Process for the preparation of octafluorocyclopentene

Abstract

The application discloses a preparation method of octafluorocyclopentene, and reaction is carried out in two steps. First, 4-cyclopentene-1,3-dione is reacted with a selective fluorine reagent under reflux in acetonitrile to generate a crude product, a second mixture, the second mixture is purified and then is put into a second step reaction, and is reacted with diethylamine sulfide in dichloromethane to generate a third mixture. The reaction process is environment-friendly and simple, basically no three wastes are generated, is cheap and easy to obtain, the reaction process is simple and mild, nitrogen protection is needed and no waste gas pollution is generated, the method is easy to operate, and is suitable for industrial production.

Description

TECHNICAL FIELD

[0001] The application belongs to the field of fine chemical industry, and particularly relates to a preparation method of octafluorocyclopentene. BACKGROUND

[0002] Octafluorocyclopentene is an important fine chemical product, and the compound has high stability and inertness, can be used as a solvent in some anhydrous and oxygen-free reactions in chemical reactions. In addition, the product can also be used as an electronic material, has high electron affinity, can form a stable pi electron system, and has electron transport capacity. It is widely used in the preparation of electronic materials, such as the synthesis of polymer electronic materials, the improvement of electrode materials, etc. In addition, due to its excellent environmental performance and working performance, it is used as a high-quality semiconductor etching and cleaning agent in the field of integrated circuits and participates in the production of semiconductors, which is crucial for improving the performance and reliability of semiconductor devices, and has great potential market and development prospect.

[0003] The industrial production method discloses a synthesis method of octafluorocyclopentene, mainly fluorine-chlorine exchange method (as shown in chemical reaction path 1), and the process is to use hexachlorocyclopentadiene as a raw material. The raw material belongs to a toxic controlled drug, and the raw material is difficult to purchase. Chlorine and hydrogen fluoride are used in the first step of preparation, and both belong to high-toxicity corrosive materials. Potassium fluoride is used in the second step, and also belongs to a fluorine-containing corrosive material. Both steps are carried out under high temperature conditions, and the process has high danger and large operation difficulty. At the same time, the process method will produce three wastes containing corrosive acid gas, which needs to be absorbed by a large amount of lye, and brings great trouble to the treatment of three wastes.

[0004] Chemical reaction path 1:

[0005] SUMMARY

[0006] In view of the fact that the raw material for preparing octafluorocyclopentene in the prior art is difficult to purchase, and the raw material may also be toxic, and many pollutants are generated in the reaction process, the application provides a preparation method of octafluorocyclopentene, which can avoid the use of dangerous materials such as toxic and highly corrosive materials, and also reduces the discharge of three wastes.

[0007] The technical scheme of the application is:

[0008] A preparation method of octafluorocyclopentene,

[0009] S1. 4-cyclopentene-1,3-dione and a selective fluorine reagent are added to a solvent one, heated and reacted, refluxed and condensed, cooled to room temperature after the reaction is completed, and quenched with water;

[0010] S2. The solution after quenching with water is extracted with ethyl acetate, the organic phase is washed with saturated sodium chloride solution, dried, and the ethyl acetate is removed by distillation under reduced pressure to obtain a second mixture crude product;

[0011] S3. The second mixture crude product is purified by column chromatography, and the mobile phase is distilled off under reduced pressure to obtain a second mixture pure product;

[0012] S4. The second mixture pure product is reacted with diethylamine sulfide in solvent two to form a third mixture.

[0013] Preferably, in S1, the solvent one is dried in an oven-dried 3A molecular sieve for not less than 16 hours before use, so that the water content in the solvent is reduced to below 100 ppm;

[0014] The 4-cyclopenten-1,3-dione and the selective fluorine reagent are added to a reactor containing the solvent one, the reactor is replaced with nitrogen gas for more than 3 times to remove the water and air in the reaction solution, and the reaction process is continuously stirred under heating;

[0015] The condensation temperature during the reflux condensation process is between -30 and 10℃.

[0016] Preferably, in S1, the solvent one is one of acetonitrile, dichloromethane, carbon tetrachloride and dimethyl sulfoxide;

[0017] The solvent one is acetonitrile, the heating reaction temperature is maintained at 78-100℃, and the reaction time is 8-16 hours;

[0018] The solvent one is dichloromethane, the heating reaction temperature is maintained at 20-40℃, and the reaction time is 16-46 hours;

[0019] The solvent one is carbon tetrachloride, the heating reaction temperature is maintained at 20-78℃, and the reaction time is 8-32 hours;

[0020] The solvent one is dimethyl sulfoxide, the heating reaction temperature is maintained at 20-100℃, and the reaction time is 8-16 hours 。

[0021] Preferably, in S1, the mass ratio of 4-cyclopenten-1,3-dione to the selective fluorine reagent is 1:(1.2-3);

[0022] The volume mL of the solvent one to the mass g of 4-cyclopenten-1,3-dione is 10-50:1;

[0023] The volume ratio of the solvent one to water is 1:1-5.

[0024] Preferably, in S2, the volume ratio of the water used for quenching to ethyl acetate is 1:1-15;

[0025] The solution after quenching with water is extracted with ethyl acetate three times;

[0026] The volume ratio of saturated sodium chloride solution to ethyl acetate is 1:2-3;

[0027] The organic phase after water washing with saturated sodium chloride solution is dried with anhydrous sodium sulfate, and the volume of saturated sodium chloride solution (mL) to the mass of anhydrous sodium sulfate (g) is 100:1-15.

[0028] The temperature of the reduced pressure distillation is 40℃, and the vacuum degree is -0.1MPa.

[0029] Preferably, in S3, the chromatographic column is used for purification, and the mesh number of the silica gel powder is 200-1000 mesh; during the column chromatography purification, the mobile phase is a mixture of ethyl acetate and petroleum ether, and the volume ratio of ethyl acetate to petroleum ether is 1:50-200;

[0030] The mobile phase is evaporated to dryness by a rotary evaporator at the end of the purification;

[0031] The temperature of the reduced pressure distillation is 40℃, and the pressure is -0.1MPa.

[0032] Preferably, the specific steps of S4 are as follows: the second mixture is added to solvent two for ice bath, the temperature of the ice bath is 0℃ or below, diethylamine sulfide is added to the ice bath reaction at a rate of 1-5 drops per second, stirring is started, the ice bath is removed, the temperature is allowed to rise to 20-100℃, stirring is performed for 2-7h, the condensate is collected, the condensate collection temperature is controlled at 0℃ or below, and the collected condensate is the third mixture, which is the crude octafluorocyclopentene product.

[0033] Preferably, in S4, the solvent two is one of dichloromethane, carbon tetrachloride, tetrahydrofuran and 1,4-dioxane.

[0034] Preferably, the solvent two is dichloromethane, and the reaction temperature is 20-40℃;

[0035] The solvent two is carbon tetrachloride, and the reaction temperature is 30-70℃;

[0036] The solvent two is tetrahydrofuran, and the reaction temperature is 20-66℃;

[0037] The solvent two is 1,4-dioxane, and the reaction temperature is 20-100℃.

[0038] Preferably, in S4, the molar ratio of the second mixture to diethylamine sulfide is 1:(2-3);

[0039] The volume ratio of the second mixture (g) to the solvent two (mL) is 1:10-50. mL

[0040] ​The reaction equation of the present application is:

[0041]

[0042]

[0043] The beneficial effects of the present application are:

[0044] The process of the present application has high safety, low production cost, strong process operability, less reaction waste, mild reaction conditions, and the solvents generated during reaction and purification can be recycled and utilized, and the reaction can be carried out under normal pressure with high yield.

[0045] In the present application, the reactants are fully reacted, the pollution during synthesis is reduced, the post-treatment is simple, and the solvent can be recycled, which belongs to a green synthesis process.

[0046] The present application has low cost and high raw material utilization rate. Compared with the original traditional synthesis process, the present process does not involve high-risk and high-corrosive materials such as chlorine and hydrogen fluoride, and a large amount of acidic waste gas is not generated during reaction. This method adopts a two-step synthesis process, and the process route is short, the reaction process is relatively environmentally friendly and simple, and the solvent and purification reagent can be recycled. The raw materials used in the present application are common chemical raw materials, which are cheap and easy to obtain. The reaction process is simple and mild, no waste gas pollution is generated, it is easy to operate, and it is suitable for industrial production. DETAILED DESCRIPTION

[0047] Example 1

[0048] In step one, 100 mL of dry acetonitrile was added to a 250 mL three-necked flask, and the acetonitrile was dried in a 3A molecular sieve for 16 h before use to reduce the water content in the acetonitrile to below 100 ppm;

[0049] The raw material 4-cyclopenten-1,3-dione (9.6 g, 0.1 mol, 1 eq.) was added to the three-necked reaction flask containing acetonitrile at 20℃, and a condenser tube (condensation temperature 10℃) and a thermometer were added to the reaction flask. Nitrogen was inserted into the condenser tube, and the reactor was replaced with nitrogen for 3 times to remove the water and air in the reaction liquid.

[0050] The heating was started, and the reaction flask was heated to 81℃, and the reaction was continuously stirred for 16 h.

[0051] In step two, after the experiment was stopped and the temperature was lowered to room temperature, 100 mL of water was added to quench the reaction, and then 300 mL of ethyl acetate was added to extract three times, and the organic phase was combined and washed with 100 mL of saturated sodium chloride solution three times. The organic phase was dried with 15 g of anhydrous sodium sulfate, and the ethyl acetate was removed by distillation under reduced pressure at a temperature of 40℃ and a pressure of -0.01 MPa.

[0052] Step three, purification by chromatography column, the silica gel powder used in the purification is 200 mesh, the developing agent flow phase ratio (volume ratio) is ethyl acetate: petroleum ether = 1:50, the mixed flow phase of ethyl acetate and petroleum ether is evaporated by a rotary evaporator at the end of purification, and a second mixture pure product 9.8 g with a purity of 85% and a yield of 70% is obtained.

[0053] Step four, the second mixture (9.8 g, 0.07 mol, 1.0 eq.) purified is added to a 300 mL dichloromethane two-port flask, a distillation collection device is built, the condenser tube condensing liquid temperature is controlled at 0°C, the two-port flask is placed in an ice bath (0°C), diethylamine sulfide (21.91 g, 0.14 mol, 2.0 eq.) is slowly added to the reactor at 1-5 drops per second, stirring is started, the ice bath is removed, and the temperature is gradually increased to 38°C, and stirring is performed for 5 h.

[0054] The condenser tube condensing temperature is 0°C, and octafluorocyclopentene 13.22 g with a purity of 87.5% and a yield of 89.1% is collected in the conical flask.

[0055] Example 2

[0056] Step one, 1500 mL of dry dimethyl sulfoxide is added to a 2000 mL three-port flask, and the dimethyl sulfoxide is dried in an oven-dried 3A molecular sieve for 16 h before use to reduce the water content in the dimethyl sulfoxide to below 100 ppm;

[0057] The raw material 4-cyclopentene-1,3-dione (19.2 g, 0.2 mol, 1 eq.) is added to the three-port reaction flask containing dimethyl sulfoxide at 20°C, a condenser tube (condensing temperature -30°C) and a thermometer are added to the reaction flask, nitrogen gas is inserted into the condenser tube port, and the reactor is replaced with nitrogen gas for 3 times to remove the water and air in the reaction liquid;

[0058] The heating is started, and the reaction flask is heated to 100°C, and the reaction is continuously stirred for 8 h.

[0059] Step two, after the experiment is stopped, the temperature is lowered to room temperature, 3500 mL of water is added for quenching, 6000 mL of ethyl acetate is added for extraction three times, the organic phase is combined, washed with 2000 mL of saturated sodium chloride solution three times, the organic phase is dried with 20 g of anhydrous sodium sulfate, and the ethyl acetate is removed by distillation under reduced pressure.

[0060] Step three, purification by chromatography column, the silica gel powder used in the purification is 1000 mesh, the developing agent flow phase ratio (volume ratio) is ethyl acetate: petroleum ether = 1:100, the purified second mixture is obtained by evaporating the mixed flow phase of ethyl acetate and petroleum ether under the condition of temperature 40℃ and pressure-0.01MPa by using a rotary evaporator, the second mixture is 26.8g, the purity is 91.2%, and the yield is 95.7%.

[0061] Step four, the purified second mixture (26.8g, 0.19mol, 1.0eq.) is added into a 1000mL 1,4-dioxane double-mouth flask, a distillation collection device is built, the condenser tube condensing liquid temperature is controlled at-10℃, the double-mouth flask is placed in an ice bath (0℃), diethylamine sulfide trifluoride (59.47g, 0.38mol, 2.0eq.) is slowly added into the reactor at 1-5 drops per second, stirring is started, the ice bath is removed, and the temperature is gradually increased to 68℃, and stirring is performed for 2h.

[0062] The condensing temperature of the condenser tube is-10℃, and the octafluorocyclopentene generated in the reaction is collected in the conical flask, which is 32.9g, the purity is 81.9%, and the yield is 81.7%.

[0063] Example 3

[0064] Step one, 3000mL of dry carbon tetrachloride is added into a 5000mL three-neck flask, the carbon tetrachloride is dried in an oven-dried 3A molecular sieve for 16h before use, so that the water content in the carbon tetrachloride is reduced to below 100ppm;

[0065] The raw material 4-cyclopentene-1,3-dione (28.8g, 0.3mol, 1eq.) and the selective fluorine reagent (318.6g, 0.9mol, 3.0eq.) are added into the three-neck reaction flask containing the carbon tetrachloride at 20℃, a condenser tube (condensing temperature 0℃) and a thermometer are added into the reaction flask, nitrogen gas is inserted into the condenser tube, and the reactor is replaced with nitrogen gas for 3 times to remove the water and air in the reaction liquid;

[0066] The heating is started, the reaction flask is heated to 78℃, and the reaction is continuously stirred for 12h.

[0067] Step two, after the experiment is stopped, the temperature is decreased to room temperature, 3500mL of water is added for quenching, 6000mL of ethyl acetate is added for extraction for three times, the organic phase is combined, washed with 3000mL of saturated sodium chloride solution for three times, the organic phase is dried with 30g of anhydrous sodium sulfate, and the ethyl acetate is removed by vacuum distillation under the condition of temperature 40℃ and pressure-0.01MPa.

[0068] Step three, purification by chromatography column, the silica gel powder used for purification has a mesh number of 800 mesh, the developing solvent mobile phase ratio (volume ratio) is ethyl acetate: petroleum ether = 1:200, and the purification is completed by rotary evaporation of the mobile phase mixed with ethyl acetate and petroleum ether to dryness to obtain 38.9 g of the second pure mixture with a purity of 89.7% and a yield of 92.6%.

[0069] Step 4: The purified second mixture (38.9 g, 0.28 mol, 1.0 eq.) was added to a two-necked flask containing 5000 mL of tetrahydrofuran. A distillation collection device was set up. The condensate temperature of the condenser was controlled at -20 ° C. The two-necked flask was placed in an ice bath (0 ° C). Diethylaminosulfur trifluoride (133.6 g, 0.83 mol, 3.0 eq.) was slowly added to the reactor at a rate of 1 to 5 drops per second. Stirring was started, the ice bath was removed, the temperature was gradually raised to 66 ° C, and stirred for 7 h.

[0070] The condensation temperature of the condenser was -20°C, and 46.9 g of octafluorocyclopentene produced by the reaction was collected in a conical flask with a purity of 72.3% and a yield of 79.1%.

[0071] Comparative Example 1

[0072] Step 1: Add the raw material 4-cyclopentene-1,3-dione (9.6 g, 0.1 mol, 1 eq.) and the selective fluorine reagent (42.5 g, 0.12 mol, 1.2 eq.) to a three-necked reaction flask containing undried acetonitrile at 20 ° C. The reaction flask is added with a condenser (condensation temperature 10 ° C.) and a thermometer. Three nitrogen ports are inserted into the condenser ports. The reactor is purged with nitrogen three times to remove moisture and air from the reaction solution.

[0073] The heating was turned on to heat the reaction flask to 81°C and the reaction was stirred for 16 hours.

[0074] Step 2: After the experiment is stopped, the mixture is cooled to room temperature, quenched with 100 mL of water, and extracted three times with 300 mL of ethyl acetate. The organic phases are combined and washed three times with 100 mL of saturated sodium chloride solution. The organic phases are dried over anhydrous sodium sulfate and the ethyl acetate is removed by distillation under reduced pressure.

[0075] Step three, purification by chromatography column, the silica gel powder used for purification has a mesh number of 200 mesh, the developing solvent mobile phase ratio (volume ratio) is ethyl acetate: petroleum ether = 1:50, the purification end temperature is 44 ° C and the pressure is -0.01 MPa. The mobile phase mixed with ethyl acetate and petroleum ether is evaporated to dryness using a rotary evaporator to obtain 6.2 g of the second pure mixture with a purity of 78.6% and a yield of 44.28%.

[0076] Step four, the purified second mixture (6.2 g, 0.044 mol, 1.0 eq.) was added to a 300 mL flask of dichloromethane, a distillation collection device was set up, the condenser tube was cooled to 0°C, the double-necked flask was placed in an ice bath (0°C), and diethylamine sulfide trifluoride (13.77 g, 0.088 mol, 2.0 eq.) was slowly added to the reactor at a rate of 1-5 drops per second. The stirring was started, the ice bath was removed, and the temperature was gradually increased to 38°C. The stirring was continued for 5 hours.

[0077] The condenser tube was cooled to 0°C, and the octafluorocyclopentene produced in the reaction was collected in the conical flask. The purity was 81.5%, and the yield was 73.9%.

[0078] Comparative Example 2

[0079] Step one, 100 mL of dry acetonitrile was added to a 250 mL three-necked flask. The acetonitrile was dried in an oven-dried 3A molecular sieve for 16 hours before use to reduce the water content in the acetonitrile to less than 100 ppm;

[0080] The raw material 4-cyclopentene-1,3-dione (9.6 g, 0.1 mol, 1 eq.) was added to a three-necked flask containing acetonitrile at 20°C, and a condenser tube (condenser temperature 10°C) and a thermometer were added to the reaction flask. Nitrogen was inserted into the condenser tube.

[0081] The heating was turned on, and the reaction flask was heated to 81°C. The stirring was continued for 16 hours.

[0082] Step two, after the experiment was stopped, the temperature was lowered to room temperature, 100 mL of water was added to quench the reaction, and then 300 mL of ethyl acetate was added to extract three times. The organic phase was combined and washed with 100 mL of saturated sodium chloride solution three times. The organic phase was dried with 50 g of anhydrous sodium sulfate, and the ethyl acetate was removed by distillation under reduced pressure at a temperature of 40°C and a pressure of -0.01 MPa.

[0083] Step three, the purified product was obtained by column chromatography. The silica gel powder used for purification had a mesh size of 200 mesh, and the developing agent flow phase ratio (volume ratio) was ethyl acetate: petroleum ether = 1:50. After purification, the flow phase mixture of ethyl acetate and petroleum ether was evaporated using a rotary evaporator to obtain a second mixture of 7.7 g, with a purity of 80.1% and a yield of 55%.

[0084] Step four, the purified second mixture (7.7 g, 0.055 mol, 1.0 eq.) was added to a 300 mL flask of dichloromethane, a distillation collection device was set up, the condenser tube was cooled to 0°C, the double-necked flask was placed in an ice bath (0°C), and diethylamine trifluoride (17.21 g, 0.11 mol, 2.0 eq.) was slowly added to the reactor at a rate of 1-5 drops per second. The stirring was started, the ice bath was removed, and the temperature was gradually increased to 38°C. The stirring was continued for 5 hours.

[0085] The condenser tube was cooled to 0°C, and the octafluorocyclopentene produced in the reaction was collected in a conical flask. The purity was 64.4%, and the yield was 60.0%.

[0086] Comparative Example 3

[0087] Step one, 100 mL of dry acetonitrile was added to a 250 mL three-necked flask. The acetonitrile was dried in an oven-dried 3A molecular sieve for 16 hours before use to reduce the water content in the acetonitrile to less than 100 ppm.

[0088] The raw material 4-cyclopentene-1,3-dione (9.6 g, 0.1 mol, 1 eq.) was added to a three-necked flask containing acetonitrile at 20°C, and the reaction flask was equipped with a condenser tube (condenser temperature 10°C) and a thermometer. Nitrogen was inserted into the condenser tube, and the reactor was replaced with nitrogen three times to remove the water and air in the reaction solution.

[0089] The heating was turned on, and the reaction flask was heated to 81°C. The stirring was continued for 16 hours.

[0090] Step two, after the experiment was stopped, the temperature was lowered to room temperature, 100 mL of water was added to quench the reaction, and then 300 mL of ethyl acetate was added to extract the reaction solution three times. The organic phase was washed with 100 mL of saturated sodium chloride solution three times, dried over anhydrous sodium sulfate, and then the ethyl acetate was removed by distillation under reduced pressure.

[0091] Step three, the purified product was obtained by column chromatography. The silica gel powder used for purification had a mesh size of 200 mesh, and the developing agent flow phase ratio (volume ratio) was ethyl acetate: petroleum ether = 1:50. After the purification was completed, the mixed flow phase of ethyl acetate and petroleum ether was evaporated using a rotary evaporator to obtain the second mixture pure product 7.3 g, with a purity of 79.7% and a yield of 52.1%.

[0092] Step four, the purified second mixture (7.3 g, 0.05 mol, 1.0 eq.) was added to a 300 mL dichloromethane two-port flask, a distillation collection device was set up, the condenser tube was not placed with coolant, 25℃ air condensation, 1-5 drops of diethylamine sulfur trifluoride (18.78 g, 0.12 mol, 2.0 eq.) was slowly added to the reactor every second, stirring was started, the temperature was gradually increased to 38℃, and stirring was continued for 5 h.

[0093] 25℃ was collected, the octafluorocyclopentene produced by the reaction was collected in a conical flask, 5.73 g, purity 68.5%, yield 54.05%.

[0094] In summary, the above is only a preferred embodiment of the present application, and is not intended to limit the scope of protection of the present application. Any modification, equivalent replacement, improvement, etc. made within the spirit and principles of the present application shall be included in the scope of protection of the present application.

Claims

1. A method for preparing octafluorocyclopentene, characterized in that: S1. Add 4-cyclopentene-1,3-dione and a selective fluorine reagent to solvent 1, heat to react, reflux and condense, cool to room temperature after the reaction, and quench with water; S2. After quenching with water, the solution was extracted with ethyl acetate, and the organic phase was washed with a saturated sodium chloride solution, dried, and ethyl acetate was removed by distillation under reduced pressure to obtain a second crude mixture; S3. The crude second mixture was purified by column chromatography, and the mobile phase was distilled off under reduced pressure to obtain a pure second mixture; S4. The pure second mixture is reacted with diethylaminosulfur trifluoride in solvent 2 to produce a third mixture, namely crude octafluorocyclopentene.

2. The method for preparing octafluorocyclopentene according to claim 1, wherein: In S1, solvent 1 is dried in dried 3A molecular sieve for not less than 16 hours before use to reduce the moisture content of the solvent to below 100 ppm; 4-cyclopentene-1,3-dione and a selective fluorine reagent are added to a reactor containing solvent 1, and the gas in the reactor is replaced with nitrogen for more than 3 times to remove moisture and air from the reaction solution; Stir continuously during the heating reaction; The condensation temperature during the reflux condensation process is between -30 and 10°C.

3. The method for preparing octafluorocyclopentene according to claim 2, wherein: In S1, the solvent 1 is one of acetonitrile, dichloromethane, carbon tetrachloride and dimethyl sulfoxide; When the first solvent is acetonitrile, the heating reaction temperature is maintained at 78-100°C, and the reaction time is 8-16 hours; When the solvent is dichloromethane, the heating reaction temperature is maintained at 20°C to 40°C, and the reaction time is 16 to 46 hours; When the first solvent is carbon tetrachloride, the heating reaction temperature is 20°C to 78°C, and the reaction time is 8 to 32 hours; When the first solvent is dimethyl sulfoxide, the heating reaction temperature is 20-100° C., and the reaction time is 8-16 hours.

4. The method for preparing octafluorocyclopentene according to claim 1, wherein: In S1, the molar ratio of 4-cyclopentene-1,3-dione:selective fluorine reagent is 1:(1.2~3); The mass ratio of solvent volume to 4-cyclopentene-1,3-dione is 10-50:1 (mL:g); The volume ratio of solvent 1 to water is 1:1~5.

5. The method for preparing octafluorocyclopentene according to claim 1, wherein: In S2, the volume ratio of water to ethyl acetate for quenching is 1:1~15; After quenching with water, the solution was extracted three times with ethyl acetate; The volume ratio of saturated sodium chloride solution to ethyl acetate is 1:2~3; The organic phase after washing with saturated sodium chloride solution is dried over anhydrous sodium sulfate, and the ratio of the volume of saturated sodium chloride solution to the mass of anhydrous sodium sulfate is 100:1-15 (mL:g); The temperature of the reduced pressure distillation was 40°C and the vacuum degree was -0.1 MPa.

6. The method for preparing octafluorocyclopentene according to claim 1, wherein: In S3, purification was performed using a chromatography column with a silica gel powder size of 200-1000 mesh; During column chromatography purification, the mobile phase was a mixture of ethyl acetate and petroleum ether, with a volume ratio of ethyl acetate:petroleum ether of 1:50-200; After purification, the mobile phase was evaporated to dryness using a rotary evaporator; The temperature of the reduced pressure distillation was 40°C and the pressure was -0.1 MPa.

7. The method for preparing octafluorocyclopentene according to claim 1, wherein: The specific steps of S4 are as follows: adding the second mixture to solvent two and placing it in an ice bath; the temperature of the ice bath is 0°C or below; adding diethylaminosulfur trifluoride 1 to 5 drops per second to the ice bath reaction; starting stirring; removing the ice bath; raising the temperature to 20-100°C; stirring the reaction for 2-7 hours; condensing and collecting the condensate; controlling the collection temperature of the condensate at 0°C or below; and collecting the condensate produced by the reaction as the third mixture, i.e., crude octafluorocyclopentene.

8. The method for preparing octafluorocyclopentene according to claim 1, wherein: In S4, the second solvent is one of dichloromethane, carbon tetrachloride, tetrahydrofuran and 1,4-dioxane.

9. The method for preparing octafluorocyclopentene according to claim 8, wherein: When the second solvent is dichloromethane, the reaction temperature is 20-40°C; When the second solvent is carbon tetrachloride, the reaction temperature is 30-70°C; When the second solvent is tetrahydrofuran, the reaction temperature is 20-66°C; When the second solvent is 1,4-dioxane, the reaction temperature is 20-100°C.

10. The method for preparing octafluorocyclopentene according to claim 1, wherein: In S4, the molar ratio of the second mixture of pure product and diethylamino sulfur trifluoride is 1: (2 to 3); The mass ratio of the second mixture to the volume of the second solvent is 1:10-50 (g:mL).

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