B(C₆F₅)₃-Catalyzed Reductive C-C Bond Cleavage of Bisindolylmethanes

In this study, B(C₆F₅)₃-catalyzed reductive C-C bond cleavage of bisindolylmethanes (BIMs) is reported as an efficient strategy for preparing C3-alkylated indoles. In the presence of silane, B(C₆F₅)₃ selectively activates Csp²-Csp³ bonds of BIMs under mild conditions. Moreover, this sustainable process exhibits a broad substrate scope, highly functional group tolerance, and excellent regioselectivity. Preliminary mechanistic studies disclose that the formation of stabilized ion-pair intermediates is crucial to achieving the desired transformation. Notably, the strategy provides a metal-free alternative to transition metal catalysis, enabling the sustainable synthesis of valuable indole derivatives.