Synthesis of 2-Substituted Indoles through Visible Light-Induced Photocatalytic Cyclizations of Styryl Azides

A visible light-induced photocatalytic intramolecular cyclization of styryl azides has been developed in the presence of the ruthenium complex Ru(bpy)(3)Cl-2 (0.5 mol%) as photocatalyst at room temperature. The present photocatalytic strategy features operational simplicity as well as high functional group tolerance, and provides a facile access to various 2-substituted N-free indoles in good to excellent yields. Importantly, the present process can employ sunlight as the light source to afford the corresponding products without loss of reaction efficiency.