One-pot multi-component synthesis of five substituted tetrahydropyridine derivatives promoted by a new natural-based biopolymeric catalyst as a green, reusable and eco-friendly heterogeneous catalyst

In this study, a new bio-based supported, green and reusable catalyst was synthesized using magnetized nano walnut shell supported titanium tetrachloride two steps. In the first step, walnut shell nanoparticles as biodegradable polymer was prepared and magnetized to nano-Fe3O4@ walnut shell. Then the resulted core–shell was coordinated to TICl4 and nano-Fe3O4@walnut shell/Ti(IV) was prepared. The catalyst was characterized by different techniques such as; Fourier transform infrared (FT-IR) spectroscopy, X-ray diffraction (XRD) pattern, energy dispersive X-ray (EDX) analysis, scanning electron microscopy (FESEM) image, vibrating sample magnetometer (VSM) curve, and thermogravimetric analysis (TGA/DTG). The catalytic efficiency was also investigated in the synthesis of five substituted tetrahydropyridine derivatives via one-pot multi-component condensation reaction of aromatic aldehydes, aromatic amines and ethyl acetoacetate under solvent-free conditions at 60 °C. The products were confirmed by their melting points, FT-IR and 1H and 13C nuclear magnetic resonance (NMR) spectra. The present procedure offers advantages such as, short reaction time, reusability of the catalyst, clean and fast work-up and simple separation of the catalyst.