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 and six membered rings. These reactions are cis stereoselective in all cases studied, and appear to proceed via a concerted, pericyclic process. The cycloadditions all generally occur under mild thermal conditions and some involving imino enophiles can also be effected at lower temperatures using Lewis acid catalysis.