The present invention relates to a process for the sulfinylation of a pyrazole derivative, characterized in that 5-amino-1-[2,6-dichloro-4-(trifluoromethyl)phenyl]-1H-pyrazole-3-carbonitrile (II) is reacted with a sulfinylating agent selected from trifluoromethylsulfinic acid, trifluoromethylsulfinic acid anhydride, and a trifluoromethylsulfinate alkaline or alkaline earth metal salt and mixtures of the acid and/or the salt(s), in the presence of at least one amine acid complex wherein the amine(s) are selected from tertiary amines and the acid(s) are selected from hydrofluoric, hydrochloric, hydrobromic and hydroiodic acid and sulfonic acid derivatives, and with the addition of a halogenating agent.本發明係關於一種亞磺醯化吡唑衍生物之方法，其特徵在於使5－胺基－1－[2,6－二氯－4－(三氟甲基)苯基]－1H－吡唑－3－腈(II)與選自三氟甲基亞磺酸、三氟甲基亞磺酸酐及三氟甲基亞磺酸鹼金屬或鹼土金屬鹽，及酸及/或鹽之混合物的亞磺醯化劑在至少一種胺酸錯合物存在下及在添加鹵化劑之情況下反應，其中胺係選自三級胺且酸係選自氫氟酸、氫氯酸、氫溴酸及氫碘酸及磺酸衍生物。
