In situ synthesis of SO3H supported Fe3O4@resorcinol–formaldehyde resin core/shell and its catalytic evaluation towards the synthesis of hexahydroquinoline derivatives in green conditions

Abstract

A novel spherically shaped core@double-shell acidic nanocatalyst (Fe₃O₄@SiO₂@RF–SO₃H) [RF: resorcinol–formaldehyde resin] was prepared in situ and completely characterized using X-ray diffraction, Fourier transform infrared spectroscopy, vibrating sample magnetometry, energy dispersive X-ray spectroscopy, thermogravimetric analysis, transmission electron microscopy and field-emission scanning electron microscopy. The concentration of H⁺ loaded on the Fe₃O₄@SiO₂@RF was reported to be 1.3 mmol g⁻¹. The well-defined Fe₃O₄@SiO₂@RF–SO₃H core–shell heterostructures exhibited high stability, efficient recyclability (10 cycles), and promoted catalytic activity for one-pot condensation reaction between the aromatic aldehydes, dimedone, malononitrile, and ammonium acetate for the synthesis of hexahydroquinoline derivatives.