Preparation of New Nitrogen-Bridged Heterocycles. XXXIII. A New Preparative Method for Thieno[3, 2-α]indolizines

Abstract

The treatment of 2-iminothieno[3, 2-α]indolizine derivatives with potassium tert-butoxide generated exclusively potassium 1-(2-cyanovinyl)indolizine-2-thiolates through the ring opening of the initially formed thiin-2-imide ions. These 2-indolizinethiolates reacted with various alkylating agents to give the corresponding S-alkylated 1-vinylindolizine derivatives, and 2-acetonylthio- and 2-phenacylthio-1-(2-cyanovinyl)indolizines of these products smoothly underwent intramolecular Michael addition under the conditions employed here to afford the corresponding 2-acetyl- and 2-aroylthieno[3, 2-α]indolizines in high yields with the elimination of a methylene compound.