A method for the preparation and purification of lithium 4,5-dicyano-2-trifluoromethylimidazole

Abstract

The application discloses a preparation and purification method of 4,5-dicyano-2-trifluoromethyl imidazole lithium. The application is characterized in that 4,5-dicyano-2-trifluoromethyl imidazole is obtained by slowly adding an aqueous solution of tert-butyl hydrogen peroxide under the condition of adding a solvent and water to 4,5-dicyano imidazole and sodium trifluoromethyl sulfinate, and stirring intensively and heating for a certain time. The crude 4,5-dicyano-2-trifluoromethyl imidazole is obtained by extracting multiple times with a solvent I and water. The lithium salt and water are added to the suspension, stirred and accompanied by a large amount of bubble generation. The activated carbon is added for decolorization, the activated carbon is removed by filtration after the decolorization is completed, and the mother liquor is rotary evaporated to remove water. The solvent II is added to remove the excess lithium salt by filtration, the mother liquor is recrystallized multiple times, and the high-purity 4,5-dicyano-2-trifluoromethyl imidazole lithium is obtained by filtration and drying. The application synthesizes 4,5-dicyano-2-trifluoromethyl imidazole from the perspective of trifluoromethylation. The reaction process is safer, the condition is milder, and a new idea is provided for industrial production.

Description

Technical Field

[0001] This invention relates to the field of chemical synthesis design, and in particular to a method for the preparation and purification of lithium 4,5-dicyano-2-trifluoromethylimidazolium. Background Technology

[0002] In recent years, the number of new energy vehicles has been increasing, driving the development of related industries. The electrolyte is the medium for lithium ion transport between the positive and negative electrodes in a lithium-ion battery. Besides the electrode materials, the advantages and disadvantages of lithium-ion batteries are closely related to the properties of the electrolyte. Lithium salts are the providers of lithium ions in the electrolyte, and their anions are the main factors determining the physical and chemical properties of the electrolyte.

[0003] Currently, the vast majority of commercially available lithium-ion batteries use LiPF6 as the electrolyte lithium salt. LiPF6 has the following outstanding advantages: (1) it has suitable solubility and high ionic conductivity in non-aqueous solvents; (2) it can form a stable passivation film on the surface of Al foil current collectors; (3) it is chemically inert; and (4) it can synergistically form a stable SEI film on the surface of graphite electrodes with carbonate solvents.

[0004] However, LiPF6 exhibits lower thermal stability than other lithium salts, decomposing even at high purity. Significant decomposition occurs when heated to 175–185°C, necessitating extreme caution during production, purification, storage, and use. The gaseous decomposition product PF5 shifts the reaction to the right, with decomposition being particularly severe at high temperatures. Furthermore, LiPF6 is highly sensitive to water; even trace amounts can lead to its decomposition, a major reason for its difficulty in preparation and purification. Its decomposition product, hydrofluoric acid (HF), is highly corrosive, causing battery performance degradation and increased interfacial resistance, thus impacting the cycle life of lithium batteries. Therefore, finding alternatives to LiPF6 is crucial.

[0005] Lithium 2-trifluoromethyl-4,5-dicyanimidazolium (LiTDI) is a novel imidazolium-derived salt that has become a potential alternative to LiPF6 due to its various performance advantages. Compared to LiPF6, LiTDI exhibits higher thermal stability and more stable degradation products, with a thermal decomposition temperature exceeding 250°C. This "Huckel"-type salt possesses high charge delocalization, which is beneficial for lithium-ion dissociation. In addition to its inherent stability, LiTDI provides excellent moisture protection in electrolytes. Studies have found that LiTDI, as an electrolyte additive that removes moisture, can effectively inhibit the hydrolysis of LiPF6. Through its interaction with water molecules, it effectively suppresses the hydrolysis of LiPF6, reducing the impact of decomposition products on the electrolyte composition. Therefore, adding only 1% LiTDI can improve electrolyte stability, thereby extending battery life. Furthermore, LiTDI does not corrode aluminum and can form a passivation layer to protect the current collector. It also exhibits a high electrochemical oxidation voltage and a high corrosion potential on the current collector aluminum foil, meeting the requirements for cathode materials in practical applications. It is worth mentioning that LiTDI helps form a stable solid electrolyte interphase (SEI) film, protecting the negative electrode from the degradation reaction of organic solvents. LiTDI, as an additive, works synergistically with traditional SEI additives to reduce battery impedance and significantly improve the battery's fast charge and discharge performance.

[0006] Currently, the main method for synthesizing LiTDI both domestically and internationally involves reacting trifluoroacetic anhydride and diaminobutenedionitrile in a 1,4-dioxane solution to yield 4,5-dicyano-2-trifluoromethylimidazolium (HTDI), followed by lithium salt formation to obtain lithium 4,5-dicyano-2-trifluoromethylimidazolium. This synthetic route uses trifluoroacetic anhydride with a boiling point of 40°C, which is highly volatile at room temperature, and improper use can easily lead to significant errors. Furthermore, excessively high local concentrations of trifluoroacetic anhydride can result in incomplete reactions and reduced yields. For industrial production, the reaction conditions are demanding, leading to high costs. Additionally, trifluoroacetic acid and trifluoroacetate esters can also react with diaminobutenedionitrile to generate HTDI. The reaction mechanism in both cases involves amidation of the amino group followed by dehydration and cyclization to form HTDI. Trifluoroacetic acid is highly corrosive, placing stringent requirements on equipment and materials. The synthetic route for trifluoroacetate esters involves three steps, and the high molecular weight of trifluoroacetate esters results in low atom utilization, increasing costs.

[0007] Building upon this foundation, we have broken through traditional synthetic approaches and proposed a novel synthetic method. This method synthesizes 4,5-dicyano-2-trifluoromethylimidazolium using 4,5-dicyanoimidazole and sodium trifluoromethylsulfinate. The trifluoromethylation of 4,5-dicyanoimidazole is achieved using sodium trifluoromethylsulfinate as the trifluoromethyl source and tert-butyl hydroperoxide as the oxidant. The reaction follows a free radical mechanism; sodium trifluoromethylsulfinate forms a trifluoromethyl radical under the action of tert-butyl hydroperoxide, which reacts with 4,5-dicyanoimidazole to achieve trifluoromethylation, generating 4,5-dicyano-2-trifluoromethylimidazolium. This is then reacted with a lithium salt to generate lithium 4,5-dicyano-2-trifluoromethylimidazolium. This method breaks through the conventional approach of using diaminobutenonitrile and trifluoroacetic anhydride, trifluoroacetic acid, and trifluoroacetate as raw materials, synthesizing 4,5-dicyano-2-trifluoromethylimidazolium from the perspective of trifluoromethylation. It offers greater safety and milder reaction conditions, which is beneficial for large-scale industrial production. Summary of the Invention

[0008] To address the shortcomings of existing technologies, this invention provides a method for the preparation and purification of lithium 4,5-dicyano-2-trifluoromethylimidazolium.

[0009] This invention provides a method for preparing 4,5-dicyano-2-trifluoromethylimidazole, the reaction process and route are as follows:

[0010]

[0011] Under conditions of adding solvent and water to 4,5-dicyanoimidazolium and sodium trifluoromethylsulfinate, an aqueous solution of tert-butyl hydroperoxide was slowly added while stirring vigorously, and the reaction was heated for a certain period of time to obtain 4,5-dicyano-2-trifluoromethylimidazolium. After the reaction was completed, the crude product 4,5-dicyano-2-trifluoromethylimidazolium was obtained by repeated extraction with solvent and water.

[0012] Specifically, the molar ratio of the aqueous solution of 4,5-dicyanimidazolium, sodium trifluoromethyl sulfinate, and tert-butyl hydroperoxide is 1:(3-9):(4-10).

[0013] Specifically, the reaction temperature is 10–80°C. Preferably, the reaction temperature is 30–50°C.

[0014] Specifically, the reaction time is 1 to 12 hours.

[0015] Specifically, the concentration of tert-butyl hydroperoxide is 50% to 80%. Preferably, the concentration of tert-butyl hydroperoxide is 70%.

[0016] Specifically, the solvent can be any one or a mixture of several of methanol, dichloromethane, dioxane, and ethyl acetate.

[0017] This invention provides a method for preparing lithium 4,5-dicyano-2-trifluoromethylimidazolium, the reaction process and route of which are as follows:

[0018]

[0019] The 4,5-dicyano-2-trifluoromethylimidazolium obtained in the above steps was added to a suspension of lithium salt and water, and the mixture was stirred, accompanied by the generation of a large number of bubbles. Activated carbon was added for decolorization. After decolorization, the activated carbon was removed by filtration, and the mother liquor was evaporated to remove water. Solvent was added and the excess lithium salt was removed by filtration. The mother liquor was recrystallized multiple times, filtered, and dried to obtain lithium 4,5-dicyano-2-trifluoromethylimidazolium with high purity.

[0020] Specifically, the lithium salt is selected from any one of lithium carbonate, lithium chloride, and lithium hydroxide.

[0021] Specifically, the decolorization time of activated carbon is 6 to 12 hours, and the amount of activated carbon is 1 to 2 g.

[0022] Specifically, the solvent is selected from any one or more of acetonitrile, dimethyl carbonate, ethyl methyl carbonate, diethyl carbonate, ethyl acetate, isopropyl ether, diethyl ether, 1,4-dioxane, and ethylene glycol dimethyl ether.

[0023] The reaction mechanism and advantages of this invention are as follows:

[0024] (1) In drug synthesis, the presence of fluorine increases the stability of organic drugs, improves the lipophilicity and permeability of compounds, and reduces the generation of drug resistance. Therefore, fluorine atoms play a crucial role in modern drug design and synthesis. Fluorine atoms themselves are highly reactive and difficult to control in reactions. Therefore, the introduction of fluorine-containing groups is often used in drug synthesis and design. Among them, trifluoromethylation is one of the commonly used synthetic methods.

[0025] The structural formula of 4,5-dicyano-2-trifluoromethylimidazolium is shown in the figure:

[0026]

[0027] It can be seen that a trifluoromethyl group is present on the imidazole ring. Based on this, we propose a method for the trifluoromethylation of 4,5-dicyanimidazole. The trifluoromethylation reaction of 4,5-dicyanimidazole utilizes sodium trifluoromethyl sulfinate as the trifluoromethyl source and tert-butyl hydroperoxide as the oxidant. The reaction follows a free radical mechanism; sodium trifluoromethyl sulfinate forms a trifluoromethyl radical under the action of tert-butyl hydroperoxide, which reacts with 4,5-dicyanimidazole to achieve trifluoromethylation, generating 4,5-dicyano-2-trifluoromethylimidazole. The reaction mechanism is as follows:

[0028]

[0029] (2) Currently, the commonly used reaction raw materials are trifluoroacetic anhydride and diaminobutadione. Trifluoroacetic anhydride has a boiling point of 40°C and is highly volatile, requiring stringent production conditions. Furthermore, the product, trifluoroacetic acid, is highly corrosive, and the post-processing is complex. The sodium trifluoromethyl sulfinate used in this invention is chemically stable, non-volatile, and widely used in the field of organofluorine chemistry. Attached Figure Description

[0030] Figure 1 This is the mass spectrum of lithium 4,5-dicyano-2-trifluoromethylimidazolium of the present invention.

[0031] Figure 2 This is the carbon NMR spectrum of lithium 4,5-dicyano-2-trifluoromethylimidazolium of the present invention.

[0032] Figure 3 The nuclear magnetic resonance fluorine spectrum of lithium 4,5-dicyano-2-trifluoromethylimidazolium of this invention.

[0033] Figure 4 Infrared spectra of commercially available 4,5-dicyano-2-trifluoromethylimidazolium lithium standard samples and 4,5-dicyano-2-trifluoromethylimidazolium lithium synthesized in this invention. Detailed Implementation

[0034] The principles and features of the present invention are described below. The examples given are only for explaining the present invention and are not intended to limit the scope of the present invention.

[0035] Figure 1 This is the mass spectrum of lithium 4,5-dicyano-2-trifluoromethylimidazolium of the present invention, obtained by... Figure 1 The presence of a molecular ion peak with a mass-to-charge ratio m / z = 185.0098 confirms the presence of TDI in the product. - The existence of.

[0036] Example 1

[0037] A 250 mL three-necked round-bottom flask equipped with an electric stirrer, reflux condenser, and thermometer was filled with 4,5-dicyanoimidazole (12.5 mmol, 1.475 g), sodium trifluoromethanesulfonate (37.5 mmol, 5.85 g), 100 mL dichloromethane, and 40 mL ultrapure water at room temperature. A 70% tert-butyl hydrogen peroxide aqueous solution (6.8 mL, 50 mmol) was slowly added dropwise, and the mixture was heated to 30 °C and reacted for 12 h. After the reaction was complete, the mixture was extracted with dichloromethane and water by shaking. The organic phase was collected and evaporated to remove the dichloromethane, yielding crude 4,5-dicyano-2-trifluoromethylimidazole.

[0038] The 4,5-dicyano-2-trifluoromethylimidazolium obtained in the above steps was added to a suspension of 0.8 g of lithium carbonate and 200 ml of water, and the mixture was stirred, accompanied by the generation of a large number of bubbles. 1 g of activated carbon was added for decolorization for 12 h, and the activated carbon was removed by filtration. Water was removed from the mother liquor by rotary evaporation, and acetonitrile was added and filtered to remove lithium carbonate. The mother liquor was recrystallized multiple times, filtered, and dried to obtain 0.6 g of relatively pure lithium 4,5-dicyano-2-trifluoromethylimidazolium, with a yield of 25%.

[0039] Example 2

[0040] A 250 mL three-necked round-bottom flask equipped with an electric stirrer, reflux condenser, and thermometer was used. At room temperature, 4,5-dicyanoimidazole (12.5 mmol, 1.475 g), sodium trifluoromethanesulfonate (112.5 mmol, 17.55 g), 100 mL of dimethyl sulfoxide, and 40 mL of ultrapure water were added. A 70% tert-butyl hydrogen peroxide aqueous solution (10.2 mL, 75 mmol) was slowly added dropwise, and the mixture was heated to 30 °C and reacted for 12 h. After the reaction was complete, the mixture was extracted with dichloromethane and water by shaking. The organic phase was collected, and the dichloromethane was removed by evaporation to obtain crude 4,5-dicyano-2-trifluoromethylimidazole.

[0041] The 4,5-dicyano-2-trifluoromethylimidazolium obtained in the above steps was added to a suspension of 0.8 g of lithium carbonate and 200 ml of water, and the mixture was stirred, accompanied by the generation of a large number of bubbles. 1 g of activated carbon was added for decolorization for 12 h, and the activated carbon was removed by filtration. Water was removed from the mother liquor by rotary evaporation, and lithium carbonate was removed by acetonitrile filtration. The mother liquor was recrystallized multiple times, filtered, and dried to obtain 0.84 g of relatively pure lithium 4,5-dicyano-2-trifluoromethylimidazolium, with a yield of 35%.

[0042] Example 3

[0043] A 250 mL three-necked round-bottom flask equipped with an electric stirrer, reflux condenser, and thermometer was used. At room temperature, 4,5-dicyanoimidazole (12.5 mmol, 1.475 g), sodium trifluoromethanesulfonate (7.5 mmol, 11.7 g), 100 mL of dichloromethane, and 40 mL of ultrapure water were added. A 70% tert-butyl hydrogen peroxide aqueous solution (13.6 mL, 100 mmol) was slowly added dropwise, and the mixture was heated to 30 °C and reacted for 12 h. After the reaction was complete, the mixture was extracted with dichloromethane and water by shaking. The organic phase was collected, and the dichloromethane was removed by evaporation to obtain crude 4,5-dicyano-2-trifluoromethylimidazole.

[0044] The 4,5-dicyano-2-trifluoromethylimidazolium obtained in the above steps was added to a suspension of 0.8 g of lithium carbonate and 200 ml of water, and the mixture was stirred, accompanied by the generation of a large number of bubbles. 1 g of activated carbon was added for decolorization for 12 h, and the activated carbon was removed by filtration. Water was removed from the mother liquor by rotary evaporation, and lithium carbonate was removed by acetonitrile filtration. The mother liquor was recrystallized multiple times, filtered, and dried to obtain 1.15 g of relatively pure lithium 4,5-dicyano-2-trifluoromethylimidazolium, with a yield of 48%.

[0045] Example 4

[0046] A 250 mL three-necked round-bottom flask equipped with an electric stirrer, reflux condenser, and thermometer was used. At room temperature, 4,5-dicyanoimidazole (12.5 mmol, 1.475 g), sodium trifluoromethanesulfonate (7.5 mmol, 11.7 g), 100 mL of dichloromethane, and 40 mL of ultrapure water were added. A 70% tert-butyl hydrogen peroxide aqueous solution (17 mL, 125 mmol) was slowly added dropwise, and the mixture was heated to 30 °C and reacted for 12 h. After the reaction was complete, the mixture was extracted with dichloromethane and water by shaking. The organic phase was collected, and the dichloromethane was removed by evaporation to obtain crude 4,5-dicyano-2-trifluoromethylimidazole.

[0047] The 4,5-dicyano-2-trifluoromethylimidazolium obtained in the above steps was added to a suspension of 0.8 g of lithium carbonate and 200 ml of water, and stirred, accompanied by the generation of a large number of bubbles. 1 g of activated carbon was added for decolorization for 12 h, and the activated carbon was removed by filtration. Water was removed from the mother liquor by rotary evaporation, and lithium carbonate was removed by acetonitrile filtration. The mother liquor was recrystallized multiple times, filtered, and dried to obtain 0.96 g of relatively pure lithium 4,5-dicyano-2-trifluoromethylimidazolium, with a yield of 40%.

[0048] Example 5

[0049] A 250 mL three-necked round-bottom flask equipped with an electric stirrer, reflux condenser, and thermometer was filled with 4,5-dicyanoimidazole (12.5 mmol, 1.475 g), sodium trifluoromethanesulfonate (7.5 mmol, 11.7 g), 100 mL dichloromethane, and 40 mL ultrapure water at room temperature. A 70% tert-butyl hydrogen peroxide aqueous solution (13.6 mL, 100 mmol) was slowly added dropwise, and the mixture was heated to 10 °C and reacted for 12 h. After the reaction was complete, the mixture was extracted with dichloromethane and water by shaking. The organic phase was collected and evaporated to remove the dichloromethane, yielding crude 4,5-dicyano-2-trifluoromethylimidazole.

[0050] The 4,5-dicyano-2-trifluoromethylimidazolium obtained in the above steps was added to a suspension of 0.8 g of lithium carbonate and 200 ml of water, and stirred, accompanied by the generation of a large number of bubbles. 1 g of activated carbon was added for decolorization for 12 h, and the activated carbon was removed by filtration. Water was removed from the mother liquor by rotary evaporation, and lithium carbonate was removed by acetonitrile filtration. The mother liquor was recrystallized multiple times, filtered, and dried to obtain 0.38 g of relatively pure lithium 4,5-dicyano-2-trifluoromethylimidazolium, with a yield of 16%.

[0051] Example 6

[0052] A 250 mL three-necked round-bottom flask equipped with an electric stirrer, reflux condenser, and thermometer was used. At room temperature, 4,5-dicyanoimidazole (12.5 mmol, 1.475 g), sodium trifluoromethanesulfonate (7.5 mmol, 11.7 g), 100 mL of dichloromethane, and 40 mL of ultrapure water were added. A 70% tert-butyl hydrogen peroxide aqueous solution (13.6 mL, 100 mmol) was slowly added dropwise, and the mixture was heated to 50 °C and reacted for 12 h. After the reaction was complete, the mixture was extracted with dichloromethane and water by shaking. The organic phase was collected, and the dichloromethane was removed by evaporation to obtain crude 4,5-dicyano-2-trifluoromethylimidazole.

[0053] The 4,5-dicyano-2-trifluoromethylimidazolium obtained in the above steps was added to a suspension of 0.8 g of lithium carbonate and 200 ml of water, and stirred, accompanied by the generation of a large number of bubbles. 1 g of activated carbon was added for decolorization for 12 h, and the activated carbon was removed by filtration. Water was removed from the mother liquor by rotary evaporation, and lithium carbonate was removed by acetonitrile filtration. The mother liquor was recrystallized multiple times, filtered, and dried to obtain 1.08 g of relatively pure lithium 4,5-dicyano-2-trifluoromethylimidazolium, with a yield of 45%.

[0054] Example 7

[0055] A 250 mL three-necked round-bottom flask equipped with an electric stirrer, reflux condenser, and thermometer was used. At room temperature, 12.5 mmol (1.475 g) of 4,5-dicyanoimidazole, 7.5 mmol (11.7 g) of sodium trifluoromethanesulfonate, 100 mL of ethyl acetate, and 40 mL of ultrapure water were added. 13.6 mL (100 mmol) of 70% tert-butyl hydroperoxide solution was slowly added dropwise, and the mixture was heated to 50 °C and reacted for 12 h. After the reaction was complete, the mixture was extracted with ethyl acetate and water by shaking. The organic phase was collected, and the ethyl acetate was removed by evaporation to obtain crude 4,5-dicyano-2-trifluoromethylimidazole.

[0056] The 4,5-dicyano-2-trifluoromethylimidazolium obtained in the above steps was added to a suspension of 0.8 g of lithium carbonate and 200 ml of water, and stirred, accompanied by the generation of a large number of bubbles. 1 g of activated carbon was added for decolorization for 12 h, and the activated carbon was removed by filtration. Water was removed from the mother liquor by rotary evaporation, and lithium carbonate was removed by acetonitrile filtration. The mother liquor was recrystallized multiple times, filtered, and dried to obtain 0.74 g of relatively pure lithium 4,5-dicyano-2-trifluoromethylimidazolium, with a yield of 31%.

[0057] Example 8

[0058] A 250 mL three-necked round-bottom flask equipped with an electric stirrer, reflux condenser, and thermometer was used to add 4,5-dicyanoimidazole (12.5 mmol, 1.475 g), sodium trifluoromethanesulfonate (7.5 mmol, 11.7 g), 100 mL of 1,4-dioxane, and 40 mL of ultrapure water at room temperature. 70% tert-butyl hydrogen peroxide aqueous solution (13.6 mL, 100 mmol) was slowly added dropwise, and the mixture was heated to 80 °C and reacted for 12 h. After the reaction was complete, 1,4-dioxane and water were removed by rotary evaporation to obtain crude 4,5-dicyano-2-trifluoromethylimidazole.

[0059] The 4,5-dicyano-2-trifluoromethylimidazolium obtained in the above steps was added to a suspension of 0.8 g of lithium carbonate and 200 ml of water, and stirred, accompanied by the generation of a large number of bubbles. 1 g of activated carbon was added for decolorization for 12 h, and the activated carbon was removed by filtration. Water was removed from the mother liquor by rotary evaporation, and lithium carbonate was removed by acetonitrile filtration. The mother liquor was recrystallized multiple times, filtered, and dried to obtain 0.77 g of relatively pure lithium 4,5-dicyano-2-trifluoromethylimidazolium, with a yield of 32%.

[0060] Example 9

[0061] A 250 mL three-necked round-bottom flask equipped with an electric stirrer, reflux condenser, and thermometer was used to add 4,5-dicyanoimidazole (12.5 mmol, 1.475 g), sodium trifluoromethanesulfonate (7.5 mmol, 11.7 g), 100 mL of methanol, and 40 mL of ultrapure water at room temperature. A 70% tert-butyl hydrogen peroxide aqueous solution (13.6 mL, 100 mmol) was slowly added dropwise, and the mixture was heated to 50 °C and reacted for 12 h. After the reaction was complete, methanol and water were removed by rotary evaporation to obtain crude 4,5-dicyano-2-trifluoromethylimidazole.

[0062] The 4,5-dicyano-2-trifluoromethylimidazolium obtained in the above steps was added to a suspension of 0.8 g of lithium carbonate and 200 ml of water, and stirred, accompanied by the generation of a large number of bubbles. 1 g of activated carbon was added for decolorization for 12 h, and the activated carbon was removed by filtration. Water was removed from the mother liquor by rotary evaporation, and lithium carbonate was removed by acetonitrile filtration. The mother liquor was recrystallized multiple times, filtered, and dried to obtain 0.7 g of relatively pure lithium 4,5-dicyano-2-trifluoromethylimidazolium, with a yield of 29%.

[0063] Example 10

[0064] A 250 mL three-necked round-bottom flask equipped with an electric stirrer, reflux condenser, and thermometer was used. At room temperature, 4,5-dicyanoimidazole (12.5 mmol, 1.475 g), sodium trifluoromethanesulfonate (7.5 mmol, 11.7 g), 100 mL of dichloromethane, and 40 mL of ultrapure water were added. A 70% tert-butyl hydrogen peroxide aqueous solution (13.6 mL, 100 mmol) was slowly added dropwise, and the mixture was heated to 30 °C and reacted for 6 h. After the reaction was complete, the mixture was extracted with dichloromethane and water by shaking. The organic phase was collected, and the dichloromethane was removed by evaporation to obtain crude 4,5-dicyano-2-trifluoromethylimidazole.

[0065] The 4,5-dicyano-2-trifluoromethylimidazolium obtained in the above steps was added to a suspension of 0.8 g of lithium carbonate and 200 ml of water, and the mixture was stirred, accompanied by the generation of a large number of bubbles. 1 g of activated carbon was added for decolorization for 12 h, and the activated carbon was removed by filtration. Water was removed from the mother liquor by rotary evaporation, and lithium carbonate was removed by acetonitrile filtration. The mother liquor was recrystallized multiple times, filtered, and dried to obtain 0.48 g of relatively pure lithium 4,5-dicyano-2-trifluoromethylimidazolium, with a yield of 20%.

[0066] Example 11

[0067] A 250 mL three-necked round-bottom flask equipped with an electric stirrer, reflux condenser, and thermometer was filled with 4,5-dicyanoimidazole (12.5 mmol, 1.475 g), sodium trifluoromethanesulfonate (7.5 mmol, 11.7 g), 100 mL dichloromethane, and 40 mL ultrapure water at room temperature. An 80% tert-butyl hydrogen peroxide aqueous solution (11.9 mL, 100 mmol) was slowly added dropwise, and the mixture was heated to 30 °C and reacted for 12 h. After the reaction was complete, the mixture was extracted with dichloromethane and water by shaking. The organic phase was collected and evaporated to remove the dichloromethane, yielding crude 4,5-dicyano-2-trifluoromethylimidazole.

[0068] The 4,5-dicyano-2-trifluoromethylimidazolium obtained in the above steps was added to a suspension of 0.8 g of lithium carbonate and 200 ml of water, and stirred, accompanied by the generation of a large number of bubbles. 1 g of activated carbon was added for decolorization for 12 h, and the activated carbon was removed by filtration. Water was removed from the mother liquor by rotary evaporation, and lithium carbonate was removed by acetonitrile filtration. The mother liquor was recrystallized multiple times, filtered, and dried to obtain 0.91 g of relatively pure lithium 4,5-dicyano-2-trifluoromethylimidazolium, with a yield of 38%.

[0069] Example 12

[0070] A 250 mL three-necked round-bottom flask equipped with an electric stirrer, reflux condenser, and thermometer was filled with 4,5-dicyanoimidazole (12.5 mmol, 1.475 g), sodium trifluoromethanesulfonate (7.5 mmol, 11.7 g), 100 mL dichloromethane, and 40 mL ultrapure water at room temperature. A 50% tert-butyl hydrogen peroxide aqueous solution (19.0 mL, 100 mmol) was slowly added dropwise, and the mixture was heated to 30 °C and reacted for 12 h. After the reaction was complete, the mixture was extracted with dichloromethane and water by shaking. The organic phase was collected and evaporated to remove the dichloromethane, yielding crude 4,5-dicyano-2-trifluoromethylimidazole.

[0071] The 4,5-dicyano-2-trifluoromethylimidazolium obtained in the above steps was added to a suspension of 0.8 g of lithium carbonate and 200 ml of water, and stirred, accompanied by the generation of a large number of bubbles. 1 g of activated carbon was added for decolorization for 12 h, and the activated carbon was removed by filtration. Water was removed from the mother liquor by rotary evaporation, and lithium carbonate was removed by acetonitrile filtration. The mother liquor was recrystallized multiple times, filtered, and dried to obtain 0.96 g of relatively pure lithium 4,5-dicyano-2-trifluoromethylimidazolium, with a yield of 40%.

[0072] Example 13

[0073] A 250 mL three-necked round-bottom flask equipped with an electric stirrer, reflux condenser, and thermometer was used. At room temperature, 4,5-dicyanoimidazole (12.5 mmol, 1.475 g), sodium trifluoromethanesulfonate (7.5 mmol, 11.7 g), 100 mL of dichloromethane, and 40 mL of ultrapure water were added. A 70% tert-butyl hydrogen peroxide aqueous solution (13.6 mL, 100 mmol) was slowly added dropwise, and the mixture was heated to 30 °C and reacted for 12 h. After the reaction was complete, the mixture was extracted with dichloromethane and water by shaking. The organic phase was collected, and the dichloromethane was removed by evaporation to obtain crude 4,5-dicyano-2-trifluoromethylimidazole.

[0074] The 4,5-dicyano-2-trifluoromethylimidazolium obtained in the above steps was added to a suspension of 0.8 g of lithium carbonate and 200 ml of water, and stirred, accompanied by the generation of a large number of bubbles. 2 g of activated carbon was added for decolorization for 12 h, and the activated carbon was removed by filtration. Water was removed from the mother liquor by rotary evaporation, and lithium carbonate was removed by acetonitrile filtration. The mother liquor was recrystallized multiple times, filtered, and dried to obtain 0.72 g of relatively pure lithium 4,5-dicyano-2-trifluoromethylimidazolium, with a yield of 30%.

[0075] Example 14

[0076] A 250 mL three-necked round-bottom flask equipped with an electric stirrer, reflux condenser, and thermometer was used. At room temperature, 4,5-dicyanoimidazole (12.5 mmol, 1.475 g), sodium trifluoromethanesulfonate (7.5 mmol, 11.7 g), 100 mL of dichloromethane, and 40 mL of ultrapure water were added. A 70% tert-butyl hydrogen peroxide aqueous solution (13.6 mL, 100 mmol) was slowly added dropwise, and the mixture was heated to 30 °C and reacted for 12 h. After the reaction was complete, the mixture was extracted with dichloromethane and water by shaking. The organic phase was collected, and the dichloromethane was removed by evaporation to obtain crude 4,5-dicyano-2-trifluoromethylimidazole.

[0077] The 4,5-dicyano-2-trifluoromethylimidazolium obtained in the above steps was added to a suspension of 0.3 g of lithium hydroxide and 200 ml of water, and stirred, accompanied by the generation of a large number of bubbles. 1 g of activated carbon was added for decolorization for 12 h, and the activated carbon was removed by filtration. Water was removed from the mother liquor by rotary evaporation, and lithium carbonate was removed by acetonitrile filtration. The mother liquor was recrystallized multiple times, filtered, and dried to obtain 1.06 g of relatively pure lithium 4,5-dicyano-2-trifluoromethylimidazolium, with a yield of 44%.

[0078] Example 15

[0079] A 250 mL three-necked round-bottom flask equipped with an electric stirrer, reflux condenser, and thermometer was used. At room temperature, 4,5-dicyanoimidazole (12.5 mmol, 1.475 g), sodium trifluoromethanesulfonate (7.5 mmol, 11.7 g), 100 mL of dichloromethane, and 40 mL of ultrapure water were added. A 70% tert-butyl hydrogen peroxide aqueous solution (13.6 mL, 100 mmol) was slowly added dropwise, and the mixture was heated to 30 °C and reacted for 12 h. After the reaction was complete, the mixture was extracted with dichloromethane and water by shaking. The organic phase was collected, and the dichloromethane was removed by evaporation to obtain crude 4,5-dicyano-2-trifluoromethylimidazole.

[0080] The 4,5-dicyano-2-trifluoromethylimidazolium obtained in the above steps was added to a suspension of 0.8 g of lithium carbonate and 200 ml of water, and the mixture was stirred, accompanied by the generation of a large number of bubbles. 1 g of activated carbon was added for decolorization for 12 h, and the activated carbon was removed by filtration. Water was removed from the mother liquor by rotary evaporation, and lithium carbonate was removed by filtration after adding ethylene glycol dimethyl ether. The mother liquor was recrystallized multiple times, filtered, and dried to obtain 0.91 g of relatively pure lithium 4,5-dicyano-2-trifluoromethylimidazolium, with a yield of 38%.

[0081] Example 16

[0082] A 250 mL three-necked round-bottom flask equipped with an electric stirrer, reflux condenser, and thermometer was used. At room temperature, 4,5-dicyanoimidazole (12.5 mmol, 1.475 g), sodium trifluoromethanesulfonate (7.5 mmol, 11.7 g), 100 mL of dichloromethane, and 40 mL of ultrapure water were added. A 70% tert-butyl hydrogen peroxide aqueous solution (13.6 mL, 100 mmol) was slowly added dropwise, and the mixture was heated to 30 °C and reacted for 12 h. After the reaction was complete, the mixture was extracted with dichloromethane and water by shaking. The organic phase was collected, and the dichloromethane was removed by evaporation to obtain crude 4,5-dicyano-2-trifluoromethylimidazole.

[0083] The 4,5-dicyano-2-trifluoromethylimidazolium obtained in the above steps was added to a suspension of 0.8 g of lithium carbonate and 200 ml of water, and stirred, accompanied by the generation of a large number of bubbles. 1 g of activated carbon was added for decolorization for 12 h, and the activated carbon was removed by filtration. Water was removed from the mother liquor by rotary evaporation, and dimethyl carbonate was added and filtered to remove lithium carbonate. The mother liquor was recrystallized multiple times, filtered, and dried to obtain 1.00 g of relatively pure lithium 4,5-dicyano-2-trifluoromethylimidazolium, with a yield of 42%.

[0084] Example 17

[0085] A 250 mL three-necked round-bottom flask equipped with an electric stirrer, reflux condenser, and thermometer was used. At room temperature, 4,5-dicyanoimidazole (12.5 mmol, 1.475 g), sodium trifluoromethanesulfonate (7.5 mmol, 11.7 g), 100 mL of dichloromethane, and 40 mL of ultrapure water were added. A 70% tert-butyl hydrogen peroxide aqueous solution (13.6 mL, 100 mmol) was slowly added dropwise, and the mixture was heated to 30 °C and reacted for 12 h. After the reaction was complete, the mixture was extracted with dichloromethane and water by shaking. The organic phase was collected, and the dichloromethane was removed by evaporation to obtain crude 4,5-dicyano-2-trifluoromethylimidazole.

[0086] The 4,5-dicyano-2-trifluoromethylimidazolium obtained in the above steps was added to a suspension of 0.8 g of lithium carbonate and 200 ml of water, and the mixture was stirred, accompanied by the generation of a large number of bubbles. 1 g of activated carbon was added for decolorization for 6 hours, and the activated carbon was removed by filtration. Water was removed from the mother liquor by rotary evaporation, and acetonitrile was added and filtered to remove lithium carbonate. The mother liquor was recrystallized multiple times, filtered, and dried to obtain 0.96 g of relatively pure lithium 4,5-dicyano-2-trifluoromethylimidazolium, with a yield of 40%.

[0087] Furthermore, the specific concentration parameters of the embodiments of the present invention are shown in Table 1:

[0088] Table 1: Specific Concentration Parameters for Examples

[0089]

[0090] In summary, Figure 2This is the carbon NMR spectrum of lithium 4,5-dicyano-2-trifluoromethylimidazolium according to the present invention. Figure 2 It can be seen that, 13 C NMR (600MHz, Acetonitrile-d3, ppm): δ=115.88, 120.23, 122.37, 148.64. Figure 3 This is the NMR fluorine spectrum of lithium 4,5-dicyano-2-trifluoromethylimidazolium according to the present invention. (From...) Figure 3 It can be seen that, 19 F NMR (600MHz, Acetonitrile-d3, ppm): δ=-64.19 (s, –CF3). Figure 4 Infrared spectra of commercially available 4,5-dicyano-2-trifluoromethylimidazolium lithium standard samples and synthesized 4,5-dicyano-2-trifluoromethylimidazolium lithium are shown for this invention. Figure 4 The infrared spectrum shows a depth of 2243 cm⁻¹ -1 Absorption peak of the symmetric stretching vibration of the -C≡N bond at 1500 cm⁻¹; -1 Absorption peak of stretching vibration of C-C bond at 1321 cm⁻¹. -1 The peak at 1189 cm⁻¹ is attributed to the -CN asymmetric stretching vibration absorption peak on the imidazole ring. -1 and 1141cm -1 The absorption peak at 1002 cm⁻¹ is attributed to the stretching vibration of the CF bond. -1 The absorption peak at the position is attributed to the -NCN bending vibration on the imidazole ring, indicating that lithium 2-trifluoromethyl-4,5-dicyanimidazolium has been successfully prepared.

[0091] As can be seen from the embodiments of this invention and Table 1, the synthetic route mentioned in this invention represents a significant breakthrough compared to previous methods, synthesizing 4,5-dicyano-2-trifluoromethylimidazole from the perspective of trifluoromethylation. The reaction process is safer and the conditions are milder, providing a new approach for industrial production. This method breaks through the conventional approach of using diaminobutenonitrile, trifluoroacetic anhydride, and trifluoroacetic acid as raw materials, synthesizing 4,5-dicyano-2-trifluoromethylimidazole from the perspective of trifluoromethylation. It offers higher safety and milder reaction conditions, which is beneficial for large-scale industrial production.

Claims

1. A method for preparing lithium 4,5-dicyano-2-trifluoromethylimidazolium, characterized in that, Includes the following steps: Under the conditions of adding solvent and water to 4,5-dicyano-2-trifluoromethylimidazolium and sodium trifluoromethylsulfinate, an aqueous solution of tert-butyl hydroperoxide was slowly added and vigorously stirred. The reaction was heated for a certain period of time to obtain 4,5-dicyano-2-trifluoromethylimidazolium. After the reaction, the crude product 4,5-dicyano-2-trifluoromethylimidazolium was obtained by multiple extractions with solvent I and water. The crude product 4,5-dicyano-2-trifluoromethylimidazolium was added to a suspension of lithium salt and water, stirred and accompanied by the generation of a large number of bubbles. Activated carbon was added for decolorization. After decolorization, the activated carbon was removed by filtration. The mother liquor was evaporated to remove water. Solvent II was added and filtered to remove excess lithium salt. The mother liquor was recrystallized multiple times, filtered and dried to obtain high-purity lithium 4,5-dicyano-2-trifluoromethylimidazolium. The molar ratio of aqueous solutions of 4,5-dicyanimidazole, sodium trifluoromethyl sulfinate, and tert-butyl hydroperoxide is 1:(3~9):(4~10). The reaction temperature is 30 ~ 50 ℃; The reaction time is 1 to 12 hours. The concentration of tert-butyl hydroperoxide is 70%; Solvent I is selected from any one or a mixture of several of methanol, dichloromethane, dioxane, and ethyl acetate; The synthetic route for lithium 4,5-dicyano-2-trifluoromethylimidazolium is as follows: ； The lithium salt is selected from any one of lithium carbonate, lithium chloride, and lithium hydroxide; Solvent II is selected from any one or more of acetonitrile, dimethyl carbonate, ethyl methyl carbonate, diethyl carbonate, ethyl acetate, isopropyl ether, diethyl ether, 1,4-dioxane, and ethylene glycol dimethyl ether; The decolorization time for activated carbon is 6 to 12 hours.

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