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

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.