2,2,6,6-Tetramethylpiperidine → 1-(tert-Butoxycarbonyl)-2-pyrroleboronic Acid

Temperature

-78 °C

n-Butyllithium (29 ml of a 1.6M solution in hexane, 47.4 mmol) was added dropwise over 10 minutes to a solution of 2,2,6,6-tetramethylpiperidine (6.7 g, 47.4 mmol) in THF (175 ml) cooled to −78° C. A solution of 1-t-butoxycarbonylpyrrole (8.19 g, 49 mmol) in THF (25 ml) was added and the mixture was maintained below −70° C. The reaction mixture was stirred for 1.5 hours at −78° C. and tri-isopropyl borate (17 g, 90 mmol) was added. The reaction mixture was then allowed to warm to ambient temperature over 1 hour. The mixture was diluted with ether (500 ml) and washed with 1M potassium hydrogen sulphate solution (100 ml×3), 1M sodium hydrogen carbonate solution (100 ml×2) and brine (100 ml). The ether phase was dried (MgSO4) and the solvent removed by evaporation. The residue was purified by flash column chromatography eluting with isohexanes/ethyl acetate (a gradient from 100/0 to 50/50) to give the 1-t-butoxycarbonylpyrrol-2-ylboronic acid (4.05 g, 43%).

1. temperaturethe mixture was maintained below −70° C
2. temperatureto warm to ambient temperature over 1 hour
3. washwashed with 1M potassium hydrogen sulphate solution (100 ml×3), 1M sodium hydrogen carbonate solution (100 ml×2) and brine (100 ml)
4. dry with materialThe ether phase was dried (MgSO4)
5. customthe solvent removed by evaporation
6. customThe residue was purified by flash column chromatography
7. washeluting with isohexanes/ethyl acetate (a gradient from 100/0 to 50/50)

ORD record

ord-223e5a170a224968b9d61a25e5b85170

Source dataset

uspto-grants-2001_07

DOI

10.6084/m9.figshare.5104873.v1

Patent number

US06265411B1