Process for the preparation of fipronil, an insecticide, and related pyrazoles

摘要

Disclosed is a process for the preparation of 5-amino-1-phenyl-3-cyano-4-trifluoromethyl sulphinyl pyrazoles as defined by Formula-I, wherein: R1 = trifluoromethyl or trifluoromethoxy, and R2 and R3 are individually hydrogen, chlorine or bromine, the process comprising the step of oxidizing a compound of Formula-II wherein: R1 = trifluoromethyl or trifluoromethoxy, R2 and R3 = individually hydrogen, chlorine or bromine, in a medium comprising at least one oxidizing agent and trichloro acetic acid, and/or the reactions product (s) of the at least one oxidizing agent and trichloro acetic acid, and at least one melting point depressant selected from monochloro acetic acid, dichloro acetic acid, methylene dichloride, ethylene dichloride, monochlorobenzene and a haloalkane. Also disclosed are 5-amino-1-phenyl-3-cyano-4-trifluoromethyl sulphinyl pyrazoles as defined by Formula-I obtained by said process.