Iron-catalyzed one-pot synthesis of benzimidazoles from 2-nitroanilines and benzylic alcohols

We herein report a new efficient method for the synthesis of benzimidazoles with hydrogen transfer procedure. This method involves alcohol oxidation, nitro reduction, condensation and dehydrogenation in a cascade. The iron-catalyzed heterocyclizations from 2-nitroanilines and benzylic alcohols to form benzimidazoles using hydrogen transfer reaction were investigated in this study. In the presence of dppf in toluene at 150°C, various benzimidazoles were obtained in moderate to good yields within 24h. The reaction was proposed to proceed via a cascade of alcohol oxidation, nitro reduction, condensation, and dehydrogenation.