[CH3:1][O:2][C:3]1[N:8]=[N:7][C:6]([C:9]2[CH:17]=[CH:16][C:12]([C:13]([OH:15])=[O:14])=[CH:11][CH:10]=2)=[CH:5][CH:4]=1.OS(O)(=O)=O.[CH3:23]O>>[CH3:23][O:14][C:13](=[O:15])[C:12]1[CH:16]=[CH:17][C:9]([C:6]2[N:7]=[N:8][C:3]([O:2][CH3:1])=[CH:4][CH:5]=2)=[CH:10][CH:11]=1To a solution of 4-(6-methoxy-pyridazin-3-yl)-benzoic acid (5.02 g, 21.8 mmol) (reference example 11f) in methanol (75 mL) is added slowly conc. H2SO4 (3.75 mL). The resulting solution is heated to 50° C. and stirred for 1 hour. The solution is then concentrated to one third volume, cooled to 0°-5° C., adjusted to pH 6 with sat NaHCO3 soln and extracted into ethyl acetate. The organic layer is washed with brine, dried over MgSO4 and concentrated. The residue is purified by flash chromatography (eluting with 20% ethyl acetate in dichloromethane) to give 4.26 g of title compound as a white crystalline solid. 1H NMR (DMSO) δ 3.90 (s, 3H), 4.10 (s, 3H), 7.38 (d, J=9 Hz, 1H), 8.10 (d, J=9 Hz, 2H), 8.25 (m, 3H). MS (EI) m/z 244 (M+).
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