Abstract: Studies on the stereoselective phenylselenoetherification of (Z)- and (E)-hex-4-en-ols is described. (Z)-Alkenol is envisage to facilitate the 5-exo favored cyclization, while (E)-izomer facilitate the 6-endo favored cyclization. Diastereomeric ratio of the cyclic products depends on counterion and reaction temperature. We found that external additives, such as pyridine and some Lewis acids coordinating to the electrophilic species are used to control the course of cyclizations with high degrees of efficiency and improve the level of stereoinduction. The course of cyclization can be directed as desired by the choice of the electrophile and the additives used in the reaction.

Abstract: Enantiomerically pure substituted 1,4-dioxanes have been prepared from vinyl phenyl selenones and the commercially available enantiopure 1,2-diols in the presence of sodium hydride. This simple and novel one step procedure is an example of the Michael initiated ring closure reactions (MIRC) and involves a conjugate addition of the alkoxide anions derived from the 1,2-diols to the vinyl phenyl selenones. The carbanions thus generated then suffer a proton transfer to give the alkoxide ions which effect the intramolecular displacement of the PhSeO2 group affording the substituted 1,4-dioxanes as the result of a ring closure reaction.

Abstract: 3 equivalents of ammonium persulfate in a 3:1 mixture of MeCN and water slowly convert alkynes into the corresponding 1,2-dicarbonyl compounds. The oxidation rate is enhanced by the presence of diphenyl diselenide that form in situ the electrophilic PhSeOSO3H able to promote a "one pot" hydroxyselenenyilation-deselenenylation reaction.