Trimethyl borate → 3-Cyano-4-fluorophenylboronic acid

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Reaction Steps

Trimethylborate (1.37 mL, 12 mmol) was added to a solution of 5-bromo-2-fluorobenzonitrile (2.0 g, 10 mmol) in toluene (16 mL) and THF (4 mL) at −78° C. n-Butyl lithium (2.5M in hexane; 4.8 mL) was slowly added over 1 h and the solution was stirred for 30 min after which it was warmed to rt for 1 h. The reaction was cooled to 0° C. and quenched with 20 mL of 1 N HCl. The product was extracted with ethyl acetate (2×200 mL), dried over magnesium sulfate, filtered and concentrated in vacuo. Silica gel chromatography eluting with 5% methanol/methylene chloride afforded 0.33 g of the desired product.

Provenance & Evidence