Reaktion #7758

Reaktionsgleichung

2-[2-(4-Fluorophenyl)acetyl]-4-hydroxy-pyrazolidine-1-carboxylic acid benzyl ester

p-nitrophenyl chloroformate

pyridine

→

desired product

Ausbeute 86.0%

2-[2-(4-fluorophenyl)acetyl]-4-(4-nitro-phenoxycarbonyloxy)-pyrazolidine-1-carboxylic acid benzyl ester

Ausbeute 86.0%

Lösungsmittel

dichloromethane

water

Reaktionsbedingungen

Aufarbeitung

1. 1
   workup.STIRRINGStirring
2. 2
   workup.STIRRINGby stirring at room temperature for 12 hours
3. 3
   Extraktionextracted with dichloromethane (40 mL)
4. 4
   WaschenThe organic layer is washed with 0.5 N NaOH (2×40 mL)
5. 5
   ExtraktionThe combined aqueous layers are back-extracted
6. 6
   Extraktionextracted with dichloromethane (30 mL)
7. 7
   WaschenThe combined organic layers are washed with brine (30 mL)
8. 8
   Sonstigedried
9. 9
   Filtrationfiltered
10. 10
    Einengenconcentrated in vacuo
11. 11
    SonstigeThe crude material is purified over silica (3:1 to 2:1 to 1:1 hexane/ethyl acetate)

Vorschrift

2-[2-(4-Fluorophenyl)acetyl]-4-hydroxy-pyrazolidine-1-carboxylic acid benzyl ester, 38, (366 mg, 1.02 mmol) is dissolved in dichloromethane (10 mL). The solution is cooled to 0° C. and p-nitrophenyl chloroformate (411 mg, 2.04 mmol) is added in one portion. The solution is stirred at 0° C., and pyridine (198 μL, 2.45 mmol) added. Stirring is continued at 0° C. for 1 hour followed by stirring at room temperature for 12 hours. The reaction is diluted with water (40 mL) and extracted with dichloromethane (40 mL). The organic layer is washed with 0.5 N NaOH (2×40 mL). The combined aqueous layers are back-extracted extracted with dichloromethane (30 mL). The combined organic layers are washed with brine (30 mL), dried, filtered, and concentrated in vacuo. The crude material is purified over silica (3:1 to 2:1 to 1:1 hexane/ethyl acetate) to afford 462 mg (86% yield) of the desired product as a white foam.

Quelle