Manganese-catalyzed aerobic dehydrogenative cyclization toward ring-fused indole skeletons.

We describe the first example of manganese(III)-catalyzed aerobic dehydrogenative cyclization producing ring-fused indole skeletons. This catalytic system converts from two C-H bonds of indole and malonate to a C-C bond and produces water as the sole side product. This operationally easy method was extended to an intermolecular cross-dehydrogenative coupling of indole and α-substituted malonate with complete C2-selectivity.