2-Formamido-3-methylpyrazine

Formylaminopyrazines have been prepared as follows. 2-Amino-3-dimethoxy-methylpyrazine stirred at 0 with acetic formic anhydride gave 2-dimethoxymethyl-3-formamidopyrazine (27) (1075), and 2-amino-3-methylpyrazine similarly treated gave 2-formamido-3-methylpyrazine (1200). 

C yanoethyl)carbamoyl-3-formylamino-5-methylpyrazine boiled with N sodium hydroxide for 30 seconds gave 3-amino-2-cyanoethylcarbamoyl-5-methyl-pyrazine (435) 2,3-dichloro-5-formamido-6-formylpyrazine was readily deformyl-ated under acid or alkaline conditions (e.g., 2A( sodium carbonate at 20°) (430) and 2-formamido-3-(iniidazol-2-yl)pyrazine was deformylated by refluxing with 0.1 A hydrochloric acid for 4 hours and its 5,6-dimethyl derivative reacted similarly (455a). 

The preparation of this ring system involves the use of pyrazine intermediates. The parent heterocycle 3 has been prepared in two different ways from 2-amino-3-methylpyrazine (1). Formylation in a mixture of formic acid and acetic anhydride at 50° gives the formamido derivative 2. This is cyclized by heating with sodium ethoxide at 325° to give... 

Alkaline closures are also possible. 2-Formamido-6-methylpyrazine-3-(JV-methyl)carboxamide gave a good yield of 3,7-dimethylpteridin-4-one when boiled in 0.5 N sodium bicarbonate for 5 min.206 For the less 7r-deficient 4-formamidoimidazole-5-carboxamide, 0.05 N sodium bicarbonate sufficed to produce an excellent yield of hypoxanthine (purin-6-one).204 These alkaline conditions are well tolerated by glycosides. 

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