Hydrochloric Acid → (S)-(4-Fluoro-2-(pent-4-en-2-yloxy)phenyl)boronic acid

Participants

Reaction Steps

A solution of (S)-1-bromo-4-fluoro-2-(pent-4-en-2-yloxy)benzene (0.66 mL, 2.55 mmol, 1 equiv) in THF (13 mL) was cooled to −78° C. (IPA/dry ice). nBuLi (1.9 mL of a 1.6 M solution in hexane, 3.06 mmol, 1.2 equiv) was added slowly. No color change observed. After 45 min, triisopropyl borate (0.70 mL, 3.06 mmol, 1.2 equiv) was added. The reaction was stirred 30 min. 1 N HCl (5 mL) was added and the reaction was removed from the cold bath. After 10 min, the reaction was added to water and extracted with DCM (×3). The combined DCM extracts were dried (Na2SO4) and concentrated in vacuo to provide the crude boronic acid (0.58 g, 100%) as a viscous pale yellow oil. Purity is ˜80%. The crude boronic acid was for used as is for the Suzuki coupling. 1H NMR (500 MHz, CDCl3) δ 7.85 (t, J=8.0 Hz, 1H), 6.74 (td, J=8.3, 2.2 Hz, 1H), 6.66-6.62 (m, 1H), 5.87 (ddt, J=17.1, 10.1, 7.1 Hz, 1H), 5.24-5.18 (m, 2H), 4.63-4.54 (m, 1H), 2.60-2.45 (m, 2H), 1.43 (d, J=6.1 Hz, 3H).

Provenance & Evidence