SYNTHESIS AND REACTIONS OF 2-MERCAPTO-6-T HIOXO-THIOPYRAN-3-CARBOXYLATE DERIVATIVES

6-Amino-thiopyran-2-thiones (1) react with dihydrogen sulfide in the p resence of pyridine and triethyl amine to yield 6-thioxo-thiopyran-2-t hiolates (2). Methylation of 2 gives the methylthio compounds 3 and 4. Further methylation of 3a and 4a yields the thiapyrylium salt (7). Th e reaction of 2-imino-thiopyran (6) with carbon disulfide represents a nother route to the 6-methylthio-thiopyran-2-thione (4a). The 2-methyl thio-thiopyran-6-thione (3a) undergoes substitution of the methylthio group with amines to 8 or reacts with phenylhydrazine to phenylhydrazo no-thiopyrane (9c). 6-Thioxo-thiophen-2-thiolates (2a,b) react with hy drazine hydrate to give hydrazono-thiopyranes (10a,b) which can be S-m ethylated. On the contrary 2c gives with hydrazine hydrate under ring transformation the pyridine-2-thiolate (11). N,S-Acetals (12) and 1,3, 4-thiadiazoles (15), which give rise to new pyridine derivatives (14) and (17), can be obtained from 1-Amino-pyridin-2-thiolate (11).