Regioselective bromination of quinoxalin-2(1H)-ones with KBr and K2S2O8.

A facile and regioselective C7-bromination of quinoxalin-2(1H)-ones has been developed by employing inexpensive inorganic potassium bromide (KBr) as the bromine source and potassium persulfate (K2S2O8) as an oxidant under mild heating conditions without transition-metal catalysts. Moreover, the transformation is also applicable to other related nitrogen-containing heterocyclic skeletons such as benzooxazinones and pyrimidinediones. This cost-effective and operationally simple bromination strategy provides a convenient route to access C7-brominated quinoxalin-2(1H)-one building blocks for subsequent synthetic derivatization.