[CH3:1][O:2][C:3]([C:5]1[C:14]2[C:9](=[CH:10][CH:11]=[CH:12][CH:13]=2)[N:8]=[C:7](Cl)[CH:6]=1)=[O:4].[F-:16].[K+]>CS(C)(=O)=O.ClCCl.O>[CH3:1][O:2][C:3]([C:5]1[C:14]2[C:9](=[CH:10][CH:11]=[CH:12][CH:13]=2)[N:8]=[C:7]([F:16])[CH:6]=1)=[O:4]2-Chloroquinoline-4-carboxylic acid methyl ester (1.14 g) in dimethylsulfone (4.0 g) was treated with potassium fluoride (2.5 g) and heated at 180° C. for 1 h. The reaction mixture was cooled to room temperature, diluted with dichloromethane:water (1:1, 200 ml), the organic phase separated, solvent removed at reduced pressure and the residue column chromatographed (silica gel, dichloromethane eluant) to give 2-fluoroquinoline-4-carboxylic acid methyl ester (0.7 g). 1H NMR (CDCl3) δ: 3.99 (3H, s), 7.57 (2H, m), 7.72 (1H, m), 7.95 (1H, d, J=8.5 Hz), 8.67 (1H, d, J=8.4 Hz). m/z (API+): 205 (MH+).
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