Syntheses of 4-Hydroxy-6,6-dimethyl-5,6-dihydro-2H-thiopyran-2-thione resp. -one and the Corresponding Tautomers

Article abstract of DOI:10.1007/BF00808744

The tautomers 4-hydroxy-6,6-dimethyl-5,6-dihydro-2H-thiopyran-2-thione (4a) and 2-mercapto-6,6-dimethyl-5,6-dihydro-4H-thiopyran-4-one (4b) resp. were synthesized by hydrolysis of 4-amino-5,6-dihydro-2H-thiopyranthiones 6, 8.On methylation of 4a,b only the S-methyl product 7 is formed.Hydrolysis of 4-amino-2-methylthiothiopyranyliden iodides 11 leads - depending on the amino group of 11- either to the thiopyranone 7 or to the 4-imino-thiopyranes 12 and to β-amino-α,β,γ,δ-unsaturated-methyldithio carboxylates 13.On reaction of 4a,b with hydrogenperoxyd the tautomers 4-hydroxy-5,6-dihydro-2H-thiopyran-2-one 5a and 5,6-dihydro-2H-thiopyran-2,4(3H)diones 5b resp. are formed. 4a, b and 5a, b undergo an aminolysis with prim. and sec. amines to the corresponding 4-amino-2H-thiopyran-2-thiones 6, 8 and -ones 10 resp.On heating in alcohols the 4-alkoxy-thiopyrane-2-thiones and -ones 9, 14 are formed from 4 a, b and 5a, b resp. - Keywords: Heterocycles; Keto-enol-tautomerism; Synthesis; 2H-Thiopyrane-2-ones and -2-thiones, 4-alkylamino and 4-alkoxy)