Reaktion #733821

Reaktionsgleichung

diethyl maleate

sodium ethoxide

acetic acid

3-chloro-2(1H)-pyridinone hydrazone

→

title product

ethyl 2-(3-chloro-2-pyridinyl)-5-oxo-3-pyrazolidine-carboxylate

Lösungsmittel

water

ethanol

Reaktionsbedingungen

Aufarbeitung

1. 1
   SonstigeA 2-L four-necked flask equipped with a mechanical stirrer
2. 2
   workup.ADDITIONthermometer, addition funnel
3. 3
   Temperaturreflux condenser, and nitrogen inlet
4. 4
   TemperaturThe mixture was heated
5. 5
   TemperaturThe mixture was re-heated
6. 6
   Temperaturto reflux over a period of 5 minutes
7. 7
   TemperaturThe reflux rate increased markedly during the addition
8. 8
   workup.ADDITIONBy the end of the addition all of the starting material
9. 9
   workup.DISSOLUTIONhad dissolved
10. 10
    Temperaturat reflux for 10 minutes
11. 11
    TemperaturAfter being cooled to 65° C.
12. 12
    SonstigeA precipitate formed
13. 13
    workup.DISSOLUTIONto dissolve
14. 14
    TemperaturThe orange solution was cooled in an ice bath
15. 15
    Sonstigeto precipitate at 28° C
16. 16
    SonstigeThe product was isolated via filtration
17. 17
    Waschenwashed with aqueous ethanol (40%, 3×50 mL)
18. 18
    Sonstigeair-dried on the
19. 19
    Filtrationfilter for about 1 hour

Vorschrift

A 2-L four-necked flask equipped with a mechanical stirrer, thermometer, addition funnel, reflux condenser, and nitrogen inlet was charged with absolute ethanol (250 mL) and an ethanolic solution of sodium ethoxide (21%, 190 mL, 0.504 mol). The mixture was heated to reflux at about 83° C. It was then treated with 3-chloro-2(1H)-pyridinone hydrazone (68.0 g, 0.474 mol). The mixture was re-heated to reflux over a period of 5 minutes. The yellow slurry was then treated dropwise with diethyl maleate (88.0 mL, 0.544 mol) over a period of 5 minutes. The reflux rate increased markedly during the addition. By the end of the addition all of the starting material had dissolved. The resulting orange-red solution was held at reflux for 10 minutes. After being cooled to 65° C., the reaction mixture was treated with glacial acetic acid (50.0 mL, 0.873 mol). A precipitate formed. The mixture was diluted with water (650 mL), causing the precipitate to dissolve. The orange solution was cooled in an ice bath. Product began to precipitate at 28° C. The slurry was held at about 2° C. for 2 hours. The product was isolated via filtration, washed with aqueous ethanol (40%, 3×50 mL), and then air-dried on the filter for about 1 hour. The title product compound was obtained as a highly crystalline, light orange powder (70.3 g, 55% yield). No significant impurities were observed by 1H NMR.

Quelle