Nitrogen → 4-Fluoro-1-naphthaleneboronic Acid (contains varying amounts of Anhydride)

Participants

Reaction Conditions

Reaction Steps

To a 250 mL three-necked round-bottomed flask equipped with septum and N2 (nitrogen) inlet were added 4.62 g (20.53 mmol) 4-bromo-1-fluoronaphthalene and 100 mL dry tetrahydrofuran. The solution was cooled to −70° C., and 15.4 mL (24.64 mmol) of a 1.6 M solution of butyl lithium in hexane was added dropwise over 5 min. The reaction was stirred at −70° C. for 10 min, then 4.2 mL (3.59 g, 24.64 mmol) triethyl borate was added, and the reaction stirred at −70° C. for 20 min and warmed to room temperature. After stirring overnight at room temperature, the reaction was quenched with saturated aqueous ammonium chloride solution, acidified with 1 N hydrochloric acid, and extracted into ethyl acetate (twice). The combined organic layer was washed with brine, dried over sodium sulfate, and evaporated. The residue was triturated with hexane to give an off-white powder, 1.97 g (51%), as a mixture of monoaryl and diaryl boronic acids. 1H-NMR (δ, CDCl3): 7.2-7.4 (m, 1H), 7.5-7.7 (m, 3H), 8.0-8.5 (m, 1H), 8.5 and 9.2 (m, 1H); APCI (−) (%): 189 (parent−1, 60).

Provenance & Evidence