Visible Light Photoredox‐Catalyzed Arylation of Quinoxalin‐2(1H)‐ones with Aryldiazonium Salts

A visible light photoredox‐catalyzed C‐3 arylation of quinoxalin‐2(1H)‐ones with aryldiazonium tetrafluoroborates has been developed. The reaction was effectively accelerated using an inexpensive eosin Y as a photoredox catalyst under visible‐light irradiation without any other metal, oxidant, or additive. This approach offers a facile way to prepare 3‐arylquinoxalin‐2(1H)‐one derivatives with a wide range of functional group tolerance. A novel and environmentally benign process for C‐3 arylation of quinoxalin‐2(1H)‐ones with aryldiazonium salts has been successfully developed. This methodology exploits a commercially available eosin Y as a nontoxic and inexpensive organic photocatalyst. The reactions proceed under mild conditions in moderate to high yields after a short period without any other metal, oxidant, or additive.