Diisopropylamine → 2-Fluoro-5-methylpyridine-3-boronic acid

Beteiligte Stoffe

Reaktionsbedingungen

Reaktionsschritte

n-Butyllithium (2.5M solution in hexane, 9.6 mL, 24 mmol) was added to a mixture of diisopropylamine (3.4 mL, 24 mmol) in THF (5.00 mL, 61 mmol) at 0° C. and the resulting pale yellow solution was stirred at the same temperature for 30 min and then cooled down to −78° C. A suspension of 2-fluoro-5-methylpyridine (Aldrich, St. Louis, Mo.) (2.22 g, mmol) in THF (5.00 mL, not complete dissolved) was slowly added. The resulting bright yellow solution was stirred at −78° C. for 1 h, treated with a solution of tri-1-propylborate (6.9 mL, 30 mmol) in THF (10.00 mL) and then allowed to warm up to room temperature. The yellow suspension was quenched with 1 N NaOH until basic (pH about 10) and the organic layer was separated. The aqueous layer was collected and carefully acidified with 6N aqueous HCl until slightly acidic, and then extracted with EtOAc(×3). The combined organic layers were dried (Na2SO4), filtered and concentrated. The resulting white solid was washed with ether to give 2-fluoro-5-methylpyridin-3-ylboronic acid (2.9196 g, 94% yield) as a white solid. LCMS (API-ES) m/z 156 (M+H)+.

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