Process for preparing 4- trifluoromethylsulphinylpyrazole derivative

摘要

A process for the preparation of a compound of formula (I), comprising oxidizing a compound of formula (II) with trifluoroperacetic acid in the presence of a corrosion inhibiting compound selected from boric acid, an alkali metal borate and hydrogen fluoride trapping agent. The compound of formula (II) may be produced by adding sulphur dioxide to a mixture comprising a disulphide of formula (III), a formate salt, trifluoromethyl bromide and a polar solvent. The disulphide of formula (III) may be produced by adding sulphur monochloride to a solution of a compound of formula (IV).