Co(III)-Catalyzed C-H Activation: A Site-Selective Conjugate Addition of Maleimide to Indole at the C-2 Position.

The cobalt(III)-catalyzed site-selective C-2 functionalization of indole has been developed using the pyrimidinyl group as a directing group. This reaction furnishes 3-arylated succinimide derivatives in excellent yields in a shorter duration using an inexpensive Co catalyst. Highly selective C-2 functionalization of indoles was achieved in the presence of the highly reactive C-3 position. This protocol is compatible with a variety of -pyrimidinyl indole and maleimide derivatives, and it can be easily scaled-up. This method is also applicable for maleic ester and heteroarenes.