Double Asymmetric Hydrogenation of Linear β,β-Disubstituted α,β-Unsaturated Ketones into γ-Substituted Secondary Alcohols using a Dual Catalytic System

Double asymmetric hydrogenation of linear beta,beta-disubstituted alpha,beta-unsaturated ketones catalyzed by the DM-SEGPHOS/DMAPEN/Ru-II complex with t-C4H9OK afforded the gamma-substituted secondary alcohols in high diastereo-and enantioselectivities. Some mechanistic experiments suggested that two different reactive species, type (I) and (II), were reversibly formed in this catalytic system: Type (I) with the diamine ligand DMAPEN enantioselectively hydrogenated the enones into the chiral allylic alcohols, and type (II) without the diamine ligand diastereoselectively hydrogenated the allylic alcohols into the gamma-substituted secondary alcohols. This dual catalysis protocol was successfully applied to the reaction of a variety of aliphatic-and aromatic-substituted enone substrates.