CS254527B1 - Insecticidal agent - Google Patents

Abstract

Insecticidal composition based on a mixture of isomers of alpha-cyano-3-phenoxybenzyl ester of 2,2-dimethyl-3-(2,2-dichlorovinyl)-cyclopropanecarboxylic acid of formula I consists in that it contains stereoisomers of absolute configuration IR, 3R, alpha-S, 1R,3S, alpha-.S and 1R,3S, alpha-R in a ratio of 1.8 to 2.2:0.8 to 1.2:0.8 to 1.2.

Description

The invention relates to an insecticidal composition.

It is known that some cyclopropanoic acid esters exhibit significant insecticidal activity. The possibility of using 2,2-dimethyl-3-(2,2-dichlorovinyl)cyclopropanecarboxylic acid esters as insecticidal agents was first proposed by Czech authors (J. Farkaš, F. Šorm: Colleotion Czech. Chem. Commun. 22, 2 230, 1959). Their work initiated further extensive research, the result of which was the synthesis of alpha-cyano-3-phenoxybenzyl ester of 2,2-dimethyl-3-(2,2-dichlorovinyl)cyclopropanecarboxylic acid of formula I with extraordinary insecticidal activity (K. Naumann: Chemie der syntetischen Pyrethroid-Insektizide, p. 10, Springer Verlag, Berlin, 1981).

This substance, also known by the technical name Cypermethrin, contains three asymmetric carbons in the molecule, designated in formula I by the Arabic numerals 1 and 3 on the cyclopropane ring and the Greek letter alpha on the benzyl carbon, which allows the existence of a total of eight separate stereoisomers, differing from each other in absolute configuration and, if necessary, also in the geometric arrangement of the substituents (cis or trans) on the cyclopropane ring. The following notation is used in this document to describe these stereoisomers:

Isomer configuration

A IR, 3R, alpha-S B IR, 3R, alpha-R C . IR, 3S, alpha-S D IR, 3S, alpha-R E 1S, 3S, alpha-S F is. 3S, alpha-R G 1S, 3R, alpha-S H 1S, 3R, alpha-R

The insecticidal activity of the individual isomers of the compound of formula I is only partially known. However, some results of biological tests show (e.g. P. Ackermann, F. Bourgeouis, J. Drábek: Pestic. Sci. 11, 169 (1980)) that there may be differences of several orders of magnitude between the individual stereoisomers. The activity found decreases in the order of stereoisomers A C B D E, F, G, H.

Although the above ranking provides some guidance for the formulation of an optimal insecticidal composition based on the substance of formula I, it is necessary to simultaneously take into account other important factors, in particular *

a) existing possibilities for stereoselective synthesis of the most effective isomers or their mixtures,

b) economic aspects of such stereoselective synthesis,

c) the possibility of mutual synergistic or antagonistic effects of the different isomers present in the mixture.

The importance of these factors will be partly apparent from the following overview of the current state of the art: Most of the syntheses of the compound of formula I described so far are non-stereoselective or the formation of less effective isomers predominates (see e.g. K. Naumann: Chemie der synthetichen Pyrethroid-Insektizide, p. 23 et seq., Springer Verlag, Berlin, 1981).

Therefore, the production of a mixture of all eight stereoisomers of formula I, in which the individual isomers are contained in approximately statistical proportions, still prevails in the world. Only recently have methods been found for the stereoselective and economical preparation of a mixture consisting of the enantiomeric pair of isomers A and F in a ratio of 1:1, and their production has begun on a technical scale. However, the results of tests of the insecticidal efficacy of the above mixture of isomers A and F are probably not entirely satisfactory, since in at least two cases a significant effect of the antagonism factor between these two isomers was found, reducing the insecticidal efficacy of the composition (M. Elliott, A.W. Farnham, N.J. Jones, D.M. Doderlund: Pestic. Sci. 9, 112, (1978)).

The resulting effects of synergistic and antagonistic factors in a mixture of isomeric insecticides cannot be predicted based on current knowledge of the art. The results of some tests show that in a mixture of eight isomers of the substance of formula I, antagonistic factors are not significantly manifested and in some situations synergistic factors may prevail (see, for example, I.A. Black et al., Proc.

BCPC, Brighton, Conf. 1979, p. 377).

An antagonistic effect similar to that found for the mixture of isomers A and F has also been demonstrated for the isomers of deltamethrin (M. Elliott et al., Pestic. Sci. 9, 112, 1978). Similar facts have been demonstrated for resmethrin and allethrin (J.C. Wickham: Pestic. Sci. 7, 273, 1976). On the contrary, a synergistic factor has been found for mixtures of optical isomers of other pyrethroids (M. Ohno et al., Pestic. Sci. 7, 241, 1976).

The above disadvantages are eliminated by an insecticidal composition containing a mixture of isomers of formula I according to the invention, the essence of which is that it consists of isomers A, C and D of the absolute configuration IR, 3R, alpha-S, IR, 3S, alpha-S and IR, 3S, alpha-R in the ratio of 1.8 to 2.2:0.8 to 1.2:0.8 to 1.2. In a number of tests, it shows higher insecticidal efficacy than the above-mentioned mixture of isomers A and F, although both compared mixtures contain the same proportion of the most effective stereoisomer A (about 50%). It was further found that in the new mixture of isomers A, C and D the antagonism factor bu3 does not apply at all, or is outweighed by the action of the synergistic factor.

These findings are clearly surprising, as they indicate the action of factors unforeseeable in the light of the state of the art. At the same time, these findings show that the efficacy of a given mixture of stereoisomers of formula I cannot be satisfactorily assessed on the basis of knowledge of the efficacy of the individual isomers, but must always be considered as an integral whole.

The insecticidal composition according to the invention can be used in any formulation in a known manner of application of natural or synthetic pyrethroid insecticides. In addition to the active substance, the composition can contain a carrier, a non-ionic surfactant and conventional synergistic compounds. The composition can be applied in various ways, for example in the form of a dust, granulate, suspension, emulsion, solution, aerosol, etc. Depending on the method of application, either a liquid carrier can be selected, such as water, alcohols, hydrocarbons or other organic solvents, mineral, vegetable or animal oil, or a solid carrier can be selected, such as talc, clay, silica gel, kaolin, perlite and the like.

The compositions preferably contain 0.005 to 10% by weight of active ingredient. The compositions can be advantageously used for controlling insects, particularly in agriculture, fruit growing, forestry, veterinary applications and in households.

Example

Insecticidal efficacy

The activity on individual organisms was monitored for five isomeric mixtures or isomers of the ester of formula I. The composition of the individual mixtures was designated as follows:

Substance 1 isomer A

Substance 2 50%A+50%F (Alfamethrin)

Substance 3 50% A + 25% C + 25% D

Substance 4 50% A + 50% E

Substance 5 25% each of isomers A, Β, E, F.

The composition of the active substance was determined using high-performance liquid chromatography. A 25x0.5 cm Spherisorb S5CN column was used; eluent n-hexane - 0.2% tetrahydrofuran. The individual components of the active substance are completely separated under these conditions. At a flow rate of 2 ml/min and a temperature of 25 °C, they have the following typical retention times: 16 min (IR, 3R, alpha S isomer); 17.5 min. (IR, 3S, alpha R isomer) and 21 min. (IR, 3S, alpha S isomer).

Quantification was performed using the internal standard method (1,3-dichloro-4,6-dinitrobenzene) with an accuracy of ±4%. This methodology revealed that substance 3 contains isomers A, C, D in a ratio of 2:1:1 and substance 4 contains isomers A, E in a ratio of 1:1. and substance 5 contains isomers A, Β, E, F in a ratio of 1:1:1:1. Chemical identification of individual isomers present in the active substance was performed by comparing spectral data (NMR, IC) with authentic samples obtained by known literature procedures.

a) Study of efficacy on houseflies.

The test insects are mixed-sex houseflies. The active substance is administered by topical application of 1 acetone solution to the dorsal thorax of the test insect. 50 insect individuals are used and mortality is determined 24 hours after application. 5 of these determinations are carried out and the lethal dose LD^q is calculated. The doses are given in µg per individual.

Substance 1 2 3 4 5 Dose 10 98% 89% 93% 92% 62 and 2.5 68% 30% 37% 31% 22% 0.5 7 » 2% 5% 3% 1% ^LD50 1.6 3.9 3.6 3.8 7.3

b) Study of efficacy against Spodoptera Littoralis larvae.

The tests were again carried out by topically applying 1 µl of a solution of the active substance in acetone to the dorsal thorax of each individual. Thirty 4th instar caterpillars were used and the LD50 was calculated from 5 consecutive 24 hour mortality determinations.

Substance 1 2 3 4 5 Dose 5 100% 100% 100% 100% 91% 2.5 100% 92% 96% 90% 76% 1.5 95% 80% 84% 79% 54% 0.5 70% 42% 48% 39% 26% ^LD50 0.27 0.65 0.52 0.71 1.35

o) Study of insecticidal efficacy on Phaedon Cochlearie.

The determination was carried out using the described methodology (M. Elliott et al., Pestio. Sel. 9, 112 (1978)) and the relative molar efficiencies thus obtained are:

Claims (1)

object of the invention Insecticidal composition based on a mixture of 2,2-dimethyl-3- (2,2-dichloro-vinyl) -cyclopropanecarboxylic acid alpha-cyano-3-phenoxybenzyl ester isomers of formula I, characterized in that the isomers of absolute configuration IR, 3R, alpha- S, IR, 3S, alpha-S and IR, 3S, alpha-R at a ratio of 1.8 to 2.2: 0.8 to 1.2: 0.8 to 1.2.