Reaktion #90231

Reaktionsgleichung

Potassium persulfate

ethyl 2-(3-chloro-2-pyridinyl)-5-oxo-3-pyrazolidinecarboxylate

sulfuric acid

→

precipitate

Ausbeute 15.7%

ethyl 1-(3-chloro-2-pyridinyl)-2,3-dihydro-3-oxo-1H-pyrazole-5-carboxylate

Ausbeute 15.7%

Lösungsmittel

acetonitrile

Reaktionsbedingungen

Aufarbeitung

1. 1
   SonstigeThe reaction mixture thinned to form a pale green, nearly clear solution
2. 2
   Sonstigeto form a pale yellow suspension
3. 3
   Temperaturthe reaction mixture was heated
4. 4
   Temperaturat gentle reflux for 3.5 hours
5. 5
   TemperaturAfter cooling
6. 6
   Sonstigea precipitate of white solid was removed by filtration
7. 7
   workup.ADDITIONThe filtrate was diluted with water (400 mL)
8. 8
   Extraktionextracted three times with ethyl ether (700 mL total)
9. 9
   Sonstigeprecipitation of an off-white solid (3.75 g), which
10. 10
    Filtrationwas collected by filtration
11. 11
    EinengenThe ether mother liquor was further concentrated

Vorschrift

To a suspension of ethyl 2-(3-chloro-2-pyridinyl)-5-oxo-3-pyrazolidinecarboxylate (i.e. product of Example 8, Step A) (27 g, 100 mmol) stirred in dry acetonitrile (200 mL) was added sulfuric acid (20 g, 200 mmol) in one portion. The reaction mixture thinned to form a pale green, nearly clear solution before thickening again to form a pale yellow suspension. Potassium persulfate (33 g, 120 mmol) was added in one portion, and then the reaction mixture was heated at gentle reflux for 3.5 hours. After cooling using an ice bath, a precipitate of white solid was removed by filtration and discarded. The filtrate was diluted with water (400 mL) and then extracted three times with ethyl ether (700 mL total). Concentration of the combined ether extracts to a reduced volume (75 mL) caused precipitation of an off-white solid (3.75 g), which was collected by filtration. The ether mother liquor was further concentrated to yield a second crop of an off-white precipitate (4.2 g), which was also collected by filtration. An off-white solid also precipitated from the aqueous phase; this solid (4.5 g) was collected by filtration to provide a combined total of 12.45 g of the title compound.

Quelle