Rhodium(III)-Catalyzed Enantioselective Coupling of Indoles and 7-Azabenzonorbornadienes by C-H Activation/Desymmetrization

Chiral rhodium(III) cyclopentadienyl catalysts ((CpRhIII)-Rh-X) play significant roles in asymmetric arene C-H activation. Rh/Ir-catalyzed couplings of arenes and strained rings have been well-studied, but they have been limited to racemic systems. Reported in this work is the (CpRhIII)-Rh-x/AgSbF6-catalyzed enantioselective desymmetrizative C-C coupling of N-pyrimidylindoles and 7-azabenzonorbornadienes with high efficiency and enantioselectivity. The role of AgSbF6 has been established by mechanistic studies. AgSbF6 enhances the catalytic activity by suppressing the C3-H activation of the indoles, activation which would otherwise lead to catalytically inactive species.