Visible light-induced direct and highly selective C-H functionalization of quinoxalin-2(1H)-one without orientating group

Using eosin Y and KI as photocatalysts to facilitate the conversion of quinoxaline-2(1H)-one and phenylhydrazine hydrochloride compounds into corresponding 3-arylated quinoxaline-2(1H)-one with high selectivity by a one-pot method under air condition, a simple and efficient synthesis method has been developed. The key feature of this protocol is the C3 arylation of quinoxaline-2(1H)-one, which lacks an orientating group and has high C-H selectivity via C-H functionalization mediated by the Minisci reaction. The mechanism study shows that KI synergies with eosin Y to cleave the C-N bond of phenylhydrazine promote the formation of benzene radicals under mild light excitation, and they then react with electron-deficient quinoxalin-2(1H)-one through a radical substitution reaction, providing a simple and effective method for the direct C-H 3-arylation of quinoxalin-2(1H)-one and its derivatives.