FC(F)(F)S(O[C:7]1[CH:12]=[CH:11][C:10]([CH:13]=[O:14])=[C:9]([CH3:15])[C:8]=1[CH3:16])(=O)=O.[B:19]1(B2OC(C)(C)C(C)(C)O2)[O:23]C(C)(C)C(C)(C)[O:20]1.C([O-])(=O)C.[K+]>O1CCOCC1.C(OCC)(=O)C.O>[CH:13]([C:10]1[CH:11]=[CH:12][C:7]([B:19]([OH:23])[OH:20])=[C:8]([CH3:16])[C:9]=1[CH3:15])=[O:14]To a solution of 4-formyl-2,3-dimethylphenyl trifluoromethanesulfonate (2.5 g) in 1,4-dioxane (50 ml) was added bis(pinacolato)diboron (2.47 g), 1,1′-bis(diphenyl-phosphino)ferrocene-palladium(II)dichloridedichloromethane complex (1:1) (1.09 g) and potassium acetate (2.61 g), and the mixture was stirred at 90° C. for 5 hours under nitrogen. The mixture was diluted with ethyl acetate and water. The organic layer was separated, washed with 1N hydrochloric acid and brine, dried over magnesium sulfate and evaporated. To a suspension of the crude product in acetone (80 ml) and water (80 ml) was added ammonium acetate (1.4 g) and sodium periodate (3.95 g), and the mixture was stirred at room temperature for 6 hours. The solvent was evaporated, and the mixture was diluted with ethyl acetate. The organic layer was separated, washed with water and brine, dried over magnesium sulfate and evaporated under reduced pressure. The residue was purified by column chromatography on silica gel (hexane/ethyl acetate=1/1) to give (4-formyl-2,3-dimethylphenyl)boronic acid (560 mg).
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