4-Methylpyrazole → 1-Ethylpyrazole-5-boronic acid, pinacol ester

HRID 1845415Notizen

Reaktionsgleichung

Reaktionsgleichung von HRID 1845415
C[C:2]1[CH:3]=[N:4][NH:5][CH:6]=1.[Li][CH2:8][CH2:9]CC.C(O[B:16]1[O:20][C:19]([CH3:22])([CH3:21])[C:18]([CH3:24])([CH3:23])[O:17]1)(C)C>[NH4+].[Cl-]>[CH2:8]([N:5]1[C:6]([B:16]2[O:20][C:19]([CH3:22])([CH3:21])[C:18]([CH3:24])([CH3:23])[O:17]2)=[CH:2][CH:3]=[N:4]1)[CH3:9]

Komponenten

5

Edukt 3

HCID 34064-MethylpyrazoleHCID 50177412-Isopropoxy-4,4,5,5-tetramethyl-1,3,2-dioxaborolaneHCID 178418339Butyllithium

Produkt 1

HCID 532172521-Ethylpyrazole-5-boronic acid, pinacol esterAusbeute 89 %

Reagenzien, Katalysatoren, Lösungsmittel 1

HCID 25517Ammonium ChlorideLösungsmittel

Versuchsvorschrift

At 0° C., to above solution of 4-methylpyrazole (˜50 mmol) was added n-BuLi (2.5M in hexane, 22 mL, 55 mmol). The reaction solution was stirred for 1 hour at RT and then cooled to −78° C. [J. Heterocyclic Chem. 41, 931 (2004)]. To the reaction solution was added 2-isopropoxy-4,4,5,5-tetramethyl-1,3,2-dioxaborolane (10.2 g, 55 mmol). After 15 min at −78° C., the reaction was allowed to warm to 0° C. over 1 hour. The reaction was diluted with saturated NH4Cl solution and extracted with DCM. The organics were dried over Na2SO4 and concentrated under vacuum to afford a tan solid (9.8 g, 89%) which was used without further purification. LCMS (ES) m/z 141 (M+H)+for [RB(OH)2]; 1H NMR (CDCl3, 400 MHz) δ ppm 7.52 (d, J=2 Hz, 1H), 6.36 (d, J=2 Hz, 1H), 4.48 (q, J=7.2 Hz, 2H), 1.44 (t, J=7.2 Hz, 3H), 1.36 (s, 12H)

Aufarbeitung

  1. waitAfter 15 min at −78° C.
  2. temperatureto warm to 0° C. over 1 hour
  3. extractionextracted with DCM
  4. dry with materialThe organics were dried over Na2SO4
  5. concentrationconcentrated under vacuum

Quellen und Nachweise

ORD-Eintrag
ord-5122928f387b456cbd8e9f73d12f144e
Quelldatensatz
uspto-grants-2015_02
Patentnummer
US08946278B2

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