Dirhodium(II)-catalyzed enantioselective cyclopropenation of internal alkynes with trifluoromethyl carbene

Abstract

Catalytic enantioselective reactions of trifluoromethyl carbene represent a powerful method for the construction of chiral trifluoromethyl-functionalized molecules, but the utilization of less reactive internal alkynes remains a persistent challenge in this domain. Herein, we report a chiral dirhodium(II) complex-catalyzed enantioselective cyclopropenation reaction of disubstituted alkynes by using 2,2,2-trifluorodiazoethane (CF3CHN2) as the trifluoromethyl carbene precursor. Achiral axial ligation by solvent molecules proves to be a key to improve the reactivity and control the stereoselectivity of metallocarbene species. This transformation provides efficient access to a wide range of enantioenriched trifluoromethyl group-substituted cyclopropenes, cyclopropanes, fused cyclopropane derivatives, and cyclopropyl boronate. The presented methodology constitutes a practical solution to a long-standing hurdle in catalytic enantioselective cyclopropenation of trifluoromethyl carbene with internal alkynes.