Intramolecular EDA Complex-Induced Dearomatization/Spirocyclization of Indolyl Propiolamides.

An intramolecular electron donor-acceptor (EDA) complex-induced cascade radical dearomatization/spirocyclization reaction of indolyl propiolamides has been developed under visible light irradiation, affording 3,3-spiroindolenines in good yields. This green strategy was based on the intrinsic reactivity of the EDA complex, which was used to enable efficient electron transfer under mild conditions without an external photocatalyst. The protocol exhibits excellent functional group tolerance and atom economy. Its synthetic utility was demonstrated through a scale-up experiment and product derivatization. Mechanistic studies revealed the involvement of radical intermediates and supported a reaction pathway proceeding via intramolecular electron transfer.