Green preparation of tetrahydrobenzimidazo[2,1-b]quinazolin-1(2H)-ones using γ-Fe2O3@ KSF as novel and recyclable magnetic catalyst

The preparation of tetrahydrobenzimidazo[2,1-b]quinazolin-1(2H)-ones via a γ-Fe2O3@KSF-catalyzed multicomponent coupling reaction of 2-aminobenzimidazole, benzaldehydes, and dimedone in solvent-free conditions is reported. γ-Fe2O3@ KSF as a magnetic catalyst was prepared using the successive coating of a γ-Fe2O3 shell on a KSF core and was characterized by different methods including FT-IR, XRD, TGA and SEM techniques. The merits of this method include limited use of organic solvents, excellent purity of products, and an easy workup technique. The tetrahydrobenzimidazo[2,1-b]quinazolin-1(2H)-ones were prepared in yields of 88- 94%. The catalyst was recovered through an external magnet and reused four times without any considerable loss of its activity.