JP5483977B2 - Method for producing N-substituted imidazole compound - Google Patents

Description

  The present invention relates to a method for producing an N-substituted imidazole compound. N-substituted imidazole compounds are compounds that are useful as curing agents and curing aids such as epoxy resins and polyurethane resins, various agricultural chemicals, pharmaceutical intermediates, and dyeing intermediates.

  The method for synthesizing the N-substituted imidazole compound depends on the type of the target N-substituted imidazole compound. For example, the imidazole compound and chloroethylamine hydrochloride are reacted to give 1- (2-amino Ethyl) imidazoles (Non-Patent Document 1), imidazole compounds and ethylene carbonate are reacted to synthesize 1- (2-hydroxyethyl) imidazoles (Patent Document 1), aldehyde compounds and compounds A method in which a primary amine is reacted to form an imine compound, and then an α, β-dicarbonyl compound and ammonia are added and reacted (Patent Document 2). Imidazole, a halide and an aqueous hydroxide solution are reacted with N- The method of making it react in presence of substituted imidazole (patent document 3) etc. is mentioned.

  The reaction solution obtained by the method of the above prior art document contains not only the target N-substituted imidazole compound but also an N-unsubstituted imidazole compound as an unreacted raw material or by-product. -Separation and purification of substituted imidazole compounds are required. However, since the N-substituted imidazole compound has a low melting point, it is difficult to purify by recrystallization, and extraction with an organic solvent is complicated, and there is a problem in production efficiency. Therefore, purification by distillation is considered suitable for obtaining an N-substituted imidazole compound with high purity and high production efficiency.

U.S. Pat. No. 3,178,446 JP 2005-82551 A Japanese Patent Laid-Open No. 4-226961

Synthetic Communication, 21 (4), 535-544, 1991

However, the N-unsubstituted imidazole compound contained in the reaction solution is about 90 ° C. even when the imidazole has the lowest melting point. When this is separated by distillation, it is cooled and solidified in a distillation line such as a condenser. There is a risk of blockage. For this reason, there is a problem that a special distillation apparatus is required or distillation in two stages is required, which is very complicated and has low production efficiency.
Therefore, an object of the present invention is to efficiently produce a high-purity N-substituted imidazole compound.

  However, as a result of intensive studies in view of such circumstances, the present inventors have found that by distilling a mixture containing an N-substituted imidazole compound and an N-unsubstituted imidazole compound in the presence of a specific organic solvent, The present inventors have found that N-unsubstituted imidazole compounds mixed in the solution as reaction raw materials are difficult to solidify upon distillation, and that N-substituted imidazole compounds can be obtained with high purity.

（式中、Ｒ１〜Ｒ３は、各々独立して、水素原子または炭素数１〜３のアルキル基であり、Ｘは、炭素数８〜２０のアルキル基、または水酸基もしくはアミノ基で置換された炭素数１〜６のアルキル基である。）

（式中、Ｒ１〜Ｒ３は、各々独立して、水素原子または炭素数１〜３のアルキル基である。） That is, the gist of the present invention is to distill a solution containing an N-substituted imidazole compound represented by the following formula (1) and an N-unsubstituted imidazole compound represented by the following formula (2) to obtain the formula (1). A method for producing an N-substituted imidazole compound, comprising a step of fractionating an N-substituted imidazole compound, wherein the solution has an N-unsubstituted imidazole whose boiling point at normal pressure is represented by the formula (2) It contains an alcohol solvent that is within a temperature range of ± 30 ° C. with respect to the boiling point of the system compound at normal pressure.
Hereinafter, the N-substituted imidazole compound represented by the formula (1) is simply referred to as “N-substituted imidazole compound”, and the N-unsubstituted imidazole compound represented by the formula (2) is simply referred to as “N-unsubstituted imidazole compound”. May be written.

Wherein R1 to R3 are each independently a hydrogen atom or an alkyl group having 1 to 3 carbon atoms, and X is a carbon atom substituted with an alkyl group having 8 to 20 carbon atoms, or a hydroxyl group or an amino group. (It is an alkyl group of formula 1-6.)

(In the formula, R1 to R3 are each independently a hydrogen atom or an alkyl group having 1 to 3 carbon atoms.)

  According to the present invention, when a solution containing an N-substituted imidazole compound and an N-unsubstituted imidazole compound is distilled to fractionate the N-substituted imidazole compound, N is added together with an organic solvent having a predetermined boiling point. -Since the unsubstituted imidazole compound is distilled, the N-unsubstituted imidazole compound is solidified in the distillation line and the line is less likely to be clogged. Therefore, a special distillation apparatus and complicated Work is unnecessary, and a high-purity N-substituted imidazole compound can be produced efficiently.

The present invention is described in detail below.
In the present invention, the normal pressure means 1 atm.

  The present invention is a method for producing an N-substituted imidazole compound, wherein a solution containing an N-substituted imidazole compound and an N-unsubstituted imidazole compound is distilled to fractionate the N-substituted imidazole compound. Process. First, a solution containing an N-substituted imidazole compound and an N-unsubstituted imidazole compound will be described.

[Solution containing N-substituted imidazole compound and N-unsubstituted imidazole compound]
In the present invention, the solution to be distilled is a reaction solution produced in the process of synthesizing the N-substituted imidazole compound, and is a solution containing the N-substituted imidazole compound and the N-unsubstituted imidazole compound. For example, it is a solution (reaction solution) containing an N-unsubstituted imidazole compound as an unreacted raw material or product and an N-substituted imidazole compound as a target product obtained by the reaction. Examples of a method for obtaining an N-substituted imidazole compound include the methods described in the above-mentioned prior art documents. Typically, N-unsubstituted imidazole compounds and substituent-containing compounds such as alkylating agents are used. Is a method of reacting.
Hereinafter, a method for producing an N-alkyl-substituted imidazole compound represented by the following formula (1) by reacting an N-unsubstituted imidazole compound with an alkylating agent will be described as an example.

  In the formula, each of R1 to R3 is independently a hydrogen atom or an alkyl group having 1 to 3 carbon atoms, and X is a carbon number substituted with an alkyl group having 8 to 20 carbon atoms, or a hydroxyl group or an amino group. 1 to 6 alkyl groups. Preferably, R1 is a hydrogen atom or an alkyl group having 1 to 3 carbon atoms, R2 and R3 are hydrogen atoms, and X is an alkyl group having 1 to 3 carbon atoms including a hydroxyl group or an amino group.

(A) N-unsubstituted imidazole compound The N-unsubstituted imidazole compound is typically an imidazole compound having the structure of the following formula (2).

  In Formula (2), R1 to R3 are each independently a hydrogen atom or an alkyl group having 1 to 3 carbon atoms.

  Specific examples of the N-unsubstituted imidazole compound represented by the formula (2) include imidazole; 2-alkylimidazole such as 2-methylimidazole, 2-ethylimidazole, 2-propylimidazole, 2-isopropylimidazole, 4- Examples thereof include 4-alkylimidazoles such as methylimidazole, among which imidazole and 2-alkylimidazole (especially 2-methylimidazole) are preferable.

(B) Alkylating agent Examples of the alkylating agent include alkyl halides, alkylene oxides, primary alkyl alcohols having a leaving group at the terminal, and ethylamine derivatives having a leaving group at the 2-position.

  Examples of the alkyl halide include alkyl halides having the structure of the following formula (3).

  In formula (3), n is a natural number of 7 to 19, and X is a halogen atom such as chlorine, bromine or iodine. Specific examples of the alkyl halide include 1-chlorooctane, 1-bromooctane, 1-iodooctane, 1-chlorodecane, 1-bromodecane, 1-iododecane, 1-chlorododecane, 1-bromododecane, 1- Examples include iodododecane, 1-chlorohexadecane, 1-bromohexadecane, and 1-iodohexadecane. Among them, the terminal halogen atom is a chlorine atom, compared with the case where the terminal halogen atom is a bromine atom or an iodine atom. Thus, the quaternary chlorination reaction is difficult to proceed, and the target N-substituted imidazole compound tends to be obtained, which is preferable.

  Examples of the alkylene oxide include alkylene oxides having the structure of the following formula (4).

  In formula (4), R is a hydrogen atom or an alkyl group having 1 to 6 carbon atoms. Specific examples of the alkylene oxide include ethylene oxide, propylene oxide, 1,2-epoxybutene, 1,2-epoxypentene, 1,2-epoxyhexane, and among them, ethylene oxide and propylene oxide are preferable. .

  Examples of the primary alkyl alcohol having a leaving group at the terminal include alkyl alcohols having the structure of the following formula (5).

  In formula (5), n is a natural number of 1 to 6, and X is a halogen atom such as chlorine, bromine or iodine. Specific examples of the alkyl alcohol include 2-chloroethanol, 3-chloro-1-propanol, 4-chloro-1-butanol, 2-bromoethanol, 3-bromo-1-propanol, 2-iodoethanol, 3-iodo-1-propanol and the like. Among them, a primary alkyl alcohol whose terminal leaving group is a chlorine atom is quaternary chlorinated as compared with the case where the terminal leaving group is a bromine atom or iodine atom. This is preferable in that the reaction does not easily proceed and the desired N-substituted imidazole compound tends to be obtained.

  Examples of the ethylamine derivative having a leaving group at the 2-position include an ethylamine derivative having a structure of the following formula (6).

  In formula (6), Y is a halogen atom such as chlorine, bromine, iodine, or fluorine, a sulfonyloxy group which may have a substituent, or a sulfonic acid group. Specific examples of such ethylamine derivatives include 2-chloroethylamine derivatives, 2-bromoethylamine derivatives, 2-iodoethylamine derivatives, 2-fluoroethylamine derivatives, p-toluenesulfonic acid (2-aminoethyl) ester derivatives, methane Examples include sulfonic acid (2-aminoethyl) ester derivatives, trifluoromethanesulfonic acid (2-aminoethyl) ester derivatives, 2-aminoethyl sulfate ester derivatives, and the like. Among them, Y is a halogen atom or a sulfonic acid group, It is particularly preferable that Y is a chlorine atom, a bromine atom, or a sulfonic acid group because industrial raw materials are easily available.

  The amount of the alkylating agent (B) to be used is generally 0.7 to 3 equivalents, preferably 0.8 to 2 equivalents, relative to the N-unsubstituted imidazole compound (A). If the alkylating agent (B) is too much, side reactions occur and impurities tend to increase. If it is too little, unreacted raw materials remain and the yield tends to decrease. In the case where alkyl halide, primary alkyl alcohol having a leaving group at the terminal or ethylamine derivative having a leaving group at the 2-position is used as the alkylating agent (B), an alkali metal such as sodium hydroxide or potassium hydroxide is used. 0.5 to 5 equivalents of an alkali metal hydroxide and carbonate mixture such as a mixture of potassium hydroxide and potassium carbonate with respect to the N-unsubstituted imidazole compound (A), It is particularly preferable to add 0.6 to 4 equivalents.

  Examples of the solvent used when the N-unsubstituted imidazole compound (A) and the alkylating agent (B) are reacted include alcohol solvents such as methanol, ethanol and 2-propanol; nitrile solvents such as acetonitrile; Amide solvents such as N, N-dimethylacetamide, N, N-dimethylformamide and N-methylpyrrolidone; aprotic polar solvents such as dimethyl sulfoxide; ether solvents such as tetrahydrofuran, cyclopentylmethyl ether and t-butylmethyl ether Hydrocarbon-type solvents, such as toluene, are mentioned, From these solvents, it can be used individually by 1 type or in combination of 2 or more types.

  Examples of the reactor used when the N-unsubstituted imidazole compound (A) and the alkylating agent (B) are reacted include a thermometer, a reflux condenser, a stirring device, an inert gas inflow facility, and a charging device. It can be carried out using an autoclave equipped with an ordinary reactor. The stirring method is not particularly limited as long as the contents can be sufficiently mixed.

  The charging method for reacting the N-unsubstituted imidazole compound (A) with the alkylating agent (B) is appropriately determined according to the type of the alkylating agent (B). For example, when alkylene oxide is used as the alkylating agent (B), the N-unsubstituted imidazole compound (A) and the reaction solvent are charged into the reactor and the liquid temperature is set to a predetermined temperature, and then the alkylene oxide is dividedly supplied. When an alkyl halide, a primary alkyl alcohol having a leaving group at the terminal, or an ethylamine derivative having a leaving group at the 2-position is used as the alkylating agent (B), an N-unsubstituted imidazole compound (A ), A base, and a reaction solvent are charged and the liquid temperature is set to a predetermined temperature, and then the primary alkyl alcohol or ethylamine derivative is dividedly supplied.

  In the case where an alkyl halide is used as the alkylating agent (B), the reaction temperature is preferably 20 to 200 ° C, more preferably 25 to 190 ° C, and particularly preferably 30 to 180 ° C. Moreover, when using an alkylene oxide as an alkylating agent (B), it is preferable that it is 30-200 degreeC, More preferably, it is 35-190 degreeC, Most preferably, it is 40-180 degreeC. Moreover, when using the primary alkyl alcohol which has a leaving group at the terminal as an alkylating agent (B), it is preferable that it is 10-200 degreeC, More preferably, it is 20-180 degreeC, Most preferably, it is 25-150. ° C. Furthermore, when an ethylamine derivative having a leaving group at the 2-position is used as the alkylating agent (B), it is preferably 50 to 200 ° C., more preferably 55 to 190 ° C., particularly preferably 60 to 180 ° C. It is. If the temperature is too low, the reaction rate tends to be slow and the yield tends to decrease. If the temperature is too high, by-products increase, and the yield and quality tend to decrease. The reaction time is usually 0.1 to 24 hours, preferably 0.5 to 20 hours. The reaction can usually be carried out at normal pressure, but when alkylene oxide is used as the alkylating agent (B), the reaction may be carried out under pressure as necessary.

  In the reaction solution after completion of the reaction, an unreacted N-unsubstituted imidazole compound (A) or alkylating agent (B), an N-substituted imidazole compound as a target product, an inorganic salt as a by-product, etc., A reaction solvent will be included. When the above alkyl halide, primary alkyl alcohol or ethylamine derivative is used as the alkylating agent (B), inorganic salts produced as a by-product are removed by filtration, and unreacted alkylene oxide and reaction solvent are distilled under reduced pressure. Leave.

[Step of fractionating N-substituted imidazole compound]
After the reaction is completed and low-boiling components such as a reaction solvent and inorganic salts are removed, the target N-substituted imidazole compound is fractionated by distillation. In the present invention, a specific organic solvent is present during this distillation. For example, a specific organic solvent is present in the system (a mixture containing an N-substituted imidazole compound and an N-unsubstituted imidazole compound) between the end of the reaction and the start of distillation in a distillation apparatus (distiller). Preferably, after completion of the reaction, the solvent in the reaction solution is distilled off to obtain a concentrate, followed by blending with a specific organic solvent and distillation.

  The specific organic solvent is an organic solvent whose boiling point at normal pressure (1 atm) is within a temperature range of ± 30 ° C. relative to the boiling point at normal pressure (1 atm) of the N-unsubstituted imidazole compound (hereinafter, specified It is also called an organic solvent.) A preferred boiling temperature range is −27 ° C. to + 20 ° C., and a particularly preferred boiling temperature range is −25 ° C. to + 10 ° C. When the temperature range of the boiling point is out of the above range, the distilled N-unsubstituted imidazole compound is solidified and the line tends to be blocked. Note that the boiling point at normal pressure (hereinafter also simply referred to as “boiling point”) can be measured with an everimeter or the like.

Examples of the specific organic solvent include alcohol solvents such as ethylene glycol, diethylene glycol, triethylene glycol, glycerin, cis-2-butene-1,4-diol, diethanolamine, triethanolamine, and 2,2′-thiodiethanol; Aromatic hydrocarbon solvents such as cyclohexylbenzene, o-nitroanisole, 1-chloronaphthalene, 1-bromonaphthalene, bicyclohexyl; halogen solvents such as 1,1,2,2-tetrabromoethane; propylbenzoate, benzyl Ester solvents such as benzoate, methyl salicylate, ethyl cinnamate; ether solvents such as phenyl ether and benzyl ether; nitrile solvents such as α-tolunitrile and succinonitrile; 2-pyrrolidinone, 1-ethyl-2 Amide solvents such as pyrrolidone; Carbonate solvents such as propylene carbonate; Heteroaromatic solvents such as quinoline and isoquinoline, etc., and alcohol solvents such as ethylene glycol, diethylene glycol, triethylene glycol and glycerin; -Aromatic hydrocarbon solvents such as nitroanisole; Ether solvents such as phenyl ether and benzyl ether; Amide solvents such as 2-pyrrolidinone and 1-ethyl-2-pyrrolidone are industrially readily available as raw materials Is preferable. These specific solvents can be used alone or in combination of two or more.
In the present invention, the above alcohol solvent is used as the specific organic solvent.

  The use amount of the specific organic solvent is usually 0.3 to 10 times (mass basis), preferably 0.5 to 8 times (mass basis) with respect to the content of the N-unsubstituted imidazole compound (A). .

Distillation conditions vary depending on the reaction raw materials, reaction products, by-products, types and compositions of solvents and specific organic solvents, etc., but basically the distillation should be carried out in the following order (1) to (3). Can do.
(1) A low boiling point component (such as a reaction solvent that cannot be completely removed) is distilled.
(2) A mixture of an N-unsubstituted imidazole compound (A) and a specific organic solvent is distilled.
(3) The target product (N-substituted imidazole compound) is distilled.
In each stage of the above (1) and (2), distillation was performed by total distillation (flowing the distilled liquid to the distillation side without returning it to the distillation can), and in the stage of (3) above, In order to increase the rectification effect, it is preferable to carry out distillation at a reflux ratio described later.

  Hereinafter, 2-methylimidazole as the N-unsubstituted imidazole compound (A) and ethylene oxide as the alkylating agent (B) are obtained, and 1- (as N-substituted imidazole compound is obtained. Diethylene glycol as a specific organic solvent was added to a concentrated liquid containing 2-hydroxyethyl) -2-methylimidazole (hereinafter referred to as “crude 1- (2-hydroxyethyl) -2-methylimidazole”) and distilled. The case where it does is demonstrated.

  After blending diethylene glycol as a specific organic solvent into crude 1- (2-hydroxyethyl) -2-methylimidazole, first, the crude 1- (2-hydroxyethyl) -2-methylimidazole is heated to increase the tower top temperature. The components having a relatively low boiling point such as the remaining reaction solvent are distilled by maintaining in a temperature range of 20 to 95 ° C. Further, a mixture of 2-methylimidazole and diethylene glycol is distilled in a temperature range of 95 to 125 ° C. Subsequently, 1- (2-hydroxyethyl) -2-methylimidazole is distilled in a temperature range of 150 to 180 ° C. The boiling point of 2-methylimidazole is 267 ° C. (normal pressure), and the boiling point of diethylene glycol is 245 ° C. (normal pressure).

The pressure during the distillation is first adjusted by adjusting the degree of vacuum in the range of 0.1 kPa to 5 kPa, and the remaining component having a relatively low boiling point such as a reaction solvent or a mixture of 2-methylimidazole and diethylene glycol is distilled. Let it come out. Thereafter, 1- (2-hydroxyethyl) -2-methylimidazole is distilled in the range of 0.1 kPa to 1 kPa.
The above temperature range and degree of vacuum are examples, and the appropriate temperature range and degree of vacuum range vary depending on the combination and content of each component in the reaction solution. If it is carried out, distillation purification is possible in other systems.

  The time from the start to the end of distillation is not particularly limited, but is preferably 24 hours or less. If the time is too long, a new impurity tends to be generated.

  As described above, while distilling a component having a relatively low boiling point such as a remaining reaction solvent or a mixture of 2-methylimidazole and diethylene glycol (stages (1) and (2) above), distillation is performed in the entire distillate. Is preferably performed. Increasing the reflux ratio causes 2-methylimidazole and diethylene glycol to separate and distill due to the rectification effect, so the blending effect of diethylene glycol decreases and 2-methylimidazole may solidify and clog in the distillation line Because there is.

  On the other hand, the N-substituted imidazole compound, which is the target product, has a tendency to reduce the rectification effect and quality (purity) if the reflux ratio is not set (total distillation). It is preferable to do. Specifically, the reflux ratio is preferably about 1: 1 to 1: 5. If the reflux ratio is increased too much, the distillation time will be prolonged, which tends to cause an increase in production cost and impurity by-product. A reflux ratio of 1: 1 means that ½ amount of the distilled liquid flows to the distillation side (distillation tank) and the remaining ½ amount is returned to the distillation can. The reflux ratio is 1: 5. Means flowing 1/6 of the distilled liquid to the distillation side (distillation tank) and returning the remaining 5/6 to the distillation can. The reflux ratio can be adjusted, for example, by installing an instrument that can adjust the amount of liquid returning to the distillation can and the amount of liquid flowing to the distillation side at the upper part of the rectification (distillation) column.

  As an apparatus for carrying out the distillation, a reaction apparatus different from the reaction apparatus for reacting the N-unsubstituted imidazole compound (A) and the alkylating agent (B) may be used. It is preferable in terms of production efficiency to perform distillation using the same apparatus. If you want to distill laboratory-level quantities, for example, an ordinary reactor equipped with a thermometer, a stirrer, a charging device, a distillation column, etc., an apparatus for adjusting the reflux ratio at the top of the distillation column Can be carried out using a reactor equipped with Further, if an industrial level amount is to be distilled, for example, a distillation facility equipped with a thermometer, a stirring device, a charging device, a distillation tower, etc., the top of the rectification (distillation) tower and the distillation tank In the middle of the line connecting the two, a reactor equipped with a meter for adjusting the reflux ratio can be used. The stirring method is not particularly limited as long as the contents can be sufficiently mixed.

  By the above distillation operation, the N-substituted imidazole compound can be fractionated from a mixture (for example, a reaction solution after completion of the reaction) containing at least the N-substituted imidazole compound and the N-unsubstituted imidazole compound. According to the present invention, an N-substituted imidazole compound can be obtained in a yield of 80% or more (before distillation) and a purity of 90 GCare% or more. The purity and yield of the fractionated N-substituted imidazole compound can be measured using gas chromatography.

  EXAMPLES Hereinafter, although an Example is given and this invention is demonstrated further more concretely, this invention is not limited to a following example, unless the summary is exceeded. In addition, the purity and yield of the obtained N-substituted imidazole compound are measured using gas chromatography under the following measurement conditions.

Column: DB-WAX 30m x 0.53mmI. D. × 1μm
Temperature rising conditions: 100 ° C. (holding 0 min) to 20 ° C./min to 220 ° C. (holding 19 min)
Inlet temperature: 230 ° C, splitless detector temperature: 230 ° C, FID (hydrogen flame ion detector)
Carrier gas: helium, 90 kPa
Injection volume: 1 μL
Analytical sample preparation method: 200 mg of N-substituted imidazole compound was weighed into a 10 mL volumetric flask and diluted with methanol to obtain an analytical sample.

Production Example 1
A 1 L reactor was charged with 454.0 g (5.53 mol) of 2-methylimidazole (boiling point 267 ° C.) and 113.5 g of methanol and purged with nitrogen, then the liquid temperature was raised to 120 ° C., and 292.0 g of ethylene oxide ( 6.63 mol) was added dropwise so that the reaction solution temperature did not exceed 130 ° C. After the completion of the dropwise addition, the mixture was reacted for 1 hour, and then the reaction solution was cooled to 50 ° C. and concentrated under reduced pressure to give 776.1 g of crude 1- (2-hydroxyethyl) -2-methylimidazole [1- (2-hydroxy Ethyl) -2-methylimidazole content: 495.2 g, 2-methylimidazole content: 42.6 g].

Example 1
200.2 g of crude 1- (2-hydroxyethyl) -2-methylimidazole obtained in Production Example 1 was attached to a device in which a riser tube having a diameter of 24 × 150 mm, in which 10 mm of McMahon packing was packed at the top of a 500 mL reactor, 1- (2-hydroxyethyl) -2-methylimidazole content: 127.7 g, 2-methylimidazole content: 11.0 g] and 33.0 g of diethylene glycol (boiling point: 245 ° C.) were added and distilled under reduced pressure. First, after raising the temperature appropriately at a vacuum degree of 0.4 kPa and distilling out low boiling point components, 2-methylimidazole and 12.5 g of diethylene glycol was distilled as a mixture. At this time, 2-methylimidazole did not solidify in the cooling line.

  Subsequently, the liquid temperature was further raised, and 1- (2-hydroxyethyl) -2-methylimidazole was distilled off under the conditions of a degree of vacuum of 0.4 kPa, a liquid temperature in the distillation can of 183 ° C., and a tower top temperature of 172 ° C. The reflux ratio at this time was set to 1: 2. The obtained fraction was 110.5 g, and the purity of 1- (2-hydroxyethyl) -2-methylimidazole was 94.8 GCarea%. The yield was 82% (content of 1- (2-hydroxyethyl) -2-methylimidazole before distillation).

Comparative Example 1
81.3 g of crude 1- (2-hydroxyethyl) -2-methylimidazole obtained in Production Example 1 was attached to an apparatus in which a riser tube having a diameter of 24 × 150 mm, in which 10 mm of McMahon packing was packed at the top of a 100 mL reactor, 1- (2-hydroxyethyl) -2-methylimidazole content: 32.5 g, 2-methylimidazole content: 2.8 g], and distilled under reduced pressure without adding any compounding agent. First, after raising the temperature appropriately at a vacuum degree of 0.4 kPa and distilling out low boiling point components, 2-methylimidazole was added under conditions of a vacuum degree of 0.4 kPa, a liquid temperature in the distillation can of 169 ° C., and a tower top temperature of 103 ° C. Distilled. At this time, 2-methylimidazole was solidified in the cooling line, and the distillation line was blocked. Therefore, further examination was discontinued.

  The N-substituted imidazole compound obtained by the production method of the present invention is a compound usefully used as a curing agent or curing catalyst such as an epoxy resin or a polyurethane resin, various agricultural chemicals, pharmaceutical intermediates, or dyeing intermediates.

Claims (1)

Formula distilling the solution containing the indicating N- unsubstituted imidazole compound shown N- substituted imidazole compound (1) and the following formula (2), the equation (1) shows N- substituted imidazole compounds A method for producing an N-substituted imidazole compound comprising a fractional distillation step,
The solution contains an alcohol solvent whose boiling point at normal pressure is within a temperature range of ± 30 ° C. relative to the boiling point at normal pressure of the N-unsubstituted imidazole compound represented by the formula (2). A method for producing a characteristic N-substituted imidazole compound.

Wherein R1 to R3 are each independently a hydrogen atom or an alkyl group having 1 to 3 carbon atoms, and X is a carbon atom substituted with an alkyl group having 8 to 20 carbon atoms, or a hydroxyl group or an amino group. (It is an alkyl group of formula 1-6.)

(In the formula, R1 to R3 are each independently a hydrogen atom or an alkyl group having 1 to 3 carbon atoms.)