GENERAL STEPS: In a reaction vessel equipped with a charging funnel, 4-bromophenylboronic acid (5 mmol) was dissolved in methanol (10 mL). A solution of potassium hydrogen fluoride (KHF2, 1.56 g, 20 mmol) in water (8 mL) was added slowly and dropwise. The reaction mixture was stirred at room temperature for 30 min. Subsequently, the mixture was concentrated under high vacuum to remove the solvent. The residual solid was extracted with an acetone solution of 20% methanol (4 x 10 mL). The extracts were combined, concentrated to near saturation, and then ether (Et2O) was added until no further precipitate was produced. The precipitate was collected by filtration, washed with ether (2 × 10 mL), and finally dried under high vacuum to give a potassium 4-bromophenyl trifluoroborate product of sufficient purity for subsequent characterization.
