I([O-])(=O)(=O)=O.[Na+].[CH3:7][C:8]1[CH:13]=[C:12]([B:14]2[O:18]C(C)(C)C(C)(C)[O:15]2)[CH:11]=[CH:10][C:9]=1[OH:23].C([O-])(=O)C.[NH4+]>CC(C)=O.O>[OH:23][C:9]1[CH:10]=[CH:11][C:12]([B:14]([OH:18])[OH:15])=[CH:13][C:8]=1[CH3:7]
Sodium periodate (4.22 g, 19.74 mmol) was added to 2-methyl-4-(4,4,5,5-tetramethyl-1,3,2-dioxaborolan-2-yl)phenol (1.54 g, 6.58 mmol) and ammonium acetate (1.52 g, 19.74 mmol) in acetone and water (2:1, 66 mL) at room temperature. The mixture was stirred for nineteen hours, then filtered, and concentrated. Sodium chloride was added to the filtrate, and it was extracted with ethyl acetate. The organic layer was dried over anhydrous magnesium sulfate, then filtered and concentrated. The residue was purified by silica gel chromatography eluting with 1:1 ethyl acetate:hexanes to ethyl acetate to give 364.4 mg (36%) of (4-hydroxy-3-methylphenyl)boronic acid as a solid. 1H NMR (400 MHz, d6-DMSO): δ 9.31 (s, 1H), 7.55 (s, 1H), 7.52 (d, J=8 Hz, 1H), 6.76 (d, J=8 Hz, 1H), 2.14 (s, 3H). ESI-LCMS m/z 151 (M−H)−.
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