Chemistry of 5,7-Dihydroxy-2H-thiopyranopyridine-4(3H)-one

Article abstract of DOI:10.1007/BF00799953

Hydrolysis of the 4-alkyliminothiopyrano<2,3-b>pyridinedioles (5) and 4-alkylaminothiopyrano<2,3-b>pyridones (6) resp. with 10 percent NaOH gives 5,7-dihydroxy-2H-thiopyrano<2,3-b>pyridine-4(3H)-one (7). 7 can be obtained in better yield by reaction of 4-dimethylamino-2(1H)-pyridinethione (8) with bis-trichlorphenylethylmalonate (2).Aminolysis of 7 affords the two isomeric products 5 and 6.On treatment with hydrazines, 7 reacts only to 4-hydrazono-derivatives 5.By heating in bromobenzene 5d is cyclized to 1H-5,1,2,6-thiatriaza-acenaphthylen-7-ol (11).On methylation with methyliodide 5, 6 and 7 furnish the 7-methoxyproducts 13, 14 and 12.By heating in 20 percent NaOH 7 is transformed into the 2-thioxo-3-pyridylmethylketone 16A and its tautomer, 2-mercapto-3-pyridylmethylketone 16B.The structures of 5, 6 and 7 are discussed. - keywords: 4-Alkylaminothiopyrano<2,3-b>pyridones; 4-Alkyliminothiopyrano<2,3-b>pyridindioles; 5,7-Dihydroxy-2H-thiopyrano<2,3-b>pyridine-4(3H)-one; 2-Mercapto-3-pyridinylmethylketone; 1H-5,1,2,6-Thiatriaza-acenaphthylene; 2-Thioxo-3-pyridylmethylketone