Visible-Light-Mediated Aerobic α-Oxygenation of Tetrahydroisoquinolines and Isoindolines Without External Photocatalysts

A visible-light-mediated strategy for the direct oxygenation of N-substituted tetrahydroisoquinolines and isoindolines to the corresponding benzo-fused lactams under clean conditions without using any external photocatalysts has been developed. The reaction was performed in the presence of a catalytic amount of base and oxygen. Mechanistic studies reveal that the reaction is initiated by the substrates themselves as photosensitizers. Additionally, BHT could be used as a buffer-like additive to improve reaction selectivity and product yield in this photo-oxidation process.