SnCl4/c-Al2O3 nanoparticles: A reusable and green heterogeneous catalyst for the one-pot synthesis of tetrahydropyridines

Abstract

Nano-SnCl4/c-Al2O3 as a reusable and green heterogeneous catalyst was prepared by the reaction of tin tetrachloride with c-alumina. This solid acid catalyst was characterized by fourier transform-infrared spectroscopy (FT-IR), X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM), transmission electron microscopy (TEM), energy-dispersive X-ray spectroscopy (EDS), thermal gravimetric analysis (TGA) and Brunauer-Emmett-Teller (BET) analyses. Tetrahydropyridines were synthesized via the one-pot reaction of 4-substitutd anilines, ethylacetoacetate and 4-substituted aldehydes in the presence of optimized amount (0.06 g) of nanoSnCl4/c-Al2O3 under thermal conditions (70 C) in ethanol as a green solvent. The process had short reaction times (5–8 h), good to excellent yields (80–93%), simple work-up and easy purification technique (recrystallization through the hot ethanol). It was found that the catalyst could be reused for three times without any considerable loss of its activity.