A solution of 3-cyano-1-(2,6-dichloro-4-trifluoromethylphenyl)-4-iodopyrazole (58 g) in dimethylformamide (350 ml) containing vinyltri-n-butyltin (1 16 ml) and tetrakis(triphenylphosphine)palladium(0) (3.5 g) was stirred at 75° C. for 3 hours. The reaction mixture was poured into water (600 ml) and ether (600 ml). The organic layer was separated, washed with water (×5), brine (700 ml), dried (Na2SO4) and evaporated. The residue was recrystallised from propan-2-ol to give the title compound as a pale brown solid, m.p.75-6° C.
