Et3N catalyzed direct α-addition cascade isomerization of deconjugated butenolides with α-ketoesters for the synthesis of α,γ-disubstituted butenolide derivatives

Abstract

The α,γ-disubstituted butenolides are widespread occurrences in numerous pharmacologically active molecules. In this paper, a highly efficient method for the synthesis of α,γ-disubstituted butenolide derivatives via a direct α-addition cascade isomerization of deconjugated butenolides with α-ketoesters using Et3N as catalyst, has been successfully developed. A series of α,γ-disubstituted butenolides have been obtained in up to 97% yield with excellent regioselectivities (up to >19/1 rr). To the best of our knowledge, there is no precedent for the application of deconjugated butenolides in the direct α-addition cascade isomerization to prepare α,γ-disubstituted butenolides to date.