3 years ago

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 β,β-Disubstituted α,β-Unsaturated Ketones into γ-Substituted Secondary Alcohols using a Dual Catalytic System
Hironori Satoh, Ryo Komatsu, Takeshi Ohkuma, Noriyoshi Arai
Double asymmetric hydrogenation of linear β,β-disubstituted α,β-unsaturated ketones catalyzed by the DM-SEGPHOS/DMAPEN/RuII complex with t-C4H9OK afforded the γ-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 γ-substituted secondary alcohols. This dual catalysis protocol was successfully applied to the reaction of a variety of aliphatic- and aromatic-substituted enone substrates. A dual asymmetric catalyst system realizes double hydrogenation of linear β,β-disubstituted α,β-unsaturated ketones into γ-substituted secondary alcohols with high diastereo- and enantioselectivities. The Ru catalyst with a diamine ligand hydrogenates the enones to the allylic alcohols exclusively, and then the reversibly formed catalyst without diamine selectively reduces the allylic alcohols to the saturated alcohols.

Publisher URL: http://onlinelibrary.wiley.com/resolve/doi

DOI: 10.1002/chem.201701527

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