Synthesis of butenolides by one-pot cyclization reactions of silyl enol ethers with oxalyl chloride

摘要

Oxalyl chloride represents a versatile C-2 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 gamma-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. 1 Introduction 2 (Trimethylsilyloxy)alkenes 3 1, 1 -Bis(trimethylsilyloxy)ketene Acetals 4 1.3-Bis(trimethylsilyloxy)alk-1-enes 5 1 3-Bis(trimethylsilyloxy)buta-1,3-dienes 5.1 Optimization 5.2 Scope and Limitations 5.3 Synthesis of gamma-Alkylidenetetronic Acids 5.4 Hydrogenation and Kinetic Resolution 5.5 Functionalization by Palladium(0)-Catalyzed Reactions 5.6 Formal Synthesis of Pulvinic Acids and Related Natural Products 5.7 Formal Synthesis of Lucidone and Linderone 5.8 1.3-Bis(trimethylsilyloxy)-1,3,6-heptatrienes and 1,3-Bis(trimethylsilyloxy)-1,3,7-octatrienes 5.9 Synthesis of 5-Alk-ylidene-2,5-dihydropyrrol-2-ones 6 Bis- and Tris(silyloxy)trienes 6.1 1,5-Bis(trimethylsilyloxy)-1,3,5-hexatrienes 6.2 1,3,5-Tris(trimethylsilyloxy)-1,3,5-hexatrienes 6.3 2,4-Bis(trimethylsilyloxy)-1,3,5-hexatrienes 7 Conclusion