Asymmetric Transfer Hydrogenation of Naphthol and Phenol Derivatives with Cooperative Heterogeneous and Homogeneous Catalysis

Asymmetric hydrogenation of all-carbon aromatics is still a long-standing challenge in the area of asym-metric catalysis. To date, asymmetric (transfer) hy-drogenation of naphthols and phenols remains unexplored. Here, we describe a new strategy for such asymmetric transformation via a bimetallic co-operative heterogeneous and homogeneous cataly-sis. By using HCOONa as the hydrogen source, various naphthols and phenols were partially hydro-genated in HFIP catalyzed by commercial Pd/C cat-alyst to give ketone intermediates. Further adding the second chiral Ru-tethered-TsDPEN catalyst and MeOH realized the asymmetric reduction of the resulting ketones in a one-pot manner, furnishing chiral alcohols with good to excellent enantioselec-tivity (up to 99% ee). The use of HFIP is crucial for suppressing ketone over-reduction via hetero-geneous catalysis. More importantly, tandem asymmetric transfer hydrogenation of naphthols was also achieved by tuning the volume ratio of mixed HFIP/MeOH solvent, affording chiral 1,2,3,4-tetrahyr-onaphthols with excellent enantioselectivity but rel-atively low yield and limited substrate scope.