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The oxidation of 1,4-diacetylbenzene using several oxidizing agents gave 1,4-phenylene-bis-glyoxal in 61–85% yields. A convenient and efficient synthesis of bis-quinoxaline and bis-pyrido[2,3- b ]pyrazine derivatives involves the double condensation of 1,2-diamines with 1,4-phenylene-bis-glyoxal in ethanol under reflux conditions. The structures of the new products were defined by proton nuclear magnetic resonance ( 1 H NMR), carbon-13 nuclear magnetic resonance ( 13 C NMR), Fourier-transform infrared spectroscopy (FT-IR) and mass spectrometry (MS).

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The regioselective catalyst-free synthesis of bis-quinoxalines and bis-pyrido[2,3- b ]pyrazines by double condensation of 1,4-phenylene-bis-glyoxal with 1,2-diamines