Benzo quinoxaline-3-carboxylic acid

The pyrazine ring is stable toward permanganate oxidation, and this explains a variety of pyrazinecarboxylic acids that have been prepared from quinoxalines or benzo-fused quinoxalines. In contrast, alkyl side chains on pyrazines are effectively oxidized by permanganate, selenious acid, selenium dioxide, or dichromate to afford the corresponding carboxylic acids (Section 8.03.7.1). Oxidation of pyrazines with hydrogen peroxide or percarboxylic acids gives pyrazine A -oxides and/or A, A -dioxides (Section 8.03.5.2). 

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). 

Several transformations of 2- and 3-D-arabotetrahydroxybutyl benzo[/]quinoxalines have been reported. Thus oxidation of the 2-tetrahydroxybutyl derivative with hydrogen peroxide in dilute sodium hydroxide gives the 2-carboxylic acid, m.p. 185°, and oxidation with potassium periodate in dilute acetic acid gives the 2-aldehyde,... 

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