Stereoselectivity in Phenylselenoetherification of (Z)- and (E)-hex-4-en-ols Facilitated by Pyridine and Some Lewis Acids

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.