To a solution of 3-(1-cyanocyclopropyl)benzoic acid (1.50 g, 8.01 mmol) in tetrahydrofuran (30 mL) were added N,N-dimethylformamide (2 drops) and oxalyl chloride (1.16 mL, 13.3 mmol), and the mixture was stirred at room temperature for 1.5 hr. The solvent was evaporated under reduced pressure, and the residue and N-[6-(3-aminophenoxy)imidazo[1,2-b]pyridazin-2-yl]acetamide (1.89 g, 6.67 mmol) were dissolved in N-methylpyrrolidone (30 mL), and the mixture was stirred at room temperature for 3 hr. Saturated aqueous sodium hydrogencarbonate solution was added to the reaction mixture, and the mixture was extracted with ethyl acetate. The extract was washed with saturated brine, dried over anhydrous magnesium sulfate and filtrated, and the residue was purified by silica gel column chromatography (ethyl acetate/hexane=0/100→100/0) to give the title compound (2.25 g, 75%) as a pale-brown powder.
