By Oxidation of Alkyl-, Styryl-, Hydroxyalkyl-, and Fused Pyrazine Systems

The oxidation of alkyl-, styryl-, and hydroxyalkylpyrazines to carboxypyrazines mostly with potassium permanganate in aqueous solution but also with selenious acid in pyridine (669), selenium dioxide (676), and sodium dichromate in aqueous phosphoric acid (677) or acetic acid (678) have been described in Section IV.2C(1), and additional data are given below. 

The copper salt of 2-carboxy-5-hydroxymethylpyrazine has been oxidized by hydrogen peroxide to 2,5-dicarboxypyrazine (1277) which was also obtained from fructosazine by oxidation with hydrogen peroxide and sodium hydroxide (1071). 

5- Dicarboxypyrazine was also obtained by permanganate oxidation of 2-carboxy-5-ethylpyrazine (352), fructosazine (182, 183), 2,5-bis(D-/yxo-tetraacetoxybutyl)-pyrazine (184), 2,5-diphenethyl-l,4-dihydropyrazine (173), a product from the ammoniation of molasses (46), and by oxidation of deoxyfructosazine (3) with hydrogen peroxide and sodium hydroxide at 80° ( ) (1072). The oxidation of 

2- D-araho-tetrahydroxybutyl)pyrazine with aqueous potassium permanganate at 90° gave 2-carboxypyrazine (544) and 2-carboxy-6-ethylpyrazine at 60° gave 

5 -dimethylpyrazin-3 -yl)pyrazine gave some 3-carboxy-2,5-dimethylpyrazine, and similar oxidation of 2,5-dimethyl-3-(2 -methylpyrazin-5 -yl)pyrazinegave some 2,5-dicarboxypyrazine and 3-carboxycarbonyl-2,5-dimethylpyrazine (718). 

---

By Oxidation of Alkyl-, Styryl-, Hydroxyalkyl-, and Fused Pyrazine Systems... 

---