Trimethyl borate → (2-(Benzyloxy)naphthalen-1-yl)boronic acid

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To a suspension of 1-bromo-2-(phenylmethoxy)naphthalene (6.26 g, 20.0 mmol) in Et2O (75 mL) at −78° C. was added n-BuLi (8.0 mL, 2.5 M, 20 mmol) in hexanes and the mixture was stirred at 0° C. for 1 h. After re-cooling to −78° C., the mixture was treated with trimethyl borate (2.5 mL, 22 mmol) and allowed to warm to room temperature overnight. The resulting mixture was quenched with 1 M HCl (50 mL) and stirred at room temperature for 45 min. The phases were separated and the extraction was completed with CH2Cl2. The combined organic extracts were dried (MgSO4) and evaporated in vacuo to give the title compound, 2-(phenylmethoxy)-1-napthaleneboronic acid as a white powder (4.62 g, 83%), which was used in the next step without further purification. For analytical purposes, a small amount of the product was re-crystallised from MeOH/H2O: mp 133.0-135.0° C. (MeOH/H2O); 1H NMR (250 MHz, d4-MeOH) δ5.20 (s, 2H), 7.28-7.60 (m, 9H), and 7.56-7.88 (m, 2H); 13C NMR (63 MHz, d4-MeOH) δ71.95, 115.4, 124.8, 127.7 (2C), 128.4, 128.9, 129.5, 129.6, 130.7 (2C?), 131.8, 137.2, 139.0 and 159.7;i IR (CHCl3) νmax 3609, 3490, 1592, 1509, 1386, and 1332 cm−1; MS (EI+) m/z (rel intensity) 278 (10%, M+), 234 (10), and 91 (100); HRMS calcd for C17H15BO3 (M+) 277.1151, found 277.1163. Anal. Calcd for C17H15BO3: C, 73.42; H, 5.44. Found: C, 73.07; H, 5.33.

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