Tungstic acid-functionalized Fe3O4@TiO2: preparation, characterization and its application for the synthesis of pyrano[2,3-c]pyrazole derivatives as a reusable magnetic nanocatalyst

Abstract

A new magnetic nanocatalyst based on the immobilization of tungstic acid onto 3-chloropropyl-grafted TiO₂-coated Fe₃O₄ nanoparticles (Fe₃O₄@TiO₂@(CH₂)₃OWO₃H) was prepared, characterized, and applied for the synthesis of pyrano[2,3-c]pyrazole derivatives. The characterization was performed using FT-IR spectroscopy, X-ray diffraction (XRD), scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDS), and vibrating sample magnetometry (VSM) analysis. Pyranopyrazoles were synthesized in the presence of this novel catalyst via a three-component reaction of 3-methyl-1-phenyl-2-pyrazolin-5-one, malononitrile, and aromatic aldehydes with high yields. It is a low cost, nontoxic and thermally stable catalyst, which shows a long life and can be reused for several catalytic cycles without deactivation or selectivity loss.