Réaction #7758

Équation de réaction

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

p-nitrophenyl chloroformate

pyridine

→

desired product

Rendement 86.0%

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

Rendement 86.0%

Solvants

dichloromethane

water

Conditions de réaction

Traitement

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

Mode opératoire

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.

Source