Photoactivation of Electron Donor-Acceptor Complexes via Quinolinium Salts and 4-Carboxamide-1,4-dihydropyridines: Synthesis of N-Heteroaryl-2-carboxamides.

By leveraging Lewis acid coordination to increase the reduction potential of quinoline to facilitate the formation of an electron donor-acceptor (EDA) complex with Hantzsch ester donors, this work establishes a dual function of the quinolinium salts. This dual function involves the initial single-electron transfer (SET) triggering the target C-H amidation and energy transfer for the generation of singlet oxygen to mediate the subsequent oxygenation process. Consequently, this protocol achieves the transformation under mild aerobic conditions, eliminating the requirement for external photosensitizers, metal catalysts, or strong oxidants.