A reaction was carried out in acetonitrile (200 mL) in the presence of potassium carbonate (1.2 eq., 4.39 g) with 2,6-dichloropurine (5.0 g, 1.0 eq.) and iodomethane (1.1 eq., 1.81 mL). The reaction mixture was stirred at 20 °C for 70 hours. After completion of the reaction, the solvent was removed by rotary evaporator. The crude product was separated by column chromatography (eluent: dichloromethane/methanol, 90/10, v/v) to afford 2,6-dichloro-9-methyl-9H-purine (3.55 g, 66% yield) and 2,6-dichloro-7-methylpurine (1.61 g, 30% yield).
