JP5523076B2 - Method for producing vinylimidazole compound - Google Patents

Description

  The present invention relates to a method for producing a vinylimidazole compound that can be used, for example, as a curing agent for an epoxy resin, a reaction accelerator for a urethane resin, or a raw material monomer for a UV curable resin or an acrylic resin.

  As a method for producing a vinylimidazole compound, Patent Document 1 discloses a method in which a 2-hydroxyethylimidazole derivative is dehydrated in a liquid phase in the presence of an alkali metal hydroxide or alcoholate.

JP-A-4-21672

  However, in the method disclosed in Patent Document 1, since the generated vinylimidazole compound and water are recovered in a gaseous state from the reaction solution, in the heated reaction solution, as the reaction proceeds, liquid 2- The ratio of the hydroxyethylimidazole derivative in the reaction solution is relatively decreased, and the ratio of the solid alkali metal hydroxide and the like is relatively increased. Therefore, as the reaction proceeds, the viscosity of the reaction solution increases and stirring becomes difficult in the middle. Therefore, the reaction is stopped with the raw material 2-hydroxyethylimidazole derivative remaining, and after further addition of the raw material, The reaction had to be restarted. That is, the ratio of raw materials that can be substantially used for the reaction (raw material utilization rate) in the charged raw materials is low, and there is room for improvement in production efficiency.

  Therefore, the present invention is a method for producing a vinylimidazole compound from a hydroxyethyl group-containing imidazole compound, and there is no need to stop the reaction in a state where the raw material hydroxyethyl group-containing imidazole compound remains, and the raw material utilization rate The purpose is to obtain a vinylimidazole compound with high yield.

  However, as a result of intensive studies in view of such circumstances, the present inventor made a reaction solution containing a vinylimidazole compound or water produced by allowing a solvent having a higher boiling point than the produced vinylimidazole compound to coexist in the reaction system. Even if it was recovered in a gaseous state from the inside, the increase in the viscosity of the reaction solution can be suppressed, so that it was not necessary to stop the dehydration reaction and the production efficiency was increased, and the present invention was completed.

  That is, the gist of the present invention is that a vinylimidazole compound represented by the following general formula (2) is obtained by subjecting a hydroxyethyl group-containing imidazole compound represented by the following general formula (1) to a dehydration reaction in the presence of a dehydrating agent. A method for producing a compound, characterized in that the dehydration reaction is performed in a solvent having a boiling point at normal pressure of 30 ° C. or more higher than the boiling point at normal pressure of the vinylimidazole compound.

[In formula, R1-R3 is respectively independently a hydrogen atom, a C1-C4 alkyl group, or a C1-C4 alkoxy group. ]

[In formula, R1-R3 is respectively independently a hydrogen atom, a C1-C4 alkyl group, or a C1-C4 alkoxy group. ]

  According to the present invention, since the raw material utilization rate can be improved as compared with the conventional method, an increase in production efficiency can be expected. In addition, in the conventional method, the viscosity of the reaction liquid increases as the dehydration reaction proceeds, so an apparatus equipped with a strong stirring blade is required. However, in the present invention, the increase in the viscosity of the reaction liquid is suppressed. Therefore, it is possible to manufacture in a circulation type distillation facility without a stirring blade.

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

  In the present invention, the hydroxyimidazole-containing imidazole compound represented by the general formula (1) is subjected to a dehydration reaction in the presence of a dehydrating agent to produce the vinylimidazole compound represented by the general formula (2). The method is characterized in that the dehydration reaction is performed in a solvent whose boiling point at normal pressure is 30 ° C. or more higher than the boiling point of the vinylimidazole compound at normal pressure. First, the hydroxyethyl group-containing imidazole compound will be described.

(A) Hydroxyethyl group-containing imidazole compound The hydroxyethyl group-containing imidazole compound, which is a raw material in the present invention, is an imidazole compound represented by the above general formula (1). In general formula (1), R1 to R3 are each independently a hydrogen atom, an alkyl group having 1 to 4 carbon atoms, or an alkoxy group having 1 to 4 carbon atoms, and the alkyl group and the alkoxy group each have a substituent. You may have. Examples of the substituent usually include a halogen atom, a hydroxyl group, an alkoxy group, an amino group, a sulfanyl group, an aryl group, and a heteroaryl group.

Specific examples of the hydroxyethyl group-containing imidazole compound represented by the general formula (1) include 1- (2-hydroxyethyl) imidazole, 2-methyl-1- (2-hydroxyethyl) imidazole, 2- Examples include ethyl-1- (2-hydroxyethyl) imidazole, 2-ethyl-4-methyl-1- (2-hydroxyethyl) imidazole, 2-methoxy-1- (2-hydroxyethyl) imidazole, 1- (2-hydroxyethyl) imidazole and 2-methyl-1- (2-hydroxyethyl) imidazole are preferred.
The hydroxyethyl group-containing imidazole compound represented by the general formula (1) can be produced by a known method, for example, according to the method described in JP-A-2005-82551.

(B) Dehydrating agent In the present invention, the hydroxyethyl group-containing imidazole compound is subjected to a dehydration reaction in the presence of a dehydrating agent to produce the vinylimidazole compound represented by the general formula (2).
The dehydrating agent is not particularly limited as long as it dehydrates the 2-hydroxyethyl group of the hydroxyethyl group-containing imidazole compound to a vinyl group, but alkali metal hydroxides and alkali metal alcoholates are preferably used. obtain. Specific examples of the alkali metal hydroxide include potassium hydroxide and sodium hydroxide. Examples of the alkali metal alcoholate include alcohols having 1 to 3 carbon atoms such as sodium methylate, sodium ethylate, and potassium methylate. , Potassium ethylate and the like. In the present invention, these dehydrating agents can be used alone or in combination of two or more.

  The usage-amount of a dehydrating agent is 0.01-20 equivalent normally with respect to the hydroxyethyl group containing imidazole type compound which is a raw material, Preferably it is 0.05-5 equivalent, More preferably, it is 0.1-1 equivalent. If there is too much dehydrating agent, the dehydration reaction will proceed rapidly, causing safety problems, and the viscosity of the reaction solution will tend to be difficult to stir, and if too little, the reaction rate will be slow. The reaction tends to stop in the middle.

(C) Specific solvent In the present invention, the dehydration reaction of the hydroxyethyl group-containing imidazole compound represented by the general formula (1) is carried out in a specific solvent. The specific solvent in the present invention is a solvent whose boiling point at normal pressure is 30 ° C. or more higher than the boiling point at normal pressure of the vinylimidazole compound represented by the general formula (2). As a specific solvent, what is necessary is just 30 degreeC or more higher than the boiling point in the normal pressure of the said vinylimidazole type compound, Preferably it is 30-500 degreeC, More preferably, it is 40-400 degreeC, Most preferably, it is 50-300 degreeC. In the range, those higher than the boiling point of the vinylimidazole compound at normal pressure are suitable. In this invention, a specific solvent can be used individually by 1 type or in combination of 2 or more types.

Specific examples of the specific solvent include alcohol solvents such as glycerin and polyethylene glycol, hydrocarbon solvents such as liquid paraffin, fluorine solvents, and ionic liquids such as ethylmethylimidazolium trifluoromethanesulfonimide.
Among these, it is preferable to use a hydrophilic solvent in terms of excellent compatibility with the raw material hydroxyethyl group-containing imidazole compound, and specifically, an alcohol solvent or an ionic liquid is preferably used.

  As a specific example of the combination of the specific solvent (C) and the vinylimidazole compound of the reaction product, for example, when the vinylimidazole compound is 1-vinylimidazole, the boiling point is 196 ° C. (normal pressure). Examples of the specific solvent that can be used in the solvent include diethylene glycol (boiling point 245 ° C. at normal pressure), triethylene glycol (boiling point 287 ° C. at normal pressure), and glycerin (boiling point 290 ° C. at normal pressure).

The amount of the specific solvent used is usually 0.01 to 100 parts by mass (equivalent), preferably 0.02 to 50 parts by mass (equivalent) with respect to 1 part by mass of the hydroxyethyl group-containing imidazole compound as a raw material. Particularly preferred is 0.05 to 10 parts by mass (equal amount). If the amount of a specific solvent used is too large, the rate of dehydration reaction will slow down or the reaction will stop in the middle, which tends to deteriorate the production efficiency and decrease the yield. As the process proceeds, the viscosity increases and it tends to be difficult to carry out the reaction normally.
In the present invention, a solvent other than the above-mentioned specific solvent may be included in the dehydration reaction as long as the object of the present invention is not impaired. In addition, a polymerization inhibitor such as BHT (3,5-dibutyl-4-hydroxytoluene), MEHQ (hydroquinone monomethyl ether), or phenothiazine may be added to the specific solvent.

  Examples of the reactor used for subjecting the hydroxyethyl group-containing imidazole compound represented by the general formula (1) to the dehydration reaction include a thermometer, a reflux condenser, a stirring device, a dropping funnel, an inert gas inflow facility, In addition, an autoclave equipped with a charging device or a normal reactor can be used. The stirring method is not particularly limited as long as the contents can be sufficiently mixed. Further, in the present invention, since the increase in the viscosity of the reaction solution can be suppressed, it is possible to manufacture with a circulating distillation facility without a stirring blade.

  When the hydroxyethyl group-containing imidazole compound represented by the general formula (1) is subjected to a dehydration reaction, for example, a dehydrating agent and a specific solvent are added to the reactor in which the raw material hydroxyethyl group-containing imidazole compound is produced. The reaction is allowed to proceed for a predetermined period of time by adjusting the charging, predetermined reaction temperature and reaction pressure conditions. The dehydrating agent may be charged all at once or dividedly.

  The reaction temperature (liquid temperature) is usually 80 to 350 ° C, preferably 120 to 300 ° C, particularly preferably 150 to 250 ° C. If the temperature is too low, the reaction rate tends to slow down or the reaction tends to stop.If the temperature is too high, decomposition of the raw material hydroxyethyl group-containing imidazole compound occurs, or the produced vinylimidazole compound polymerizes. The yield tends to decrease.

  The reaction pressure is usually 0.01 hPa to 1013 hPa, preferably 0.1 hPa to 100 hPa. When the pressure is too high (that is, close to normal pressure), the produced vinylimidazole stays in the reaction vessel and tends to be decomposed by heat.

  The reaction time is usually 0.5 to 30 hours, preferably 1 to 20 hours. If it is too short, the reaction does not proceed sufficiently and the yield is lowered. If it is too long, there is no particular problem with the reaction, but the productivity tends to be lowered.

  The vinyl imidazole compound and water produced by the dehydration reaction of the hydroxyethyl group-containing imidazole compound are vaporized from the reaction solution, liquefied through the condensation tube, and recovered as a distillate. Since this distillate may contain a raw material hydroxyethyl group-containing imidazole compound, a specific solvent and a by-product, it is preferable to further purify by distillation to obtain a high-purity product. The rectification method may be batch rectification or continuous rectification, and the rectification column may be a plate column or a packed column.

By the above rectification operation, a vinylimidazole compound having a purity of 99.5% or more can be obtained, and a high purity vinylimidazole compound having a purity of 99.9% or more can be obtained. Moreover, the yield (raw material utilization) with respect to the raw material (hydroxyethyl group-containing imidazole compound) of the vinylimidazole compound obtained by rectification is 70% or more, and the yield with respect to the crude vinylimidazole compound before rectification. Is 95% or more. The purity and yield of the vinylimidazole compound can be measured using gas chromatography.
In Example 1 of Patent Document 1, 0.21 mmol of the product (1-vinylimidazole) is obtained with respect to 0.34 mmol of the charged raw material (2-hydroxyethylimidazole). Only 63%.

  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. The predicted boiling point at normal pressure described below is a value calculated by Advanced Chemistry Development (ACD / Labs) Software V8.14 for Solaris. Moreover, the purity and yield of the obtained vinylimidazole compound were measured using gas chromatography under the following measurement conditions.

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

[Production of 1-vinylimidazole (R1 to R3 in General Formula (2) are all hydrogen atoms)]
114 g of 1- (2-hydroxyethyl) imidazole (purity 98%, 1 mol, expected boiling point at normal pressure 316.5 ± 25 ° C.), 11 g of glycerin (boiling point 290 ° C. at normal pressure) and 16.8 g of potassium hydroxide (0.3 mol) was weighed into a 200 mL round bottom flask and subjected to a dehydration reaction at an internal temperature of 220 ° C. and 27 hPa. By condensing the gas generated by the progress of the reaction, a liquid containing 89 g of 1-vinylimidazole (0.95 mol, boiling point 196 ° C. at normal pressure) and water was obtained. Quantitative descriptions regarding raw materials, specific solvents and products are summarized in Table 1.
The obtained liquid was further rectified at a reflux ratio of 5 and a degree of vacuum of 40 hPa in a distillation apparatus equipped with a column packed with McMahon 15 cm. As a result, the top temperature was 90 ° C. and the purity was 99.9%. -85 g (0.90 mol) of vinylimidazole was obtained as a colorless liquid. That is, the yield (raw material utilization) of 1-vinylimidazole obtained by rectification relative to the raw material (1- (2-hydroxyethyl) imidazole) is 90%.

[Production of 2-methyl-1-vinylimidazole (R1 in General Formula (2) is a methyl group, and R2 and R3 are both hydrogen atoms)]
In Example 1, except that the raw material was changed to 128.7 g (purity 98%, 1 mol) of 2-methyl-1- (2-hydroxyethyl) imidazole and the amount of glycerin used as the specific solvent was changed to 13 g. In the same manner, a liquid containing 97.1 g of 2-methyl-1-vinylimidazole (0.89 mol, expected boiling point of 215.6 ± 23 ° C. at normal pressure) and water was obtained. Quantitative descriptions regarding raw materials, specific solvents and products are summarized in Table 1.
The obtained liquid was further rectified at a reflux ratio of 5 and a vacuum of 13 hPa in a distillation apparatus equipped with a column packed with McMahon 15 cm. As a result, the top temperature was 86 ° C. and a purity of 99.3% 2 was obtained. -93 g (0.85 mol) of methyl-1-vinylimidazole was obtained as a colorless liquid. That is, the yield (raw material utilization rate) with respect to the raw material (2-methyl-1- (2-hydroxyethyl) imidazole) of 2-methyl-1-vinylimidazole obtained by rectification is 85%.

[Production of 1-vinylimidazole]
In Example 1, the same operation was performed except that the liquid paraffin was changed to 11 g (boiling point of 300 ° C. or higher at normal pressure), and 88.4 g of 1-vinylimidazole (0.94 mol, boiling point of 196 ° C. at normal pressure). ) And water were obtained. Quantitative descriptions regarding raw materials, specific solvents and products are summarized in Table 1.

[Production of 1-vinylimidazole]
In Example 1, the same operation was performed except that glycerin as a specific solvent was changed to 11 g (decomposition point 350 ° C. or higher) of EMITFSI [1-ethyl-3-methylimidazolium bis (trifluoromethanesulfonyl) imide]. A liquid containing 89 g of 1-vinylimidazole (0.95 mol, boiling point 196 ° C. at normal pressure) and water was obtained. Quantitative descriptions regarding raw materials, specific solvents and products are summarized in Table 1.

[Production of 1-vinylimidazole including production process of 1- (2-hydroxyethyl) imidazole]
A 500 mL four-necked flask equipped with a stirrer and a dropping funnel was charged with 61.1 g (1.0 mol) of monoethanolamine and cooled to 25 ° C. while cooling 81.2 g (1.0 mol) of a 37% aqueous formaldehyde solution. And stirred for 1 hour. After confirming the formation of the imine compound by liquid chromatography, the temperature was raised to 80 ° C., and 145.1 g (1.0 mol) of 40% aqueous glyoxal solution and 60.8 g (1.0 mol) of 28% aqueous ammonia solution were simultaneously added dropwise ( The dropping time was 2 hours), and the mixture was aged at 80 ° C. for 1 hour. After completion of the reaction, water and remaining raw materials were distilled off to obtain an oily reaction product. The reaction product contained 98% 1- (2-hydroxyethyl) imidazole and 2% imidazole.

Subsequently, 20 g of glycerin (boiling point 290 ° C. at normal pressure) and 16.8 g (0.3 mol) of potassium hydroxide were added, and a dehydration reaction was performed at an internal temperature of 220 ° C. and 27 hPa. By condensing the gas generated by the progress of the reaction, a liquid containing 85 g of 1-vinylimidazole (0.9 mol, boiling point 196 ° C. at normal pressure) and water was obtained.
The obtained liquid was further rectified at a reflux ratio of 5 and a degree of vacuum of 40 hPa in a distillation apparatus equipped with a column packed with McMahon 15 cm. As a result, the top temperature was 90 ° C. and the purity was 99.8%. -81 g (0.86 mol) of vinylimidazole was obtained as a colorless liquid.

Comparative Example 1

  In Example 1, the same operation was performed except that glycerin was not added. However, since the viscosity increased during the reaction and stirring became impossible, the operation was interrupted. The obtained distillate contained 70 g (0.75 mol) of 1-vinylimidazole.

  The vinylimidazole compound obtained by the present invention can be used, for example, as a curing agent for epoxy resin, a reaction accelerator for urethane resin, a raw material monomer for UV curable resin or acrylic resin. Moreover, these resins can be widely used for adhesives, hair care agents, cleaning agents, and the like.

Claims (2)

A method for producing a vinylimidazole compound represented by the following general formula (2) by subjecting a hydroxyethyl group-containing imidazole compound represented by the following general formula (1) to a dehydration reaction in the presence of a dehydrating agent. ,
A method for producing a vinylimidazole compound, comprising performing the dehydration reaction in a solvent having a boiling point at normal pressure of 30 ° C. or more higher than a boiling point at normal pressure of the vinylimidazole compound.

[In formula, R1-R3 is respectively independently a hydrogen atom, a C1-C4 alkyl group, or a C1-C4 alkoxy group. ]

[In formula, R1-R3 is respectively independently a hydrogen atom, a C1-C4 alkyl group, or a C1-C4 alkoxy group. ]   The method for producing a vinylimidazole compound according to claim 1, wherein the dehydrating agent is an alkali metal hydroxide.