Additive-and Catalyst-free C3-H Methylation of Quinoxalin-2(1H)-ones with Di-tert-butyl Peroxide

We have developed a C3-selective methylation of quinoxalin-2(1H)-ones employing di-tert-butyl peroxide (DTBP) as a safe and readily handled methylating reagent. This transformation proceeds under catalyst- and additive-free conditions, furnishing a direct and efficient synthetic route to C3-methylated quinoxalin-2(1H)-ones. The synthetic utility of this protocol was further demonstrated by a gram-scale reaction and the methylation of 2H-benzo[b][1,4]oxazin-2-one.