A mixture of 6-fluoro-1-(phenylsulfonyl)-3-(1H-pyrazol-4-yl)-1H-indole (Intermediate 5; 512 mg; 1.50 mmol), 3,6-dichloropyridazine (450 mg; 3.02 mmol) and K2CO3 (828 mg; 5.99 mmol) in MeCN (15.0 mL) was stirred at 100° C. for 16 hours under nitrogen. The reaction mixture was diluted with EtOAc (30 mL) and water (10 mL). The organic layer was separated, washed with brine (10 mL), dried over anhydrous Na2SO4, filtered, concentrated, and purified by a silica gel column chromatography (petroleum ether/EtOAc=4/1 to 2/1) to afford 620 mg (91%) of the title compound as a white solid.
