A Magnetic Fe ₃ O ₄ /Modified Bentonite Composite as Recyclable Heterogeneous Catalyst for Synthesizing 2‐Substituted Benzimidazoles

Abstract An efficient and convenient synthesis of 2‐substituted benzimidazoles catalyzed by magnetic Fe 3 O 4 supported by modified bentonite (MB) was developed. Herein, a separable, magnetic catalyst Fe 3 O 4 /MB was successfully prepared on the basis of exploring Fe 3 O 4 synthesis by co‐precipitation method. Fe 3 O 4 was obtained in 96.09 % yield using sweet orange oil as a reducing and protecting agent. The result showed that the sweet orange oil played a crucial role in the preparation of Fe 3 O 4 . Fe 3 O 4 and Fe 3 O 4 /MB were characterized by powder XRD, SEM, EDX, XPS and BET, and were further applied to catalyze the synthesis of 2‐substituted benzimidazoles. The applicability of the substrate was investigated on the basis of optimizing the reaction conditions. As a consequence, 2‐substituted benzimidazoles were obtained in 37.01–91.68 % yield. It suggested that Fe 3 O 4 /MB was an environmentally friendly and low‐cost catalyst possessing good catalytic activity, broader substrate adaptability and excellent recyclability. It is a promising catalyst in industrial production.