Chitosan-supported Fe3O4 nanoparticles: a magnetically recyclable heterogeneous nanocatalyst for the syntheses of multifunctional benzimidazoles and benzodiazepines

An environmentally benign and clean biopolymer-based heterogeneous nanocatalyst was prepared and its properties and morphology were characterized using scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDX) and X-ray diffraction (XRD). Then, its catalytic activity was investigated in two important organic reactions. In these reactions, efficient and selective syntheses of 1,2-disubstituted benzimidazole and 1,5-benzodiazepine derivatives were carried out using 1,2-diamines and aldehydes or ketones in the presence of a catalytic amount of magnetically recoverable chitosan-supported iron oxide nanoparticles (Fe3O4/chitosan), as a biodegradable nanocomposite, in ethanol at ambient temperature in high yields. The Fe3O4/chitosan nanocatalyst can be recovered easily and reused without any significant loss of the catalytic activity.