BF3-functionalized silica-coated magnetic nanoparticles as a novel heterogeneous solid acid for synthesis of formazan derivatives via a green protocol

Article abstract of DOI:10.1246/bcsj.20140298

A new type of green heterogeneous solid acid was prepared by the immobilization of BF₃·Et₂O on the surface of Fe₃O₄@SiO₂ core-shell nanocomposite (Fe₃O₄@SiO₂-BF₃) and characterized by Fourier transform infrared spectroscopy (FT-IR), X-ray diffraction (XRD), vibrating sample magnetometer (VSM), field emission scanning electron microscope (FE-SEM), energy-dispersive X-ray (EDS), and transmission electron microscope (TEM). The activity of this super solid acid was probed through the synthesis of aryl diazonium salts as the starting reactant and then, their diazo coupling with aldehyde phenylhydrazones for formation of formazan derivatives in a solvent-free medium at room temperature. This clean and environmentally benign methodology has advantages such as: no need for corrosive and toxic liquid acids, solvents, or buffer solutions, room temperature reaction, high yields, and short reaction times. In addition, long-term stability of aryl diazonium salts supported on the surface of Fe₃O₄@SiO₂-BF₃ magnetic nanoparticles (MNPs) at room temperature was one of the most important results of this procedure.