Inorganic-organic hybrid nanomaterial (Fe3O4@SiO2-AQ): A retrievable heterogeneous catalyst for the green synthesis of 4H-chromenes

Preparation of 4-aminiquinaldine grafted on silica-coated nano-Fe3O4 particles (Fe3O4@SiO2-AQ) as a novel retrievable heterogeneous nanocatalyst is described. This novel hybrid nanomaterial was applicated for the green synthesis of substituted 2-amino-4H-chromenes via the one-pot condensation reaction of an aldehyde, malononitrile and α-naphthol/β-naphthol/phenol under solvent-free condition. Eco-friendly method, high yield and purity of the desired products, short reaction time along with the ease of the work-up procedure outlines the advantages of these new methodologies over the earlier ones. Surface and magnetic properties of the core/shell hybrid nanoparticles were characterized via transmission electron microscopy (TEM), scanning electron microscope (SEM), X-ray powder diffraction (XRD), energy-dispersive X-ray spectroscopy (EDS), thermogravimetric analysis (TGA/DTA), and Fourier-transform infrared spectroscopy (FT-IR) techniques. This nanocatalyst can be reused at least six times without considerable loss of its performance.