Eco-friendly highly efficient solvent free synthesis of benzimidazole derivatives over sulfonic acid functionalized graphene oxide in ambient condition

Sulfonated graphene oxide (GO-HSO3) heterogeneous catalyst was prepared at molecular level and characterized by using various modern analytic and spectroscopic methods. Using prepared heterogeneous catalyst GO-HSO3, benzimidazole synthesis was carried out by means of reacting diamine and aldehyde at room temperature in solvent free condition. The catalyst GO-HSO3 showed tremendous catalytic activity in selective synthesis of benzimidazole, as a result 100 % conversion of reactants and up to 89.0 % yield of respective benzimidazole was achieved using 0.1 mg of catalyst in very short reaction duration. The GO-HSO3 catalyst was separated from the reaction mixture by simple filtration process at the end of reaction and reused for six successive cycles without noteworthy loss of catalytic activity and selectivity. Key advantageous of this protocol is high yield, low cost, and easy work-up procedure as well as short reaction time and solvent free condition. The present method is found eco-friendly, highly efficient, solvent free, high yielding, and clean method for the synthesis benzimidazole derivatives at room temperature.