[CH:1]1([O:5][C:6]2[CH:7]=[C:8]([F:20])[C:9]([F:19])=[C:10]([CH:18]=2)[C:11]([O:13]C2CCC2)=[O:12])[CH2:4][CH2:3][CH2:2]1.C(O)C.[OH-].[Na+]>O>[CH:1]1([O:5][C:6]2[CH:7]=[C:8]([F:20])[C:9]([F:19])=[C:10]([CH:18]=2)[C:11]([OH:13])=[O:12])[CH2:4][CH2:3][CH2:2]1A mixture of cyclobutyl 5-cyclobutoxy-2,3-difluorobenzoate (49 g, 174 mmol), ethanol (300 mL), sodium hydroxide (20 g, 500 mmol) and water (300 mL) stirred at 60° C. overnight. The mixture was cooled to room temperature and extracted with petroleum ether (2×100 mL). The pH of the aqueous layer was adjusted to 5 with 6 M hydrochloric acid, and then it was extracted ethyl acetate (3×300 mL). The combined ethyl acetate layers were washed with brine, dried over anhydrous sodium sulfate, filtered, and concentrated to afford 5-cyclobutoxy-2,3-difluorobenzoic acid (38 g, 96%) as a white solid. MS (ESI, neg. anion) m/z 227 [M−H]−.
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