N-Heterocyclic Carbene-Catalyzed Aldol-Lactonization of Ketoacids via Dynamic Kinetic Resolution

Abstract

N-Heterocyclic carbene (NHC)-catalyzed enantioselective aldol lactonization of acyclic ketoacids, proceeding via dynamic kinetic resolution, is presented. The carbene generated from the chiral aminoindanol-derived triazolium salt in the presence of LiCl was the key for the success of this transformation. The reaction allowed the diastereoselective and enantioselective synthesis of cyclopentane-fused β-lactones having three contiguous stereocenters. The reaction products are shown to undergo substrate-controlled β-lactone opening in the presence of amines to afford succinimide derivatives with four contiguous stereocenters.