A Facile Synthesis of 2-exo-Methylenepenam through Reductive Cyclization of Allenecarboxylates in a Metal Salt/Metal Bimetal Redox System

Tanaka, H.; Kameyama, Y.; Torii, S. Synlett 1992, 878.

Construction of the 2-exo-methylenepenam framework has been performed successfully by reductive cyclization of 2-(4-phenylsulfonylthio-2-oxoazetidin-1-yl)-2,3-butadienoates, derived from penicillin G, in a bismuth(III) chloride/zinc bimetal redox system.