NHC-Catalyzed Organocatalytic Asymmetric Approach to 2,2-Disubstituted Benzofuran-3(2H)-ones Containing Fully Substituted Quaternary Stereogenic Center

Abstract

A highly efficient and enantioselective approach to the synthesis of functionalized benzofuran-3(2H)-ones is presented. It proceeds via an intramolecular Stetter reaction using β,β-disubstituted Michael acceptors in the construction of five-membered rings with fully-substituted quaternary stereogenic centers and is promoted by terpene-derived triazolium salts. As a result, a series of chiral 2,2-disubstituted benzofuran-3(2H)-one derivatives with linear, branched, and cyclic aliphatic substitutions on the quaternary stereogenic center were obtained in high yields and with excellent enantioselectivities of up to 99% ee.