General procedure for the synthesis of 6-chloro-4-methylpyrimidine-4,5-diamine from 4,6-dichloro-5-amino-pyrimidine and monomethylamine: a mixture of 5-amino-4,6-dichloropyrimidine (5,1.0 mmol), triethylamine (1.0 mmol), ethanol (4.3 mL), and monomethylamine (2.5 mmol) was placed in a steel cylinder and reacted for 3 hours by heating to 55°C. After completion of the reaction, the volatiles were removed under reduced pressure. The crude product was purified by silica gel column chromatography with the eluent CHCl3-cC6H12-CH3OH (70:20:10), followed by recrystallization with EtOAc to afford the target compound, 6-chloro-4-methylpyrimidine-4,5-diamine (6), as a white solid (148 mg, 93% yield). The product characterization data were as follows: melting point 165-67 °C; 1H NMR (400 MHz, [D6]DMSO) δ 2.89 (d, J=4.4 Hz, 3H, CH3), 4.96 (br s, 2H, NH2), 6.86 (br q, J=4.4 Hz, 1H, NH), 7.75 (s, 1H, H-2); elemental analysis ( C5H7ClN4) is consistent with theoretical values.
