Quinoxaline-2,3-dicarboxylic acid derivatives

The cleavage of fused pyrazines represents an important method of synthesis of substituted pyrazines, particularly pyrazinecarboxylic acids. Pyrazine-2,3-dicarboxylic acid is usually prepared by the permanganate oxidation of either quinoxalines or phenazines. The pyrazine ring resembles the pyridine ring in its stability rather than the other diazines, pyridazine and pyrimidine. Fused systems such as pteridines may easily be converted under either acidic or basic conditions into pyrazine derivatives (Scheme 75). 

The electrolytic oxidation of quinoxaline at a copper anode gives pyrazine-2,3-dicarboxylic acid in excellent yield. A similar conversion may be effected with alkaline potassium permanganate, and a list of quinoxaline derivatives which can be oxidized with potassium... 

Quinoxaline Derivatives Which Can Be Oxidized to Pyrazine-2,3-dicarboxylic Acids on a Preparative Scale... 

Quinoxaline derivatives (36), and not the expected sydnones, were obtained from the Af-nitroso derivatives of 3-arylamino-l-aryl-pyrrolidine-2,5-diones (35). The precise nature of this rearrangement has not so far been determined.40 The derived quinoxaline-2,3-dicarboxylic acid mono-jV-arylamides (37) were obtained in 40-60% yield. The latter compounds were also made by the conventional reaction of quinoxaline 2,3-dicarboxylic anhydride and an amine.40... 

The mass spectra of some formyl derivatives of 2-(2 -thienyl)indole have been elucidateThe electroreduction of 4-(2-thienyl)quinoxaline has been further investigated. The preparation of 2,5-bis(benzoxazolyl)-thiophens from thiophen-2,5-dicarboxylic acid has been patented... 

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