General procedure for the synthesis of 5-fluoro-2-methoxy-4-fluoropyrimidinamine using 2-methoxy-4-chloro-5-fluoropyrimidine as starting material: 32.5 g of 2-methoxy-4-chloro-5-fluoropyrimidine (compound of formula III) was added to 170 g of a 10 wt% solution of isopropanol in ammonia, heated to 40-60 °C, and the reaction was stirred for 3-5 hours. After completion of the reaction, it was naturally cooled to room temperature and the solid product was collected by filtration. The solid was washed with isopropanol and dried to give 27.2 g of 5-fluoro-2-methoxy-4-pyrimidinamine (compound of formula II, white solid) in 95.0% molar yield and 99.0% HPLC purity.
