[F:1][C:2]1[CH:7]=[CH:6][C:5]([N:8]2[C:12]([C:13]3[CH:18]=[CH:17][C:16]([S:19][CH3:20])=[CH:15][CH:14]=3)=[CH:11][C:10](N)=[N:9]2)=[CH:4][CH:3]=1.N(OC(C)(C)C)=O>C(#N)C.O1CCOCC1>[F:1][C:2]1[CH:3]=[CH:4][C:5]([N:8]2[C:12]([C:13]3[CH:18]=[CH:17][C:16]([S:19][CH3:20])=[CH:15][CH:14]=3)=[CH:11][CH:10]=[N:9]2)=[CH:6][CH:7]=1A mixture of 1-(4-fluorophenyl)-5-[4-(methylthio)-phenyl]pyrazol-3-amine (3 g), cupric chloride (1.6 g) and t-butyl nitrite (1.14 g) in acetonitrile (50 ml) and dioxane (20 ml) was stirred at ambient temperature for 4 hours. The insoluble was filtered, and to the filtrate were added ethyl acetate and water. The organic layer was separated, washed with dilute hydrochloric acid, dried and concentrated. The oily residue (3.8 g) was purified by column chromatography on silica gel (40 g) eluting with a mixture of toluene and ethyl acetate (10:1) to give a brown oil of 1-(4-fluorophenyl)-5-[4-(methylthio)phenyl]-pyrazole (1.4 g).
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