Trimethyl borate → (5-Cyano-2-Methoxyphenyl)Boronic Acid

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3-Bromo-4-methoxybenzonitrile (3.0 g, 14.2 mmol, 1.0 eq) was dissolved in anhydrous tetrahydrofuran (10 mLs). The solution cooled at −10° C. and stirred while isopropylmagnesium chloride (17.7 mmol, 8.8 mLs, 2.0 M in THF, 1.25 eq.) was added. The mixture was stirred for 1 hour and then trimethyl borate (1.87 g, 17.7 mmol, 2.0 mL) was added dropwise. The mixture was allowed to warm slowly to room temperature for 1 hour. The solvent was evaporated and the residue was partitioned between 5% citric acid and ethyl acetate. The organic layer was separated, washed with water and brine, dried over anhydrous magnesium sulfate and concentrated to a minimum volume under reduced pressure. The residue was recrystallized from hexanes to give 5-cyano-2-methoxybenzeneboronic acid (2.48 g, 99%) as a fluffy white powder.

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