http://www.sciforum.net/conf/ecsoc-15 The 15th International Electronic Conference on Synthetic Organic Chemistry The 15th International Electronic Conference on Synthetic Organic Chemistry http://www.sciforum.net/presentation/569 Mark Penick wrote: Ring C is formally antiaromatic, which is a very unusual feature to find in a drug.  Is attack on ring C a critical part of the  anticancer activity? 2011-11-18 2011-11-18T04:42:22Z http://www.sciforum.net/presentation/665 Mark Penick wrote: I think you should consider making some conformationally restricted analogs of selenocysteine that are held in the conformations (of selenocysteine) shown in the paper, to see if they work faster or better than selenocysteine itself. 2011-11-18 2011-11-18T04:30:35Z http://www.sciforum.net/presentation/699 Vitamin E, consisting of the groups of tocotrienols 5 and tocopherols 6, is the biologically most important fat-soluble antioxidant. In the context of total synthesis of these compounds,[1] the Zr-mediated carboalumination methodology[2] was applied. Alkyne 3, easily available from (E)-geranylacetone (4), delivers (all-E)-alkenyl iodide 2 for the coupling with (enantiomerically pure) aldehydes 1 to various stereochemically defined homologous trienols 5, e.g. serving as starting materials for the highly stereoselective Ir-catalyzed asymmetric hydrogenation to tocopherols 6.[3] [1] a) T. Netscher, Chimia 1996, 50, 563; T. Netscher, Vitamins and Hormones 2007, 76, 155; b) C. Rein, P. Demel, R.A. Outten, T. Netscher, B. Breit, Angew. Chem. Int. Ed. 2007, 46, 8670; c) T. Netscher, M. Scalone, R. Schmid in Asymmetric Catalysis on Industrial Scale, H.-U. Blaser, E. Schmidt (eds.), Wiley-VCH, Weinheim, Germany, 2004, p. 71. [2] a) E. Negishi, Pure Appl. Chem. 1981, 53, 2333; b) S. Huo, E. Negishi, Org. Lett. 2001, 3, 3253. [3] S. Bell, B. Wüstenberg, S. Kaiser, F. Menges, T. Netscher, A. Pfaltz, Science 2006, 311, 642. 2011-11-14 2011-11-14T00:00:00Z http://www.sciforum.net/presentation/781 In our previous works (see ECSOC-15, 2008 and also 2 our accompanied communication) we found interesting dependencies of ortho- and meta-protons chemical shift (δoH) in monoalkylbenzenes and disubstituted para-alkylaromatic compounds NMR 1H spectra upon the place and degree of branching of alkyl chain. If this branching takes place at the α-carbon atom, the shift of basic spectral parameter – δiH (δoH or δmH) - is observed and entitled as "α-effect"; the branching at β-carbon atom leads to another type shift ("β-effect"). The positive value of α- or β-effect means that δiH value increases with the increasing of amount of methyl groups in α- or β-position; contrary, negative value of such effect mean decrease δiH value. The natural question emerges: are α- and β-effects for phenyl ring carbon atoms existed too? We obtain the answer while studying NMR 1H spectra of 26 especially selected rows of disubstituted para-alkylaromatic compounds Nn of the general formula p-Y-C6H4-(CH2)r-CR1R2R3 (where r=0 or r=1). We examined as substituents "Y" 26 the most widespread groups from most electronegative (NO2) to most electropositive (NMe2). The variable fragments (R1, R2, R3) given in general formula are only hydrogen atom or methyl group. Depending upon the place of alkyl chain branching all compounds we divide into two types: the compounds of A type (r=0 in general formula), where the branching takes place at α-carbon atom and compounds of B type branched at β-carbon atom (r=1). The differential spectral parameters (ΔδiC) were used instead of basic ones (δiC). The ΔδiC parameter means a difference between the value of studied carbon chemical shift δiC,N(n) of the examined compound Nn and the same value δiC,N(0) of the standard compound, where all variable substituents R1 = R2 = R3 = Н. The δiC,N(0) and ΔδiC parameter values of all A and B type compounds are demonstrated in 5 tables. Averaged values of differential parameters were calculated, tabulated in additional 4 tables and pictured on 4 diagrams. In our communication we have a broad discussion of values and signs calculated for all types averaged differential parameters. The regular "structure-property" dependencies (α- and β-effects) which were founded only for δ0H,N(n) parameters, are also detected for 4 types of δiC,N(n) parameters of studied disubstituted para-alkylaromatic compounds. Such α- and β-effects were observed for all examined differential spectral parameters ΔδiC,N(n) in all investigated rows of disubstituted para-alkylaromatic compounds. It should be stressed that for the investigated rows of compounds 1-26 there are no facts contradicting with the predicting values and signs of both α- and β-effects. The similar regular "structure-property" dependencies are also examined for 1H NMR spectra parameters of other aromatic compounds in our accompanied communication, which we also want to sent now to ECSOC-15. 2011-11-14 2011-11-14T00:00:00Z http://www.sciforum.net/presentation/779 In our previous work (see ECSOC-12, 2008) we found some interesting dependencies of ortho-protons chemical shift (δoH) in monoalkylbenzenes NMR 1H spectra upon the place and degree of branching of alkyl chain. If the branching takes place at the α-carbon atom, the downfield shift of basic spectral parameter - δoH - (α-effect) is observed and entitled as "α-effect"; the branching at β-carbon atom leads to the shift toward upfield ("β-effect"). α-Effect has a positive value because δoH value increases with the increase of amount of methyl groups in α-position, contrary, β-effect has a negative value. The natural question emerges: which other classes of aromatic compounds (in addition to monoalkylbenzenes) the founded regularities apply to? We obtain the answer while studying NMR 1H spectra of 17 especially selected rows of monoalkylbenzenes with functional groups in alkyl substituent. Extended interpretation of the term "functional groups" allows to examine alkyl groups with multiple bonds C=C, CºC and C=O as a functionalized fragment. Depending upon the place of alkyl chain branching all compounds are divided into two types. In the compounds of A type the branching takes place at α-carbon atom and in the compounds of B type – at β-carbon atom. The variable fragments may be only hydrogen atom or methyl group. The use of differential spectral parameters (ΔδНо) instead of basic ones (δоН) is more advisable because of the great scattering of δоН,N(n) values. The differential spectral parameter is a difference between the value of ortho-protons chemical shift δоН,N(n) of the investigated compound Nn and the same value δоН,N(0) of the standard compound, when all variable substituents R1 = R2 = R3 = Н. The δНо and ΔδНо values of all A and B type compounds are demonstrated in 2 tables and 2 diagrams. The new regular "structure-property" dependencies which were determined for nonfunctionalized monoalkylbenzenes are observed for all values of basic spectral parameters δ0H, N(n) in the investigated rows of monoalkylbenzenes substituted by functional substituents in the side chain. α- and β-Effects (change of chemical shift of ortho-protons δ0H in NMR1H spectra) are explained by changes of saturation of definite spatial areas near phenyl ring by methyl groups. It should be stressed that for the investigated compounds 1-17 there are no facts contradicting with the existing of "α-effect" at the branching of alkyl chain near α-carbon atom and "β-effect" observed at the branching near β-carbon atom. The similar regular "structure-property" dependencies are reported for monosubstituted para-alkylaromatic compounds in two our accompanied communications, which we also intend to sent to ECSOC-15. 2011-11-14 2011-11-14T00:00:00Z http://www.sciforum.net/presentation/780 In our previous works (see ECSOC-15, 2008; and also our accompanied communication №1) we found some interesting dependencies of ortho-protons chemical shift (δoH) in monoalkylbenzenes NMR 1H spectra upon the place and degree of branching of alkyl chain. If this branching takes place at the α-carbon atom, the shift of basic spectral parameter – δiH (δoH or δmH) - is observed and entitled as "α-effect"; the branching at β-carbon atom leads to another type shift ("β-effect"). The positive value of α- or β-effect means that δiH value increases with the increasing of amount of methyl groups in α- or β-position; contrary, negative value of such effect mean decrease δiH value. The natural question emerges: which other classes of aromatic compounds (in addition to monoalkylbenzenes) the founded regularities apply to? Are α- and β-effects for meta-protons existed too? We obtain the answer while studying NMR 1H spectra of 21 especially selected rows of disubstituted para-alkylaromatic compounds Nn of the general formula p-Y-C6H4-(CH2)r-CR1R2R3 (where r=0 or r=1). We examined as substituents "Y" 21 the most widespread groups from most electronegative (NO2) to most electropositive (NMe2). The variable fragments (R1, R2, R3) given in general formula are only hydrogen atom or methyl group. Depending upon the place of alkyl chain branching all compounds we divide into two types: the compounds of A type (r=0 in general formula), where the branching takes place at α-carbon atom and compounds of B type branched at β-carbon atom (r=1). The differential spectral parameters (ΔδНо) were used instead of basic ones (δоН). The ΔδНо parameter means a difference between the value of studied proton chemical shift δiН,N(n) of the examined compound Nn and the same value δоН,N(0) of the standard compound, where all variable substituents R1 = R2 = R3 = Н. The δiН,N(0) and ΔδiН parameter values of all A and B type compounds are demonstrated in 3 tables. Averaged values of differential parameters were calculated, tabulated in 2 tables and pictured on 2 diagrams. In our communication we have a broad discussion of values and signs calculated for all types averaged differential parameters. The regular "structure-property" dependencies (α- and β-effects) which earlier were founded only for monoalkylbenzenes δ0H,N(n) parameters, are also detected for δ0H,N(n) and δmH,N(n) parameters of studied disubstituted para-alkylaromatic compounds. Such α- and β-effects were observed for all examined differential spectral parameters ΔδiH,N(n) in all investigated rows of disubstituted para-alkylaromatic compounds. It should be stressed that for the investigated rows of compounds 1-21 there are no facts contradicting with the predicting values and signs of both α- and β-effects. The similar regular "structure-property" dependencies are also examined for 13C NMR spectra parameters of the same disubstituted para-alkylaromatic compounds in our next communication №3, which we also want to sent now to ECSOC-15. 2011-11-14 2011-11-14T00:00:00Z http://www.sciforum.net/presentation/782 At the XIV Conference ECSOC (2010), we made the first post, which opened a new section of our research - the study of influence on each other through the space of two molecule fragments, unconnected by chemical bonds, at the time of registration of NMR spectra. In this investigation it was found that the aryl ring has the greatest influence on the spectral parameters of the studied fragment of the molecule, which is separated from the aryl groups by one or more chemical bonds. In the present communication we conduct systematic investigation of the described phenomenon researching the methyl and ethyl esters of ω-aryl fatty acids by general formula: Ar-(CR1R2)m-X-(CR3R4)n-COOAlk, where Alk = Me or Et, and X = N or O. We have studied such esters: i) of aromatic acids (m = n = 0, heteroatom X in them missing), i.e. unsubstituted and substituted benzoic (1), α-naphthoic (2); ii) of ω-arylcarbonic acid (m = 0, heteroatom X in them missing): arylacetic (3) (n = 1), β-arylpropionic (4) (n = 2) and γ-arylbutyric (5) (n = 3), as well as iii) acids, in which the alkyl moiety of the molecule acidic fragment contains heteroatom X (nitrogen or oxygen) (6). The presence or absence of the aryl fragment influence on the alkoxy group was judged on the value of the basic spectral parameters - the chemical shifts of methyl protons (δСН3Н) as well as (δСН2Н and δСН3Н) in ethyl groups. There were developed and validated specific criteria for identifying such effect. One of them is based on the introduction of a new virtual parameter - the expected value of the chemical shift of alkoxy group protons. By the sum of the results, obtained using all the necessary criteria, we make judgments about the probability of the presence or absence of the studied effect. There were suggested the presence of studied effects in ethers 3-6, and its absence in the esters 1 and 2, with the exception of esters of substituted benzoic acids (1), in which the substituent in the ortho-position is aryl group. Based on the virtual differential ∆δСН2Н and ∆δСН3Н ​​ parameters values (which is equal to the difference between "experimentally obtained" and "expected" values ​​of the basic spectral parameters δСН2Н or δСН2Н), as well as other criteria, we make judgments about the magnitude of the studied effect in esters 3-6 as well as its dependence on the values ​​of m, n, and X. A comparison of aryl group "influence magnitude" aryl group on the protons of methyl and methylene fragments of ethoxyl group. We make the overall conclusion about high probability of the studied effect existence in esters 3-6 and, especially, in compounds 3 and 4. 2011-11-14 2011-11-14T00:00:00Z http://www.sciforum.net/presentation/771 Selçuk Gümüş wrote: Thank you Dr. Azizoglu... 2011-11-11 2011-11-11T23:02:40Z http://www.sciforum.net/presentation/771 Akin Azizoglu wrote: Congratulation. A novel work for aromaticity of heterocyclic derivatives. 2011-11-09 2011-11-09T16:06:35Z http://www.sciforum.net/presentation/789 Thanh Dao Tran wrote: Thanks Dr. Santosh Kumar Gurung for your attention as well as good commendation. We are conducting our project with other series of chalcones in which B ring possess chlorine atom as well as A ring are pyridin-3-yl, pyridin-4-yl moieties. We will submit them in the next time. Best regards. 2011-11-07 2011-11-07T15:46:03Z http://www.sciforum.net/presentation/789 Santosh Kumar Gurung wrote: First of all congratulation. Good to attend this virtual presentation. A novel work for new type of heterocyclic chalcone derivatives. I wonder the new derivatives with substituted halogens at B-ring as well as synthesis of pyridin-3-yl, pyridin-4-yl derivatives. All the best 2011-11-05 2011-11-05T13:35:41Z http://www.sciforum.net/presentation/693 Francisca Cabrera-Escribano wrote: You can see the complete file if you click on "download PDF File" at the botton of the page. However, if you have any problem about, I could send you the file by e-mail. 2011-11-03 2011-11-03T13:16:59Z http://www.sciforum.net/presentation/693 Mark Penick wrote: Please re-upload your paper, it seems page 3 is corrupt and won't load. 2011-11-02 2011-11-02T20:25:10Z http://www.sciforum.net/presentation/768 We report herein that acylals can be prepared very fast and in excellent yields by the direct condensation of aldehydes with acetic anhydride under solvent-free condition by employing of a mesoporous derivatized Mobile Crystalline Material, MCM-41-SO3H as heterogeneous catalyst at room temperature. 2011-11-02 2011-11-02T00:00:00Z http://www.sciforum.net/presentation/792 Composite of magnetic and conductive Hollow polyaniline/CnFe2O4 nanosphere with novel core-shell structure were successfully prepared by in-situ polymerization in the presence of ammonium persulfate (APS) as the oxidant and dodecyl benzene sulfonic acid (DBSA) as the surfactant and dopant. The synthesized hollow microsphere composites were characterized by FT-IR and UV/Vis spectrophotometry. X-ray photoelectron spectroscopy was used to determine the degree of coating with a conducting polymer. Its morphology was characterized by scanning electron Microscopy (SEM). The changes of the magnetic properties before and after polyaniline coating were investigated by using vibrating sample magnetometer (VSM). 2011-11-02 2011-11-02T00:00:00Z http://www.sciforum.net/presentation/636 N-Tosyl-2-nitropirrole and N-Tosyl-3-nitropirrole reacts with poorly and activated dienes using protic ionic liquids as reaction media. They exhibit a dienophile character producing the corresponding indoles through a Diels-Alder process. In all cases the presence of protic ionic liquids as reaction media improve the yields respect to use of molecular solvent, while the temperature and the reaction time decrease. 2011-11-02 2011-11-02T00:00:00Z http://www.sciforum.net/presentation/791 In this paper we have investigated photocatalytic activity of the N, S-codoped TiO2 nanoparticles for degradation of 4-NP in aqueous. In this method nitrogen and sulfur doping by using a single source, ammonium sulfate as the modification agent of titanium tetrachloride as precursor and the N, S-codoped TiO2 nanoparticles prepared by the sol-gel method. This catalyst was characterized by XRD, SEM, UV- visible and FT-IR. 2011-11-02 2011-11-02T00:00:00Z http://www.sciforum.net/presentation/793 In this work, a novel method of microwave assisted chemical precipitation procedure was used to synthesize AgInS2 nanoparticles. Ag, In and S precursors with a stoichiometric ratio of 1:1:2 were dissolved in ethylene glycol as solvent and compolexing agent. The resultant precipitation was placed under microwave irradiation for 5 min to obtain product. X-ray diffraction pattern (XRD) and scanning electron microscopy (SEM) were employed to characterize the final product. 2011-11-01 2011-11-01T00:00:00Z http://www.sciforum.net/presentation/764 In this research, a new series of substituted 4H- pyrans and 4H-chromenes derivatives has been synthesized at ambient temperature in the presence of catalytic amount of sodium carbonate (20 mol %) via one-pot three-component cyclocondensation reactions of malononitrile, dialkylacetylenedicarboxylates and 1,3-diketones in ethanol under ultrasound irradiation. The synergistic effect of MCRs and ultrasound has been successfully demonstrated to offer an easy way for the synthesis of these compounds in excellent yields. 2011-11-01 2011-11-01T00:00:00Z http://www.sciforum.net/presentation/789 In a wide search program toward new antimicrobial agents, a seri of heterocyclic chalcones have been synthesized by condensing benzaldehyde derivatives with heteroarylmethylcetone in potassium hydroxide methanol according to the Claisen-Schmidt condensation at room temperature. The synthetic chalcones have been determined by IR spectroscopy and 1H-NMR spectroscopy. The antimicro-bacterial activity of the novel products was evaluated against bacteria such as Staphylococcus aureus, Pseudomonas aeruginosae, E. coli and fungi such as Candida albicans, dermatophytes. The result shows that pyridine moiety may show antibacterial effect stronger than that of thiophene or furan. Heterocyclic chalcones with hydroxyl group on B ring at position 2 or 3 are considered as lead compounds for generation of new potential antimicrobial drugs in future. 2011-10-31 2011-10-31T00:00:00Z http://www.sciforum.net/presentation/584 Peculiarities of 2,1-benzisoxazol-3(1H)-one synthesis by means of the photochemical cycle forming reaction of 2-azidobezoic acid in ethanol. Based upon HPLC kinetical data we have observed the 2,1-benzisoxazol-3(1H)-one yield decrease in the course of decreasing of the starting azide concentration. It was stated that the 2,1-benzisoxazol-3(1H)-one formation effectiveness depended on the actinic light wavelength. Changing the light wavelength from 365 to 253.7 nm we observed an increase of the cycle formation yield. The decrease of the 2,1-benzisoxazol-3(1H)-one yield in the course of irradiating at 365 nm was explained by the secondary photolysis. 2011-10-31 2011-10-31T00:00:00Z http://www.sciforum.net/presentation/770 A simple, convenient, and practical method for the synthesis of α-amino nitriles through a one-pot, three-component Strecker reaction of diverse carbonyl compounds and amines with trimethylsilyl cyanide (TMSCN) under mild conditions in EtOH 96 % has been developed. Reactions proceed efficiently in the presence of a catalytic amounts of new and recoverable ionic liquid of N-butyl-N-methyl imidazolium Phthalimide-N-Oxyl {[Bmim] PINO} at room temperature. 2011-10-31 2011-10-31T00:00:00Z http://www.sciforum.net/presentation/599 This communication deals with the synthesis and evaluation of some pyrazinamide (PZA) analogues/prodrugs. A series of sixteen pyrazinamide analogues with the –CO-NH-CH2- or -NH-CH2- linkers connecting the pyrazine and benzene rings was prepared by using the microwave assisted coupling reaction of substituted methyl-pyrazinecarboxylate with ring-substituted benzylamines and characterized. The results of in vitro antimycobacterial screening indicated some interesting antimycobacterial activity in the series of N-benzylpyrazine-2-carboxamides. From the second series, 3-(3,4-dichlorobenzylamino)pyrazine-2-carboxamide was the most active in the inhibition of photosynthetic electron transport (PET) in spinach (Spinacia oleracea L.) chloroplasts (IC50 = 2.2 μmol mL-1). 2011-10-31 2011-10-31T00:00:00Z http://www.sciforum.net/presentation/579 Cyclodextrins polymers are known as an interesting low molecular carriers in pharmacy, food technology, medicine etc. There are different routes to design such kind of macromolecules however most of them base on synthetic compound. In the presented work a series of cyclodextrin polyesters with malic acid were obtained using dry method. Sodium hydrogen phosphate was used as a catalyst. As a result two different fractions were obtained i.e. water soluble and insoluble ones. Both of them were characterized by means of carboxylic acid (HPLC) and carbohydrates profile (anthron method) . Several malic acid derivatives were detected especially fumaric and malonic acids. In obtained sample the complexation ability was checked using standard methyl orange method. The insoluble fraction was hydrolyzed using sodium carbonate solution and the carboxylic acids and cyclodextrin presence were investigated as well. According to obtained results we can state the novel cyclodextrin macromolecules were design using simple and easy protocol. The obtained product is fully biodegradable and completely nontoxic what guides to many possible application in both food and non-food application. 2011-10-31 2011-10-31T00:00:00Z http://www.sciforum.net/presentation/572 The object of the present study is the isodesmic reaction of cellobiose (the repeating unit in cellulose) with different kinds of silanes, R-SiH3, to form silylated cellobiose (Cello-SiH3) and the corresponding alcohols (R-OH). The size and the chemical reactivity of the substituent R is varied as well as the position where O-silylation at the cellobiose takes place. In contrast to experimental observations where the O6 position is favored for silylation, for the computed reactions, energy differences are smaller than 3 kcal/mol for the different positions at the B3LYP/6-311G* as well as at the B3LYP/6-311+G* level of theory. Depending on the silane, reaction energies in a range from -17 kcal/mol (R=NHSiH3) and +18 kcal/mol (R=F) have been calculated. In addition, semi-empirical calculations on the PM3 level of theory have been performed. These results are set into contrast with the results derived from DFT calculations to assess whether semi-empirical methods may be useful for the description of larger systems containing silylated cellobiose units. Acknowledgements: The research leading to these results has received funding from the European Community's Seventh Framework Programme [FP7/2007–2013] under grant agreement no. 214015 (S.S. and H.M.A.E.) and no. 214653. 2011-10-31 2011-10-31T00:00:00Z http://www.sciforum.net/presentation/756 The fluoroscent dyes are used as probes for the detection of heavy metal ions, aminoacids and other biomolecules in recent years. Some of these dyes, including Nile Blue deivatives, which belong to the benzophenoxazine family, fluoresce at near the far visible-near infrared region with minimum interference from absrption scattering and reduced risk of photodecomposition.1 As previously reported by our group,2,3 benzo[a]phenoxazinium dyes are involved in an acid-base equilibra where the 5-amino position is the main site of deprotection.4 The quantum yield of the basic form is almost ten times lower than the cationic acid form. This has an impact in the overall fluorosence quantum yield. In continuation of our research intrests,2-4 the present work describes the study of fluoresence quantum yileds of pure cationic forms by shifting the acid-base equilibria with the addition of a strong acid. The photophysical behaviour of these novel compounds in AOT/cyclohenxane/water w/o microemulsions as a function of water content will also be discussed. Acknowledgements: Thanks are due to Fundacao para a Ciencia e Tecnologia (Portugal) for its financial support of a BPD to B. R. Raju (SFRH/BPD/62881/2009), Centro de Quimica and Centro de Fisica (Universidade do Minho). The NMR Spectro meter Bruker Avance III 400 is part of the National NMR Network, and was purchased in the framework of the National Program for Scientific Re-equipment, contract REDE/1517/RMN/2005 with funds from POCI 2010 (FEDER) and FCT. Refrences: 1. Goncalves, M. S. T. Chem. Rev. 2009, 109, 190. 2. Alves, C. M. A.; Naik, S.; Coutinho, P. J. G. Goncalves, M. S. T. Tetrahedron 2009, 65, 10441. 3. Alves, C. M. A.; Naik, S.; Coutinho, P. J. G. Goncalves, M. S. T. Tetrahedron Lett. 2011, 52, 112. 4. Naik, S.; Alves, C. M. A.; Coutinho, P. J. G. Goncalves, M. S. T. Euro. J. Org. Chem. 2011, 13, 2491. 2011-10-31 2011-10-31T00:00:00Z http://www.sciforum.net/presentation/727 A library of 2-amino-9-aryl-3-cyano-4-methyl-7-oxo-6,7,8,9-tetrahydropyrido[2',3':4,5]thieno[2,3-b]pyridines which recently have been reported as selective progesterone receptor agonists was synthesized by ternary condensation of N-methylmorpholinium 4-aryl-3-cyano-6-oxo-1,4,5,6-tetrahydropyridine-2-thiolates with malononitrile and acetone, and alternatively by reaction of bis(4-aryl-3-cyano-6-oxo-1,4,5,6-tetrahydropyridine-2-yl)disulfides with acetone and malononitrile in basic media. The mechanism, scope and limitations of the reactions are discussed. 2011-10-31 2011-10-31T00:00:00Z http://www.sciforum.net/presentation/701 Ab-initio levels of theory using 6-31+G(d,p) basis set have been carried out to investigate the Isomeric structures, energies and properties of mononsilacyclopropylidenoids, C2H4SiMX (where M= Na or Li, and X= F, Cl or Br). The theoretical calculations depict that each of them has three stationary structures: silacyclopropylidenoid (S), tetrahedral (T), and inverted (I). All of the silacyclopropylidenoid (S) forms are energetically more stable than others except for S-LiF, whereas all of the tetrahedral (T) forms are the most unstable ones except for T-NaF. Energy differences between S, T, and I forms range from 0.60 to 8.70 kcal/mol. Moreover, natural bond orbitals (NBO), and frontier molecular orbitals (FMO) were achieved in this computational study. 2011-10-31 2011-10-31T00:00:00Z http://www.sciforum.net/presentation/607 Polyfluoroarylmetallic compounds are the important group of polyfluoroarenes. Among the chemical transformations of polyfluoroarylmetallic compounds, it is of interest to study the properties of polyfluoroaromatic zinc compounds and their role as reactive intermediates. Polyfluoroaromatic zinc compounds were prepared from chloropentafluorobenzene and perfluoroarenes [1,2]. Recently, these organozinc compounds were converted to hydro-, bromoperfluoroarenes, perfluorobiaryls, allylpolyfluoroarenes, N,N-dimethyl-bis(polyfluoroaryl)methanamines, polyfluoroaromatic ketones [1-4]. Search for the ways of synthesis of polyfluoroaromatic aldehydes is another important aspect of chemistry of polyfluoroarylzinc compounds. We have found that interaction of these organozinc compounds with Vilsmeier-Haack reagent formed from oxalyl chloride and DMF, and subsequent treatment of the reaction mixtures with water led to the corresponding polyfluoroaromatic aldehydes. When methanol was used instead of water, polyfluorinated acetales were obtained. From 1,4-dibromo-2,3,5,6-tetrafluorobenzene and zinc in the presence of tin (II) chloride in DMF, dizinc compound was obtained that was then converted to 2,3,5,6-tetrafluoroterephthalaldehyde by reaction with Vilsmeier-Haack reagent. The mechanisms of transformations are discussed. References [1] A.O. Miller, V.I. Krasnov, D. Peters, V.E. Platonov and R. Miethchen, Tetrahedron Lett., 2000, 41, 3817-3819. [2] A.S. Vinogradov, V.I. Krasnov and V.E. Platonov, Russ. J. Org. Chem., 2008, 44, 95-102. [3] A.S. Vinogradov, V.I. Krasnov and V.E. Platonov, Coll. Czech. Chem. Commun. 2008, 73, 1623–1630. [4] A.S. Vinogradov, V.I. Krasnov and V.E. Platonov, Russ. J. Org. Chem., 2010, 46, 344-351. 2011-10-31 2011-10-31T00:00:00Z http://www.sciforum.net/presentation/617 Phenolic compounds are bioactive substances widely distributed in the vegetable kingdom. They act as natural antioxidants, and their presence contributes to the color, flavor and aroma of food. This group of micronutrients is composed of one or more aromatic benzene rings with one or more hydroxyl groups and their redox properties are related with their chemical structure characteristics. The knowledge of their redox potentials may help the food industry, because when phenolic compounds are oxidized they could affect the quality of the wines, beers, grape juices, etc. Coumarins are a large family of compounds, of natural and synthetic origin, that show important biological activities. Therefore, they occupy an important place in the study of natural products and synthetic organic chemistry. Recent studies pay special attention to their antioxidative, anticarcinogenic and enzymatic inhibition properties. Their preparation, and the versatility of the synthetic methodology, allowed us obtaining a wide family of compounds with substituent in different positions in the molecule. The election of these derivatives has considered the later pharmacological evaluation. The investigation of the properties of these compounds, the study of the structural pattern and the elucidation of their biological role is of great interest for further development of coumarin-like antioxidant drugs. The electrochemical behaviour of a group of differently substituted hydroxycoumarins was investigated using cyclic, differential pulse and square wave voltammetry, in aqueous media at a glassy carbon electrode over the whole pH range. The antioxidant reactivity and capacity were also evaluated through a competition assay with hydroxyl radical (OH•) and DMPO like ORAC-FL methodology. Number and positions of the hydroxyl groups were important factors in the antioxidant activities against peroxyl radical of both types of coumarins derivatives. 2011-10-31 2011-10-31T00:00:00Z http://www.sciforum.net/presentation/613 Oxalyl chloride (1) has been known to be involved as C1 synthon for ketone synthesis,1 as an alternative route for carbonylation with CO gas. Given the importance of ketones in pharmaceutical and industrial applications,there is a permanent interest in finding new ways for their synthesis. Based on the exceptional leaving group ability of the trialkylstannyl group in EAS, we have recently proposed efficient catalyst-free and regioselective synthesis of unsymmetrical ketones using different acyl chlorides.2 Driven by these results we initiated studies on the reaction of arylstannanes with 1. Now, we describe a novel regioselective synthesis of symmetrical diaryl ketones using 1 as C1 carbonyl synthon, under catalyst-free conditions. These results are significant from the point of view of its simplicity, the wide range of synthetically3 or commercially available arylstannanes and the associated convenience in the utilization of 1 as carbonyl synthon, instead of specific acyl chlorides. All the reactions studied went, exclusively, through an ipso-substitution independently whether the directing influences of the aryl substituents and the trialkylstannyl group are either matched or mismatched. We suggest a mechanism by which 1 acts as C1 synthon on these reactions. In addition, a special work up is proposed in order to recover the trialkyltin chlorides generated. 1 Rao, M. L. N.; Venkatesh, V.; Dasgupta, P. Tetrahedron Lett. 2010, 51, 4975-4980. 2Lo Fiego, M. J.; Silbestri, G. F.; Lockhart, M. T.; Chopa, A. B. J. Org. Chem. 2011, 76, 1707-1714. 3 Silbestri, G. F.; Lo Fiego, M. J.; Lockhart, M. T.; Chopa, A. B. J. Organometal. Chem. 2010, 695, 2578-2585. 2011-10-31 2011-10-31T00:00:00Z http://www.sciforum.net/presentation/601 Surfactants are organic compounds which contain hydrophobic groups acting as tail and hydrophilic groups acting as head, thus they are solved hardly in water and organic solvents.Surfactants are able to change surface energy within levels considerably. Property of surfactant comes from its double molecular structure. It means that it contains two hydrophilic and hydrophobic groups at the same time. A novel type of surfactants known as bolaform is studied and synthesized in this study. Bolaforms have two polar head groups connected via a poly methylen chain. They are categorized into anionic, cationic and non ionic depending on the head group's charge. Micelle extraction of metallic ions, using as molecules sensitive to light and usage in synthesis of mesoporous silica structure for different applications such as in catalysts are among bolaforms' applications. Structural formula of synthesized kinds with the same spacer and different heads is as follows. Bolaform A with structural formula of Br-(CH3)3N+(CH2)12 N+(CH3)Br – with side branches of methyl in head group and bolaform B with structural formula of Br-(CH3 CH2)3N+(CH2)12 N+(CH3 CH2)3Br – . IR and NMR identification techniques approves obtained product. Using surface tension measurement device it can be observed that synthesized bolaforms have suitable CMC (relatively low); in other words, bolaform's surfactants with long spacer have surface activity property. 2011-10-31 2011-10-31T00:00:00Z http://www.sciforum.net/presentation/769 Nano-ordered MCM-41 anchored sulfonic acid (MCM-41-SO3H) was found to be an efficient catalyst for condensation of indoles with various carbonyl compounds to afford the corresponding bis(indolyl)methanes in high yields under solvent-free conditions using ball milling at room temperature. 2011-10-31 2011-10-31T00:00:00Z http://www.sciforum.net/presentation/739 Bitopic pyrazole-containing ligands attract interest because of their potential use as building blocks for crystal engineering and for synthesis of heterobimetallic complexes for catalysis. Several new bitopic pyrazole-containing ligands were prepared from the corresponding pyrazoles and tetrahalogen- or tetratosyloxy derivatives of o-xylene and neopentane in a superbasic medium (KOH-DMSO). The reaction of unsubstituted pyrazole with 1,3-dibromo-2,2-dibromomethylpropane yields a new tetrapyrazole ligand with a neopentane backbone, while no reaction occurs in case of 3,5-dimethylpyrazole. The product represents a bitopic ligand comprising two 1,3-bis(pyrazol-1-yl)propane units directly linked together. The use of tetratosyloxy- instead of tetrabromo-derivative gives previously unknown 1,1-bis(3,5-dimethylpyrazol-1-ylmethyl)oxetane, while the unsubstituted pyrazole in the same conditions yields a mixture tetrapyrazolyl-neopentane and dipyrazolyloxetane derivatives. A new bitopic ligand with aromatic o-xylene linker inaccessible by other routes was prepared from o-bis(dibromomethyl)benzene and pyrazole in a superbasic KOH-DMSO medium. In case of 3(5)-methylpyrazole and 3,5-dimethylpyrazole no products could be isolated, apparently due to steric hindrance. 2011-10-31 2011-10-31T00:00:00Z http://www.sciforum.net/presentation/606 Polyfluoroarenesulfonyl halides can be successfully used for the introduction of polyfluoroarenesulfonyl moiety in organic compounds. Recently we realized a simple and efficient method for preparation of polyfluoroarenesulfonyl bromides by the action of electrophilic brominating agents on polyfluoroarenethiols. We have shown that the nature of halogen atom in SO2Hal group influence the chemical properties of polyfluoroarenesulfonyl halides. Thus, the reactions of polyfluoroarenesulfonyl bromides with alkenes such as hexene-1 or allyl chloride provided the corresponding adducts in high yields, while the conversion of polyfluoroarenesulfonyl chlorides at the same conditions was poor and C6F5SO2F was unreactive. The formation of adducts apparently occurs with participation of polyfluoroarenesulfonyl radicals. At the same time the reaction of polyfluoroarenesulfonyl bromides with allyl bromide resulted in allyl polyfluoroaryl sulfones. This fact is explained by the addition of polyfluoroarenesulfonyl radical to alkene double bond and subsequent elimination of bromine. In reactions of allyl polyfluoroaryl sulfones with polyfluoroarenesulfonyl bromides the replacement of ArFSO2 group in sulfone by another one takes place. According to these data the reversibility of allyl polyfluoroaryl sulfone formation can be suggested. Surprisingly the reactions of polyfluoroarenesulfonyl chlorides or bromides with polyfluoroarenethiols gave mixtures of polyfluorinated diaryl disulfides, whereas replacement of fluorine atom at the 4-position of aromatic ring of C6F5SO2F occured. It turned out that reactions of polyfluoroarenesulfonyl chlorides or bromides with some n‑nucleophiles probably proceeded with electron transfer. For example, such process could take place in reactions of polyfluoroarenesulfonyl chlorides or bromides with alkali metal halides. 2011-10-31 2011-10-31T00:00:00Z http://www.sciforum.net/presentation/615 Some new nitrogen bridge-head pyrido[1,2-b][1,2,4]triazepines incorporating 6-methylchromone moiety have been synthesized from the reaction of 1,6-diamino-4-(6-methyl-4-oxo-4H-chromen-3-yl)-2-oxo-1,2-dihydropyridine-3,5-dicarbonitrile (4) with some 1,3-bifunctional electrophiles including 2-cyano-3,3-bis(methylthio)acrylonitrile, 2-cyano-3,3-bis(methylthio)prop-2-enamide, 5-chloro-3-methyl-1-phenylpyrazol-4-carboxaldehyde, 2-chloro-3-formylquinoline, p-methoxybenzylidenemalononitrile, ethyl 2-cyano-3-(4-methoxyphenyl)prop-2-enoate and chromone-3-carbonitrile. Structure of the newly synthesized compounds have been establised on the basis of elemental analysis and spectral data. All compounds were screened in vitro for their antimicrobial activity. 2011-10-31 2011-10-31T00:00:00Z http://www.sciforum.net/presentation/642 Several research studies involving fused heteroaromatic dyes based on the oxazine moiety have been focused on their absorption and fluorescence spectroscopic properties.1 These long-wavelength fluorophores find applications as biological probes, namely in covalent labeling of amino acids, proteins, peptides and DNA.2 Also, more frequently they have been used in non-covalent labeling, such as staining nucleic acids in a variety of context, monitoring protein conformation alterations or for therapeutic purposes.3 Although the interest of photophysical properties, several compounds possessing the phenoxazine nucleus have been stressed due to their antiproliferative properties with potential applications both as antitumour and as antimicrobial agents. Considering our promising previous results in this field,4 and having in mind future evaluation of biological activity, we decided to synthesise new benzo[a]phenoxazinium salts having chlorinated terminals at their substituents in 2- and 9- positions. Furthermore, these compounds can also be used as covalent and non-covalent probes, and consequently the photophysical properties were also studied in ethanol and water in simulated physiological conditions. Acknowledgements: Thanks are due to the Foundation for Science and Technology (Portugal) for its financial support of Centre of Chemistry. The NMR spectrometer Bruker Avance III 400 is part of the National NMR Network (RNRMN) and was purchased in the framework of the National Program for Scientific Re-equipment, contract REDE/1517/RMN/2005 with funds from POCI 2010 (FEDER) and FCT. References 1. Jose, J.; Burgess, K. Tetrahedron 2006, 62, 11021-11037. 2. Salomi, B. S. B.; Mitra, C. K.; Gorton, L. Synth. Met. 2005, 155, 426-429. 3. Nakanishi, J.; Nakajima, T.; Sato, M.; Ozawa, T.; Tohda, K.; Umezawa, Y. Anal. Chem. 2001, 73, 2920-2928. 4. Frade, V. H. J.; Sousa, M. J.; Moura, J. C. V. P.; Gonçalves, M. S. T. Bioorg. Med. Chem. 2008, 16, 3274-3282. 2011-10-31 2011-10-31T00:00:00Z http://www.sciforum.net/presentation/640 Two new symmetrical disazo direct dyes containing 4,4'-diaminostilbene-2,2'disulphonic acid as middle component and 3-bromosalicylanilide and 4-bromosalicylanilide as coupling components were synthesized. The dyes were characterised by TLC, VIS, FT/IR, 13C-NMR spectroscopy, and HPLC technique. The colour, spectrophotometric study of the two disazo stilbene dyes with symmetrical structure was performed using the CIE 1976 (CIELAB) uniform colur space parameters, under the CIE (Commission Internationale d'Eclairage) recommended illuminants: D65 (natural day light), A (tungsten light), F2 (fluorescent light) and the standard 10° observer respectively. The colour differences (ΔEab*) and (ΔECMC) were calculated against one standard, revealing a high colouring power for the two new studied dyes. 2011-10-31 2011-10-31T00:00:00Z http://www.sciforum.net/presentation/644 In this work we studied changes in poly(vinyl alcohol) (PVA) conformations with respect to the polymer concentrations, using Langevin dynamics at 300 ± 10 K. Constructed polymer chain consisted of 90 units and the friction coefficient of the solvent (water) was set to 55 ps-1. We also turned to quantum mechanical calculations, using B3LYP/6-31+G* level of theory in order to investigate the association via hydrogen bonds (HB) between two OH-groups of PVA and between OH-group and water. It was demonstrated that in dilute solutions PVA macromolecules tend to shrink and form more dense coils by comparison with polymers in more concentrated solutions, where two or more chains overlap, entangle and associate via intermolecular hydrogen bonding. We also established that HB between OH-groups and water molecules are less stable than those between two not adjacent OH-groups of one or various chains. The obtained data allow us to consider that in the case of low PVA concentrations, the distances between parts of one chain tend to decrease that leads to the polymer conformation favorable for the intramolecular cross-linking when the acetalization reaction of PVA takes place. As far as the cross-linking occurs within the coil, the resulting product should loss it flexibility. We assumed that the mass-transfer in this system should be slower than the subsequent chemical reaction, so the acetalization of partially modified PVA should proceed with essential retardation. 2011-10-31 2011-10-31T00:00:00Z http://www.sciforum.net/presentation/679 Our group has been involved in searching new synthetic routes to organostannanes by the SRN1 mechanism.1 Based on our experience we consider of interest to study the scope of SRN1 in the polystannylation of an aromatic ring. Now we inform the experimental results obtained in the reaction of trimethylstannylsodium (1) with aryl phosphates supporting three nucleofugal groups, in liquid ammonia as solvent, and a DFT study which support the notable differences observed between isomeric substrates. In order to synthesize 1,2,4-tris(trimethylstannyl)benzene (2) we use as starting substrates 1,3-bis(diethoxyphosphoryloxy)-4-chlorobenzene (3) and 1,4-bis(diethoxyphosphoryloxy)-3-chlorobenzene (4). Under photostimulation 3 and 4 led to entirely different products distributions. Meanwhile 3 afforded 2 together with 1,3- and 1,4-bis(trimethylstannyl)benzene in a 63:23:10 ratio, 4 yielded a mixture of 2 and 1,4- bis(trimethylstannyl)benzene in a 32:68 ratio. Starting substrates were almost recovered in dark reactions supporting an SRN1 mechanism. These results were unexpected since the substrates would have similar electron affinities. We have previously demonstrated that differences in spin density on radical anions affect products distributions,2 so, we started a systematic theoretical study over 3 and 4 with the B3LYP functional, the LACVP pseudopotential (Sn) and the 6-31+G* (C, H, O, P) with GAUSSIAN03. We observed meaningful differences in SOMOs MO, spin density distribution and activation energies of the corresponding radical anions intermediate, which support the experimental outcome and allow us to interpret the distribution of stannylated end-products in terms of the structural features of the starting isomers. 1 Silbestri, G. F.; Lo Fiego, M. J.; Lockhart, M. T.; Chopa, A. B. J. Organometal. Chem. 2010, 695, 2578-95 and references therein. 2 Dorn, V. B.; Badajoz, M. A.; Lockhart, M. T.; Chopa, A. B.; Pierini, A. B. J. Organometal. Chem. 2008, 693, 2458-62. 2011-10-31 2011-10-31T00:00:00Z http://www.sciforum.net/presentation/681 Derivatives of quinoline and its isosters are remarkable compounds with many different kinds of biological effects. A number of quinoline related compounds expressed antifungal, antibacterial, antiviral, antineoplastic, and other activities. In order to perform the classical synthesis of amides activation of quinoline-2-carboxylic acid is usually required. When activation is carried out under standard conditions with thionyl chloride, formation of undesired chloro compound where chlorine is attached in position 4 of quinoline ring is observed. In this study we have developed a method for preparation of substituted anilides in one step, based on the direct reaction of an acid or ester with substituted anilines using microwave irradiation. In recent developments, the use of microwave irradiation to simplify and improve classic organic reactions has become a very popular method, because it often leads to higher yields, cleaner reactions and shorter reaction times. In connections with solvent-free conditions, microwave-assisted methods result in very efficient and environmentally friendly technology. The method was tested on compounds: 2-quinaldic acid and its methyl and phenyl ester, 2-naphthoic acid and its ethyl ester. All those compounds reacted with 4-bromaniline as a model aniline. The synthesis was carried out under solvent-free conditions or in solvents: DMF and chlorobenzene. Despite the fact, that formation of anilides under microwave irradiation is hampered by competitive decarboxylation of quinaldic acid to quinoline, this technique showed certain advantages like shorter reaction time, no use of aggressive chemicals and simpler work-up. From the series of experiments is evident, that the use of phenyl ester is the most effective for microwave accelerated synthesis of anilides. A series of substituted anilides of quinaldic acid were prepared by developed method. 2011-10-31 2011-10-31T00:00:00Z http://www.sciforum.net/presentation/626 2,2'-Dicarbazole-1,1'-diphenyl (2,2'-CBP) is a prospective host material for phosphorescent light emmiting diodes (PHOLED)s. The synthesis of 2,2'-CBP is limited by the availability of starting materials. We wish to report an efficient protocol for the synthesis of 2,2'-CBP with overal yield about 90% starting from o-nitrobenzoic acid. Thus, Pd catalized homocoupling of o-nitrobenzoic acid affords 2,2'-dinitro-1,1'-diphenyl (2,2'-DNDP) in 95% yield. Pd catalized reduction of 2,2'-DNDP and the following double arylation of 2,2'-diaminodiphenyl with 2,2'-dibromo-1,1'-diphenyl (which can be obtained from 2,2'-diamino-1,1'-diphenyl in 70-76% yield) affords the final product in 95% yield with overal yield after 3 steps of 90 %. 2011-10-31 2011-10-31T00:00:00Z http://www.sciforum.net/presentation/748 Abstract:Surfactants are a class of chemical compounds with unique properties, structure of which is consisted of hydrophobic and hydrophilic parts. This double structure gives rise to their unique behaviors in various conditions. Bolaforms are organic molecules compounds of two charged groups which are connected via a linear poly methylen chain.Bolaforms' surfactants don't work as well as Conventional surfactant (having a head group and one alkyl chain) in reducing surface tension. Bolaforms are absorbed in water – air interface, however, their effectiveness in terms of reducing water surface tension is not considerable compared to common surfactants. In this study, synthesis of two kinds of bolaforms which the same spacer length and different heads is investigated. The structural formula for synthesized kinds is as follows: bolaform A with structural formula Br-(CH3)3N+(CH2)3 N+(CH3)­3 Br – ­with methyl side branches in head group and bolaform B with structural formula of Br-(CH3 CH2)3N+(CH2)3 N+(CH3 CH2)3Br –. IR and NMR identification techniques approves obtained product. Using surface tension measurement device it can be observed that synthesized bolaforms have high CMC; in other words, bolaform's surfactants with short spacer play electrolytic role. 2011-10-31 2011-10-31T00:00:00Z http://www.sciforum.net/presentation/639 Dyes ions have a tendency to self-associate in aqueous solutions. Since almost all textile dyes are applied from aqueous systems, it is important to understand the association of dyes in water, and to determine the number of chemical species presented in the system. The main factors influencing aggregation are dye concentration, electrolyte concentration, and temperature. In the present work, the influence of the coupling component structure on the dye aggregation is presented. The molecular aggregation has been studied spectrophotometrically in aqueous solutions as a function of dye concentration (10-6 ¸ 10-3 mol/L). As the concentration increases, different changes were observed in the dyes UV-vis spectra indicating that the molecules are beginning to aggregate. The shapes of the obtained spectra were totally different as the coupling component structure was changed in the dye molecule.From the matriceal analysis, the number of chemical species presented in the system (in domain of concentrations studied) was determined. The mathematical calculations confirm the experimental data regarding the aggregation of the investigated dyes. 2011-10-31 2011-10-31T00:00:00Z http://www.sciforum.net/presentation/634 We have explored the reaction of substituted alkenylaluminums that were prepared by various methods with sulfonyl halides, which we believed to be effective sources of electrophilic halogen. Alkenylaluminums obtained in Zr-catalyzed methylalumination of terminal alkynes react with sulfonyl chlorides and bromides to give corresponding alkenyl halides in high yield. Cycloalumination of 1-decyne and phenylacetylene affords aluminacyclopent-2-enes, which react with 1 equivalent of sulfonyl chlorides and bromides to give after deuterolysis alkenyl halides in high yield. The halogenation proceeds regioselectively only at the sp2-hybridized carbon atom and with the retention of the configuration of the double bond. To our surprise, b-substituted vinylaluminums that were obtained by hydroalumination of terminal alkynes (1-octyne, phenylacetylene) by DIBAL-H do not react with sulfonyl halides (MsCl, TsCl, MsBr). Thus, the sulfonyl chlorides and bromides are more convenient halogenation agents for b,b- and a,b,b-substituted vinylaluminums that were prepared by Zr-catalyzed methylalumination and cycloalumination compared to NCS and NBS, which is manifested in the facts that: a) the reaction proceeds at room temperature; b) the reaction does not require the use of ether solvent (moreover, the latter inhibits the halogenation), c) higher regioselectivity for the bromination of aluminacyclopent-2-enes is observed. 2011-10-31 2011-10-31T00:00:00Z http://www.sciforum.net/presentation/740 Since the optically active quinuclidin-3-ol is an important intermediate in the preparation of physiologically or pharmacologically active compounds, new biocatalytic method for the efficient production of chiral quinuclidin-3-ols was examined. Butyrylcholinesterase (BChE; EC 3.1.1.8) was chosen as a biocatalyst in a preparative kinetic resolution of enantiomers. [1-3] In this study a series of racemic, (R)- and (S)- esters of quinuclidin-3-ol and acetic, benzoic, phthalic and succinic acids were synthesized as well as their racemic and chiral, quaternary N-benzyl, meta and para N-bromobenzyl and meta and para N-methylbenzyl derivatives. After the resolution, all N-benzyl protected groups were successfully removed by catalytic transfer hydrogenation with ammonium formate (10% Pd-C). The stereoselectivity of hydrolysis with horse serum BChE was investigated. The rates of hydrolyses were monitored at 37 oC in 0.1 M phosphate buffer pH 7.4 (2 mM concentrations of racemic esters). Hydrolyses studies confirmed [3] that all (R)-enantiomers of prepared esters are much better substrates than (S)-enantiomers. In the case of N-benzyl protected esters, the difference for all prepared esters was even more pronounced. Introduction of bromine atom or methyl group in the meta or para position on the phenyl ring of benzyl moiety resulted in a remarkable improvement of the stereoselectivity: (R)-acetates and (S)-alcohols were isolated in a high optical purity (> 95 %). Thus, optically pure quinuclidin-3-ols can be prepared in the high yields and enantiopurity by the esterification, quarternization with benzyl bromide, BChE-catalysed hydrolysis and finally catalytic transfer hydrogenation. [1] Ines Primozic, Tomica Hrenar, Srdjanka Tomic and Zlatko Meic, Journal of Physical Organic Chemistry 15 (2002) 608-614. [2] Ines Primozic, Tomica Hrenar, Srdjanka Tomic and Zlatko Meic, European Journal of Organic Chemistry (2003) 295-301. [3] Ines Primozic, and Srdjanka Tomic, Croatica Chemica Acta 84 (2011) 245-249. 2011-10-31 2011-10-31T00:00:00Z http://www.sciforum.net/presentation/747 New thermotropic liquid crystals containing benzoxazole core and alkanoyloxy chain at the end group of the molecules (Cn-1H2n-1COO-, n = 14, 16, 18) was synthesized. The present compounds are enantiotropic smectic A liquid crystals.It was also found that the end groups of the molecules and polar chloro substituent at the benzoxazole fragment had effect on the mesomorphic properties. 2011-10-31 2011-10-31T00:00:00Z http://www.sciforum.net/presentation/581 A simple, inexpensive, environmentally friendly and efficient route for the synthesis of 3,4-dihydropyrimidin-2(1H)-one derivatives via the one-pot three-component Biginelli reaction using pentafluorophenylammonium triflate (PFPAT) as a catalyst is described. PFPAT organocatalyst is air-stable, cost-effective, easy to handle, and easily removed from the reaction mixtures. 2011-10-31 2011-10-31T00:00:00Z http://www.sciforum.net/presentation/683 Over the last decades triterpenoids have drawn attention because of their anti-inflammatory, anti-oedematous, antitumor, and anti-HIV activities. Abundant in many plants, these metabolites are valuable natural raw materials to perform chemicals modifications and obtain semisynthetic analogs for structure-activity relationship studies. Asteraceae family constitutes a rich source of several pentacyclic mono-alcohols, diols and triols terpenes such as calenduladiol, faradiol, heliantriol B2, taraxasterol, arnidiol, lupeol, etc. Acetylcholine serves as a neurotransmitter in the central and peripheral nervous system. Acetylcholinesterase (AChE) stops the function of acetylcholine by its hydrolytic destruction in the cholinergic synapses. Enhancement of acetylcholine level in the brain inhibiting AChE is considered one of the most promising approaches for treating Alzheimer's disease. In the course of our ongoing search of natural AChE inhibitors, we isolated calenduladiol (1), in good yields, from ethanolic extract of Chuquiraga erinacea D. don. subsp. erinacea (Asteraceae), collected in southwest of Buenos Aires province, Argentina. This triterpene elicited moderate AChE inhibition which encouraged us to synthesize five calenduladiol derivatives: 30-oxo-calenduladiol (2), 30-hydroxy-calenduladiol (3), calenduladiol diacetate (4), 30-oxo-calenduladiol diacetate (5) and 30-hydroxy-calenduladiol triacetate (6). Compounds 2 and 3 were obtained by oxidation with SeO2 and, 4, 5 and 6 by esterification with Ac2O and pyridine from compounds 1, 2 and 3 respectively. Compounds 2-6 which were obtained in good yields and characterized by 1H and 13C NMR spectroscopy. The oxidized analogs, 2 and 3 resulted to be the most active ones with a 43 % and 40 % of AChE inhibition at 0.2 mM, respectively, in the Ellman's assay. Acetylated derivatives (4-6) elicited a weak activity compared with 1, at the same concentration. Our results indicate that calenduladiol analogues oxidized at C-30 could be a promising strategy for the enhancement of pharmacological properties of this type of triterpene alcohols. 2011-10-31 2011-10-31T00:00:00Z http://www.sciforum.net/presentation/652 Novel mulriple polymer polyaniline/Bi2SnTiO7 was synthesized by chemical oxidation in-situ polymerization method and sol-gel method for the first time. The structural and photocatalytic properties of novel polyaniline/Bi2SnTiO7 have been characterized by X-ray diffraction, scanning electron microscopy, X-ray photoelectron spectroscopy and X-ray spectrometry. The photocatalytic degradation of methylene blue was realized under visible light irradiation with novel polyaniline/Bi2SnTiO7 as catalyst. The results showed that novel polyaniline/Bi2SnTiO7 owned higher catalytic activity compared with Bi2SnTiO7 or pure TiO2 or N-doped TiO2 for photocatalytic degradation of methylene blue under visible light irradiation. The photocatalytic degradation of methylene blue with novel polyaniline/Bi2SnTiO7 or N-doped TiO2 as catalyst followed the first-order reaction kinetics, and the first-order rate constant was 0.01350 or 0.00333 min-1. After visible light irradiation for 220 min with novel polyaniline/Bi2SnTiO7 as catalyst, complete removal and mineralization of methylene blue was observed. The reduction of the total organic carbon, the formation of inorganic products, SO42- and NO3-, and the evolution of CO2 revealed the continuous mineralization of methylene blue during the photocatalytic process. The possible photocatalytic degradation pathway of methylene blue was obtained under visible light irradiation. Novel mulriple polymer polyaniline/Bi2SnTiO7/(visible light) photocatalysis system was found to be suitable for textile industry wastewater treatment and could be used to solve other environmental chemical pollution problems. 2011-10-31 2011-10-31T00:00:00Z http://www.sciforum.net/presentation/609 A novel class of backbone-modified oligonucleotide analogs has emerged since the discovery of CuI-catalyzed [3+2] azide-alkyne cycloaddition. These are oligonucleotide analogs with 1,4-substituted 1,2,3-triazoles in internucleotide linkages. Of all such analogs known to date, only the triazole-linked deoxythymidine decamer has been reported to show enhanced binding affinity to complementary DNA. Importantly, it is a fully modified (dT)10 analog. Irregular oligonucleotides bearing the same backbone modification have not been described so far. With a goal of investigating sequence and regularity dependence of the effect of this modification on duplex stability, we have designed sequentially heterogenous modified oligonucleotides, which can be prepared using a modified dinuleoside block. In this paper we report on the synthesis of the dithymidine phosphoramidite block with the triazole linker, its utilization in oligonucleotide synthesis and hybridization data of thus obtained oligonucleotide analogs. The effect of single and multiple modifications on stability of irregular sequence duplexes is assessed and compared with published data for the oligo(T)/oligo(A) duplex. We also compare the effect of the linker concerned with that of a shorter triazole linker. 2011-10-31 2011-10-31T00:00:00Z http://www.sciforum.net/presentation/763 A rapid and efficient procedure for the synthesis of N-arylamines by aromatic nucleophilic substitution of activated as well as unactivated aryl halides with various amines using solvent-free microwaves activation under green chemistry conditions was described. Good to excellent yields were obtained in very short reaction time. 2011-10-31 2011-10-31T00:00:00Z http://www.sciforum.net/presentation/772 A facile protocol for the one-pot synthesis of pyrimidinone derivatives through Biginelli reaction in the presence of catalytic amount of the nano-ordered MCM-41-SO3H anchored sulfonic acid (MCM-41-SO3H) has been described. The reaction proceeds smoothly under solvent-free conditions on grinding of a mixture of different aldehydes, ethyl acetoacetate and urea in a mortar. 2011-10-31 2011-10-31T00:00:00Z http://www.sciforum.net/presentation/685 Fluorescent probes are widely used in membrane biophysical studies to investigate the properties of the molecular environment of cell membrane and biochemical processes related to it. These probes provide information of the molecular environment trough changes of their photophysical properties. While these probes can provide valuable information of the membrane molecular properties, a clear structural description, at the molecular scale, of the membrane properties surrounding the fluorescent molecular probe, is essential for the interpretation of the experimental fluorescent signal. In this work, we studied the membrane permeation properties of four benzo[a]phenoxazinium fluorescent probes with different alkyl chains in the tetracyclic ring in DPPC membranes using molecular modelling techniques . We describe the molecular mechanism of interaction between the molecular probes and the DPPC lipids. We show that probes can be preferentially located at the membrane water interface interaction with the lipid polar groups, while others can be cross the membrane in a passive way. This processes is dependent on the tetracyclic substitutions and alkyl chain present in the fluorescent probe. These findings can provide a detailed rational of the structural properties surrounding the molecular probes that could be correlated with the experimentally measured fluorescence. 2011-10-31 2011-10-31T00:00:00Z http://www.sciforum.net/presentation/661 Fluorescent cholic acid derivatives are used as well in biological investigations as in chemical. As nature products their derivatives can be used in research of hepatotoxicity, cell transport system and distribution of the drugs in organisms. Cholic acid-based fluorescent sensors are used to detection different organic and inorganic compounds such as drugs, toxins, amino acids and heavy metals. 'Fluorophore–spacer–receptor' motif is an effective way of designing of plurality of chemosensors and has used in the last two decades. Coumarines containing electron donating groups are natural non-toxic compounds that have good fluorescent parameters. It is also known that rearrangement of imino-coumarines is the easy way to fluorescent coumarine derivatives. Hence, in present work fluorescent receptor precursors bearing coumarine fluorophore on C24 of cholic acid were designed and synthesized in 3 steps. The condensation of 2-imino-coumarine-3-carboxamides with cholic hydrazide in acetic acid with following recyclization in diphenyl ether formed the corresponding 1,3,4-oxadiazol-2-yl-coumarin derivatives in moderate to good yields. Structures of synthesized 7 examples fluorescent cholic-based derivatives were confirmed by NMR H1 and MS. The UV-absorption and fluorescent spectrum of the newly synthesized compounds was measured in acetonitrile and ethanol solutions. It is shown that wave length of emitted irradiation is in the range from 420 to 510nm and quantum yield is in the range from 0,02 to 0,58. Either wave length or quantum yields depend on donation value and position of substitution group in coumarine fragment. Sensor-precursors that are developed in this way are very flexible to modifications. On the one hand, it's possible to modify easily the coumarine fragment in order to change the wavelength of fluorescence and color, respectively, on the other hand, by the introduction of various substituents on the hydroxyl groups in cholic fragment it's allowed to control the response level from attaching guest-substances. 2011-10-31 2011-10-31T00:00:00Z http://www.sciforum.net/presentation/662 Carbohydrates play a fundamental role in a wide number of molecular recognition phenomena. In fact they are the most important mediators in the intercellular interactions and with extracellular matrix components, such as enzyme, hormones, toxins, bacteria, virus, etc. For this reason, during last years there has been a growing interest in bioactive oligosaccharides, since tailor-made sugar based compounds able to interfere in key biological mechanisms would represent a powerful weapons in biomedicine. However the development of saccharide-based drugs has beeen largely hampered by the typical challenges associated with classical carbohydrate synthesis. Sugar mimics endowed with very similar biological properties, but structurally and synthetically simpler than their natural counterparts, may offer a valuable alternative.A simple and efficient approach to the synthesis of pseudo-oligosaccharides based on intramolecular cyclization promoted by various selenium electrophile of heterodymer sugar olefin is described. Various selenocyclic ether are obtained as two diastereoisomers trans and cis and after column chromatography are isolated in enantiomerically pure form These compounds can be seen as potential precursors of carbohydrate mimics, in fact via syn elimination of selenoxides followed by further functionalization of the C-C double bond is possible to obtain analogous tryciclic sugar. This procedure represent an innovative use of selenium chemistry applied at the carbohydrates. 2011-10-31 2011-10-31T00:00:00Z http://www.sciforum.net/presentation/670 An asymmetric aldol reaction is one of the most common methods for carbon-carbon bond formation in organic molecules. It is extensively applied in the synthesis of carbohydrates, amino sugares, steroids, and other valuable chiral organic compounds. It provides an atom-economic approach to β-hydroxyl carbonyls, which make up a large family of chiral intermediates for the synthesis of biologically active substances and natural products. In continuation of our research in environmentally benign and microwave assisted conditions, we now report an operationally simple and fast method for the preparation of aldol products by one-pot condition reaction. In this research, the direct aldol reaction of ketones with aromatic aldehydes using catalytic amount of RuCl3.nH2O and chiral ligand proceeded smoothly under extremely mild conditions to give the corresponding aldol adducts in good yields with moderate to good diastereoselectivity. The system can efficiently proceed at room temperature with a small excess of ketone. From a practical and economic point of view this reaction condition is convenient with respect to most of other protocols where a large excess of ketone is used. Also, microwave technique offers simple, clean, fast, efficient, and economic for the synthesis of a large number of aldol adducts. All the synthesized compounds are confirmed by spectroscopy methods such as 1H-NMR, 13C-NMR and IR. Important advantages of this thechnology include highly accelerated rate of the reaction, reduction in reaction time with an improvement in the yield and quality of the products. 2011-10-31 2011-10-31T00:00:00Z http://www.sciforum.net/presentation/693 Today the aminoglycosides are still the most commonly used antibiotics worldwide thanks to the combination of their high efficacy with low cost. The interest of aminoglycoside antibiotics is due to their use in treatment of wide variety infections. These compounds act on gram-positive and gram-negative bacteria as protein synthesis inhibitors.[1] However, they are nephrotoxic and ototoxic in some cases, thus limiting its use. Kanamycin is an aminoglycoside antibiotic with multiple therapeutic applications. A previous step of their synthesis is the formation of 3-amino-3-deoxy-D-glucose from commercial available products. Integration of phenylhydrazine with a sugar derived dialdehyde (2) in water, as a key step, has been used[2] as an elegant and easy strategy synthesis. However, a low reproducibility of this method makes synthetic chemists reluctant to its use, in such a way that other routes of synthesis of 3-amino-3-deoxy-D-glucose are preferred.[3] All this, despite the fact that the above mentioned integration reaction can be considered as a representative example of green chemistry.[4] We have revisited this process and we report herein new NMR and IR data of compounds 2 and 3 that they confirm the structures proposed in literature. In addition, we describe novel different conditions for their synthesis that reduce the time of reactions, especially in case of dialdehyde 2. We thank the AECID (Projects A/023577/09 and A/040322/10) and the 'Junta de Andalucía' (FQM 142 and Project P09-AGR-4597) for financial support. [1] a) Li, J.; Chang. T., Anti-Infec. Agents in Med. Chem. 2006, 5, 255.; b) Corey, E. J.; Czakó, B.; Kürti, L., Molecules and Medicine. John Wiley & Sons, New Jersey, 2007 [2] Patroni, J.; Stick, R. Aust. J. Chem, 1985, 38, 947 and reference therein. [3] Faghih, R.; Cabrera-Escribano, F. et al, J. Org. Chem. 1986, 51, 4558 [4] Anastas, Y.; Warner, J.C. Green Chemistry: theory and practice.Oxford University Press, New York, 1998 2011-10-31 2011-10-31T00:00:00Z http://www.sciforum.net/presentation/695 The interest of fluorescent carbohydrates is due to wide applications in biology and environmental technology. For example, water soluble glucose based imino-anthracenyl derivatives have been shown to recognize specifically Hg2+ (which is highly toxic and causes DNA damage and impair mitosis) by switch-on fluorescence.[1] Fluorescence is a powerful technique as a consequence of its highly sensible and specific detection methods. [2],[3] With the aim to generate new derivatives with biological, pharmacological and technological properties, we design the here presented compounds using as diversity point (see Scheme), the amino group. We have selected coumarins as chromophore units (CU), due to their demonstrated anticoagulant activity and easy availability. On the other hand, fluorescent aldehydes have been chosen as fluorescence sources for their chemosensor potential activity in a wide variety of fields. We report here on new fluorescent derivatives of D-glucosamine (1) previous protection of its hydroxyl groups. These derivatives having general structures 2 and 3, have been prepared in good yields by: a) nucleophilic attack of the amino group to activated carboxycoumarins, and b) by reductive amination, respectively. We thank the AECID (Projects A/023577/09 and A/040322/10) and the 'Junta de Andalucía' (FQM 142 and Project P09-AGR-4597) for financial support. [1] Mitra, A.; Mittal, K. A. and Rao, P. C. Chem. Comm., 2011, 47, 2565 and references therein. [2] Lee, D.Y.; Singh, N. and Jang, D. O. Tetrahedron Lett. 2010, 51, 1103 [3] a) Rettig, W. Applied Fluorescence in Chemistry, Biology and Medicine; Springer: New York, 1999. b) Christensen, L.; Norgaard, R.; Bro, S. and Engelsen, B. Chem. Rev. 2006, 106, 1979. 2011-10-31 2011-10-31T00:00:00Z http://www.sciforum.net/presentation/663 Because of their ready availability, great structural and electronic diversity, easy handling and peculiar chemical behaviour organoselenium compounds are nowadays considered versatile reagents for many synthetic transformations. a,b-Unsaturated selenones represent an interesting example: the electron-withdrawing effect combined with the excellent nucleofugal ability of the phenylselenonyl group makes these compounds useful 1,2-bis(electrophilic) synthons. Recently we have conveniently employed readily available a,b-unsaturated selenones and 1,3-dicarbonyl compounds or cyanoacetates for the organocatalytic asymmetric assembly of structurally complex spirolactones or cyclopropanes. We now report some preliminary results concerning the use of phenyl vinyl selenone and cyclic b-ketoesters for the stereoselective formation of sterically constrained b-aminoesters containing two adjacent stereocenters. The sequential synthesis involves the following steps: a) a highly enantioselective Michael addition catalyzed by a cinchona alkaloid derived catalyst, b) the conversion of the resulting Michael adduct to the corresponding azide by nucleophilic substitution of the phenylselenonyl group, c) a cyclization reaction via a Staudinger/aza-Wittig sequence, d) a diastereoselective reduction of the resulting cyclic imine. b-Aminoesters are obtained with good yields and excellent stereocontrol. 2011-10-30 2011-10-30T00:00:00Z http://www.sciforum.net/presentation/715 The lower molecular weight hydrocarbons that can be mapped on the buckminsterfullerene (C60) structure are commonly known as "buckybowls" or "geodesic polyarenes" and have the distinctive characteristics of preserving the curvature and aromaticity of fullerene. These bowl-shaped structures are expected to be quite rigid. Nevertheless, the smaller members of the family, in spite of its substantial curvature are surprisingly flexible undergoing rapid bowl-to-bowl inversion in solution as evidenced by the dynamic NMR behavior of C20H10 (corannulene) and several of its derivatives. With the aim of gaining understanding in the bowl-to-bowl inversion, the present theoretical study has explored the effect that substitution of some of the hydrogen atoms of corannulene has on this process. The model systems studied have the formula C20H10-nRn with R = -Cl, -Br, -C≡CH, -CH3 and n = 0, 2, 4, 5, 6, 8, and 10. It is observed that the bowl depth is reduced only by high substitution levels or by a substitution pattern that conduces to important peri interactions. Full substitution with bulky groups causes a pronounced repulsion and the deformation of the transition structure for bowl inversion that otherwise is planar. The activation barrier for the inversion – bowl depth data fit an empirical quartic/quadratic function used previously in similar systems but the coefficients of the fitting don't follow the predicted substituent independency. 2011-10-30 2011-10-30T00:00:00Z http://www.sciforum.net/presentation/762 A new class of β-amino alcohol and diamine ligands has been prepared from isosorbide as a chiral renewable source. The efficiency of these ligands has been evaluated for the metal-catalyzed enantioselective reduction of aromatic ketones by transfer hydrogenation, giving excellent conversion and good enantioselectivity. 2011-10-30 2011-10-30T00:00:00Z http://www.sciforum.net/presentation/671 The development of new antimicrobial and anti cancer therapeutic agents is one of the fundamental goals in medicinal chemistry. Chiral thioureas and their derivatives display a wide range of biological activities such as antibacterial, antiviral and antifungal (1). In addition, some of these compounds could be used as catalysts in the asymmetric reactions such as the Michael addition to nitroalkenes and the Biginelli reaction. Therefore, recent efforts have been devoted to the synthesis of these compounds (2). In the light of this information, novel chiral thioureas bearing amino acids and 2-aminophenol moieties were synthesized in good yields and the structures of the compounds were characterized by elemental analysis, IR, 1H NMR and 13C NMR. References (1) Saeed, S., Rashid, N., Jones, P., Ali, M., Hussain, R., Eur. J. Med. Chem. 45, 2010, 1323-1331 (2) Sheng-Li, Z., Chang-Wu, Z., Gang, Z., Tetrahedron: Asymmetry, 20, 2009, 1046-1051 2011-10-30 2011-10-30T00:00:00Z http://www.sciforum.net/presentation/568 N'-[(4-oxochromen-3-yl)methylidene]-4-R-furo[3,2-b]pyrrole-5-carboxhydrazides 3 were prepared by treatment of substituted carboxhydrazides 1 with 4-oxo-4H-chromen-3-carboxaldehyde 2 in ethanol in the presence of p-TsOH. Compounds 3 were subsequently used as ligands in complexation reactions with solutions of metal (M2+) chlorides or nitrates: [Ni(NO3)2.6H2O, Co(NO3)2.6H2O, CoCl2.6H2O, CuCl2.2H2O] to give complexes 4. 2011-10-30 2011-10-30T00:00:00Z http://www.sciforum.net/presentation/669 The ring-opening of epoxides with different nucleophiles is an important strategy for the formation of 1,2-bifunctionalized building blocks. A wide variety of nucleophiles such as alcohols, phenols and carboxylic acids have been utilized in this reaction. Oxygen nucleophiles are among the most important ones as they lead to pharmaceutically important Þ-alkoxy and Þ-aryloxy alcohols.1 Recently, we reported the first ring-opening of epichlorohydrin with salicylaldehyde derivatives in the presence of Jacobsen' s Co(III)salen catalyst.2 The final ring-opened product is a multifunctional aldehyde containing a stereocenter in addition to the alkyl halide and alcohol functional groups. In this study, we report the preparation of multifunctional chiral Schiff base ligands by the condesation of 4-(3-chloro-2-hydroxypropoxy)-2-hydroxybenzaldehyde with primary amines (2-aminophenol and 2-amino-2-methyl-1-propanol). The ligands have been characterized by elemental analysis, IR, 1H and 13C NMR spectroscopies. References 1. J. M. Ready, E. N. Jacobsen, J. Am. Chem. Soc., 1999, 121, 6086. 2. L. Karadeniz, G. Koz, K. Aydin, S. T. Astley, Turkish Journal of Chemistry, 2010, 34, 711. 2011-10-30 2011-10-30T00:00:00Z http://www.sciforum.net/presentation/690 The reaction of tris(oxiran-2-ylmethyl)-1,3,5-triazinane-2,4,6-trione with phenol or N-methylaniline promoted by microwave heating, under solventless conditions, led to the opening of the oxirane ring through the less hindered carbon, leading to tripodal triols with C3 symmetry in good yields. 2011-10-30 2011-10-30T00:00:00Z http://www.sciforum.net/presentation/777 Reaction of a-D-glucosamine hydrochloride with different substituted benzaldehyde have been investigated in the presence of various inorganic and organic bases. Based on obtained results, the general synthetic method for azomethines of a-D-glucosamine hydrochloride and substituted benzaldehyde proposed. 2011-10-30 2011-10-30T00:00:00Z http://www.sciforum.net/presentation/778 Some novel substituted acetophenone and benzaldehyde (2',3',4',6'-tetra-O-acetyl-β-D-glucopyranosyl)-thiosemicarbazones were synthesized by reaction of 2,3,4,6-tetra-O-acetyl-β-D-glucopyranosyl thiosemicarbazide and substituted acetophenones and benzaldehydes. The reaction was performed using microwave-assisted method. The compounds have converted into 2-iminothiazolidin-4-ones by reaction with ethyl bromoacetate in dichloromethane in the presence of anhydrous sodium acetate. Structures of obtained compounds were confirmed by spectroscopic methods. 2011-10-30 2011-10-30T00:00:00Z http://www.sciforum.net/presentation/783 The research on fluorescent carbostyrils of the general type I has been going on in our work group for several years. In the course of these investigations we found that carbostyrils of type II having a 4-p-toluenesulfonyl group in position 4 - formed as not isolated intermediates in many cases during our investigations of strongly fluorescent 4-cyano-carbostyrils - showed surprisingly strong fluorescence: they exhibit long-wave absorption and fluorescence properties, and high quantum yields. These findings prompted us to investigate the synthesis and luminescence properties of 4-p-toluenesulfonyl-carbostyrils of type II dependent on the nature of substituents in position 3. In this contribution new types of the acceptor group in position 4 such as toluenesulfonyl and toluenesulfonyloxy groups are investigated, which were in earlier investigations applied as intermediates for e.g. strong fluorescent cyano-carbostyrils. Observations during the reaction sequences revealed that they have already similar strong fluorescence properties as the desired target molecules. 2011-10-30 2011-10-30T00:00:00Z http://www.sciforum.net/presentation/776 Several 5- and 7-substituted isatins were prepared from corresponding anilines or unsubstituted isatin. Some novel substituted isatin (2,3,4,6-tetra-O-acetyl-β-D-galactopyranosyl)thiosemicarbazones were synthesized by reaction of 2,3,4,6-tetra-O-acetyl-β-D-galactopyranosyl thiosemicarbazide with these isatins. The reaction was carried out by using microwave-assisted heating method. 2011-10-30 2011-10-30T00:00:00Z http://www.sciforum.net/presentation/580 The main objective of the project was to find conditions of the synthesis of pyrano[2,3-c]pyrazoles in accordance with the principles of "green" chemistry. Pyrano[2,3-c]pyrazoles possess a broad spectrum of biological activity. For example, they can be used as anticancer agents and enzyme inhibitors. Known methods for the synthesis of such compounds involve using large volumes of toxic solvents and are complicated in usage. In the course of the our work the reactions between malononitrile, 3-methyl-2-pyrazoline-5-one and benzaldehyde under solvent-free conditions and in small quantity of water in the presence of various amounts of non-toxic bases (potassium fluoride, sodium acetate, and sodium hydroxide) were studied. As a result, optimal conditions for the synthesis of 6-amino-3-methyl-4-phenyl-1,4-dihydropyrano[2,3-c]pyrazole-5-carbonitrile (one of the simplest pyrano[2,3-c]pyrazoles) have been found. These conditions were tested on synthesis of difficult functionally substituted pyrano[2,3-c]pyrazoles. Thus, it was found that in optimal conditions the reaction between malononitrile, 3-methyl-2-pyrazoline-5-one and aromatic aldehydes in small quantity of water and in the presence of 5 mol.% of sodium hydroxide leads to pyrano[2,3-c]pyrazoles selectively in high yield (more than 93%). Carrying out the reaction in water and using sodium hydroxide as the base allows to reduce the cost of the process and significantly improve its environmental friendliness. Using small amounts of water allows to use the working capacity of a chemical reactor more efficiently and to avoid significant losses at the isolation stage. Thus, the proposed process is more efficient and environmentally friendly compared to those known today. 2011-10-30 2011-10-30T00:00:00Z http://www.sciforum.net/presentation/775 Some new substituted isatin (2,3,4,6-tetra-O-acetyl-β-D-glucopyranosyl)thiosemicarbazones were synthesized by reaction of 2,3,4,6-tetra-O-acetyl-β-D-glucopyranosyl thiosemicarbazide and corresponding substituted isatin using microwave-assisted heating method. 2011-10-30 2011-10-30T00:00:00Z http://www.sciforum.net/presentation/598 Mitotic spindle dynamics represents an important target of anticancer drugs. Many small natural and semi-synthetic drugs influence tubulin assembly and cause apoptosis of excessively dividing cells. Molecules attacking the colchicine domain of tubulin block its polymerization. Despite this there are colchicine site inhibitors (CSIs) not used in cancer treatment due to their high toxicity, low activity or poor solubility. On the basis of the structure-activity relationships, aryltetralin and dibenzylbutyrolactone lignan-like molecules were designed in an attempt to obtain active drugs. Structure modifications embraced the elimination of typically toxic groups. Two new dibenzylbutyrolactone-type compounds were prepared by total synthesis from substituted benzaldehyde, benzyl bromide and dimethyl succinate. The Stobbe condensation of the substituted benzaldehyde with dimethyl succinate followed with the selective hydrogenation of the double bond and the selective reduction of the ester in the presence of carboxyl led to the β-benzylbutyrolactone. Alkylation of butyrolactone enolate with a substituted benzyl bromide provided the final 2-hydroxy-5'-methoxy-4'-O-methyl arctigenin (1) after phenolic group deprotection. The target 2,5'-dimethoxy-4'-O-methyl arctigenin (2) was obtained by means of one-step methylation of dibenzylbutyrolactone derivative 1. 2011-10-28 2011-10-28T00:00:00Z http://www.sciforum.net/presentation/678 Amines are present in many naturally occurring bioactive molecules showing interesting herbicidal and fungicidal activities, and they are also utilised as versatile intermediates for the synthesis of pharmaceuticals, agrochemicals, dyes, and as valuable building blocks in synthetic organic chemistry. Amines can be synthesized by the reaction of aldehydes or ketones with ammonia, primary or secondary amines in presence of different reducing agents. This is the so-called reductive amination reaction which is described as direct when the carbonyl compound and the amine are mixed together with a suitable reducing agent in a single operation, without preformation of an imine or an iminium salt. On the other hand, the reducing systems based on the use of alkali-metals in combination with arenes in aprotic media, with the arene acting as electron carrier have received much attention. In the last years, we have been working on the preparation of transition metal nanoparticles by fast reduction of the corresponding metal chlorides with lithium and a catalytic amount of an arene [naphthalene, 4,4´-di-tert-butylbiphenyl (DTBB)] as electron carrier. In this work we want to introduce a simple and efficient procedure for the direct reductive amination of aldehydes for the one-pot synthesis of secondary amines, using primary amines as starting materials in the presence of lithium powder and a catalytic amount of DTBB or a polymer supported naphthalene as electron carrier. The direct reductive amination of a variety of aldehydes was achieved simply by adding a mixture of the corresponding carbonyl compound and the amine, over a solution of the lithium arenide in THF at room temperature. For most of the substrates tested the main reaction products were the secondary amines along with variable amounts of the corresponding alcohol and imine products. DFT methods have been applied in order to explain the differences in reactivity observed. 2011-10-28 2011-10-28T00:00:00Z http://www.sciforum.net/presentation/751 The hypothesis of vector alignment should allow for the rational design of intensely colored conjugated organic dyes by providing a means of predicting the structures that provide a straight path for the π electrons to move across the entire molecule in response to perturbation by a passing photon. 2011-10-27 2011-10-27T00:00:00Z http://www.sciforum.net/presentation/664 In the past few decades, the synthesis of new heterocyclic compounds has been a subject of great interest due to their wide applicability. Among a large variety of heterocyclic compounds, heterocycles containing phthalazine moiety were reported to possess anticonvulsant, cardiotonic, and vasorelaxant activities. Therefore, a number of methods have been reported for the synthesis of phthalazine derivatives. Despite the available methods, the development of new synthetic methods for the efficient preparation of heterocycles containing phthalazine ring fragment is therefore an interesting challenge. With these precedents and with the aim of preparing new derivatives with potential pharmacological activity, we have synthesized new phthalazinedione derivatives by introducing halogenoalkyl substituents in one of the NH-nucleophilic groups. So, we started with 4-chloro-phthalic anhydride, which reacted with methyl- hydrazine, in MW mild conditions. After purification, we obtained two different isomers of phthalizediones, 8-chloro-2-methyl-2, 3-dihydro-phthalazine-1, 4-dione and 8-chloro-3-methyl-2, 3-dihydro-phthalazine-1,4-dione. Then halogenoalkyl substituents with different chain length were introduced in the nitrogen group in a very efficient way. Finally halogen atom of alkyl chains was replaced by an azide group. The described synthetic route will allow us to condense a nitrogen heterocyclic ring on the phatalazinone moiety and obtain a new tricyclic scaffold with promising pharmacological properties. 2011-10-27 2011-10-27T00:00:00Z http://www.sciforum.net/presentation/586 In this study, a series of new seven ring-substituted 4-chloro-2-styrylquinazoline derivatives were prepared. The procedures for synthesis of the compounds are presented. The compounds were analyzed using RP-HPLC to determine lipophilicity. They were tested for their activity related to inhibition of photosynthetic electron transport (PET) in spinach (Spinacia oleracea L.) chloroplasts. For all the compounds, the relationships between the lipophilicity and the chemical structure of the studied compounds are discussed, as well as their structure-activity relationships (SAR). 2011-10-27 2011-10-27T00:00:00Z http://www.sciforum.net/presentation/653 Bacterial diseases of freshwater fish epithelia have been extensively studied; however in marine fishes relatively few bacterial skin and gill diseases have been characterized. Tenacibaculum maritimum, a Gram-negative and filamentous bacterium, has been described as the etiological agent of tenacibaculosis in marine fish. Since 1990, as the farming of fish became a steadily growing industry, this disease has been widely distributed in several countries and is considered a limiting factor for the culture of many species of commercial value in the world. Among the drugs used in the past few years enrofloxacin proved to be the most useful compound in the control of tenacibaculosis outbreaks, although the rapid appearance of resistant strains has already been described. Therefore, it is important to discover new classes of selective antimicrobial drugs. Coumarin derivatives are a class of compounds that present a wide range of pharmacological activities. Among others, recent studies pay special attention to the antibiotic properties of the coumarin moiety. In order to contribute to the development of new agents, in the present communication we have synthesized new 3-arylcoumarin derivatives, structurally related with well know antibiotic novobiocin. On this scaffold we introduced substituents with different electronic, steric and/or lipophilic properties in different positions of the aromatic rings. The compounds have been prepared via a palladium-catalyzed coupling type Suzuki reaction of phenyliodonium zwitterion species previously synthesized by us. Further, were evaluated for antibacterial activity against bacterial and fungal strains. The preliminary results of biological activity and/or selectivity against Tenacibaculum Maritimum will be presented. 2011-10-27 2011-10-27T00:00:00Z http://www.sciforum.net/presentation/588 In this study a series of twenty-five substituted quinoline-2-carboxanilides were prepared. The procedures for synthesis of the compounds are presented. The compounds were tested for their activity related to inhibition of photosynthetic electron transport (PET) in spinach (Spinacia oleracea L.) chloroplasts. For all the compounds the structure-activity relationships (SAR) are discussed. 2011-10-27 2011-10-27T00:00:00Z http://www.sciforum.net/presentation/754 Camellia oil is used in cooking and soap making. The relative composition of the fatty acid components of the triglycerides is studied by NMR in Camellia Reticulata and Camellia Japonica. 2011-10-25 2011-10-25T00:00:00Z http://www.sciforum.net/presentation/633 Nevirapine (NVP) is a non-nucleoside reverse transcriptase inhibitor used against the human immunodeficiency virus type-1 (HIV-1), mostly to prevent mother-to-child HIV transmission in developing countries [1]. One of the limitations of NVP use is severe hepatotoxicity [2], which raises concerns about its chronic administration, particularly in the perinatal and pediatric settings. The reasons for the adverse effects of NVP administration are currently not clear, although there is increasing evidence that metabolic activation to reactive electrophiles capable of reacting with bionucleophiles is likely to be involved in the initiation of toxic responses. Phase I NVP metabolism involves oxidation of the 4-methyl substituent to 12-hydroxy-NVP , and the formation of phenolic derivatives that are conceivably capable of undergoing further metabolic oxidation to electrophilic quinoid species prone to react with bionucleophiles. The covalent adducts thus formed might be at the genesis of toxic responses. As part of a program aimed at evaluating the possible contribution of quinoid derivatives of NVP Phase I phenolic metabolites to the toxic responses elicited by the parent drug, we have investigated the oxidation of 2-hydroxy-NVP with dipotassium nitroso-disulfonate (Frémy's salt), mimicking the one-electron oxidation involved in enzyme-mediated metabolic oxidations. We report herein the isolation and full structural characterization (by NMR, MS and X-ray diffraction) of a 1H-pyrrole-2,5-dione derivative as a major product, stemming from an unusual pyridine ring contraction. References: [1] Lockman et al., N. Engl. J. Med. 2007, 356, 135-147. [2] Pollard et al., Clin. Ther 1998, 20, 1071–1092. Acknowledgments: We thank the Portuguese NMR Network (IST-UTL Center) and the Portuguese MS Network (IST-UTL Center) for providing access to the facilities. This work was supported in part by research 2011-10-25 2011-10-25T00:00:00Z http://www.sciforum.net/presentation/608 Photochemical oxidations of propylene by means of nitromethane and nitroethane were studied by UB3Lyp/6-31g in both the triplet and singlet states. It was studied the reaction paths giving propylene oxide. Gaussian03 was used to perform the calculations of the transition states of the reactions using QST2 and QST3 methods. Activation energies were calculated for every stage of the reactions. It was shown that the reaction proceeds mainly on the triplet potential surface energy. 2011-10-25 2011-10-25T00:00:00Z http://www.sciforum.net/presentation/632 Recently we have observed accelerating influence of trimethyl silyl chloride addition on the rate of the reactions of 5-(α-amino- α'-hydroxy)methylene Meldrum's Acids with amines particularly in the case of highly basic amines. However the nature of the aforementioned process remain unexplained. In proposed communication we wish to report insightful elucidation of this mechanism. The reaction under investigation involves simply addition of the trimethyl silyl chloride to the mixture of amine and carbamoyl Meldrum's acid derivative. We considered three potentially possible ways for the TMSCl action. The first possibility is formation of the O-silylated Meldrum acid, which would exclude formation of salt Meldrum's acid with amine, what undoubtedly hindered this reaction. The next way for the acceleration of the process is silylation of amine and subsequent reaction of silylated amine with carbamoyl Meldrum's acid. The last possibility is connected with the formation of equimolar amount of HCl during the reaction of TMSCl with carbamoyl Meldrum's acid or amine which should speed up the rate of decomposition of the Meldrum's acid derivative. The NMR monitored experiments as well classical experiments in which predicted intermediated were added to the reaction mixtures excluded formation of O-silylated Meldrum's acid as well as influence of formed HCl as a reason of the acceleration investigated reaction. Our experiments revealed that silylated amine is responsible for rate acceleration of the reaction amines and 5-(α-amino- α'-hydroxy)methylene Meldrum's Acids in the presence of TMSCl. 2011-10-25 2011-10-25T00:00:00Z http://www.sciforum.net/presentation/641 The use of fluorescent probes for detection of biological and organic molecules has increased in the last years due to their high sensitivity and ease of use compared to radiochemical methods. Interference with the measurement of the label fluorescence could occur in many biological samples, which display some fluorescence of their own, usually in the blue or green region of the spectrum. Consequently, in studies with biomolecules it is desirable to improve the sensitivity of detection using dyes with absorption and fluorescence in the red or near infrared spectral region. Therefore, in these spectral regions it is possible the use of inexpensive and effective excitation sources, e.g. laser diodes.1,2 Having these facts in mind and as a continuation of our previous research,3 fluorescent benzo[a]phenoxazinium chlorides possessing different substituents at position 2, namely propoxyl, 4-ethoxy-4-oxobutoxyl or 3-carboxypropoxyl groups, and at positions 5, 9 and 10 of the tetracyclic system, the amino, ethylamino and methyl groups, respectively, were synthesised. Absorption and emission studies of all compounds were also carried out in ethanol, water and at simulated physiological conditions (pH 7.4). Acknowledgements: Thanks are due to the Foundation for Science and Technology (Portugal) for its financial support of Centre of Chemistry. The NMR spectrometer Bruker Avance III 400 is part of the National NMR Network (RNRMN), and was purchased in the framework of the National Program for Scientific Re-equipment, contract REDE/1517/RMN/2005 with funds from POCI 2010 (FEDER) and FCT. References 1. Gonçalves, M.S.T. Chem. Rev. 2009, 109, 190. 2. Gonçalves, M.S.T. Optimized UV/Visible Fluorescent Markers in Advanced Fluorescence Reporters in Chemistry and Biology I. Fundamentals and Molecular Design, Demchenko A.P. (Volume Ed.), O.S. Wolfbeis (Series Ed.), Springer Series on Fluorescence, Vol. 8, Ch. 2, 27-64, Springer, Heidelberg, Germany, 2010. 3. a) Alves, C.M.A. et al Tetrahedron Lett. 2011, 52, 112. b) Naik, S. et al Eur. J. Org. Chem. 2011, 2491. 2011-10-25 2011-10-25T00:00:00Z http://www.sciforum.net/presentation/624 Neurodegenerative diseases are becoming prevalent pathologies in developed societies due to increasing average of life expectancy of the population. This fact has encouraged an active research in the development of new drugs, since they may represent an important advance in the treatment of complex diseases such as Alzheimer and Parkinson's diseases. Coumarins are a large family of compounds, of both natural and synthetic origin, important because of the pharmacological activities that this compounds display. Therefore, they occupy an important place in the organic and medicinal chemistry realm. In recent years, coumarins have been attracting interest because of their ability of inhibiting some enzymes. The versatility of the Perkin and Knoevenagel reactions has led to a large family of differently substituted compounds. In order to find the structural features for the human MAO inhibitory activity and selectivity, in the present communication we report the synthesis, pharmacological evaluation and a comparative study of a new series of 3-phenylcoumarins versus 3-benzoylcoumarins. A bromo atom and a methoxy/hydroxy substituent were introduced in these scaffolds at different positions of the coumarin moiety. The synthesized compounds were evaluated as MAO-A and B inhibitors using R-(-)-deprenyl and iproniazide as reference compounds. The presence or absence of a carbonyl group between the coumarin and the phenyl substituent in 3 position remarks, respectively, the MAO-A or MAO-B inhibitory activity. Some of the new compounds showed MAO-B inhibitory activities in the low nanomolar range. Compound 2 (IC50 = 1.35 nM) showed higher inhibitory activity than the R-(-)-deprenyl (IC50 = 19.60 nM) and higher MAO-B selectivity, with more than 74,074-fold inhibition level, respecting to the MAO-A isoform. In addition, docking experiments were carried out on hMAO-A and h-MAO-B structures. This study has provided new information about the enzyme-inhibitor interaction and the potential therapeutic application of this coumarin scaffolds. 2011-10-25 2011-10-25T00:00:00Z http://www.sciforum.net/presentation/689 The copper catalyzed Huisgen reaction was used for the synthesis of two derivatives of 1H-1,2,3-triazol-1,3,5-triazinane-2,4,6-trione. One from tris(2-azidoethyl)-1,3,5-triazinane-2,4,6-trione and phenylacetylene, and the other by coupling of 1,3,5-tri(prop-2-yn-1-yl)-1,3,5-triazinane-2,4,6-trione with benzyl azide. 2011-10-25 2011-10-25T00:00:00Z http://www.sciforum.net/presentation/702 Triethylammonium 4-aryl-3,5-dicyano-6-oxo-1,4,5,6-tetrahydropyridine-2-olates were obtained by reaction of (E)-3-aryl-2-cyanoacrylamides with 1-cyanoacetyl-3,5-dimethylpyrazole in the presence of 1.5 eq. of Et3N (20 °C, acetone) in 55-98% yields. 2011-10-25 2011-10-25T00:00:00Z http://www.sciforum.net/presentation/656 The genome DNA is constantly exposed to endogenous and exogenous oxidative stresses. Damaged DNA can cause mutations, which may increase the risk of developing cancer, aging, and other diseases. Various oxidative stresses lead to G:C–T:A and G:C–C:G transversions, because guanine is highly susceptible to oxidative stress in the DNA, owing to the lowest oxidation potential among four nucleobases. One typical lesion product of guanine is 8-oxo-7,8-dihydroguanine (8oxoG), and DNA polymerases incorporate adenine but not guanine opposite 8oxoG lesions. More specifically, 8oxoG:A base pairs cause G:C–T:A transversions, and then the other oxidative guanine damages seem to cause G:C–C:G transversions. 2,5-diamino-4H-imidazol-4-one (Iz) and 2,2,4-triamino-5(2H)-oxazolone (Oz) are the oxidative guanine damages, which can pair with guanine, and several DNA polymerases incorporate guanine opposite these lesions in vitro. We previously reported that the calculated stabilization energy of Iz:G base pair is similar to that of C:G base pair and that of Oz:G base pair is planar and has two hydrogen bonds. Guanidinohydantoin (Gh) and spiroiminodihydantoin (Sp) are the oxidative products of 8oxoG. It was shown that Klenow fragment incorporated adenine and guanine opposite these lesions. Our previous study proposed Gh:G and Sp:G base pairs, however, the stabilization energy of these base pairs have not been calculated. Therefore, We estimated the stabilization energy of these base pairs by ab initio molecular orbital calculations. 2011-10-25 2011-10-25T00:00:00Z http://www.sciforum.net/presentation/655 The extraordinary structures and properties of fullerenes have had an important impact on nanotechnology as these compounds exhibit outstanding mechanical and electronic properties. 1,3-Dipolar cycloadditions (1,3-DCs) have proved to be a powerful way to functionalize these conjugated ? systems and have offered wide opportunities for the creation of new nanocarbon structures with potential application in biological, biotechnology, material science and medicinal chemistry. The 1,3-DCs of fullerene (C60) with nitrile oxides, RCNO, have been studied in the gas phase using density functional theory (DFT) at the B3LYP/6-31G(d) level. Energetic and kinetic parameters have been determined at room temperature so as to investigate the effect of electron-withdrawing (R = F, Cl, Br, NC, CN and NO2) and electron-releasing (R = Me and Et) substituents attached to the nitrile oxides on the 1,3-DCs. These parameters have been interpreted in terms of group electronegativity and DFT reactivity indices. An unexpected behaviour was observed for the 1,3-DC involving FCNO as these reactions have some pseudodiradical character. Inspired by the results of the 1,3-DCs of nitrile oxides to C60, we have extended this theoretical gas phase research to the addition of a second HCNO to the cycloadduct of the addition of HCNO on C60. The various possibilities for the second addition are being explored with the aim of determining the thermodynamic and kinetic products. The findings of our research should be helpful to experimentalists in their quests for functionalized fullerenes. 2011-10-24 2011-10-24T00:00:00Z http://www.sciforum.net/presentation/645 Corannulene is an unsaturated hydrocarbon composed of fused rings, one central five-membered ring and five peripheral six-membered rings. Its structure can be considered as a portion of C60. Corannulene is a curved pi surface, but unlike C60, it has two completely different faces: one concave (inside) and one convex (outside). In this work, computational modeling of the binding between alkali metals cations and corannulene has been performed at the DFT and MP2 levels. Different isomers of the corannulene/M+ binding have been studied and the transition states interconnecting local minima were located. The alkali cations can be bound to five or six membered ring in both faces. In DFT calculations, the binding to the convex face (outside) is favored relative to the concave face for the three alkali cations as it already has been published [R.C. Dunbar, J. Phys. Chem. A 2002, 106, 9809]. For Li+ and Na+, MP2 calculations are very similar and show the same trend, but for K+ the calculations are quite different and the trend is reversed. According to our results, migration of cations can take place over the convex or the concave pi-face. There are two ways to transform a concave complex in a convex complex: migration across the edge of corannulene and bowl-to-bowl inversion. 2011-10-24 2011-10-24T00:00:00Z http://www.sciforum.net/presentation/700 The title compound was prepared from 2,6-difluorophenol in four steps. Acetylation, followed by nitration, reduction to the amine and diazotization/azide formation proceeded in the expected fashion. A copper-catalyzed Huisgen cyclization between the compound and phenylacetylene was carried out as a model and the triazole isolated. The propargyl ester of naproxen was prepared (naproxen/propargyl alcohol/carbodiimide) and the subsequent click reaction carried out. It is expected that this strategy will afford access to materials with dual biological activity. 2011-10-23 2011-10-23T00:00:00Z http://www.sciforum.net/presentation/672 One of the most important transformations of glycidic esters is their decarboxylation to give rise to aldehydes and ketones. A proposed mechanism for the decomposition of the ethyl 3-phenyl glycidate indicates that the ethyl side of the ester is eliminated as ethylene through a concerted six-membered cyclic transition state, and the unstable intermediate glycidic acid rapidly decarboxylates to give the corresponding aldehyde. Two possible pathways for the glycidic acid decarboxylation were proposed, one of them via a five-membered cyclic transition state and the other one via a four-membered cyclic transition state(Chuchani, G.; Tosta, M.; Rotinov, A.; Herize, A. J. Phys. Org. Chem. 2004, 17, 694). An accurate experimental description of the glycidic acid decarboxylation is a challenging task, since the glycidic acids decompose even at room temperature. Therefore, the goal of this work is investigated the path more favored by decarboxylation. Theoretical calculations were carried out in order to probe this proposed mechanism. Geometries of the different reactants, products and intermediates were optimized at different levels of calculation. The vibrational frequencies were calculated at the same level. The results were compared with those from experiments. Theoretical calculations indicate that the glycidic acid decarboxylation occurs via a five-membered cyclic transition state. 2011-10-23 2011-10-23T00:00:00Z http://www.sciforum.net/presentation/629 Despite being intense in the gas phase, the strength of the interaction between a cation and an aromatic cloud decreases significantly when solvated. This effect has an important impact on a variety of systems where the cation•••pi interaction is known to play a key role. In the case of cation•••pi contacts involving aromatic amino acid residues, the degree of exposure to the solvent can be widely variable, so the interaction can be modulated by the environment in an almost continuous way. Most theoretical studies regarding cation•••amino acid interactions have been performed by considering simple alkaline cations in the gas phase. However, interactions can also be established with more complex cations from other amino acids, such as it is the case with arginine cationic side chain and the aromatic units in phenylalanine, tyrosine and tryptophan. In the present work ab initio and DFT methods were employed to study complexes formed by phenylalanine and a guanidinium cation representing the cationic chain of arginine. The results help understanding the impact of the interaction on the structure of phenylalanine, and constitute a first step towards the study of the effects caused by water molecules in the characteristics of these systems. 2011-10-23 2011-10-23T00:00:00Z http://www.sciforum.net/presentation/774 In this communication we present our initial synthetic studies to the natural product tulearin A. The total synthesis relies on the assembly of two chiral building blocks through regioselective nucleophilic epoxide opening and macrolactonization for the construction of 18-membered lactone skeleton. In this initial contribution we report the partial synthesis of the fragment C1-C7 containing three stereogenic centers where the key step is an asymmetric aldol condensation. 2011-10-23 2011-10-23T00:00:00Z http://www.sciforum.net/presentation/618 Interactions between cations and aromatic molecules can be often find on a large number of biomolecular systems, such as proteins and receptor-ligand complexes. In addition, its important role in biological processes such as molecular recognition, drug action, and protein folding has been revealed by extensive experimental and theoretical investigations. Most previous theoretical investigations of cation···p interactions, have been focused on their characteristics in the gas phase, with less attention to their behavior in aqueous environment. In this latter case, most of the work has been focused on the whole effect of water solution as a medium on the cation···p interactions. Hence, it is important studying the influence of individual water molecules on the interaction as the cation···p complex is sequentially hydrated. The ammonium···phenol and methylammonium···phenol cation···p complex was selected as a model system to explore how water molecules affect the cation···p interaction. To mimic the process of water molecules binding to a cation···p complex, water molecules were introduced into the complex one by one. The purpose of this study is studying the geometrical characteristic of cation···p complexes with different numbers of water molecules and to investigate how the binding of water molecules to an existing cation···p complex affects the cation···p interaction. 2011-10-22 2011-10-22T00:00:00Z http://www.sciforum.net/presentation/570 α-Alkylidene-γ-lactams and lactones are the active constituents of many natural and synthetic compounds exhibiting pronounced biological properties. They are able to act as Michael acceptors in the reaction with thiol groups of bionucleophiles or can readily form [2 + 2] cycloadducts with DNA bases. We have developed concise synthetic approaches towards exemplary representatives of α-methylene models that hinges upon the preliminary assembly of the lactam and lactone template. Subsequent installation of the methylidene by a metallation/alkylation/elimination sequence completed the elaboration of the racemic title compounds. The presence of a quaternary carbon center bearing the carboxylate function precluded the undesirable isomerization leading to the corresponding endocyclic unsaturated analogues. 2011-10-22 2011-10-22T00:00:00Z http://www.sciforum.net/presentation/654 Aliphatic polyesters are one of the classes of materials that can potentially meet the varying requirements put for tissue scaffolds. In recent years, much attention was paid to design biocompatible scaffolds for tissues that would have the similarity to natural tissues in terms of stiffness, flexibility and endurance. Polyesters of citric acid and diols are promising materials for tissue scaffolds. They are characterized by simplicity of synthesis, use of low-cost and non-toxic monomers as well as ease of controlling properties of obtained products by polymerization process operating conditions. Many attempts at modification of polyesters based on citric acid with natural polyols such as xylitol and mannitol have been observed in recent years. Synthetic polyesters can also be modified with vegetable oil-based polyols being diverse in terms of hydroxyl number and functionality, which leads to change of mechanical properties of obtained polyesters. In this work, the effect of rapeseed oil-based polyols addition on the properties of citric acid-based polyesters has been investigated. It has been found that modification with polyols leads to improvement of tensile strength of obtained materials and additionally in reduction of elongation at break values. However, the modification had no significant influence on swelling properties of achieved polyesters. 2011-10-22 2011-10-22T00:00:00Z http://www.sciforum.net/presentation/698 The Diels-Alder reaction of various reactive dienophiles with cyclopentadiene is reported. Rather than cracking dicyclopentadiene in a separate step, the reagents were mixed in a sealed tube and the reactions carried out at 185C. Conversion to the adducts is dependent on the nature of the dienophile and the reaction time. In those cases where stereochemistry is relevant, the endo/exo ratios are reported and compared to those reported at lower temperatures. 2011-10-22 2011-10-22T00:00:00Z http://www.sciforum.net/presentation/620 Among the different forces observed in biological complexes, the cation···p interaction is a strong, non-covalent binding force which participates in a wide variety of processes such as molecular recognition in biological receptors, enzymatic catalysis, etc. The nature and characteristics of this kind of interaction has been mainly theoretically studied in the gas phase, despite being known that the presence of water molecules modulates the strength of the interaction between metal ions and aromatic species. Besides, most studies have employed benzene as a prototype of aromatic unit. On the other hand, an also simple aromatic system as phenol presents two coordination sites for cations: the aromatic ring and the hydroxyl oxygen, thus allowing a greater variety of structures to be formed than in benzene. The hydroxyl group can also be hydrated and participate in the formation of the hydrogen bond network. In the present work, a study of the interaction between cations and phenol has been carried out to shed light on the effect of successive hydration on the interaction. So, ab initio and DFT methods were employed for studying the stepwise microhydration of phenol···cation complexes, locating the most stable structures and obtaining the corresponding complexation energies. The results suggest that the participation of the hydroxyl group is already relevant in clusters containing a small number of water molecules. 2011-10-22 2011-10-22T00:00:00Z http://www.sciforum.net/presentation/630 We have recently reported an experimental and computational study on [1,5]-H shifts in acetal-ketenimines and acetal-carbodiimides in which the acetalic H atom migrates to the central electrophilic carbon atom of the heterocumulenic fragment. These rearrangements occur under unusual mild thermal conditions, and were chemically interpreted as hydride shifts. The resulting intermediates undergo 6π electrocyclic ring closure to give, respectively, quinoline and quinazoline rings. As a continuation we considered the replacement of the ketenimine and carbodiimide functions by cumulene fragments. As expected, the thermal treatment of several acetal-allenes led to 1,2-dihydronaphthalenes by a similar [1,5]-H/6π electrocyclic ring closure tandem process. Next, as we will describe in this communication, we essayed the cyclization of acetal and dithioacetal-allenes, by activating the electron-rich cumulene function with a protic acids Surprisingly, these reactions provided new heterocyclic fused indenes as reaction products. A mechanistic rationale for explaining these results will be also disclosed. 2011-10-22 2011-10-22T00:00:00Z http://www.sciforum.net/presentation/665 Selenium-based reagents bear a high potential for the improvement of known reactions not only from an environmental and pharmaceutical point of view, but also as interesting reagents for the development of, completely new synthetic transformations and as potential ligands in catalytic reactions. A variety of organoselenium compounds have been proven to be useful for organic synthesis over several decades. Organoselenium species can be introduced as either nucleophiles or electrophiles to other organic molecules, producing useful intermediates for organic synthesis. Optically active organoselenium derivatives and their application to highly selective asymmetric synthesis are also of current interest. Probably the most interesting aspect, which emerged in recent years, concerns the possibility of effecting some functional group conversions using catalytic amounts of the selenium reagent or using selenium containing compounds as chiral ligands in metal catalyzed reactions. The developments of all these catalytic processes represent the most important results which have been reported recently in this field and their conceptual and synthetic relevance considerably increases the use of some organoselenium derivatives as Green Catalysts. [1] In consideration that in Nature, the main biological function of selenium is associated with its incorporation in the form of selenocysteine (Sec) into certain proteins having redox motifs different selenium containing compounds can be investigated as bio-inspired catalysts in the carbon-carbon multiple bond oxidation mediated by H2O2 in water. These catalysts resulted to be also interesting good GPx-mimetics. Acknowledgement: Financial support from M.I.U.R.-PRIN2007, Consorzio CINMPIS, Bari, University of Perugia, the grant "British-Italian Partnership" from the British Council/CRUI. References [1] a) D. M. Freudendahl, S. Santoro, S. A. Shahzad, C. Santi, T. Wirth Angew. Chem. Int. Ed.2009, 8, 8409.b) C. Santi, M. Tiecco, L. Testaferri, C. Tomassini, S. Santoro, G. Bizzoca Phosphorus Sulfur Silicon Relat. Elem. 2008,183, 956. c) S. Santoro, C. Santi, M. Sabatini, L. Testaferri, M. Tiecco Adv.Synth. Catal. 2008, 350, 2881. d) S. Santoro, B. Battistelli, B. Gjoka, C-w.S.Si, L.Testaferri, M. Tiecco, C. Santi Synlett, 2010, 1402. 2011-10-20 2011-10-20T00:00:00Z http://www.sciforum.net/presentation/749 Di-substituted silanetellurones, X2Si=Te (X=H, F, Cl, Br, I and CN) are the target of this research. They are organometallic analogues, also known as heavy ketones, and they have recently been of great interest to researchers. Knowledge of the properties of such heavy ketones is important for a better understanding of both the chalcogen and substituent effects. The chemistry of multi-bonded compounds between group 14 and heavier chalcogen atoms has attracted chemists in various fields, as these molecules have proven to be convenient models for studying fundamental chemical problems and valuable intermediate products in synthesis. However, the literature of the mentioned species is limited and this research work endeavors a systematic investigation of these silanetellurones, using theoretical methods. We report the structural and spectroscopic parameters as well as the ionization potentials (IPad and IPad(ZPVE)), the neutral–anion separations (EAad and EAad(ZPVE)), the singlet–triplet splittings, the Kohn-Sham HOMO–LUMO gaps besides the nucleophilicity (N) and global electrophilicity (ω) indices. Since experimental data are still lacking for silanetellurones, the findings of this work would add to the literature, assist experimentalists to generate and further explore these novel species as well as rationalize some reactions pertaining to silanetellurones. 2011-10-20 2011-10-20T00:00:00Z http://www.sciforum.net/presentation/667 The nature of selenium-sulfur non-bonding interactions in a series of substituted benzeneselenenyl derivatives has been investigated by means of computational techniques. The results of these calculations, together with experimental measurements (X-rays crystallography and NMR), suggest that the strength of this interaction increases with the increase of electronegativity of the substituent on selenium. Natural bond orbital (NBO) analysis suggests that this interaction has a mainly covalent character, rather than electrostatic, and originates from an interaction between a lone pair of sulfur and an antibonding orbital on selenium. Atom in molecules (AIM) analysis further supports this finding. 2011-10-20 2011-10-20T00:00:00Z http://www.sciforum.net/presentation/771 The effects of substituent type and position on the aromaticity of certain derivatives of three 1,3- azoles (oxazole, imidazole and thiazole) have been investigated theoretically by using density functional theory at the level of B3LYP/6-31G(d,p) method. The second heteroatom substitution decreased the aromaticities of furan, pyrrole and thiophene. The decreased aromaticity has been found to be gained back to some extent by the substitution of strong electron withdrawing groups or atoms (NO2 and F). NICS data have been considered in order to judge the aromaticities of the systems. The most effective substitution to enhance the aromaticity has beencalculated to be at position- 4. The variation of the bond lengths of the main skeleton supported the findings through NICS calculations. The frontier molecular orbital energies have also been reported to draw a general correlation between these energies and the aromaticity of the system. 2011-10-19 2011-10-19T00:00:00Z http://www.sciforum.net/presentation/674 The authors report on the use of the reaction system BrCCl3/PPh3 in the amidation of carboxylic acids, in the preparation of anhydrides from carboxylic acids and in the esterification of carboxylic acids with cholesterol, where cinnamic acids were used as acid component in all three transformations. Furthermore, the use of BrCCl3/PPh3 in the dehydration of benzcarboxamides to benzonitriles was studied as well as the preparation of N-(phenylsulfonyl)-triphenylphosphoranylideneamide from benzenesulfonamide. 2011-10-17 2011-10-17T00:00:00Z http://www.sciforum.net/presentation/569 Indenoisoquinolinediones, as exemplified by lead compounds indotecan and indimitecan, are a class of non-camptothecin topoisomerase I poisons that display marked cytotoxic properties and for some of them antitumor activities in xenograft models. We have developed two alternative and dramatically different synthetic approaches to a variety of highly fused and diversely substituted models that differ from the elaboration of key precursors, i.e. arylated 2,3-dihydroisoquinolones. The first one is based upon a Suzuki-Miyaura cross-coupling reaction involving enol phosphates combined with a ring-closing metathesis (RCM) reaction to ensure the creation of the six-membered lactam unit. The second approach hinges upon the photoinduced electrocyclization of the 6π electron aromatic enamides. The presence of phenolic methoxy groups precluded an additional mandatory and problematic oxidation step to generate the unsaturated lactam ring. Intramolecular carbocationic annulation reaction and ultimate oxidation of the latent hydroxyl functionality completed the synthesis of the targeted title compounds. 2011-10-17 2011-10-17T00:00:00Z