Oxidation of Quinoxalines and Other Fused Pyrazines to Pyrazinecarboxylic Acids

OXIDATION OF QUINOXALINES AND OTHER FUSED PYRAZINES TO PYRAZINECARBOXYLIC ACIDS 

The pyrazine ring is relatively stable to oxidation, and many pyrazine-carboxylic acids have been prepared from quinoxalines, phenazines, and other fused pyrazines by oxidation with potassium permanganate. This reaction has been most used for the oxidation of quinoxalines, for example, 77 - 78. The oxidations are usually carried out with potassium permanganate in alkali (397), but may also be effected without added base (398). Crippa and Perroncito (399) have also used chromic oxide in acetic acid-acetic anhydride to oxidize benzo(/]quinoxalines (79). Pyrazines prepared by this method are summarized in Table 11.9 (397-419). 

PYRAZINECARBOXYLIC ACIDS PREPARED BY THE OXIDATION OF QUINOXALINES, PHENAZINES, AND OTHER FUSED PYRAZINES 

The pyrimidine ring in many pteridines may be cleaved by acid, alkali, and various other nucleophiles to yield pyrazines the severity of the reaction con- 

Details of these ring opening reactions of polycyclic compounds to give pyrazines are given in Table 11.10 (375, 420-463a) and some additional data are recorded in Sections Vl.l A, VIl.lC, and VIIl.lA(l). 

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