Pyrazinethiones and Pyrazinethiols

This section is mainly about tautomeric pyrazinethiones but the meagre available information on nontautomeric pyrazinethiones and pyrazinethiols is also included. 

Aspects of the tautomerism of tautomeric pyrazinethiones have been studied931, 1398,1424 all(j le acute toxicities of 2-mercaptomethylpyrazine and bis(pyrazin-2-yl-methyl) disulfide have been determined.674 1204 

Most tautomeric pyrazinethiones have been made by primary synthesis (see Chapters 1 and 2), thiolysis of halogenopyrazines (see Section 4.2.4), or thiation of tautomeric pyrazinones (see Section 5.1.2.1) a few nontautomeric pyrazinethiones by primary synthesis (see Chapters 1 and 2) or thiation of nontautomeric pyrazinones (see Section 5.4.2) and nearly all extranuclear pyrazinethiols by thiolysis of extranuclear halogenopyrazines (see Section 4.4). Other routes to such pyrazinethiones and pyrazinethiols are illustrated in the following examples  

5-Benzylthio-2(177)-pyrazinone (1) gave 5-thioxo-3,4,5,6-tetrahydro-2(17/)-pyrazinone (3) (Na, liquid NH3, -76°C, 1 h 70%) a small yield of the intermediate 5-mercapto-2( I 7/)-pyrazinone (2) was obtained when the proportion of sodium to substrate was decreased.1565 

5-Bismethylthio-3,6-dihydropyrazine (4) gave 3,6-dihydro-2,5(177,477)-pyra-zinedithione (6) by addition of H2S and subsequent loss of MeSH from the intermediate (5) (H2S [, pyridine-THF, 0°C, 3 h 64%).714 

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The formation of such pyrazines by primary synthesis has been covered in Chapters 1 and 2 the meagre literature on their formation by oxidation of pyrazinethiones or pyrazinethiols is mentioned in Section 6.1.2. 

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