Preparation of Nitropyrazines

A few nitropyrazines have been prepared by primary synthesis (see Chapters 1 and 2). Other routes to nitropyrazines are illustrated in the following examples  

3-Amino-5,6-dichloro-2-pyrazinecarboxylic acid (1) gave 5,6-dichloro-3-nitro-2-pyrazinamine (2) (H2S04—HN03, 15 — 20°C, 4 h 46% C02 f during the reaction).607,1313 

2-(Thien-2-yl)pyrazine (5) gave a mixture of 2-(5-nitrothien-2-yl)- (6) and 2-(4-nitrothien-2-yl)pyrazine (7) (H2S04—HN03, 70°C, 4 h good yield of mixture).5601134 

Note Pyrazinamines may be converted into the corresponding dimethylsulfimidopyrazines (sometimes called dimethylsulfiliminopyrazines neither name is satisfactory ) as outlined in Section 13.2.5 these derivatives may be oxidized successively to unstable C-nitrosopyrazines and forthwith to nitropyrazines, as illustrated here. 

2-Chloro-5-dimethylsulfimidopyrazine (8, X = Cl) likewise gave 2-chloro-5-ni-tropyrazine (10, X = Cl) (m-ClC6H4C03H, CH2C12, -5 0°C, 40 min then 

Note This reaction has been done in many ways, such as that indicated here. 

Nitration of 2,5-dimethyl-3,6-diphenylpyrazine with nitric-sulfuric acid occurs in the benzene rings to give 2,5-dimethyl-3,6-di-m-nitrophenylpyrazine (191). 

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