Unexpected Transformation of Ethyl 1-(4-Chlorophenyl)-2-Methyl-4-Oxo-1,4,5,6-Tetrahydropyridine-3-Carboxylate and Antibacterial Activity of the Products

The cyclization reaction of N-(4-chlorophenyl)-β-alanine, in the presence of piperidine as a catalyst, provided ethyl 1-(4-chlorophenyl)-2-methyl-4-oxo-1,4,5,6-tetrahydropyridine-3-carboxylate, which reactions with different hydrazines were carried out resulting in formation of a variety of tetrahydropyridine, dihydropyrazolone, and oxazole derivatives in good yields. 5-[2-[(4-Chlorophenyl)amino]ethyl]-4-(1-hydrazinylethylidene)-2,4-dihydro-3H-pyrazol-3-one was converted into a series of hydrazones, which provided tetrahydro-3H-pyrazolo[4,3-c]pyridin-3-one under treatment with acids. The structures of all synthesized compounds were confirmed by IR, 1H NMR, and 13C NMR spectroscopy. The structures of three compounds were unambiguously assigned by means of X-ray analysis data. Some of the synthesized compounds exhibited weak antibacterial activity