反应详情

温度

-78 °C

n-Butyllithium (2.5 M in hexanes, Aldrich; 20.0 mL, 50.0 mmol) was added (dropwise over 20 min) to a solution of (R)-tert-butyl 4-(1-(6-fluoropyridin-3-yl)ethyl)piperazine-1-carboxylate (10.0 g, 32.3 mmol) in THF (150 mL) at −78° C., and the resulting mixture was stirred at −78° C. for 20 min. Triisopropyl borate (15.0 mL, 65.2 mmol) was then added (dropwise over 10 min), followed by additional THF (20 mL) to rinse solidified triisopropyl borate from the side of the flask. The resulting mixture was stirred at −78° C. for min, and the cooling bath was then removed. The reaction mixture was stirred for 1 h, and 1 N aq. NaOH (100 mL) and water (40 mL) were then sequentially added. The resulting mixture was stirred for 10 min, and the organic layer was separated. The organic layer was extracted with 1 N aq. NaOH (40 mL), and the aqueous layers were then combined and pH-adjusted with N aqueous HCl to a final pH of about 5. The resulting mixture was extracted with EtOAc (3×200 mL), and the combined organic extracts were dried over sodium sulfate, filtered, and concentrated in vacuo to provide (R)-5-(1-(4-(tert-butoxycarbonyl)piperazin-1-yl)ethyl)-2-fluoropyridin-3-ylboronic acid (9.27 g, 81% yield) as a white solid. 1H NMR (400 MHz, d4-MeOH) δ 8.39 (br. s., 1H), 8.26 (d, J=6.5 Hz, 1H), 4.54-4.63 (m, 1H), 3.31 (br. s., 4H; masked by MeOH), 3.13 (br. s., 4H), 1.80 (d, J=6.8 Hz, 3H), 1.45 (s, 9H). 19F NMR (377 MHz, d4-MeOH) δ −60.93 (br. s., 1F). m/z (ESI, +ve) 354.2 (M+H)+.

1. washto rinse solidified triisopropyl borate from the side of the flask
2. stirringThe resulting mixture was stirred at −78° C. for min
3. customthe cooling bath was then removed
4. stirringThe reaction mixture was stirred for 1 h
5. addition1 N aq. NaOH (100 mL) and water (40 mL) were then sequentially added
6. stirringThe resulting mixture was stirred for 10 min
7. customthe organic layer was separated
8. extractionThe organic layer was extracted with 1 N aq. NaOH (40 mL)
9. extractionThe resulting mixture was extracted with EtOAc (3×200 mL)
10. dry with materialthe combined organic extracts were dried over sodium sulfate
11. filtrationfiltered
12. concentrationconcentrated in vacuo