Visible‐Light‐Induced Aerobic Intramolecular Cyclization of (2‐Aminophenyl)(1H‐indol‐1‐yl)methanones: Direct Access to Bioactive Tryptanthrin and its Derivatives

Abstract Visible‐light‐induced mild, transition metal, base, and photocatalyst‐free green protocol has been developed for the synthesis of tryptanthrin and its derivatives. The present reaction is compatible with a wide range of substrates with good to high yields. Further, a novel synthetic transformation of tryptanthrin derivatives has been achieved by the decarboxylative addition of cyanoacetic acid for the first time. This reaction proceeds by visible‐light‐induced single electron transfer between the substrate and oxygen, followed by intramolecular cyclization without the use of an external photocatalyst. magnified image