A mixture of 4.8 g (36 mmol) 2,4,6-trifluoropyridine, 19.8 g (119 mmol) 5-hydroxy-1-methyl-3-trifluoromethylpyrazole and 18.1 g (131 mmol) potassium carbonate in 25 ml anhydrous sulfolane is stirred and heated to 80° C. over a period of 3 days. After cooling, the mixture is diluted with pentane/ethyl acetate (by volume ration 1/1) and filtered through a bed of silica gel. The filtrate is washed 10 times with water and the organic layer is dried over magnesium sulfate. After removal of the solvents, the residue is washed with isopropyl ether and 19.1 g (93 % yield) colorless crystals of melting point 130 0C are obtained.
