Acid-Catalyzed Regioselective Acylation of α-Silylallylic Sulfides and Its Application to a Novel Cyclopentannelation and Furan Annelation

Abstract

Introduction of a silyl group at the a-position of allylic sulfides, followed by the aluminum chloride-catalyzed reaction of the resulting α-silylallylic sulfides with acid chlorides resulted in regioselective acylation at the γ-position of the allylic system to give γ-acylated vinylic sulfides, chemically equivalent to 1, 4-dicarbonyl compounds. Heating of the products in refluxing benzene with an equimolar amount of p-toluenesulfonic acid produced 2-cyclopentenone derivatives. Treatment of the acylated products with an equimolar amount of concentrated sulfuric acid gave α-phenylthiofuran derivatives. These procedures provide a novel method for cyclopentannelation and furan annelation.