Quinoxaline-2-carboxylic acids table

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). 

Quinoxaline-2-carboxylic Acids and Quinoxaline-2,3-dicarboxylic Acids TABLE 2. (.contd.)... 

Another straightforward procedure is described to prepare substituted isoindolo [2,l-a]quinoxalin-6(5//)-ones, which involved the transformation of a substituted 2//-isoindole-l-carboxylic acid into an acid chloride (Scheme 3.90) followed by a coupling reaction with a substituted 2-iodophenylamine and a copper-catalyzed C-N coupling reaction (Table 3.11). 

Elchaninov and Elchaninov 2014) reactions. The formation of 2-(lH-imidazo[4,5-Z7]pyridin-2-yl)-3-arylquinoxahnes 96a-d from pyrido[2,3-fe]pyrazin-2(lfl)-ones 95a-d and 1,2-DAB 5a proceeds in AcOH under reflux for 35-47 h. It should be noted, that carrying out the reaction with refluxed AcOH for 3 h leads to the formation of 2-amino-3-azaanylide quinoxaline 3-phenyl-2-carboxylic acids 97. This has been illustrated by the reaction of 2-(lH-imidazo[4,5-fc]pyridin-2-yl)-3-phenylquinoxahne 95a and 1,2-DAB 5a (Table 6.4) (Mamedov et al. 2010a). 

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