Synthesis of Benzimidazol-2-ones by Oxidative Cyclization Ring Closure of Amido-Urea Precursors

We describe herein the synthesis of novel benzimidazol-2-ones by oxidative cyclization of amido-urea precursors, using bis(acetoxy)iodobenzene. The role of the oxidative reagent and the formation of the benzimidazol-2-one products were demonstrated and supported by X-ray diffraction. Optimization of the reaction conditions was performed, and the generality of the reaction was shown. The reaction scope was found to be limited to amino-urea substrates bearing a C(sp3) atom adjacent to the amide carbonyl group. A mechanistic pathway involving a Hofmann rearrangement was proposed.