THERMAL AND LEWIS-ACID CATALYZED INTRAMOLECULAR ENE REACTIONS OF ALLENYLSILANES

Intramolecular ene reactions of allenylsilanes can be effected with a variety of imines, aldehydes and alkenes as enophiles, forming five an d six membered rings. These reactions are cis stereoselective in all c ases studied, and appear to proceed via a concerted, pericyclic proces s. The cycloadditions all generally occur under mild thermal condition s and some involving imino enophiles can also be effected at lower tem peratures using Lewis acid catalysis.