With reference to Scheme (XI), A DMF (300 mL) suspension of 5-(2-(4-fluoro-3-methoxy-5-methylphenylamino)-5-methylpyrimidin-4-ylamino)benzo[d]oxazol-2(3H)-one trifluoroacetate (prepared as described in Example 3) (40.38 g, 79 mmol) and Cs2CO3 (78.3 g, 238 mmol) was stirred at rt under Nitrogen atmosphere, after 2.5 h, di-tert-butyl chloromethyl phosphate (26.6 g, 103 mmol) was added and stirring was continued at room temperature. After 49 h, by LC-MS, the reaction was >90% complete (note: due to relatively poor quality of alkylating agent of this batch, additional ˜7 g of di-tert-butyl chloromethyl phosphate was added). With stirring, the reaction mixture was poured into 1.2 L of H2O, ppt formed and was a bit lumpy, additional 500 mL of H2O was added to ensure the formation of non-sticky solid. Precipitate was collected by filtration, washed with water, and was further dried under high vac. Compound di-tert-butyl (5-(2-(4-fluoro-3-methoxy-5-methylphenylamino)-5-methylpyrimidin-4-ylamino)-2-oxobenzo[d]oxazol-3(2H)-yl)methyl phosphate was obtained as a light brown solid and was used directly in the next reaction.
