Preparation and application of ZnFe2O4@SiO2-SO3H, as a novel heterogeneous acidic magnetic nanocatalyst for the synthesis of tetrahydrobenzo[b]pyran and 2,3-dihydroquinazolin-4(1H)-one derivative

In this work, we report the synthesis and identification of ZnFe2O4@SiO2-SO3H as a novel and green nanomagnetic solid acid catalyst, which is containing the sulfuric acid catalytic sites on the surface of ZnFe2O4 magnetic nanoparticles as the catalytic support. The as-synthesized ZnFe2O4@SiO2-SO3H MNPs were characterized with accuracy by different physicochemical methods; including, X-ray powder diffraction, energy-dispersive spectroscopy, Scanning electron microscopy, Fourier transform infrared, X-ray elemental mapping, Thermogravimetric analysis, and Vibrating Sample Magnetometer analyses. The catalytic activity of this nanomagnetic material is considered for the synthesis of the diversely substituted tetrahydrobenzo[b]pyran and DHQZ (2,3-dihydroquinazolin-4(1H)-ones) in ethanol solvent, which affording excellent yields (86-97%). The heterogeneous nature of the catalyst was confirmed via the hot filtration experiment. Furthermore, the activity of the recycled nanocatalyst was examined for at least five cycles with a negligible loss of its activity (97-92%). Also, the amount of sulfamic acid function in the ZnFe2O4@SiO2-SO3H was calculated from back titration.