Catalytic Asymmetric Homologation of 4-Substituted Cyclohexanones with CF3 CHN2 : Enantioselective Synthesis of α-Trifluoromethyl Cycloheptanones.

Introduction of the trifluoromethyl group (CF3 ) into organic molecules in an enantioselective manner has attracted significant attention, but still remains a challenging problem. We herein report a catalytic asymmetric trifluoromethylation of cyclic ketones via a ScIII /chiral bisoxazoline-catalyzed homologation reaction by employing 2,2,2-trifluorodiazoethane (CF3 CHN2 ) as the CF3 source. This desymmetrization process is highly efficient and generates two chiral centers with excellent diastereoselectivity and enantioselectivity, affording chiral α-trifluoromethyl cyclic ketones in a straightforward manner.