I([O-])(=O)(=O)=O.[Na+].C([O-])(=O)C.[NH4+].[Cl:12][C:13]1[CH:14]=[C:15]([CH2:28][C:29]([O:31][CH3:32])=[O:30])[CH:16]=[CH:17][C:18]=1[B:19]1[O:23]C(C)(C)C(C)(C)[O:20]1>CC(C)=O.O>[Cl:12][C:13]1[CH:14]=[C:15]([CH2:28][C:29]([O:31][CH3:32])=[O:30])[CH:16]=[CH:17][C:18]=1[B:19]([OH:20])[OH:23]Sodium periodate (1.967 g, 9.20 mmol) and ammonium acetate (0.709 g, 9.20 mmol) were added to a stirred solution of methyl 2-(3-chloro-4-(4,4,5,5-tetramethyl-1,3,2-dioxaborolan-2-yl)phenyl)acetate (Intermediate 2-7; 0.952 g, 3.07 mmol) in acetone (20 mL) and water (10 mL). The resulting suspension was stirred at ambient temperature for 17 hours. The reaction mixture was diluted with water (50 mL) and extracted with EtOAc (3×250 mL). The organic extracts were combined washed with saturated brine (100 mL), dried over MgSO4, filtered and evaporated to afford 2-chloro-4-(2-methoxy-2-oxoethyl)phenylboronic acid (0.656 g, 94%) as a cream oil which solidified on standing, and was used without further purification.
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