A series of novel isoxazole, dihydropyrazolone, and tetrahydropyridine derivatives were synthesized by the reaction of corresponding ethyl 1-substituted aryl-2-methyl-4-oxo-1,4,5,6-tetrahydropyridine-3-carboxylates with different hydrazines and hydroxylamine. Reaction of tetrahydropyridone with N,N-dimethylformamide dimethyl acetal provided 1-(5-chloro-2-methylphenyl)-2-[2-(dimethylamino)ethenyl]-4-oxo-1,4,5,6-tetrahydropyridine-3-carboxylate, which was cyclized into a bicyclic compound on treatment with ammonium acetate. The structures of all synthesized compounds were confirmed by IR, 1H NMR, and 13C NMR spectroscopy data. The structure of 5-(5-chloro-2-methylphenyl)-4-methyl-2-phenyl-2,5,6,7-tetrahydro-3H-pyrazolo[4,3-c]pyridin-3-one was unambiguously assigned by means of X-ray analysis data.