A preparation method of trifluoromethyl alkyl sulfone

Abstract

The present invention provides a method for preparing trifluoromethyl alkyl sulfone, which belongs to the field of organic chemistry. The present invention provides a reaction formula for the preparation method of trifluoromethyl alkyl sulfone as follows: wherein R is a C1-C6 alkyl group, and X is chlorine, bromine or iodine, comprising the following reaction steps: under an inert atmosphere, reacting compound 1 and compound 2 in the presence of an ether solvent, and post-treating to obtain compound 3. The present application creatively selects trifluoromethanesulfonic anhydride as a reaction substrate, so the reaction provided by the present invention reduces the generation of by-products, improves the reaction yield, and is conducive to the industrial production of trifluoromethyl alkyl sulfone compounds.

Description

[0001] Related patent applications

[0002] This patent application claims priority to Chinese patent application 202210915837.3 filed on August 1, 2022, the entire text of which is incorporated herein by reference. Technical Field

[0003] The present invention relates to the field of organic chemistry, and in particular to a method for preparing trifluoromethyl alkyl sulfone. Background Art

[0004] Numerous literature reports indicate that sulfone compounds can be used as battery electrolytes. Specifically, Chinese patent application CN114008824A reports that certain sulfone compounds, such as trifluoromethyl methyl sulfone, trifluoromethyl n-propyl sulfone, trifluoromethyl isopropyl sulfone, trifluoromethyl n-butyl sulfone, and trifluoromethyl tert-butyl sulfone, exhibit good ionic conductivity and high input / output when used as electrolytes.

[0005] However, there is currently no method for conveniently and efficiently preparing the above-mentioned trifluoromethyl alkyl sulfone.

[0006] For example, U.S. Patent No. 3,776,960A describes a method for preparing trifluoromethyl alkyl sulfone, which involves reacting trifluoromethanesulfonyl fluoride with a methyl Grignard reagent to ultimately produce a mixture of di(trifluoromethanesulfonyl)methane and trifluoromethyl methyl sulfone. These two compounds have similar properties and are difficult to purify and separate subsequently.

[0007] For example, the paper Epoxide Ring Opening by α-Sulfonyl Carbanions. Synthesis of γ-Hydroxy Sulfones and Triflones (Synthetic Communications, 16:3, 309-329) also reported a method for preparing trifluoromethyl methyl sulfone by reacting trifluoromethanesulfonyl fluoride with methyl Grignard reagent, but the yield was only 58%.

[0008] In addition, trifluoromethanesulfonyl fluoride is highly toxic, expensive, and highly corrosive, making it unsuitable for industrial production.

[0009] For example, the paper "Reaction of triflic anhydride with Grignard reagents. Oxidizing properties of triflic anhydride" (J. Org. Chem. 45, 2727-2729) reports a method for preparing trifluoromethyl alkyl sulfones by reacting alkyl magnesium chlorides with trifluoromethyl anhydride. However, the document specifically points out that alkyl magnesium bromide is not a suitable option for preparing trifluoromethyl sulfone compounds because the document believes that the main product obtained by the reaction of alkyl magnesium bromide with trifluoromethyl anhydride is a brominated alkane.

[0010] However, as mentioned above, trifluoromethyl alkyl sulfones are primarily used as battery electrolytes. However, according to the industry standard SJ / T 11724-2018 for electrolytes for lithium primary batteries, the chloride ion content in lithium battery electrolytes must be less than 5.0 mg / kg, while there is no requirement for bromide ions. Products prepared using alkyl magnesium chlorides inevitably contain a certain amount of chloride ions, which undoubtedly places higher demands on the subsequent purification of the product. Summary of the Invention

[0011] The present invention is made to solve the above problems and aims to provide a method for preparing trifluoromethyl alkyl sulfone with cheap and readily available raw materials and high yield.

[0012] The present invention provides a method for preparing trifluoromethyl alkyl sulfone, which has the following characteristics:

[0013]

[0014] In the formula, R is a C1-C6 alkyl group, X is chlorine, bromine or iodine, and the reaction comprises the following steps:

[0015] Under an inert atmosphere, compound 1 and compound 2 are reacted in the presence of an ether solvent and post-treated to obtain compound 3.

[0016] The preparation method of trifluoromethyl alkyl sulfone provided by the present invention may also have the following characteristics: wherein R in the reaction formula is any one of methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, cyclopentyl or cyclohexyl.

[0017] The method for preparing trifluoromethyl alkyl sulfone provided by the present invention may also have the following characteristics: wherein the ether solvent is any one or more of diethyl ether, propyl ether, tert-butyl ether or tert-butyl methyl ether.

[0018] The method for preparing trifluoromethyl alkyl sulfone provided by the present invention may also have the following characteristics: wherein the molar ratio of compound 1 to compound 2 is 1:(2-3).

[0019] The method for preparing trifluoromethyl alkyl sulfone provided by the present invention may also have the following characteristics: wherein the reaction temperature is -20°C to -10°C.

[0020] The method for preparing trifluoromethyl alkyl sulfone provided by the present invention may also have the following characteristics: wherein, the method further comprises the following reaction steps:

[0021] Compound 1 is mixed with a solvent, and the reaction system is cooled to -80°C to -40°C under an inert atmosphere. Compound 2 is added dropwise and reacted at -20°C to -10°C for 1-5 hours. After post-treatment, compound 3 is obtained.

[0022] The method for preparing trifluoromethyl alkyl sulfone provided by the present invention may also have the following characteristics: wherein the post-treatment comprises the following steps:

[0023] Water or an aqueous solution of an inorganic salt is added to quench the reaction, the liquids are separated, the organic phase is taken, washed with water, washed with saturated brine, dried, and distilled to obtain compound 3.

[0024] The method for preparing trifluoromethyl alkyl sulfone provided by the present invention may also have the following characteristics: wherein, the method comprises the following reaction steps:

[0025] Add compound 1 and an ether solvent to a dry reaction vessel, cool to -80°C to -40°C, and add compound 2 dropwise under an inert atmosphere. After the addition is complete, react at -20°C to -10°C for 1-5 hours, add an aqueous ammonium chloride solution to quench the reaction, separate the liquids, take the organic phase, wash with water, wash with saturated brine, dry, and distill to obtain compound 3.

[0026] Functions and effects of the invention

[0027] According to the method for preparing trifluoromethyl alkyl sulfones involved in the present invention, since trifluoromethanesulfonic anhydride is creatively selected as the reaction substrate, the reaction provided by the present invention reduces the generation of by-products, improves the reaction yield, and is conducive to the industrial production of trifluoromethyl alkyl sulfone compounds. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 This is the GCMS spectrum of the reaction control in Example 1 of the present invention;

[0029] Figure 2 is the hydrogen spectrum of trifluoromethyl methyl sulfone prepared in Example 1 of the present invention; and

[0030] Figure 3 This is the fluorine spectrum of trifluoromethyl sulfone prepared in Example 1 of the present invention. DETAILED DESCRIPTION

[0031] In order to make the technical means, creative features, objectives and effects achieved by the present invention easier to understand, the present invention is described in detail below with reference to embodiments and drawings.

[0032] In the following examples, unless otherwise specified, all raw materials are commercially available products.

[0033] <Example 1>

[0034] Preparation method of compound 3a

[0035] This example provides a method for preparing compound 3a, and the reaction formula is as follows:

[0036]

[0037] The process comprises the following reaction steps:

[0038] 20 g of compound 1 (0.071 mol, 1.0 eq) was added to 100 mL of diethyl ether. The reaction system was cooled to -55°C after nitrogen was replaced. Under nitrogen protection, 59.1 mL of methylmagnesium chloride diethyl ether solution (3 mol / L, 0.177 mol, 2.5 eq) was slowly added dropwise. The temperature of the reaction system was controlled between -55°C±5°C during the addition. After the addition was completed, the temperature was raised to -15°C, and the reaction was stirred for 2 h. Samples were taken after 1 h of reaction and sent to GCMS for detection. The GCMS spectrum was as shown below. Figure 1 As shown, Figure 1 As shown, a considerable amount of target product 3a was produced in the reaction system and no formation of bis(trifluoromethylsulfonyl)methane impurity was observed.

[0039] After stirring for 2 h, 80 mL of a saturated aqueous solution of ammonium chloride was added to the reaction system to quench the reaction. The mixture was allowed to stand for separation, and the organic phase was taken. The organic phase was washed once with 100 mL of water and 100 mL of a saturated aqueous solution of common salt, respectively, and dried over anhydrous sodium sulfate overnight. The solvent was removed by distillation under reduced pressure, and 8.0 g of the target product was obtained by atmospheric distillation at 140 ° C. The yield was 76.0%.

[0040] <Example 2>

[0041] Screening of reaction solvents

[0042] This example screened the reaction solvent based on Example 1. In this example, except for the different solvents, the other conditions were the same as those in Example 1. The screening results are shown in Table 1.

[0043] Table 1 Screening of reaction solvents

[0044] Serial number Reaction solvent Yield 1 Tetrahydrofuran 38.8％ 2 2-Methyltetrahydrofuran 42.3％ 3 tert-Butyl methyl ether 61.4％ 4 Toluene 29.7％

[0045] As shown in Table 1, the reaction involved in this example exhibits a strong solvent effect, showing a good yield only in chain ethers, and a poor yield in other solvents.

[0046] <Example 3>

[0047] Screening of temperature when adding Grignard reagent

[0048] This example screened the reaction system temperature when the Grignard reagent was added dropwise based on Example 1. In this example, except for the reaction system temperature when the Grignard reagent was added dropwise, the other conditions were the same as those in Example 1. The screening results are shown in Table 2.

[0049] Table 2 Screening of temperature when adding Grignard reagent

[0050] Serial number Temperature (℃) Yield 1 -80±5 73.5％ 2 -20±5 56.8％ 3 0±5 50.0％

[0051] As shown in Table 2, the temperature when the Grignard reagent is added dropwise has a great influence on the product. As the temperature increases, the final reaction yield decreases significantly.

[0052] <Example 4>

[0053] Screening of reaction temperature

[0054] This example screened the reaction temperature based on Example 1. In this example, except for the reaction temperature, the other conditions were the same as those in Example 1. The screening results are shown in Table 3.

[0055] Table 3 Screening of reaction temperature

[0056] Serial number Reaction temperature Yield 1 -55℃ 66.1％ 2 0℃ 56.1％ 3 20℃ 44.4％

[0057] As can be seen from Table 3, the reaction involved in this example is quite sensitive to reaction temperature, and the yield varies greatly when the reaction is carried out at different temperatures. Specifically, when the reaction temperature is too low, it is not conducive to the rapid progress of the reaction, and a large amount of unreacted raw materials will still remain in the reaction system. When the reaction temperature is too high, more impurities will be generated, making it impossible to obtain the target product in high yield.

[0058] <Example 5>

[0059] Preparation method of compound 3a

[0060] This example provides a method for preparing compound 3a, and the reaction formula is as follows:

[0061]

[0062] The process comprises the following reaction steps:

[0063] 10 g of compound 1 (0.035 mol, 1.0 eq) was added to 50 mL of diethyl ether. The reaction system was cooled to -55°C after nitrogen was replaced. Under nitrogen protection, 29.3 mL of methylmagnesium bromide diethyl ether solution (3 mol / L, 0.088 mol, 2.5 eq) was slowly added dropwise. During the addition, the temperature of the reaction system was controlled between -55°C±5°C. After the addition was completed, the temperature was raised to -15°C, and the reaction was stirred for 2 h. Samples were taken after 2 h of reaction and sent to GCMS for detection. The GCMS spectrum showed that the reaction was complete.

[0064] After stirring for 2 h, 40 mL of a saturated aqueous solution of ammonium chloride was added to the reaction system to quench the reaction. The mixture was allowed to stand for separation, and the organic phase was taken and washed once with 50 mL of water and 50 mL of a saturated aqueous sodium chloride solution, respectively, and dried over anhydrous sodium sulfate overnight. The solvent was removed by distillation under reduced pressure, and 3.7 g of compound 3a was obtained by atmospheric distillation at 140°C in a yield of 70.5%.

[0065] Comparative Example 1

[0066] Reaction of benzylmagnesium bromide with trifluoromethanesulfonic anhydride

[0067] This comparative example provides the reaction of benzylmagnesium bromide and trifluoromethanesulfonic anhydride, and the reaction formula is as follows:

[0068]

[0069] The process comprises the following reaction steps:

[0070] 10 g of compound 1 (0.035 mol, 1.0 eq) was added to 50 mL of diethyl ether. The reaction system was replaced with nitrogen and cooled to -55 ° C. Under nitrogen protection, 88.0 mL of diethyl ether solution of benzylmagnesium bromide (1 mol / L, 0.088 mol, 2.5 eq) was slowly added dropwise. During the addition, the temperature of the reaction system was controlled between -55 ° C ± 5 ° C. After the addition was completed, the temperature was raised to -15 ° C, and the reaction was stirred for 2 h. Samples were taken at 2 h of reaction and sent to GCMS for detection. The GCMS spectrum showed that 73% of compound 4 and 12% of compound 3b were obtained.

[0071] Functions and Effects of the Embodiments

[0072] According to the preparation method of trifluoromethyl alkyl sulfone involved in the above embodiment, because trifluoromethanesulfonic anhydride is creatively selected as the reaction substrate, the reaction provided by the present invention reduces the generation of by-products, improves the reaction yield, and is conducive to the industrial production of trifluoromethyl alkyl sulfone compounds.

[0073] Furthermore, according to the preparation method of trifluoromethyl alkyl sulfone involved in the above embodiment, since diethyl ether is selected as the reaction solvent, and the appropriate temperature for adding the Grignard reagent and the appropriate reaction temperature are selected, the reaction yield is further improved.

[0074] Furthermore, the present invention uses methylmagnesium chloride as a reaction raw material, unexpectedly producing methyltrifluoromethyl sulfone in high yield, rather than the monobromomethane reported in the literature. This method avoids the incorporation of chloride ions, simplifying subsequent purification steps and therefore making it more suitable for use in battery electrolytes.

[0075] The above embodiments are preferred examples of the present invention and are not intended to limit the scope of protection of the present invention.

Claims

1. A method for preparing trifluoromethyl alkyl sulfone, characterized in that: The reaction formula is as follows: In the formula, R is methyl, X is bromine, The process comprises the following reaction steps: Compound 1 is mixed with a solvent, and the reaction system is cooled to -80°C to -40°C under an inert atmosphere. Compound 2 is added dropwise and reacted at -20°C to -10°C for 1h-5h. After post-treatment, compound 3 is obtained. The solvent is diethyl ether.

2. The method for preparing trifluoromethyl alkyl sulfone according to claim 1, wherein: in, The molar ratio of the compound 1 to the compound 2 is 1:(2-3).

3. The method for preparing trifluoromethyl alkyl sulfone according to claim 1, wherein in, Post-processing includes the following steps: Water or an aqueous solution of an inorganic salt is added to quench the reaction, the liquids are separated, the organic phase is taken, washed with water, washed with saturated brine, dried, and distilled to obtain compound 3.

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