Preparation method of perfluoroisobutyl methyl ether

Abstract

The invention discloses a preparation method of perfluoroisobutyl methyl ether, which relates to the technical field of fluorine chemical industry, and comprises the following steps: 1) carrying out addition reaction on hexafluoropropylene and chloroformate as raw materials under the action of villiaumite to prepare heptafluoroisobutyrate; 2) hydrolyzing the heptafluoroisobutyrate under the action of alkali to obtain heptafluoroisobutyric acid; 3) preparing a key intermediate heptafluoroisobutyryl chloride from heptafluoroisobutyric acid under the action of an acylation reagent; and 4) reacting the key intermediate heptafluoroisobutyryl chloride with a methylation reagent under the action of alkali metal fluoride to prepare the perfluoroisobutyl methyl ether. The perfluoroisobutyl methyl ether is prepared by constructing the key intermediate heptafluoroisobutyryl chloride, the used raw materials hexafluoropropylene and chloroformate are cheap and easy to obtain, and the production cost is greatly reduced. According to the method, the key intermediate heptafluoroisobutyryl chloride can be rapidly and efficiently constructed, the reaction conversion rate of each step is high, the product is easy to separate and purify, the yield and purity of the product are effectively improved, and the method is suitable for industrial production.

Description

Technical Field

[0001] The invention relates to the technical field of fluorine chemical industry, and in particular to a method for preparing perfluoroisobutyl methyl ether. Background Art

[0002] Electronic fluorinated liquid is a colorless and transparent liquid that has both moderate solubility and good material compatibility, an ozone potential (ODP) of 0, and a low global warming potential (GWP). It is mainly composed of fluorides and has the characteristics of being non-conductive, non-flammable, non-toxic, and residue-free, as well as having thermal and chemical stability. These characteristics make electronic fluorinated liquid very suitable for use in high-tech fields such as semiconductor wafer manufacturing, electronic reliability testing, and immersion cooling of data center servers. With the deepening of the replacement of chlorofluorocarbons such as CFC and HCFC, 3M has developed a hydrofluoroether product, Novec TM HFE-7100 / 7200 / 7300 / 7500 (the chemical structures of HFE-7100, 7200, 7300, and 7500 are perfluoroisobutyl methyl ether, perfluoroisobutyl ethyl ether, perfluorohexyl methyl ether, and perfluoroheptyl ethyl ether, respectively) are designated as Acceptable (can be used without restrictions) as cleaning agents and refrigerants in the Freon Alternatives List (SNAP List) determined by the EPA (U.S. Environmental Protection Agency), providing an ideal solution for companies that promote green procurement.

[0003] There are few publicly available synthetic routes for perfluoroisobutyl methyl ether HFE-7100, which can be roughly divided into four technical routes:

[0004] 1) First, a fluorinated olefin such as heptafluoroisobutylene methyl ether or hexafluoromonochloroisopropenyl methyl ether is constructed, and then it is added with fluorine gas / cobalt fluoride (patent CN107382678; document Synlett 2000, 3, 343-344) or hydrofluoric acid (patent CN111995502) to obtain the reaction equation as follows:

[0005]

[0006] 2) First, perfluoroisobutyryl fluoride / perfluoroisobutyryl chloride is constructed, and then reacted with a methylating agent under the action of an alkali metal to obtain the product. The raw material for constructing perfluoroisobutyryl fluoride is hexafluoropropylene dimer (patent CN109503366, CN117567252), hexafluoropropylene trimer (patent CN109534966, CN109734562), or directly using perfluoroisobutyryl fluoride (patent CN110002968, CN116178116, US2004192974; Journal of Fluorine Chemistry 2005, 126, 1578-1586); the raw material for constructing perfluoroisobutyryl chloride is phosgene (patent CN115521192), and the reaction equation is as follows:

[0007]

[0008] 3) First, 2,2-difluoro-3,3-bis(trifluoromethyl)oxirane is constructed, and then reacted with a methylating agent under the action of an alkali metal to obtain (patent CN117486683), and the reaction equation is as follows:

[0009]

[0010] 4) Prepared by atom exchange between hydrofluoric acid and corresponding halogenated alkane (patent CN116693371).

[0011]

[0012] The conclusion that can be drawn from the above four technical routes is: first construct the key intermediate perfluoroisobutyryl fluoride / perfluoroisobutyryl chloride, and then react with a methylating agent under the action of an alkali metal to prepare perfluoroisobutyl methyl ether. This method is relatively simple and widely used compared to other process routes. Disadvantages of other process routes: 1) Process route one and process route four use highly toxic and corrosive F2 and HF, which have a high risk factor and demanding requirements on reaction equipment; 2) Process route three is relatively simple, but the preparation of the raw material octafluoroisobutylene is more difficult. Therefore, the key to the research is to more conveniently and quickly construct perfluoroisobutyryl fluoride / perfluoroisobutyryl chloride in technical route two. Summary of the invention

[0013] The main purpose of the present invention is to provide a method for synthesizing perfluoroisobutyl methyl ether HFE-7100. The present invention uses hexafluoropropylene as a raw material and synthesizes nonafluoroisobutyl ether through a four-step reaction. The method has cheap and readily available raw materials, simple process operation, mild reaction conditions, high yield, and is easier to realize industrial production.

[0014] In order to achieve the above object, the technical solution adopted by the present invention is:

[0015] The present invention provides a method for synthesizing perfluoroisobutyl methyl ether, comprising the following steps:

[0016] Step 1: using hexafluoropropylene and chloroformate as raw materials, heptafluoroisobutyrate is prepared by addition reaction under the action of fluoride salt;

[0017] Step 2: hydrolyzing heptafluoroisobutyrate under the action of a base to obtain heptafluoroisobutyric acid;

[0018] Step 3: Heptafluoroisobutyric acid is reacted with an acylating agent to prepare the key intermediate heptafluoroisobutyryl chloride;

[0019] Step 4: The key intermediate heptafluoroisobutyryl chloride reacts with a methylating agent in the presence of an alkali metal fluoride to produce perfluoroisobutyl methyl ether.

[0020] The technical circuit of the present invention is as follows:

[0021]

[0022] Where R=Me,Et,Pr,i-Pr,Ph,Bn.

[0023] The specific steps of step 1 are: dissolving chloroformate with a solvent, adding fluoride salt, evacuating, and then introducing hexafluoropropylene. Raising the temperature to the reaction temperature, reacting at the reaction temperature. After the reaction is completed, cooling to room temperature, standing and stratifying. The lower layer of crude product is washed with water and distilled to obtain heptafluoroisobutyrate.

[0024] Preferably, the solvent in step 1 is selected from one or more of acetonitrile, dimethyl sulfoxide, N,N-dimethylformamide, 1,4-dioxane, tetrahydrofuran, toluene, chloroform, ethylene glycol dimethyl ether, diethylene glycol dimethyl ether, and tetraethylene glycol dimethyl ether; more preferably diethylene glycol dimethyl ether.

[0025] Preferably, the fluoride salt in step 1 is selected from one or more of sodium fluoride, lithium fluoride, potassium fluoride, cesium fluoride, silver fluoride, and ammonium fluoride; more preferably, it is potassium fluoride.

[0026] Preferably, the reaction temperature in step 1 is 50°C to 150°C; more preferably 80°C to 120°C.

[0027] Preferably, the molar ratio of hexafluoropropylene to chloroformate in step 1 is 1:1-5; more preferably 1:1-2.

[0028] Preferably, the molar ratio of hexafluoropropylene to fluoride salt in step 1 is 1:1-5; more preferably 1:1-2.

[0029] Preferably, in the step 1, the mass ratio of hexafluoropropylene to the solvent is 1:3-20; more preferably 1:5-10.

[0030] Preferably, the reaction time of step 1 is 2 to 10 hours; more preferably 3 to 5 hours.

[0031] The specific steps of step 2 are as follows: dissolve heptafluoroisobutyrate in a polar solvent, and then add an aqueous solution of alkali. After the addition is completed, react at the reaction temperature. After the reaction is completed, adjust the pH value to 5-6 with 10% dilute hydrochloric acid, then extract with ethyl acetate, combine the organic phases, wash three times with saturated brine, and then dry with anhydrous sodium sulfate. Filter and rotary evaporate to obtain a crude product of heptafluoroisobutyric acid, which is directly used in the next step without purification.

[0032] Preferably, the polar solvent in step 2 is selected from one or more of acetonitrile, acetone, dimethyl sulfoxide, N,N-dimethylformamide, 1,4-dioxane, tetrahydrofuran, methanol, and ethanol; more preferably methanol.

[0033] Preferably, the base in step 2 is selected from one or more of sodium hydroxide, lithium hydroxide, potassium hydroxide, potassium carbonate, sodium carbonate, and cesium carbonate; more preferably sodium hydroxide.

[0034] Preferably, the reaction temperature in step 2 is 0°C to 50°C; more preferably 20°C to 25°C.

[0035] Preferably, the molar ratio of heptafluoroisobutyrate to the base in step 2 is 1:1-8; more preferably 1:2-4.

[0036] Preferably, in step 2, the mass ratio of heptafluoroisobutyrate to solvent is 1:3-20; more preferably 1:5-10.

[0037] Preferably, the reaction time of step 2 is 1 to 3 hours; more preferably 1 to 1.5 hours.

[0038] The specific steps of step 3 are: dissolving heptafluoroisobutyric acid in a solvent, then adding a catalyst, cooling to 0°C, and then slowly dropping an acylating agent. After the addition is completed, react at the reaction temperature. After the reaction is completed, low-temperature distillation is performed to obtain heptafluoroisobutyryl chloride.

[0039] Preferably, the solvent in step three is selected from one or more of acetonitrile, 1,4-dioxane, tetrahydrofuran, diethyl ether, acetone, toluene, dichloromethane, chloroform, and diethylene glycol dimethyl ether; more preferably dichloromethane.

[0040] Preferably, the catalyst in step three is selected from one or more of N,N-dimethylformamide, N-methylpyrrolidone, pyridine, and ferric chloride; more preferably, it is N,N-dimethylformamide.

[0041] Preferably, the acylating agent in step 3 is selected from one or more of oxalyl chloride, thionyl chloride, sulfuryl chloride, phosphorus oxychloride, and phosphorus trichloride; more preferably, thionyl chloride.

[0042] Preferably, the reaction temperature in step three is 0°C to 30°C; more preferably 20°C to 25°C.

[0043] Preferably, in step 3, the molar ratio of heptafluoroisobutyric acid to the acylating agent is 1:1-5; more preferably 1:1.5-3.

[0044] Preferably, in step three, the molar ratio of heptafluoroisobutyric acid to the catalyst is 1:0.01-0.5; more preferably 1:0.01-0.05.

[0045] Preferably, in step three, the mass ratio of heptafluoroisobutyric acid to solvent is 1:3-20; more preferably 1:5-10.

[0046] Preferably, the reaction time of step three is 1 to 5 hours; more preferably 1 to 2 hours.

[0047] The specific steps of step 4 are as follows: dissolving heptafluoroisobutyryl chloride in a solvent, then adding a fluoride salt, a phase transfer catalyst, and a methylating agent, heating to a reaction temperature, and reacting at the reaction temperature. After the reaction is completed, adding an excess of 20% sodium hydroxide solution to quench, standing to separate layers, collecting the lower layer of liquid, washing with water, and distilling to obtain pure perfluoroisobutyl methyl ether.

[0048] Preferably, the solvent in step 4 is selected from one or more of acetonitrile, N,N-dimethylformamide, N,N-dimethylacetamide, 1,4-dioxane, dimethyl sulfoxide, ethylene glycol dimethyl ether, diethylene glycol dimethyl ether, and tetraethylene glycol dimethyl ether; more preferably diethylene glycol dimethyl ether.

[0049] Preferably, the fluoride salt in step 4 is selected from one or more of sodium fluoride, lithium fluoride, potassium fluoride, cesium fluoride, silver fluoride, and ammonium fluoride; more preferably, it is potassium fluoride.

[0050] Preferably, the phase transfer catalyst in step 4 is selected from one or more of tetrabutylammonium bromide, benzyltriethylammonium chloride, methyltrialkylammonium chloride, 15-crown-5, and 18-crown-6; more preferably, methyltrialkylammonium chloride.

[0051] Preferably, the methylating agent in step 4 is selected from one or more of methyl iodide, dimethyl sulfate, and dimethyl carbonate; more preferably, dimethyl sulfate.

[0052] Preferably, the reaction temperature in step 4 is 50°C to 150°C; more preferably 60°C to 90°C.

[0053] Preferably, the molar ratio of heptafluoroisobutyryl chloride to fluoride salt in step 4 is 1:1-6; more preferably 1:2-3.

[0054] Preferably, the molar ratio of heptafluoroisobutyryl chloride to the phase transfer catalyst in step 4 is 1:0.01-1; more preferably 1:0.01-0.5.

[0055] Preferably, in step 4, the molar ratio of heptafluoroisobutyryl chloride to the methylating agent is 1:1-6; more preferably 1:2-3.

[0056] Preferably, in step 4, the mass ratio of heptafluoroisobutyryl chloride to the solvent is 1:3-20; more preferably 1:5-10.

[0057] Preferably, the reaction time of step 4 is 1 to 12 hours; more preferably 2 to 5 hours.

[0058] Compared with the existing technology, the present invention has the following beneficial effects:

[0059] 1. The raw materials hexafluoropropylene and chloroformate used in the present invention are cheap and readily available, which greatly reduces the production cost;

[0060] Compared with other routes, the synthetic route of the present invention can construct the key intermediate heptafluoroisobutyryl chloride more quickly and with high yield;

[0061] 2. The synthesis of the key intermediate heptafluoroisobutyryl chloride constructed by the present invention is carried out through conventional processes such as addition, hydrolysis, acylation, etc. The reaction conditions are mild, the process operation is simple and safe, the reaction conversion rate of each step is high, and the products are easy to separate and purify, which effectively improves the yield and purity of the product and is suitable for industrial production. DETAILED DESCRIPTION

[0062] The above contents of the present invention are further described in detail below in conjunction with specific implementation plans. For technicians in this research field, this should not be understood as the scope of the above subject matter of the present invention being limited to the following examples; all technologies implemented based on the above contents of the present invention belong to the scope of the present invention.

[0063] Unless otherwise specified, the experimental methods used in the following examples are all conventional methods; the reagents, materials, instruments, etc. used in the following examples are all commercially available unless otherwise specified.

[0064] Example 1

[0065] Referring to the technical route diagram in the invention content, the specific steps are as follows:

[0066] 1) Dissolve propyl chloroformate (1838g, 15.0mmol) in 6L acetonitrile, add cesium fluoride (1823g, 12.0mmol), dry the pressure-resistant reactor and evacuate, then introduce hexafluoropropylene (1500g, 10.0mmol). Heat to 100℃ for reaction. After the reaction is completed, cool to room temperature and stand for stratification. The lower layer of crude product is washed with water and distilled to obtain 2433.14g of product perfluorobutyric acid propyl ester, with a yield of 95%. 1H NMR (400MHz, CDCl3) δ4.15 (d, J=10.5Hz, 2H), δ1.70–1.65 (m, 2H), 0.95 (t, J=8.0Hz, 3H).19F NMR (376MHz, CDCl3) δ-75.05, -75.07 (d, J = 9.42Hz, 6F), -181.88–-181.97 (m, 1F).

[0067] 2) Dissolve heptafluoroisobutyric acid propyl ester (2561g, 10.0mmol) in 8L methanol, then add an aqueous solution of sodium hydroxide (1200g, 30.0mmol). After the addition, react at room temperature. After the reaction is completed, adjust the pH value to 5-6 with 10% dilute hydrochloric acid, then extract with ethyl acetate, combine the organic phases, wash three times with saturated brine, and then dry with anhydrous sodium sulfate. Filter and rotary evaporate to obtain 2145g of crude heptafluoroisobutyric acid with a yield of 100%. No purification is required and it is directly used in the next step. 19 F NMR (376MHz, CDCl3) δ-75.47, -75.49 (d, J = 9.48Hz, 6F), -181.38–-181.46 (m, 1F).

[0068] 3) Dissolve heptafluoroisobutyric acid (2140 g, 10.0 mmol) in 5 L of dichloromethane, then add catalyst N,N-dimethylformamide (7.3 g, 0.1 mmol), cool to 0°C, then slowly drop thionyl chloride (1428 g, 12.0 mmol). After addition, react at 0°C. After the reaction, distill at low temperature to obtain 2278.3 g of heptafluoroisobutyryl chloride with a yield of 98%. 19F NMR (376 MHz, CDCl3) δ-75.94, -75.96, -75.98, -75.99 (dt, J = 9.56 Hz, 6.25 Hz, 6F), -168.99–-169.07 (m, 1F).

[0069] 4) Dissolve heptafluoroisobutyryl chloride (2324 g, 10.0 mmol) in 1.2 L diethylene glycol dimethyl ether, then add cesium fluoride (2280 g, 15.0 mmol), methyltrialkylammonium chloride (8.1 g, 0.02 mmol), and dimethyl sulfate (2520 g, 20.0 mmol). After the addition, heat to 90 ° C. After the reaction is completed, add an excess of 20% sodium hydroxide solution to quench, let stand and separate, collect the lower layer of liquid, wash with water, and distill to obtain 2150.52 g of pure perfluoroisobutyl methyl ether with a yield of 86%. 1H NMR (400MHz, CDCl3) δ3.38 (s, 3H). 19F NMR (376MHz, CDCl3) δ -74.43, -74.49 (d, J = 9.55Hz, 6F), -82.44–-82.56 (m, 2F), -182.32–-182.46 (m, 1F).

[0070] Example 2

[0071] 1) Dissolve methyl chloroformate (1128g, 12.0mmol) in 4L tetrahydrofuran, add potassium fluoride (870g, 15.0mmol), dry the pressure reactor and evacuate, then pass hexafluoropropylene (1500g, 10.0mmol). Heat to 50℃ for reaction. After the reaction is completed, cool to room temperature and stand for stratification. The lower layer of crude product is washed with water and distilled to obtain 1687.2g of product perfluorobutyric acid methyl ester, with a yield of 74%. 1HNMR (400MHz, CDCl3) δ4.03 (s, 1H). 19F NMR (376MHz, CDCl3) δ-76.41, -76.43 (d, J=9.41Hz, 6F), -182.18–-182.27 (m, 1F).

[0072] 2) Dissolve methyl heptafluoroisobutyrate (2280 g, 10.0 mmol) in 8 L of ethanol, and then add an aqueous solution of lithium hydroxide (1200 g, 50.0 mmol). After the addition, heat to 30 °C for reaction. After the reaction, adjust the pH to 5-6 with 10% dilute hydrochloric acid, then extract with ethyl acetate, combine the organic phases, wash three times with saturated brine, and then dry with anhydrous sodium sulfate. Filter and rotary evaporate to obtain 2098 g of crude heptafluoroisobutyric acid with a yield of 98%, which can be used directly in the next step without purification.

[0073] 3) Heptafluoroisobutyric acid (2140 g, 10.0 mmol) was dissolved in 10 L toluene, and then catalyst pyridine (395.5 g, 5.0 mmol) was added, the temperature was lowered to 0°C, and then sulfuryl chloride (6750 g, 50.0 mmol) was slowly added dropwise. After the addition, the temperature was raised to 30°C for reaction. After the reaction was completed, low temperature distillation was performed to obtain 2045.82 g of heptafluoroisobutyryl chloride, with a yield of 88%.

[0074] 4) Dissolve heptafluoroisobutyryl chloride (2324 g, 10.0 mmol) in 6 L acetonitrile, then add sodium fluoride (1680 g, 40.0 mmol), tetrabutylammonium bromide (322 g, 1.0 mmol), and methyl iodide (7100 g, 50.0 mmol). After the addition, heat to 50 ° C. After the reaction is completed, add an excess of 20% sodium hydroxide solution to quench, let stand and separate, collect the lower layer of liquid, wash with water, and distill to obtain 1075.26 g of pure perfluoroisobutyl methyl ether with a yield of 43%.

[0075] Example 3

[0076] 1) Dissolve ethyl chloroformate (1404g, 13.0mmol) in 5L ethylene glycol dimethyl ether, add sodium fluoride (672g, 16.0mmol), dry the pressure reactor and evacuate, then pass hexafluoropropylene (1500g, 10.0mmol). Heat to 70℃ for reaction. After the reaction is completed, cool to room temperature and stand for stratification. The lower layer of crude product is washed with water and distilled to obtain 1379.9g of ethyl perfluorobutyrate, with a yield of 57%. 1HNMR (400MHz, CDCl3) δ4.31–4.25 (m, 2H), 1.24 (t, J=6.0Hz, 3H). 19FNMR (376MHz, CDCl3) δ-76.25, -76.27 (d, J=9.37Hz, 6F), -181.88–-181.99 (m, 1F).

[0077] 2) Dissolve ethyl heptafluoroisobutyrate (2421 g, 10.0 mmol) in 10 L tetrahydrofuran, cool to 0°C, and then add an aqueous solution of potassium hydroxide (1120 g, 20.0 mmol). After the addition, react at 0°C. After the reaction, adjust the pH to 5-6 with 10% dilute hydrochloric acid, then extract with ethyl acetate, combine the organic phases, wash three times with saturated brine, and then dry with anhydrous sodium sulfate. Filter and rotary evaporate to obtain 2119 g of crude heptafluoroisobutyric acid with a yield of 99%. No purification is required and it is directly used in the next step.

[0078] 3) Dissolve heptafluoroisobutyric acid (2140 g, 10.0 mmol) in 8 L chloroform, then add catalyst N-methylpyrrolidone (99 g, 1.0 mmol), cool to 0°C, then slowly drop oxalyl chloride (3810 g, 30.0 mmol). After addition, react at room temperature. After the reaction is completed, distill at low temperature to obtain 2231.8 g of heptafluoroisobutyryl chloride, with a yield of 96%.

[0079] 4) Dissolve heptafluoroisobutyryl chloride (2324g, 10.0mmol) in 8LN,N-dimethylformamide, then add lithium fluoride (780g, 30.0mmol), 18-crown ether-6 (528g, 2.0mmol), dimethyl sulfate (3783g, 30.0mmol), and heat to 80°C after addition. After the reaction is completed, add an excess of 20% sodium hydroxide solution to quench, let stand and separate, collect the lower layer of liquid, wash with water, and distill to obtain 1450.35g of pure perfluoroisobutyl methyl ether with a yield of 58%.

[0080] Example 4

[0081] 1) Dissolve phenyl chloroformate (391.4 g, 2.5 mmol) in 2 L of dimethyl sulfoxide, add silver fluoride (177.8 g, 1.4 mmol), dry the pressure-resistant reactor and evacuate it, then introduce hexafluoropropylene (150 g, 1.0 mmol). Heat to 150 ° C for reaction. After the reaction is completed, cool to room temperature and stand for stratification. The lower layer of crude product is washed with water and distilled to obtain 269.83 g of perfluorobutyric acid phenyl ester, with a yield of 93%. 1HNMR(400MHz, CDCl3)δ7.41–7.36(m,2H),7.28–7.24(m,1H),7.18–7.14(m,2H).19F NMR (376MHz, CDCl3) δ -75.31, -75.33 (d, J = 9.39Hz, 6F), -180.05–-180.17 (m, 1F).

[0082] 2) Dissolve phenyl heptafluoroisobutyrate (2901 g, 10.0 mmol) in 10 L 1,4-dioxane, cool to 0°C, and then add an aqueous solution of sodium hydroxide (800 g, 20.0 mmol). After addition, react at room temperature. After the reaction, adjust the pH to 5-6 with 10% dilute hydrochloric acid, then extract with ethyl acetate, combine the organic phases, wash three times with saturated brine, and then dry with anhydrous sodium sulfate. Filter and rotary evaporate to obtain 2119 g of crude heptafluoroisobutyric acid with a yield of 99%. No purification is required and it is directly used in the next step.

[0083] 3) Dissolve heptafluoroisobutyric acid (2140 g, 10.0 mmol) in 12 L tetrahydrofuran, then add catalyst N,N-dimethylformamide (7.3 g, 0.1 mmol), cool to 0°C, then slowly drop phosphorus oxychloride (3833 g, 25.0 mmol). After addition, react at room temperature. After the reaction is completed, distill at low temperature to obtain 1836.6 g of heptafluoroisobutyryl chloride, with a yield of 79%.

[0084] 4) Dissolve heptafluoroisobutyryl chloride (2324 g, 10.0 mmol) in 10 L dimethyl sulfoxide, then add potassium fluoride (1160 g, 20.0 mmol), benzyltriethylammonium chloride (182 g, 0.8 mmol), and dimethyl carbonate (2700 g, 30.0 mmol). After the addition, heat to 150°C. After the reaction is completed, add an excess of 20% sodium hydroxide solution to quench, let stand to separate, collect the lower layer of liquid, wash with water, and distill to obtain 925.22 g of pure perfluoroisobutyl methyl ether with a yield of 37%.

[0085] Example 5

[0086] 1) Dissolve benzyl chloroformate (3070g, 18.0mmol) in 8L diethylene glycol dimethyl ether, add potassium fluoride (1740g, 30.0mmol), dry the pressure-resistant reactor and evacuate it, then introduce hexafluoropropylene (1500g, 10.0mmol). Heat to 130℃ for reaction. After the reaction is completed, cool to room temperature and stand for stratification. The lower layer of crude product is washed with water and distilled to obtain 2585.36g of perfluorobutyric acid benzyl ester, with a yield of 85%. 1HNMR(400MHz, CDCl3)δ7.35(d,J=4.3Hz,4H),7.30–7.26(m,1H),5.15(s,2H).19F NMR (376MHz, CDCl3) δ-75.94, -75.96 (d, J = 9.40Hz, 6F), -181.55–-181.67 (m, 1F).

[0087] 2) Dissolve benzyl heptafluoroisobutyrate (3042g, 10.0mmol) in 10L dimethyl sulfoxide, cool to 0°C, and then add an aqueous solution of potassium carbonate (6900g, 50.0mmol). After the addition, heat to 50°C for reaction. After the reaction, adjust the pH value to 5-6 with 10% dilute hydrochloric acid, then extract with ethyl acetate, combine the organic phases, wash three times with saturated brine, and then dry with anhydrous sodium sulfate. Filter and rotary evaporate to obtain 1048.8g of crude heptafluoroisobutyric acid with a yield of 49%. No purification is required and it is directly used in the next step.

[0088] 3) Dissolve heptafluoroisobutyric acid (2140 g, 10.0 mmol) in 8 L of ether, then add catalyst pyridine (79 g, 1.0 mmol), cool to 0°C, then slowly drop thionyl chloride (3569 g, 30.0 mmol). After the addition, react at room temperature. After the reaction is completed, distill at low temperature to obtain 2162 g of heptafluoroisobutyryl chloride, with a yield of 93%.

[0089] 4) Dissolve heptafluoroisobutyryl chloride (232.4 g, 1.0 mmol) in 1.4 L tetraethylene glycol dimethyl ether, then add silver fluoride (152.2 g, 1.2 mmol), 15-crown ether-5 (110 g, 0.5 mmol), methyl iodide (227.2 g, 1.6 mmol), and heat to 120°C after addition. After the reaction is completed, add an excess of 20% sodium hydroxide solution to quench, let stand to separate, collect the lower layer of liquid, wash with water, and distill to obtain 227.55 g of pure perfluoroisobutyl methyl ether with a yield of 91%.

[0090] Comparative Example 1 (Chinese Patent CN115521192)

[0091] In a 250 ml three-necked flask, add 5 g (16.85 mmol) of triphosgene in toluene solution (10 ml) and add 0.12 g (1.68 mmol) of DMF as a catalyst to catalyze the generation of phosgene.

[0092] In a 120 ml thick-walled pressure bottle, add 5 g (33.33 mmol) of hexafluoropropylene, 3.3 g (33.33 mmol) of phosgene, 1.933 g (33.33 mmol) of metal fluoride KF, and 20 ml of acetonitrile as solvent, and stir at room temperature for 6 hours to obtain 80% of heptafluoroisobutyric acid salt.

[0093] Directly add 4.5 g (33.33 mmol) of sulfuryl chloride, stir at room temperature for 10 h, and distill to obtain 5.5 g (23.7 mmol) of heptafluoroisobutyryl chloride, with a yield of about 89%.

[0094] A 5ml thick-walled pressure-resistant bottle was used as the reaction vessel. In the glove box, metal fluoride KF (12.5mg, 0.216mmol) was added to the thick-walled pressure-resistant bottle, and then taken out. Under the protection of N2, 1ml of acetonitrile was injected as the solvent, and heptafluoroisobutyryl chloride (25mg, 0.108mmol), dimethyl sulfate (25mg, 0.198mmol), and tetrabutylammonium chloride (1.4mg, 0.005mmol) were added. Heat to 70℃ and stir to react for 1h. The system changed from white turbidity to orange-yellow, and the yield was about 80%.

[0095] From the above comparison, it can be seen that the total yield of preparing perfluoroisobutyl methyl ether by heptafluoroisobutyryl chloride provided by the method of comparative example 1 is 56.96%, and the yield of preparing phosgene in the first step is not given; the total yield of preparing perfluoroisobutyl methyl ether by the method provided by embodiment 1 of the present invention is 80.1%, and the total yield is greatly improved. In addition, the raw material used in comparative example 1 is phosgene, which is a highly toxic gas; the raw material used in the present invention is an economical and low-toxic chloroformate derivative. Therefore, the preparation method of perfluoroisobutyl methyl ether of the present invention is safer, has a higher yield, low cost, mild reaction, simple operation, and can meet the needs of industrial production.

[0096] The above description is only a preferred specific implementation manner of the present invention, but the scope of protection of the present invention is not limited thereto. Any modifications, equivalent substitutions and improvements made by any technician familiar with the technical field within the technical scope disclosed by the present invention should be included in the scope of protection of the invention.

Claims

1. A method for synthesizing perfluoroisobutyl methyl ether, characterized in that: The following steps are involved: Step 1: using hexafluoropropylene and chloroformate as raw materials, heptafluoroisobutyrate is prepared by addition reaction under the action of fluoride salt; Step 2: hydrolyzing heptafluoroisobutyrate under the action of a base to obtain heptafluoroisobutyric acid; Step 3: Heptafluoroisobutyric acid is reacted with an acylating agent to prepare the key intermediate heptafluoroisobutyryl chloride; Step 4: The key intermediate heptafluoroisobutyryl chloride reacts with a methylating agent in the presence of an alkali metal fluoride to produce perfluoroisobutyl methyl ether.

2. The method for synthesizing perfluoroisobutyl methyl ether according to claim 1, characterized in that: The specific steps of step 1 are: dissolving chloroformate with a solvent, adding fluoride salt, evacuating, then introducing hexafluoropropylene, heating to the reaction temperature, reacting at the reaction temperature, cooling to room temperature after the reaction is completed, standing to separate layers, and washing the lower layer of crude product with water and distilling to obtain heptafluoroisobutyrate.

3. The method for synthesizing perfluoroisobutyl methyl ether according to claim 2, characterized in that: The solvent in step 1 is selected from one or more of acetonitrile, dimethyl sulfoxide, N,N-dimethylformamide, 1,4-dioxane, tetrahydrofuran, toluene, chloroform, ethylene glycol dimethyl ether, diethylene glycol dimethyl ether, and tetraethylene glycol dimethyl ether; The fluoride salt is selected from one or more of sodium fluoride, lithium fluoride, potassium fluoride, cesium fluoride, silver fluoride, and ammonium fluoride; The reaction temperature is 50°C to 150°C; The molar ratio of hexafluoropropylene to chloroformate is 1:1 to 5; The molar ratio of hexafluoropropylene to fluoride salt is 1:1 to 5; The mass ratio of hexafluoropropylene to solvent is 1:3 to 20; The reaction time is 2 to 10 hours.

4. The method for synthesizing perfluoroisobutyl methyl ether according to claim 1, characterized in that: The specific steps of step 2 are: dissolving heptafluoroisobutyrate in a polar solvent, then adding an aqueous solution of alkali, reacting at the reaction temperature, and after the reaction is completed, adjusting the pH value to 5-6 with 10% dilute hydrochloric acid, then extracting with ethyl acetate, combining the organic phases, washing three times with saturated brine, and then drying with anhydrous sodium sulfate, filtering and rotary evaporation to obtain a crude heptafluoroisobutyric acid product, which is directly used in the next step without purification.

5. The method for synthesizing perfluoroisobutyl methyl ether according to claim 4, characterized in that: The polar solvent in step 2 is selected from one or more of acetonitrile, acetone, dimethyl sulfoxide, N,N-dimethylformamide, 1,4-dioxane, tetrahydrofuran, methanol, and ethanol; The base is selected from one or more of sodium hydroxide, lithium hydroxide, potassium hydroxide, potassium carbonate, sodium carbonate, and cesium carbonate; The reaction temperature is 0°C to 50°C; The molar ratio of heptafluoroisobutyrate to base is 1:1 to 8; The mass ratio of heptafluoroisobutyrate to the polar solvent is 1:3-20; The reaction time is 1 to 3 hours.

6. The method for synthesizing perfluoroisobutyl methyl ether according to claim 1, characterized in that: The specific steps of step three are: dissolving heptafluoroisobutyric acid in a solvent, then adding a catalyst, cooling to 0°C, then slowly dropping an acylating agent, reacting at the reaction temperature, and after the reaction is completed, low-temperature distillation to obtain heptafluoroisobutyryl chloride.

7. The method for synthesizing perfluoroisobutyl methyl ether according to claim 6, characterized in that: The solvent in step 3 is selected from one or more of acetonitrile, 1,4-dioxane, tetrahydrofuran, diethyl ether, acetone, toluene, dichloromethane, chloroform, and diethylene glycol dimethyl ether; The catalyst is selected from one or more of N,N-dimethylformamide, N-methylpyrrolidone, pyridine, and ferric chloride; The acylating agent is selected from one or more of oxalyl chloride, thionyl chloride, sulfuryl chloride, phosphorus oxychloride, and phosphorus trichloride; The reaction temperature is 0°C to 30°C; The molar ratio of heptafluoroisobutyric acid to the acylating agent is 1:1 to 5; The molar ratio of heptafluoroisobutyric acid to the catalyst is 1:0.01-0.5; The mass ratio of heptafluoroisobutyric acid to the solvent is 1:3-20; The reaction time is 1 to 5 hours.

8. The method for synthesizing perfluoroisobutyl methyl ether according to claim 1, characterized in that: The specific steps of step 4 are: dissolving heptafluoroisobutyryl chloride in a solvent, then adding a fluoride salt, a phase transfer catalyst, and a methylating agent, and after the addition, heating to the reaction temperature, reacting at the reaction temperature, after the reaction is completed, adding an excess of 20% sodium hydroxide solution for quenching, standing and stratifying, collecting the lower layer of liquid, washing with water, and distilling to obtain pure perfluoroisobutyl methyl ether.

9. The method for synthesizing perfluoroisobutyl methyl ether according to claim 8, characterized in that: The solvent in step 4 is selected from one or more of acetonitrile, N,N-dimethylformamide, N,N-dimethylacetamide, 1,4-dioxane, dimethyl sulfoxide, ethylene glycol dimethyl ether, diethylene glycol dimethyl ether, and tetraethylene glycol dimethyl ether; The fluoride salt is selected from one or more of sodium fluoride, lithium fluoride, potassium fluoride, cesium fluoride, silver fluoride, and ammonium fluoride; The phase transfer catalyst is selected from one or more of tetrabutylammonium bromide, benzyltriethylammonium chloride, methyltrialkylammonium chloride, 15-crown-5, and 18-crown-6; The methylating agent is selected from one or more of methyl iodide, dimethyl sulfate, and dimethyl carbonate; The reaction temperature is 50°C to 150°C; The molar ratio of heptafluoroisobutyryl chloride to fluoride salt is 1:1 to 6; The molar ratio of heptafluoroisobutyryl chloride to the phase transfer catalyst is 1:0.01-1; The molar ratio of heptafluoroisobutyryl chloride to the methylating agent is 1:1 to 6; The mass ratio of heptafluoroisobutyryl chloride to the solvent is 1:3-20; The reaction time is 1 to 12 hours.

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