Formation of Bis‐indolylmethanes from Symmetrical Triarylmethanes via Brønsted Acid Catalyzed C−C Bond Breaking Reaction

Abstract

An alternative approach to synthesize bis‐indolylmethanes (BIMs) via a unique p‐toluenesulfonic acid (PTSA) catalyzed dual Csp3−Csp2 bond‐breaking reaction has been reported here. In the reported protocol, 1,3,5‐trimethoxybenzene (TMB), an electron‐rich and sterically bulky arene, acts as a carbon‐based leaving group which can be recovered after the completion of the reaction. In this process, several BIMs of various indole derivatives can be synthesized from symmetrical triarylmethanes (TRAMs) containing bis‐TMB motifs. By modifying the reaction conditions, we could control the sequential bond cleavage of two Csp3−Csp2 bonds in starting TRAM.