A solution containing 164 mg of 5-(3,5-dichloro-phenylsulphanyl)-3-methyl-1-phenyl-1H-pyrazole-4-carbaldehyde, 103 mg of diethyl benzylphosphonate and 27 mg of sodium hydride (60% in mineral oil) in 5 ml of anhydrous tetrahydrofuran was stirred under nitrogen at rt for 16 h. The solvent was evaporated and the residue was purified by flash chromatography on silica gel using ethyl acetate/petroleum spirit 40°-60° C. (1:10) for the elution to give 162 mg of 5-(3,5-dichlorophenylthio)-3-methyl-1-phenyl-4-styryl-1H-pyrazole as a pale yellow solid. Mass spectrum (EI) m/z 436 [M]+.
