Cu immobilized on MgZnFe2O4 nanoparticles as a green catalyst in the synthesis of mono and bis-polyhydroquinolines

In this study, a green and environmentally friendly catalyst (MgZnFe₂O₄@ZSC-Cu) was synthesized using a simple and clean method. The catalyst was prepared by combining MgZnFe₂O₄ MNPs with Ziziphus spina-christi extract (ZSC) and immobilizing Cu ions on the resulting material. The catalyst was thoroughly characterized using various techniques including Fourier-transform infrared spectroscopy (FT-IR), X-ray diffraction (XRD), Field emission-scanning electron microscopy (FE-SEM), Energy dispersive X-ray analyzer (EDS), Inductively coupled plasma-optical emission spectrometry (ICP-OES), Thermogravimetric (TGA), and Vibrating sample magnetometry (VSM) analyses. The catalytic activity of MgZnFe₂O₄@ZSC-Cu was evaluated in the Hantzsch reaction involving a four-component reaction with ethyl acetoacetate or dimedone/cyclohexane-1,3-dione, various aromatic aldehydes/di-aldehydes, and ammonium acetate. The structure of the newly formed bis compound and polyhydroquinolines was determined using FT-IR, ¹H and ¹³C NMR spectroscopy. This catalyst provides numerous benefits, such as simple separation using a magnet, less reaction times, high product yield, solvent-free conditions, straightforward work-up, and the capability to reuse the catalyst for up to five cycles.