A novel Cu(II) nanoparticles anchored on cyanuric chloride-attached magnetic nanocatalyst: A highly stable, recyclable and efficient nanocatalyst for the synthesis of chromene derivatives

A novel core-shell magnetic nanocatalyst, a copper nanocatalyst, Cu(II)-Schiff base-TCT-APTES@SiO2@Fe3O4 was synthesized and used as an environmentally friendly and recyclable nanocatalyst for the synthesis of chromene derivatives by the one-pot three component reaction in ethanol under reflux conditions. [Display omitted] •A novel magnetic Cu(II) complex anchored Schiff base immobilized on magnetic nanocatalyst (Cu(II)-Schiff base-TCT-APTES@SiO2@Fe3O4) nanostructure was synthesized and elucidated by various characterization techniques.•Reactions carried out in ethanol as green solvent.•Low catalyst loading was used in the chromene derivatives.•Atom economy, simple work-up procedure, environmentally friendly, and operational simplicity.•The catalyst can be reused several consecutive cycles and a negligible loss of Cu (0.8% leaching) observed. As a novel core-shell magnetic nanocatalyst, a copper nanocatalyst, Cu(II)-Schiff base-TCT-APTES@SiO2@Fe3O4 was successfully synthesized through the reaction of the cyanuric chloride grafted onto the core-shell magnetic nanocatalyst with Schiff base complex and finally treated with Cu(NO3)2·3H2O. The noteworthy point is that the novel Schiff base separated by employing hydrazine with 2-pyridinecarboxaldehyde was synthesized and purified by a simple washing and identified by FT-IR, 1H NMR and 13C NMR spectrums. The catalyst was studied relying on various techniques and spectroscopic procedures including FT-IR, SEM, TEM, XPS, XRD, VSM, BET, TGA, and ICP analyses. The TEM images indicated that the catalyst was synthesized with an average size of 37–47 nm and a spherical shape. BET analysis showed that our catalyst has been synthesized with mesoporous structure and high surface area (52.55 m2/g). Moreover, the XPS results clearly demonstrated the peak at 937.2 eV and 949.2 eV that was related to the presence of Cu(II) in structure of catalyst. Then, copper nanocatalyst was successfully tested for the one-pot three component reaction of chromene derivatives of various aldehydes, phenols (2-hydroxynaphthalene-1,4-dione, resorcinol and β-naphthol) and malononitrile in ethanol under reflux conditions. All products were obtained in excellent yields for a diverse range of aromatic aldehydes. TON and TOF numbers for the compound 4j with the highest yield were found to be 192 and 581.8 h−1, respectively. Further, the copper catalyst can be reused by external magnetic field over seven times with a negligible loss in activity, show