Iridium-catalyzed asymmetric hydrogenation of α-substituted α,β-unsaturated acyclic ketones: enantioselective total synthesis of (-)-mesembrine.

A highly efficient asymmetric hydrogenation of α-substituted α,β-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).