Syntheses of 1-Substituted 4-Amino-2(1H)-pyridinethione by Dimroth-Reaction of 2,4-Diaminothiopyranylium Halogenides

Article abstract of DOI:10.1007/BF00798613

4-Amino-2-alkylimino-2H-thiopyranes (5) and 4-amino-2-alkylaminothiopyranylium halogenides (4) resp. on heating in refluxing D M F A are rearranged in the presence of Na-ethylate to 1-alkyl-4-aminodihydro-2(1H)-pyridinethiones (2).Also 2-methylthiothiopyranylidenammonium iodides (6) and 2-methylthio-4H-thiopyrane-4-one (7) can be transformed into 1-substituted 2(1H)-pyridinethiones (2) by heating in prim. amines.On treatment with alkali, 4-dimethylaminothiopyranylium iodide (4a) is transformed into its base 5a and hydrolyzed to 8. 5a and 8 are rearranged to the pyridinethiones 2a and the tautomers 9 A, B.The structure of the rearranged pyridinethiones 2 was proved by the 1-phenylderivate 2a.Thus 4-methyl-3-penten-2-on reacts with phenylthiourea via the phenylimino-1,3-thiazine (14) to give 3-phenyl-2(1H)pyridinethione (15). 15 is transformed by the methylpyrimidine-pyridine-rearrangement to the 1-phenylpyridinethione 2a.The mechanism of the Dimroth-reaction of 2-alkylimino-2H-thiopyranes (5) and the stereochemistry of the 1-benzyl-6-phenyl-2(1H)-pyridinethiones 2 are discussed. - Keywords: Conformational analysis of benzyl phenyl 2(1H) pyridinethiones; Dimroth-reaction; Keto-enol-tautomerism of 1-substituted 4-hydroxy-2(1H)-pyridinethiones; 2-Methylthiothiopyranylidenammonium iodides and 2-methylthio-4H-thiopyrane-4-one, reaction with primary amines