Visible-Light-Promoted [5 + 1] Annulation Initiated by Electron-Donor-Acceptor Complexes: Synthesis of Perfluoroalkyl- s-Triazines.

A visible-light-promoted electron-donor-acceptor (EDA) complex-initiated [5 + 1] annulation between biguanides and perfluoroalkyl halides for the construction of perfluoroalkyl- s-triazines has been developed. It was found that both visible light and dioxygen in the air are favorable for the reaction. A radical-polar crossover mechanism was proposed, in which sequential SET, radical combination, HF elimination, electrocyclization, and aromatization are involved.