SnCl4-functionalized nano-Fe3O4 encapsulated-silica particles as a novel heterogeneous solid acid for the synthesis of 1,4-dihydropyridine derivatives

Abstract

A novel type of green heterogeneous solid acid was prepared by the immobilization of SnCl₄ on the surface of Fe₃O₄@SiO₂ (Fe₃O₄@SiO₂–SnCl₄) and characterized by Fourier transform-infrared spectroscopy (FT-IR), X-ray diffraction (XRD), vibrating sample magnetometer (VSM), field emission-scanning electron microscopy (FE-SEM), energy dispersive X-ray (EDX) analysis, N₂ adsorption–desorption (BET) study and transmission electron microscopy (TEM). The activity of this solid acid was investigated via the synthesis of 1,4-dihydropyridine derivatives using a three or four component coupling reaction between an aldehyde, 1,3-dicarbonyl compound, and ammonium acetate under ultrasonic irradiation, which yielded excellent results with easy work-up in a short time. 1,4-dihydropyridine derivatives were characterized by FT-IR and ¹HNMR spectroscopy.