The method of obtaining the lambda-cyhalothrin isomerization

 

(57) Abstract:

Describes how to obtain the lambda-cyhalothrin in the form of a racemic modification, containing S--cyano-3-phenoxybenzyl-1R, 3R-3-(Z-2-chloro-3,3,3-Cryptocom-1-EN-1-yl)-2,2-dimethylcyclopropanecarboxylate and its enantiomer, including the processing of cyhalothrin in the form of a mixture of four isomers in approximately equal amounts, which contains two isomers, the components of the lambda cigalotrin and epimer of these two isomers in solution or in suspension in isopropanol, wherein the treatment is carried out in the wet isopropanol, containing 2 to about 15. % of water, sodium cyanide, taken in an amount of 0.5 to 15.0 mol. % the number of cyhalothrin, at a temperature of -10o- +20o. The technical result is simplification. 3 C.p. f-crystals, 1 table.

The invention relates to a method for converting a first isomer to the second isomer, in which the first and second isomers are epimerase the same connection.

Pyrethroids are usually obtained by means of esterification, which give a mixture of isomers. It is known that some isomers have a greater insecticidal effect than others, and this has led to the development of methods to separate the more active isomers and probe N 1582594, European patent N 107296 and U.S. patent N 4997970, and they all differ in the use of reason. However these methods are the basis not only contributes to the desired isomerization by removal of a proton, leading to the epimerization at the carbon atom that carries a cyano group, but also that it is undesirable, can catalyze the decomposition of esters, resulting in a reduced yield of the desired product.

A number of these PYRETHROID products containing only one or two isomers were released on the market. It products such as deltamethrin /S--cyano-3-phenoxybenzyl 1R,3R-/2.2-dibromovinyl /-2,2-dimethylcyclopropane carboxylate/, acrinathrin /S--cyano-3-phenoxybenzyl Z-1R,3S-3- [2-/2,2,2-Cryptor-1-cryptanalytically/vinyl] - 2,2-dimethylcyclopropane carboxylate/, S-fenvalerate /S--cyano-3-phenoxybenzyl S-2-/4-chlorophenyl/-3-methylbutyrate/, and lambda cigalotrin/ racemic combination S--cyano-3 - phenoxybenzyl 1R,3R-3-/Z-2-chloro-3,3,3-Cryptocom-1-EN-1-yl/- 2,2-dimethylcyclopropane of carboxylate and its enantiomer/.

The closest according to the proposed method is a method of obtaining cyhalothrin in the form of crystalline enantiomeric pairs, including the processing of cyhalothrin in the form of a mixture of four isomers, in approx evritania dried, at the temperature of (-10) - (+5)oC, with the addition of crystals of the enantiomeric pair of isomers (see 1225483 A).

According to the present invention proposes a method of obtaining a lambda of cyhalothrin in the form of a racemic modification, containing S--cyano-3-phenoxybenzyl 1R, 3R-3-(Z-2-chloro-3,3,3-Cryptocom-1-EN-1-yl) -2,2-dimethylcyclopropane carboxylate and its enantiomer, including the processing of cyhalothrin in the form of a mixture of four isomers in approximately equal amounts, which contains two isomers, the components of the lambda cigalotrin and epimer of these two isomers in solution or in suspension in isopropanol, the distinguishing feature of which is the fact that what treatment is carried out in the wet isopropanol containing 2 to 15% vol. water, sodium cyanide, taken in an amount of 0.5 - 15 mol.% the number of cyhalothrin, when the temperature - 10...+20oC.

It is preferable to use epimer obtained industrially in a mixture with isomers. While cyanide can be used in solid form or in the form of an aqueous solution in the presence of a catalyst phase transfer

The method of the invention can also be used to obtain deltamethrin, acrinathrin, S-fenvalerate and lambda-cyhalothrin products from PressTV the fear of loss of output due to accelerated basis decomposition. Furthermore, the method reduces the time cycle, indicating that the use of isomerization involving cyanide leads to unexpected significant economic advantage in comparison with known methods of epimerization with the base as a catalyst.

The exact mechanism by which the method of the invention leads to isomerization of epimere the desired isomer and the product is not known, but a possible explanation may be the effect on the carbon atom bearing a cyano, a cyanide ion, a defiant move ceanography mechanism SN2 with concomitant inversion of chirality. Since the isomer of the product is less soluble than the epimer, he will yet to crystallize from the reaction mixture as soon as the solution becomes saturated with respect to the isomer, and this leads the process in favor of a less soluble isomer.

Polar organic solvents or diluents that can be used for the process of the invention are those in which the isomer product or racemic modification is less soluble than its epimer or the racemate. This can be, for example, monobasic lower alcohols containing up to six carbon atoms, such as isopro is, the AK ethyl acetate, or mixtures with alcohols, to obtain an environment that will allow isomer and epimer be separated on the basis of the difference in solubility. There may be a portion of the water within the Miscibility, but it is usually less than 20% by volume.

Preferably the solvent is a branched lower alcohol like isopropanol containing 2 to 15% by volume of water.

The source of cyanide ions may be cyanide alkaline or alkaline earth metal, or Quaternary ammonium cyanide. The most preferred sodium cyanide or potassium cyanide. It can be used in solid form, in this case, any residual material at the end of the process must be separated from the solid product by selective solubility, or by washing with water to dissolve the cyanide, or by extraction with an organic solvent to dissolve the product. In another case, the cyanide may be in the form of an aqueous solution, which, when used in excess can enforce two-phase system, where you use certain solvents, in this case, the method is facilitated by use of catalysts phase ammonium. Better if cyanide is present in the amount of 0.5 to 15.0 mol.% in relation to the epimer.

One of the suitable methods for the extraction of the product will be uploading the contents of the reactor in excess of diluted acid, such as sulfuric acid, or, better, a dilute water solution of alkali metal hypochlorite. This technique can be used with reaction mixtures with cyanide in solid or dissolved form, and this allows you to regenerate the product by filtration or by extraction of the solvent.

The method is carried out in a reactor in which the temperature can be controlled by external heating or cooling. The rate of decomposition of the crystalline product is enhanced by reducing the solubility of the product at lower temperatures and when shaking the contents of the reactor to thoroughly mix.

The timing will depend on the speed of formation of the product and it is not desirable that it was less than one hour and more than 60 hours. The exact conditions depend on the specific product. The method is carried out at a temperature in the range -10 to +20oC for 15 to 45 hours.

Although for some appropriate temperature for a certain period of time, it is often useful, especially for products with a lower melting temperature or a relatively high solubility, to add a portion of the product in solid crystalline form to the mixture to provide a crystalline surface, which can further crystallize the product. The number of added crystalline product is not critical, provided that it is enough to get a saturated solution with a portion remaining in the undissolved state at a certain operating temperature.

For a better understanding of the invention offers the following examples illustrate the use of the method to obtain the lambda-cyhalothrin. As already mentioned, the lambda cigalotrin is a racemic product, consisting of isomer S--cyano-3-phenoxybenzyl 1R,3R-3-/Z-2-chloro-3,3,3-cryptographp-1-EN-1-yl/2,2 - cyclopropanecarboxylate and its enantiomer. Lambda cigalotrin get out of cyhalothrin, which is produced as a mixture of four isomers in approximately equal amounts, with two isomers are lambda cigalotrin and epimere these two isomers, i.e. R--cyano-3-phenoxybenzyl 1R, 3R-3-/Z-2-chloro-3,3,3-Cryptocom-1-EN-1-yl/ -2,2-cyclopropanecarboxylate and his ananatis) and "Para isomer II".

Example 1. Cigalotrin (105 g), wet isopropanol containing 2,7 or 8.0% weight/weight of water (270 g), sodium cyanide (6.5 g) and crystalline lambda cigalotrin loaded into a 1-liter glass reactor, turbine equipped with a glass stirrer and a cooling jacket, maintained at a temperature of -5oC, which is maintained by circulation of chilled mixture of water and ethylene glycol, with stirring for 24 hours, after which the ratio of the Pair of the first isomer /Pair II isomer determined by gas chromatography. The stirring is continued for another 24 hours and make a second determination of the ratio I/II.

The results listed in the table in comparison with the results obtained in similar experiments, in which instead of the cyanide present Diisopropylamine.

The table shows that the use of cyanide allows you to complete the method after 24 hours, while the use of amine requires a much longer period to achieve the same end result.

1. The method of obtaining the lambda-cyhalothrin in the form of a racemic modification, containing S--cyano-3-phenoxybenzyl - 1R,3R - 3-(Z-2-chloro-3,3,3-Cryptocom-1-EN-1-yl)-2,2-dimethylcyclopropanecarboxylate and its enantiomer, including education, components lambda-cigalotrin and epimer of these two isomers in solution or in suspension in isopropanol, wherein the treatment is carried out in the wet isopropanol containing 2 to 15% vol. water, sodium cyanide, taken in an amount of 0.5 to 15.0 mol.% the number of cyhalothrin, at a temperature of -10o... +20oC.

2. The method according to p. 1, characterized in that epimer obtained industrially in a mixture with isomers.

3. The method according to p. 1, characterized in that the cyanide is used in solid form.

4. The method according to p. 1, characterized in that the cyanide is used in the form of an aqueous solution in the presence of a catalyst phase transfer.

 

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