Hydrochloric Acid → 1H-Indol-6-ylboronic acid

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A solution of 6-Bromo-1H-indole (1.5 g, 7.65 mmol) in THF (10 mL) was added dropwise to a suspension of potassium hydride (0.31 g, 7.65 mmol) in THF at 0° C. After fifteen minutes at 0° C., the solution was cooled to -78° C. and a t-butyl lithium solution (1.7 M in pentane, 9.0 mL, 15.3 mmol) was added dropwise via syringe while maintaining a temperature below −55° C. After 15 minutes, the solution was cooled to −78° C. and treated with a tributyl borate (4.14 mL, 15.3 mmol). The solution was stirred at −78° C. for 2 hours and then allowed to warm to −10° C. The solution was the added 75 mL of 1 M HCl, warmed to room temperature and separated. The aqueous phase was extracted with diethyl ether (3×75 mL) and the combined organics were extracted with 1 M NaOH (4×40 mL). The aqueous layers were combined, adjusted to pH ˜2 with 6 M HCl and extracted with diethyl ether (4×50 mL). The combined organic layers were washed with brine (20 mL), dried (MgSO4), filtred and concentrated. The concentrate was purified by flash chromatography on silica gel using 3.5-5% methanol/dichloromethane to give 838 mg (68% yield) of the desired product. MS (ESI(+)) m/e 161 (M+H)+.

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