Br[CH:2]1[CH2:5][CH2:4][CH2:3]1.[F:6][C:7]1[C:15]([F:16])=[CH:14][C:13]([OH:17])=[CH:12][C:8]=1[C:9]([OH:11])=[O:10].C(=O)([O-])[O-].[K+].[K+]>C(#N)C>[CH:2]1([O:17][C:13]2[CH:14]=[C:15]([F:16])[C:7]([F:6])=[C:8]([CH:12]=2)[C:9]([O:11][CH:2]2[CH2:5][CH2:4][CH2:3]2)=[O:10])[CH2:5][CH2:4][CH2:3]1Bromocyclobutane (150 g, 1.12 mol) was added to a mixture of 2,3-difluoro-5-hydroxybenzoic acid (50 g, 287 mmol), and potassium carbonate (230 g, 1.67 mol) in acetonitrile (1500 mL), and the resulting mixture stirred overnight at 90° C. The reaction mixture was cooled to room temperature, filtered, and concentrated under vacuum. The residue was purified via column chromatography on silica gel (eluting with petroleum ether) to afford cyclobutyl 5-cyclobutoxy-2,3-difluorobenzoate (49 g, 60%) as a yellow green solid. MS (ESI, pos. ion) m/z 283 [M+H]+.
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