Photoredox aerobic oxidative cycliation of N-arylacrylamides with benzylalcohols.

ABSTRACT

While the radical coupling/cyclization of N-arylacrylamides has been well established for the synthesis of functionalized oxindoles, in the present work, a visible-light-induced aerobic oxidative coupling/cyclization reaction of N-arylacrylamides with benzylalcohols has been developed. The combination of LiBr and benzophenone as the additive was found to be highly effective to enhance the catalytic efficacy. This protocol offers a mild alternative access to structurally valuable hydroxyalkyl oxindoles. Mechanistic studies reveal that the bromo radical in situ formed through the photoredox SET process under aerobic conditions enables efficient HAT to generate the key hydroxyalkyl radical intermediate.