DE102014214674A1 - Process for the preparation of substituted imidazolium salts - Google Patents

Abstract

This invention relates to a process for the preparation of 1,3-disubstituted imidazolium salts, which comprises reacting an α-dicarbonyl compound, an aldehyde, an amine and the hydrazoic acid of the anion Xn- and reacting in water, one with water miscible solvent or mixtures thereof takes place.

Description

wobei
R¹ ein organischer Rest mit 1 bis 20 Kohlenstoffatomen ist;
R³ ein organischer Rest mit 1 bis 20 Kohlenstoffatomen ist;
die Reste R², R⁴ und R⁵ unabhängig voneinander ausgewählt sind aus der Gruppe bestehend aus Wasserstoff, organischer Rest mit 1 bis 20 Kohlenstoffatomen;
X für das Anion einer Wasserstoffsäure mit einem pK_S-Wert von höchstens 2, bevorzugt höchstens 1, noch bevorzugter im Bereich von –5 bis 1, (jeweils gemessen bei 25 °C, 1 bar in Wasser oder Dimethylsulfoxid) steht, und
n für 1, 2 oder 3 steht,
und das Verfahren dadurch gekennzeichnet ist, dass
(a) eine α-Dicarbonylverbindung, ein Aldehyd, ein Amin und die Wasserstoffsäure des Anions X^n– miteinander umgesetzt werden und
(b) die Umsetzung in Wasser, einem mit Wasser mischbaren Lösungsmittel oder deren Gemische erfolgt, wobei eine Temperatur von –50 °C bis 15 °C, bevorzugt –5 °C bis 10 °C eingehalten wird.The invention relates to a process for the preparation of 1,3-disubstituted imidazolium salts of the formula (I)

in which
R ^{1 is} an organic radical having from 1 to 20 carbon atoms;
R ^{3 is} an organic radical having 1 to 20 carbon atoms;
the radicals R ² , R ⁴ and R ^{5 are} independently selected from the group consisting of hydrogen, organic radical having 1 to 20 carbon atoms;
X is more preferably in the range of -5 to 1, (in each case measured at 25 ° C, 1 bar in water or dimethyl sulfoxide) for the anion of a hydrochloric acid having a _pK a value of at most 2, preferably at most 1, and
n is 1, 2 or 3,
and the method is characterized in that
(a) an α-dicarbonyl compound, an aldehyde, an amine and the ^hydrazoic acid of the anion X ^n- are reacted together, and
(B) the reaction in water, a water-miscible solvent or mixtures thereof, wherein a temperature of -50 ° C to 15 ° C, preferably -5 ° C to 10 ° C is maintained.

Background of the invention

Imidazolium salts have great application-related importance as ionic liquids. The term ionic liquids is understood to mean salts having a melting point of less than 200 ° C., in particular salts which are liquid at room temperature.

For example, ionic liquids, in particular imidazolium salts, are suitable as solvents in many industrial applications, for example also for the dissolution of cellulose.

Desirable are therefore simple and inexpensive process for the preparation of such imidazolium salts in the highest possible purity and quality. The prior art describes various methods for synthesizing the imidazolium salts.

That's how it describes WO 2009/027250 A2 generally the synthesis of 1,3-diethylimidazolium acetate from formaldehyde, glyoxal, ethylamine and acetic acid. The distillation of the mixture takes place at temperatures ≥ 80 ° C.

In the WO 91/14678 describes a one-step process for the preparation of imidazolium salts from an α-dicarbonyl compound, an aldehyde, an amine and an acid. The reaction takes place in the presence of an organic solvent, toluene.

This method has some disadvantages. Thus, first, it is discontinuous due to the azeotropic distillation, because in such a process step, a continuous process is generally not possible. Secondly, this reaction produces unwanted by-products, especially the ammonium salt of the acid used (preferred acids are strong acids with a pK _s less than 4). Third, the reaction takes place in an organic solvent which, together with the water formed during the reaction, has to be removed by azeotropic distillation in a complicated manner. Due to other by-products, the resulting reaction product has a dark to black color.

A similar procedure is also from the WO 02/094883 A2 known. As anions hydrophobic, for example, fluorinated anions are used here, so that the products arise as a separate phase and can be easily separated from the aqueous phase. Also in the WO 02/094883 A2 described method has the disadvantage that it is discontinuous.

The WO 2009/074535 A2 describes a process for the preparation of imidazolium salts, which is characterized in that a hydrogen acid having a pK _s value of at least 2 (measured at 25 ° C, 1 bar in water or dimethyl sulfoxide) is used.

The previous methods of the prior art have the disadvantages described.

It was therefore an object of the present invention to provide a process for the preparation of imidazolium salts, which does not have the disadvantages mentioned and in particular can be dispensed with the use of organic solvents, which has an improved product purity, and in which acids with a pK _S ≤ 2 can be used.

The inventive method, the object of the invention is achieved in a surprising manner.

Description of the invention

To the imidazolium salts

wobei
R¹ ein organischer Rest mit 1 bis 20 Kohlenstoffatomen ist;
R³ ein organischer Rest mit 1 bis 20 Kohlenstoffatomen ist;
die Reste R², R⁴ und R⁵ unabhängig voneinander ausgewählt sind aus der Gruppe bestehend aus Wasserstoff, organischer Rest mit 1 bis 20 Kohlenstoffatomen;
X für das Anion einer Wasserstoffsäure mit einem pK_S-Wert von höchstens 2, bevorzugt (jeweils gemessen bei 25 °C, 1 bar in Wasser oder Dimethylsulfoxid) steht,
und
n für 1, 2 oder 3 steht.According to the invention 1,3 disubstituted imidazolium salts of the formula (I) with

in which
R ^{1 is} an organic radical having from 1 to 20 carbon atoms;
R ^{3 is} an organic radical having 1 to 20 carbon atoms;
the radicals R ² , R ⁴ and R ^{5 are} independently selected from the group consisting of hydrogen, organic radical having 1 to 20 carbon atoms;
X represents value of at most 2, preferably (in each case measured at 25 ° C, 1 bar in water or dimethyl sulfoxide) for the anion of a hydrochloric acid having a pK _S,
and
n is 1, 2 or 3.

The term "organic radical" in the context of the invention means that it is a hydrocarbon radical which may contain, in addition to carbon and hydrogen, further heteroatoms, in particular oxygen atoms. For example, it may contain hydroxyl groups, ether groups, ester groups or carbonyl groups.

In a preferred embodiment, R ^{1 is} an organic radical having from 1 to 10 carbon atoms and R ^{3 is} an organic radical having from 1 to 10 carbon atoms.

R ¹ and R ³ are more preferably independently of one another a hydrocarbon radical having 1 to 20 carbon atoms, in particular having 1 to 10 carbon atoms, which contains no other heteroatoms such as oxygen or nitrogen in addition to carbon and hydrogen. The hydrocarbon radical may be aliphatic (including unsaturated aliphatic groups) or aromatic, or may contain both aromatic and aliphatic groups. Preferably, R ¹ and R ^{3 are} an aliphatic hydrocarbon radical.

The hydrocarbon group is, for example, selected from the group consisting of phenyl group, benzyl group, a phenyl group substituted by one or more C ₁ to C ₄ alkyl groups or benzyl group, alkyl groups and alkenyl groups, the allyl group being a particularly preferred alkenyl group.

More preferably, each of R ¹ and R ^{3 is} a C ₁ to C ₁₀ alkyl group, preferably a C ₁ to C ₆ alkyl group, more preferably a C ₁ to C ₄ alkyl group. Most preferably, R ¹ and R ^{3 are} independently selected from the group consisting of methyl group, Ethyl group, n-propyl group, isopropyl group, n-butyl group, sec-butyl group, tert-butyl group, wherein the methyl group, ethyl group, n-propyl group, n-butyl group have particular importance.

In a further embodiment, R ¹ and R ³ each represent the same organic radical. In this embodiment, the imidazolium salts of the formula (I) are therefore in particular symmetrical, disubstituted imidazolium salts. In an alternative embodiment, the imidazolium salts are mixtures of imidazolium salts of the formula (I) with different radicals R ¹ and R ³ . Such mixtures are obtainable by using different amines, for example primary amines with different alkyl groups. The resulting mixture then contains both imidazolium salts in which R ¹ and R ^{3 are} identical, as well as imidazolium salts in which R ¹ and R ^{3 have} different meanings.

In various particularly preferred embodiments, the radicals R ¹ and R ³ are selected as follows:
R ¹ = R ³ = methyl group; R ¹ = R ³ = ethyl group; R ¹ = R ³ = n-propyl group;
R ¹ = R ³ = n-butyl group; R ¹ = methyl group and R ³ = ethyl group; R ¹ = methyl group and
R ³ = n-propyl group; R ¹ = methyl group and R ³ = n-butyl group; R ¹ = methyl group and
R ³ = allyl group; R ¹ = ethyl group and R ³ = allyl group; R ¹ = methyl group and
R ³ = benzyl group; R ¹ = ethyl group and R ³ = benzyl group.

The radicals R ² , R ⁴ and R ⁵ are independently selected from the group consisting of hydrogen, organic radical having 1 to 20 carbon atoms, wherein R ⁴ and R ^{5 may} also together form an aliphatic or aromatic ring. The organic radical may contain not only carbon and hydrogen but also heteroatoms such as nitrogen or oxygen; it may preferably contain oxygen, in particular in the form of hydroxyl groups, ester groups, ether groups or carbonyl groups.

In particular, the radicals R ² , R ⁴ and R ^{5 are} independently selected from the group consisting of hydrogen, hydrocarbon radical, wherein the hydrocarbon radical in addition to carbon and hydrogen may at most contain hydroxyl groups, ether groups, ester groups or carbonyl groups.

Preferably, the R ² , R ⁴ and R ^{5 are} independently selected from the group consisting of hydrogen, hydrocarbon radical having 1 to 20 carbon atoms, in particular having 1 to 10 carbon atoms, wherein the hydrocarbon radical contains no other heteroatoms such as oxygen or nitrogen.

The hydrocarbon radical may be aliphatic (including unsaturated aliphatic groups) or aromatic, or may consist of both aromatic and aliphatic groups, where R ⁴ and R ^{5 may} also form an aromatic or aliphatic hydrocarbon ring, optionally substituted by further aromatic or aliphatic hydrocarbon groups may be substituted (the number of carbon atoms of the optionally substituted hydrocarbon ring including the substituents may be preferably not more than 40, in particular not more than 20, more preferably not more than 15 or not more than 10). Examples of hydrocarbon radicals which may be mentioned are the phenyl group, a benzyl group, a phenyl group or benzyl group substituted by one or more C ₁ -C ₄ -alkyl groups, alkyl groups, alkenyl groups and, in the case where R ⁴ and R ^{5 form} a ring, by R ⁴ and R ⁵ formed aromatic 5- or 6-ring, a cyclohexene or cyclopentene, which ring systems may be substituted in particular by one or more C ₁ - to C ₁₀ -, in particular C ₁ - to C ₄ -alkyl groups. As the hydrocarbon radical, aliphatic hydrocarbon radicals are preferred.

The radicals R ² , R ⁴ and R ⁵ are particularly preferably selected independently of one another from the group consisting of hydrogen atom, C ₁ - to C ₈ -alkyl group, C ₁ - to C ₈ -alkenyl group, the allyl group being particularly preferably used as alkenyl group ,

Most preferably, the radicals R ² , R ⁴ and R ^{5 are} independently selected from the group consisting of hydrogen atom, methyl group, ethyl group, n-propyl group, isopropyl group, n-butyl group, sec-butyl group, tert-butyl group, where the group consisting from methyl group, ethyl group, n-propyl group, n-butyl group has special meaning.

In a particular embodiment, R ^{2 is} independently of the other radicals R ⁴ and R ⁵ and the remaining radicals R ¹ and R ^{3 is} an H atom. Imidazolium salts of the formula (I) in which R ^{2 is} an H atom are particularly advantageous in the context of the present invention.

In a particular embodiment, R ² , R ⁴ and R ^{5 represent} a hydrogen atom. Alternatively, in this particular embodiment, R ^{2 is} selected from the group consisting of hydrogen, C ₁ to C ₄ alkyl, and R ⁴ , R ⁵ are independently selected from the group consisting of hydrogen, C ₁ to C ₄ alkyl.

As individual cases for the cations of the compounds of the formula (I), mention may be made:
1-butyl-3-methyl-imidazolium (R ¹ = butyl group, R ³ = methyl group); 1-butyl-3-ethylimidazolium (R ¹ = butyl group, R ³ = ethyl group); 1,3-dimethylimidazolium (R ¹ = methyl group, R ³ = methyl group); 1-ethyl-3-methyl-imidazolium (R ¹ = ethyl group, R ³ = methyl group); 1-ethyl-2,3-dimethylimidazolium (R ¹ = ethyl group, R ² = methyl group, R ³ = methyl group).

In formula (I), n is 1, 2 or 3; the anion has one, two or three negative charges and accordingly there are one, two or three imidazolium cations in the salt. Preferably n is 1 or 2, more preferably n is 1; The anion is therefore particularly preferably monovalent.

In formula (I), X represents the anion of a hydrochloric acid having a _pK a value of at most 2, in particular of at most 1, and in a preferred embodiment in the range of -5 to 1 (measured at 25 ° C, 1 bar in water or dimethyl sulfoxide).

The pK _s value is the negative decadic logarithm of the acid constant, K _s . The _pK a value is either measured to 25 ° C, 1 bar in water or dimethyl sulfoxide as a solvent; According to the invention it is therefore sufficient if an anion, either in water or in dimethyl sulfoxide has the appropriate _pK. Dimethyl sulfoxide is particularly useful when the anion is not well soluble in water. Both solvents can be found in standard works.

Suitable anions X ^- may be mentioned in particular compounds having one or more carboxylate groups (short-carboxylate), which have the above _pK.

Particular examples of such carboxylates are organic compounds having 1 to 20 carbon atoms which contain one or two, preferably one carboxylate group.

It may be both aliphatic and aromatic compounds, wherein the aromatic compounds are understood as meaning those containing aromatic groups. Particular preference is given to aliphatic or aromatic compounds which, apart from the oxygen atoms of the carboxylate group, contain no further heteroatoms or at best also contain one or two hydroxyl groups, carbonyl groups or ether groups. Very particular preference is given to aliphatic or aromatic compounds which, apart from the oxygen atoms of the carboxylate group, contain no further heteroatoms.

Examples of compounds having two carboxylate groups are the anions of phthalic acid, isophthalic acid, C ₂ -C ₆ -dicarboxylic acids, for example oxalic acid malonic acid, succinic acid, glutaric acid, adipic acid.

As compounds having a carboxylate group, the anions of aromatic, aliphatic, saturated or unsaturated C ₁ - to C ₂₀ -carboxylic acids, in particular alkanecarboxylic acids, alkenecarboxylic acids, alkynecarboxylic acids, alkadienecarboxylic acids, alkadienecarboxylic acids, hydroxycarboxylic acids or ketocarboxylic acids or aromatic carboxylic acids such as benzoic acid or phenylacetic acid are listed. Suitable alkanecarboxylic acids, alkene carboxylic acids and alkadiene carboxylic acids are also known as fatty acids.

As anions X ^- may be mentioned in particular the benzoate anion and the anions of C ₁ - to C ₂₀ -alkanecarboxylic acids, which may optionally be substituted by one or two, preferably a hydroxy group. Particularly preferred are the benzoate anion and the anions of C ₂ to C ₂₀ alkanecarboxylic acids; in particular the acetate anion and propionate anion; most preferred is the acetate anion. Preferred imidazolium salts of the formula (I) are soluble in water or miscible with water. In particular, the solubility in water or miscibility in water is at least 50 grams of imidazolium salt, more preferably at least 100 grams of imidazolium salt most preferably at least 200 grams of imidazolium salt and especially at least 300 grams of imidazolium salt in 1 liter of water (at 1 bar, 21 ° C).

Particular examples of imidazolium salts which may be mentioned are 1,3-disubstituted imidazolium salts of the formula (I) where R ¹ and R ^{3 are} identical and X ^{- is} a compound having a carboxylate group.

Particularly preferred imidazolium salts are 1,3-disubstituted imidazolium salts of the formula (I) in which R ¹ and R ^{3 are} identical and represent a C ₂ - to C ₄ -alkyl group, in particular an ethyl group, and where R ² , R ⁴ and R ^{5 is} a hydrogen atom and X ^{- is} an acetate anion or a propionate anion.

To the starting compounds of the preparation

According to the invention, an α-dicarbonyl compound, an aldehyde, an amine and the hydrazoic acid of the anion X ^- are reacted with each other.

The above starting compounds are selected according to the desired radicals R ¹ to R ⁵ in formula (I).

wobei R⁴ und R⁵ die oben genannte Bedeutung haben. The α-dicarbonyl compound is preferably a compound of the formula (II)

wherein R ⁴ and R ^{5 have} the abovementioned meaning.

The compound of the formula (II) is particularly preferably glyoxal.

The aldehyde is, in particular, an aldehyde of the formula R ² -CHO, where R ^{2 has} the abovementioned meaning. Particularly preferred is formaldehyde; The formaldehyde can also be used in the form of formaldehyde-releasing compounds such as paraformaldehyde or trioxane.

The amines are, in particular, primary amines of the R-NH _{2 type} . The radical R corresponds to the radicals R ¹ and R ^{3 of} the imidazolium salts obtained. If a defined primary amine is used, an imidazolium salt is obtained in which the radicals R ¹ and R ^{3 are} identical. If a mixture of amines (for example mixture of R'-NH ₂ and R "-NH ₂ ) is used, a mixture of imidazolium salts (mixture of salts with R ¹ and R ³ = R ', R ¹ and R ³ = R "and salts with R ¹ = R 'and R ³ = R").

The hydrazoic acid is the desired hydrazoic acid of the anion X ^- , preferably this hydrazoic acid is selected from the group consisting of F ₃ C-SO ₃ H, HClO ₄ , HCl, H ₂ SO ₄ , H ₃ C-SO ₃ H , HNO ₃ , HBF ₄ , Cl ₃ C-CO ₂ H, HO ₂ C-CO ₂ H, HCl ₂ C-CO ₂ H, H ₂ SO ₃ , HSO ₄ ^- , the corresponding anion is in each case F ₃ C-SO ₃ ^- , ClO ₄ ^- , Cl ^- , HSO ₄ ^- , H ₃ C-SO ₃ ^- , NO ₃ ^- , BF ₄ ^- , Cl ₃ C-CO ₂ ^- , HO ₂ C-CO ₂ ^- , HCl ₂ C- CO ₂ ^- , HSO ₃ ^- , SO ₄ ^2- . Particularly preferred are HCl, H ₃ C-SO ₃ H, HBF ₄ , H ₂ SO ₄ .

Implementation of the procedure

The reaction of the starting compounds is carried out according to the invention in water, a water-miscible solvent or mixtures thereof.

Particularly suitable water-miscible solvents are protic solvents, preferably aliphatic alcohols or ethers having a maximum of 4 carbon atoms, for example methanol, ethanol, methyl ethyl ether, tetrahydrofuran. Suitable protic solvents are miscible with water in any ratio (at 1 bar, 21 ° C).

Preferably, the reaction is carried out in water or mixtures of water with the protic solvents above. The reaction is particularly preferably carried out in water, without addition of an organic solvent or in the absence of an organic solvent.

Preferably, no hydrophobic, water-immiscible organic solvents (hydrocarbons, for example toluene) are used as entrainer to remove the water or solvent after the reaction. The reaction mixture particularly preferably contains neither during nor after the reaction hydrophobic, water-immiscible organic solvents such as hydrocarbons; In particular, the reaction mixture contains no solvents other than water or said protic solvents (neither during nor after the reaction).

The reaction of the starting components can be carried out at atmospheric pressure and for example at temperatures of 5 to 100 ° C, in particular 5 to 50 ° C, more preferably 10 to 40 ° C.

The output components can be combined in any order.

The reaction can be carried out batchwise, semi-continuously or continuously. In the semi-continuous procedure, for example, at least one starting compound can be submitted and the remaining starting components are added.

In the continuous mode of operation, the starting components are continuously brought together and the product mixture is continuously removed. The starting components may be supplied singly or as a mixture of all or part of the starting components. In a particular embodiment, the amine and the acid are mixed in advance and fed as a stream, the remaining components can be supplied individually or as a mixture (2nd stream). In a further particular embodiment, all starting components containing carbonyl groups (ie the α-dicarbonyl compound, the aldehyde and the hydrazoic acid of the anion X ^- , if it is a carboxylate) are pre-mixed and fed together as a stream; the remaining amine is then fed separately.

The continuous production can be carried out in any reaction vessels, for example a stirred tank. It is preferably carried out in a stirred tank cascade, for example from 2 to 4 stirred tanks, or in a tubular reactor.

The resulting reaction mixture is generally dark colored due to by-products. A lightening of the reaction mixture can be achieved in the present case, surprisingly by oxidation.

For this purpose, the resulting reaction mixture can be treated with an oxidizing agent. The oxidizing agent may be, for example, gaseous or liquid. Particularly suitable is gaseous oxygen, which is brought into contact with the reaction mixture in a suitable manner, for example by pressure and / or introduction below the liquid surface.

In particular, liquid oxidizing agents, in particular oxidizing agents, which are dissolved in suitable, miscible with the reaction mixture solvents. Particularly suitable solvents are water, a water-miscible solvent or mixtures thereof.

Particularly suitable water-miscible solvents are protic solvents, preferably aliphatic alcohols or ethers having a maximum of 4 carbon atoms, for example methanol, ethanol, methyl ethyl ether, tetrahydrofuran. Suitable protic solvents are miscible with water in any ratio (at 1 bar, 21 ° C).

Preferably, the oxidizing agent is dissolved in water or mixtures of water with the protic solvents above, more preferably it is dissolved in water.

Suitable oxidizing agents are known to the person skilled in the art. Oxidizing agents are compounds with high electron affinity (electrophilicity). Highly electrophilic and therefore suitable as oxidizing compounds are, for example, oxygen and oxygen-containing per-compounds, in particular hydrogen peroxide, metal peroxides or organic peroxides such as sodium persulfate or tert-butyl hydroperoxide, inorganic and organic peracids, for example periodic acid or percarboxylic acids, but also other compounds such as sulfur or metal compounds of high valence states [for example, iron (III) compounds, manganese dioxide, potassium permanganate, chromic acid, chromanhydride, lead dioxide or lead tetraacetate].

Preference is given to gaseous oxygen and in particular hydrogen peroxide, preferably in the form of the above solutions, in particular as a 10 to 40% strength by weight solution.

The amount of the oxidizing agent is selected as required, for example, 0.1 to 20 mol, preferably 0.5 to 10 mol of oxidizing agent can be used per 1 mol of imidazolium salt (based on the amount theoretically obtained from the reaction mixture).

The oxidation can be carried out for example at temperatures of 20 to 100 ° C, in particular 50 to 90 ° C at atmospheric pressure until a lightening of the approach occurs.

Water and / or other solvent (see above), preferably water, is preferably distilled off directly from the reaction mixture, that is to say no entrainer, for example an organic, water-immiscible solvent, is used. The water and / or other solvent may be separated before or after the oxidation described above. If an oxidation is carried out, the separation of the water is preferably carried out thereafter. Excess acid (HX) is preferably neutralized, for example with alkali hydroxide, especially sodium hydroxide. The resulting salt (NaX) may preferably be precipitated by addition of a suitable solvent such as acetonitrile or methanol and removed from the mixture. The solvent used can then be separated off again, for example by distillation.

According to the process of the invention, imidazolium salts are obtained by a single-stage reaction in high purity and yield. The measures for implementation and processing are easy to perform. Unwanted salts, such as ammonium salts, which are difficult to remove, are not obtained in the process of the invention. Excess acid can be easily removed. In particular, the method can also be carried out continuously.

The following examples serve to illustrate the invention without limiting it in any way.

Examples

Thirteen experiments were carried out. The amine used in each experiment and the acid used in each experiment are shown in the table.

General test procedure

A cryostat was cooled to -5 ° C, then the amine (4.8 mol) was charged. Subsequently, formaldehyde (2.4 mol) and then the acid (2.4 mol) were added. The dosing rates were chosen so that the reactor temperature did not rise above 5 ° C. After the two doses, the dosage of glyoxal (2.4 mol) was started. The reaction temperature was raised to 10 ° C. A temperature of> 10 ° C was avoided. The volatile constituents were then removed under reduced pressure on a rotary evaporator, taking care that the bath temperature did not exceed 80 ° C. The pure substance thus obtained represented the final product.

The following table gives an overview of the particular starting materials used and the yields achieved. table

QUOTES INCLUDE IN THE DESCRIPTION

This list of the documents listed by the applicant has been generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Cited patent literature

• WO 2009/027250 A2 [0005]
• WO 91/14678 [0006]
• WO 02/094883 A2 [0008, 0008]
• WO 2009/074535 A2 [0009]

Claims (5)

Process for the preparation of 1,3-disubstituted imidazolium salts of the formula (I)

R ^{1 is} an organic radical having from 1 to 20 carbon atoms; R ^{3 is} an organic radical having 1 to 20 carbon atoms; the radicals R ² , R ⁴ and R ^{5 are} independently selected from the group consisting of hydrogen, organic radical having 1 to 20 carbon atoms; X is the anion of a hydrochloric acid having a _pK a value of at most 2 (in each case measured at 25 ° C, 1 bar in water or dimethyl sulfoxide), and n is 1, 2 or 3, and the method is characterized in that (A) an α-dicarbonyl compound, an aldehyde, an amine and the ^hydrazoic acid of the anion X ^n- are reacted together and (b) the reaction is carried out in water, a water-miscible solvent or mixtures thereof. Process according to claim 1, characterized in that R ¹ = R ³ . A method according to claim 1 or 2, characterized in that R ² , R ⁴ and R ⁵ independently represent an H atom or a C ₁ - to C ₁₀ alkyl group. Method according to one of claims 1 to 3, characterized in that X is selected from the group consisting of Cl ^- , H ₃ C-SO ₃ ^- , BF ₄ ^- , HSO ₄ ^- . Method according to one of claims 1 to 4, characterized in that the reaction is carried out in water.