A method for preparing hydrofluoroether and fluorinated ester

Abstract

The invention discloses a method for preparing a hydrofluoroether and a fluorinated ester, wherein an alkali metal salt is mixed with a polar aprotic solvent, and an excess of fluorinated alcohol is slowly added dropwise under a cold bath environment until the reaction is complete; the reaction mixture is transferred to an autoclave, and perfluoro-2-methyl-2,3-epoxypentane is added, and the reaction is carried out for 0.5 to 5 hours under the conditions of a temperature of 5 to 85 ° C and a stirring speed of 100 to 400 rpm; the mixed product is transferred to a round-bottomed flask for rectification and purification, and the fractions of hydrofluoroether and fluorinated ester are collected respectively, and the fluorinated alcohol as a solvent is recovered and reused. The present invention uses a polar aprotic solvent and a fluorinated alcohol as a mixed solvent, and solves the problem that perfluoro-2-methyl-2,3-epoxypentane and a fluorinated alcohol salt are difficult to react under fluorinated alcohol conditions. At the same time, the yield can be increased to more than 80%, and the final product purity reaches 99.5%, and in addition, the product hydrofluoroether and fluorinated ester have great economic value.

Description

(I) Technical field

[0001] The present invention belongs to the technical field of fine fluorine chemical industry, and specifically relates to a method for preparing hydrofluoroether and fluorine-containing ester, in particular, a method for using a mixed solvent of fluorine-containing alcohol and a polar aprotic solvent to open the ring of perfluoro-2-methyl-2,3-epoxypentane and a fluorine-containing alcohol salt to generate corresponding fluorine ether and fluorine ester. (II) Background technology

[0002] Hydrofluoroethers can be used as substitutes for fluorocarbons in cleaning agents, foaming agents, coolants, pharmaceutical intermediates, etc. In addition, hydrofluoroethers have good application prospects due to their low surface tension, non-flammability and other chemical properties or as additives in lithium battery electrolytes.

[0003] Fluorinated esters can be used as fluorinated building blocks and pharmaceutical intermediates. In recent years, as countries attach great importance to environmental protection, the scale of downstream industries such as lithium battery industry and new energy vehicles has continued to expand. As the requirements for safety, cycle life and energy density of lithium batteries increase, the demand for electrolyte additives increases year by year. Fluorinated esters can also be used as diluents in lithium metal batteries to improve battery performance under low temperature conditions and prevent structural degradation (such as cracks) of electrode materials, thereby making the battery have better cycle performance.

[0004] Documents ("synthesis and conversions of perfluoro(2,4-dimethyl-3-heptene)oxide", Zapevalov, A.Ya, "Zhurnal Organicheskoi Khimii", Vol. 20, No. 11, pp. 2267-3373, 19841231,) and Chinese invention patent CN112028747A all mention that, using methanol as solvent, perfluoro-2-methyl-2,3-epoxypentane and sodium methoxide generate hexafluoroisopropyl methyl ether and methyl pentafluoropropionate. This method is low in cost and simple to operate. According to general research ideas, using perfluoro-2-methyl-2,3-epoxypentane as raw material, replacing other fluorinated alcohols and sodium fluoroalcohol, according to the same reaction equation, corresponding hexafluoroisopropyl fluoride ether and fluoropentafluoropropionate should be obtained. However, in the actual research process, it was found that in the presence of only fluorinated alcohol solvents, the addition of raw material perfluoro-2-methyl-2,3-epoxypentane and bases such as NaH, NaOH almost did not react with perfluoro-2-methyl-2,3-epoxypentane. The reason is that the reaction is S N 2. It is difficult to carry out the forward nucleophilic reaction. Hexafluoroisopropyl fluoride and pentafluoropropionic acid fluoride cannot be prepared according to the technical routes provided by the original patents or literature.

[0005] Therefore, it is of great significance to further study its synthetic reaction pathway. (III) Summary of the invention

[0006] The invention aims to provide a method for preparing hydrofluoroether and fluorine-containing ester. Polar aprotic solvent and fluorine-containing alcohol are used as mixed solvents to make perfluoro-2-methyl-2,3-epoxypentane react with fluorine-containing alcohol salt, and simultaneously obtain corresponding hydrofluoroether and fluorine-containing ester. The problem that perfluoro-2-methyl-2,3-epoxypentane and fluorine-containing alcohol salt are difficult to react under the condition that fluorine-containing alcohol is used as solvent is solved, and perfluoro-2-methyl-2,3-epoxypentane can undergo ring-opening alkylation reaction.

[0007] Taking the reaction of perfluoro-2-methyl-2,3-epoxypentane with sodium trifluoroethoxide as an example, the reaction is S N 2 nucleophilic substitution, but due to the introduction of fluorine atoms in fluorinated alcohols, the fluorinated functional group has a strong electron-withdrawing ability, resulting in the lack of electrons in the epoxy bond, which is easily attacked by nucleophilic reagents. The nucleophilicity of trifluoroethoxy is relatively weak. The present invention successfully overcomes the defect that the reaction cannot proceed by introducing a polar aprotic solvent (see the schematic diagram of the reaction mechanism). Figure 1 ).

[0008] The technical solution adopted by the present invention is:

[0009] The present invention provides a method for preparing hydrofluoroether and fluorinated ester, the method comprising the following steps:

[0010] (1) An alkali metal salt is mixed with a polar aprotic solvent, and an excess of a fluorinated alcohol is slowly added dropwise in a cold bath environment until the reaction is complete to obtain a reaction mixture; the polar aprotic solvent is acetonitrile (ACN), N,N-dimethylformamide (DMF), N,N-dimethylacetamide (DMAC), dimethyl sulfoxide (DMSO), ethylene glycol dimethyl ether (DME), tetrahydrofuran, pyridine, and ethyl acetate; the alkali metal salt includes a hydride, carbonate, or bicarbonate of an alkali metal; the alkali metal includes lithium, sodium, and potassium; (2) The reaction mixture of step (1) is transferred to a high-pressure reactor, and perfluoro-2-methyl-2,3-epoxypentane is added, and the reaction is carried out at a temperature of 5 to 85° C. and a stirring speed of 100 to 400 rpm for 0.5 to 5 hours; (3) After the reaction of step (2) is completed, the mixed product is transferred to a round-bottom flask for distillation and purification, and the fractions of hydrofluoroether and fluorinated ester are collected respectively, and the fluorinated alcohol used as a solvent is recovered and reused.

[0011] Preferably, the alkali metal salt in step (1) is preferably NaH, Li2CO3, or KHCO3.

[0012] Preferably, the polar aprotic solvent in step (1) is acetonitrile, N,N-dimethylformamide, N,N-dimethylacetamide, dimethyl sulfoxide, or ethylene glycol dimethyl ether.

[0013] Preferably, the cold bath environment in step (1) is -25 to -5°C, and more preferably the cold bath temperature is -15 to -5°C.

[0014] Preferably, the fluorine-containing alcohol in step (1) includes long-chain fluorine-containing alcohols such as 2-fluoroethanol, 2,2-difluoroethanol, 2,2,2-trifluoroethanol, 3-fluoropropanol, 2,2,3,3-tetrafluoropropanol, 1H,1H-pentafluoropropanol, 1H,1H-perfluoro-1-pentanol, etc. More preferably, the fluorine-containing alcohol is 2-fluoroethanol, 2,2,2-trifluoroethanol, 2,2-difluoroethanol, 3-fluoropropanol, 2,2,3,3-tetrafluoropropanol, 1H,1H-perfluoro-1-pentanol.

[0015] Preferably, the molar ratio of the alkali metal salt to the fluorine-containing alcohol in step (1) is 1:2.5-5, and more preferably 1:2.5-4. The molar ratio of the alkali metal salt to the polar aprotic solvent is 1:1-5, and more preferably 1:1-4.

[0016] Preferably, in step (1), a polar aprotic solvent is added to an alkali metal salt under cold bath conditions, and then a fluorinated alcohol is slowly added dropwise (dropping speed 1 drop / 5 seconds) to generate a fluorinated alcohol salt which is dissolved in a mixed solvent.

[0017] Preferably, the molar ratio of the perfluoro-2-methyl-2,3-epoxypentane in step (2) to the alkali metal salt in step (1) is 0.1 to 0.5:1, and a more preferred molar ratio is 0.2 to 0.4:1.

[0018] Preferably, the reaction conditions of step (2) are preferably: reaction temperature of 15-35° C., stirring speed of 200-300 r / min, and reaction time of 1-3 h.

[0019] Preferably, in step (3), the hydrofluoroether is preferably hexafluoroisopropyl trifluoroethyl ether, with a fraction of 77.5°C; and the fluorinated ester is trifluoroethyl pentafluoropropionate, with a fraction of 70°C.

[0020] The present invention also provides an application of the fluorinated ether and fluorinated ester prepared by the method in the preparation of lithium battery electrolyte or pharmaceutical intermediates. The fluorinated ether prepared by the method is mainly used in the fields of lithium battery electrolyte additives, cleaning agents, foaming agents, coolants, and pharmaceutical intermediates, and the fluorinated ester is mainly used in the fields of lithium battery electrolyte additives, fluorinated building blocks, and pharmaceutical intermediates.

[0021] Compared with the prior art, the beneficial effects of the present invention are mainly reflected in:

[0022] The present invention adopts polar aprotic solvent and fluorine-containing alcohol as mixed solvent, and solves the problem that perfluoro-2-methyl-2,3-epoxypentane and fluorine-containing alcohol salt are difficult to react under fluorine alcohol conditions. Compared with the original technology, the reaction can proceed smoothly. Since the addition of polar aprotic solvent makes each solvent soluble in the other, the reaction can be started without high stirring speed. At the same time, the yield can be increased to more than 80%, and the purity of the final product reaches 99.5%. In addition, the product hydrofluoroether and fluorine-containing ester have great economic value. (IV) Description of the drawings

[0023] Figure 1 This is a schematic diagram of the ring-opening alkylation reaction of perfluoro-2-methyl-2,3-epoxypentane with a fluorine-containing alcohol salt in Example 1.

[0024] Figure 2 This is the mass spectrum of hexafluoroisopropyl trifluoroethyl ether in Example 1.

[0025] Figure 3 This is the mass spectrum of trifluoroethyl pentafluoropropionate in Example 1.

[0026] Figure 4 is the hexafluoroisopropyl trifluoroethyl ether in Example 1 1 H-NMR spectrum.

[0027] Figure 5 For the trifluoroethyl pentafluoropropionate in Example 1 1 H-NMR spectrum.

[0028] Figure 6 is the hexafluoroisopropyl trifluoroethyl ether in Example 1 19 F-NMR spectrum.

[0029] Figure 7 For the trifluoroethyl pentafluoropropionate in Example 1 19 F-NMR spectrum.

[0030] Figure 8 This is the infrared spectrum of hexafluoroisopropyl trifluoroethyl ether in Example 1.

[0031] Fig. 9 This is the infrared spectrum of trifluoroethyl pentafluoropropionate in Example 1. (V) Specific implementation methods

[0032] The present invention is further described below in conjunction with specific embodiments, but the protection scope of the present invention is not limited thereto:

[0033] Example 1

[0034] (1) Add 9 g of sodium hydride (purity 60%, 0.225 mol) and 19.56 g (0.268 mol) of N,N-dimethylformamide to a round-bottom flask. Start stirring and slowly add 107.13 g (1.071 mol) of 2,2,2-trifluoroethanol dropwise (dropping speed 1 drop / 5 seconds) in a cold bath (-5°C) until the sodium hydride reacts completely (the reaction is considered complete when no bubbles are generated).

[0035] (2) The reaction mixture of step (1) (i.e., containing sodium 2,2,2-fluorotrifluoroethanol and excess 2,2,2-trifluoroethanol) was transferred to a high-pressure reactor, and 23.7 g (0.075 mol) of perfluoro-2-methyl-2,3-epoxypentane was added. The stirring speed was controlled at 300 rpm and the reaction was carried out at 35° C. for 1 hour.

[0036] (3) After the reaction of step (2) was completed, the mixed product was transferred to a round-bottom flask for distillation and purification. The 70°C fraction was collected to obtain 14.5 g of trifluoroethyl pentafluoropropionate with a yield of 79%. The mass spectrum is shown in FIG. Figure 3 , 1 H-NMR diagram Figure 5 , 19 F-NMR diagram Figure 7 , infrared spectrum see Fig. 9 The characteristic fragment ion peak analysis is shown in Table 2. The fraction at 77.5°C was collected to obtain 13.5 g of hexafluoroisopropyl trifluoroethyl ether with a yield of 72%. The mass spectrum is shown in Figure 2 , 1 H-NMR diagram Figure 4 , 19 F-NMR diagram Figure 6 , infrared spectrum see Figure 8 The characteristic fragment ion peak analysis is shown in Table 1. At the same time, 85.4 g of 2,2,2-trifluoroethanol as a solvent was recovered, and the recovery rate reached 80%.

[0037] Table 1 Analysis of characteristic fragment ion peaks of hexafluoroisopropyl trifluoroethyl ether

[0038]

[0039] Table 2 Characteristic fragment ion peak analysis of trifluoroethyl pentafluoropropionate

[0040]

[0041] Examples 2-5, Comparative Example 1, Comparative Example 2

[0042] The reaction reagents and reaction conditions were changed on the basis of Example 1, so they are presented in a tabular form, see Table 3, DMSO represents dimethyl sulfoxide, DMF represents N,N-dimethylformamide, ACN represents acetonitrile, and DME represents ethylene glycol dimethyl ether.

[0043] Table 3 Reaction conditions and results of Examples 2-5, Comparative Example 1 and Comparative Example 2

[0044]

Claims

1. A method for preparing hydrofluoroether and fluorinated ester, characterized in that: The method comprises the following steps: (1) An alkali metal salt is mixed with a polar aprotic solvent, and an excess of a fluorinated alcohol is slowly added dropwise in a cold bath environment until the reaction is complete; the alkali metal salt is NaH or KHCO3; the polar aprotic solvent is acetonitrile, N,N-dimethylformamide, N,N-dimethylacetamide, dimethyl sulfoxide, or ethylene glycol dimethyl ether; the fluorinated alcohol is 2-fluoroethanol, 2,2-difluoroethanol, 2,2,2-trifluoroethanol, 3-fluoropropanol, or 2,2,3,3-tetrafluoropropanol; the molar ratio of the alkali metal salt to the fluorinated alcohol is 1:2-5; the molar ratio of the alkali metal salt to the polar aprotic solvent is 1:1-5; (2) The reaction mixture of step (1) is transferred to a high pressure reactor, and perfluoro-2-methyl-2,3-epoxypentane is added thereto, and the reaction is carried out at a temperature of 5-85°C and a stirring speed of 100-400 rpm for 0.5-5 rpm. h; the molar ratio of the perfluoro-2-methyl-2,3-epoxypentane to the alkali metal salt in step (1) is 0.1-0.5:1; (3) after the reaction in step (2) is completed, the mixed product is distilled and purified, and the fractions of the hydrofluoroether and the fluorinated ester are collected separately, and the fluorinated alcohol used as a solvent is recovered and reused.

2. The method for preparing hydrofluoroether and fluorinated ester according to claim 1, characterized in that: Step (1) The cold bath environment is -25~-5 ℃.

3. The method for preparing hydrofluoroether and fluorinated ester according to claim 1, characterized in that: In step (2), the reaction temperature is 15-35°C, the stirring speed is 200-300 r / min, and the reaction time is 1-3 h.

4. The method for preparing hydrofluoroether and fluorinated ester according to claim 1, characterized in that: In step (3), the hydrofluoroether is hexafluoroisopropyl trifluoroethyl ether, and the fraction is 77.5°C; the fluorinated ester is trifluoroethyl pentafluoropropionate, and the fraction is 70°C.

5. The method for preparing hydrofluoroether and fluorinated ester according to claim 1, characterized in that: The prepared fluorinated ethers and fluorinated esters are used in preparing lithium battery electrolytes or pharmaceutical intermediates.

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