Rhodium-Catalyzed Highly Enantio- and Diastereoselective Alkenylation of β,γ-Unsaturated Butenolides via Dynamic Kinetic Resolution.

Abstract

A rhodium-catalyzed highly enantio- and diastereoselective alkenylation of β,γ-unsaturated butenolides is reported. The use of a chiral diene ligand, (S,S)-Ph-bod, enables the facile synthesis of chiral butyrolactones in high yields with extremely high enantioselectivities (>99% ee in all cases) and high diastereoselectivities (up to >20:1 dr). The key process of the reaction involves the isomerization of β,γ-unsaturated butenolides to racemic α,β-unsaturated butenolides and the subsequent dynamic kinetic resolution through ligand-controlled, enantioselective alkenylation with an alkenylrhodium species that is generated in situ via 1,4-rhodium migration.