Magnetically Recyclable Ag@Fe2O3 Core-shell Nanostructured Catalyst for One-pot Synthesis of 2-Aryl Benzimidazole and Benzothiazole

Abstract

Nanocatalysts exhibit several applications in the synthesis of many industrially important organic compounds. They manifest extremely fascinating physical and chemical properties which can be exploited in their catalytic applications. A magnetically recyclable Ag@Fe2O3 core-shell structured nanocatalyst was synthesized by a simple sol-gel technique and characterized by x-ray diffraction spectroscopy, field emission scanning electron microscope, high-resolution transmission electron microscopy, fourier transform infrared spectroscopy, vibrating sample magnetometer etc. Nanocatalyst was found to be a highly efficient heterogeneous catalyst for the synthesis of 2-aryl benzimidazoles and benzothiazoles via one-pot condensation of aromatic aldehydes and 1, 2-phenylenediamine, and 2-aminothiophenol. Ag@Fe2O3 nanocatalyst provides rapid conversion of the substrate into the desired product at room temperature within just 5-18 min in the presence of C2H5OH with good to excellent yield. The combination of Ag core with magnetic Fe2O3 shell results in improved efficiency, stability, magnetic recovery, and reusability compare to the individual nanoparticles. The synthetic protocol is featured with high yield, mild conditions, and simple work-up. Magnetic recovery of the catalyst from reaction systems and its reusability for several runs without loss of catalytic activity are additional advantages.