A method for synthesizing difluorophosphate compounds
By generating difluorophosphate intermediates through low-temperature reactions and then carrying out nucleophilic reactions, the problems of low yield and poor purity in traditional methods are solved, achieving high-yield and safe compound synthesis. This method is applicable to the synthesis of difluorophosphate compounds with various functional groups and is suitable for industrial production.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- HEFEI GUOXUAN HIGH TECH POWER ENERGY
- Filing Date
- 2026-02-02
- Publication Date
- 2026-06-09
AI Technical Summary
Traditional methods for synthesizing difluorophosphate compounds result in low yields, poor purity, complex operations, and safety risks, making them unsuitable for industrial production.
The intermediate was generated by reacting pyrophosphoryl chloride with a fluorinating agent at low temperature, and then reacted with a nucleophilic reagent in the presence of an acid-binding agent to synthesize difluorophosphate compounds. Byproducts were removed by controlling the reaction conditions and through a simple purification step.
The synthesis of difluorophosphate compounds with high selectivity and high yield (over 85%) was achieved. The reaction conditions were mild and the safety was high. The method is applicable to the synthesis of compounds with various functional groups and is conducive to industrial production.
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Figure CN122167475A_ABST
Abstract
Description
Technical Field
[0001] This invention relates to the field of lithium-ion battery electrolyte additives, and in particular to a method for synthesizing difluorophosphate compounds. Background Technology
[0002] As lithium-ion batteries develop towards higher energy density and longer cycle life, traditional carbonate electrolytes are increasingly important in high-voltage applications (>4.5V vs. Li). + Under conditions of / Li, oxidative decomposition easily occurs, leading to battery performance degradation. Difluorophosphate compounds, due to the unique synergistic effect of PF and P=O bonds, can form a stable SEI film inside the battery, exhibiting significant advantages under certain high-voltage systems. Traditional methods for synthesizing difluorophosphate compounds generally involve using phosphorus oxychloride and a corresponding alcohol under alkaline conditions to generate the corresponding difluorophosphate intermediate, which is then fluorinated to produce the corresponding difluorophosphate compound. While this method yields the product, the yield of the synthetic intermediate is low, and the specific fluorination conditions limit its widespread application. For example, some methods use highly toxic and difficult-to-prepare fluorinating agents such as phosgene and HgF, posing a serious threat to operator safety and greatly limiting the feasibility of large-scale production. Furthermore, this method often suffers from low yield and poor product purity. For instance, the preparation of ethyl difluorophosphate, obtained by fluorinating ethyl difluorophosphate with sodium fluoride, has a yield of only 40%; when methyl difluorophosphate is prepared by fluorinating antimony trifluoride, monofluorination byproducts often remain, affecting product purity. Furthermore, some reactions have extremely demanding operating conditions and complex procedures, making them unsuitable for industrial production. Therefore, it is necessary to provide a synthetic method for difluorophosphate compounds that offers high yield, convenient separation and purification, and is simple and safe. Summary of the Invention
[0003] Based on the technical problems existing in the background technology, the present invention proposes a method for synthesizing difluorophosphate compounds, which has high product yield, few by-products, convenient separation and purification, mild reaction conditions, simple operation process, high safety, and is conducive to industrial production.
[0004] The present invention provides a method for synthesizing difluorophosphate compounds, comprising the following steps:
[0005] S1. Under a protective atmosphere, pyrophosphoryl chloride is reacted with a fluorinating agent in the first solvent to obtain the intermediate shown in Formula A:
[0006]
[0007] Formula A;
[0008] The reaction temperature is -50℃ to -30℃;
[0009] S2. Under a protective atmosphere, the intermediate shown in Formula A is reacted with the nucleophile R-XH in a second solvent in the presence of an acid-binding agent to obtain the difluorophosphate compound shown in Formula I:
[0010]
[0011] Formula I;
[0012] In Formula I, R-XH, X is selected from oxygen atom or sulfur atom, and R is selected from any one of substituted or unsubstituted straight-chain or branched C1~C5 alkyl, substituted or unsubstituted C6~C10 aryl; the substituted substituent is selected from at least one of F, -CF3, -CN, -NO2, -CF2CF3, -C(CF3)3;
[0013] The reaction temperature is -5℃ to 0℃.
[0014] The synthetic route of the present invention may be, for example:
[0015] .
[0016] The method of this invention involves reacting pyrophosphoryl chloride with a fluorinating agent at low temperature to obtain the general intermediate pyrophosphoryltetrafluoro, which then undergoes a nucleophilic reaction with an alcohol or thiol to yield the corresponding difluorophosphate ester compound. This invention achieves highly selective and high-yield synthesis of difluorophosphate ester compounds, with target product yields exceeding 85%. The reaction conditions are mild, with few byproducts. The main byproduct, triethylamine difluorophosphate, can be easily removed through purification, ensuring high safety. This method exhibits good compatibility with various functional groups and is applicable to the synthesis of difluorophosphate ester compounds with different structures.
[0017] Preferably, in step S1, the first solvent is selected from any one of acetonitrile, tetrahydrofuran, dichloromethane, and toluene; the ratio of pyrophosphoryl chloride to the first solvent is 1g: 2~5mL. In step S1, by selecting an appropriate type and amount of the first solvent, the reaction can be promoted to proceed more uniformly and efficiently.
[0018] Preferably, in S1, the fluorinating agent is selected from at least one of potassium fluoride, sodium fluoride, silver fluoride, zinc fluoride, ammonium fluoride, pyridine hydrofluoric acid (CAS: 32001-55-1), and triethylamine hydrofluoric acid (CAS: 73602-61-6); the molar ratio of pyrophosphoryl chloride to the fluorinating agent is 1:4.2 to 1:4.5. By selecting a suitable type and amount of fluorinating agent, pyrophosphoryl chloride can be converted into the intermediate shown in Formula A more fully and efficiently.
[0019] Preferably, in step S1, after the reaction is complete, a conventional purification step is also included, such as filtering the obtained reaction solution with diatomaceous earth and purifying the filtrate by distillation.
[0020] Preferably, in S1, the distillation purification can be carried out under normal pressure or reduced pressure, wherein the reduced pressure distillation temperature is preferably 20~120℃.
[0021] Preferably, in step S2, the second solvent is selected from any one of acetonitrile, tetrahydrofuran, dichloromethane, and toluene; the ratio of the intermediate shown in Formula A to the second solvent is 1 g: 3~5 mL. In step S2, by selecting an appropriate type and amount of the second solvent, the reaction can be promoted to proceed more uniformly and efficiently.
[0022] Preferably, in S2, the molar ratio of the intermediate shown in Formula A to the nucleophile R-XH is 1:1.2 to 1:1.5. By controlling the appropriate amount of nucleophile R-XH, the reaction efficiency can be improved while saving costs.
[0023] Preferably, in S2, the nucleophile R-XH is selected from any one of CH3OH, CH3CH2OH, CF3CH2OH, CH3SH, and (CH3)2CHCH2SH.
[0024] In S2, the type and amount of the acid-binding agent are conventionally selected and can be adjusted according to actual needs. Preferably, in S2, the acid-binding agent is selected from at least one of triethylamine, N,N-diisopropylethylamine, diethylamine, ethylamine, tert-butylamine, and N-tert-butylethylamine; the molar ratio of the intermediate shown in Formula A to the acid-binding agent is 1:2~3.
[0025] Preferably, in step S2, after the reaction is complete, a conventional purification step is also included, such as: adding ethyl acetate and water to the reaction solution for extraction, drying the obtained organic phase with a desiccant, filtering to remove the desiccant, removing the solvent from the filtrate by rotary evaporation, and then purifying by distillation to obtain the final product.
[0026] Preferably, the volume ratio of ethyl acetate to water is 1~1.5:1.
[0027] Preferably, the extraction is performed two or more times.
[0028] Preferably, the drying agent used for drying the organic phase is anhydrous sodium sulfate or anhydrous magnesium sulfate.
[0029] Preferably, in S1, the specific steps for reacting pyrophosphoryl chloride with the fluorinating agent in the first solvent are conventional operations, which may include: dissolving the fluorinating agent in the first solvent at room temperature, then cooling it to -50°C to -30°C, and slowly adding pyrophosphoryl chloride dropwise under stirring to carry out the reaction.
[0030] In S2, the specific steps of reacting the intermediate shown in Formula A with the nucleophile R-XH in a second solvent in the presence of an acid-binding agent are conventional operations. For example, it may include: dissolving the intermediate shown in Formula A in a second solvent at room temperature, cooling to -5℃ to 0℃, then adding the nucleophile R-XH and the acid-binding agent, and stirring the reaction.
[0031] Preferably, in S1, the reaction time is 2-4 hours.
[0032] Preferably, in S2, the reaction time is 4 to 8 hours.
[0033] By controlling the reaction time in S1 and S2, the reaction can be completed efficiently and fully, thereby saving costs while ensuring the yield.
[0034] In S1 and S2, the protective gas is selected from at least one of nitrogen, helium, and argon.
[0035] The beneficial effects of this invention are as follows:
[0036] The method of this invention involves reacting pyrophosphoryl chloride with a fluorinating reagent at low temperature to obtain the general intermediate pyrophosphoryltetrafluoro, which then undergoes a nucleophilic reaction with an alcohol or thiol to yield the corresponding difluorophosphate compounds. This achieves highly selective and high-yield synthesis of difluorophosphate compounds, with the target product yield reaching over 85%. The reaction conditions are mild, with few byproducts. The main byproduct, triethylamine difluorophosphate, can be easily removed through purification, ensuring high safety. This method exhibits good compatibility with various functional groups and is applicable to the synthesis of difluorophosphate compounds with different structures. Furthermore, the reaction raw materials used in this invention are inexpensive and readily available, reducing reagent costs. The separation and purification of the products can be achieved through simple conventional methods such as filtration and distillation, further enhancing its practical value and facilitating industrial production. Attached Figure Description
[0037] Figure 1 The image shows the 1H NMR spectrum of the difluorophosphate compound 2 prepared in Example 2 of this invention.
[0038] Figure 2 The image shows the 1H NMR spectrum of the difluorophosphate compound 3 prepared in Example 3 of this invention. Detailed Implementation
[0039] The technical solution of the present invention will now be described in detail through specific embodiments.
[0040] Example 1
[0041] Preparation of difluorophosphate compounds 1:
[0042] S1. Under a nitrogen atmosphere, potassium fluoride (0.33 mol) was dissolved in 50 mL of anhydrous acetonitrile at room temperature. The mixture was then cooled to -30°C, and pyrophosphoryl chloride (0.079 mol) was slowly added dropwise with stirring for 2 h. The reaction was monitored by GC-MS until the endpoint was reached. After the reaction was completed, the reaction solution was filtered through diatomaceous earth at room temperature. The filtrate was then distilled at atmospheric pressure at 69°C to obtain 12.6 g of colorless liquid, which is the intermediate shown in Formula A (purity 93%, yield 85.3%).
[0043]
[0044] Formula A;
[0045] S2. Under a nitrogen atmosphere, the intermediate (0.07 mol) shown in Formula A was dissolved in 40 mL of anhydrous dichloromethane at room temperature. The mixture was cooled to 0 °C, and then methanol (0.11 mol) and triethylamine (0.14 mol) were added. The mixture was stirred for 4 h. After the reaction was completed, 50 mL of ethyl acetate and 50 mL of water were added to the reaction solution for extraction. The extraction was repeated twice. The organic phases were combined, dried with anhydrous sodium sulfate, and filtered to remove the anhydrous sodium sulfate. The filtrate was first purified by rotary evaporation to remove the solvent, and then purified by distillation at atmospheric pressure. The fraction from 66 °C to 68 °C was collected to obtain 6.8 g of colorless liquid, which is difluorophosphate compound 1 (yield 83.8%, GC purity 98.3%).
[0046] Structure and characterization of difluorophosphate compound 1:
[0047]
[0048] 1 H NMR (400 MHz, CDCl3) δ 3.70 (d, J = 8.0 Hz, 3H);
[0049] 13 C NMR (125 MHz, ) δ 47.9;
[0050] The boiling point (bp) is 68 ℃ / 760 mm Hg.
[0051] Example 2
[0052] Preparation of difluorophosphate compounds 2:
[0053] S1. Prepare the intermediate shown in Formula A, following the same steps as in Example 1;
[0054] S2. Under a nitrogen atmosphere, the intermediate (0.07 mol) shown in Formula A was dissolved in 40 mL of anhydrous tetrahydrofuran at room temperature. The mixture was cooled to 0 °C, and then CH3CH2OH (0.11 mol) and triethylamine (0.14 mol) were added. The mixture was stirred for 4 h. After the reaction was completed, 50 mL of ethyl acetate and 50 mL of water were added to the reaction solution for extraction. The extraction was repeated twice. The organic phases were combined, dried with anhydrous sodium sulfate, and filtered to remove the anhydrous sodium sulfate. The filtrate was first purified by rotary evaporation to remove the solvent, and then purified by distillation at atmospheric pressure. The fraction collected at 74 °C to 76 °C was used to obtain 7.9 g of colorless liquid, which was difluorophosphate compound 2 (yield 86.9%, GC purity 96.3%).
[0055] Structure and characterization of difluorophosphate compound 2:
[0056]
[0057] 1H NMR (400 MHz, CDCl3) δ 4.05 (s, 2H), 1.36 (s, 3H);
[0058] The boiling point (bp) is 75 ℃ / 760 mm Hg.
[0059] Example 3
[0060] Preparation of difluorophosphate compounds 3:
[0061] S1. Prepare the intermediate shown in Formula A, following the same steps as in Example 1;
[0062] S2. Under a nitrogen atmosphere, the intermediate (0.07 mol) shown in Formula A was dissolved in 40 mL of anhydrous tetrahydrofuran at room temperature. The mixture was cooled to 0 °C, and then CF3CH2OH (0.11 mol) and triethylamine (0.14 mol) were added. The mixture was stirred for 4 h. After the reaction was completed, 50 mL of ethyl acetate and 50 mL of water were added to the reaction solution for extraction. The extraction was repeated twice. The organic phases were combined, dried with anhydrous sodium sulfate, and filtered to remove the anhydrous sodium sulfate. The filtrate was first purified by rotary evaporation to remove the solvent, and then purified by distillation at atmospheric pressure. The fraction from 68 °C to 71 °C was collected to obtain 11.4 g of colorless liquid, which is difluorophosphate compound 3 (yield 88.6%, GC purity 95.38%).
[0063] Structure and characterization of difluorophosphate compound 3:
[0064]
[0065] 1H NMR (400 MHz, CDCl3) δ 4.42 (d, J = 8.8 Hz, 1H), δ 4.17 (d, J = 8.8Hz, 1H);
[0066] The boiling point (bp) is 70 ℃ / 760 mm Hg.
[0067] Example 4
[0068] Preparation of difluorophosphate compounds 4:
[0069] S1. Prepare the intermediate shown in Formula A, following the same steps as in Example 1;
[0070] S2. Under a nitrogen atmosphere, the intermediate (0.07 mol) shown in Formula A was dissolved in 40 mL of anhydrous tetrahydrofuran at room temperature. The solution was cooled to -5 °C, and then CH3SH (0.11 mol) and N,N-diisopropylethylamine (0.14 mol) were added. The mixture was stirred for 4 h. After the reaction was completed, 30 mL of ethyl acetate and 40 mL of water were added to the reaction solution for extraction. The extraction was repeated twice. The organic phases were combined, dried with anhydrous sodium sulfate, and filtered to remove the anhydrous sodium sulfate. The filtrate was first purified by rotary evaporation to remove the solvent, and then purified by distillation at atmospheric pressure. The fraction from 80 °C to 83 °C was collected to obtain 8.0 g of pale yellow liquid, which is difluorophosphate compound 4 (yield 86.6%, GC purity 98%).
[0071] Structure and characterization of difluorophosphate compound 4:
[0072]
[0073] 1H NMR (400 MHz, CDCl3) δ 2.04 (s, 3H);
[0074] Boiling point (bp) is 82 ℃ / 760 mm Hg.
[0075] Example 5
[0076] Preparation of difluorophosphate compounds 5:
[0077] S1. Prepare the intermediate shown in Formula A, following the same steps as in Example 1;
[0078] S2. Under a nitrogen atmosphere, the intermediate shown in Formula A (0.07 mol) was dissolved in 40 mL of anhydrous acetonitrile at room temperature, cooled to -5 °C, and then (CH3)2CHCH2SH (0.11 mol) and N,N-diisopropylethylamine (0.14 mol) were added. The mixture was stirred for 4 h. After the reaction was completed, 30 mL of ethyl acetate and 35 mL of water were added to the reaction solution for extraction. The extraction was repeated twice. The organic phases were combined, dried with anhydrous sodium sulfate, and filtered to remove the anhydrous sodium sulfate. The filtrate was first purified by rotary evaporation to remove the solvent, and then purified by distillation at atmospheric pressure. The fraction from 84 °C to 86 °C was collected to obtain 10.7 g of pale yellow liquid, which is difluorophosphate compound 5 (yield 87.8%, GC purity 98%).
[0079] Structure and characterization of difluorophosphate compound 5:
[0080]
[0081] 1 H NMR (400 MHz, CDCl3) δ 2.49 (d, J = 4.8 Hz, 2H), 1.95 (tddt, J =11.7, 7.0, 4.9, 2.2 Hz, 1H), 0.91 (d, J = 6.9 Hz, 6H);
[0082] Boiling point (bp) is 85 ℃ / 760 mm Hg.
[0083] The above description is only a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any equivalent substitutions or modifications made by those skilled in the art within the scope of the technology disclosed in the present invention, based on the technical solution and inventive concept of the present invention, should be covered within the scope of protection of the present invention.
Claims
1. A method for synthesizing a difluorophosphate compound, characterized in that, Includes the following steps: S1. Under a protective atmosphere, pyrophosphoryl chloride is reacted with a fluorinating agent in the first solvent to obtain the intermediate shown in Formula A: Formula A; The reaction temperature is -50℃ to -30℃; S2. Under a protective atmosphere, the intermediate shown in Formula A is reacted with the nucleophile R-XH in a second solvent in the presence of an acid-binding agent to obtain the difluorophosphate compound shown in Formula I: Formula I; In Formula I, R-XH, X is selected from an oxygen atom or a sulfur atom, and R is selected from any one of substituted or unsubstituted straight-chain or branched C1-C5 alkyl groups or substituted or unsubstituted C6-C10 aryl groups; the substituted substituent is selected from at least one of -F, -CF3, -CN, -NO2, -CF2CF3, and -C(CF3)3. The reaction temperature is -5℃ to 0℃.
2. The method for synthesizing difluorophosphate compounds according to claim 1, characterized in that, In S1, the first solvent is selected from any one of acetonitrile, tetrahydrofuran, dichloromethane, and toluene; the ratio of pyrophosphoryl chloride to the first solvent is 1g:2~5mL.
3. The method for synthesizing difluorophosphate compounds according to claim 1, characterized in that, In S1, the fluorinating agent is selected from at least one of potassium fluoride, sodium fluoride, silver fluoride, zinc fluoride, ammonium fluoride, pyridinium hydrofluoride, and triethylamine hydrofluoride; the molar ratio of pyrophosphoryl chloride to the fluorinating agent is 1:4.2 to 1:4.
5.
4. The method for synthesizing difluorophosphate compounds according to claim 1, characterized in that, In step S1, after the reaction is complete, the following steps are also included: filtering the obtained reaction solution with diatomaceous earth and purifying the filtrate by distillation to obtain the final product.
5. The method for synthesizing difluorophosphate compounds according to claim 1, characterized in that, In S2, the second solvent is selected from any one of acetonitrile, tetrahydrofuran, dichloromethane, and toluene; the ratio of the intermediate shown in Formula A to the second solvent is 1g:3~5mL.
6. The method for synthesizing difluorophosphate compounds according to claim 1, characterized in that, In S2, the molar ratio of the intermediate shown in Formula A to the nucleophile R-XH is 1:1.2 to 1:1.
5.
7. The method for synthesizing difluorophosphate compounds according to claim 1, characterized in that, In S2, the acid-binding agent is selected from at least one of triethylamine, N,N-diisopropylethylamine, diethylamine, ethylamine, tert-butylamine, and N-tert-butylethylamine; the molar ratio of the intermediate shown in Formula A to the acid-binding agent is 1:2~3.
8. The method for synthesizing difluorophosphate compounds according to claim 1, characterized in that, In step S2, after the reaction is complete, the following steps are also included: adding ethyl acetate and water to the reaction solution for extraction, drying the obtained organic phase with a drying agent, filtering to remove the drying agent, removing the solvent from the filtrate by rotary evaporation, and then purifying by distillation to obtain the final product.
9. The method for synthesizing difluorophosphate compounds according to claim 1, characterized in that, In S1, the specific steps for reacting pyrophosphoryl chloride with a fluorinating agent in the first solvent include: dissolving the fluorinating agent in the first solvent at room temperature, then cooling the temperature to -50℃ to -30℃, and slowly adding pyrophosphoryl chloride dropwise under stirring to carry out the reaction; In S2, the specific steps of reacting the intermediate shown in Formula A with the nucleophile R-XH in a second solvent in the presence of an acid-binding agent include: dissolving the intermediate shown in Formula A in a second solvent at room temperature, cooling to -5℃~0℃, then adding the nucleophile R-XH and the acid-binding agent, and stirring the reaction.
10. The method for synthesizing difluorophosphate compounds according to claim 1, characterized in that, In S1, the reaction time is 2-5 hours; In S2, the reaction time is 4~8h.