An efficient and one-pot green synthesis of 2-arylsubstituted benzimidazoles catalyzed by nano-Fe3O4@silica sulfuric acid as a recyclable nanomagnetic solid acid catalyst

An efficient and green protocol for the synthesis of 2-arylsubstituted benzimidazoles via a condensation reaction of aromatic aldehydes and 1,2-phenylenediamine using nano-Fe3O4@SiO2-SO3H as a solid acid catalyst in ethanol under reflux conditions has been described. The reactions are completed in short times, and the corresponding benzimidazoles are produced with high yields. The present procedure has several advantages, including short reaction times, high yields of products, facile experiment, simple work-up, eco-friendly reaction conditions, and reusability of the catalyst. The catalyst could simply be separated and recovered by an external magnet and reused several times without appreciable loss of catalytic activity.