反应详情

To a solution of 1-benzylhydrazine dihydrochloride (Aldrich, 0.98 g, 5.0 mmol) in EtOH (30 mL) were added DIEA (2.0 mL) and ethyl 2,4-dioxopentanoate (0.70 mL, 5.0 mmol). The mixture was stirred at room temperature for 12 h and was concentrated in vacuo. The residue was dissolved in 1 N NaOH (10 mL). The solution was heated at 60° C. for 1 h. After cooling down, the solution was extracted with DCM (3×50 mL). The aqueous layer was neutralized to pH 2.0 and then was extracted with EtOAc. The organic layer was washed with brine and dried over MgSO4. It was filtered and concentrated to give 1-benzyl-5-methyl-1H-pyrazole-3-carboxylic acid (1.0 g, 92% yield). MS (ESI+): m/z 217.12 (M+H)+.

1. concentrationwas concentrated in vacuo
2. dissolutionThe residue was dissolved in 1 N NaOH (10 mL)
3. temperatureThe solution was heated at 60° C. for 1 h
4. temperatureAfter cooling down
5. extractionthe solution was extracted with DCM (3×50 mL)
6. extractionwas extracted with EtOAc
7. washThe organic layer was washed with brine
8. dry with materialdried over MgSO4
9. filtrationIt was filtered
10. concentrationconcentrated