C[O:2][C:3](=O)[C:4]#[C:5][C:6]1[CH:11]=[CH:10][C:9]([F:12])=[CH:8][CH:7]=1.[CH3:14][NH:15][NH2:16]>CO.O>[F:12][C:9]1[CH:10]=[CH:11][C:6]([C:5]2[N:15]([CH3:14])[NH:16][C:3](=[O:2])[CH:4]=2)=[CH:7][CH:8]=1A suspension of (4-fluorophenyl)propynoic acid methyl ester (1.6 g, 9.0 mmol) in MeOH (10 mL) and H2O (10 mL) was heated at 60° C. and MeNHNH2 (0.5 mL, 9.4 mmol) was added. The reaction mixture was stirred at 60° C. for 20 min. then filtered. The residue was washed with H2O (10 mL) and MeOH (5 mL) and dried to give 5-(4-fluorophenyl)-1-methyl-1,2-dihydro-pyrazol-3-one (0.63 g, 36%). The filtrate was then concentrated under reduced pressure and the residue dissolved in EtOAc (20 ml) and washed with H2O (3×15 mL). The aqueous layer was acidified to pH 5.5 with 2 M citric acid solution (3×15 mL) and extracted with EtOAc (3×20 mL). The extracts were dried (MgSO4) and concentrated under reduced pressure to give 5-(4-fluoro-phenyl)-2-methyl-1,2-dihydro-pyrazol-3-one (0.2 g, 12%).
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