A mixture of 3-(1-phenyl-1H-pyrazol-5-yl)-1-[3-(trifluoromethyl)phenyl]pyridazin-4(1H)-one (49.0 mg, 0.128 mmol) and selectfluor (45.4 mg, 0.128 mmol) in MeCN (1 mL) was stirred at room temperature for 6 days. To the mixture was added selectfluor (45.4 mg, 0.128 mmol) at room temperature. The mixture was stirred at room temperature for 1 day. To the mixture was added selectfluor (45.4 mg, 0.128 mmol) at room temperature. The mixture was stirred at room temperature for 1 day. To the mixture was added selectfluor (45.4 mg, 0.128 mmol) at room temperature. The mixture was stirred at room temperature for 1 day. To the mixture was added selectfluor (272 mg, 0.768 mmol) at room temperature. The mixture was stirred at room temperature for 3 days. The mixture was diluted with brine, extracted with AcOEt, dried over MgSO4, filtered, concentrated in vacuo, purified by column chromatography on silica gel (hexane/AcOEt=50/50 to 0/100) and crystallized with AcOEt/hexane to yield the title compound (11.7 mg, 23% yield) as a pale yellow solid: mp 156-158° C. 1H NMR (DMSO-d6, 300 MHz): δ ppm 6.67 (1H, d, J=8.2 Hz), 7.33-7.50 (5H, m), 7.63-7.83 (4H, m), 7.97 (1H, d, J=4.1 Hz), 8.96 (1H, d, J=8.0 Hz).
