To a stirred solution of 4-allyloxy-5-(4-chlorophenyl)-1-(2-chlorophenyl)-1H-pyrazole-3-carboxylic acid ethyl ester I-1e (337 mg, 0.8 mmol) osmium tetroxide (53 microliters of a 0.15 M solution in water) and N-methylmorpholine-N-oxide (120 mg, 0.9 mmol) in dioxane (2.4 ml)/water (0.6 ml) was stirred at ambient temperature for 18 hours, then sodium periodate (1.7 g, 8.1 mmol) was added and stirring was continued for 3.5 hours. The thick slurry was diluted with ethyl acetate (100 ml), filtered and solids washed 2× with ethyl acetate. The combined filtrates were washed with water, brine, dried (Na2SO4) and concentrated in vacuo to afford an oil. Silica gel chromatography (25% ethyl acetate/hexanes) afforded the title compound (I-1f) as a colorless foam, 130 mg.
