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 γ-Fe2O3@KSF-catalyzed multicomponent coupling reaction of 2-aminobenzimidazole, benzaldehydes and dimedone in solvent-free conditions are reported. γ-Fe2O3@KSF as a magnetic catalyst was prepared using the successive coating of γ-Fe2O3 shell on 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 easy workup technique. The tetrahydrobenzimidazo[2,1-b]quinazolin-1(2H)-ones were prepared in yields of 88–94%. The catalyst recovered through an external magnet and reused four times without any considerable loss of its activity.