Dioxirane epoxidation of 10-membered-ring stilbene lactams as synthetic precursors to protoberberines

Silylated stilbene lactams 1, prepared by intramolecular addition of an ary l radical to a trimethylsilylacetylene, were converted into protoberberines by dimethyldioxirane (DMD) epoxidation and subsequent acid-catalyzed cycli zation of the epoxysilane with HCl. Treatment of the nonsilylated trans- an d cis-stilbene derivatives with DMD afforded 13-hydroxytetrahydroprotoberbe rines and 13a-hydroxy-13-ketotetrahydroprotoberberines as the main products . Tetrahydroprotoberberines were also obtained in excellent yields by the r eaction of both silylated and nonsilylated lactams with hydriodic acid.