Synthesis of Butenolides by One-Pot Cyclization Reactions of Silyl Enol Ethers with Oxalyl Chloride

Abstract

Oxalyl chloride represents a versatile C2 building block for cyclization reactions. A variety of cyclization reactions of oxalyl chloride are known which involve the formation of two carbon-heteroatom bonds. In contrast, one-pot cyclizations of oxalyl derivatives which proceed by formation of at least one carbon-carbon bond are more rare. In recent years, a number of such cyclizations have been developed which rely on the reaction of oxalyl chloride with silyl enol ethers. These reactions allow for an efficient synthesis of various oxygen heterocycles, such as γ-alkylidenebutenolides, maleic anhydrides and isotetronic acids. The cyclization reactions, which involve the formation of a carbon-carbon and a carbon-oxygen bond, generally proceed with excellent regioselectivity.