Diisopropylamine → 2-Fluoro-5-methylpyridine-3-boronic acid

Temperature

-78 °C

n-Butyllithium (2.5M solution in hexane, 9.6 mL, 24 mmol) was added to a mixture of diisopropylamine (3.4 mL, 24 mmol) in THF (5.00 mL, 61 mmol) at 0° C. and the resulting pale yellow solution was stirred at the same temperature for 30 min and then cooled down to −78° C. A suspension of 2-fluoro-5-methylpyridine (Aldrich, St. Louis, Mo.) (2.22 g, mmol) in THF (5.00 mL, not complete dissolved) was slowly added. The resulting bright yellow solution was stirred at −78° C. for 1 h, treated with a solution of tri-1-propylborate (6.9 mL, 30 mmol) in THF (10.00 mL) and then allowed to warm up to room temperature. The yellow suspension was quenched with 1 N NaOH until basic (pH about 10) and the organic layer was separated. The aqueous layer was collected and carefully acidified with 6N aqueous HCl until slightly acidic, and then extracted with EtOAc(×3). The combined organic layers were dried (Na2SO4), filtered and concentrated. The resulting white solid was washed with ether to give 2-fluoro-5-methylpyridin-3-ylboronic acid (2.9196 g, 94% yield) as a white solid. LCMS (API-ES) m/z 156 (M+H)+.

1. dissolutionnot complete dissolved)
2. additionwas slowly added
3. stirringThe resulting bright yellow solution was stirred at −78° C. for 1 h
4. temperatureto warm up to room temperature
5. customThe yellow suspension was quenched with 1 N NaOH until basic (pH about 10)
6. customthe organic layer was separated
7. customThe aqueous layer was collected
8. extractionthen extracted with EtOAc(×3)
9. dry with materialThe combined organic layers were dried (Na2SO4)
10. filtrationfiltered
11. concentrationconcentrated
12. washThe resulting white solid was washed with ether

ORD record

ord-43ed9d07c9bc412bbe090493db00c50c

Source dataset

uspto-grants-2014_07

DOI

10.6084/m9.figshare.5104873.v1

Patent number

US08772480B2