[Synthesis]
The reaction was carried out with 4-iodo-1,2-benzenediamine (0.46 g, 1.96 mmol) and glyoxal (40% aqueous solution, 2.25 mL) in a solvent mixture of acetic acid (1 mL) and ethanol (20 mL), heated at 100 °C for several hours. After completion of the reaction, the mixture was cooled to room temperature. Subsequently, water was added for dilution and the crude product was extracted with ethyl acetate. The target compound 6-iodoquinoxaline (0.323 g, 64% yield) was purified by silica gel column chromatography using hexane and ethyl acetate (1:1, v/v) as eluent. The product was characterized by 1H NMR (400 MHz, CDCl3) with chemical shifts (δ) of 8.77 (dd, 2H, J = 2.0, 8.8 Hz), 8.46 (d, 1H, J = 2.0 Hz), 7.96 (dd, 1H, J = 2.0, 8.8 Hz), 7.75 (d, 1H, J = 8.8 Hz). |