Ethyl orthoformate → 3-Cyano-1-(2,6-dichloro-4-trifluoromethylphenyl)-5-ethoxymethylideneamino-4-trifluoromethylsulfinylpyrazole

Participants

Reaction Steps

A 12-L three-necked flask fitted with an overhead stirrer, heating mantle, water separator (e.g. Dean Stark trap) with condenser was placed under a nitrogen atmosphere and charged with 1.475 kg (3.37 moles) of fipronil and 6 L of triethyl orthoformate. The suspension was heated to reflux over 2.5 h, then at reflux for 3 h with collection and removal of the distillate. The mixture was cooled to room temperature, then evaporated under reduced pressure at a bath temperature of 60-80° C., then at 50° C. overnight. The resulting beige solid, 1.717 kg (95.8% by HPLC, 3.335 moles, 99% purity corrected yield) was used without further purification (m.p. about 63° C.).

Provenance & Evidence