General procedure for the synthesis of 2,4-diamino-6-methoxypyrimidine from methanol and 2,4-diamino-6-chloropyrimidine: 9.2 g (0.40 mol) of sodium metal was added to a flask containing 320 mL of methanol and stirred until completely dissolved. Subsequently, 28.9 g (0.20 mol) of 2,4-diamino-6-chloropyrimidine was added to this solution. The reaction mixture was placed under reflux conditions and stirred continuously for 44 hours. Upon completion of the reaction, the precipitated sodium chloride was removed by filtration. The filtrate was concentrated to dryness to give the crude product. The crude product was dissolved in 300 mL of ethanol, heated to boiling and then thermally filtered. The filtrate was allowed to stand overnight to crystallize 2,4-diamino-6-methoxypyrimidine. The product can be further purified by recrystallization of the mother liquor. After drying, 2,4-diamino-6-methoxypyrimidine (58.8 g, 84% yield) was obtained as a white solid. Melting point: 166-169 °C. 1H-NMR (300 MHz, d6-DMSO): δ= 3.18 (s, 3H, 6-OMe), 5.06 (s, 1H, 5-H), 5.94 (s, 2H, NH2), 6.05 (s, 2H, NH2). 13C-NMR (125 MHz, d6-DMSO): δ= 52.8 ( 6-OMe), 76.1 (5-C), 163.3 (2-C), 166.3 (4-C), 170.8 (6-C).
