Step B: Synthesis of 2-chloro-N,N-dimethylpyrimidin-4-amine. To a solution of 2,4-dichloropyrimidine (15.0 g, 10.15 mmol) in tetrahydrofuran (THF, 150 mL) was slowly added 50% aqueous methylamine (MeNH2) (22.7 g, 25.2 mmol). The reaction mixture was stirred at room temperature for 2 hours. After completion of the reaction, the reaction solution was poured into saturated aqueous sodium bicarbonate (NaHCO3) solution and the aqueous phase was extracted three times with chloroform (CHCl3). The organic layers were combined, dried with anhydrous magnesium sulfate (MgSO4), filtered and concentrated. The crude product was purified by fast chromatography (amino silica gel column, 20% ethyl acetate/hexane as eluent) to afford 2-chloro-N,N-dimethylpyrimidin-4-amine (8.66 g, 55% yield) and 4-chloro-N,N-dimethylpyrimidin-2-amine (0.87 g, 6% yield), both as white solids.
