Trimethyl borate → 3-Ethyl-4-fluorophenylboronic acid

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To a solution of 95A (290 mg, 1.43 mmol) in THF (5 mL) at −78° C. was added n-BuLi (2.5 M in hexanes, 0.86 mL, 2.15 mmol). The mixture was stirred at −78° C. for 30 min before trimethyl borate (0.32 mL, 2.86 mmol) was added. The reaction was left stirring from −78° C. to rt over 3 h. It was quenched with 1.0 N HCl (2 mL), extracted with EtOAc, washed with Na2S2O3, brine and dried over Na2SO4. After evaporation of the solvent, the crude solid product was purified by silica gel column chromatography eluting with gradient CH2Cl2 in hexanes (0-15%) to give 95B (170 mg, 71% yield). 1H NMR (400 MHz, Methanol-d4) δ ppm 1.09 (t, J=7.47 Hz, 3H) 2.54 (q, J=7.47 Hz, 2H) 6.81-6.88 (m, 1H) 7.42-7.47 (m, 1H) 7.51 (d, J=9.23 Hz, 1H).

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