Synthese des 4-Hydroxy-6,6-dimethyl-5,6-dihydro-2H-thiopyran-2-thions bzw. -ons und der entsprechenden Tautomeren

The tautomers 4-hydroxy-6,6-dimethyl-5,6-dihydro-2H-thiopyran-2-thione (4 a) and 2-mercapto-6,6-dimethyl-5,6-dihydro-4H-thiopyran-4-one (4 b) resp. were synthesized by hydrolysis of 4-amino-5,6-dihydro-2H-thiopyranthiones6,8. On methylation of4 a,b only the S-methyl product7 is formed. Hydrolysis of 4-amino-2-methylthiothiopyranyliden iodides11 leads—depending on the amino group of11—either to the thiopyranone7 or to the 4-imino-thiopyranes12 and to -amino-,,,-unsaturated-methyldithio carboxylates13. On reaction of4 a,b with hydrogenperoxyd the tautomers 4-hydroxy-5,6-dihydro-2H-thiopyran-2-one5 a and 5,6-dihydro-2H-thiopyran-2,4(3H)diones5 b resp. are formed.4 a,b and5 a,b undergo an aminolysis with prim. and sec. amines to the corresponding 4-amino-2H-thiopyran-2-thiones6,8 and -ones10 resp. On heating in alcohols the 4-alkoxy-thiopyrane-2-thiones and -ones9,14 are formed from4 a,b and5 a,b resp.