Synthesis of 6-methylquinoxaline: 3,4-diaminotoluene (Aldrich, 100 g, 0.82 mol) was dissolved in 600 mL of hot water (70-75°C) and quickly added to a slurry of glyoxal-sodium bisulfite adduct (Aldrich, 239.5 g, 0.9 mol, 1.1 equiv) in 400 mL of water at 60°C. The reaction mixture was heated at 60 °C for 1 h and then 5 g (0.02 mol) of the glyoxal adduct was added retrospectively. After cooling to room temperature, it was filtered through a paper filter. The filtrate was neutralized to pH 7.5-7.8 with 5 M NaOH aqueous solution and subsequently extracted with ether (4 x 400 mL). The combined organic phases were dried over anhydrous Na2SO4 and concentrated by rotary evaporation to give 92 g of brown oil. This crude product was purified by vacuum distillation (boiling point 100-102 °C, 10 mmHg; literature value: 86 °C, 1 mmHg) to give 89 g (75% yield) of light yellow oily target product.
