Silica-modified magnetite Fe3O4 nanoparticles grafted with sulfamic acid functional groups: an efficient heterogeneous catalyst for the synthesis of 3,4-dihydropyrimidin-2(1H)-one and tetrahydrobenzo[b]pyran derivatives

Silica-modified magnetite-polyoxometalates functionalized with sulfamic acid groups as hybrid nanoparticles were prepared by sulfonation of diamine-functionalized propyl group grafted on the magnetic silica-coated Fe₃O₄ nanoparticles. This heterogeneous nanocatalyst was explored to present high catalytic performance for the synthesis of 3,4-dihydropyrimidinones and tetrahydrobenzo[b]pyrans under mild reaction conditions. The properties of this nanocatalyst were characterized by FT- infrared, energy-dispersive X-ray spectrum, scanning electron microscope, X-ray diffraction, X-ray fluorescence and elemental analysis. Easy separation of the nanocatalyst by using an external magnet, recyclability, non-toxicity, versatility and high stability of the catalyst combined with low reaction times and excellent yields make the present protocol very useful and attractive for the synthesis of the titled products.