Reaktion #94048

Reaktionsgleichung

acetic acid

2-nitrophenylhydrazine

ethoxymethyleneoxalacetic acid ethyl ester

acetic acid

→

1-(2-nitrophenyl)-1H-pyrazole-4,5-dicarboxylic acid, diethyl ester

Reaktionsbedingungen

Aufarbeitung

1. 1
   workup.ADDITIONAfter the addition
2. 2
   Temperaturthe reaction mixture is refluxed for at least 3 hours
3. 3
   TemperaturAfter cooling
4. 4
   workup.DISTILLATIONthe solvent is distilled off first under water vacuum
5. 5
   workup.DISSOLUTIONThe dark, oily residue is dissolved in 20 ml
6. 6
   workup.ADDITIONof ether are added

Vorschrift

5 g. of 2-nitrophenylhydrazine are dissolved in 50 ml. of glacial acetic acid and 7.9 g. of ethoxymethyleneoxalacetic acid ethyl ester in 50 ml. of glacial acetic acid are slowly added dropwise. After the addition has been completed, the reaction mixture is refluxed for at least 3 hours. After cooling, the solvent is distilled off first under water vacuum and then under oil pump vacuum. The dark, oily residue is dissolved in 20 ml. of tetrahydrofuran, 10 ml. of ether are added and the mixture is kept in the refrigerator for 24 hours. The product, 1-(2-nitrophenyl)-1H-pyrazole-4,5-dicarboxylic acid, diethyl ester, is obtained in the form of large crystals, yield 11.5 g. The product is recrystallized from cyclohexane and obtained as yellow crystals; yield 9.8 g., m.p. 45°-46°.

Quelle