Synthesis of C2-Carbonyl Indoles via Visible Light-Induced Oxidative Cleavage of an Aminomethylene Group

A strategy for photochemical oxidative cleavage of the aminomethylene group at the C2 position of indole was developed to synthesize C2-carbonyl indoles. The reaction was initiated by the photochemical oxidation of N1, followed by a water-assisted concerted H-shift by abstracting hydrogen from aminomethylene. Bromopyridine was discovered to play dual roles as an oxidant for the regeneration of photocatalysts and as an accelerant for the single-electron transfer process.