Br[C:2]1[C:16]([CH3:17])=[CH:15][C:5]([O:6][CH2:7][O:8][CH2:9][CH2:10][Si:11]([CH3:14])([CH3:13])[CH3:12])=[C:4]([O:18][CH3:19])[CH:3]=1.C([Li])CCC.[B:25](OC)([O:28]C)[O:26]C>C1COCC1>[CH3:19][O:18][C:4]1[C:5]([O:6][CH2:7][O:8][CH2:9][CH2:10][Si:11]([CH3:14])([CH3:13])[CH3:12])=[CH:15][C:16]([CH3:17])=[C:2]([B:25]([OH:28])[OH:26])[CH:3]=1[2-(4-Bromo-2-methoxy-5-methyl-phenoxymethoxy)-ethyl]-trimethyl-silane (2.6 g, 7.5 mmol) was stirred in dry THF (10 mL) at −78° C. under argon. n-Butyllithium (3.75 mL, 2.5 M in hexanes, 9.36 mmol) was added dropwise, and the reaction stirred for 30 min before it was transferred via cannula to a flask of trimethyl borate (8.4 mL, 75 mmol) in THF (15 mL), which was also stirring at −78° C. under argon. After addition was complete, the reaction stirred 30 min at −78° C. and then 30 min while warming to 0° C. It was then quenched with H2O (20 mL), acidified with 0.1 N HCl, and extracted with ethyl acetate (2×25 mL). Organics were washed with brine (20 mL), dried (Na2SO4), and concentrated in vacuo. Purification by silica gel chromatography (20% to 50% ethyl acetate/hexanes) gave 1.11 g (47%) of 5-methoxy-2-methyl-4-[2-(trimethyl-silanyl)-ethoxymethoxy]-phenyl-boronic acid as a white solid. 1H NMR (300 MHz, CDCl3) δ 7.78 (s, 1H), 7.10 (s, 1H), 5.36 (s, 2H), 3.93 (s, 3H), 3.83 (t, 2H, J=8.4 Hz), 2.79 (s, 3H), 0.98 (t, 2H, J=8.4 Hz), 0.01 (s, 9H). Anal. (C14H25BO5Si—H2O)C, H. Calculated: C, 57.15; H, 7.88. Found: C, 56.89; H, 7.87.
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