Butyl lithium (2.6 ml, 6.6 mmol, 2.5 M solution in hexane) is added to a solution of 1-bromo-4-trifluoromethyl benzene (0.84 ml, 6 mmol) in anhydrous diethyl ether (5 ml) at −30° C. The mixture is stirred for 60 min at −20° C. and for 60 min at 10° C. The solution is allowed to warm to ambient temperature. This solution is then added to a mixture of 4-methyl-2,3,5-trifluoro-6-(3-trifluoromethylphenoxy)pyridine 2A (1.5 g, 5 mmol) in anhydrous diethyl ether (100 ml) at −50° C. during 2.5 hours. The mixture is further stirred for 7 hours at −50° C. and washed with saturated aqueous ammonium chloride and water. After drying and evaporation of the organic layer, the residue is purified by vacuum destillation. One obtains colorless crystals (0.37 g, 0.85 mmol, bp. 130° C. at 0.01-0.02 mbar) of mp. 87° C.
