A method for preparing ethyl chrysanthemate

Abstract

The present application belongs to the technical field of organic synthesis, and particularly relates to a preparation method of ethyl chrysanthemate. Glycine ethyl ester hydrochloride is reacted with sodium nitrite in a dispersion system containing organic mixed solvents to obtain a diazo ethyl acetate dispersion liquid, which is then mixed with an octacarbene and reacted under the catalysis of an organic amine catalyst to generate ethyl chrysanthemate. After the reaction is completed, the target product ethyl chrysanthemate is purified, and the organic mixed solvents collected in the purification process are recycled to step (1). The present application adopts mixed solvents such as methyl tert-amyl ether methyl ether, petroleum ether and n-hexane, and the diazotization yield reaches 96%. At the same time, an organic amine catalyst is adopted, and the cyclization yield reaches 88%. The new preparation method of ethyl chrysanthemate of the present application has significant advantages in yield and quality, and contributes a new solution to the development of the health insecticide industry and the anti-new coronavirus pharmaceutical industry.

Description

Technical Field

[0001] This invention belongs to the field of organic synthesis technology, and specifically relates to a method for preparing ethyl chrysanthemate. Background Technology

[0002] Ethyl chrysanthemate is a key intermediate in the production of first-generation chrysanthemic acid-based sanitary insecticides, holding a significant position in the sanitary insecticide market and international competition. However, currently only a few countries worldwide are capable of producing ethyl chrysanthemate, and its production capacity and cost directly impact the competitiveness of domestic sanitary insecticides and foreign competing products. Furthermore, ethyl chrysanthemate also plays a crucial role in the production of calonic anhydride.

[0003] Ethyl chrysanthemate has advantages such as relatively low toxicity, less wastewater production, and a small molecular weight. However, its high production cost and limited output have led to insufficient market demand, limited annual production, and even supply shortages, causing instability in the market. Therefore, both the pesticide industry and the pharmaceutical industry dealing with novel coronavirus urgently need to increase the production of ethyl chrysanthemate and reduce its production costs. Summary of the Invention

[0004] To solve the above-mentioned technical problems, the present invention provides a method for preparing ethyl chrysanthemate:

[0005] (1) Diazotization

[0006] Glycine ethyl ester hydrochloride reacts with sodium nitrite in a dispersion system containing an organic mixed solvent to obtain a diazonium ethyl acetate dispersion, wherein the organic mixed solvent is tert-amyl methyl ether and petroleum ether (relative density 0.64–0.66 g / cm³). 3 (water = 1) and a combination of at least two of the following: n-hexane;

[0007] (2) Cycloning

[0008] The ethyl diazonium ester dispersion obtained in step (1) is mixed with octacarbene and reacted to generate ethyl chrysanthemate under the catalysis of an organic amine catalyst. The organic amine catalyst is one or a combination of several of triethylenediamine, triethylamine, N,N-dimethylcyclohexylamine, pyridine, and N-ethylmorpholine. After the reaction is completed, the target product ethyl chrysanthemate is purified and the organic mixed solvent collected during the purification process is recycled to step (1).

[0009] As a preferred method: In step (1), glycine ethyl ester hydrochloride is first dispersed and dissolved in water, and then an organic mixed solvent is added to it. While stirring continuously, sodium nitrite aqueous solution and acid solution are added dropwise. After the addition is completed, the reaction is stopped after stirring for a period of time. The mixture is allowed to stand and separate into layers. The organic phase after separation is collected and washed to obtain ethyl diazonium chloride dispersion.

[0010] Further: In step (1), glycine ethyl ester hydrochloride is dispersed and dissolved in water, and then an organic mixed solvent is added to it. Under continuous stirring, the temperature of the stirring system is first adjusted to 10°C by an ice-water bath, and sodium nitrite aqueous solution and acid solution are added dropwise to it under the condition of keeping it warm.

[0011] Further: In step (1), the acid solution is a dilute sulfuric acid aqueous solution with a solute mass fraction of 10%.

[0012] As a preferred option: In step (2), after mixing octadecene, polymerization inhibitor and organic amine catalyst, the mixture is heated to 100℃~105℃ under continuous stirring, and then the ethyl diazonium acetate dispersion obtained in step (1) is added dropwise under the heat preservation condition. After the addition is completed, the reaction continues for a period of time.

[0013] Further: In step (2), during the heating and heat preservation stages, the components that vaporize after being heated in the reaction system are simultaneously condensed and refluxed.

[0014] As a preferred option: In step (2), after the reaction is completed, the resulting reaction system is added to cold water and allowed to stand and separate. The organic amine catalyst enters the aqueous phase to achieve separation. The organic phase after separation is then collected. After the organic phase is evaporated, crude ethyl chrysanthemate is left. During the evaporation process, the heated and vaporized components are condensed and collected to achieve the recovery of the organic mixed solvent (on this basis, further increasing the evaporation temperature can condense and collect most of the excess reactant octadecene).

[0015] As a preferred option: In step (2), after the reaction is completed, the resulting reaction system is evaporated to leave crude ethyl chrysanthemate. During the evaporation process, the heated and vaporized components are condensed and collected to recover the organic mixed solvent containing organic amine catalysts (on this basis, further increasing the evaporation temperature can condense and collect most of the excess reactant octacarbonene). In this way, when the organic mixed solvent recovered here is reused in the process of this scheme, the use of organic amine catalysts can be reduced or eliminated in step (2).

[0016] Further: In step (2), the crude ethyl chrysanthemate product is subjected to negative pressure distillation, and the main fraction is collected as the target product ethyl chrysanthemate (the octadecene remaining in the crude product is separated and removed with the front fraction).

[0017] The beneficial effects of this invention are as follows: In the diazotization reaction of step (1), this scheme selects a mixed solvent composed of tert-amyl methyl ether, petroleum ether, and n-hexane as the organic phase for the diazotization reaction, so that after the diazotization reaction in step (1), the organic phase containing the product ethyl diazonium chloride can be fully separated from the aqueous phase, which can increase the reaction yield of step (1) by 6-7%; at the same time, it effectively avoids the safety hazards caused by the ethyl diazonium chloride organic phase carrying water into the heated cyclization reaction in step (2), and because the ethyl diazonium chloride organic phase enters the aqueous phase, the organic phase of the product can be fully separated from the aqueous phase. The amount of water carried in step (2) is very small, which can increase the yield of the cyclization reaction in step (2) by about 3%. At the same time, the limit on the (weight) content of octadecene carried by the organic mixed solvent collected after the reaction in step (2) and prepared for reuse in step (1) is also relaxed, allowing up to 5% or even higher, which is more feasible for industrial production. If the aqueous phase after stratification in step (1) is evaporated, desalted and recycled, and reused in step (1), the COD emissions of the entire process route can be reduced by more than 60%.

[0018] Meanwhile, this scheme uses organic amines as catalysts in the cyclization reaction, which can be dispersed freely in the organic phase of octadecene to form a homogeneous reaction with high stability, which is beneficial to the cyclization yield.

[0019] Therefore, the novel preparation method of ethyl chrysanthemate of the present invention is easy to operate and has significant advantages in terms of yield and quality, providing new impetus for the sustainable development of the sanitary insecticide industry and the pharmaceutical industry for combating the novel coronavirus. Attached Figure Description

[0020] Figure 1 The chromatogram is the detection chromatogram of the product prepared in step (2) of Example 1. Detailed Implementation

[0021] A method for preparing ethyl chrysanthemate:

[0022] (1) Diazotization

[0023] First, glycine ethyl ester hydrochloride was dispersed and dissolved in water. Then, an organic mixed solvent was added to it. The organic mixed solvent was a combination of at least two of tert-amyl methyl ether, petroleum ether, and n-hexane. Under continuous stirring, the temperature of the stirred system was first adjusted to 10°C by an ice-water bath. Under the condition of keeping the temperature warm, sodium nitrite aqueous solution and dilute sulfuric acid aqueous solution with a solute mass fraction of 10% were added dropwise. After the addition was completed, the reaction was continued for a period of time and then stopped. The mixture was allowed to stand and separate into layers. The organic phase after separation was collected and washed to obtain ethyl diazonium chloride dispersion.

[0024] (2) Cycloning

[0025] Octadene, a polymerization inhibitor (hydroquinone, the same below), and an organic amine catalyst are mixed. The organic amine catalyst is one or a combination of several of triethylenediamine, triethylamine, N,N-dimethylcyclohexylamine, pyridine, and N-ethylmorpholine. The mixture is heated to 100℃~105℃ under continuous stirring and reflux. Then, the ethyl diazonium ester dispersion obtained in step (1) is added dropwise while maintaining the temperature. After the addition is complete, the reaction continues for a period of time.

[0026] After the reaction is completed, the resulting reaction system is added to cold water and allowed to stand for separation. The organic amine catalyst enters the aqueous phase to achieve separation. The organic phase after separation is then evaporated to leave crude ethyl chrysanthemate. During the evaporation process, the heated and vaporized components are condensed and collected to recover the organic mixed solvent. The recovered organic mixed solvent is reused in step (1). Further increasing the evaporation temperature can condense and collect most of the excess reactant octadecene. The crude ethyl chrysanthemate left after evaporation is then subjected to negative pressure distillation, and the main fraction is collected as the target product ethyl chrysanthemate (the octadecene remaining in the crude product is separated and removed with the previous fraction).

[0027] Example 1

[0028] (1) Diazotization

[0029] Add 275 g of glycine ethyl ester hydrochloride, 250 mL of deionized water, 450 mL of tert-amyl methyl ether, and 100 mL of n-hexane to the reaction flask in sequence. While continuously stirring, first adjust the temperature of the stirred system to 10°C using an ice-water bath. Then, while maintaining the temperature and continuously stirring, add an aqueous solution of sodium nitrite (156 g of sodium nitrite dissolved in 245 mL of deionized water) dropwise. After the addition is complete, continue to add a 10% (w / w) dilute sulfuric acid aqueous solution dropwise while maintaining the temperature at 10°C and continuously stirring to adjust the pH of the mixture to 4 and stabilize it.

[0030] After adding the dilute sulfuric acid aqueous solution, the mixture was kept at 10°C and stirred for 45 minutes. After stirring, the mixture was allowed to stand at 10°C to separate into layers. The separated organic phase was added to 100 mL of deionized water and stirred and washed at 10°C for 10 minutes. The mixture was then allowed to stand at 10°C to separate into layers again. The separated organic phase was used as the diazonated ethyl acetate dispersion. The composition of the diazonated ethyl acetate dispersion was analyzed by gas chromatography, and the yield of diazonated ethyl acetate was 96.5% (moles of diazonated ethyl acetate in the dispersion ÷ moles of glycine ethyl ester hydrochloride in the raw material × 100%, the same below). The water content of the diazonated ethyl acetate dispersion was measured to be 0.002% by a Karl Fischer moisture analyzer. The mixture was stored at 10°C for later use.

[0031] (2) Cycloning

[0032] 650 g of octadecene, 2.4 g of triethylenediamine catalyst, and 0.01 g of polymerization inhibitor were added to another reaction flask. The mixture was electrically heated to 103 °C and held at this temperature under continuous stirring and reflux. Then, the ethyl diazonium ester dispersion obtained in step (1) was added dropwise. After the addition was complete, the mixture was stirred and kept at this temperature for another 30 minutes.

[0033] After the reaction was completed, the resulting reaction system was added to sufficient cold water and allowed to stand for separation. The organic amine catalyst entered the aqueous phase for separation. The separated organic phase was then evaporated at -0.08 MPa vacuum (assuming one standard atmosphere is 0 Pa, the same below) and 80°C. During the evaporation process, the heated and vaporized components were condensed and collected to recover the organic mixed solvent from the diazonium ethyl acetate dispersion. After sufficient condensation and collection, the crude ethyl chrysanthemate product left after evaporation was separated by distillation at -0.1 MPa vacuum and 140°C, and the main fraction was collected as the target product ethyl chrysanthemate (purity greater than 97%, yield 88.2%, moles of target product ethyl chrysanthemate ÷ moles of diazonium ethyl acetate obtained in step (1) × 100%, the same below). The chromatogram of the product is attached. Figure 1 As shown.

[0034] Example 2

[0035] (1) Diazotization

[0036] Add 275 g of glycine ethyl ester hydrochloride, 250 mL of deionized water, and petroleum ether (relative density 0.64–0.66 g / cm³) sequentially to the reaction flask. 3 Mix 200 mL of water and 400 mL of n-hexane. While continuously stirring, first adjust the temperature of the mixture to 10°C using an ice-water bath. Then, while maintaining the temperature and continuing to stir, add dropwise a sodium nitrite aqueous solution (165 g sodium nitrite dissolved in 260 mL deionized water). After the addition is complete, continue to add a 10% (w / w) dilute sulfuric acid aqueous solution while maintaining the temperature at 10°C and continuing to stir, to adjust the pH of the mixture to 3.5 and stabilize it.

[0037] After adding the dilute sulfuric acid aqueous solution, the mixture was kept at 10°C and stirred for 20 minutes. After stirring, the mixture was allowed to stand at 10°C to separate into layers. The separated organic phase was added to 150 mL of deionized water and washed at 10°C for 20 minutes. The mixture was then allowed to stand at 10°C to separate into layers again. The separated organic phase was used as the diazonated ethyl acetate dispersion. The composition of the diazonated ethyl acetate dispersion was analyzed by gas chromatography, and the yield of diazonated ethyl acetate was 97%. The water content of the diazonated ethyl acetate dispersion was measured to be 0.003% by a Karl Fischer moisture analyzer. The mixture was stored at 10°C for later use.

[0038] (2) Cycloning

[0039] 680 g of octadecene, 2.8 g of N-ethylmorpholine catalyst, and 0.02 g of polymerization inhibitor were added to another reaction flask. The mixture was electrically heated to 103 °C and held at this temperature under continuous stirring and reflux. Then, the ethyl diazonium ester dispersion obtained in step (1) was added dropwise. After the addition was complete, the mixture was stirred and kept at this temperature for another 20 minutes.

[0040] After the reaction was completed, the resulting reaction system was added to sufficient cold water and allowed to stand for separation. The organic amine catalyst entered the aqueous phase for separation. The separated organic phase was then evaporated at -0.08 MPa vacuum and 80 °C. During the evaporation process, the heated and vaporized components were condensed and collected to recover the organic mixed solvent from the ethyl diazonium ester dispersion. After sufficient condensation and collection, the crude ethyl chrysanthemate product remaining after evaporation was separated by distillation at -0.1 MPa vacuum and 140 °C, and the main fraction was collected as the target product ethyl chrysanthemate (purity greater than 98.0%, yield 88.4%).

[0041] Example 3

[0042] (1) Diazotization

[0043] Add 27.5 g of glycine ethyl ester hydrochloride, 25 mL of deionized water, 30 mL of tert-amyl methyl ether, and petroleum ether (relative density 0.64–0.66 g / cm³) sequentially to the reaction flask. 3 (Water = 1) 30 mL, while continuously stirring, first adjust the temperature of the stirred system to 10℃ using an ice-water bath, and then add sodium nitrite aqueous solution (16 g sodium nitrite dissolved in 25 mL deionized water) dropwise while maintaining the temperature and continuous stirring. After the addition is complete, continue to add a 10% dilute sulfuric acid aqueous solution dropwise while maintaining the temperature at 10℃ and continuous stirring to adjust the pH of the mixture to 4 and stabilize it.

[0044] After adding the dilute sulfuric acid aqueous solution, the mixture was kept at 10°C and stirred for 30 minutes. After stirring, the mixture was allowed to stand at 10°C to separate into layers. The separated organic phase was added to 15 mL of deionized water and stirred and washed at 10°C for 35 minutes. The mixture was then allowed to stand at 10°C to separate into layers again. The separated organic phase was used as the diazonated ethyl acetate dispersion. The composition of the diazonated ethyl acetate dispersion was analyzed by gas chromatography, and the yield of diazonated ethyl acetate was 96.4%. The water content of the diazonated ethyl acetate dispersion was measured to be 0.002% by a Karl Fischer moisture analyzer. The mixture was stored at 10°C for later use.

[0045] (2) Cycloning

[0046] 65 g of octadecene, 0.2 g of triethylamine catalyst, and 0.002 g of polymerization inhibitor were added to another reaction flask. The mixture was electrically heated to 103 °C and held at this temperature under continuous stirring and reflux. Then, the ethyl diazonium ester dispersion obtained in step (1) was added dropwise. After the addition was complete, the mixture was stirred and held at this temperature for another 20 minutes.

[0047] After the reaction was completed, the resulting reaction system was evaporated at -0.08 MPa vacuum and 80 °C. During the evaporation process, the heated and vaporized components were condensed and collected to recover the organic mixed solvent containing the organic amine catalyst (from the diazonium ethyl acetate dispersion). After sufficient condensation and collection, the crude ethyl chrysanthemate product remaining after evaporation was separated by distillation at -0.1 MPa vacuum and 140 °C, and the main fraction was collected as the target product ethyl chrysanthemate (purity greater than 97.3%, yield 87.8%).

[0048] Comparative Example 1

[0049] Use 1,2-dichloroethane instead of the organic mixed solvent of "450 mL of tert-amyl methyl ether and 100 mL of n-hexane" in Example 1, and perform the remaining operations as in Example 1:

[0050] (1) Diazotization

[0051] Add 275 g of glycine ethyl ester hydrochloride, 250 mL of deionized water, and 550 mL of 1,2-dichloroethane sequentially to the reaction flask. While continuously stirring, first adjust the temperature of the stirred system to 10°C using an ice-water bath. Then, while maintaining the temperature and continuously stirring, add an aqueous solution of sodium nitrite (156 g of sodium nitrite dissolved in 245 mL of deionized water) dropwise. After the addition is complete, continue to add a 10% (w / w) dilute sulfuric acid aqueous solution dropwise while maintaining the temperature at 10°C and continuously stirring to adjust and stabilize the pH of the mixture to 4.

[0052] After adding the dilute sulfuric acid aqueous solution, the mixture was kept at 10°C and stirred for 45 minutes. After stirring, the mixture was allowed to stand at 10°C to separate into layers. The separated organic phase was added to 100 mL of deionized water and stirred and washed at 10°C for 10 minutes. The mixture was then allowed to stand at 10°C to separate into layers again. The separated organic phase was used as the diazonated ethyl acetate dispersion. The composition of the diazonated ethyl acetate dispersion was analyzed by gas chromatography, and the yield of diazonated ethyl acetate was found to be 88.2%. The water content of the diazonated ethyl acetate dispersion was determined to be 0.007% by a Karl Fischer moisture analyzer.

[0053] Due to the safety concerns posed by the high moisture content, this ethyl diazonium ester dispersion is not suitable for direct use in the dropwise reaction in step (2).

[0054] Comparative Example 2

[0055] The organic mixed solvent of "450 mL of tert-amyl methyl ether and 100 mL of n-hexane" in Example 1 was completely replaced with tert-amyl methyl ether, and all other operations were the same as in Example 1:

[0056] (1) Diazotization

[0057] Add 275 g of glycine ethyl ester hydrochloride, 250 mL of deionized water, and 550 mL of tert-amyl methyl ether sequentially to the reaction flask. While continuously stirring, first adjust the temperature of the stirred system to 10°C using an ice-water bath. Then, while maintaining the temperature and continuously stirring, add dropwise a sodium nitrite aqueous solution (156 g of sodium nitrite dissolved in 245 mL of deionized water). After the addition is complete, continue to add a 10% (w / w) dilute sulfuric acid aqueous solution while maintaining the temperature at 10°C and continuously stirring to adjust and stabilize the pH of the mixture to 4.

[0058] After adding the dilute sulfuric acid aqueous solution, the mixture was kept at 10°C and stirred for 45 minutes. After stirring, the mixture was allowed to stand at 10°C to separate into layers. The separated organic phase was added to 100 mL of deionized water and washed at 10°C for 10 minutes. The mixture was then allowed to stand at 10°C to separate into layers again. The separated organic phase was used as the diazonated ethyl acetate dispersion. The composition of the diazonated ethyl acetate dispersion was analyzed by gas chromatography, and the yield of diazonated ethyl acetate was 90.8%. The water content of the diazonated ethyl acetate dispersion was measured to be 0.004% by a Karl Fischer moisture analyzer. The mixture was stored at 10°C for later use.

[0059] (2) Cycloning

[0060] 650 g of octadecene, 2.4 g of triethylenediamine catalyst, and 0.01 g of polymerization inhibitor were added to another reaction flask. The mixture was electrically heated to 103 °C and held at this temperature under continuous stirring and reflux. Then, the ethyl diazonium ester dispersion obtained in step (1) was added dropwise. After the addition was complete, the mixture was stirred and kept at this temperature for another 30 minutes.

[0061] After the reaction was completed, the resulting reaction system was added to sufficient cold water and allowed to stand for separation. The organic amine catalyst entered the aqueous phase for separation. The separated organic phase was then evaporated at -0.08 MPa vacuum and 80 °C. During the evaporation process, the heated and vaporized components were condensed and collected to recover the organic mixed solvent from the ethyl diazonium ester dispersion. After sufficient condensation and collection, the crude ethyl chrysanthemate product remaining after evaporation was separated by distillation at -0.1 MPa vacuum and 140 °C, and the main fraction was collected as the target product ethyl chrysanthemate (purity 92.7%, yield 84.6%).

[0062] It can be seen that when using a single organic solvent, although the water content of the product dispersion obtained in step (1) meets the standard (less than 0.005), it is still higher than that of the scheme using a mixed organic solvent, resulting in a decline in the yield in both steps (1) and (2).

[0063] Comparative Example 3

[0064] In step (2), no catalyst, triethylenediamine, was added; all other operations were the same as in Example 1.

[0065] (1) Diazotization

[0066] Same as step (1) in Example 1;

[0067] (2) Cycloning

[0068] 650 g of octadecene and 0.01 g of polymerization inhibitor were added to another reaction flask. The mixture was electrically heated to 103 °C and held at this temperature under continuous stirring and reflux. Then, the ethyl diazonium ester dispersion obtained in step (1) was added dropwise. After the addition was complete, the mixture was stirred and held at this temperature for another 30 minutes.

[0069] After the reaction was completed, the resulting reaction system was added to sufficient cold water and allowed to stand for separation. The separated organic phase was then evaporated at -0.08 MPa vacuum and 80 °C. During the evaporation process, the heated and vaporized components were condensed and collected to recover the organic mixed solvent from the ethyl diazonium ester dispersion. After sufficient condensation and collection, the crude ethyl chrysanthemate product remaining after evaporation was separated by distillation at -0.1 MPa vacuum and 140 °C, and the main fraction was collected as the target product ethyl chrysanthemate (purity 86.2%, yield 23.5%).

Claims

1. A method for preparing ethyl chrysanthemate, characterized in that: The method is as follows: (1) Diazotization Glycine ethyl ester hydrochloride and sodium nitrite are reacted in a dispersion system containing an organic mixed solvent to obtain an ethyl diazonium chloride dispersion, wherein the organic mixed solvent is a combination of at least two of tert-amyl methyl ether, petroleum ether, and n-hexane; (2) Cycloning The ethyl diazonium ester dispersion obtained in step (1) is mixed with octadecene and reacted under the catalysis of an organic amine catalyst to generate ethyl chrysanthemate. After the reaction is completed, the target product ethyl chrysanthemate is purified, and the organic mixed solvent collected during the purification process is recycled back to step (1). The organic amine catalyst is any one of triethylenediamine, N-ethylmorpholine, and triethylamine.

2. The method for preparing ethyl chrysanthemate according to claim 1, characterized in that: In step (1), glycine ethyl ester hydrochloride is first dispersed and dissolved in water, and then the organic mixed solvent is added to it. While stirring continuously, sodium nitrite aqueous solution and acid solution are added dropwise. After the addition is completed, the reaction is continued for a period of time and then stopped. The mixture is allowed to stand and separate into layers. The organic phase after separation is collected and washed to obtain the diazonium ethyl acetate dispersion.

3. The method for preparing ethyl chrysanthemate according to claim 2, characterized in that: In step (1), glycine ethyl ester hydrochloride is dispersed and dissolved in water, and then the organic mixed solvent is added to it. Under continuous stirring, the temperature of the stirring system is first adjusted to 10°C by an ice-water bath, and the sodium nitrite aqueous solution and the acid solution are added dropwise while keeping the system warm.

4. The method for preparing ethyl chrysanthemate as described in claim 2, characterized in that: In step (1), the acid solution is a dilute sulfuric acid aqueous solution with a solute mass fraction of 10%.

5. The method for preparing ethyl chrysanthemate according to claim 1, characterized in that: In step (2), after mixing the octadecene, the polymerization inhibitor, and the organic amine catalyst, the mixture is heated to 100℃~105℃ under continuous stirring. Then, the ethyl diazonium acetate dispersion obtained in step (1) is added dropwise while maintaining the temperature. After the addition is complete, the reaction continues for a period of time.

6. The method for preparing ethyl chrysanthemate according to claim 5, characterized in that: In step (2), during the heating and heat preservation stages, the components that vaporize after being heated in the reaction system are simultaneously condensed and refluxed.

7. The method for preparing ethyl chrysanthemate according to claim 1, characterized in that: In step (2), after the reaction is completed, the resulting reaction system is added to cold water, allowed to stand and separate into layers, the organic phase after separation is collected, and then the organic phase is evaporated to leave crude ethyl chrysanthemate. During the evaporation process, the heated and vaporized components are condensed and collected to recover the organic mixed solvent.

8. The method for preparing ethyl chrysanthemate according to claim 1, characterized in that: In step (2), after the reaction is completed, the resulting reaction system is evaporated to leave crude ethyl chrysanthemate. During the evaporation process, the heated and vaporized components are condensed and collected to recover the organic mixed solvent containing the organic amine catalyst.

9. The method for preparing ethyl chrysanthemate as described in claim 7 or 8, characterized in that: In step (2), the crude ethyl chrysanthemate product is subjected to negative pressure distillation, and the main fraction is collected as the target product ethyl chrysanthemate.

Images