Butane-1-soltunic acid modified starch-coated γ-Fe2O3 magnetic nanoparticles [γ-Fe₂O₃@starch-n-butyl SO₃H] was easily prepared through a ring opening reaction of 1, 4-butane sultone with nano-magnetic γ-Fe2O3@starch. After structural studies, using FT-IR, SEM, XRD, TGA, TEM, EDX, VSM and also pH analysis the efficiency of this reagent in the preparation of tetrahydrobenzimidazo[2,1-b] quinazolin-1(2H)-ones and 2H-indazolo[2,1-b]phthalazine-triones was studied. Operational simpleness, high yields, short reaction times, wide applicability and simple recyclability of the catalyst employing an external magnet are the most important advantages of this methodology.