Cobalt-catalyzed cross-dehydrogenative coupling between N-(2-pyridyl) and free indoles for the synthesis of unsymmetrical 2,2′-biindoles

Cobalt-catalyzed cross-dehydrogenative coupling of N-(2-pyridyl) indoles with free indoles for the construction of unsymmetrical 2,2-biindoles with excellent regioselectivity is developed. The broader substrate scope as well as the removable directing group of this strategy allows the synthesis of unsymmetrical 2,2-biindoles to be accessible in organic synthesis.