Visible Light Promoted Synthesis of Indoles by Single Photosensitizer under Aerobic Conditions

The construction of substituted indole skeletons is always an important concern of synthetic chemists because of its prevalent structure found in natural products and biological molecules. Here, we succeeded in preparing indoles and their derivatives from a wide variety of simple enamines via radical cyclization only with catalytic amounts of an iridium(III) photosensitizer (PS) in DMSO solution under air atmosphere. The mechanistic investigation suggests that the reaction involves a radical course to accomplish the conversion of enamines to indoles under visible light irradiation.