A highly efficient, green protocol has been developed for the synthesis of various structurally diverse 2,20-arylmethylene bis(3-hydroxy-5,5-dimethyl-2-cyclohexene- 1-one) and 2-substituted-1H-benzimidazole derivatives. The reaction was performed in water under ultrasound irradiation, using BiOCl nanoparticles as a catalyst. The nanocatalyst was found to be reusable for seven subsequent reactions without much loss in activity. Simple methodology with short reaction times and mild reaction conditions with easy work-up procedure are the salient features of this method.