Pyrethroids ether type

Conformational Analysis of Fenvalerate and an Ether-Type Pyrethroid... 

In the indoor environment, many types of products such as crystals, sprays and liquids are applied for active and preventative protection of insects. Insect sprays are particularly popular because they are easy to handle and can be combined with air fresheners. Commonly, the amount of active agents in these products is well below 2%. For example, a commercially available insecticide for indoor use may contain 0.25% tetramethrin, 0.05% D-phenothrin and 1% of the synergist pipero-nyl butoxide. Pyrethroids are also used as active agents in liquid products against furniture beetle. In addition, materials containing natural fibers are often equipped with synthetic pyrethroids as a precaution. Apart from the active ingredients, volatile components such as acetone, aliphatic hydrocarbons, cycloalkanes, branched alkanes C3-benzenes and dipropylene glycol monomethyl ether are usually present in insecticides. 

A candidate for the active conformer of esfenvalerate (the most insecticidally active stereo isomer of fenvalerate) has been presented based on conformational analyses using the AMI molecular orbital method and shape comparisons with low activity pyrethroids. Esfenvalerate and a new type pyrethroid, 3-phenoxy-benzyl (R)-2-(4-ethoxyphenyl)-3,3,3-trifluoropropyl ether, which has a configuration opposite to that of esfenvalerate, were reasonably superimposed. 

All six compounds are colorless liquids, soluble in alcohol, petroleum ether, and tetrachloromethane, they are easily oxidized and rapidly lose their activity in light and air and are also sensitive towards moisture and alkali. They are contact poisons that rapidly enter the nervous system and induce the characteristic symptoms in insects (high excitation, followed by impairments of coordination, paralysis, and finally death). The first effect starts rapidly, i.e., the insect is unable to move within a few minutes. This knock-down effect, especially in flies, is only achieved by a few insecticides. However, the dose required for this effect is usually not sufficient to cause death since the active principles of P. undergo rapid detoxification by enzymatic oxidation in the insects, thus some of the afflicted insects can recover. This can be prevented by the addition of synergists or active principles of the phosphoric acid ester and carbamate type. R, especially under the recommended conditions of use, is relatively harmless for humans and warm-blooded animals (birds, mammals). The synthetic pyrethroids, devel-... 

Wether the latest aftermath in pyrethroid research, the non-ester variations of the ether, hydrocarbon or the silane types are sufficiently different or more advantageous to capture market shares has to be shown in the future. 

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