2.6- Dimethylpyrazine 1,4-dioxide with acetic anhydride

Variations in the products obtained from the reaction of 2,5-dimethylpyrazine 1,4-dioxide with acetic anhydride by two groups of workers (625, 760) may be explained by procedural differences. 

Other reactions with their counterparts in the pyridine series are also well known. Thus, 2,3-dimethylpyrazine 1,4-dioxide reacts with acetic anhydride to yield 2,3-bis(acetoxy-methyl)pyrazine (S3) in good yield (72KGS1275). Pyrazine 1-oxide also reacts directly with acetic anhydride to yield 2(ljH)-pyrazinone by way of the intermediate acetate (Scheme 22). The corresponding reaction in the quinoxaline series is not so well defined and at least three products result (Scheme 23) (67YZ942). 

Dimethylpyrazine 1-oxide is converted into 2,5-dimethyl-3-propylmercaptopyrazine on treatment with 1-propanethiol and acetic anhydride, and similarly the 1,4-dioxide yields the bisthio ether (206).409... 

Bauer and Hirsch (764) found that 2,5-dimethylpyrazine 1-oxide refiuxed for 2 hours with propane-1-thiol in acetic anhydride gave 2,5-dimethyl-3-propylthio-pyrazine (5), and 2,5-dimethylpyrazine 1,4-dioxide similarly treated gave 2,5-dimethyl-3,6-dipropylthiopyrazine, but attempted reactions with benzenesulfonyl chloride instead of acetic anhydride (as in the pyridine series) were unsuccessful. 

Dimethylamino-23-dimethylpyrazine 1-oxide in boiling acetic anhydride gave 2-acetoxymethyl-3-dimethylamino-5-methylpyrazine (793) which was not isolated but saponified directly to 3-dimethylamino-2-hydroxymethyl-5-methylpyrazine (793). 2-Amino-3-cyano-5-methylpyrazine 1,4-dioxide refluxed with (a) acetic anhydride gave 3-acetamido-2-cyano-5-hydroxy-6-methylpyrazine 1-oxide (532) and (6) sodium methoxide gave 3-amino-2-cyano-5-methoxy-6-methylpyrazine 1-oxide (532). 

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