¹³C and ¹⁵N-NMR spectroscopy provides clear evidence that the Schiff bases of 3-hydroxy-4-pyridinecarboxaldehyde exist as a mixture of hydroxyimino and oxoenamino tautomers in acid media. The study of the stabilities of the tautomeric forms has been approached using density functional calculations (B3LYP/6-31G**). The X-ray molecular structure of (E)-4-[(4-bromophenylimino)methyl]-3- hydroxypyridinium tetrafluoroborate has been solved.

A new approach to 1-vinyl isoquinolines and isoindolines using as the key step the acid catalyzed cyclization of allenamides via an acyliminium ion intermediate has been achieved.

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Silica supported 12-tungstophosphoric acid catalyzes efficiently the reaction of o-phenylenediamines with ketones under solvent-free condition to afford the corresponding 1,5-benzodi-azepines in good yields. The catalyst can be recovered by simple filtration and reused.

Synthetic routes to polyhydroxy azepanes from monosaccharides are described. The stereoselective formation of trans epoxyamides and regioselective epoxyde opening led to azido derivatives that could be transformed in azepanic structures. An anomalous result was obtained in the hydrogenation in MeOH with Pd/C of the azido derivative obtained from D-mannose

The method for coupling of haloaryls to polycyclic aryls with zinc dust and (trialkyl)ammonium formate in an inert atmosphere was extended for polycyclic haloaryls.

Reaction of b-halogen-a-tosyl-substituted ureas with enolates of b-oxoesters and 1,3-diketones gives earlier unknown 3-acyl-substituted 5-ureido-4,5-dihydrofurans instead of expected 5-acyl-6-(halogenomethyl)-4-hydroxyhexahydropyrimidin-2-ones.

A series of new functionalised naphtho[2,3-a]phenoxazinium chlorides was synthesised by condensation of 5-ethylamino-2-nitrosophenol hydrochloride with 1-aminoanthracene and its N-substituted derivatives. These cationic dyes showed maximum absorption in the range between 590 and 647 nm and strong fluorescence with maximum emission wavelengths between 630 and 674 nm, as well as high fluorescent quantum yields in ethanol and water at physiological pH.

Two fluorescent functionalised benzo[a]phenoxazinium chlorides were efficiently synthesised by condensation of 5-ethylamino-4-methyl-2-nitrosophenol hydrochloride with the corresponding N-substituted-naphthylamines. In order to evaluate their applicability as covalent probes for biomolecules, these heterocycles were coupled at the C-terminus of N-protected-L-valine through an ester or amide linkage. Studies of their photophysical properties revealed that all compounds absorbed and emitted at longer wavelengths with high fluorescent quantum yields.

Photostability studies of a series of functionalised benzo[a]phenoxazinium chlorides were carried out in ethanol and water at physiological pH, under irradiation at 419 and 350 nm. These compounds showed good to excellent photostability in ethanol and moderate photostability in water in the wavelengths tested.