To a vial charged with 2-((2-chloro-5-cyano-3-(4-oxopiperidin-1-yl)phenyl)amino)-4-(cyclopropyl(4-methoxybenzyl)amino)imidazo[2,1-f][1,2,4]triazine-7-carbonitrile (Intermediate 13) (30 mg, 0.053 mmol) and 3,3-difluorocyclobutanamine (6.79 mg, 0.063 mmol) in methanol (132 μl) and tetrahydrofuran (132 μl) was added trimethyl orthoformate (58.4 μl, 0.528 mmol). The reaction mixture was stirred at room temperature. Sodium cyanoborohydride (6.64 mg, 0.106 mmol) was added and the reaction mixture was stirred at room temperature 6 h. The reaction mixture was diluted with water and methanol and filtered. The solid was taken up in DMF and partitioned between water and ethyl acetate. The aqueous layer was washed with ethyl acetate (3×). The combined organics were washed with 10% lithium chloride solution, dried over anhydrous sodium sulfate, filtered and concentrated in vacuo. The crude material was taken forward as is.
