Tributyl borate → (5-Methoxy-1-benzofuran-2-yl)boronic acid

Participants

Reaction Conditions

Reaction Steps

5-Methoxybenzofuran (5.3 g, 35.8 mmol) was dissolved in anhydrous THF (120 mL) and cooled to −30° C. The solution was treated with n-BuLi (18 mL, 45 mmol, 2.5 M in hexanes) over 30 min, maintaining the internal temperature at −30° C. during the addition to give a yellow solution. After 1 h at −30° C., tributyl borate (12.2 mL, 45.1 mmol) was added over 10 min and the solution became pale yellow. The resulting solution was allowed to warm slowly to 14° C. over 12 h, then was quenched with 6 M HCl (50 mL) and extracted with EtOAc (150 mL). The organics were washed with water, then brine and dried over MgSO4. After filtration, the organic solution was concentrated and the boronic acid precipitated by the addition of hexanes. The solid was filtered and washed with hexanes to give an off-white solid (3.95 g, 48%).

Provenance & Evidence