Pyrazinecarboxylic esters oxidation

Methyl 2-cyano-A-(2-hydroxyimino-4-mcthylvalcryl)glycinatc (46, R = Me) gave methyl 3-amino-5-isobutyl-6-oxo-l, 6-dihdyro-2-pyrazinecarboxylate 4-oxide (47, R = Me) (AcOH, 70°C, 3 h >32%) 337 the ethyl ester (47, R = Et) (>62%) was made similarly.848... 

Most of the usual routes to such aldehydes have been covered already by primary synthesis in Chapters 1 and 2, by oxidation of alkylpyrazines in Section 3.2.4.1, by oxidation of hydroxymethylpyrazines, in Section 5.2.2, and by reduction of pyrazinecarboxylic esters in Section 8.2.2. 

This chapter includes not only nuclear and extranuclear pyrazinecarboxylic acids and anhydrides, but also the related esters, acyl halides, amides, hydrazides, nitriles, aldehydes, ketones, and any of their thio analogues a few rare isothiocyanatopy-razines and pyrazinecarbonitrile oxides are also included. To avoid repetition, interconversions of these pyrazine derivatives are discussed only at the first opportunity for example, the esterification of carboxylic acids is discussed as a reaction of carboxylic acids rather than as a preparative route to carboxylic esters, simply because the section on carboxylic acids precedes that on carboxylic esters. To minimize any confusion, many cross-references have been inserted. 

Nitroaniline, N-00077 Pyrazinecarboxylic acid Me ester, in P-00285 3-Pyridinecarboxamide A-Oxide, in P-00341... 

---