Synthesis of novel benzimidazoles and benzothiazoles via furan‐2‐carboxaldehydes, o‐phenylenediamines, and 2‐aminothiophenol using Cu(II) Schiff‐base@SiO2 as a nanocatalyst

Abstract

2‐(5‐Substituted phenyl)furan‐2‐carboxaldehyde derivatives were prepared by using an efficient copper(II) complex of tetradentate Schiff‐base ligand immobilized onto silica as a heterogeneous nanocatalyst [Cu(II) Schiff‐base@SiO2] (5.0 mol%) using anilines, sodium nitrite, and furan‐2‐carboxaldehyde. Furthermore, attractive di‐heteroaryl benzo‐fused systems such as benzimidazole and benzothiazole derivatives were synthesized using this nanocatalyst (5.0 mol%) via the reaction of o‐phenylenediamines and 2‐aminothiophenol with 2‐(5‐substituted phenyl)furan‐2‐carboxaldehydes in EtOH. The catalyst was characterized by Fourier transform infrared (FT‐IR), field emission scanning electron microscope (FESEM), energy‐dispersive X‐ray spectroscopy (EDX), X‐ray powder diffraction (XRD), and inductively coupled plasma (ICP) techniques. The advantages of the present catalytic system are short reaction times, mild conditions, good to excellent yields, and low amount of nanocatalyst. Moreover, to the best of our knowledge, this is the first time of using the same catalyst in two steps including synthesis of 2‐(5‐substituted phenyl)furan‐2‐carboxaldehyde and benzimidazole or benzothiazole derivatives. In addition, the synthesized catalyst was recycled very well and reused several times without significant loss of its catalytic activity.