C([O:3][C:4](=[O:21])[C:5]1[CH:10]=[C:9]([F:11])[CH:8]=[N:7][C:6]=1[O:12][C:13]1[CH:18]=[CH:17][C:16]([Cl:19])=[C:15]([Cl:20])[CH:14]=1)C.O.[OH-].[Li+].Cl>O1CCCC1>[Cl:20][C:15]1[CH:14]=[C:13]([CH:18]=[CH:17][C:16]=1[Cl:19])[O:12][C:6]1[N:7]=[CH:8][C:9]([F:11])=[CH:10][C:5]=1[C:4]([OH:21])=[O:3]
2-(3,4-Dichloro-phenoxy)-5-fluoro-nicotinic acid ethyl ester (4.9 g, 14.8 mmol, see preparation 72) was dissolved in tetrahydrofuran (50 ml). Water (27 ml) and lithium hydroxide (1.56 g, 37.1 mmol) were added and the mixture was stirred vigorously for 7 hours. The reaction mixture was acidified to pH5 by addition of 2 M hydrochloric acid and the mixture was partitioned between ethyl acetate (200 ml) and water (200 ml). The aqueous layer was acidified to pH 3 by addition of 2 M hydrochloric acid and the phases were separated. The aqueous phase was extracted with ethyl acetate (2-fold 50 ml) and the combined organic solutions were dried over magnesium sulphate and concentrated in-vacuo to give 2-(3,4-dichloro-phenoxy)-5-fluoro-nicotinic acid as a white solid (4.4 g).
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