Hydrochloric Acid → 2-Chloro-4-fluorobenzeneboronic acid

Participants

Reaction Steps

To 1.05 g Mg in THF (20 mL) was added catalytic I2 and then a 1 mL portion of the 2-Chloro-4-fluoro-iodobenzene (10 g total, 39 mmol) was added. The mixture was stirred, slowly warmed, and an exothermic reaction began. The remainder of the 2-Chloro-4-fluoro-iodobenzene was added at a rate to maintain the exotherm and then the reaction was heated to THF reflux for 2.5 h, then cooled to 23°. The resulting mixture was added with rapid stirring to a −70° solution of trimethyl borate (4.53 mL, 40 mmol) in THF (40 mL). The reaction was stirred at <0° for 20 min and at 23° for 16 h, then poured into 2N HCl (150 mL), stirred 2 h, and the THF was removed under vacuum. The residual aqueous solution was extracted with Et2O (3×200 mL) and the combined extracts were dried (Na2SO4) and concentrated to afford a red solid. Trituration with hexane and drying afforded the title compound as a tan solid. (1.89 g, 28%). 1H-NMR CD3OD δ 7.09 (m, 1H), 7.21 (m, 1H), 7.38 (m, 1H).

Provenance & Evidence