FIPRONIL INSECTICIDE - NOVEL PHOTOCHEMICAL DESULFINYLATION WITH RETENTION OF NEUROTOXICITY

Fipronil is an outstanding new insecticide for crop protection with go od selectivity between insects and mammals, The insecticidal action in volves blocking the gamma-aminobutyric acid-gated chloride channel wit h much greater sensitivity of this target in insects than in mammals, Fipronil contains a trifluoromethylsulfinyl moiety that is unique amon g the agrochemicals and therefore presumably important in its outstand ing performance, me find that this substituent unexpectedly undergoes a novel and facile photoextrusion reaction on plants upon exposure to sunlight, yielding the corresponding trifluoromethylpyrazole, i.e., th e desulfinyl derivative, The persistence of this photoproduct and its high neuroactivity, resulting from blocking the gamma-aminobutyric aci d-gated chloride channel, suggest that it may be a significant contrib utor to the effectiveness of fipronil, In addition, desulfinylfipronil is not a metabolite in mammals, so the safety evaluations must take i nto account not only the parent compound but also this completely new environmental product.