A solution of 1-(2,6-dichloro-4-trifluoromethylphenyl)-3,5-dimethyl4-iodopyrazole (1 g) in dimethylformamide (10 ml) containing yinyltri-n-butyltin (2 ml) and tetrakis(triphenylphosphine)palladium(0) (0.1 g) was stirred at 75° C. for 2 hours then left overnight at room temperature. The mixture was again heated at 75° C. for 2 hours then vinyltri-n-butyltin (2 ml) was added and the mixture heated at 75° C. for 2 hours. Tetrakis(triphenylphosphine)palladium(0) (0.1 g) was added and heating continued for a further 2 hours. The reaction mixture was evaporated and the residue partitioned between water and dichloromethane. The organic layer was separated, washed with water (×2), then brine, dried (Na2SO4) and evaporated. The residue was adsorbed onto silica gel (20 g) and purified by column chromatography on silica gel (150 g) eluted with hexane, then hexane with increasing amounts of dichloromethane and finally dichloromethane. Combination and evaporation of suitable fractions provided the title compound as yellow oil.
