[Cl:1][C:2]1[CH:7]=[C:6]([Cl:8])[CH:5]=[CH:4][C:3]=1[C:9]1[N:13]2[N:14]=[C:15]([CH3:19])[CH:16]=[C:17](O)[C:12]2=[CH:11][C:10]=1[CH3:20].P(Br)(Br)[Br:22].C([O-])(O)=O.[Na+]>BrC1C=CC=CC=1.C(Cl)(Cl)Cl>[Br:22][C:17]1[C:12]2[N:13]([C:9]([C:3]3[CH:4]=[CH:5][C:6]([Cl:8])=[CH:7][C:2]=3[Cl:1])=[C:10]([CH3:20])[CH:11]=2)[N:14]=[C:15]([CH3:19])[CH:16]=1A solution of 7-(2,4-dichlorophenyl)-2,6-dimethylpyrrolo[1,2-b]pyridazin-4-ol (34.2 g, 111.5 mmol) and phosphorus tribromide (50 mL, 142.5 g, 526.4 mmol) in bromobenzene (500 mL) is refluxed for 1 h. After cooling to room temperature, the mixture is diluted with CHCl3. Saturated NaHCO3 solution is added at 0° C. to neutralize and the mixture is separated immediately. The aqueous layer is extracted with CHCl3 (2×). The combined CHCl3 solution is dried over MgSO4 and filtered. The filtrate is concentrated in vacuo to dryness. The residue is subjected to column chromatography (silica gel, 1/10 EtOAc/heptane) to afford 38.8 g (93%) of light yellow solid as the title compound: 1H NMR (400 MHz, CDCl3) δ 7.48 (d, J=1.5 Hz, 1H), 7.29 (m, 2H), 6.64 (s, 1H), 6.49 (s, 1H), 2.28 (s, 3H), 2.15 (s, 3H); 13C NMR (100 MHz, CDCl3) δ 148.9, 136.8, 135.2, 134.3, 130.1, 129.3, 127.1, 125.6, 125.1, 124.2, 123.2, 114.8, 102.3, 22.0, 12.8; MS (EI) m/z 369 (M+), 371 (M+), 373 (M+); HRMS (FAB) calcd for C15H11BrCl2N2+H 368.9561, found 368.9572.
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