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

Temperature

-30 °C

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%).

1. temperaturemaintaining the internal temperature at −30° C.
2. additionduring the addition
3. customto give a yellow solution
4. temperatureto warm slowly to 14° C. over 12 h
5. customwas quenched with 6 M HCl (50 mL)
6. extractionextracted with EtOAc (150 mL)
7. washThe organics were washed with water
8. dry with materialbrine and dried over MgSO4
9. filtrationAfter filtration
10. concentrationthe organic solution was concentrated
11. customthe boronic acid precipitated by the addition of hexanes
12. filtrationThe solid was filtered
13. washwashed with hexanes

ORD record

ord-40f7125d92ff413d8e17c0e8a4f9b442

Source dataset

uspto-grants-2016_01

DOI

10.6084/m9.figshare.5104873.v1

Patent number

US09227986B2