[NH:1]1[CH:5]=[CH:4][CH:3]=[N:2]1.[F:6][C:7]1[CH:12]=[C:11]([F:13])[CH:10]=[CH:9][C:8]=1[C:14](=[O:17])[CH2:15]Cl.O>CC(C)CC(=O)C>[F:6][C:7]1[CH:12]=[C:11]([F:13])[CH:10]=[CH:9][C:8]=1[C:14](=[O:17])[CH2:15][N:1]1[CH:5]=[CH:4][CH:3]=[N:2]1A mixture of 1H-pyrazole (1.3 mol) in 4-methyl-2-pentanone (500 ml) was stirred and refluxed. 1-(2,4-difluorophenyl)-2-chloroethanone (0.26 mol) dissolved in 4-methyl-2-pentanone (500 ml) was added dropwise and the mixture was stirred and refluxed for 3 h. The mixture was cooled, poured into water and separated. The organic layer was evaporated. The residue was stirred up in HCl/water, filtered off and washed with water. The precipitate was stirred up in hexane, filtered off and dried in vacuo at 45° C., yielding 45 g (78%) of 1-(2,4-difluorophenyl)-2-(1H-pyrazol-1-yl)ethanone; mp. 76.4° C. (interm. 12).
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