Preparation method of symmetrical fluoroether products

Abstract

The invention discloses a preparation method of a symmetrical fluoroether product. In a dichloromethane system, a fluoroalcohol and p-methylsulfonyl chloride react in an alkaline environment at room temperature to obtain a p-methylsulfonate intermediate. Subsequently, an inorganic strong base is dropwise added to the p-methylsulfonate intermediate, the fluoroalcohol and p-methylbenzenesulfonyl chloride in the dichloromethane system under low temperature conditions. The temperature is then increased and the reaction temperature is maintained at 30°C to 50°C to continue the reaction. After the reaction is completed, the symmetrical fluoroether product is obtained by distillation. The invention does not use the Williamson synthesis method, greatly improves the yield of the second step, and ensures that the total reaction yield can reach a maximum of 94.6%. The reaction process can be carried out in the same system, does not require extraction and purification of the intermediate product, simplifies the process, and reduces production costs.

Description

Technical Field

[0001] The invention relates to the technical field of battery electrolyte additives, and in particular to a method for preparing a symmetrical fluoroether product. Background Art

[0002] Fluorinated organic solvents have long been used in the production of lithium-ion batteries. Compared to conventional electrolytes containing non-fluorinated solvents, fluorinated organic solvents are more effective in improving the performance of lithium-ion batteries. This is because fluorine has strong electronegativity and weak polarity, and fluorinated additives have advantages such as low melting point, high flash point, and high oxidative decomposition voltage. For example, fluoropropanol ether (structure shown in Formula 1) can be used as a low-temperature electrolyte additive, not only improving the low-temperature performance of the electrolyte, but also enhancing the battery's oxidation resistance, flame retardancy, and electrode wettability. Furthermore, bis-(2,2-difluoroethyl) ether (structure shown in Formula 2) used as a battery electrolyte can also have higher compatibility with graphite anodes.

[0003] Formula 1:

[0004] Formula 2:

[0005] The Williamson synthesis is commonly used to synthesize ethers, involving the reaction of sodium alkoxide with an alkyl halide, sulfonate, and sulfate under anhydrous conditions to produce an ether. The Williamson synthesis can be used to prepare symmetrical ethers, such as those shown in Formulas 1 and 2, as well as asymmetrical ethers. For example, Chinese invention patent application No. 201711259446.6, "A Two-Step Method for Preparing Hydrofluoroethers," discloses a two-step method for preparing hydrofluoroethers. The first step involves reacting p-toluenesulfonyl chloride with a fluorinated alcohol under alkaline conditions to produce p-toluenesulfonate. The second step involves reacting p-toluenesulfonate with sodium alkoxide via the Williamson ether synthesis reaction to produce the hydrofluoroether. While the document discloses a yield exceeding 94% for the first step, the yield for the second step is only above 84%. This limited yield in the second step results in a low overall yield. Furthermore, sodium alkoxide is both a nucleophile and an alkaline reagent. Alkyl halides are very susceptible to elimination reactions under the conditions of the Williamson ether synthesis to produce alkenes rather than ethers. Therefore, the Williamson ether synthesis is more suitable for primary alkyl halides and not for polyalkyl halides. Therefore, it is very difficult to prepare high-yield symmetrical alcohol ether products such as those shown in Formulas 1 and 2 through the Williamson ether synthesis reaction. Summary of the Invention

[0006] The object of the present invention is to provide a method for preparing a symmetrical fluorinated ether product, which can be used to prepare a series of symmetrical fluorinated symmetrical ether products to improve the yield of the product and reduce the production cost.

[0007] To achieve the above object, the present invention provides the following technical solutions:

[0008] A method for preparing a symmetrical fluoroether product comprises reacting a fluoroalcohol and p-methylsulfonyl chloride in a dichloromethane system in an alkaline environment at room temperature to obtain a p-methylsulfonate intermediate. The key lies in: adding the p-methylsulfonate intermediate, the fluoroalcohol and p-methylbenzenesulfonyl chloride again in the dichloromethane system, dropwise adding an inorganic strong base under low temperature conditions, raising the temperature after the dropwise addition is completed, maintaining the reaction temperature at 30°C to 50°C, and continuing the reaction for 2h to 8h. After the reaction is completed, the symmetrical fluoroether product is obtained by distillation.

[0009] Specifically, the above low temperature condition is 15°C to 20°C.

[0010] Preferably, the above-mentioned inorganic strong base is a potassium hydroxide or sodium hydroxide solution with a mass concentration of 40% to 50%, and the volume ratio of the inorganic strong base solution to the dichloromethane is 1:4 to 8.

[0011] Furthermore, the above-mentioned dichloromethane system also includes N-methylpyrrolidone.

[0012] Furthermore, the volume ratio of the above-mentioned N-methylpyrrolidone and dichloromethane is 1:10-20.

[0013] More specifically, the molar ratio of the fluoroalcohol to p-methylsulfonyl chloride is 1:1.2-1.8, and the molar ratio of the fluoroalcohol to p-methylsulfonate intermediate is 1:1.2-1.8.

[0014] It should be noted that the alkaline environment is prepared by adding triethylamine, pyridine, potassium hydroxide or sodium hydroxide solution into the reaction system, the concentration of the alkaline solution is 5% to 10%, and the volume ratio of the alkaline solution to the dichloromethane is 1:4 to 8.

[0015] Optimally, the volume ratio of the p-toluenesulfonyl chloride to dichloromethane is 1:3-6.

[0016] Compared with the prior art, the present invention has the following beneficial effects:

[0017] The present invention involves reacting a fluoroalcohol with p-methylsulfonyl chloride in an alkaline dichloromethane system to obtain a p-methylsulfonate intermediate. This p-methylsulfonate intermediate then undergoes a secondary reaction with the fluoroalcohol. By controlling the reaction temperature, the corresponding symmetrical fluoroether product can be prepared. This method avoids the Williamson synthesis, significantly improving the yield of the second step and enabling the overall reaction to reach a maximum of 94.6%.

[0018] Although the present invention employs a two-step reaction, the reaction process can be carried out in a single system, eliminating the need for intermediate product extraction and purification. This simplifies the process, reduces production costs, and further improves the yield of the final product. The yields in each embodiment can reach over 89.2%, with a maximum of 94.6%, and the purity of the target product can reach over 99.81%, with a maximum of 99.93%. The first-step reaction yields for Samples 1 and 2 were 96.3% and 96.2%, respectively.

[0019] The mixed system of dichloromethane and N-methylpyrrolidone constructed by the present invention is more conducive to the preparation of symmetrical fluoroether products, especially for long-chain and multi-fluorinated products, and the effect is more significant. The reaction process of the present invention has few side reactions, and high-purity products can be obtained by distillation. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 This is the NMR spectrum of sample 2 prepared in Example 2 of the present invention;

[0021] Figure 2 This is the gas chromatography-mass spectrometry of sample 2 prepared in Example 2 of the present invention;

[0022] Figure 3 This is the NMR spectrum of sample 4 prepared in Example 4 of the present invention;

[0023] Figure 4 This is the gas chromatography-mass spectrometry of sample 4 prepared in Example 4 of the present invention;

[0024] Figure 5 This is a gas chromatogram of sample 2 prepared in Example 2 of the present invention;

[0025] Figure 6 This is a gas chromatogram of sample 4 prepared in Example 4 of the present invention. DETAILED DESCRIPTION

[0026] The following will be combined with the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the embodiments described 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 making creative efforts are within the scope of protection of the present invention.

[0027] For the convenience of description, the amounts of test materials used in the embodiments and comparative examples are all pure amounts.

[0028] Example 1

[0029] S1: Add 7.8 g of fluoroalcohol and 30.5 g of p-methylsulfonyl chloride to a reaction flask containing 94 mL of dichloromethane and stir until fully dissolved. Add 16 mL of 10% pyridine solution dropwise under an ice-water bath. After the addition is complete, react at room temperature for 4 h. After the reaction is complete, filter, adjust the acidity, separate the liquids, and dry to obtain a p-methylsulfonate intermediate.

[0030] S2: The p-methylsulfonate intermediate prepared in step S1 was added again to a reaction flask containing 94 mL of dichloromethane, and 7.8 g of fluoroalcohol was added. 12 mL of 45% sodium hydroxide solution was added dropwise at 20°C. After the addition was complete, the temperature was raised to 40°C and maintained, and the reaction was continued for 4 hours. After the reaction was completed, a symmetrical fluoroether sample 1, i.e., a fluoropropyl ether product, was obtained by distillation.

[0031] Example 2

[0032] S1: Add 7.8 g of fluoroalcohol and 22.9 g of p-methylsulfonyl chloride to a reaction flask containing 70 mL of dichloromethane and stir until fully dissolved. Add 9 mL of 5% triethylamine solution dropwise under an ice-water bath. After the addition is complete, react at room temperature for 4 h. After the reaction is complete, filter, adjust the acidity, separate the liquids, and dry to obtain a p-methylsulfonate intermediate.

[0033] S2: The p-methylsulfonate intermediate prepared in step S1 was added again to a reaction flask containing 70 mL of dichloromethane, and 7.8 g of fluoroalcohol and 5 mL of N-methylpyrrolidone were added. 12 mL of 40% sodium hydroxide solution was added dropwise at 20°C. After the addition was complete, the temperature was raised to 30°C and maintained, and the reaction was continued for 3 hours. After the reaction was completed, a symmetrical fluoroether sample 2, i.e., a fluoropropyl ether product, was obtained by distillation.

[0034] Example 3

[0035] S1: Add 8.2 g of 2,2-difluoroethanol and 26.7 g of p-methylsulfonyl chloride to a reaction flask containing 61 mL of dichloromethane and stir until fully dissolved. Add 15 mL of 10% potassium hydroxide solution dropwise under an ice-water bath. After the addition is complete, react at room temperature for 6 h to obtain a reaction solution containing a p-methylsulfonate intermediate.

[0036] S2: 8.2 g of 2,2-difluoroethanol was added to the reaction solution containing the p-methylsulfonate intermediate prepared in step S1, and 15 mL of a 50% sodium hydroxide solution was added dropwise at 15°C. After the addition was completed, the temperature was raised to 50°C and maintained, and the reaction was continued for 8 hours. After the reaction was completed, the symmetrical fluoroether sample 3, i.e., the di-(2,2-difluoroethyl) ether product, was obtained by distillation.

[0037] Example 4

[0038] S1: Same as step S1 in Example 3;

[0039] S2: 8.2 g of 2,2-difluoroethanol and 3 mL of N-methylpyrrolidone were added to the reaction solution containing the p-methylsulfonate intermediate prepared in step S1, and 12 mL of 50% potassium hydroxide solution was added dropwise at 18°C. After the addition was completed, the temperature was raised to 35°C and maintained, and the reaction was continued for 5 hours. After the reaction was completed, the symmetrical fluoroether sample 4, i.e., di-(2,2-difluoroethyl) ether product, was obtained by distillation.

[0040] Example 5

[0041] S1: Add 8.2 g of 2,2-difluoroethanol, 26.7 g of p-methylsulfonyl chloride, and 6 mL of N-methylpyrrolidone to a reaction flask containing 61 mL of dichloromethane, stir until fully dissolved, and add 10 mL of 5% potassium hydroxide solution dropwise under an ice-water bath. After the addition is complete, react at room temperature for 2 h. After the reaction is completed, a reaction solution containing p-methylsulfonate intermediates is obtained;

[0042] S2: 8.2 g of 2,2-difluoroethanol was added to the reaction solution containing the p-methylsulfonate intermediate prepared in step S1, and 12 mL of a 50% potassium hydroxide solution was added dropwise at 18°C. After the addition was completed, the temperature was raised to 40°C and maintained, and the reaction was continued for 2 hours. After the reaction was completed, the symmetrical fluoroether sample 5, i.e., the di-(2,2-difluoroethyl) ether product, was obtained by distillation.

[0043] Comparative Example

[0044] Comparative Example 1

[0045] S1: The implementation process is the same as step S1 in Example 1;

[0046] S2: The implementation process is the same as step S2 of Example 1, except that the temperature is not increased after the strong base is added, and the reaction is continued at room temperature for 4 hours. After the reaction is completed, the symmetrical fluoroether reference substance 1, i.e., the fluoropropanol ether product, is obtained by distillation.

[0047] Comparative Example 2

[0048] S1: The implementation process is the same as step S1 in Example 3;

[0049] S2: The implementation process is the same as step S2 of Example 3, except that after adding the strong base, the temperature is raised to 30°C and maintained, and the reaction is continued for 3 hours. The symmetrical fluoroether reference substance 2 is obtained by distillation.

[0050] Comparative Example 3

[0051] S1: The implementation process is the same as step S1 of Example 5, except that a chloroform system is used instead of a dichloromethane system;

[0052] S2: The implementation process is the same as step S2 of Example 5. In step S2, a symmetrical fluoroether reference substance 3 is prepared.

[0053] Comparative Example 4

[0054] S1: The implementation process is the same as step S1 of Example 5, except that 10 mL of dimethylacetamide is added to the dichloromethane system instead of N-methylpyrrolidone;

[0055] S2: The implementation process is the same as step S2 of Example 5. In step S2, a symmetrical fluoroether reference substance 4 is prepared.

[0056] Analysis and testing

[0057] The samples of the embodiment were analyzed by high performance gas chromatography-mass spectrometry and nuclear magnetic hydrogen spectrum. The structure of the samples was consistent with the structural characteristics of the target product. The relevant partial spectra are shown in the attached Figures 1 to 4 .

[0058] The samples of the embodiment and the reference substance were respectively tested by high-efficiency gas chromatography, and the purity and total impurity amount of the samples were measured. The results are shown in Table 1.

[0059] The gas chromatograms of sample 2 and sample 5 are shown in the attached Figure 5 and attached Figure 6 .

[0060] The yields in the examples and comparative examples were calculated according to Formula 1. The results are shown in Table 1.

[0061] Formula 1: Yield (%) = actual weight of the sample obtained (g) / theoretical amount calculated based on the amount of fluoroalcohol used (g) × 100%.

[0062] Table 1: Summary of total yield, purity and impurity test results of samples and reference substances

[0063] Sample No. Total yield (%) Purity of target product (%) Total impurities (%) Sample 1 91.5 99.81 0.16 Sample 2 93.6 99.89 0.09 Sample 3 89.2 99.85 0.12 Sample 4 91.3 99.91 0.08 Sample 5 94.6 99.93 0.06 Comparative Example 1 52.3 90.2 9.6 Comparative Example 2 26.7 85.3 14.7 Comparative Example 3 43.6 86.9 12.3 Comparative Example 4 85.1 94.6 5.2

[0064] As can be seen from the results in Table 1, the yields of the various embodiments of the present invention can reach over 89.2%, with a maximum of 94.6%, and the purity of the target product can reach over 99.81%, with a maximum of 99.93%. The first step reaction yields of Sample 1 and Sample 2 were 96.3% and 96.2%, respectively.

[0065] Comparative Examples 1 and 2 reduced the temperature of the second step reaction and prolonged the reaction time. Comparative Example 3 replaced the reaction system and found that the yield of the target product was significantly reduced. It can be seen that the reaction temperature and the reaction system are the key process control points of the present invention and have an important influence on the reaction.

[0066] In Comparative Example 4, dimethylacetamide was used instead of N-methylpyrrolidone. Not only was the yield slightly lower than that of Example 3 in which N-methylpyrrolidone was not added, but the product purity was also correspondingly reduced. This indicates that the mixed system of dichloromethane and N-methylpyrrolidone constructed in the present invention is more conducive to the preparation of symmetrical fluoroether products, especially for long-chain, multi-fluorinated products. The effect is more significant.

Claims

1. A method for preparing symmetrical fluoroether products, wherein a fluoroalcohol and p-methylsulfonyl chloride react in a dichloromethane system under alkaline conditions at room temperature to obtain a p-methylsulfonate intermediate, characterized in that: The p-toluenesulfonate intermediate, the fluoroalcohol and p-toluenesulfonyl chloride are again added dropwise to an inorganic strong base in a dichloromethane system at a low temperature of 15°C to 20°C. After the addition is complete, the temperature is raised and the reaction temperature is maintained at 30°C to 50°C for 2h to 8h. After the reaction is completed, a symmetrical fluoroether product is obtained by distillation. The dichloromethane system also includes N-methylpyrrolidone; The volume ratio of the N-methylpyrrolidone to dichloromethane is 1:10-20.

2. The method for preparing a symmetrical fluoroether product according to claim 1, characterized in that: The inorganic strong base is a potassium hydroxide or sodium hydroxide solution with a mass concentration of 40% to 50%, and the volume ratio of the inorganic strong base solution to the dichloromethane is 1:4 to 8.

3. The method for preparing a symmetrical fluoroether product according to claim 1, characterized in that: The molar ratio of the fluoroalcohol to p-methylsulfonyl chloride is 1:1.2-1.8, and the molar ratio of the fluoroalcohol to p-methylsulfonate intermediate is 1:1.2-1.

8.

4. The method for preparing a symmetrical fluoroether product according to claim 1, characterized in that: The alkaline environment is prepared by adding triethylamine, pyridine, potassium hydroxide or sodium hydroxide solution into the reaction system, the concentration of the alkaline solution is 5% to 10%, and the volume ratio of the alkaline solution to the dichloromethane is 1:4 to 8.

5. The method for preparing a symmetrical fluoroether product according to claim 1, characterized in that: The volume ratio of p-toluenesulfonyl chloride to dichloromethane is 1:3-6.

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