Synthesis of carbolines by photostimulated cyclization of anilinohalopyridines.

A general synthetic route to prepare all four carboline regioisomers by photostimulated cyclization of anilinohalopyridines is described. The methodology affords various substituted carbolines in good to excellent yields. In the case of α-carbolines, the SRN1 methodology complements previously reported palladium-catalyzed cyclization approaches.