[F:1][C:2]1[CH:3]=[C:4]([CH:10]=[CH:11][C:12]=1F)[C:5]([O:7]CC)=[O:6].[CH3:14][C:15]1[NH:16][CH:17]=[CH:18][N:19]=1.C([O-])([O-])=O.[K+].[K+].O>CN(C)C=O.C(OCC)(=O)C>[F:1][C:2]1[CH:3]=[C:4]([CH:10]=[CH:11][C:12]=1[N:16]1[CH:17]=[CH:18][N:19]=[C:15]1[CH3:14])[C:5]([OH:7])=[O:6]To a solution of ethyl 3,4-difluorobenzoate (1.5 g) in N,N-dimethylformamide (12 mL) is added 2-methylimidazole (1.3 g) and K2CO3 (2.2 g) and the mixture is heated at 140° C. in a microwave oven for 1 h. After cooling to room temperature, water and ethyl acetate are added and the organic layer is dried (MgSO4) and concentrated. The residue is purified by chromatography (ethyl acetate/hexane 0:1→1:0). The ester is dissolved in methanol (30 mL) and 4 M aqueous NaOH (3 mL) is added and the mixture is stirred at room temperature for 1 h. The mixture is neutralized with 6 M aqueous HCl, concentrated and then acidified with 6 M aqueous HCl. The precipitate is filtered off washing with a small amount of water and dried by suction to give the title compound.
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