Synthesis
3,4-Dimethylphenylhydrazine hydrochloride (8.7 g, 50 mmol) was dissolved in 100 mL of glacial acetic acid and ethyl acetoacetate (6.5 g, 50 mmol) and sodium acetate (4.1 g, 50 mmol) were added. The reaction mixture was heated to 120°C and refluxed for 7 h, during which the progress of the reaction was monitored by thin layer chromatography (TLC) until the feedstock was fully reacted. After completion of the reaction, ethyl acetate was removed by evaporation under reduced pressure. 100 mL of water was added to the residue and extracted four times with 100 mL of ethyl acetate. The ethyl acetate layers were combined and concentrated directly under reduced pressure without drying with anhydrous sodium sulfate to afford 1-(3,4-dimethylphenyl)-3-methyl-1H-pyrazol-5(4H)-one (8.3 g, 82% yield).
