Visible-Light-Promoted and EDA Complex-Driven [4 + 2] Annulation for the Construction of Naphtho[1',2':4,5]imidazo[1,2- a ]pyridines.

A green visible-light-promoted and electron donor-acceptor (EDA) complex-driven synthetic strategy for the construction of value-added naphtho[1',2':4,5]imidazo[1,2- a ]pyridines from 2-arylimidazo[1,2- a ]pyridines with Z -α-bromocinnamaldehydes has been accomplished under photocatalyst- and transition-metal-free conditions. This efficient annulation approach provides a new and straightforward pathway for the annulative π-extension of imidazo[1,2- a ]pyridine-based aromatics. Moreover, the sustainable methodology exhibits simple operation, a wide range of substrates, benign conditions, and good functional group compatibility.