The product of Step A, methyl (3S,4R)-4-(2,4-difluorophenyl)pyrrolidine-3-carboxylate (0.46 g, 1.91 mmol) was dissolved in dioxane (2 ml). DIPEA (1.33 mL, 7.64 mmol) and 3,6-dichloropyridazine (1.42 g, 9.55 mmol) were added. The reaction was conducted at 120° C. for 5 minutes and at 150° C. for 10 minutes with microwave. Then, the reaction mixture was concentrated in vacuo. The obtained residue was diluted with EtOAc, washed with water and purified by column chromatography (eluent: EtOAc/Hex=1/5) to give the title compound (0.44 g, 65%).
