At room temperature, initially 4.00 g (12 mmol) of 2-chloro-3-(5-methyl-4,5-dihydroisoxazol-3-yl)-4-methylsulfonylbenzoyl chloride in 50 ml of dioxane and then 1.20 g (12.2 mmol) of triethylamine in 30 ml of dioxane were added dropwise to a solution of 1.20 g (12 mmol) of 5-hydroxy-1-methylpyrazole in 30 ml of dioxane. The reaction mixture was stirred for 12 hours and then filtered through silica gel and the filtrate was admixed with 0.50 g (3.6 mmol) of potassium carbonate and heated under reflux for 12 hours. After a further 12 hours of stirring at room temperature, a spatula tipful of potassium carbonate was added, and the mixture was once again heated under reflux. After cooling, the solvent was distilled off under reduced pressure, the residue was taken up in water and washed with ethyl acetate, the pH was adjusted to 1-2 using 10% strength hydrochloric acid and the mixture was extracted repeatedly with ethyl acetate. The combined organic phases were washed with water and dried and the solvent was removed. The residue was digested in cold ethyl acetate. 1.60 g (34% of theory) of 4-[2-chloro-3-(5-methyl-4,5-dihydroisoxazol-3-yl)-4-methylsulfonylbenzoyl]-5-hydroxy-1-methyl-1H-pyrazole were obtained.
