By Oxidation of Aminopyrazines

2-Aminopyrazine was oxidized by hydrogen peroxide in acetic acid at 20° to 3-aminopyrazine 1 -oxide and at 50° for 15 hours to 2-aininopyrazine 1,4-dioxide (51%) (also obtained by similar oxidation of 3-aminopyrazine 1-oxide) (1189). m-Chloroperoxybenzoic acid was also used for the oxidation of 2-aminopyrazine to its 1-oxide (1258). The following aminopyrazine TV-oxides have been prepared by oxidation (reagent and conditions) 2-amino-3-methoxycarbonylpyrazine 1-oxide (m-chloroperoxybenzoic acid in chloroform at reflux) (880, 1222) 2-amino-5-chloro-3-methoxycarbonyl(and methylcarbamoyl)pyrazine 1-oxide (m-chloroperoxybenzoic acid in chloroform at reflux) (1222) 2-amino-5-bromo-3-methoxycarbonylpyrazine 1-oxide (w hloroperoxybenzoic acid in chloroform at reflux) (878, 879, 1222) 2-amino-3-chloropyrazine 1-oxide (peroxyacetic acid) (906) 2-amino-3-bromo-5,6-dimethylpyrazine 1-oxide (peroxyacetic acid) (907) and 2,3-bis(pyridin-2 -yl)pyrazine 1,4-dioxide (hydrogen peroxide in sulfuric acid at room temperature) (754). 

Further preparations were the oxidation of 2-methyl-3-piperidinopyrazine with hydrogen peroxide in acetic or formic acid to 3-methyl-2-piperidinopyrazine 1-oxide and 2-(7V -hydroxy-7V -piperidinio)-3-methylpyrazine hydroxide (51) [which was dehydrated by sublimation to 2-methyl-3-(A -piperidino-7V -oxide)pyrazine 

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