Pyrazole → 1H-Pyrazol-1-ylacetic acid

HRID 25956Notes

Reaction equation

HRID 25956 reaction equation
[NH:1]1[CH:5]=[CH:4][CH:3]=[N:2]1.O1CCCC1.[H-].[Na+].C([O:15][C:16](=[O:19])[CH2:17]Br)C>C(O)C>[N:1]1([CH2:17][C:16]([OH:19])=[O:15])[CH:5]=[CH:4][CH:3]=[N:2]1

Participants

6

Reactant 4

HCID 1048PyrazoleHCID 7748Ethyl bromoacetateHCID 8028Tetrahydrofuran3×HCID 24758Sodium hydride

Product 1

HCID 37174621H-Pyrazol-1-ylacetic acid

Reagents, catalysts & solvents 1

HCID 702EthanolSolvent

Procedure

50 g of pyrazole in 250 ml of abs. tetrahydrofuran is added dropwise in a nitrogen atmosphere within 1/2 hour at 20°-30°, with stirring and cooling, to 38.7 g of sodium hydride in 100 ml of abs. tetrahydrofuran. The reaction mixture is stirred for a further 3 hours at 40°; it is then cooled towards 5° and, with good cooling, 160.7 g of bromoacetic acid ethyl ester in 100 ml of abs. tetrahydrofuran is added dropwise at 0°-10° during 1 hour. Stirring is maintained overnight at room temperature; there is then added dropwise 150 ml of ethanol; stirring is continued for 1 hour, and the suspension is subsequently concentrated by evaporation. To the residue is added a solution of 74 g of NaOH tablets in 600 ml of 60% methanol (aqueous), and refluxing is carried out for 40 minutes. The solution is then cooled, and washed twice with 200 ml of ether. The aqueous phase is made acid to a congo-red indicator (about pH 2) with conc. hydrochloric acid at 5° with cooling, and the solution is continuously extracted during 24 hours with methylene chloride. The extract is concentrated by evaporation, and recrystallised from ether/tetrahydrofuran. The crystals melt at 167°-169°.

Workup

  1. stirringThe reaction mixture is stirred for a further 3 hours at 40°
  2. stirringStirring
  3. stirringstirring
  4. concentrationthe suspension is subsequently concentrated by evaporation
  5. additionTo the residue is added a solution of 74 g of NaOH tablets in 600 ml of 60% methanol (aqueous)
  6. temperaturerefluxing
  7. waitis carried out for 40 minutes
  8. temperatureThe solution is then cooled
  9. washwashed twice with 200 ml of ether
  10. customat 5°
  11. temperaturewith cooling
  12. extractionthe solution is continuously extracted during 24 hours with methylene chloride
  13. concentrationThe extract is concentrated by evaporation
  14. customrecrystallised from ether/tetrahydrofuran
  15. custommelt at 167°-169°

Sources & evidence

ORD record
ord-5c64fe855c04408a91ece6cd7596f509
Source dataset
uspto-grants-1979_04
Patent number
US04147792

Reaction notes

Loading…