5-Cyano-2-fluorobenzeneboronic acid

121-43-7

1194-02-1

468718-30-1

468717-46-6

Example 163 Synthesis of 3-(2-dimethylaminomethyl-cyclopropyl)-1H-indazole-5-carbonitrile Procedure: n-BuLi (1.9 M, 26.3 mL, 50 mmol) was slowly added dropwise under nitrogen protection to a solution of diisopropylamine (7.71 mL, 55 mmol) in anhydrous THF (100 mL), keeping the reaction temperature at 0 °C. After 10 min. the reaction system was cooled to -78 °C. Subsequently, a solution of 4-fluorobenzonitrile (6.06 g, 50 mmol) in anhydrous THF (20 mL) was added dropwise at a rate that maintained the internal temperature at -78 °C. After stirring at this temperature for 1 hour, trimethyl borate (8.41 mL, 75 mmol) was added dropwise, also at a rate maintaining an internal temperature of -78 °C. The reaction mixture was stirred at -78 °C and gradually warmed to room temperature for 16 hours. Upon completion of the reaction, the system was cooled to 10 °C and 25 mL of 6N HCl was added. stirring was continued at room temperature for 4 h. The reaction mixture was then partitioned between water and ethyl acetate. The organic layer was washed three times with 100 mL of 2N NaOH. The aqueous layers were combined and adjusted to pH 6 with 6N HCl. The white solid formed was extracted through three times with 100mL ethyl acetate. The organic layers were combined, dried with sodium sulfate, concentrated and dried under high vacuum to give 2-fluoro-5-cyanophenylboronic acid (5.74 g, 70% yield). The product was confirmed by 1H NMR (500 MHz, acetone-d6): δ 8.08 (1H, dd, J = 2.14,5.5 Hz), 7.90 (1H, m), 7.31 (1H, t, J = 8.85 Hz). Elemental analysis (C7H5BFNO2) Calculated values: C, 50.97; H, 3.05; N, 8.49. Measured values: C, 51.19; H, 3.19; N, 8.26.