Synthesis of γ-Carboline Derivatives via the Rh(III)-Catalyzed Regioselective C-H Activation/[4+2] Annulation Cascade.

Transition-metal-catalyzed annulation represents an attractive approach for constructing diverse bioactive molecules while facing challenges like regioselective control. Herein, an efficient assembly of diverse highly functionalized γ-carboline derivatives from 2H-imidazoles and alkynes has been established. This was achieved through a rhodium(III)-catalyzed C-H activation/[4+2] tandem cyclization cascade, facilitating chemo- and regioselective access to γ-carbolines, which exhibit good anticancer activity, in moderate yields.