Reaktion #159877

Reaktionsgleichung

ammonium chloride

1-methyl-1H-pyrazole

n-butyllithium

hydrochloric acid

triisopropyl borate

→

product

(1-methyl-1H-pyrazol-5-yl)boronic acid

Lösungsmittel

tetrahydrofuran

Reaktionsbedingungen

Aufarbeitung

1. 1
   workup.ADDITIONAfter completion of the addition
2. 2
   Temperaturthe mixture was gradually warmed to room temperature
3. 3
   workup.STIRRINGstirred overnight
4. 4
   Sonstigethe temperature of the reaction mixture below 10° C
5. 5
   SonstigeThe organic phase was separated
6. 6
   Extraktionthe aqueous phase was extracted with ethyl acetate (3×1 L)
7. 7
   WaschenThe combined organic layers were washed with saturated aqueous sodium chloride solution
8. 8
   Trocknendried over sodium sulfate
9. 9
   Filtrationfiltered
10. 10
    Sonstigeand the solvent was removed under reduced pressure
11. 11
    WaschenThe residue was washed with petroleum ether (3×300 mL)
12. 12
    Sonstigethe resulting solid was dried under vacuum

Vorschrift

To a solution of 1-methyl-1H-pyrazole (110 g, 1.34 mol) in anhydrous tetrahydrofuran (2 L), with stirring, was added drop-wise n-butyllithium (2.5 M, 590 mL, 1.47 mol) at −78° C. After completion of the addition, the mixture was stirred for 1.5 hours at −78° C. Then triisopropyl borate (277 g, 1.47 mol) was added and the mixture was gradually warmed to room temperature and stirred overnight. Saturated aqueous ammonium chloride solution (1 L) was added drop-wise, while keeping the temperature of the reaction mixture below 10° C. The resulting mixture was acidified to a pH of approximately 6 with 1 N aqueous hydrochloric acid. The organic phase was separated and the aqueous phase was extracted with ethyl acetate (3×1 L). The combined organic layers were washed with saturated aqueous sodium chloride solution, dried over sodium sulfate, and filtered; and the solvent was removed under reduced pressure. The residue was washed with petroleum ether (3×300 mL) and the resulting solid was dried under vacuum to afford the product as a white solid. Yield: 157 g, 1.25 mol, 93%. 1H NMR (400 MHz, DMSO-d6) δ 3.97 (s, 3H), 6.72-6.74 (m, 1H), 7.34-7.36 (m, 1H), 8.35 (br s, 2H).

Quelle