Reaktion #339212

Reaktionsgleichung

HMPA

HMPA

4-oxo-piperidine-1-carboxylic acid benzyl ester

dibromodifluoromethane

→

4-difluoromethylene-piperidine-1-carboxylic acid benzyl ester

Ausbeute 56.0%

Lösungsmittel

THF

Reaktionsbedingungen

Aufarbeitung

1. 1
   SonstigeThe cooling bath was removed
2. 2
   Temperaturthe mixture was heated
3. 3
   Temperaturat reflux for 18 h
4. 4
   Waschenthe residue was washed with diethyl ether several times
5. 5
   WaschenThe combined ether washings were washed successively with saturated aqueous copper (II) sulphate, brine
6. 6
   Trocknendried over Na2SO4
7. 7
   Einengenconcentrated
8. 8
   Sonstigepurification by chromatography (20% EtOAc-hexanes)

Vorschrift

To a solution of 4-oxo-piperidine-1-carboxylic acid benzyl ester (0.50 g, 2.14 mmol, 1.0 eq.) in THF (20 mL) was added dibromodifluoromethane (0.90 mL, 4.5 eq.) at −30° C. followed by HMPA (1.75 mL, 4.5 eq.). The cooling bath was removed and the reaction mixture was swirled periodically. After 30 min, zinc dust (0.63 g, 4.5 eq.) and HMPA (80 μL 0.4 eq.) was added and the mixture was heated at reflux for 18 h. Upon cooling to room temperature, the residue was washed with diethyl ether several times. The combined ether washings were washed successively with saturated aqueous copper (II) sulphate, brine, dried over Na2SO4 and concentrated. The residue was purification by chromatography (20% EtOAc-hexanes) to afford 4-difluoromethylene-piperidine-1-carboxylic acid benzyl ester (0.32 g, 56%) as a colorless oil.

Quelle