An Efficient Procedure for the Synthesis of 2-Arylsubstituted Benzimidazoles Catalyzed by Co (II) Immobilized on Fe3O4@SiO2-NH2/EP@SAA as a Recyclable Nanomagnetic Catalyst

Abstract

Fast, simple and high-yield synthesis continues to be a major challenge for synthetic organic chemists. Among nitrogen-containing heterocyclic compounds, 1 the benzimidazole ring is an important pharmacophore for modern drug discovery. 2 Benzimidazoles have significant biological properties including anticancer, 3 anti-HIV, 4 antibacterial, 5 anti-ulcer, 6 anti-tumor 7 and enzyme inhibitory 8 properties. Benzimidazoles are also important intermediates in organic reactions. 9 Due to the importance of benzimidazoles, interest in the synthesis of these compounds has increased. The most common method is the condensation of o -aryldiamines and carbonyl compounds, especially aldehydes; and the wide availability of the latter makes this route particularly attractive for the production of 2-arylsubstituted benzimidazoles. 10 Numerous oxidative and catalytic reagents have been employed in this method, including Oxone, 11 In(OTf) 312 , FeCl 3 (cid:1) 6H 2 O, 13 I 2 /KI/K 2 CO 314 , sulfamic acid, 15 KHSO 416 , TBAF, 17 SBSA, 18 TiCl 3 OTf 19 and VOSO 4 . 20 These catalysts have been useful for their own purposes in facilitating the synthesis of the expected compounds. However, some of these methods have disadvantages such as high reaction temperatures, prolonged reaction times, low yields, expense, complex work-up procedures or toxic solvents. So the discovery of mild