Direct synthesis of 2-substituted benzimidazoles via dehydrogenative coupling of aromatic-diamine and primary alcohol catalyzed by Co Complex

A Co (II) complex with stable structure was designed and synthesized with quinalic acid and Co (OAc)2.4H2O. The single crystal structure of complex was characterized by X-ray diffraction. A dehydrogenative coupling of aromatic diamines and primary alcohols was developed by using the Co (II) complex as the catalyst to synthesize 2-substituted benzimidazole. A series of 2-substituted benzimidazole were obtained with good to excellent yields under mild reaction conditions. In addition, a compound with inhibit Parkinson's activity was synthesized on the gram-scale by using the method. Finally, the reaction mechanism was proposed and the energy changes in the reaction process were simulated by density functional theory (DFT).