Methylpyrazine 1-oxides with acetic anhydride

The first studies of the reactions of methylpyrazine A(-oxides with acetic anhydride were carried out by Koelsch and Gumprecht (625). They found that... 

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)]. 

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]

Amino-3-cyano-5-methylpyrazine 1,4-dioxide (91) refluxed for several minutes with acetic anhydride formed 3-acetamido-2-cyano-5-hydroxy-6-methylpyrazine 1-oxide (92) (24%) (532) and 2-acetoxymethyl-5-methylpyrazine 1,4-dioxide refluxed with acetic anhydride afforded a mixture of2,5-di(acetoxymethyl)pyrazine 1-oxide, with some 2,5-diacetoxymethylpyrazine and a monoxide of 2-acetoxy-methyl-5-methylpyrazine (625). 2-Formylpyrazine hydrate 1,4-dioxide with aqueous sodium hydroxide or bicarbonate at < 37° in an unusual reaction gave 3-carboxy-pyrazine 1-oxide mixed with 5 [Pg.188]

Pyrazine 1-oxide, 2-methylpyrazine 4-oxide, and 2,6-dimethyl-pyrazine 4-oxide are unreactive toward acetic anhydride, but 2,5-dimethylpyrazine 1-oxide, 2,6-dimethylpyrazine 1-oxide, and 2,3,5,6-tetramethylpyrazine 1-oxide react to give 2-acetoxymethyl derivatives. The following mechanism (Scheme 44) is consistent with the observation that an acetoxymethyl derivative is only formed when a methyl group is adjacent to the AT-oxide function.407 However, in... 

The reaction of 3-chloro-2-methylpyrazine 1-oxide with glacial acetic acid and acetic anhydride to give (after treatment with aqueous sodium hydroxide) 2-chloro-... 

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