To a solution of 4-(5-bromopyrrolo[1,2-b]pyridazin-4-yloxy)-3-fluoroaniline (57 mg, 0.178 mmol) and 1,5-dimethyl-3-oxo-2-phenyl-2,3-dihydro-1H-pyrazole-4-carboxylic acid (124 mg, 0.534 mmol) prepared in Preparation Example 1 in dimethylformamide (2 mL), HATU (270 mg, 0.711 mmol) and triethylamine (0.1 mL, 0.711 mmol) were sequentially added and stirred at 50° C. overnight. The resulting reaction mixture was concentrated under reduced pressure and the resulting residue was extracted with dichloromethane and water. The organic layer was separated, dried with magnesium sulfate, and then filtered. The filtrate was concentrated under reduced pressure. The resulting residue was purified by silica gel chromatography (10% ethyl acetate in dichloromethane) to give the target compound as a white solid (60 mg, 0.111 mmol, 63% yield).
