2.6- Diamino-3-chloro-5-methoxycarbonylpyrazine

Although 2,6-diamino-3-chloro-5-methoxycarbonylpyrazine was sufficiently reactive to condense with many guanidines, some aliphatic amines, and hydrazine, it failed to condense with weak nitrogen bases such as 2-hydrazinopyrazine. Owing to interest in analogues of the effective potassium-sparing diuretic 2,6-diamino-3-chloro-5-guanidinocarbonylpyrazine, effort has been directed to the preparation of active esters (1331). 

The brominations of 2-amino-3-carboxypyrazine (804), 2-amino-5-bromo-3-carboxypyrazine (805, 806), and 2-amino-5-bromo-3-methoxycarbonylpyrazine (807) to 2-amino-3,5-dibromopyrazine have been described in Section V.IB (2) nitrations of 2-amino-3-carboxy-5-chloro-6-ethylaminopyrazine to 2-amino-5-chloro-6-ethylamino-3-nitropyrazine (1181) and 2,6-diamino-3,5-dicarboxypyrazine... 

Amino-3-methoxycarbonylpyrazine with urea in the presence of sodium hydride in dimethylformamide at — 15° gave 2-amino-3-ureidocarbonylpyrazine (1152, 1322). The reaction was also applied to the following pyrazines 2-amino-5-chloro-3-methoxy carbonyl (1152) 2,6-diamino-3-chloro-5-methoxycarbonyl (1380) 2-amino-5-chloro-3-methoxycarbonyl-6-methylamino (1380) 2-amino-5-chloro-6-dimethylamino(and other dialkylamino)-3-methoxycarbonyl (1152) and 2-amino-5-chloro-3-methoxycarbonyl-6-methylthio (1152). The preparation of ureidocarbonylpyrazines from A -cyanamides has been described in Section 2C(2)(d). 

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