5-Bromo-2,4-dichloropyrimidine (45.6 g, 200 mmol) was dissolved in dioxane (400 mL) at room temperature and subsequently cyclopentylamine (20.4 g, 240 mmol) was added to the solution. The reaction mixture was stirred continuously for 6 hours at room temperature. After completion of the reaction, the reaction mixture was diluted with ethyl acetate, washed sequentially with saturated brine and dried over anhydrous magnesium sulfate. The solvent was removed by concentration under reduced pressure to afford 5-bromo-2-chloro-N-cyclopentyl-4-pyrimidinamine as a light yellow solid (56 g, 100% yield), which could be used in subsequent reactions without further purification. The product was characterized as follows: 1H NMR (500 MHz, DMSO-d6) δ 8.23 (1H, s), 7.37 (1H, d, J = 7.3 Hz), 4.31 (1H, m), 1.92 (2H, m), 1.71 (2H, m), 1.53-1.59 (4H, m) ppm; LCMS-ESI (POS), m/z [M + H]+: measured value 276.0, calculated value 275.9.
