Reaktion #1673840

Reaktionsgleichung

2-(ethoxymethylene)-2-cyanoacetic acid ethyl ester

2-hydrazinopropionaldehyde diethyl acetal

1-(1-methyl-2,2-diethoxyethyl)-4-ethoxycarbonyl-5-aminopyrazole

→

1-(1-methyl-2,2-diethoxyethyl)-4-carboxy-5-aminopyrazole

Ausbeute 11.0%

Lösungsmittel

ethanol

ethanol

sodium hydroxide

Reaktionsbedingungen

Aufarbeitung

1. 1
   TemperaturThe mixture was refluxed for 4 hours
2. 2
   workup.DISTILLATIONthe solvent was distilled off in vacuo
3. 3
   Sonstigeto give the crude
4. 4
   Temperaturthe mixture was refluxed for 1 hour
5. 5
   TemperaturThe reaction mixture was cooled at room temperature
6. 6
   Waschenwashed with ethyl acetate (100 ml x 2)
7. 7
   FiltrationThe precipitate was collected by filtration
8. 8
   Waschenwashed with water
9. 9
   Trocknendried over phosphorus pentoxide

Vorschrift

To a solution of 2-(ethoxymethylene)-2-cyanoacetic acid ethyl ester (56.3 g) in ethanol (200 ml) was added dropwise 2-hydrazinopropionaldehyde diethyl acetal (54 g) in ethanol (80 ml) at room temperature. The mixture was refluxed for 4 hours. The reaction mixture was cooled at room temperature and the solvent was distilled off in vacuo to give the crude. 1-(1-methyl-2,2-diethoxyethyl)-4-ethoxycarbonyl-5-aminopyrazole (100 g). The crude product (100 g) was dissolved in aqueous 4N-sodium hydroxide (170 ml) and the mixture was refluxed for 1 hour. The reaction mixture was cooled at room temperature and washed with ethyl acetate (100 ml x 2). The aqueous solution was adjusted to pH 3.5 with 6N-hydrochloric acid and stirred for 1 hour. The precipitate was collected by filtration, washed with water and dried over phosphorus pentoxide to give 1-(1-methyl-2,2-diethoxyethyl)-4-carboxy-5-aminopyrazole (9.93 g).

Quelle