Mechanism and Origin of Enantioselectivity in the Rh_2(OAc)(DPTI)_3-Catalyzed Cyclopropenation of Alkynes

摘要

Tetrabridged dirhodium(II) catalysts effect several valuable reactions of alpha-diazocarbonyl compounds,including C-H and N-H insertions,cyclopropanations of alkenes,and cyclopropenations of alkynes.The conventional mechanism for these reactions involves formation of a rhodium carbenoid followed by direct C-H insertion or cycloaddition of the carbenoid to afford products.It has generally been assumed that the tetrabridged framework is intact in the active rhodium carbenoid,and a considerable body of experimental and theoretical results in the literature has been consistent with this mechanism.