IC.[F:3][C:4]1[C:12]([F:13])=[C:11](O)[CH:10]=[CH:9][C:5]=1[C:6]([OH:8])=[O:7].[C:15](=O)([O-])[O-].[Li+].[Li+].CN(C)[CH:23]=[O:24]>O>[F:3][C:4]1[C:12]([F:13])=[C:11]([O:24][CH3:23])[CH:10]=[CH:9][C:5]=1[C:6]([O:8][CH3:15])=[O:7]Iodomethane (10.7 mL, 172.5 mmol) was added into a mixture of 2,3-difluoro-4-hydroxybenzoic acid (10.0 g, 57.5 mmol), lithium carbonate (12.7 g, 172.5 mmol) and N,N-dimethylformamide (100 mL). The mixture was stirred at 40° C. for 12 h, and then poured into water and extracted with EtOAc. The organic extracts were dried over MgSO4. Evaporation and purification by flash chromatography (hexanes/EtOAc 5/1) gave a white solid (10.2 g, 88% yield, m.p. 66–68° C.); MS m/e 203 (M+H)+.
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