Cobalt-Catalyzed C-H Thiolation through Dehydrogenative Cross-Coupling

A cobalt-catalyzed dehydrogenative cross-coupling of thiols and indoles is reported. Using a cooperative reaction system, a new mode of action for the cobalt-catalyzed C-heteroatom bond formation was found. The directed C-H activation catalysis overrides an undirected thiolation of indole in the 3-position that occurs in the absence of cobalt. Mechanistic studies indicate a sequence of C-H activation, thiolate transfer, and reductive elimination.