Into a three-neck round-bottom flask, 5-(2-chloro-5-methylpyrimidin-4-ylamino)benzo[d]oxazol-2(3H)-one (33.2 g, 120 mmol) and 4-fluoro-3-methoxy-5-methylbenzenamine hydrochloride (32.19 g, 168 mmol) were added, followed by i-PrOH (750 mL) and TFA (23.1 mL, 300 mmol). The reaction mixture was stirred under nitrogen atmosphere with gentle refluxing (note: with overhead stirrer at internal temperature of 75-80° C.). After 22 h, by LC-MS, the reaction was >95% complete (note: when ≦3% of the 2-chloropyrimidine starting material remained, the reaction did not progress much further even after another day or two). The reaction mixture was cooled to room temperature, precipitate was collected by filtration, washing with i-PrOH (˜50 mL×2). Compound 5-(2-(4-fluoro-3-methoxy-5-methylphenylamino)-5-methylpyrimidin-4-ylamino)benzo[d]oxazol-2(3H)-one trifluoroacetate was obtained as a light tan color solid (still a little bit damp) and was added to a NaHCO3 aqueous solution (15.12 g (180 mmol) of NaHCO3 dissolved in 1 L of H2O). The aqueous suspension was stirred at rt overnight. Solid was collected by filtration, washing with H2O (˜150 mL×3), and was further dried under high vacuum. Free base compound 5-(2-(4-fluoro-3-methoxy-5-methylphenylamino)-5-methylpyrimidin-4-ylamino)benzo[d]oxazol-2(3H)-one was obtained as an off-white solid: 44.51 g (93.8% yield).
