Electron Transfer Photoredox Catalysis: Intramolecular Radical Addition to Indoles and Pyrroles

The utilization of the photoredox catalyst, tris(2,2′-bipyridyl)ruthenium dichloride, and a household light bulb to effect radical cyclizations onto indoles and pyrroles at room temperature is reported. A reactive free radical intermediate is generated via the reduction of an activated C−Br bond by the single electron reductant, Ru(I), generated in a visible light induced photocatalytic cycle. This system represents an expansion of the application of photoredox catalysis in conventional free radical processes.