Highly effective synthesis of 1-thioamidoalkyl-2-naphthols and tetrahydropyridines using a nanostructured silica-based catalyst under mild conditions

Abstract

Nano-2-[N',N'-dimethyl-N'-(silica-n-propyl)ethanaminium chloride]- N,N-dimethylaminium bisulfate (nano-[DSPECDA][HSO4]) was used as a highly effective and heterogeneous silica-based nanostructured catalyst for the synthesis of 1-thioamidoalkyl-2-- naphthols and substituted tetrahydropyridines. The expected products were prepared in mild conditions. In this work, three novel 1-thioamidoalkyl-2-naphthols and two new tetrahydropyridine derivatives were synthesized and characterized by IR, 1H and 13C NMR and Mass spectroscopy. One-pot multi-component condensation of 2-naphthol with arylaldehydes and thioacetamide catalyzed by nano-[DSPECDA][HSO4] under green, mild and solvent-free conditions led to 1-thioamidoalkyl-2-naphthols in high yields. The nanocatalyst was also used for the preparation of functionalized tetrahydropyridines by the one-pot multi-component reaction of anilines, arylaldehydes and ethylacetoacetate under solvent-free and mild conditions. The reaction results were found to be better compared to the literature in terms of one or more of these factors: yield, time, and the reaction media. All the products were purified by recrystallization from EtOH, and without column chromatography, being in good agreement with the green chemistry protocols.