Ethyl 2,4-dioxovalerate → 1-Benzyl-5-methyl-1h-pyrazole-3-carboxylate

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Reaction Steps

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)+.

Provenance & Evidence