Synthesis of benzimidazole derivatives using Ni2+ supported on hydroxyapatite-core@shell γ-Fe2O3 nanoparticles both under solvent and solvent-free conditions

Ni2+ supported on hydroxyapatite-core@shell γ-Fe2O3 nanoparticles (γ-Fe2O3@HAp-Ni2+) was found to be a useful catalyst for the synthesis of benzimidazole derivatives from o-phenylenediamine and aldehydes under solvent and solvent-free conditions at 80 °C. This reaction affords the corresponding benzimidazole derivatives compared with the classical reactions this method consistently gives a high yield, easy magnetic separation, a short reaction time, simple workup and recyclable property of the catalyst. In this way, the catalyst was readily recovered using an external magnet and could be reused in five consecutive runs without significant loss of reactivity. The mean size and the surface morphology of the nanocatalyst were characterized by TEM, SEM, VSM, XRD and FTIR techniques.