To a rapidly stirred solution of 5-amino-3-cyano-1-(2,6-dichloro-4-trifluoromethylphenyl)-4-iodopyrazole (0.25 g) in toluene (2 ml) containing tetrakis(triphenylphosphine)palladium(0) (0.02 g) was added saturated aqueous sodium hydrogen carbonate solution (1 ml) and a solution of 4-pyridylboronic acid (0.153 g) in ethanol (1 ml). The mixture was heated under reflux for 12 hours, then left at room temperature overnight and then poured into ether (25 ml) and water (25 ml). The organic layer was separated, dried (MgSO4) and evaporated. The residue was taken up the minimum amount of ethyl acetate and purified by chromatography on silica gel (20 g) eluted with dichloromethane:methanol (100:1). Combination and evaporation of suitable fractions followed by recrystallisation from ether/hexane dichloromethane gave the title compound as a white solid, m.p. 226-8° C. (decomp.).
