Synthesis method of 3, 3-dimethyl-4, 6, 6-trichloro-7, 7, 7-trifluoroheptanoate

Abstract

The invention discloses a synthesis method of 3, 3-dimethyl-4, 6, 6-trichloro-7, 7, 7-trifluoroheptanoate, and relates to the technical field of organic synthesis. The 3, 3-dimethyl-4, 6, 6-trichloro-7, 7, 7-trifluoroheptanoate is obtained by taking methyl 3, 3-dimethyl-4, 6, 6-trichloro-7, 7, 7-trifluoroheptanoate and trifluorotrichloroethane as raw materials and carrying out addition reaction under the action of a catalyst. The preparation method comprises the following steps: (1) preparing a catalyst; (2) premixing; (3) initiating reaction; (4) reacting; (5) recycling; (6) layered washing; and (7) dehydrating. The method has the advantages that the reaction is performed in stages, and the catalyst with stable property and flowability is firstly prepared; adding relatively excessive catalyst to initiate reaction at low temperature; and after the reaction is initiated, adding the residual catalyst and the reaction raw materials in a double-dropwise manner. Therefore, the problems of low synthesis efficiency of the catalyst after addition by a one-pot method, high deactivation rate of the catalyst due to too fast temperature rise after initiation of the addition reaction, too long reaction time, low reaction yield and the like are avoided.

Description

Technical Field

[0003] The invention belongs to the technical field of synthetic chemistry, and particularly relates to a method for synthesizing 3,3-dimethyl-4,6,6-trichloro-7,7,7-trifluoroheptanoate. Background Art

[0004] Trifluorochlorpyrifos acid, also known as Kungfu acid, has a chemical name of 3-(2-chloro-3,3,3-trifluoropropene-1-yl) 2,2-dimethylcyclopropanecarboxylic acid. It is a common intermediate of multiple pyrethroid varieties. It was first successfully developed by Zeneca and put into industrial production for the production of pesticide products such as Kungfu pyrethrin, tefluthrin and Uranus. The production process in the prior art is mainly an industrial route using pentylene ester as the starting material. That is, pentylene ester (methyl ester or ethyl ester) first reacts with trifluorotrichloroethane (Fll3A) to generate 3,3-dimethyl-4,6,6-trichloro-7,7,7-trifluoroheptyl ester intermediate, and then undergoes cyclization, saponification, acidification, and recrystallization to obtain Kungfu acid. For example, Chinese patent CN106518645A discloses a method for preparing 3,3-dimethyl-4,6,6-trichloro-7,7,7-trifluoroheptanoate, wherein 20% to 30% of the total amount of methyl benzoate is placed in a reaction vessel with trichlorotrifluoroethane, monoethanolamine, tert-butyl alcohol and cuprous chloride, and the remaining methyl benzoate is dripped into the reaction system after a period of reaction. The one-time addition of trichlorotrifluoroethane (normal pressure boiling point 47.5°C) in this scheme makes it difficult to increase the system temperature and prolong the reaction time; and the one-time addition of cuprous chloride leads to a high catalyst deactivation rate, which increases the amount of cuprous chloride used. Chinese patent CN115636744A reported a method for preparing 3,3-dimethyl-4,6,6-trichloro-7,7,7-trifluoroheptanoate. Although the reaction time was shortened to 8 hours, the molar ratio of methyl benzoate to cuprous chloride was 1:0.1-0.4, and the optimal ratio was 1:0.25. The use of a large amount of cuprous chloride not only increased the production cost, but also the abandoned catalyst was prone to environmental pollution. Chinese patent CN108084019A reported a method for preparing 3,3-dimethyl-4,6,6-trichloro-7,7,7-trifluoroheptanoate. Methyl benzoate, trichlorotrifluoroethane, tert-butyl alcohol, monoethanolamine and cuprous chloride were added to the reactor in one pot. After the addition reaction was initiated, the temperature was easily suddenly increased, resulting in the deactivation of the catalyst, and there were great safety hazards in workshop production.

[0005] In summary, the existing synthesis schemes cannot avoid the problems of easy catalyst deactivation, long reaction time, sudden temperature rise after the reaction is initiated, and safety hazards in workshop production. It is necessary to improve the synthesis method of 3,3-dimethyl-4,6,6-trichloro-7,7,7-trifluoroheptanoate to avoid catalyst deactivation, thereby shortening the reaction time and improving operational safety. Summary of the invention

[0006] The technical problem to be solved by the present invention is how to avoid catalyst deactivation and thus reduce the amount of catalyst used, shorten the synthesis time of 3,3-dimethyl-4,6,6-trichloro-7,7,7-trifluoroheptanoate and improve the safety of the reaction. In view of the above technical problems to be solved, a method for synthesizing 3,3-dimethyl-4,6,6-trichloro-7,7,7-trifluoroheptanoate is now proposed. The synthetic reaction formula is as follows:

[0007]

[0008] To achieve the above object, the present invention provides the following technical solution: a method for synthesizing 3,3-dimethyl-4,6,6-trichloro-7,7,7-trifluoroheptanoate, which is prepared by the following steps:

[0009] (1) Catalyst preparation: cuprous chloride is mixed with monoethanolamine and ethylene glycol to obtain a catalyst solution. The molar ratio of methyl benzoate to cuprous chloride is 1:0.03-0.05, the molar ratio of cuprous chloride to monoethanolamine is 1:4-5, and the weight ratio of cuprous chloride to ethylene glycol is 1:1-10;

[0010] (2) premixing: methyl benzoate, trifluorotrichloroethane and tert-butyl alcohol are fully mixed to obtain a premix solution 1 for standby use; methyl benzoate and trifluorotrichloroethane are fully mixed to obtain a premix solution 2 for standby use;

[0011] (3) initiating the reaction, adding part of the catalyst prepared in step (1) to the premixed solution 1 in step (2), wherein the amount of the catalyst added accounts for 30% to 50% of the total amount, heating the mixture to 85 to 90° C. under stirring and reacting for 1 hour;

[0012] (4) reacting, adding the premix 2 in step (2) and the remaining catalyst in step (3) to the reaction solution in step (3) by double dropwise addition, heating to 100-105° C. and reacting for 4-6 hours;

[0013] In the step (1) of preparing the catalyst, cuprous chloride powder is added in batches into a mixed solution of monoethanolamine and ethylene glycol under the protection of an inert gas, stirring is maintained during the addition process, and the temperature is controlled between 30 and 80° C. After stirring for 30 to 60 minutes, the catalyst is obtained for use.

[0014] The reaction further comprises post-processing step (5) recovery, step (6) layered washing, and step (7) dehydration.

[0015] (5) Recovery: recovering tert-butyl alcohol, trifluorotrichloroethane and methyl benzoate in the reactants by distillation.

[0016] (6) Layered washing: the remaining product in step (5) is allowed to stand for stratification, and the upper organic layer is washed with water to obtain a crude product.

[0017] (7) Dehydration: the organic layer after washing in step (5) is dehydrated to obtain the finished product of 3,3-dimethyl-4,6,6-trichloro-7,7,7-trifluoroheptanoate.

[0018] Furthermore, in step (2), the molar ratio of the total amount of methyl pentanoate to the total amount of trifluorotrichloroethane is 1:1.3-1.5. During the preparation of premix 1, the weight ratio of methyl pentanoate to trifluorotrichloroethane is 1:1-2, the methyl pentanoate accounts for 25-40% of the total amount of methyl pentanoate, and the amount of tert-butyl alcohol is 1-2 times the total weight of methyl pentanoate. Premix 2 is prepared by mixing the remaining methyl pentanoate and trifluorotrichloroethane after preparing premix 1.

[0019] Furthermore, in the step (4), the reaction pressure is 0.25-0.3 MPa, and the reaction stopping condition is that the mass concentration of methyl benzoate is less than 0.5%.

[0020] Furthermore, the recovery step in step (5) of the post-treatment link is to heat to 120-130° C. at normal pressure to recover tert-butyl alcohol and trifluorotrichloroethane, and then cool to 70-110° C. at negative pressure to recover methyl benzoate.

[0021] Furthermore, the washing solution in step (6) of the post-treatment step is a sodium thiosulfate solution.

[0022] Furthermore, the dehydration step in step (7) of the post-treatment link is to carry out reduced pressure dehydration at 70-80° C. to control the water content of 3,3-dimethyl-4,6,6-trichloro-7,7,7-trifluoroheptanoate to be less than 0.1% to obtain the finished product of 3,3-dimethyl-4,6,6-trichloro-7,7,7-trifluoroheptanoate.

[0023] In the prior art, the synthesis of 3,3-dimethyl-4,6,6-trichloro-7,7,7-trifluoroheptanoate uses cuprous chloride as a catalyst mixture for a one-pot reaction. The reaction requires an excessive amount of catalyst and cannot be recycled, which greatly increases the three wastes of the reaction. During the feeding process, cuprous chloride powder will adhere to the pipeline valve, resulting in the ball valve on the pipeline being unable to be strictly sealed, and there are great safety hazards in the workshop production process. The applicant creatively discovered that the catalyst cuprous chloride can be prepared by premixing with monoethanolamine and ethylene glycol to obtain a catalyst with stable properties and fluidity, thereby avoiding the adhesion of cuprous chloride powder to the pipeline valve, thereby improving the safety of the reaction. Furthermore, the applicant has found through long-term research that both the reaction temperature and the reaction time will affect the activity of the catalyst and thus affect the reaction yield. The higher the temperature, the greater the catalyst deactivation rate, and the longer the time, the greater the catalyst deactivation amount. Specifically, the reaction system in the existing one-pot reaction rapidly exothermically heats up to above 120°C and the temperature is difficult to control if the temperature rises too fast, which leads to a large amount of catalyst deactivation, too long reaction time, and low reaction yield. The present application adopts a method of batch premixing and staged temperature increase reaction, firstly initiating the reaction at a low temperature, and then performing a catalytic reaction by double-dropping the remaining materials and increasing the temperature, which can improve the reaction efficiency and shorten the reaction time.

[0024] Compared with the prior art, the present invention has the following beneficial effects:

[0025] (1) The present invention can prepare a catalyst with stable properties and fluidity by premixing cuprous chloride, monoethanolamine and ethylene glycol, which greatly reduces the amount of catalyst used and prevents cuprous chloride powder from adhering to the valve during the feeding process, causing the valve to be loosely closed and causing safety hazards.

[0026] (2) The present invention conducts the reaction in stages. First, a relatively excessive amount of catalyst is added to initiate the reaction at a low temperature. After the reaction is initiated, the remaining catalyst and the reaction raw materials are added dropwise. This can mitigate the violent reaction process and avoid the problem of excessive temperature of the reaction system and subsequent catalyst deactivation due to rapid heat release, thereby greatly reducing the amount of catalyst used. At the same time, since the reaction releases heat slowly, the reaction is safer and more reliable. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 The present invention is a flow chart of the method. DETAILED DESCRIPTION

[0028] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0029] See also Figure 1 As shown, this specific embodiment discloses a method for synthesizing 3,3-dimethyl-4,6,6-trichloro-7,7,7-trifluoroheptanoate, and the overall steps are as follows:

[0030] (1) Catalyst preparation: cuprous chloride is added in batches into a mixture of monoethanolamine and ethylene glycol under the protection of an inert gas, stirring is maintained during the addition process, and the temperature is controlled between 30 and 80° C. After stirring for 30 to 60 minutes, a catalyst is obtained for standby use. Specifically, the molar ratio of methyl benzoate to cuprous chloride is 1:0.03 to 0.05, the molar ratio of cuprous chloride to monoethanolamine is 1:4 to 5, and the weight ratio of cuprous chloride to ethylene glycol is 1:1 to 10.

[0031] (2) Premixing: methyl pentanoate, trifluorotrichloroethane and tert-butyl alcohol are fully mixed to obtain premix 1 for standby use; methyl pentanoate and trifluorotrichloroethane are fully mixed to obtain premix 2 for standby use. The molar ratio of the total amount of methyl pentanoate to the total amount of trifluorotrichloroethane is 1:1.3-1.5. During the preparation of premix 1, the weight ratio of methyl pentanoate to trifluorotrichloroethane is 1:1-2, the methyl pentanoate accounts for 25-40% of the total amount of methyl pentanoate, and the amount of tert-butyl alcohol is 1-2 times the total weight of methyl pentanoate. Premix 2 is prepared by mixing the remaining methyl pentanoate and trifluorotrichloroethane after preparing premix 1.

[0032] (3) Initiate the reaction by adding part of the catalyst prepared in step (1) to the premix 1 in step (2), wherein the amount of the catalyst added is 30% to 50% of the total weight, heating the mixture to 85 to 90° C. under stirring and reacting for 1 hour.

[0033] (4) reaction, the premix 2 in step (2) and the remaining catalyst in step (3) are added dropwise to the reaction solution in step (3) by double addition, and the temperature is raised to 100-105° C. and reacted for 4-6 hours; at this time, the reaction pressure is 0.25-0.3 MPa, and the reaction stopping condition is that the mass concentration of methyl benzoate is less than 0.5%.

[0034] (5) Recovery: distill and recover tert-butyl alcohol, trifluorotrichloroethane and methyl benzoate in the reactants; specifically, heating to 120-130° C. at normal pressure to recover tert-butyl alcohol and trifluorotrichloroethane, and then cooling to 70-110° C. under negative pressure to recover methyl benzoate.

[0035] (6) Layered washing, the remaining product in step (5) is allowed to stand and layer, the lower black oil layer is sent to three wastes for treatment, and the upper organic layer is washed with water to obtain a crude product; preferably, sodium thiosulfate solution can be used for water washing, which can greatly improve the removal efficiency of copper ions in the crude product. Compared with washing with pure water, the copper ion content in the wastewater is 2 to 3 times that of washing with water alone when the addition liquid is washed with a 1% sodium thiosulfate aqueous solution. Depending on the specific product batch and condition, other concentrations of sodium thiosulfate can also be used for washing. In the original process, after the workshop addition product was washed with water once, there was almost no copper ion in the aqueous solution when it was washed with pure water twice, but copper ions were found to be washed out again when washed with 0.5% hydrochloric acid. Pure water can only wash away some water-soluble copper salts, but copper in other forms in the addition product cannot be washed out.

[0036] (7) Dehydration: the organic layer after washing in step (5) is dehydrated to obtain the finished product of 3,3-dimethyl-4,6,6-trichloro-7,7,7-trifluoroheptanoate. Specifically, dehydration is carried out under reduced pressure at 70-80° C., and the water content of 3,3-dimethyl-4,6,6-trichloro-7,7,7-trifluoroheptanoate in the still residue is controlled to be less than 0.1% to obtain the finished product of 3,3-dimethyl-4,6,6-trichloro-7,7,7-trifluoroheptanoate.

[0037] It should be noted that the temperatures and pressures mentioned above are all range values. This is because the reaction temperature does not require overly precise temperature and pressure control, and the reaction process will generate heat and cannot be precisely controlled. Accurately determining a specific temperature and pressure does not conform to the actual situation, is technically difficult to achieve, and is also a redundant operation in this reaction process. For temperature control, it is sufficient to control it within the range value. Therefore, in the embodiments of the present invention, no special examples are given for the end values ​​of the temperature range value.

[0038] Some specific embodiments are provided below to help those skilled in the art to better understand the present invention.

[0039] Example 1

[0040] This specific embodiment discloses a specific implementation process of a method for synthesizing 3,3-dimethyl-4,6,6-trichloro-7,7,7-trifluoroheptanoate, comprising the following steps:

[0041] (1) Catalyst preparation: 4.5 g of cuprous chloride powder was added in batches to a mixture of 11.0 g of monoethanolamine and 22.0 g of ethylene glycol under nitrogen protection, stirring was maintained during the addition process, and the temperature was controlled between 30 and 80° C. After stirring for 45 minutes, the catalyst was obtained for use. At the same time, 160 g of methyl benzoate, 274 g of trifluorotrichloroethane, and 160 g of tert-butyl alcohol were taken for use.

[0042] (2) Premixing: 40 g of methyl benzoate, 40 g of trifluorotrichloroethane and 160 g of tert-butyl alcohol were fully mixed to obtain premix 1 for later use. The remaining 120 g of methyl benzoate and 234 g of trifluorotrichloroethane were fully mixed to obtain premix 2 for later use.

[0043] (3) Initiate the reaction by adding part of the catalyst prepared in step (1) to the premix 1 in step (2), wherein the amount of the catalyst added accounts for 30% of the total weight of the catalyst, heating the mixture to 85-90° C. under stirring and reacting for 1 hour.

[0044] (4) reaction, the premix 2 in step (2) and the remaining catalyst in step (3) are added dropwise to the reaction solution in step (3) by double addition, and then the temperature is raised to 100-105° C. and the reaction is carried out for 4 hours; at this time, the reaction pressure is 0.25-0.3 MPa, and the reaction stopping condition is that the mass concentration of methyl benzoate is less than 0.5%.

[0045] (5) Recovery: distill and recover tert-butyl alcohol, trifluorotrichloroethane and methyl benzoate in the reactants; specifically, heating to 120-130° C. at normal pressure to recover tert-butyl alcohol and trifluorotrichloroethane, and then cooling to 70-110° C. and -0.095 MPa to recover methyl benzoate.

[0046] (6) Layered washing: the remaining product in step (5) is allowed to stand for stratification, and the upper organic layer is washed with 200 g of a 1% sodium thiosulfate aqueous solution and then stratified.

[0047] (7) Dehydration: the organic layer after washing in step (6) is heated to 120-130° C. for dehydration, and the moisture content of 3,3-dimethyl-4,6,6-trichloro-7,7,7-trifluoroheptanoate is controlled to be less than 0.1% to obtain 358.2 g of 3,3-dimethyl-4,6,6-trichloro-7,7,7-trifluoroheptanoate finished product.

[0048] The moisture content of the above product was measured to be 0.04%, and the gas phase detection showed that the finished product content of 3,3-dimethyl-4,6,6-trichloro-7,7,7-trifluoroheptanoate was 97.5%, and the yield was 94.2%.

[0049] Example 2

[0050] This specific embodiment discloses another specific process of a method for synthesizing 3,3-dimethyl-4,6,6-trichloro-7,7,7-trifluoroheptanoate. Compared with Example 1, in step (1), 4.5 g of cuprous chloride, 11.0 g of monoethanolamine, and 4.5 g of ethylene glycol are used. The other conditions are the same, and 353.3 g of the product is obtained in this embodiment. The gas phase detection content is 97.3%, the water content is 0.04%, and the yield is 92.7%.

[0051] Example 3

[0052] This specific embodiment discloses another specific process of a method for synthesizing 3,3-dimethyl-4,6,6-trichloro-7,7,7-trifluoroheptanoate. Compared with Example 1, in step (1), 4.5 g of cuprous chloride, 11.0 g of monoethanolamine, and 45 g of ethylene glycol are used. The other conditions are the same, and 357.5 g of the product is obtained in this embodiment. The gas phase detection content is 97.5%, the water content is 0.04%, and the yield is 94.0%.

[0053] Example 4

[0054] This specific embodiment discloses another specific process of a method for synthesizing 3,3-dimethyl-4,6,6-trichloro-7,7,7-trifluoroheptanoate. Compared with Example 1, in step (2), 40 g of methyl benzoate, 80 g of trifluorotrichloroethane, and 160 g of tert-butyl alcohol are contained in premix 1. In the preparation process of premix 2, 120 g of methyl benzoate and 194 g of trifluorotrichloroethane are contained. The other conditions are the same, and 358.0 g of product is obtained in this embodiment. The gas phase detection content is 97.7%, the water content is 0.04%, and the yield is 94.3%.

[0055] Example 5

[0056] This specific embodiment discloses another specific process of a synthesis method of 3,3-dimethyl-4,6,6-trichloro-7,7,7-trifluoroheptanoate. Compared with Example 1, in step (2), the preparation of premix 1 and premix 2 is cancelled, and 160g of methyl benzoate, 274g of trifluorotrichloroethane, and 160g of tert-butyl alcohol are directly mixed and added to the reactor. Step (3) and step (4) are combined, and the catalyst prepared in step (1) is directly added to the reactor, heated to 85-90°C under stirring and reacted for 1 hour, and then heated to 100-105°C for 6 hours. At this time, the reaction pressure is 0.25-0.3MPa, and the reaction is stopped when the mass concentration of methyl benzoate is detected to be less than 1.0%. The other conditions are the same. This embodiment obtains 348.0g of product, with a gas phase detection content of 97.0%, a moisture content of 0.05%, and a yield of 91.0%. Failure to prepare a premix results in reduced product purity and yield.

[0057] Example 6

[0058] This specific embodiment discloses another specific process of a method for synthesizing 3,3-dimethyl-4,6,6-trichloro-7,7,7-trifluoroheptanoate. Compared with Example 1, the preparation of the catalyst is eliminated in step (1), and the preparation of premix 1 and premix 2 is eliminated in step (2). 160 g of methyl benzoate, 274 g of trifluorotrichloroethane, and 160 g of tert-butyl alcohol are directly mixed and added to the reactor. Step (3) and step (4) are combined, and cuprous chloride, monoethanolamine, and ethylene glycol in step (1) are directly added to the reactor, heated to 85-90° C. under stirring and reacted for 1 hour, and then heated to 100-105° C. and reacted for 6 hours. At this time, the reaction pressure is 0.25-0.3 MPa, and the reaction is stopped when the mass concentration of methyl benzoate is detected to be less than 1.5%. The other conditions were the same, and the product obtained in this example was 342.0 g, with a gas phase content of 96.5%, a moisture content of 0.05%, and a yield of 89%. Failure to prepare a catalyst and a premix resulted in reduced product purity and yield.

[0059] The present invention performs the reaction in stages, firstly prepares a catalyst with stable properties and fluidity, then adds a relatively excessive amount of catalyst to initiate the reaction at low temperature, and finally adds the remaining catalyst and the reaction raw materials in double drops. This avoids the problems of low efficiency of generating a catalyst after adding cuprous chloride and ethanolamine in one pot, high catalyst deactivation rate due to excessively fast temperature rise after the reaction is initiated, and thus low reaction yield, and safety accidents that are prone to occur during production.

[0060] The embodiments of the present invention are described in detail above with reference to the accompanying drawings, but the present invention is not limited to the described embodiments. For those skilled in the art, various changes, modifications, substitutions and variations of these embodiments are made without departing from the principles and spirit of the present invention, and still fall within the scope of protection of the present invention.

Claims

1. A method for synthesizing 3,3-dimethyl-4,6,6-trichloro-7,7,7-trifluoroheptanoate, characterized in that: 3,3-Dimethyl-4,6,6-trichloro-7,7,7-trifluoroheptanoate was prepared by the following steps: (1) Catalyst preparation: under the protection of inert gas, solid cuprous chloride is added in batches into a mixture of monoethanolamine and ethylene glycol, stirring is maintained during the addition process, and the temperature is controlled between 30 and 80° C. After stirring for 30 to 60 minutes, the catalyst is obtained for standby use; (2) premixing: methyl benzoate, trifluorotrichloroethane and tert-butyl alcohol are fully mixed to obtain a premix solution 1 for standby use; methyl benzoate and trifluorotrichloroethane are fully mixed to obtain a premix solution 2 for standby use; (3) initiating the reaction, adding part of the catalyst prepared in step (1) to the premixed solution 1 in step (2), wherein the amount of the catalyst added accounts for 15% to 35% of the total amount, heating the mixture to 85 to 90° C. under stirring and reacting for 1 hour; (4) reacting, adding the premix 2 in step (2) and the remaining catalyst in step (3) to the reaction solution in step (3) by double dropwise addition, heating to 100-105° C. and reacting for 4-6 hours; (5) recovering the tert-butyl alcohol, trifluorotrichloroethane and methyl benzoate in the reaction system by distillation; (6) washing by stratification, the remaining product in step (5) is allowed to stand for stratification, and the upper organic layer is washed with water to obtain a crude product of 3,3-dimethyl-4,6,6-trichloro-7,7,7-trifluoroheptanoate; (7) Dehydration: the organic layer after washing in step (5) is dehydrated to obtain the finished product of 3,3-dimethyl-4,6,6-trichloro-7,7,7-trifluoroheptanoate.

2. The method for synthesizing 3,3-dimethyl-4,6,6-trichloro-7,7,7-trifluoroheptanoate according to claim 1, characterized in that: The recovery step in step (5) is to heat to 120-130° C. at normal pressure to recover tert-butyl alcohol and trichlorotrifluoroethane, and then cool to 70-110° C. at negative pressure to recover methyl benzoate.

3. The method for synthesizing 3,3-dimethyl-4,6,6-trichloro-7,7,7-trifluoroheptanoate according to claim 1, characterized in that: The dehydration step in step (7) is to perform reduced pressure dehydration at 70-80° C. to control the water content of 3,3-dimethyl-4,6,6-trichloro-7,7,7-trifluoroheptanoate to less than 0.1% to obtain the finished product of 3,3-dimethyl-4,6,6-trichloro-7,7,7-trifluoroheptanoate.

4. The method for synthesizing 3,3-dimethyl-4,6,6-trichloro-7,7,7-trifluoroheptanoate according to claim 1, characterized in that: In the step (1), the molar ratio of methyl benzoate to cuprous chloride is 1:0.03-0.05, the weight ratio of cuprous chloride to monoethanolamine is 1:4-5, and the weight ratio of cuprous chloride to ethylene glycol is 1:1-10.

5. The method for synthesizing 3,3-dimethyl-4,6,6-trichloro-7,7,7-trifluoroheptanoate according to claim 1, characterized in that: In the step (2) of preparing the premix 1, the weight ratio of methyl pentanoate to trichlorotrifluoroethane is 1:1-2, and the methyl pentanoate accounts for 25-40% of the total amount of methyl pentanoate.

6. The method for synthesizing 3,3-dimethyl-4,6,6-trichloro-7,7,7-trifluoroheptanoate according to claim 1, characterized in that: In the reaction step (4), the reaction pressure is 0.25-0.3 MPa, and the reaction stopping condition is that the mass concentration of methyl benzoate is less than 0.5%.

7. The method for synthesizing 3,3-dimethyl-4,6,6-trichloro-7,7,7-trifluoroheptanoate according to claim 1, characterized in that: The water washing liquid in step (6) is a sodium thiosulfate solution.

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