Anchoring Cu (II) on Fe3O4@ SiO2/Schiff base: a green, recyclable, and extremely efficient magnetic nanocatalyst for the synthesis of 2-amino-4H-chromene derivatives

In this work, a novel water-soluble Salen type Cu(II) Schiff base complex functionalized silica-coated magnetite nanoparticles [Fe3O4@SiO2/Schiff base of Cu(II)] was synthesized and characterized. First, an immobilized water-soluble Schiff base was synthesized from the condensation reaction between 3-amino propyl triethoxy silane (APTES) functionalized silica-coated magnetite nanoparticles and a water-soluble aldehyde (sodium salicylaldehyde-5-sulfonate monohydrate). After that, functionalized Schiff base was converted to functionalized Cu(II) Schiff base complex as the result of reaction with Cu(II) acetate tetrahydrate. The structural and magnetic properties of the prepared compounds were identified by FT-IR, XRD, SEM, EDX, TEM, VSM, and TGA. The catalytic activity of the novel nanocatalyst was investigated for the preparation of 2-amino-4H-chromene derivatives through an one-pot, three-component reaction of dimedone, aromatic aldehydes, and malononitrile, in the presence of catalytic amounts of the Fe3O4@SiO2/Schiff base of Cu(II) nanocatalyst in water and at room temperature. The 2-amino-4H-chromene derivatives were obtained in good to excellent yields. Furthermore, because of the solubility of metal Schiff base complexes in water, the nanocatalyst dispersed in water easily without using ultrasonic or shaker.