Реакция #792174

Уравнение реакции

Potassium persulfate

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

sulfuric acid

→

precipitate

Выход 15.7%

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

Выход 15.7%

Растворители

acetonitrile

Условия реакции

Обработка

1. 1
   ДругоеThe reaction mixture thinned to form a pale green, nearly clear solution
2. 2
   Другоеto form a pale yellow suspension
3. 3
   Температураthe reaction mixture was heated
4. 4
   Температураat gentle reflux for 3.5 hours
5. 5
   ТемператураAfter cooling
6. 6
   Другоеa precipitate of white solid was removed by filtration
7. 7
   workup.ADDITIONThe filtrate was diluted with water (400 mL)
8. 8
   Экстракцияextracted three times with ethyl ether (700 mL total)
9. 9
   Другоеprecipitation of an off-white solid (3.75 g), which
10. 10
    Фильтрацияwas collected by filtration
11. 11
    КонцентрированиеThe ether mother liquor was further concentrated

Методика

To a suspension of ethyl 2-(3-chloro-2-pyridinyl)-5-oxo-3-pyrazolidinecarboxylate (i.e. product of Example 12, 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.

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