Chemistry of 5-Alkylamino-4H-thiopyranopyridine-4-ones

Article abstract of DOI:10.1007/BF00809378

4-Alkylaminopyridinethiones*HCl (1*HCl) react with bis-trichlorethylmalonate (3) predominantly to 5-alkylamino-4H-thiopyrano<2,3-b>pyridine-4-ones (6).With alcohols in the presence of acids at 25 deg C 6 undergoes an alcoholysis to the corresponding alkyl-3-(2-thioxo-3-pyridyl)propionates (9).On heating in dilute alkali 6 is hydrolysed via 4-alkylamino-2-thioxopyridylpropylketones (11) to the tautomers, 4-hydroxy-2-thioxopyridylpropylketone (12A) and 2-thioxo-3-(1-hydroxybutenyl)-4-piperidon (12B), resp.On refluxing with alkali the ethyl-pyridylpropionate 9a is cyclisized to the 1-alkyl-1,6-naphthyridine-2(1H)-one (4a), but boiling in ethanolic acid hydrolyses 9a via the pyridylpropionic acid 10 to 4-alkyl-aminopyridylpropylketone (11a).The latter can be transformed via the tautomers 12A, B and 2-methylthio-3-pyridylpropylketone (13) to the 4-hydroxy-3-butyrylpyridone (14A) and its tautomer, 3-(1-hydroxy-butenyl)-piperidine-2,4-diones (14B), resp.The structure of 14A, B is established by reaction of 4-isopropylamino-2(1H)-pyridone (2) with butanoylchloride to the 4-isopropylamino-3-butyrypyridone (15) and hydrolysis of 15 to the tautomers 14A, B. - Keywords: 4-Alkylamino-2(1H)pyridinethiones*HCl, reaction with bistrichlorphenyl-ethylmalonate; Alkyl-3(2-thioxo-3-pyridyl)propionates; 4-Hydroxy-3-butyrylpyridone; 4-Hydroxy-2-thioxopyridylpropylketone; Tautomerism