A mixture of 3-acetyl-1-(4-fluorophenyl)-5-[4-(methylsulfonyl)phenyl]pyrazole (1.1 g), thallium (III) nitrate trihydrate (1.6 g) and perchloric acid (70%; 3.3 ml) in methanol (16 ml) and dioxane (8 ml) was stirred at ambient temperature overnight. The insoluble was filtered, and the filtrate was diluted with chloroform, washed with water, dried and concentrated. The residue (1.6 g) was purified by column chromatography on silica gel (100 g) eluting with a mixture of toluene and ethyl acetate (2:1) to give pale brown crystals of 1-(4-fluorophenyl)-3-(methoxyacetyl)-5-[4-(methylsulfonyl)phenyl]pyrazole (0.13 g).
