Iridium-Catalyzed Asymmetric Hydrogenation of α-Substituted α,β-Unsaturated Acyclic Ketones: Enantioselective Total Synthesis of (-)-Mesembrine

A highly efficient asymmetric hydrogenation of alpha-substituted alpha,beta-unsaturated acyclic ketones catalyzed by chiral spiro iridium complexes for the preparation of chiral 2-substituted allylic alcohols has been developed (ee up to 99.7%). This method provides a concise route to (-)-mesembrine (34% yield, 12 steps).