1. In 250 mL of glacial acetic acid, 3,4-dimethylphenylhydrazine hydrochloride (17.7 g, 0.1 mol), ethyl acetoacetate (13.0 g, 0.1 mol), and sodium acetate (8.2 g, 0.1 mol) were added, and mixed with stirring.
2. The reaction mixture was heated to reflux for 24 hours.
3. After completion of the reaction, the mixture was cooled and the solvent was removed by evaporation.
4. The residue was dissolved in 1 L of ether and washed carefully with saturated aqueous sodium bicarbonate (5 x 200 mL).
5. The ether layer was separated and the ether was removed by evaporation to afford the target product 2-(3,4-dimethylphenyl)-1,2-dihydro-5-methyl-1H-pyrazol-3-one (15.4 g, 76% yield). 6. The product was subjected to 1H NMR.
6. The product was confirmed by 1H NMR (300 MHz, d6-DMSO) and mass spectrometry (ES) with the following characterization data: 1H NMR δ 11.30 (br s, 1H), 7.49 (d, J = 1.4 Hz, 1H), 7.43 (dd, J = 8.2 Hz, 1H), 7.14 (d, J = 8.2 Hz, 1H), 5.31 (s, 1H ), 2.20 (s, 3H), 2.22 (s, 3H), 2.08 (s, 3H); MS (ES) m/z 203 [M + H].
