[Cl:1][C:2]1[CH:7]=[CH:6][C:5]([N:8]2[C:12](=O)[C:11]3[CH2:14][CH2:15][CH2:16][C:10]=3[NH:9]2)=[C:4]([F:17])[CH:3]=1.P(Br)(Br)([Br:20])=O.C(N(CC)C1C=CC=CC=1)C.[OH-].[Na+]>O.CN(C)C=O>[Br:20][C:12]1[N:8]([C:5]2[CH:6]=[CH:7][C:2]([Cl:1])=[CH:3][C:4]=2[F:17])[N:9]=[C:10]2[CH2:16][CH2:15][CH2:14][C:11]=12
A mixture of 6.3 parts of 2-(4-chloro-2-fluorophenyl)-1,4,5,6-tetrahydrocyclopentapyrazol-3(2H)-one, 7.9 parts of phosphorous oxybromide, 3.7 parts of N,N-diethylaniline and 10 parts of N,N-dimethylformamide was refluxed 24 hours and poured into 100 parts of water. After neutralizing with 50% aqueous sodium hydroxide solution, the mixture was extracted twice with 100 parts of diethyl ether. The ether extract was dried over anhydrous magnesium sulfate and the solvent was removed under a reduced pressure of 100 mm. Hg at ambient temperature. The crude product was recrystallized from ethanol-water to yield 2.1 parts of 3-bromo-2-(4-chloro-2-fluorophenyl)-2,4,5,6-tetrahydrocyclopentapyrazole melting at 106°-110°.
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