A highly efficient magnetic solid acid nanocatalyst for the synthesis of new bulky heterocyclic compounds

Abstract

Fe₃O₄ nanoparticles were prepared and coated with 3-aminopropyltriethoxysilane (APTES). The formed amine-surfaced Fe₃O₄@APTES NPs were further chemically modified with maleic anhydride (MAH) to generate Fe₃O₄@APTES·MAH NPs. This catalyst was characterized by FT-IR, X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), thermogravimetric analysis (TG), energy dispersive X-ray analyzer (EDAX), vibrating sample magnetometry (VSM) and the dynamic light scattering (DLS) measurement technique. The catalyst showed high thermal stability and good reusability. Some new bulky heterocyclic compounds such as bis(2,4,5-triarylimidazole), bis(1,4-dihydropyridine), bis(1,8-dioxooctahydroxanthene) and bis(1,8-dioxo-decahydroacridine) derivatives were synthesized using 4,4′-(alkylazanediyl)dibenzaldehyde as substrate and Fe₃O₄@APTES or Fe₃O₄@APTES·MAH as catalyst. The high purity products were isolated and the catalyst was easily separated with a simple work-up with magnetic field and was recycled several times without noticeable loss of reactivity under the described reaction conditions.