From mercaptopyrazines

Hydroxypyrazine with phosphorus pentasulfide in refluxing pyridine for 45 minutes was readily converted to 2-mercaptopyrazine (46%) (55) (its 1-methyl analogue was prepared similarly) (821,1100) and 5-mercapto-2,3-diphenylpyrazine was prepared likewise (834, 1008). 2-Amino-3-mercaptopyrazine was prepared from 2-amino-3-hydroxypyrazine and phosphorus pentasulflde in refluxing 0-picoline(llOl). 

Preparations of mercaptopyrazines from hydroxypyrazines by reaction with phosphorus pentasulfide in boiling pyridine or 3-picoline have been reported in Chapter VI.6B. 

Mercaptopyrazine in aqueous hydrochloric or acetic acids was chlorinated to give the sulfonyl chloride which with excess liquid ammonia gave 2-sulfamoyl-pyrazine (1006, 1153). Direct sulfonation of the pyrazine ring has never been reported (819) but 2-sulfopyrazine (17) has been prepared from 2-chloropyrazine and aqueous sodium sulfite at 150° (819), and from 2-fluoropyrazine and aqueous sodium sulfite at reflux for 2 hours (882, 884). 2-Amino-3-mercaptopyrazine in aqueous sodium hydroxide with concentrated ammonia and sodium hypochlorite has been shown to give 2-amino-3-sulfamoylpyrazine (1101). 

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