Triisopropyl borate → 5-(1-(Tert-butyldimethylsilyloxy)propan-2-yl)-2-fluoropyridin-3-ylboronic acid

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Reaction Conditions

Reaction Steps

n-Butyllithium (1.55M in hexane) (Aldrich, St. Louis, Mo.; 4.98 mL, 7.72 mmol) was added (dropwise over 5 min) to a solution of 5-(1-(tert-butyldimethylsilyloxy)propan-2-yl)-2-fluoropyridine (1.89 g, 7.01 mmol) in THF (35 mL) at −78° C., and the resulting yellow solution was stirred at −78° C. for 1 h. Triisopropyl borate (Aldrich, St. Louis, Mo.; 1.935 mL, 8.42 mmol) was then added, and the resulting mixture was stirred at −78° C. for 1 h. The reaction mixture was subsequently partitioned between EtOAc (250 mL) and water (90 mL) (1N aq. HCl (12.0 mL) was added to bring the pH to about 6.5). The organic layer was separated, and the aqueous layer was extracted with EtOAc (2×100 mL). The combined organic extracts were dried over sodium sulfate, filtered, and concentrated in vacuo to provide 5-(1-(tert-butyldimethylsilyloxy)propan-2-yl)-2-fluoropyridin-3-ylboronic acid (2.25 g, 7.18 mmol, 102% yield) as a colorless oil, which was used directly in the subsequent step. m/z (ESI, +ve) 314.2 (M+H)+.

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