Abstract: 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 such as boric acid. Also, a process for preparing a compound of formula (II) by adding sulfur dioxide to a mixture of the corresponding disulfide, a formate salt, trifluoromethyl bromide and a polar solvent; and a process for preparing the disulfide comprising adding S2Cl2 to a solution, in an organic solvent, of the corresponding 4-unsubstituted pyrazole.