ChemInform Abstract: Stereoselective Electrophilic Cyclization of Doubly Activated Imines with Allylsilanes and Simple Alkenes.

ChemInform Abstract

The cyclization of the imines (I), which are accessible by condensation of the corresponding amines with diethyl mesoxalate, leads either to the vinyl piperidines (II) or to the cis-anellated lactones (III); the latter are obtained with complete retention of the double bond geometry. The low yield of (IIIb) is caused by additional formation of its N-ethyl derivative in 48% yield which results from alkylation of (IIIb) with ethyl triflate, a by-product in the cyclization process. Cyclization of the imines (IV) or (VII) proceeds with high selectivity to give (V) or (VIII) as major products.