Visible-Light-Mediated Cyclization of Intramolecular Electron Donor–Acceptor (EDA) Complexes and Its Application in the Total Synthesis of Corynanthe-Type Alkaloids

A visible-light-driven one-pot decarboxylative cyclization cascade via an intramolecular electron donor–acceptor (EDA) complex is reported. By covalently tethering an indole donor and an NHPI ester acceptor with an alkyl linker, this strategy enables efficient assembly of the signature 6/5/6/6 tetracyclic skeleton of corynanthe-type monoterpene indole alkaloids under mild, metal- and photocatalyst-free neutral conditions. The transformation features a broad substrate scope (22 examples), excellent yields (68–98%), and facile gram-scale scalability. Using this reaction as the key step, we achieved the enantioselective total synthesis of (+)-hirsutinol and (−)-dihydrocorynantheol in 8 linear steps, which represents, to the best of our knowledge, the first application of an intramolecular EDA strategy in the total synthesis of indole alkaloids.