Step b: Synthesis of 4-chloro-2-amino-5-methylpyrimidine
5-Methylisocytosine (3 g, 24.0 mmol) was mixed with phosphorus trichloride (POCl3, 20 mL) and heated to reflux for 45 minutes. Upon completion of the reaction, the excess phosphorous trichloride was removed by distillation under reduced pressure. The residue was slowly poured into ice water and the pH was subsequently adjusted to alkaline with ammonia at 10 °C. The precipitated solid was collected by filtration and recrystallized from ethanol to afford the target compound 4-chloro-2-amino-5-methylpyrimidine (1 g, 29.0% yield).
1H NMR (400 MHz, DMSO-d6) δ: 8.11 (s, 1H, pyrimidine ring H), 6.81 (br s, 2H, NH2), 2.04 (s, 3H, CH3).
