Pyrazole pyrethroids

The insecticidal activity and structure-activity relationships of novel pyrethroids prepared by reacting methyl phenyl substituted pyrazole methanols with dichloro chrysanthemic acid chloride are reported. These pyrethroids are active on tobacco budworm, fall armyworm, southern corn rootworm, and aster leafhopper, generally in the concentration range of 1000-250 ppm. Although less active than the pyrethroid standard bifenthrin, the overall structure-activity of these pyrazole pyrethroids with regard to substitution patterns is similar to that previously observed with bifenthrin analogs. 

Schemes I-IV illustrate the syntheses of the pyrazole pyrethroids reported here. In scheme-I, condensation of ethyl ethoxy-methyl eneacetoacetate (3) (6) and ethyl ethoxymethylenetrifluoro-acetoacetate (4) (7) with phenyl hydrazine in glacial acetic acid initially at room temperature followed by heating at reflux gave the pyrazolecarboxylates 5 (8) and 6 in yields of 43 and 70%, respectively. Reduction with lithium aluminum hydride gave the alcohols 7 and 8 which were then allowed to react with the DV-acid chloride in Et3N/THF to give the pyrethroid isomer mixtures 9 (2) and 10 (4 3 trans/cis) in 80-85% yield from the carboxylates. Pyrethroid 10 was prepared to determine how the increased lipophilicity over 9 affected insecticidal activity.

Synthesis and Insecticidal Activity of Pyrethroids from Substituted Pyrazole Methanol Precursors... 

Reported here is the synthesis and insecticidal activity of some related pyrethroids represented by general formula 2 prepared by condensing methyl phenyl substituted pyrazole methanols with the more readily available dichloro chrysanthemic acid chloride (DV-acid Chloride). All of the pyrethroid samples were also prepared and tested as approximately a 4 3 trans/cis mixture of isomers. 

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