One-Pot Synthesis of Dihalogenated Ring-Fused Benzimidazolequinones from 3,6-Dimethoxy-2-(cycloamino)anilines Using Hydrogen Peroxide and Hydrohalic Acid

3,6-Dimethoxy-2-(cycloamino)anilines undergo 4- or 6-electron oxidations to afford novel ring-fused halogenated benzimidazoles or benzimidazolequinones using H2O2/HCl or H2O2/HBr. Cl2 and Br2 are capable of the same oxidative transformation to the benzimidazolequinones. Labeling experiments indicate that water is necessary for oxidation of the para-dimethoxybenzenes to the corresponding quinones.