WO2003091222A1

WO2003091222A1 - Process for producing n-alkyl-n'-alkylimidazolium salt

Info

Publication number: WO2003091222A1
Application number: PCT/JP2003/000957
Authority: WO
Inventors: Toshiyuki Ito; Yoshihisa Tsuji; Masahiro Torihara; Hideharu Iwasaki
Original assignee: Kuraray Co.,Ltd.
Priority date: 2002-04-23
Filing date: 2003-01-31
Publication date: 2003-11-06
Also published as: JP2003313171A; AU2003208077A1

Abstract

A process for producing an N-alkyl-N'-alkylimidazolium salt, characterized by reacting the corresponding imidazolium halide salt with an alkali metal salt having the anion to be possessed by the N-alkyl-N'-alkylimidazolium salt and subsequently washing the reaction mixture with a hydrocarbon solvent and then with water. By the process, an imidazolium salt usable as a medium in various reactions can be industrially advantageously produced.

Description

Specification

Method for producing N-alkyl-N'-alkylimidazolyl salts

The present invention provides a compound represented by the general formula (I):

(In the formula, R ¹ and R ² each represent an alkyl group having 1 to 8 carbon atoms, and A 1 represents an anion.)

The present invention relates to a method for producing an N-alkyl-N'-alkyl imidazolium salt [hereinafter referred to as imidazolium salt (I)].

Imidazolium salt (I) is in the form of a molten salt that is in a liquid state at room temperature to a relatively high temperature of about 300 and falls into the category of ionic liquids. Its properties show high polarity based on the aprotic ionic structure, and it has excellent solubility for low molecular weight organic and inorganic compounds. In addition, imidazolyl salt (I) has a vapor pressure of 0 and is non-volatile, so it provides a clean reaction environment, can be used in a vacuum, and can be used as a medium in various reactions. . Furthermore, imidazolyl salt (I) has the property of not being mixed with water or a protic organic solvent, and can provide an environment for a two-phase reaction. In addition, imidazolium salt (I) retains ionic properties and has charge transfer characteristics, and is used as an electrolyte for lithium secondary batteries and as a solid electrolyte by gelation. Can also be expected. Technology background

Traditionally, ionic liquids have been made from organic cations and inorganic anions. Examples of the cationic species include alkylammonium [NR _X H _{4 —} _x ] +, alkyl phosphonium [PR _X H _{4 —} _x ] ⁺ , N, N, -alkylimidazolium, N-alkylpyri Jiniumu Ri Contact like are used, as the Anion species, for example, aluminum chlorinated (a 1 C 1 ₄ one, a 1 ₂ C 1 ₇ -, etc.) and, tetrafurfuryl O b borate Anion (BF ₄ —) And hexafluorophosphate (PF ₆ _) are used.

A method for synthesizing a room-temperature molten salt composed of an imidazolyl salt is as follows: (1) A 1,3-dialkylimidazolyl halide is reacted with a silver salt or a lead salt containing an anion in the presence of an alcoholic solvent such as methanol. Exchange Law [Journal of the Chemical Society, Chemical Communications, pp. 965 (1992), and Tokuhei 9 — See No. 50 988 88], (2) A method of adding hexafluorophosphoric acid to an aqueous solution of 1,3-dialkylimidazolium halide and performing salt exchange [Chemica 1 Comm. unications), 1765 (1998) and Journal of Materials Chemistry, 2627 (1992)], (3) A salt exchange method by adding a salt such as sodium hexafluorofluoride to 1,3-dialkylimidazolium halide in an acetone solvent [Polyhedron (P olyhedron), see Section 127 (1996)].

In the above method (1), the octalogenated salt, which is a by-product, is Yes, it has the advantage that it is easy to purify imidazolium salts, but there are restrictions on the types of metal salts that can be used, and there is a possibility that salts of heavy metals such as silver and zinc may remain in imidazolium salts. Has problems. In method (2), since a highly corrosive strong acid is used, there is no reaction device (vessel) that can be industrially implemented, and an operation of synthesizing an imidazolium salt in an aqueous solution and then removing water is performed. However, there is a problem that lipophilic by-products such as nitrogen-containing heterocyclic compounds remain. In the method (3), an operation of synthesizing an imidazolyl salt in acetone having a low boiling point and then removing the acetone is performed. The operation is simple, but the precipitated imidazolyl salt includes sodium chloride or the like. There is a problem that the hydrophilic by-product remains. That is, the imidazolium salts produced by the methods (1) to (3) which do not have an operation for positively removing lipophilic or hydrophilic impurities produced as by-products contain impurities. It is not possible to carry out the reaction in the presence of a noble metal complex which is susceptible to trace impurities as a reaction medium.

An object of the present invention is to provide a method for industrially advantageously producing an imidazolium salt that can be used as a medium for various reactions. Disclosure of the invention

The present invention relates to a process for producing an imidazolium salt (I), which comprises reacting a corresponding imidazolium octylogen salt with an alkali metal salt containing an anion contained in the imidazolium salt (I) and then reacting with a hydrocarbon solvent. A method for producing an imidazolium salt (I), which comprises washing and then washing with water.

In a preferred embodiment of the present invention, in the general formula (I), R ¹ is a methyl group, R ² is a butyl group, and A_ is hexafluoro. An imidazolium salt (I), which is a phosphate ion, is obtained. BEST MODE FOR CARRYING OUT THE INVENTION

In the above general formula, examples of the alkyl group represented by R ¹ and R ² include a methyl group, an ethyl group, a propyl group, an isopropyl group, a butyl group, an isobutyl group, a hexyl group, a cyclohexyl group, a heptyl group, And R ¹ and R ² are preferably different from each other. A- The shade I O emissions represented, for example, _{_{BF 4 -, PF 6 -,}} CH 3 C0 2 -, CF 3 C0 2 _{one, CF 3 S0 3 -, (} CF 3 S 0 2) 2 N- and No.

As the imidazolium salt (I), N-butyl N'-methyl imidazolium hexafluorophosphate is preferred in consideration of purification efficiency.

The imidazolium halide corresponding to the imidazolium salt (I) can be easily prepared by a known method. For example, N-butyl-N'-methylimidazolyl chloride is produced, for example, by stirring 1-methylimidazole and butane chloride under heating [Chemica 1 (Chemica 1 Comm unications), 1] 7 65 (1992)].

In the present invention, an imidazolium salt (I) is produced by reacting an imidazolium halide salt corresponding to the imidazolium salt (I) with an alkali metal salt containing an anion A_.

The reaction is preferably performed in the presence of a solvent. Examples of the solvent include aliphatic hydrocarbons such as heptane, hexane, cyclohexane, octane and decane; aromatic hydrocarbons such as benzene, toluene, xylene and mesitylene; methylene chloride, chloroform and tetrachloride Halogenated hydrocarbons such as carbon and black benzene; ethyl acetate, butyl acetate, ethyl propionate, Esters such as butyl propionate; ketones such as acetone, methyl ethyl ketone, methyl isopropyl ketone, and methyl isobutyl ketone; ethers such as dimethyl ether, diisopropyl ether, tetrahydrofuran and 1,4-dioxane are used. These solvents may be used alone or as a mixture of two or more. The amount of the solvent used is not particularly limited, but is preferably an amount that can be stirred even when salts are precipitated, and is 0.1 to 100 times the weight of the imidazolym halide. The weight is more preferably 0.2 to 80 times by weight, particularly preferably 0.3 to 70 times by weight, in consideration of the economics and operability of the reaction.

The reaction temperature and reaction time are not particularly limited, but are usually in the range of 30 to 200, preferably in the range of 1 to 50 hours.

After completion of the reaction, the obtained reaction mixture is optionally removed by separating or distilling off the reaction solvent, followed by washing with a hydrocarbon solvent and then with water. Examples of the hydrocarbon solvent include aliphatic or alicyclic saturated hydrocarbons such as pentane, hexane, cyclohexane, methylcyclohexane, heptane and octane; aromatics such as benzene, toluene, xylene and mesitylene Hydrocarbons. These hydrocarbon solvents may be used in combination with other organic solvents. Examples of other organic solvents include halogenated hydrocarbons such as methylene chloride, chloroform, carbon tetrachloride, getyl ether, and the like. Ethers such as tetrahydrofuran, tetrahydropyran, dipropyl ether, diisopropyl ether, dibutyl ether, and anisol; esters such as methyl acetate, ethyl acetate, propyl acetate, butyl acetate, methyl butyrate, ethyl butyrate, and propyl butyrate; acetone, methyl ethyl ketone, and getyl ketone; Ketones such as methyl isopropyl pyrketone, methyl isobutyl ketone, and cyclohexanone are exemplified. these These solvents may be used alone or as a mixture of two or more. The proportion of the hydrocarbon solvent in the mixed solvent is preferably in the range of 100 to 50%.

Although the number of times of washing with the hydrocarbon solvent is not particularly limited, it is usually preferably at least two times. Although the amount of the hydrocarbon solvent used for washing is not particularly limited, it is usually 0.1 to 100 times the weight of the obtained imidazolium salt (I). It is preferably 0.5 to 80 times by weight, and particularly preferably 1 to 50 times by weight in consideration of the washing effect and economy. The solvent used for washing is removed by liquid separation or evaporation as necessary, but it is not necessary to remove it before washing with water.

The water used for the washing is preferably one that does not contain metal components as much as possible, such as ion-exchanged water, distilled water and purified water. Although the amount of water used is not particularly limited, it is usually preferably 0.01 to 50 times the weight of the obtained imidazolium salt (I). In this case, the weight is more preferably 0.05 to 40 times the weight, and particularly preferably 0.1 to 30 times the weight. The number of washes is usually preferred to be 2 or more.

After the above-mentioned washing treatment, the organic solvent and water used for washing are removed by heating, depressurizing, or heating and depressurizing to obtain the desired imidazolyl salt (I). Example

Hereinafter, the present invention will be described specifically with reference to examples, but the present invention is not limited to the examples. Reference example 1

32.1 g (1 mo 1) of imidazole and 92.5 g (1 mo 1) of 1-chlorobutane were placed in a tri-flask with a volume of 30 Om 1 equipped with a reflux tube, thermometer and stirrer. Was replaced with nitrogen, and the mixture was heated with stirring at 70 ° C. for 48 hours. After cooling to room temperature, 200 g of ethyl acetate was added for washing. After separating and removing the ethyl acetate, washing with 100 g of ethyl acetate, separating and removing, and further removing the ethyl acetate under reduced pressure, 1-butyl-3-methylimidazolyl chloride is obtained. 136.2 g (yield 78%) were obtained. Example 1

In a 1 L three-necked flask equipped with a reflux tube, a thermometer, and a stirrer, 94.5 g (0.5 mol) of 1-butyl-3-methylimidazolidum chloride obtained in Reference Example 1 and sodium hexane 83.9 g (0.5 mol) of fluorophosphate and 500 g of acetone were added thereto, and the mixture was stirred at 27 ° C for 24 hours. The obtained reaction mixture was filtered to remove a precipitate, and then acetone was distilled off under reduced pressure. To the residue, 200 g of toluene was added, and the mixture was stirred for 15 minutes at 27, and the operation of separating and removing toluene was performed twice. Next, 200 g of ion-exchanged water was added, the mixture was stirred for 15 minutes, and the operation of separating and removing water was performed twice. By drying at 70 under a reduced pressure of 1 Pa for 8 hours, 136.5 g (yield 85%) of N-butyl-N′-methylimidazolylhexafluorophosphate was obtained. Reference example 2

In Example 1, the reaction solution was filtered using 20 g of Celite, and dried under reduced pressure to obtain N-butyl-N, -methylimidazolium hexane. 141.4 g (yield 88.1%) of safluorophosphate was obtained. Reference example 3

In a three-necked flask having an inner volume of 50 ml, 14.4 g (0.134mo 1) of benzaldehyde, 20 g of N-butyl_Ν'-methylimidazoliumhexafluorophosphate obtained in Example 1 and 0.32 g (0.2 mmo 1) of nickel acetyl acetate was added, and the system was replaced with nitrogen and further replaced with oxygen. The temperature was raised to 60 ° C. while supplying 5 ml of oxygen per minute, and the mixture was stirred for 12 hours. After the reaction was completed, 20 g of isopropyl ether was added for extraction, and the mixture was analyzed by gas chromatography (GC-14A, Shimadzu Corporation, column; G-100, 30 m, manufactured by The Chemicals Inspection Association). The conversion of benzaldehyde was 98% and the selectivity to benzoic acid was 88%. Comparative Example 1

In Reference Example 3, the N-butyl-N'-methylimidazolylhexafluo obtained in Reference Example 2 was used instead of the N-butyl-N'-methylimidazonium hexafluorophosphate obtained in Example 1. The same reaction and operation were carried out except that olophosphate was used. The conversion of benzaldehyde was 45% and the selectivity to benzoic acid was 71%. Industrial applicability

According to the present invention, an imidazolium salt (I) that can be used as a medium for various reactions can be industrially advantageously produced.

Claims

The scope of the claims

General formula (I)

In producing an N-alkyl-N′-alkyl imidazolium salt represented by the following formula, an alcohol containing the corresponding imidazolium halide and the anion of the N-alkyl-N′-alkyl imidazolium salt The method for producing an N-alkyl-N'-alkylimidazolym salt as described above, wherein the salt is reacted with a metal salt, washed with a hydrocarbon solvent, and then washed with water.

2. The production method according to claim ¹ , wherein in the general formula (I), R ¹ is a methyl group, R ² is a butyl group, and A— is a hexafluorophosphate ion.

3. The production method according to claim 1, wherein the reaction is performed in the presence of a solvent.

4. The process according to claim 3, wherein the solvent is selected from aliphatic hydrocarbons, aromatic hydrocarbons, octogenated hydrocarbons, esters, ketones and ethers.

5. The method according to claim 1, wherein after the reaction is completed, the obtained reaction mixture is subjected to a washing operation after removing the reaction solvent by liquid separation or distillation, and then subjecting the reaction mixture to a washing operation.

6. The production method according to claim 1, wherein the hydrocarbon solvent is an aliphatic saturated hydrocarbon, an alicyclic saturated hydrocarbon, or an aromatic hydrocarbon.

7. The production method according to claim 6, wherein the aliphatic or alicyclic saturated hydrocarbon is selected from pentane, hexane, cyclohexane, methylcyclohexane, heptane and octane.

8. The method according to claim 6, wherein the aromatic hydrocarbon is selected from benzene, toluene, xylene, and mesitylene.

9. The production method according to claim 1, wherein the amount of the hydrocarbon solvent used is 0.1 to 100 times the weight of the N-alkyl-N'-alkylimidazolide salt.

10. The method according to claim 1, wherein the amount of the hydrocarbon solvent used is 0.5 to 80 times the weight of the N-alkyl-N'-alkyl imidazolium salt.

1 1. The production method according to claim 1, wherein the amount of the hydrocarbon solvent used is 1 to 50 times the weight of the N-alkyl-N'-alkyl imidazolium salt.

1 2. The production method according to claim 1, wherein washing with a hydrocarbon solvent is performed at least twice.

1 3. The method according to claim 1, wherein the water is selected from ion-exchanged water, distilled water and purified water.

14. The production method according to claim 1, wherein the amount of water used is 0.01 to 50 times the weight of the N-alkyl-N'-alkylimidazolyte salt.

15. The production method according to claim 1, wherein the amount of water used is 0.05 to 40 times the weight of the N-alkyl-N'-alkylimidazolium salt.

1 6. When the amount of water used is N-alkyl-N'-alkylimidazoliu 2. The production method according to claim 1, wherein the weight is 0.1 to 30 times the weight of the salt.

1 7. The production method according to claim 1, wherein washing with water is performed twice or more.