General procedure for the synthesis of 6-aminoquinoxaline from 6-nitroquinoxaline: 10% palladium carbon (50 mg) was added to a solution of 6-nitroquinoxaline (500 mg, 2.86 mmol) in methanol (20 mL) and the reaction mixture was stirred for 4 hr. under an atmosphere of hydrogen at 1 atm. Upon completion of the reaction, the catalyst was removed by diatomaceous earth filtration and the filtrate was evaporated to remove the solvent. The residue was purified by silica column chromatography followed by evaporation of the solvent to afford 6-aminoquinoxaline as a yellow solid (342 mg, 82% yield) with a thin layer chromatography (TLC) Rf value of 0.32 (unfolding agent: ethyl acetate). The product was characterized by 1H NMR (CDCl3): δ 8.65 (1H, d, J=1.7 Hz), 8.55 (1H, d, J=1.7 Hz), 7.87 (1H, d, J=8.9 Hz), 7.18 (1H, dd, J=8.9,2.5 Hz), 7.13 (1H, d, J=2.5 Hz), 4.20 (2H, br. s, -NH2).
