فهرست نشریات علمی دسترسی آزاد ایران

: In this study, a novel cobalt(II) Schiff base catalyst incorporating a crown ether moiety was synthesized and immobilized onto cellulose nanocrystals (CNC). The structure was characterized by Fourier Transform Infrared spectroscopy )FT-IR(, X-ray Diffraction )XRD(, Scanning Electron Microscopy )SEM(, Energy-Dispersive X-ray spectroscopy (EDX), Transmission Electron Microscopy (TEM), Thermogravimetric Analysis (TGA), Nuclear Magnetic Resonance (NMR) and Inductively Coupled Plasma Mass Spectrometry (ICP-MS), confirming successful anchoring and stability. The resulting hybrid, Crowned Imine-Co(II)@CNC, efficiently catalyzed the synthesis of chromene derivatives via a tandem oxidation–cyclization of benzyl alcohols, malononitrile, and 1,3-diketones under aqueous conditions with molecular oxygen as oxidant. The protocol afforded high yields (up to 99%) in short times and the catalyst was reused for at least five cycles with negligible loss of activity. The crown ether moiety played a key role in oxygen activation and catalyst dispersibility in water. This methodology provides a green and sustainable approach to the synthesis of biologically relevant chromene frameworks.