Toluene → 8-Butylamino-6-methylpyrido[2,3-b]pyrazine-7-carboxylic acid, ethyl ester

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Reaction Steps

13.3 g. of 5,6-Diamino-4-butylamino-2-methylpyridine-3-carboxylic acid, ethyl ester (0.05 Mol.) of Example 1 d and 4g. of glyoxal monohydrate, dissolved in 100 ml. of toluene, are refluxed, while the water formed is removed by means of a water separator. After about 3 hours, the reaction is complete and the solution is concentrated. The remaining oily residue is extracted twice with 50 ml. portions of gasoline and addition of activated charcoal. The gasoline extracts are cooled and the crystalline 8-butylamino-6-methylpyrido[2,3-b]pyrazine-7-carboxylic acid, ethyl ester is filtered off, yield 70%; m.p. 56°-58°.

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