Novel method for synthesizing quizalofop-p-ethyl

Abstract

The invention belongs to the field of chemistry and chemical engineering, and particularly relates to a novel method for synthesizing quizalofop-p-ethyl. The quizalofop-p-ethyl racemate reacts with a configuration conversion reagent, so that the quizalofop-p-ethyl racemate is efficiently converted into R-configuration quizalofop-p-ethyl. According to the method, the quizalofop-p-ethyl racemate is converted into quizalofop-p-ethyl with high optical purity under the action of the configuration conversion agent, the use of a high-optical-purity intermediate for synthesizing quizalofop-p-ethyl is avoided, so that the raw material cost can be greatly reduced, and meanwhile, for a quizalofop-p-ethyl product with insufficient optical purity, the yield of the quizalofop-p-ethyl is greatly improved. The optical purity can be improved by the method.

Description

Technical Field

[0001] This invention belongs to the field of chemical engineering, and specifically relates to a new method for synthesizing quizalofop-p-ethyl. Background Technology

[0002] Quizalofop-P-ethyl, chemically known as (R)-2-[4-(6-chloro-2-quinoxalinyl)oxy]phenoxy]propionate ethyl ester, is a highly effective, low-toxicity, and highly selective aryloxyphenoxypropionic acid post-emergence herbicide for dryland crops. It effectively disrupts fatty acid synthesis by inhibiting acetyl-CoA carboxylase in gramineous plants, thus causing weed death. Quizalofop-P-ethyl is highly safe for broadleaf crops (such as soybeans, cotton, peanuts, and rapeseed) and effectively controls annual and perennial gramineous weeds such as barnyard grass, foxtail grass, crabgrass, and goosegrass, enjoying wide application value and an important market position in agricultural production.

[0003] Currently, the R-configuration of quizalofop-P-ethyl requires the use of an R-configuration chiral intermediate for synthesis: However, there is a problem with high raw material costs.

[0004] Therefore, there is an urgent need in this field to develop a new method for the synthesis of quizalofop-P-ethyl, which should have the characteristics of a short route, low raw material cost, mild reaction conditions, and high overall yield, so as to meet the dual requirements of economic efficiency and environmental protection for industrial production. Summary of the Invention

[0005] To address the above problems, the purpose of this invention is to provide a new method for synthesizing quizalofop-P-ethyl.

[0006] To achieve the above objectives, the technical solution adopted by the present invention is as follows: A novel method for the synthesis of quizalofop-P-ethyl involves reacting the racemic quizalofop-P-ethyl with a configuration inversion reagent to efficiently convert the racemic quizalofop-P-ethyl into the R configuration. .

[0007] Furthermore, the racemic mixture of quizalofop-P-ethyl and the configuration inversion reagent are dissolved in an organic solvent and reacted at 20-80°C for 1-24 hours. After the reaction, the filter cake is washed until no quizalofop-P-ethyl product is detectable in the filtrate. The filtrate is collected, and the solvent is distilled off under reduced pressure to obtain the R-configuration of quizalofop-P-ethyl. The filter cake and solvent are reused.

[0008] Preferably, the reaction is carried out at 20°C for 8 hours.

[0009] The configuration inversion reagent is one or more of silica powder, silica, silicate, and diatomaceous earth. Preferably, the configuration inversion reagent is silica powder.

[0010] The amount of configuration conversion reagent used is 1-10 times the mass of the quizalofop-p-ethyl racemic mixture.

[0011] The organic solvent is one or more of ethyl acetate, diethyl ether, dichloroethane, dichloromethane, chloroform, n-hexane, petroleum ether, acetone, methanol, ethanol, toluene, xylene, and acetonitrile. Preferably, the organic solvent is ethyl acetate.

[0012] The solvent is one or more selected from ethyl acetate, diethyl ether, dichloroethane, dichloromethane, chloroform, n-hexane, petroleum ether, and acetone. Ethyl acetate is preferred.

[0013] After the reaction was complete, the filter cake was washed with solvent until no quizalofop-P-ethyl product was detected in the filtrate. The filtrate was collected and evaporated to dryness to obtain the R-configuration quizalofop-P-ethyl. The filter cake and solvent were reused.

[0014] The solvent is one or more selected from ethyl acetate, diethyl ether, dichloroethane, dichloromethane, chloroform, n-hexane, petroleum ether, and acetone. Ethyl acetate is preferred.

[0015] The beneficial effects of this invention are: This invention uses a quizalofop-P-ethyl racemic mixture to convert it into a high-optical-purity quizalofop-P-ethyl. By avoiding the use of high-optical-purity intermediates in the synthesis of quizalofop-P-ethyl, the raw material cost can be significantly reduced. At the same time, for quizalofop-P-ethyl products with insufficient optical purity, this method can improve the optical purity. Detailed Implementation

[0016] The reaction raw materials and solvents involved in the embodiments of this invention are all commercially available.

[0017] Example 1

[0018] 10g of racemic quizalofop-P-ethyl and 20g of silica gel powder were added to 40mL of ethyl acetate and stirred at 20℃ for 8 hours. After the reaction was completed, the mixture was filtered and the filter cake was washed twice with 10mL of ethyl acetate. The filtrate was collected and the solvent was evaporated under reduced pressure to obtain 9.8g of purified quizalofop-P-ethyl (yield 98%, purity 99%, ee 99%). The filter cake and solvent were reused.

[0019] Example 2

[0020] 10g of racemic quizalofop-P-ethyl and 20g of silica gel powder were added to 40mL of dichloroethane and stirred at 20°C for 8 hours. After the reaction was completed, the mixture was filtered and the filter cake was washed twice with 10mL of dichloroethane. The filtrate was collected and the solvent was evaporated under reduced pressure to obtain 9.7g of purified quizalofop-P-ethyl (yield 97%, purity 99%, ee 98%). The filter cake and solvent were reused.

[0021] Example 3

[0022] 10g of racemic quizalofop-P-ethyl and 20g of silica gel powder were added to 40mL of toluene and stirred at 20℃ for 8 hours. After the reaction was completed, the mixture was filtered and the filter cake was washed twice with 10mL of toluene. The filtrate was collected and the solvent was evaporated under reduced pressure to obtain 9.7g of purified quizalofop-P-ethyl (yield 98%, purity 99%, ee 98%). The filter cake and solvent were reused.

[0023] Comparative Example 1 10g of quizalofop-P-ethyl racemic mixture and 20g of neutral alumina were added to 40mL of toluene and stirred at 20℃ for 8 hours. After the reaction was completed, the mixture was filtered and the filter cake was washed twice with 10mL of toluene. The filtrate was collected and the solvent was evaporated under reduced pressure to obtain 9.7g of quizalofop-P-ethyl racemic mixture (ee 5%).

[0024] As can be seen from the comparison between the examples and Comparative Example 1, Comparative Example 1 used neutral alumina as the configuration conversion agent, but the final ee value was only 5%, and almost no R configuration of quizalofop-P-ethyl was obtained. Therefore, the selection of configuration conversion agent is extremely important. The present invention uses one or more of silica powder, silica, silicate, and diatomaceous earth. Silica powder is preferred, which can realize the conversion of quizalofop-P-ethyl racemic into high optical purity quizalofop-P-ethyl, with an ee value of up to 99%.

[0025] In summary, this invention uses a configuration conversion agent to convert the racemic mixture of quizalofop-P-ethyl into high-optical-purity quizalofop-P-ethyl, which can significantly reduce raw material costs. The configuration conversion agent is inexpensive, the operation is simple, and the overall economic benefits are significant. At the same time, for quizalofop-P-ethyl products with insufficient optical purity, this method can improve the optical purity.

Claims

1. A novel method for synthesizing quizalofop-P-ethyl, characterized in that: The racemic form of quizalofop-P-ethyl reacts with a configuration inversion reagent to efficiently convert the racemic form of quizalofop-P-ethyl into the R configuration.

2. The method according to claim 1, characterized in that: The racemic mixture of quizalofop-P-ethyl and the configuration inversion reagent are dissolved in an organic solvent and reacted at 20-80℃ for 1-24 hours. After the reaction is completed, the filter cake is washed, the filtrate is collected, and the solvent is distilled off under reduced pressure to obtain the R-configured quizalofop-P-ethyl. The filter cake and solvent are reused.

3. The method according to claim 2, characterized in that: React at 20℃ for 8 hours.

4. The method according to claim 1, characterized in that: The configuration inversion reagent is one or more of silica powder, silicon dioxide, silicate, and diatomaceous earth.

5. The method according to claim 4, characterized in that: The configuration conversion reagent is silica powder.

6. The method according to claim 2, characterized in that: The amount of configuration conversion reagent used is 1-10 times the mass of the quizalofop-p-ethyl racemic mixture.

7. The method according to claim 2, characterized in that: The organic solvent is one or more of ethyl acetate, diethyl ether, dichloroethane, dichloromethane, chloroform, n-hexane, petroleum ether, acetone, methanol, ethanol, toluene, xylene, and acetonitrile.

8. The method according to claim 7, characterized in that: The organic solvent is ethyl acetate.

9. The method according to claim 2, characterized in that: After the reaction is complete, the filter cake is washed with a solvent, which can be one or more of ethyl acetate, diethyl ether, dichloroethane, dichloromethane, chloroform, n-hexane, petroleum ether, and acetone.

10. The method according to claim 9, characterized in that: The solvent is ethyl acetate.