Bromine → 4-(4-Fluorophenyl)-5-[4-(methylsulfonyl)phenyl]-3(2H)-pyridazinone

The dihydropyridazinone product from Example 18 (47 mg, 0.136 mmol) was dissolved in acetic acid (25 mL). Bromine (0.025 mL, 0.16 mmol) was added to the solution and the reaction mixture was stirred at 95° C. for 20 minutes. The reaction mixture was concentrated under reduced pressure. The residue was partitioned between ethyl acetate and water. The organic layer was washed with brine, dried over MgSO4 and filtered. The filtrate was concentrated under reduced pressure to provide a solid which was eluted through a short pad of silica gel with ethyl acetate. The title compound was crystallized from ethyl acetate/hexanes (yield: 35 mg, 75%). mp 255-256° C. 1H NMR (300 MHz, CDCl3) δ 3.07 (s, 3H), 6.98 (t, J=9 Hz, 2H), 7.16-7.23 (m, 2H), 7.35 (d, J=9Hz, 2H), 7.86 (s, 1H), 7.91 (d, J=9 Hz, 2H). MS (DCI/NH3) m/z 345 (M+H)+ and m/z 362 (M+NH4)+.