Hypervalent iodine oxidation of benzil-α-arylimino oximes: an efficient synthesis of 2,3-diphenylquinoxaline-1-oxides

A mild and efficient synthetic protocol for the oxidation of benzil-α-arylimino oximes 3 utilizing iodobenzene diacetate (IBD) as an oxidizing agent has been developed. Oximes 3, obtained by the condensation of (E)-benzil monoxime 2 with various appropriately substituted anilines 1, on treatment with iodobenzene diacetate in dichloromethane at room temperature underwent oxidative cyclization to afford 2,3-diphenylquinoxaline-1-oxide 4 in excellent yields.