Fe2+ Supported on Hydroxyapatite-core-shell-γ-Fe2O3 Nanoparticles as an Inexpensive and Magnetically-recoverable Catalyst for Rapid Synthesis of Benzimidazoles and Benzoxazole Derivatives

A simple and facile method for the preparation ofFe2+ supported on hydroxyapatite-core-shell-γ-Fe2O3 nanoparticles (γ-Fe2O3@HAp-Fe2+ NPs) as an environmentally friendly and recyclable green catalyst is described and used for the one-pot synthesis of benzimidazoles and benzoxazole derivatives via reactions between aromatic aldehydes and ortho‐phenylenediamine or ortho‐aminophenol in aqueous media conditions at room temperature. This green method offers significant advantages in terms of its simplicity, very low loading of catalyst, high catalytic efficiency, good to excellent product yields, short reaction time, simple experimental and work-up procedure. Also, after the reaction, γ-Fe2O3@HAp-Fe2+ NPs can be easily recovered and reused for at least ten runs. This magnetic nanoparticle was characterized by Fourier transform infrared spectroscopy (FT-IR), X-ray diffraction (XRD), transmission electron microscopy (TEM), scanning electron microscope (SEM) and vibrating sample magnetometry (VSM) spectra.