Fused 1, 4-dimethoxybenzenes could be oxidized to benzoquinones by either direct oxidation or demethylation-oxidation. The oxidative demethylation of 5, 8-dimethoxy-2- methylquinoline using 1.1 equiv of NBS in aqueous THF and a catalytic amount of H2SO4 at 20° C for 5 min gave 2-methylquinoline-5, 8-dione in 98% yield without bromination. Moreover, we can control either bromination or oxidative demethylation, or both reactions.
