2- Carbamoyl-6-methylpyrazine

Carboxy-5-methylpyazine (9.7 g) in dry dioxan (114 ml) and tributylamine (17.7 ml) was treated with ethyl chloroformate (7.5 ml), keeping the temperature at 0-5°C. After 10 min, dioxan (190 ml) saturated with ammonia was added. The mixture was stirred for 3 h at room temperature, then dioxin was distilled off, and the residue was taken up tin saturated aqueous sodium bicarbonate (20 ml). The mixture was filtered and the product washed with water to give 2-carbamoyl-5-methylpyrazine (9.2 g), melting point 204°-206°C. 

This 2-carbamoyl-5-methylpyrazine (7.0 g) in glacial acetic acid (30 ml) and 35% (w/v) hydrogen peroxide (20 ml) was heated with stirring at 70°C for 7 h. The reaction mixture was cooled, the product which separated was filtered and washed with water to give 2-carbamoyl-5-methylpyrazine-4-oxide (5.5 g), melting point 206°-208°C. 

Carbamoyl-5-methylpyrazine 4-oxide (5.0 g) was added to 10% by weight sodium hydroxide (50 ml) and then refluxed for 30 min. The reaction mixture was acidified with dilute hydrochloric acid and extracted in a continuous extractor with ethyl acetate. The ethyl acetate extract was concentrated to small volume and gave, after filtration 2-carboxy-5-methylpyrazine 4-oxide (3.2 g), melting point 178°-180°C. 

Ethyl 5-bromo-2-pyrazinecarboxylate 2-(2-Ethylbut-1 -enyl)-6-methylpyrazine Ethyl 5-carbamoyl-2-pyrazinecarboxylate Ethyl 5-chloro-2-pyrazinecarboxylate Ethyl 3-cyano-5,6-dimethyl-2-pyrazinecarboximidate Ethyl 3-cyano-5,6-dimethyl-2-pyrazinecarboxylate Ethyl 3,5-diami no-6-chloro-2-pyrazi necarboximidate Ethyl 6-diethylamino-2-pyrazinecarboxylate 2-Ethyl-3,6-diisobutyl-5-methylpyrazine 2-Ethyl-3,6-diisobutylpy razi ne 2-Ethyl-3,6-diisobutylpyrazine 1 -oxide 2-Ethyl-3,6-diisobutylpyrazine 4-oxide 2-Ethyl-3,6-diisopropylpyrazine /V-Ethyl-AyV -dimethyl-3,5-bismethylamino-2,6-pyrazinedicarboxamide Ethyl 3,6-dimethyl-5-oxo-4,5-dihydro-2-pyrazinecarboxylate... 

Amino-2prepared from 2-amino-3-cyanopyrazine 1-oxide by reflux with acetic acid-acetic anhydride followed by ready deacetylation by refluxing in methanol (538), and in a similar manner 3-amino-2-ethoxycarbonyl-5-hydroxypyrazine has been prepared from 2-amino-3-ethoxycarbonylpyrazine 1 -oxide through 3-acetamido-2-ethoxycarbonyl-5 ydroxy-pyrazine (538), and 2-amino-3-carbamoyl-6-hydroxy-5-methylpyrazine from 2-amino-3-cyano-5-methylpyrazine 1-oxide (538). The preparation of 24 ydroxy-6-methoxycarbonylpyrazine (10) has been claimed from 3-methoxycarbonylpyrazine 1-oxide with acetic anhydride followed by hydrolysis (1057) [cf. Nov Cek et al. (839), who claim it to be the 5-isomer, and Foks (744)]. 

Alkoxypyrazine A-oxides may also be prepared by oxidation of the alkoxypyrazine with peroxyacetic acid. In this way the following have been prepared 3-ethoxypyrazine 1-oxide (100°/20h) (978) 3-(trideuteromethoxy)pyrazine 1-oxide (757l9h) (975) 3-ethoxy-2-methylpyrazine 1-oxide (65-75724h) (978) 3-methoxy-2-phenylpyrazine 1-oxide (55720 h) (817) 3-ethoxy-2,5-dimethyl-pyrazine 1-oxide (56716 h) (872) 3-carbamoyl-2-methoxypyrazine 1-oxide (80720h) (881) and 2-cyano-5-ethoxy-3,6-dimethylpyrazine A-oxide (55720h) (288). 

Aminopyrazine jV-oxides may rearrange and acetylate in the presence of acetic anhydride. Thus 2-amino-3with acetic anhydride and acetic acid at reflux for 2 hours gave 3.acetamido-2-carbamoyl-5-hydroxypyrazine (25), 2-amino-3[Pg.216]

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). 

Amides have also been prepared from carboxylic acids as follows a mixture of 2-carboxypyrazine and triethylamine in methylene chloride treated with ethyl chloroformate and then morpholine gave 2-(A-morpholinocarbonyl)pyrazine (1351) 2-carboxy-5(and 6)-methylpyrazine in dioxane with tributylamine and ethyl chloroformate and then treated with ammonia gave 2-carbamoyl-5(and 6)-methylpyrazine (673), and 2-carbamoyl-5(and 6)-ethylpyrazine were prepared... 

Cyanopyrazine 1-oxide and 3-cyanopyrazine 1-oxide each with alkaline 3% hydrogen peroxide at 55° gave 2-carbamoylpyrazine 1-oxide and 3-carbamoyl-pyrazine 1-oxide, respectively (838). 3-Amino-2-cyanopyrazine 1-oxide refluxed with trifluoroacetic anhydride in triHuoroacetic acid for 5 hours gave 3-amino-2-carbamoylpyrazine 1-oxide (538), and 2-amino-3-cyano-5-methylpyrazine 1-oxide with sulfuric acid (d. 1.8) at 100° gave 2-amino-3-carbamoyl-5-methylpyrazine 1-oxide (1255). 2-Amino-6-chloro-3-cyano-5-methylpyrazine 1-oxide with 0.5N sodium hydroxide at room temperature for 48 hours formed a mixture of 2-amino-3-cyano-6-hydroxy-5-methylpyrazine 1-oxide (56%) and 2-amino-3-carbamoyl-6-chloro-5-methylpyrazine 1-oxide (22%)(533). 3-7V-Acetylcarbamoylpyrazine 1-oxide was hydrolyzed by hot 10% sodium hydroxide to 3-carboxypyrazine 1-oxide (1057). 

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