[F:1][C:2]1[CH:20]=[CH:19][C:5]([CH2:6][CH2:7][C:8]2[C:9]([C:15]([O:17][CH3:18])=[O:16])=[N+:10]([O-])[CH:11]=[CH:12][CH:13]=2)=[CH:4][CH:3]=1.CN(C=[O:25])C>FC(F)(F)C(OC(=O)C(F)(F)F)=O>[F:1][C:2]1[CH:20]=[CH:19][C:5]([CH2:6][CH2:7][C:8]2[C:9]([C:15]([O:17][CH3:18])=[O:16])=[N:10][C:11]([OH:25])=[CH:12][CH:13]=2)=[CH:4][CH:3]=1A solution of 3-(4-fluorophenethyl)-2-(methoxycarbonyl)pyridine-1-oxide (7.96 g) in DMF (100 ml) and trifluoroacetic anhydride (40.9 ml) was stirred under an inert atmosphere at ambient temperature for 24 hours. The reaction mixture was concentrated under reduced pressure, diluted with saturated aqueous sodium bicarbonate (150 ml) and extracted with dichloromethane (3×100 ml). The combined organic extracts were dried and concentrated under reduced pressure and the residue purified on a silica flash column eluting with methanol/dichloromethane (1:9) to give methyl 3-(4-fluorophenethyl)-6-hydroxypyridin-2-carboxylate as a cream solid (7.7 g).
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