反应详情

102 g (2-nitrophenyl)hydrazine and 142 g (Ethoxymethylene)propanedioic acid, diethyl ester are dissolved in 300 ml ethanol and refluxed for 20 hours. After cooling the clear red solution is evaporated and the solvent distilled off. The remaining crystalline residue (168 g) is added to 400 g PPA (polyphosphoric acid) at a temperature of 80° C. The reaction is completed by heating the solution for 10 minutes to 120° C. The solution is then immediately poured on 2 kg ice and stirred for 30 minutes. After filtration the residue is recrystallized from n-propanol to yield 80 g of 5-hydroxy-1-(2-nitrophenyl)-1H-pyrazole-4-carboxylic acid, ethyl ester with a melting point of 157°-160° C.; yellow crystals.

1. temperaturerefluxed for 20 hours
2. temperatureAfter cooling the clear red solution
3. customis evaporated
4. distillationthe solvent distilled off
5. additionThe remaining crystalline residue (168 g) is added to 400 g PPA (polyphosphoric acid) at a temperature of 80° C
6. temperatureby heating the solution for 10 minutes to 120° C
7. additionThe solution is then immediately poured on 2 kg ice
8. filtrationAfter filtration the residue
9. customis recrystallized from n-propanol