Flash Communication: Cobalt-Catalyzed Asymmetric Hydrogenation of a Fluorinated Cyclobutenoic Acid Derivative

An enantioselective hydrogenation of a fluorinated cyclobutenoic acid derivative using both neutral cobalt(II) and cationic, bis(phosphine)-supported cobalt(I) precatalysts has been developed. With 2 mol % of [(( S,S )- Ph BPE)Co(η 6 -PhMe)][BAr F 4 ], complete conversion and >99% ee was obtained at ambient temperature, enabling a route for the preparation of an enantioenriched bis(difluoro)-substituted cyclobutane. Deuterium-labeling studies supported homolytic cleavage of H 2 and established the unsaturated starting material was not isomerized under catalytic hydrogenation conditions.