Catalytic Asymmetric Homologation of 4‐Substituted Cyclohexanones with CF3CHN2: 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 (CF3CHN2) 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. α‐Trifluoromethyl cycloheptanones containing the C(sp3)−CF3 bond on the chiral centers were accessed through a highly stereoselective ScIII/chiral bisoxazoline‐catalyzed homologation reaction of cyclic ketones with CF3CHN2 as the trifluoromethylation reagent. This reaction could be applied to construct silicon‐stereogenic centers with moderate diastereoselectivities and high enantioselectivities.