Synthesis method of difluoromethylsulfonyl imide alkali metal salt

Abstract

The invention discloses a method for synthesizing difluoromethylsulfonyl imide alkali metal salt ([(CF2HSO2) (R1SO2) N] M, M = Li, Na, K, Rb, Cs). The method comprises the following steps: reacting an N-chlorine reagent with difluoromethyl sulfide to synthesize a key intermediate difluoromethylsulfonyl chloride; reacting the obtained difluoromethylsulfonyl chloride with sulfonamide containing a substituent group R1 or alkali metal salt thereof, and preparing difluoromethylsulfonyl imide salt containing active protons by taking weak nucleophilic inorganic and organic alkali as an acid-binding agent; and finally, reacting the difluoromethyl sulfonimide alkali metal salt with an alkali metal oxygen-containing compound and / or oxysalt to obtain the high-purity difluoromethyl sulfonimide alkali metal salt. The method has the characteristics of simple operation steps, mild reaction conditions, high operation safety, easiness in separation and purification of products and the like, and is suitable for industrial mass production.

Description

Technical Field

[0001] The present invention belongs to the technical fields of organofluorine chemistry, non-aqueous electrolyte materials, new materials and advanced power sources, and relates to a preparation method of an alkali metal conductive salt for a secondary battery system, and particularly relates to a synthesis method of an alkali metal salt of difluoromethylsulfonylimide. Background Art

[0002] As one of the key materials for high specific energy secondary battery systems, the basic physical, chemical and electrochemical properties of alkali metal conductive salts (such as chemical, electrochemical stability, electrode interface compatibility, etc.) directly affect the comprehensive performance of secondary battery systems. At present, alkali metal salts based on hexafluorophosphate (PF6 - ) are used as the main conductive salts and are widely applied to high specific energy secondary battery systems such as lithium-ion batteries and sodium-ion batteries [see: K. Xu, Chemical Reviews, 2014, 114, 11503; Ma Mengying et al., Energy Storage Science and Technology, 2020, 9(5), 1234–1250]. However, alkali metal hexafluorophosphate salts have poor chemical stability, and their non-aqueous electrolytes are easily decomposed to generate harmful substances such as phosphorus pentafluoride (PF5), phosphoryl trifluoride (POF3) and hydrogen fluoride (HF), greatly reducing the coulombic efficiency and cycle stability of the battery [see: Z. Song, Journal of Power Sources, 2022, 526, 231105; Wang Xingxing et al., Energy Storage Science and Technology, 2022, 11(4), 1226–1235].

[0003] In the past three decades, researchers have designed and synthesized various anion structures to improve the comprehensive performance of non-aqueous electrolytes. Among them, the bis(trifluoromethylsulfonyl)imide anion ([N(SO2CF3)2] - , TFSI -)The imide alkali metal salts represented by [have shown excellent chemical stability (e.g., not easily hydrolyzed, good tolerance to protic impurities, etc.) and relatively high thermal decomposition temperature (>300 °C). Their non-aqueous electrolytes have advantages such as high ionic conductivity and wide electrochemical window, and are considered as a class of conductive alkali metal salts with great application prospects [see: H. Zhang, Energy & Environmental Science, 2023, 16, 11; Wang Xuanchen et al., Energy Storage Science and Technology, 2023, 12(5), 1409–1425]. In particular, replacing the trifluoromethyl group (CF3) with the difluoromethyl group (CF2H) can effectively reduce the corrosion of the sulfonimide alkali metal salts to the current collector of the battery cathode, form a stable interfacial film on the surface of the aluminum foil current collector, and improve the electrochemical stability of the high-voltage electrode materials based on their non-aqueous electrolytes [see: L. Qiao, Nature Materials, 2022, 21, 455–462]. Therefore, the alkali metal salts of difluoromethylsulfonimide are an important class of new electrolyte conductive salt materials; however, the existing synthesis methods have disadvantages such as long reaction time, low conversion rate, and poor operation safety, resulting in the fact that this type of alkali metal salts has not been actually industrially applied in secondary battery systems.

[0004] Currently, the synthesis of alkali metal salts of difluoromethylsulfonimide mainly uses difluoromethylsulfonyl chloride (HCF2SO2Cl) to react with the corresponding sulfonamide salts. This reaction mainly has difficulties such as the difficult preparation of difluoromethylsulfonyl chloride, slow reaction rate, and low conversion rate. For example, using high-purity difluoromethylsulfonyl chloride as the starting material and synthesizing (difluoromethylsulfonyl)(trifluoromethylsulfonyl)imide ([N(SO2CF2H)(SO2CF3)] - , DFTFSI - ) by the above method, the reaction requires at least 48 hours and the yield is only 33% [see: L. Qiao, Nature Materials, 2022, 21, 455–462].

[0005] For the synthesis of the key intermediate difluoromethylsulfonyl chloride, 3M Company (Minnesota Mining and Manufacturing Company) in the United States proposed a synthetic route for preparing difluoromethylsulfonyl chloride by using benzyl difluoromethyl sulfide as a substrate and introducing chlorine gas [see: G. Moore, Journal of Organic Chemistry, 1979, 44, 1708–1711]. Experimental results show that this method involves the preparation and operation of hazardous gas chlorine, and has problems such as harsh synthesis conditions, large reaction latent heat, and low yield. Rhodia Chemical Company in France used difluorochloromethane as a raw material, added an aqueous sodium hydroxide solution and benzyl mercaptan in a Hastelloy high-pressure reactor, reacted to obtain benzyl difluoromethyl sulfide; and introduced chlorine gas to prepare difluoromethylsulfonyl chloride [see: S.J. Laurent et al, US Patent No. US2006178536]. This technical route mainly promotes reaction conversion by increasing the pressure of the reaction system, and has difficulties such as high requirements for reaction equipment and high operation safety risks. Therefore, the synthesis method of difluoromethylsulfonyl chloride with low cost, high conversion rate, and high operation safety is the main difficulty in preparing alkali metal salts of difluoromethylsulfonimide.

[0006] In addition, the carbon-hydrogen bond in the molecular structure of difluoromethylsulfonyl chloride (CF2HSO2Cl) has certain acidity, and it is easy to react with nucleophiles to generate various by-products with complex structures, resulting in difficulties in the separation and purification of alkali metal salts of difluoromethylsulfonimide. To sum up, the research and development of a method for preparing alkali metal salts of difluoromethylsulfonimide with low cost, environmental friendliness, high efficiency, and safe operation to meet the actual application needs of the industry is the key bottleneck for the large-scale application of alkali metal salts of difluoromethylsulfonimide in secondary batteries. Summary of the Invention

[0007] The task of the present invention is to provide a synthesis method, or preparation method, of alkali metal salts of difluoromethylsulfonimide, which has the characteristics of low cost, environmental friendliness, high conversion rate, and safe operation, so as to overcome the deficiencies of the above-mentioned existing technologies and realize the large-scale application of high-performance non-aqueous electrolyte materials based on alkali metal salts of difluoromethylsulfonimide. The molecular structure of the alkali metal salts of difluoromethylsulfonimide is shown in the following formula (I):

[0008]

[0009] In formula (I): M is Li, Na, K, Rb or Cs; R 1 is a substituent as described in any one of the following ① to ⑦:

[0010] ①R 1 is a perfluoroalkyl group of C m F 2m+1 where m is 0 or a positive integer from 1 to 8; preferably m is a positive integer from 1 to 4;

[0011] ②R 1 is C m F 2m+1 a perfluoroalkoxy of O, where m is a positive integer from 1 to 8, preferably m is a positive integer from 1 to 4;

[0012] ③R 1 is a fluoroalkyl containing fluorooxyethylene H(CF2CF2O) m CF2CF2 or F(CF2CF2O) m CF2CF2, where m is 0 or a positive integer from 1 to 6;

[0013] ④R 1 is C m H 2m+1 a hydrocarbyl group, where m is a positive integer from 1 to 10, preferably m is a positive integer from 1 to 4;

[0014] ⑤R 1 is C m H 2m+1 an alkoxy of O, where m is a positive integer from 1 to 10;

[0015] ⑥R 1 is C m X n H 2m+1-n a partially halogenated alkyl group, where X is F, Cl, Br or I; m is a positive integer from 1 to 10, n is a positive integer ≤ 2m + 1; preferably R 1 is CF2H, CH2F, CF3CH2, (CF3)2CH, CCl2H, CH2Cl or CCl3CH2;

[0016] ⑦R 1 is C m X n H 2m+1-n a partially halogenated alkoxy of O, where X is F, Cl, Br or I; m, n are positive integers, m = 1 - 10, n ≤ 2m + 1; preferably R 1 = CF3CH2O, (CF3)2CHO, ClCH2O, Cl2CHO or CCl3CH2O;

[0017] The technical solution to implement the present invention is:

[0018] The preparation method of the alkali metal salt of difluoromethylsulfonylimide provided by the present invention includes the following steps:

[0019] Step 1: In a non-aqueous solvent, mix an N-chlorine reagent, water and difluoromethyl thioether, and synthesize the intermediate difluoromethylsulfonyl chloride by an oxidative chlorination reaction;

[0020] Step 2: In a polar aprotic solvent, using a weakly nucleophilic inorganic and / or organic base as an acid scavenger, react the difluoromethylsulfonyl chloride prepared in Step 1 with a sulfonamide (R 1 SO2NH2) containing a substituent R 1 or its alkali metal salt (R 1 SO2NHM) to prepare a difluoromethylsulfonyl imide salt containing an active proton.

[0021] The sulfonamide (R 1 SO2NH2) containing a substituent R 1 described in Step 2 above has a structure shown in the following formula (II):

[0022]

[0023] R 1 in formula (II) is a substituent described in any one of the following ① to ⑦:

[0024] ① R 1 is a perfluoroalkyl group of C m F 2m+1 , where m is 0 or a positive integer from 1 to 8; preferably m is a positive integer from 1 to 4;

[0025] ② R 1 is a perfluorinated alkoxy group of C m F 2m+1 O, where m is a positive integer from 1 to 8, preferably m is a positive integer from 1 to 4;

[0026] ③ R 1 is a fluoroalkyl group containing fluorinated oxyethylene H(CF2CF2O) m CF2CF2 or F(CF2CF2O) m CF2CF2, where m is 0 or a positive integer from 1 to 6;

[0027] ④ R 1 is a hydrocarbyl group of C m H 2m+1 , where m is a positive integer from 1 to 10, preferably m is a positive integer from 1 to 4;

[0028] ⑤ R 1 is a hydrocarbyloxy group of C m H 2m+1 O, where m is a positive integer from 1 to 10;

[0029] ⑥ R 1 is a partially halogenated alkyl group of C m X n H 2m+1-n , where X is F, Cl, Br or I; m is a positive integer from 1 to 10, and n is a positive integer ≤ 2m + 1; preferably R1 is CF2H, CH2F, CF3CH2, (CF3)2CH, CCl2H, CH2Cl or CCl3CH2;

[0030] ⑦R 1 is C m X n H 2m+1-n a partially halogenated alkoxy group of C, where X is F, Cl, Br or I; m and n are positive integers, m = 1 to 10, n ≤ 2m + 1; preferably R 1 = CF3CH2O, (CF3)2CHO, ClCH2O, Cl2CHO or CCl3CH2O.

[0031] The sulfonamide (R 1 SO2NH2) containing the substituent R 1 in step two above, the alkali metal salt (R 1 SO2NHM) has a structure shown in the following formula (III):

[0032]

[0033] R in formula (III) 1 has the same meaning as R 1 in formula (II); M in formula (III) is Li, Na, K, Rb or Cs.

[0034] The structure of the difluoromethylsulfonimide salt containing an active proton described in step two above is shown in formula (IV),

[0035]

[0036] In formula (IV) is a cation containing an active proton.

[0037] Step three: React the difluoromethylsulfonimide salt containing an active proton (formula (IV)) prepared in step two with an alkali metal oxide or an oxygen-containing salt to prepare an alkali metal difluoromethylsulfonimide salt (formula (I)).

[0038] The N-chlorine reagent described in step one above is one of N-chlorosuccinimide (NCS), trichloroisocyanuric acid (TCCA), dichlorohydantoin (DCH), N-chlorophthalimide (NCPI), trichloromelamine (TCM), sodium p-toluenesulfonchloramide (chloramine T), N-chlorosaccharin (NCSa), N,N,N',N'-tetrachlorobenzene-1,3-disulfonamide (TCBDA), poly(N,N'-dichloro-N-ethylbenzene-1,3-disulfonamide) (PCBS), or a mixture composed of two or more of them;

[0039] In the above step 1, the feeding ratio of difluoromethyl sulfide, water, and N-chlorine reagent is as follows: the feeding ratio of difluoromethyl sulfide to water calculated by molar amount is 100:50 to 100:600, preferably 100:100 to 100:250; the feeding ratio of difluoromethyl sulfide to N-chlorine reagent calculated by molar amount is 100:20 to 100:500, preferably 100:50 to 100:400.

[0040] The non-aqueous solvent described in the above step 1 is one of toluene, xylene, n-hexane, n-pentane, cyclohexane, petroleum ether (boiling point 60°C to 90°C), chloroform, dichloromethane, 1,2-dichloroethane, tetrahydrofuran, methyl tert-butyl ether, ether, ethylene glycol dimethyl ether, 1,3-dioxolane, 1,4-dioxane, acetonitrile, dichloroacetonitrile, methyl acetate, ethyl acetate, butyl acetate, dimethyl carbonate, methyl ethyl carbonate, diethyl carbonate, ethylene carbonate, propylene carbonate, γ-butyrolactone, acetone, n-butyl ketone, 2-butanone, N-methylpyrrolidone, N,N-dimethylformamide, N,N-dimethylacetamide, dimethyl sulfoxide, sulfolane, 1,3-dimethylpropyleneurea (DMPU), 1,3-dimethyl-2-imidazolidinone (DMEU), or a mixture composed of two or more of them; preferably acetonitrile, dichloromethane, ether, methyl tert-butyl ether or dimethyl carbonate, or preferably a mixed solvent of acetonitrile and dichloromethane.

[0041] The reaction temperature of the reaction described in the above step 1 is a constant temperature or a gradually changing temperature from -20°C to 80°C; preferably, the reaction temperature range is 10°C to 60°C; the reaction time of the reaction is 2 hours to 48 hours, preferably the reaction time is 4 hours to 8 hours.

[0042] The weakly nucleophilic organic base used as an acid-binding agent in the above step 2 is one of imidazole, 1-methylimidazole, triazole, 2,6-dimethylpyridine, 2,6-di-tert-butylpyridine, diisopropylethylamine, 1,8-diazabicyclo[5.4.0]undec-7-ene (DBU), potassium hexamethyldisilazide, sodium hexamethyldisilazide, lithium hexamethyldisilazide, sodium tetramethylpiperidine, lithium tetramethylpiperidine, or a mixture composed of two or more of them; preferably imidazole, 1-methylimidazole, 2,6-dimethylpyridine or sodium hexamethyldisilazide, or preferably a mixture of imidazole and 2,6-dimethylpyridine.

[0043] The weakly nucleophilic inorganic base used as an acid-binding agent in the second step described above is one of potassium phosphate (K3PO4), sodium phosphate (Na3PO4), lithium phosphate (Li3PO4), dipotassium hydrogen phosphate (K2HPO4), disodium hydrogen phosphate (Na2HPO4), dilithium hydrogen phosphate (Li2HPO4), potassium dihydrogen phosphate (KH2PO4), sodium dihydrogen phosphate (NaH2PO4), lithium dihydrogen phosphate (LiH2PO4), sodium thiosulfate (Na2S2O3), potassium thiosulfate (K2S2O3), or a mixture composed of two or more of them; preferably potassium phosphate, lithium phosphate, dipotassium hydrogen phosphate or sodium dihydrogen phosphate, or preferably a mixture of potassium phosphate and sodium dihydrogen phosphate.

[0044] The polar aprotic solvent described in the second step above is one of tetrahydrofuran, methyl tert-butyl ether, diethyl ether, ethylene glycol dimethyl ether, 1,3-dioxolane, 1,4-dioxane, acetonitrile, dichloroacetonitrile, methyl acetate, ethyl acetate, butyl acetate, dimethyl carbonate, methyl ethyl carbonate, diethyl carbonate, ethylene carbonate, propylene carbonate, γ-butyrolactone, acetone, n-butyl ketone, 2-butanone, N-methylpyrrolidone, N,N-dimethylformamide, N,N-dimethylacetamide, dimethyl sulfoxide, sulfolane, 1,3-dimethylpropyleneurea (DMPU), 1,3-dimethyl-2-imidazolidinone (DMEU), or a mixture composed of two or more of them; preferably acetonitrile, dichloromethane, diethyl ether or methyl tert-butyl ether, or preferably a mixture of acetonitrile and methyl tert-butyl ether.

[0045] The reaction temperature of the reaction described in the second step is a constant temperature or a gradually changing temperature between -20°C and 150°C, and the preferred reaction temperature range is 40°C to 100°C; the reaction time of the reaction is 4 hours to 120 hours, and the preferred reaction time is 6 hours to 48 hours.

[0046] The alkali metal oxygen-containing compound described in the third step above is one of lithium oxide, sodium oxide, potassium oxide, lithium hydroxide, sodium hydroxide, rubidium hydroxide, cesium hydroxide, or a mixture composed of two or more of them. The alkali metal oxygen-containing salt described in the third step above is one of lithium hydrogencarbonate, sodium hydrogencarbonate, potassium hydrogencarbonate, rubidium hydrogencarbonate, cesium hydrogencarbonate, lithium carbonate, sodium carbonate, potassium carbonate, rubidium carbonate, cesium carbonate, lithium hydrogen phosphate, sodium hydrogen phosphate, potassium hydrogen phosphate, lithium phosphate, sodium phosphate, potassium phosphate, or a mixture composed of two or more of them.

[0047] The present invention discloses a method for synthesizing alkali metal salts of difluoromethylsulfonylimide ([(CF2HSO2)(R 1 SO2)N]M, M = Li, Na, K, Rb, Cs), which uses an N-chloro reagent to react with difluoromethyl sulfide to synthesize a key intermediate, difluoromethylsulfonyl chloride; then the obtained difluoromethylsulfonyl chloride is reacted with a compound containing a substituent R1 React with sulfonamide or its alkali metal salt, use weak nucleophilic inorganic and organic bases as acid-binding agents to prepare difluoromethylsulfonylimide salts containing active protons; finally react it with alkali metal oxygen-containing compounds and / or oxygen-containing salts to obtain high-purity alkali metal salts of difluoromethylsulfonylimide. This method has the characteristics of simple operation steps, mild reaction conditions, high operation safety, easy separation and purification of products, low cost, environmental friendliness, high efficiency, etc., is suitable for large-scale industrial production, and can achieve industrialized large-scale application.

[0048] The present invention uses a solid N-chloro reagent to replace highly dangerous chlorine gas, utilizes the controllable decomposition of the nitrogen-chlorine bond to generate a chlorine cation, promotes the conversion of benzyl sulfide to difluoromethylsulfonyl chloride, effectively improves the operation safety and product conversion rate of preparing difluoromethylsulfonyl chloride, and shortens the reaction time, significantly improving the production efficiency of difluoromethylsulfonyl chloride. In addition, the present invention uses weak nucleophilic organic and inorganic bases as acid-binding agents to promote the cleavage of the sulfur-chlorine bond in difluoromethylsulfonyl chloride, while avoiding side reactions of the acidic carbon-hydrogen bond (ClSO2F2C—H) in its molecular structure, effectively improving the conversion rate of alkali metal salts of difluoromethylsulfonylimide, while inhibiting the formation of complex by-products, having the advantages of simple post-treatment operation and high product purity, overcoming the deficiencies of the prior art, and meeting the actual needs of industrial production of alkali metal salts. Description of the Drawings

[0049] Figure 1 . 19F NMR spectrum of difluoromethylsulfonyl chloride synthesized using NCS as an oxidative chlorination reagent. The reaction solvent is acetonitrile, the reaction time is 4 hours, and the reaction temperature is 40 °C. The deuterated reagent is deuterated acetone.

[0050] Figure 2 . 19F NMR spectrum of triethylammonium difluoromethylsulfonylimide salt ([Et3NH][N(SO2CF2H)(SO2CF3)],[Et3NH][DFTFSI]) containing active protons prepared by ion exchange reaction using triethylammonium hydrochloride. The reaction solvent is water, the reaction time is 2 hours, and the reaction temperature is 25 °C. The deuterated reagent is deuterated acetone.

[0051] Figure 3 . 19F NMR spectrum of potassium (difluoromethylsulfonyl)(trifluoromethylsulfonyl)imide (KDFTFSI) prepared by neutralizing triethylammonium difluoromethylsulfonylimide salt containing active protons. The reaction solvent is acetonitrile and water, the reaction time is 2 hours, and the reaction temperature is 25 °C. The deuterated reagent is deuterated acetone. Detailed Description of the Invention

[0052] The following lists the preparation of some compounds involved in the present invention to further illustrate the present invention in detail, but the preparation methods in the examples are not limited to the preparation of the listed compounds.

[0053] The main instruments and equipment used in the examples are as follows: nuclear magnetic resonance spectrometer (AV 400M, Bruker, Switzerland), heat collecting constant temperature magnetic stirrer (DF-101S, Gongyi Yuhua Instrument Co., Ltd.).

[0054] The main sources of reagents used in the examples are: N-chlorosuccinimide (NCS, chemically pure Aladdin Reagent Co., Ltd.); trichloroisocyanuric acid (TCCA, chemically pure, Aladdin Reagent Co., Ltd.); 1,3-dichloro-5,5-dimethylhydantoin (DCH, chemically pure, Anaiji Chemical Reagent Co., Ltd.); acetonitrile (CH3CN, chemically pure, Sinopharm Chemical Reagent Co., Ltd.); ethanol (C2H5OH, chemically pure, Sinopharm Chemical Reagent Co., Ltd.); dichloromethane (CH2Cl2, chemically pure, Sinopharm Chemical Reagent Co., Ltd.); trifluoromethylsulfonamide (CF3SO2NH2, chemically pure, Solvay Group); imidazole (chemically pure, Aladdin Reagent Co., Ltd.); methyl tert-butyl ether (chemically pure, Sinopharm Chemical Reagent Co., Ltd.); triethylamine (Et3N, chemically pure, Sinopharm Chemical Reagent Co., Ltd.), pyridine (chemically pure, Sinopharm Chemical Reagent Co., Ltd.); the following drugs are homemade: benzyl difluoromethyl sulfide (PhCH2SCHF2), trifluoromethyl Potassium sulfonamide (CF3SO2NHK), potassium fluorosulfonamide (FSO2NHK), potassium pentafluoroethylsulfonamide (C2F5SO2NHK), potassium difluoromethylsulfonamide (CF2HSO2NHK), potassium perfluorobutylsulfonamide (n-C4F9SO2NHK), potassium trifluoroethoxysulfonamide (CF3CH2OSO2NHK), potassium hexafluoroisopropoxysulfonamide ((CF3)2CHOSO2NHK); hydrochloric acid (mass fraction 36.5%, Sinopharm Chemical Reagents Co., Ltd.); dipotassium hydrogen phosphate (chemically pure, Sinopharm Chemical Reagent Co., Ltd.); potassium bicarbonate (chemically pure, Sinopharm Chemical Reagent Co., Ltd.); anhydrous lithium carbonate (chemically pure, Sinopharm Chemical Reagent Co., Ltd.); anhydrous sodium carbonate (chemically pure, Sinopharm Chemical Reagent Co., Ltd.); anhydrous potassium carbonate (chemically pure, Sinopharm Chemical Reagent Co., Ltd.); anhydrous rubidium carbonate (chemically pure, Sinopharm Chemical Reagent Co., Ltd.); anhydrous cesium carbonate (chemically pure, Sinopharm Chemical Reagent Co., Ltd.).

[0055] 1. Synthesis of difluoromethanesulfonyl chloride (Example 1-7)

[0056] Example 1

[0057] In a 500 mL eggplant-shaped flask, successively add benzyl difluoromethyl sulfide (17.4 g, 0.1 mol), acetonitrile (100 g), and deionized water (3.6 g, 0.2 mol), and stir and mix evenly at room temperature. Then, under ice bath conditions, slowly dropwise add an acetonitrile solution (250 g) of N-chlorosuccinimide (54.5 g, 0.4 mol). After the addition is complete, gradually raise the temperature to 40 °C and continue stirring and reacting for 4 hours. After the reaction is complete, filter off the insoluble matter, dry the filtrate with anhydrous magnesium sulfate, and distill under atmospheric pressure to obtain 12.0 g of difluoromethylsulfonyl chloride, with a yield of 80%. The nuclear magnetic resonance hydrogen spectrum and fluorine spectrum of the obtained difluoromethylsulfonyl chloride ( Figure 1 ) data: 1 H NMR (Acetone-d6, TMS, 400 MHz, ppm): δ = 7.54 (t, J = 54.5 Hz, 1H); 19 F NMR (376.5 MHz, acetone-d6, CCl3F, ppm): δ = -116.28 ppm (d, J = 52.6 Hz, 2F).

[0058] Example 2

[0059] In Example 2, keep the feeding amounts of benzyl difluoromethyl sulfide and N-chlorosuccinimide unchanged, change the feeding amount of deionized water, and operate according to the steps in Example 1 to synthesize difluoromethylsulfonyl chloride. The feeding amounts of benzyl difluoromethyl sulfide and deionized water are calculated by molar amount and are 100:0, 100:200, 100:400, 100:600, and 100:10000 in turn, which are Example 2a, Example 2b, Example 2c, Example 2d, and Example 2e respectively. The corresponding experimental results are listed in Table 1.

[0060] As can be seen from Table 1, when using N-chlorosuccinimide as the oxidative chlorination reagent, the feeding ratio of benzyl difluoromethyl sulfide, N-chlorosuccinimide, and deionized water has a significant impact on the reaction yield. An appropriate amount of deionized water can significantly improve the reaction yield. In particular, the feeding ratio of difluoromethyl sulfide to water (calculated by molar amount) is 100:100 to 100:250; the feeding ratio of difluoromethyl sulfide to N-chlorine reagent (calculated by molar amount) is 100:50 to 100:400 is the preferred example.

[0061] Table 1. Synthesis of difluoromethylsulfonyl chloride using N-chlorosuccinimide at different feeding ratios

[0062]

[0063] Example 3

[0064] Example 3 used other temperatures instead of 40°C in Example 1. The other temperatures were 0°C and 80°C, which were Example 3a and Example 3b respectively. The operation was carried out according to the steps in Example 1 to synthesize difluoromethylsulfonyl chloride. The other reaction temperatures and the corresponding experimental results are listed in Table 2. It can be seen from Table 2 that when N-chlorosuccinimide was used as the oxidative chlorination reagent, the reaction was not easy to proceed at low temperatures, and the product hydrolysis was serious at high temperatures, both of which were not conducive to improving the reaction yield.

[0065] Table 2. Synthesis of difluoromethylsulfonyl chloride using N-chlorosuccinimide at different reaction temperatures

[0066] Serial number Reaction temperature / °C <![CDATA[Mass of HCF2SO2Cl / g]]> <![CDATA[Yield of HCF2SO2Cl / %]]> Example 1 40 12.6 85 Example 3a 0 6.3 42 Example 3b 80 2 13

[0067] Example 4

[0068] In a 500 mL eggplant-shaped flask, benzyl difluoromethyl sulfide (17.4 g, 0.1 mol), dichloromethane (350 g), and deionized water (3.6 g, 0.2 mol) were added in sequence, and stirred and mixed evenly at room temperature. Then, under ice bath conditions, solid N-chlorosuccinimide (54.5 g, 0.4 mol) was added in batches. After the addition of the solid was completed, the temperature was gradually raised to 40°C, and stirring was continued for 4 hours. After the reaction was completed, the insoluble substances were removed by filtration, the filtrate was dried with anhydrous magnesium sulfate, and difluoromethylsulfonyl chloride 12.8 g was obtained by atmospheric distillation, with a yield of 85%. The nuclear magnetic resonance hydrogen spectrum and fluorine spectrum data of the obtained difluoromethylsulfonyl chloride are as follows: 1 H NMR(Acetone-d6,TMS,400MHz,ppm):δ=6.14(t,J=54.5Hz,1H); 19 F NMR(376.5MHz,acetone-d6,CCl3F,ppm):δ=-116.28ppm(d,J=52.6Hz,2F).

[0069] Example 5

[0070] In Example 5, ethanol, water, acetonitrile / dichloromethane (1:1, mass ratio) were used as solvents instead of acetonitrile in Example 1, which were Example 5a, Example 5b, and Example 5c respectively. The operation was carried out according to the steps in Example 1 to synthesize difluoromethylsulfonyl chloride. The other reaction solvents and the corresponding experimental results are listed in Table 3.

[0071] Table 3. Synthesis of difluoromethylsulfonyl chloride using N-chlorosuccinimide in different reaction solvents

[0072] Serial number Reaction solvent <![CDATA[Mass of HCF2SO2Cl / g]]> <![CDATA[Yield of HCF2SO2Cl / %]]> Example 1 Acetonitrile 12.6 85 Example 5a Ethanol 0 0 Example 5b Water 0 0 Example 5c Acetonitrile / Dichloromethane 12.8 88

[0073] As can be seen from Table 3, when N-chlorosuccinimide is used as the oxidative chlorination reagent and a polar protic compound (such as ethanol, water) is used as the solvent, the reaction product undergoes severe hydrolysis and the target product, difluoromethylsulfonyl chloride, cannot be obtained. However, when a mixture of two non-aqueous solvents is used in the above reaction, difluoromethylsulfonyl chloride can be effectively prepared.

[0074] Example 6

[0075] In a 1000 mL eggplant-shaped flask, benzyl difluoromethyl sulfide (52.3 g, 0.3 mol), acetonitrile (300 g), and deionized water (10.8 g, 0.6 mol) were successively added and stirred at room temperature until evenly mixed. Then, under an ice bath condition, an acetonitrile solution (380 g) of trichloroisocyanuric acid (93.0 g, 0.4 mol) was slowly added dropwise. After the addition was complete, the temperature was gradually raised to 40 °C and stirring was continued for 4 hours. After the reaction was completed, the insoluble substances were removed by filtration, the filtrate was dried with anhydrous magnesium sulfate, and difluoromethylsulfonyl chloride (39.7 g) was obtained by atmospheric distillation, with a yield of 88%. The nuclear magnetic resonance hydrogen spectrum and fluorine spectrum data of the obtained difluoromethylsulfonyl chloride are as follows: 1 H NMR (Acetone-d6, TMS, 400 MHz) δ (ppm): 6.30 (t, J = 54.5 Hz, 1H); 19 F NMR (Acetone-d6, CCl3F, 376.5 MHz) δ (ppm): -116.30 ppm (d, J = 52.6 Hz, 2F).

[0076] Example 7

[0077] In a 500 mL eggplant-shaped flask, benzyl difluoromethyl sulfide (17.4 g, 0.1 mol), acetonitrile (100 g), and deionized water (3.6 g, 0.2 mol) were successively added and stirred at room temperature until evenly mixed. Then, under an ice bath condition, an acetonitrile solution (250 g) of 1,3-dichloro-5,5-dimethylhydantoin (DCDMH; 39.4 g, 0.2 mol) was slowly added dropwise. After the addition was complete, the temperature was gradually raised to 40 °C and stirring was continued for 4 hours. After the reaction was completed, the insoluble substances were removed by filtration, the filtrate was dried with anhydrous magnesium sulfate, and difluoromethylsulfonyl chloride (12.0 g) was obtained by atmospheric distillation, with a yield of 80%. The nuclear magnetic resonance hydrogen spectrum and fluorine spectrum data of the obtained difluoromethylsulfonyl chloride are as follows: 1 H NMR (Acetone-d6, TMS, 400 MHz) δ (ppm): 6.35 (t, J = 54.5 Hz, 1H); 19 F NMR (Acetone-d6, CCl3F, 376.5 MHz) δ (ppm): -116.25 ppm (d, J = 52.6 Hz, 2F).

[0078] From the experimental results of Example 1, Example 6 and Example 7, it can be seen that by using oxidation and chlorination reagents such as N-chlorosuccinimide, trichloroisocyanuric acid, 1,3-dichloro-5,5-dimethylhydantoin, etc., the key intermediate difluoromethylsulfonyl chloride can be synthesized at a mild reaction temperature (10 °C to 60 °C) and a short reaction time (4 hours to 8 hours).

[0079] 2. Synthesis of difluoromethylsulfonylimide salts containing active protons (Examples 8-13)

[0080] Example 8

[0081] In a 500 mL eggplant-shaped flask, imidazole (13.6 g, 200 mmol), potassium trifluoromethanesulfonamide (CF3SO2NHK, 18.7 g, 100 mmol), and anhydrous acetonitrile (60 mL) were added in sequence. After stirring and dissolving, a solution of difluoromethylsulfonyl chloride (CF2HSO2Cl, 15.0 g, 100 mmol) in acetonitrile (40 mL) was slowly added dropwise under an ice bath. After the addition was completed, the temperature was gradually raised to 85 °C, and the reaction was continued with stirring for 48 h. After the reaction was completed, the insoluble matter was removed by suction filtration under reduced pressure, and the filtrate was concentrated to obtain the product (difluoromethylsulfonyl)(trifluoromethylsulfonyl)imide imidazolium salt ([ImH][N(SO2CF2H)(SO2CF3)]), a light yellow liquid, 24.2 g), with a yield of 73%. 1H NMR and 19F NMR data of [ImH][N(SO2CF2H)(SO2CF3)]: 1 H NMR (Acetone-d6, TMS, 400 MHz) δ (ppm): 6.39 (t, J = 56.0 Hz, 1H); 19 F NMR (Acetone-d6, CCl3F, 376.5 MHz) δ (ppm): -79.28 (s, 3F), -124.87 (d, J = 52.7 Hz, 2F).

[0082] Example 9

[0083] In Example 9, triethylamine and pyridine were used instead of imidazole in Example 8, which were Example 9a and Example 9b respectively. The steps in Example 8 were followed to synthesize difluoromethylsulfonylimide salts containing active protons. The other organic acid-binding agents and the corresponding experimental results are listed in Table 4.

[0084] From the experimental results in Table 4, it can be seen that when using strong nucleophilic organic bases (such as triethylamine, pyridine, etc.) as acid-binding agents, it is easy to cause the decomposition of difluoromethylsulfonyl chloride, which is not conducive to the subsequent reaction with potassium trifluoromethanesulfonamide to form active proton intermediates, and the overall reaction yield is low (<60%).

[0085] Table 4. Synthesis of [C][DFTFSI] using different organic acid-binding agents

[0086] Serial number Acid-binding agent [C][DFTFSI] Mass / g [C][DFTFSI] Yield / % Example 8 Imidazole 24.2 73 Example 9a Triethylamine 16.9 51 Example 9b Pyridine 13.2 40

[0087] Example 10

[0088] Using an inorganic base as an acid-binding agent to synthesize triethylammonium difluoromethylsulfonylimide containing active protons ([Et3NH + [DFTFSI - ) is as follows.

[0089] To a 500 mL eggplant-shaped flask, potassium hydrogen phosphate (17.4 g, 100 mmol), potassium trifluoromethanesulfonamide (CF3SO2NHK, 18.7 g, 100 mmol), and anhydrous acetonitrile (60 mL) were successively added and stirred and mixed evenly at room temperature. A solution of difluoromethanesulfonyl chloride (HCF2SO2Cl, 15.0 g, 100 mmol) in acetonitrile (40 mL) was added dropwise to the above mixture, and then the temperature was gradually raised to the reflux temperature and heated for reaction for 48 hours. After the reaction was completed, the insoluble matter was removed by filtration, and the solvent in the filtrate was removed under vacuum to obtain potassium (difluoromethylsulfonyl)(trifluoromethylsulfonyl)imide (K[DFTFSI], white powder, 23.5 g), with a yield of 78%. 1H NMR and 19F NMR data of K[DFTFSI]: 1 1H NMR (Acetone-d6, TMS, 400 MHz) δ (ppm): 6.38 (t, J = 56.0 Hz, 1H); 19 19F NMR (Acetone-d6, CCl3F, 376.5 MHz) δ (ppm): -79.40 (s, 3F), -125.20 (d, J = 52.7 Hz, 2F).

[0090] To a 250 mL eggplant-shaped flask, the prepared K[DFTFSI] (15.1 g, 50 mmol), triethylammonium hydrochloride (6.9 g, 50 mmol), and deionized water (30 mL) were successively added and stirred and mixed evenly at room temperature. Subsequently, the lower layer solution was separated by standing, and the aqueous phase was extracted with dichloromethane. The low-boiling solvent was removed under reduced pressure to obtain triethylammonium difluoromethylsulfonylimide containing active protons ([Et3NH][DFTFSI], 17.3 g), with a yield of 95%. 1H NMR and 19F NMR Figure 2 ) data: 1 1H NMR (Acetone-d6, TMS, 400 MHz) δ (ppm): 6.41 (t, J = 54.3 Hz, 1H), 3.39 (q, J = 7.3 Hz, 6H), 1.37 (t, J = 7.3 Hz, 9H); 1919F NMR (Acetone-d6, CCl3F, 376.5 MHz) δ (ppm): -79.29 (s, 3F), -125.04 (d, J = 54.7 Hz, 2F).

[0091] Example 11

[0092] The experimental procedure for synthesizing imidazolium difluoromethylsulfonylimide salt ([ImH][DFTFSI]) containing active protons using inorganic base dipotassium hydrogen phosphate as an acid-binding agent is as follows:

[0093] In Example 11, imidazole hydrochloride was used instead of triethylamine hydrochloride in Example 10, and the procedure in Example 10 was followed to synthesize imidazolium difluoromethylsulfonylimide salt ([ImH][DFTFSI], 15.6 g) with a yield of 94%.

[0094] Example 12

[0095] In Example 12, other inorganic acid-binding agents were used instead of dipotassium hydrogen phosphate in Example 10. The other inorganic acid-binding agents were potassium carbonate and potassium bicarbonate, which were Example 12a and Example 12b respectively. The procedure in Example 10 was followed to synthesize triethylammonium difluoromethylsulfonylimide salt ([Et3NH][DFTFSI]). The other inorganic acid-binding agents and the corresponding experimental results are listed in Table 5.

[0096] From the experimental data in Table 5, it can be seen that when using carbonate or bicarbonate as an acid-binding agent, free water molecules are easily generated during the reaction, which in turn consumes difluoromethylsulfonyl chloride, resulting in a relatively low overall reaction yield (<60%).

[0097] Table 5. Synthesis of [Et3NH][DFTFSI] using different inorganic acid-binding agents

[0098] Serial number Acid-binding agent <![CDATA[[Mass of [Et3NH][DFTFSI] / g]]> <![CDATA[[Et3NH][DFTFSI] Yield / %]]> Example 10 Dipotassium hydrogen phosphate 12.4 68 Example 12a Potassium carbonate 9.3 51 Example 12b Potassium bicarbonate 7.3 40

[0099] Example 13

[0100] Example 13 uses sulfonamide (R 1 SO2NH2) or its alkali metal salt (R 1 SO2NHK) containing other substituents R 1 instead of potassium trifluoromethylsulfonamide (CF3SO2NHK) in Example 8. The sulfonamide containing other substituents R 1The alkali metal salts of sulfonamide are FSO2NHK, C2F5SO2NHK, n-C4F9SO2NHK, CF2HSO2NHK, CF3CH2OSO2NHK, (CF3)2CHOSO2NHK, which are Example 13a, Example 13b, Example 13c, Example 13d, Example 13e and Example 13f respectively. Operate according to the steps in Example 8 or Example 10 to synthesize difluoromethylsulfonylimide triethylamine salt ([Et3NH][DFSI]) containing other substituents R 1 and active proton. The other substituents R 1 and the corresponding experimental results are listed in Table 6.

[0101] Table 6. Synthesis of difluoromethylsulfonylimide triethylamine salt [Et3NH][DFSI] containing other substituents R 1 and active proton

[0102] Serial number <![CDATA[R 1 SO2NHK]]> <![CDATA[[Et3NH][DFSI] mass / g]]> <![CDATA[[Et3NH][DFSI] Yield / %]]> Example 13a <![CDATA[FSO2NHK]]> 15.1 96 Example 13b <![CDATA[C2F5SO2NHK]]> 19.7 95 Example 13c <![CDATA[C4F9SO2NHK]]> 23.7 92 Example 13d <![CDATA[CHF2SO2NHK]]> 16.5 95 Example 13e <![CDATA[CF3CH2OSO2NHK]]> 18.9 96 Example 13f <![CDATA[(CF3)2CHOSO2NHK]]> 21.5 93

[0103] The difluoromethylsulfonylimide triethylamine salts containing other substituents R 1 and active proton involved in Table 6 are triethylamine salt of (difluoromethylsulfonyl)(fluorosulfonyl)imide ([Et3NH][DFFSI]), triethylamine salt of (difluoromethylsulfonyl)(pentafluoroethylsulfonyl)imide ([Et3NH][DFPFSI]), triethylamine salt of (difluoromethylsulfonyl)(perfluorobutylsulfonyl)imide ([Et3NH][DFNFSI]), triethylamine salt of bis(difluoromethylsulfonyl)imide ([Et3NH][DFDFSI]), triethylamine salt of (difluoromethylsulfonyl)(trifluoroethoxysulfonyl)imide ([Et3NH][DFTFESI]) and triethylamine salt of (difluoromethylsulfonyl)(hexafluoroisopropoxysulfonyl)imide ([Et3NH][DFHFPSI]).

[0104] 3. Synthesis of alkali metal salts of difluoromethylsulfonylimide (Examples 14 - 16)

[0105] Example 14

[0106] Into a 250 mL eggplant-shaped flask, sequentially add difluoromethylsulfonylimide triethylamine salt containing active proton ([Et3NH][DFTFSI], 36.4 g, 100 mmol), lithium carbonate (Li2CO3, 3.7 g, 50 mmol), deionized water (50 mL) and dichloromethane (50 mL), and stir the reaction for one hour. After the reaction is completed, filter off the insoluble substances under reduced pressure, and at the same time distill off the low-boiling by-products and solvents under reduced pressure to obtain lithium (difluoromethylsulfonyl)(trifluoromethylsulfonyl)imide (LiDFTFSI, 25.6 g) with a yield of 95%. The 1H NMR and 19F NMR spectra of the obtained LiDFTFSI productFigure 3 ) Data: 1 H NMR (Acetone-d6, TMS, 400 MHz) δ (ppm): 6.38 (t, J = 56.0 Hz, 1H); 19 F NMR (Acetone-d6, CCl3F, 376.5 MHz) δ (ppm): -79.40 (s, 3F), -125.20 (d, J = 52.7 Hz, 2F)

[0107] Example 15

[0108] In Example 15, other alkali metal carbonates (M2CO3) were used instead of lithium carbonate (Li2CO3) in Example 14. The other alkali metal carbonates were Na2CO3, K2CO3, Rb2CO3, and Cs2CO3, which were Example 15a, Example 15b, Example 15c, and Example 15d respectively. According to the steps in Example 14, alkali metal salts of difluoromethylsulfonylimide were synthesized. The other alkali metal carbonates and the corresponding experimental results are listed in Table 7.

[0109] Table 7. Synthesis of M[DFTFSI] using different alkali metal carbonates

[0110] Serial number <![CDATA[M2CO3]]> M[DFTFSI] Mass / g M[DFTFSI] Yield / % Example 15a <![CDATA[Na2CO3]]> 27.1 95 Example 15b <![CDATA[Potassium carbonate]]> 28.6 95 Example 15c <![CDATA[Rb2CO3]]> 33.0 95 Example 15d <![CDATA[Cs2CO3]]> 37.5 95

[0111] Example 16

[0112] In Example 16, other alkali metal carbonates (M2CO3) were used instead of lithium carbonate (Li2CO3) in Example 14. According to the steps in Example 14, the triethylammonium salt of difluoromethylsulfonylimide [Et3NH][DFSI] containing other substituents R 1 and active protons was prepared into an alkali metal salt of difluoromethylsulfonylimide containing other substituents R 1 of.

[0113] The said containing other substituents R 1The triethylammonium salts of difluoromethylsulfonylimide with active protons are triethylammonium (difluoromethylsulfonyl)(fluorosulfonyl)imide ([Et3NH][DFFSI]), triethylammonium (difluoromethylsulfonyl)(pentafluoroethylsulfonyl)imide ([Et3NH][DFPFSI]), triethylammonium (difluoromethylsulfonyl)(perfluorobutylsulfonyl)imide ([Et3NH][DFNFSI]), triethylammonium bis(difluoromethylsulfonyl)imide ([Et3NH][DFDFSI]), triethylammonium (difluoromethylsulfonyl)(trifluoroethoxysulfonyl)imide ([Et3NH][DFTFESI]) and triethylammonium (difluoromethylsulfonyl)(hexafluoroisopropoxysulfonyl)imide ([Et3NH][DFHFPSI]), which are Example 16a, Example 16b, Example 16c, Example 16d, Example 16e and Example 16f respectively. The alkali metal salts of difluoromethylsulfonylimide and the corresponding experimental yields are listed in Table 8.

[0114] Table 8. Experimental yields (percentage) of alkali metal salts of difluoromethylsulfonylimide containing other substituents R 1

[0115] Serial number MDFSI type <![CDATA[Na2CO3]]> <![CDATA[K2CO3]]> <![CDATA[Rb2CO3]]> <![CDATA[Cs2CO3]]> Example 16a M[DFFSI] 95 95 94 94 Example 16b M[DFPFSI] 95 95 94 94 Example 16c M[DFNFSI] 95 94 95 93 Example 16d M[DFDFSI] 96 95 95 93 Example 16e M[DFTFESI] 94 94 93 93 Example 16f M[DFHFPSI] 94 94 94 93 .​

Claims

1. A method for preparing an alkali metal salt of difluoromethylsulfonimide, comprising the following steps: Step 1: In a non-aqueous solvent, an N-chlorine reagent, water and difluoromethyl methyl sulfide are mixed, and the intermediate difluoromethylsulfonyl chloride is synthesized by oxidative chlorination reaction; Step 2: In an aprotic polar solvent, using a weakly nucleophilic inorganic or / and organic base as an acid-binding agent, react the difluoromethylsulfonyl chloride prepared in Step 1 with a sulfonamide (R 1 SO2NH2) or its alkali metal salt (R 1 SO2NHM) containing a substituent R 1 to prepare a difluoromethylsulfonyl imide salt containing an active proton; The sulfonamide (R 1 ) containing the substituent R 1 SO2NH2) has the structure shown in formula (II), R in formula (II) 1 is a substituent selected from any one of the following ① to ⑦: ①R 1 is C m F 2m+1 perfluoroalkyl group, where m is an integer of 0 or from 1 to 8; preferably m is an integer from 1 to 4; ②R 1 is C m F 2m+1 is a perfluoroalkoxy group of O, where m is a positive integer from 1 to 8, preferably m is a positive integer from 1 to 4; ③R 1 is a fluoroalkyl H(CF2CF2O) containing fluorooxyethylene m CF2CF2 or F(CF2CF2O) m CF2CF2, where m is a positive integer from 0 or 1 to 6; ④R 1 is C m H 2m+1 hydrocarbyl group, wherein m is a positive integer from 1 to 10, preferably m is a positive integer from 1 to 4; ⑤R 1 is C m H 2m+1 hydrocarbyloxy of C, H, O, where m is a positive integer from 1 to 10; ⑥R 1 is C m X n H 2m+1-n is a partially halogenated alkyl group, where X is F, Cl, Br or I; m is a positive integer from 1 to 10, and n is a positive integer ≤ 2m + 1; preferably R 1 is CF2H, CH2F, CF3CH2, (CF3)2CH, CCl2H, CH2Cl or CCl3CH2; ⑦R 1 is C m X n H 2m+1-n a partially halogenated alkoxy group of O, where X is F, Cl, Br or I; m and n are positive integers, m = 1 to 10, n ≤ 2m + 1; preferably R 1 = CF3CH2O, (CF3)2CHO, ClCH2O, Cl2CHO or CCl3CH2O; The sulfonamide (R 1 ) containing a substituent R 1 SO2NH2) of the alkali metal salt (R 1 SO2NHM) has a structure as shown in formula (III), R in formula (III) 1 has the same meaning as R 1 in formula (II); M in formula (III) is Li, Na, K, Rb or Cs; The structure of the difluoromethylsulfonimide salt containing active protons is shown in formula (IV), In formula (IV) is a cation containing an active proton; Step 3: The difluoromethylsulfonimide salt (formula (IV)) containing active protons prepared in Step 2 is reacted with an alkali metal oxygen-containing compound or an oxygen-containing salt to prepare an alkali metal salt of difluoromethylsulfonimide (formula (I)).

2. The preparation method according to claim 1, wherein The N-chlorine reagent described in Step 1 is one of N-chlorosuccinimide (NCS), trichloroisocyanuric acid (TCCA), dichlorohydantoin (DCH), N-chlorophthalimide (NCPI), trichloromelamine (TCM), sodium p-toluenesulfonchloramide (chloramine T), N-chlorosaccharin (NCSa), N,N,N',N'-tetrachlorobenzene-1,3-disulfonamide (TCBDA), poly(N,N'-dichloro-N-ethylbenzene-1,3-disulfonamide) (PCBS), or a mixture composed of two or more of them.

3. The preparation method according to claim 1, wherein In Step 1, the feeding ratio of difluoromethyl methyl sulfide, water and N-chlorine reagent is: the feeding ratio of difluoromethyl methyl sulfide to water calculated by molar amount is 100:50 to 100:600, preferably 100:100 to 100:250; the feeding ratio of difluoromethyl methyl sulfide to N-chlorine reagent calculated by molar amount is 100:20 to 100:500, preferably 100:50 to 100:

400.

4. The preparation method according to claim 1, wherein The non-aqueous solvent described in Step 1 is one of toluene, xylene, n-hexane, n-pentane, cyclohexane, petroleum ether (boiling point 60°C to 90°C), chloroform, dichloromethane, 1,2-dichloroethane, tetrahydrofuran, methyl tert-butyl ether, ether, ethylene glycol dimethyl ether, 1,3-dioxolane, 1,4-dioxane, acetonitrile, dichloroacetonitrile, methyl acetate, ethyl acetate, butyl acetate, dimethyl carbonate, methyl ethyl carbonate, diethyl carbonate, ethylene carbonate, propylene carbonate, γ-butyrolactone, acetone, n-butyl ketone, 2-butyl ketone, N-methylpyrrolidone, N,N-dimethylformamide, N,N-dimethylacetamide, dimethyl sulfoxide, sulfolane, 1,3-dimethylpropyleneurea (DMPU), 1,3-dimethyl-2-imidazolidinone (DMEU), or a mixture composed of two or more of them; preferably acetonitrile, dichloromethane, ether, methyl tert-butyl ether or dimethyl carbonate, or preferably a mixed solvent of acetonitrile and dichloromethane.

5. The preparation method according to claim 1, characterized in that, The reaction temperature of the reaction described in Step 1 is a constant temperature or a gradually changing temperature from -20°C to 80°C; the preferred reaction temperature range is 10°C to 60°C.

6. The preparation method according to claim 1, wherein The reaction time of the reaction described in Step 1 is 2 hours to 48 hours; the preferred reaction time is 4 hours to 8 hours.

7. The preparation method according to claim 1, characterized in that, The weakly nucleophilic organic base used as an acid scavenger in Step 2 is one of imidazole, 1-methylimidazole, triazole, 2,6-dimethylpyridine, 2,6-di-tert-butylpyridine, diisopropylethylamine, 1,8-diazabicyclo[5.4.0]undec-7-ene (DBU), potassium hexamethyldisilazide, sodium hexamethyldisilazide, lithium hexamethyldisilazide, sodium tetramethylpiperidine, lithium tetramethylpiperidine, or a mixture composed of two or more of them; preferably imidazole, 1-methylimidazole, 2,6-dimethylpyridine or sodium hexamethyldisilazide, or preferably a mixture of imidazole and 2,6-dimethylpyridine.

8. The preparation method according to claim 1, characterized in that, The weakly nucleophilic inorganic base used as an acid scavenger in Step 2 is one of potassium phosphate (K3PO4), sodium phosphate (Na3PO4), lithium phosphate (Li3PO4), dipotassium hydrogen phosphate (K2HPO4), disodium hydrogen phosphate (Na2HPO4), dilithium hydrogen phosphate (Li2HPO4), potassium dihydrogen phosphate (KH2PO4), sodium dihydrogen phosphate (NaH2PO4), lithium dihydrogen phosphate (LiH2PO4), sodium thiosulfate (Na2S2O3), potassium thiosulfate (K2S2O3), or a mixture composed of two or more of them; preferably potassium phosphate, lithium phosphate, dipotassium hydrogen phosphate or sodium dihydrogen phosphate, or preferably a mixed acid scavenger of potassium phosphate and sodium dihydrogen phosphate.

9. The preparation method according to claim 1, wherein The polar aprotic solvent described in Step 2 is one of tetrahydrofuran, methyl tert-butyl ether, diethyl ether, ethylene glycol dimethyl ether, 1,3-dioxolane, 1,4-dioxane, acetonitrile, dichloroacetonitrile, methyl acetate, ethyl acetate, butyl acetate, dimethyl carbonate, methyl ethyl carbonate, diethyl carbonate, ethylene carbonate, propylene carbonate, γ-butyrolactone, acetone, n-butyl ketone, 2-butanone, N-methylpyrrolidone, N,N-dimethylformamide, N,N-dimethylacetamide, dimethyl sulfoxide, sulfolane, 1,3-dimethylpropyleneurea (DMPU), 1,3-dimethyl-2-imidazolidinone (DMEU), or a mixture composed of two or more of them; preferably acetonitrile, dichloromethane, diethyl ether or methyl tert-butyl ether, or preferably a mixed solvent of acetonitrile and methyl tert-butyl ether.

10. The preparation method according to claim 1, wherein The reaction temperature of the reaction described in Step 2 is a constant temperature or a gradient temperature between -20°C and 150°C; preferably the reaction temperature range is 40°C to 100°C; the reaction time of the reaction described in Step 2 is 4 hours to 120 hours; preferably the reaction time is 6 hours to 48 hours.

11. According to the preparation method described in claim 1, it is characterized in that, In Step 3, the alkali metal oxygen-containing compound is one of lithium oxide, sodium oxide, potassium oxide, lithium hydroxide, sodium hydroxide, rubidium hydroxide, cesium hydroxide, or a mixture composed of two or more of them; the alkali metal oxygen-containing salt described in Step 3 is one of lithium bicarbonate, sodium bicarbonate, potassium bicarbonate, rubidium bicarbonate, cesium bicarbonate, lithium carbonate, sodium carbonate, potassium carbonate, rubidium carbonate, cesium carbonate, lithium hydrogen phosphate, sodium hydrogen phosphate, potassium hydrogen phosphate, lithium phosphate, sodium phosphate, potassium phosphate, or a mixture composed of two or more of them.

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