P(Cl)(Cl)(Cl)=O.[CH3:6][C:7]1[CH:8]=[C:9]([N:14]2[C:18](=[O:19])[CH:17]=[C:16]([CH3:20])[NH:15]2)[CH:10]=[CH:11][C:12]=1[CH3:13].O.CN(C)[CH:24]=[O:25]>>[CH3:6][C:7]1[CH:8]=[C:9]([N:14]2[C:18]([OH:19])=[C:17]([CH:24]=[O:25])[C:16]([CH3:20])=[N:15]2)[CH:10]=[CH:11][C:12]=1[CH3:13]Phosphorus oxychloride (4.82 mL, 51.6 mmol) was added dropwise to an ice-cooled, stirred suspension of 1-(3,4-dimethylphenyl)-3-methyl-3-pyrazolin-5-one (8.70 g, 43.0 mmol) in dimethylformamide (18.0 mL) at such a rate as to maintain the temperature below 20° C. After the addition, the mixture was heated at 100° C. for 2 h, then cooled, poured into iced water (200 mL). The resulting mixture was stirred for 18 h, then filtered. The solid was washed with water and dried to give the title compound (7.83 g, 79%) as a cream-coloured powder. MS (ES) m/e 231 [M+H]+.
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