Visible-light-induced radical-cascade alkylation/cyclization of N-methacryloyl-2-phenylbenzimidazole: Access to benzoimidazo[2,1-a]isoquinolin-6(5H)-ones

A metal-free visible-light-induced synthesis of aza-polycyclic aromatic hydrocarbons via cascade alkylation/cyclization of N-methacryloyl-2-phenylbenzimidazole was developed. The reaction was carried out with inactive alkanes and cyclic ethers as alkylation reagents, and phenanthrenequinone (PQ) as a direct hydrogen-atom transfer (HAT) photocatalyst. The desired products were obtained in moderate to good yields at room temperature under air.