Hydrochloric Acid → (5-Cyano-1-benzofuran-2-yl)boronic acid

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Reaction Steps

To benzofuran-5-carbonitrile (500 mg, 3.49 mmol) in THF (9.98 mL) at −78° C. was added nBuLi 1.6M in hexanes (2.401 mL, 3.84 mmol) dropwise. The mixture was stirred for 30 min at this temperature, and then trimethyl borate (0.858 mL, 7.68 mmol) was added dropwise. The mixture was stirred for 20 min, and then HCl 2N (11.52 mL, 23.05 mmol) was added. The bath was removed, and stirring continued for 30 min. The mixture was diluted with water and extracted with EtOAc three times, dried over magnesium sulfate, filtered, concentrated. Crude 5-cyanobenzofuran-2-ylboronic acid (623 mg, 87%) was then dried and used as is for the next step.

Provenance & Evidence