Hydrochloric Acid → 5-Fluoro-2-methoxyphenylboronic acid

Participants

Reaction Conditions

Reaction Steps

In a 200-mL flask, a solution of 2-bromo-4-fluoroanisole (Aldrich: 4.00 mL, 30.8 mmol) in THF (50 mL) was cooled to -78° C. (CO2 /IPA). To this solution n-BuLi (Aldrich: 2.5 M in hexanes; 12.4 mL, 31 mmol, 1.0 equivuiv) was added dropwise over a 30 min period. The reaction mixture was stirred at -78° C. for 60 min and treated with trimethylborate (Aldrich: 10.5 mL, 92.4 mmol, 3.0 equivuiv). The reaction mixture was allowed to slowly warm to rt, stirred overnight (12h), and cooled to 0° C. (ice/H2O). The solution was treated with 5% HCl until the pH reached 6. The reaction mixture was poured into sat'd NH4Cl (80 mL) and extracted with CH2Cl2 (3×100 mL). The extracts were washed with sat'd NH4Cl (1×80 mL), combined, dried (MgSO4), filtered through a pad of Celite™, and concentrated to afford 4.90 g (94%) of a white semi-solid. Data for 5-fluoro-20methozyphenylboronic acid: 1H NMR (400 MHz, acetone-d6): 7.47 (dd,J=8.8, 3.3, 1H); 7.17 (m, 1H); 7.05 (dd,J=9.0, 3.9, 1H); 3.93 (s, 3H).

Provenance & Evidence