Purification method of 2-(fluoroalkyl or fluoroalkoxy)-4,5-dicyanoimidazole

Abstract

The present invention relates to a process for purifying a compound of the following formula (III): wherein Rf is a fluorinated alkyl or fluorinated alkoxy group containing 1-5 carbon atoms, the process comprising the following steps: a) heating a composition comprising the compound of the formula (III) to a temperature T1 in an organic solvent S3 until the compound of the formula (III) has dissolved; b) cooling to an intermediate temperature T2 between 23°C and the temperature T1, resulting in a two-phase composition comprising: a phase P1 comprising the compound of the formula (III); a phase P2; c) separating phases P1 and P2 at a temperature T2; d) cooling phase P1 to a temperature T3 until crystals of the compound of the formula (III) have formed.

Description

Technical Field

[0001] The present invention relates to a process for purifying imidazole.

[0002] The present invention also relates to a process for preparing imidazole lithium salt. Background Art

[0003] Lithium-ion batteries include at least a negative electrode, a positive electrode, a separator and an electrolyte. The electrolyte consists of a lithium salt dissolved in a solvent, which is usually a mixture of organic carbonates to have a good compromise between viscosity and dielectric constant.

[0004] The most widely used of the salts is lithium hexafluorophosphate (LiPF6), which has many of the desirable qualities but has the disadvantage of degrading in the form of hydrofluoric acid gas. This raises safety issues, particularly where lithium ion batteries are used for passenger vehicles.

[0005] Therefore, other salts have been developed for providing electrolytes for Li-ion batteries, and in particular LiTDI (1-trifluoromethyl-4,5-dicarbonitrile-imidazole lithium) and LiPDI (1-pentafluoroethyl-4,5-dicarbonitrile-imidazole lithium), as described in WO 2010 / 023413. These salts have the advantages of containing fewer fluorine atoms and containing strong carbon-fluorine bonds instead of the weaker phosphorus-fluorine bonds in LiPF6. In addition, these salts have very good conductivity of about 6 mS / cm and very good dissociation between imidazolate anions and lithium cations.

[0006] WO 2010 / 023413 proposes several synthetic routes for the preparation of these pentacyclic anions, one of which consists of condensing diaminomaleonitrile (DAMN) with an acid derivative such as a fluorinated anhydride followed by a proton / lithium exchange. The condensation is carried out in a single step.

[0007] WO 2015 / 49435 describes the preparation of fluoroalkyl-4,5-dicyanoimidazolium salts in a purity compatible with use in batteries or in ionic liquids. The process involves the use of activated carbon to purify the pentacyclic anionic salts. Currently, the use of activated carbon is a cumbersome operation and is prone to introducing ions such as Ca into the medium that can lead to a decrease in battery performance. 2+ or K + Furthermore, activated carbons generally require extensive washing before use, which is an expensive limitation. Finally, to obtain the desired purity and acceptable Hazen color, at least one recrystallization step is required.

[0008] Therefore, there is a need for a new process for preparing pentacyclic anionic salts that can at least partially overcome at least one of the aforementioned drawbacks. Summary of the invention

[0009] Purification process

[0010] The present invention relates to a process for purifying a compound of the following formula (III):

[0011]

[0012] Wherein Rf is a fluoroalkyl or fluoroalkoxy group containing 1 to 5 carbon atoms, and the process comprises the following steps:

[0013] a. the step of heating the composition comprising the compound of formula (III) in an organic solvent S3 at a temperature T1 until the compound of formula (III) has dissolved;

[0014] b. cooling to an intermediate temperature T2 between 23°C and temperature T1, resulting in a step of a two-phase composition comprising:

[0015] - phase P1, comprising said compound of formula (III);

[0016] - Phase P2;

[0017] c. a step of separating phases P1 and P2 at a temperature T2;

[0018] d. A step of cooling phase P1 to temperature T3 until crystals of the compound of formula (III) have formed.

[0019] According to one embodiment, Rf represents CF3, CHF2, C2F5, C3F7, C2F4OCF3 or CF2OCF3, preferably CF3, C2F5 or C2F4OCF3.

[0020] Preferably, the compound of formula (III) is a compound wherein Rf represents CF3.

[0021] According to one embodiment, the present invention relates to a process for purifying a compound of the following formula (III):

[0022]

[0023] Wherein Rf is C2F4OCF3 or a fluoroalkyl or fluoroalkoxy group containing 1 to 5 carbon atoms, and the process comprises the following steps:

[0024] a. heating the composition comprising the compound of formula (III) in an organic solvent S3 having a donor number in the range of 0.1 to 10 at a temperature T1 until the compound of formula (III) has dissolved;

[0025] b. cooling to an intermediate temperature T2 between 23°C and temperature T1, resulting in a step of a two-phase composition comprising:

[0026] - phase P1, comprising said compound of formula (III);

[0027] - Phase P2;

[0028] c. a step of separating phases P1 and P2 at a temperature T2;

[0029] d. A step of cooling phase P1 to temperature T3 until crystals of the compound of formula (III) have formed.

[0030] Heating step a)

[0031] The organic solvent S3 preferably has a donor number ranging from 0.1 to 10.

[0032] The donor number of the solvent is expressed as a value -ΔH, where ΔH is the interaction enthalpy (Kcal / mol) between the solvent and antimony pentachloride (Journal of Solution Chemistry, Vol. 13, No. 9, 1984).

[0033] The organic solvent S3 is preferably selected from aromatic compounds or aliphatic or cyclic alkanes, such as toluene, benzene, xylene, cyclohexane or heptane. Preferably, the organic solvent S3 is toluene.

[0034] Temperature T1 is the temperature at which the compound of formula (III) is dissolved in the organic solvent S3.

[0035] The temperature T1 may be between 40°C and the boiling point of the organic solvent S3, preferably between 50°C and 120°C, advantageously between 60°C and 100°C. The temperature T1 is advantageously equal to 70°C.

[0036] The composition comprising the compound of formula (III) and the organic solvent S3 used in step a) can be obtained by placing the organic solvent S3 in contact with the compound of formula (III) in solid form.

[0037] Before step a), the compound of formula (III) may be in hydrated form, i.e. the compound of formula (III) may have a water content by weight of between 1% and 25%, preferably between 5% and 20% and preferentially between 10% and 16%, relative to the total weight of the compound of formula (III).

[0038] Before step a), the mass content of the compound of formula (III) in the composition comprising organic solvent S3 may range from 1% to 70% by weight, preferably from 5% to 50% by weight, and preferentially from 8% to 30% by weight, relative to the total weight of the composition.

[0039] Cooling step b)

[0040] The temperature T2 is between 23°C and the temperature T1 , preferably between 23°C and 50°C and advantageously between 30°C and 50°C.

[0041] Step b) results in a two-phase composition comprising:

[0042] - phase P1 comprising said compound of formula (III); and

[0043] -Phase P2.

[0044] Phase P1 is advantageously a liquid phase; it comprises in particular an organic solvent S3.

[0045] Phase P1 preferably comprises more than 30%, preferably more than 35% and advantageously more than 40% of the compound of formula (III) initially contained in the solution obtained at the end of step a).

[0046] Phase P1 preferably comprises from 0.5% to 70% by weight, preferably from 1% to 50% by weight, preferentially from 5% to 30% by weight, of compound of formula (III), relative to the total weight of said phase P1.

[0047] Phase P2 may comprise a content of compound of formula (III) strictly less than 45%, preferably less than 35% of the initial content of compound of formula (III) in the solution obtained at the end of step a).

[0048] Phase P2 may include impurities resulting from the process used to prepare the compound of formula (III), such as colorants and TFA.

[0049] Preferably, phase P2 has a higher density than the density of phase P1 .

[0050] Phase P2 can be separated from phase P1 , for example, by decanting followed by flushing the lower phase or pumping the upper phase.

[0051] Cooling step b)

[0052] The purification process according to the invention comprises a step of cooling phase P1 to temperature T3 until crystals of the compound of formula (III) have formed.

[0053] The temperature T3 may be between 40° C. and −30° C., preferably between 25° C. and −15° C. and even more preferentially between 10° C. and −5° C. The temperature T3 is advantageously 0° C.

[0054] The temperature T3 is advantageously the temperature at which the compound of formula (III) crystallizes in the organic solvent S3.

[0055] Steps a, b, c, d can be repeated on P2 to obtain more compound III. The number of repetitions is between 2 and 4, preferably 3.

[0056] Additional Steps

[0057] The aforementioned purification process may comprise an additional step e) of filtering off the composition obtained at the end of step d). The filtration advantageously results in the compound of formula (III) in solid form and in a filtrate.

[0058] The solid is advantageously subjected to a further drying step, preferably under a stream of nitrogen at 23° C. or more.

[0059] The aforementioned purification process advantageously allows the preparation of the compound of formula (III) in good yield and with a reduced content of impurities, in particular of reagents tending to color the product and / or TFA (trifluoroacetic acid) and / or the following amides derived from the compound of formula (III):

[0060]

[0061] The purification process advantageously allows the preparation of compounds of formula (III) with less color.

[0062] The purification process also advantageously allows obtaining the compound of formula (III) in good yield and with a reduced impurity content, in a reduced number of steps, without the need for additional expensive purification steps.

[0063] Preliminary steps

[0064] The purification process according to the present invention may comprise a step a') of contacting the compound of formula (III) with an organic solvent S3 before step a). Preferably, the organic solvent S3 is added to the compound of formula (III).

[0065] The compound of formula (III) from step a') can be obtained via a process comprising the following steps:

[0066] -x) a step of placing the compound of formula (III) in contact with water, preferably in a mass ratio of compound of formula (III) / water ranging from 1:1 to 1:4, advantageously from 1:1 to 1:2;

[0067] -y) a step of heating the composition obtained in step x) to a temperature T6 (preferably between 30° C. and 80° C., advantageously between 40° C. and 70° C.);

[0068] -z) a step of cooling the composition obtained in step y) until crystals of the compound of formula (III) have formed;

[0069] -z') a step of filtering off the crystals, and optionally drying;

[0070] -z") an optional step of washing the crystals with water, in particular at 23°C, and an optional drying step.

[0071] The compound of formula (III) of step x) can be obtained by any process for preparing a compound of formula (III), optionally carrying out a step of evaporating off the reaction solvent.

[0072] Synthesis of compounds of formula (III)

[0073] The compound of formula (III) can be obtained by the following process:

[0074] i. The step of reacting the diaminomaleonitrile of formula (I) with the compound of the following formula (II) at a temperature T4 to form a salified amide compound of formula (IVa) and / or the corresponding amine (IVb):

[0075]

[0076] Wherein Y represents a chlorine atom or a group OCORf,

[0077]

[0078] ii. dehydrating the salified amide compound of formula (IVa) and / or the corresponding amine of formula (IVb) at a temperature T5 higher than T4 to form the imidazole compound of formula (III).

[0079] The temperature T4 may range from 0 to 80°C, preferably from 10 to 50°C, more preferably from 20 to 30°C, for example about 25°C.

[0080] According to one embodiment, step (i) lasts from 1 to 12 hours, preferably from 1 to 3 hours, and / or step (ii) lasts from 1 to 12 hours, preferably from 1 to 3 hours.

[0081] According to one embodiment, the diaminomaleonitrile of formula (I) and the compound of formula (II) are dissolved in a solvent before step (i), and the solvent is preferably 1,4-dioxane.

[0082] Step (i) is preferably carried out by dissolving the reactants in solvent S1.

[0083] The solvent S1 may be selected from 1,4-dioxane, toluene, dimethylformamide and a mixture thereof, and the solvent S1 is preferably 1,4-dioxane.

[0084] The concentration of DAMN of formula (I) in the reaction medium of step (i) is preferably 0.001 to 2 mol / L, more preferably 0.1 to 1 mol / L. The molar ratio of compound (I) to compound (II) is preferably 0.25 to 1.5, more preferably 0.5 to 1.25.

[0085] The second step (ii) is carried out at a temperature T5 higher than T4. Preferably, T5 is at least 10°C, or at least 20°C, or at least 30°C, or at least 40°C, or at least 50°C, or at least 60°C, or at least 70°C higher than T4.

[0086] According to a particular embodiment, temperature T5 corresponds to the boiling point of the solvent used.

[0087] Preferably, T5 ranges from 30 to 180°C, more particularly from 60 to 150°C, more preferentially from 75 to 140°C, for example about 100 or 101°C (which corresponds to the boiling point of 1,4-dioxane).

[0088] The concentration of compound (IVa) and / or (IVb) in the reaction medium during the second step is preferably in the range of 0.001 to 2 mol / L, more preferably 0.05 to 0.75 mol / L.

[0089] Preferably, the second step (ii) is carried out immediately after the first step simply by changing the temperature of the reaction mixture by heating, without intermediate purification and advantageously without any separation step.

[0090] In the case where Y═Cl, the amide is salified by adding a carboxylic acid which also makes it possible to improve the yield of the second step by acid catalysis. The acid used is, for example, trifluoroacetic acid, acetic acid or benzoic acid, and preferably trifluoroacetic acid.

[0091] The molar ratio of compound (IVa) and / or (IVb) to the catalyst is preferably in the range of 0.5-20, more preferably 1-10.

[0092] The reaction temperature T4 can be constant throughout the first step, and the reaction temperature T5 can be constant throughout the second step, but this is not necessarily the case. For example, it is conceivable that the temperature increases throughout the reaction, or only throughout the first step. In such a case, the condition according to which T5 is greater than T4 means that the temperature throughout the second step is greater than the temperature throughout the first step, that is, the minimum temperature reached during the second step is greater than the maximum temperature reached during the first step.

[0093] In order to convert the first step into the second step and to carry out the required temperature change, a transition period may be necessary. The transition period preferably has a duration of less than 1 hour, such as less than 30 minutes, such as less than 20 minutes, such as less than 10 minutes, such as less than 5 minutes.

[0094] The aforementioned steps i) and ii) may be followed by a step of distilling the azeotropic mixture of solvent S1 / water, in particular at a temperature ranging from 40°C to 90°C.

[0095] Process for preparing lithium imidazole

[0096] The present invention also relates to a process for preparing a lithium imidazole compound of formula (V):

[0097] (V)

[0098] Wherein Rf is a fluoroalkyl or fluoroalkoxy group containing 1 to 5 carbon atoms, and the process comprises:

[0099] -1) purifying the compound of formula (III) according to the aforementioned process; and

[0100] -2) reacting the compound of formula (III) with a lithiated base.

[0101] According to one embodiment, Rf represents CF3, CHF2, C2F5, C3F7, C2F4OCF3 or CF2OCF3, preferably CF3, C2F5 or C2F4OCF3.

[0102] According to one embodiment, the present invention relates to a process for preparing a lithium imidazole compound of formula (V), wherein Rf is a fluoroalkyl or fluoroalkoxy group containing 1 to 5 carbon atoms or C2F4OCF3, the process comprising:

[0103] -1) purifying the compound of formula (III) according to the aforementioned process; and

[0104] -2) reacting the compound of formula (III) with a lithiated base.

[0105] Preferably, the compound of formula (V) is a compound wherein Rf represents CF3.

[0106] The lithiating base may be selected from lithium hydride, lithium carbonate, lithium hydroxide and mixtures thereof. Preferably, the lithiating base is lithium carbonate.

[0107] The lithiated base may be in solid form or in the form of an aqueous or organic composition (eg a suspension or solution). The concentration of the lithiated base in the aqueous or organic composition is preferably in the range of 0.01 to 10 mol / L, more preferably 0.1 to 5 mol / L.

[0108] The compound of formula (III) obtained at the end of the purification process as described above may be in solid form or dissolved in an organic solvent. The concentration of compound (III) in the organic phase may preferably be in the range of 0.01 to 5 mol / L, more preferentially 0.1 to 3 mol / L.

[0109] Preferably, before step 2), the compound of formula (III) is dissolved in an organic solvent S4, preferably an organic solvent S4 having a donor number ranging from 1 to 70, advantageously from 5 to 65. As solvent S4, esters, nitriles or ethers may be mentioned in particular. Advantageously, the organic solvent S4 is selected from methyl acetate, ethyl acetate, butyl acetate, acetonitrile, propionitrile, isobutyronitrile, glutaronitrile, dioxane and tetrahydrofuran, and even more advantageously acetonitrile.

[0110] Preferably, step 2) comprises adding a composition comprising a compound of formula (III) to an aqueous composition of a lithiated base.

[0111] The reaction of step 2) can be carried out at a temperature between 0°C and 100°C, preferably between 10°C and 50°C and even more preferentially between 20°C and 30°C.

[0112] The duration of step 2) may be between 1 hour and 72 hours, preferably between 3 hours and 24 hours, even more preferentially between 6 hours and 18 hours.

[0113] The process may comprise the further step of evaporating off the water and the solvent, preferably under vacuum. In case an organic solvent is present, water is preferentially removed by azeotropic distillation.

[0114] The process may comprise the additional step of recrystallizing the compound of formula (V) in an organic solvent S4 as defined above.

[0115] The use of the purification process according to the invention advantageously makes it possible to prepare compounds of formula (V) and in particular LiTDI in improved yield and in particular in a reduced number of steps.

[0116] The purification process according to the invention advantageously results in a reduced impurity content, such as reduced or even zero amide-LiTDI, Ca 2+ , K + , TFA-Li... and less colored compounds of formula (V), and especially LiTDI.

[0117] The purification process according to the invention advantageously allows the preparation of compounds of formula (V) and in particular LiTDI with improved purity without the use of many additional purification steps. Such purity advantageously enables the use of compounds of formula (V) in batteries or ionic liquids.

[0118] In the context of the present invention, the term "between x and y" or "ranging from x to y" means a range including the limits x and y. For example, a temperature "between -20 and 80°C" especially includes the values ​​-20°C and 80°C.

[0119] The invention is illustrated by the following examples without, however, being restricted thereto. Example

[0120] The Hazen color is measured as follows: According to the Hazen standard, for (I) solutions at a concentration of 1 mol / L in a solvent that does not absorb in the visible region, on a Hach Lico 150 spectrophotometer, in a cell with a diameter of 11 mm. When a solution gives a value of less than 10 Hazen, the light path is increased for greater accuracy by using a 50 mm cuvette. The Hazen values ​​reported in the examples are the average of three measurements made on the same solution.

[0121] For the examples, the fluorine species were 19 F. 1 H and 13 The NMR analysis conditions for C NMR are as follows:

[0122] equipment NMR spectroscopy and quantification were performed on a Brüker AV 400 spectrometer. 13 C's 100.62MHz and for 19 F's 376.47MHz in 5mm BBFO + type probe.

[0123] sampling : The sample was dissolved in DMSO-d6 (about 30 mg in 0.6 ml). In the case of detection of fluoride or addition of LiF (which serves to check for the presence of undesired fluoride), the solvent was D2O due to the insolubility of LiF in DMSO.

[0124] Quantification : 19 Relative quantification in F NMR is performed by integrating the signal of the fluorinated species weighted by the amount of fluorine attributed to the signal, a method well known to those skilled in the art. According to methods well known to those skilled in the art, 19 Absolute quantification in F NMR is performed by dosing α,α,α-trifluorotoluene (TFT, Aldrich) into the tube containing the compound and integrating the signal of the fluorinated species to be analyzed compared to the CF3 signal of the internal standard. The limit of quantification of species such as LiTDI at a frequency of 376.47 MHz and the selected probe is about 50 ppm level.

[0125] Example 1 :Process for preparing HTDI

[0126] 20 kg of 98% pure DAMN (diaminomaleonitrile) in 60 kg of 1,4-dioxane are placed in a 100 liter glass reactor equipped with a condenser, a reactant introduction pump and a temperature port at room temperature (23°C). The suspension is stirred while 40.4 kg of 99% pure trifluoroacetic anhydride (TFAA) are introduced by means of the pump; the introduction rate of TFAA is controlled so that the reaction medium is kept at a temperature below 30°C (reactor wall temperature is about 12°C). The suspension quickly turns into a brown solution. When all the trifluoroacetic anhydride has been introduced, the medium is stirred for 15 minutes and then the temperature of the reaction medium is increased to the reflux point of dioxane (105°C) (reactor water temperature: maximum 130°C), maintaining this temperature so that the complete operation lasts for 30 minutes under reflux.

[0127] Then, the jacket temperature was adjusted to 100°C and the pressure in the reactor was gradually reduced so that the azeotropic mixture of dioxane / water was distilled out at 70°C. While continuing the distillation, four additions of 10 kg of dioxane were performed at this temperature. The pressure was adjusted to ensure that the solvent was distilled at 60°C. The medium was concentrated at 60°C until a brown oil was obtained. The oil was then blended in water at a water / oil mass ratio of 1:1. The whole was stirred and heated at 60°C until a uniform brown paste was obtained, and then cooled. The crystals obtained were then filtered out and subsequently resuspended in water at room temperature (23°C) and then filtered out. This operation was performed three times in total.

[0128] The solid was partially dried overnight at room temperature (23° C.) under a stream of nitrogen. 33.7 kg of brown HTDI crystals were obtained.

[0129] Example 2 :Purification of HTDI

[0130] The product obtained in Example 1 is incorporated in 280 kg of toluene and kept at 70° C. for 2 hours under stirring. A colored solution is obtained. The solution is cooled to 40° C. to produce two phases. A highly colored heavy phase gradually forms at the bottom of the reactor. It is flushed out. A pale yellow solution is collected. When cooled to 0° C., solid HTDI is collected. Solid HTDI is collected by filtering and then washing with toluene at a temperature between 0° C. and 25° C.

[0131] The colored lower phase was treated twice with toluene according to the same principle.

[0132] Example 3 :Process for preparing LiTDI

[0133] The solid HTDI obtained in Example 2 was dissolved in acetonitrile to obtain a solution comprising between 40 and 50% by weight of HTDI.

[0134] This solution was gradually added to a suspension of 5 kg of Li2CO3 in 94 kg of acetonitrile at room temperature while controlling the evolution of CO2. The mixture was stirred at room temperature (23°C) overnight.

[0135] The reaction water is removed by azeotropic distillation of water / CH3CN. Excess lithium carbonate is filtered off and the reaction medium is then concentrated at 70° C. under reduced pressure to a LiTDI / CH3CN concentration of 30% by weight.

[0136] The concentrate was cooled to -10° C. LiTDI crystallized. It was filtered off and washed twice with acetonitrile cooled to -20° C. Its purity, measured by NMR, was 100%.

[0137] It was subsequently dried, first under a stream of nitrogen and then under vacuum at 75° C. The lithium content was measured by ion chromatography to be 3.63%. The Hazen color was 14. The overall yield relative to DAMN was 43%, ie 14.7 kg of LiTDI.

[0138] The process advantageously makes it possible to obtain LiTDI with a Hazen color of 14 without the need for treatment with activated carbon.

Claims

1. A process for purifying a compound of formula (III): Wherein Rf is a fluoroalkyl group containing 1 to 5 carbon atoms, and the process comprises the following steps: a. the step of heating the composition comprising the compound of formula (III) in an organic solvent S3 at a temperature T1 until the compound of formula (III) has dissolved; b. cooling to an intermediate temperature T2 between 23°C and temperature T1, resulting in a step of a two-phase composition comprising: - phase P1, comprising said compound of formula (III); - Phase P2; c. a step of separating phases P1 and P2 at a temperature T2; d. a step of cooling phase P1 to a temperature T3 until crystals of the compound of formula (III) have formed, and The temperature T1 is between 40°C and the boiling point of the organic solvent S3. The organic solvent S3 is selected from toluene, benzene, xylene and cyclohexane.

2. The process as claimed in claim 1, characterized in that Rf represents CF3, CHF2, C2F5, or C3F7.

3. The process as claimed in claim 2, characterized in that Rf represents CF3 or C2F5.

4. The process according to any one of claims 1 to 3, characterized in that Rf represents CF3.

5. The process according to any one of claims 1 to 3, characterized in that The temperature T1 is between 50°C and 120°C.

6. The process as claimed in claim 5, characterized in that The temperature T1 is between 60°C and 100°C.

7. The process according to any one of claims 1 to 3, characterized in that Before step a), the compound of formula (III) has a water content of between 1% and 25% by weight relative to the total weight of the compound of formula (III).

8. The process as claimed in claim 7, characterized in that Before step a), the compound of formula (III) has a water content of between 5% and 20% by weight relative to the total weight of the compound of formula (III).

9. The process as claimed in claim 8, characterized in that Before step a), the compound of formula (III) has a water content of between 10 and 16% by weight relative to the total weight of the compound of formula (III).

10. The process according to any one of claims 1 to 3, characterized in that The temperature T2 is between 23°C and 50°C.

11. The process as claimed in claim 10, characterized in that The temperature T2 is between 30°C and 50°C.

12. The process according to any one of claims 1 to 3, characterized in that Phase P1 comprises more than 30% of the compound of formula (III) initially contained in the solution obtained at the end of step a).

13. The process as claimed in claim 12, characterized in that Phase P1 comprises more than 35% of the compound of formula (III) initially contained in the solution obtained at the end of step a).

14. The process as claimed in claim 13, characterized in that Phase P1 comprises more than 40% of the compound of formula (III) initially contained in the solution obtained at the end of step a).

15. The process according to any one of claims 1 to 3, characterized in that Phase P1 comprises from 0.5% to 70% by weight, relative to the total weight of said phase P1.

16. The process as claimed in claim 15, characterized in that Phase P1 comprises from 1% to 50% by weight, relative to the total weight of said phase P1.

17. The process as claimed in claim 16, characterized in that Phase P1 comprises 5% to 30% by weight, relative to the total weight of said phase P1.

18. The process according to any one of claims 1 to 3, characterized in that The temperature T3 is between 40°C and -30°C.

19. The process as claimed in claim 18, characterized in that The temperature T3 is between 25°C and -15°C.

20. The process as claimed in claim 19, characterized in that The temperature T3 is between 10°C and -5°C.

21. The process according to any one of claims 1 to 3, characterized in that It comprises a further step e) of filtering off the composition obtained at the end of step d).

22. The process according to any one of claims 1 to 3, characterized in that It comprises a step a') of contacting the compound of formula (III) with an organic solvent S3 before step a).

23. The process as claimed in claim 22, characterized in that The compound of formula (III) in step a') is obtained by a process comprising the following steps: -x) a step of contacting the compound of formula (III) with water; -y) a step of heating the composition obtained in step x) to a temperature T6; -z) a step of cooling the composition obtained in step y) until crystals of the compound of formula (III) have formed; -z') a step of filtering off the crystals and optionally drying; -z") an optional step of washing the crystals with water and an optional drying step.

24. The process as claimed in claim 23, characterized in that The compound of formula (III) in step a') is obtained by a process comprising the following steps: -x) a step of placing the compound of formula (III) in contact with water at a mass ratio of compound of formula (III) / water ranging from 1:1 to 1:

4.

25. The process as claimed in claim 24, characterized in that The mass ratio of the compound of formula (III) / water is 1:1 to 1:

2.

26. The process of claim 23, wherein: The temperature T6 is between 30°C and 80°C.

27. The process as claimed in claim 26, characterized in that The temperature T6 is between 40°C and 70°C.

28. The process of claim 23, wherein: The compound of formula (III) in step a') is obtained by a process comprising the following steps: -z") an optional step of washing the crystals with water at 23°C and an optional drying step.

29. A process for preparing a lithium imidazole compound of formula (V): (V) Wherein Rf is a fluoroalkyl group containing 1 to 5 carbon atoms, and the process comprises: -1) Purifying a compound of formula (III) according to a process as described in any one of claims 1 to 28; and -2) reacting the compound of formula (III) with a lithiated base.

30. The process as claimed in claim 29, characterized in that The lithiating base is selected from the group consisting of lithium hydride, lithium carbonate, lithium hydroxide and mixtures thereof.

31. A process as claimed in any one of claims 29 and 30, characterised in that Prior to step 2), the compound of formula (III) is dissolved in an organic solvent S4.

32. The process as claimed in claim 31, characterized in that The organic solvent S4 has a donor number ranging from 1 to 70.

33. The process as claimed in claim 32, characterized in that The organic solvent S4 has a donor number ranging from 5 to 65.

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