Synthesis of Indolo[2,3-b]quinolines via a Visible Light-Induced Intramolecular Oxidative Cyclization and Detosylation

A transition metal-free, visible light-induced intramolecular oxidative cylclization-detosylation-aromatization was discovered. This photocatalytic strategy generated potentially bioactive indolo[2,3-b]-quinoline derivatives in up to 97% yield. With a simple setup, this protocol works efficiently under mild conditions. The final products were obtained both in the presence and in the absence of Eosin Y sodium salt, but the reaction efficiency was largely improved with the use of a photosensitizer.