JPS63208578A - Production of 4-methylimidazoles - Google Patents

Abstract

PURPOSE:To obtain 4-methylimidazoles on an industrial scale at a low cost in high yield, by reacting an aldehyde with ammonia in an aqueous medium, adding methylglyoxal to the reaction system and continuing the reaction. CONSTITUTION:An aldehyde and ammonia are introduced into an aqueous medium and are made to react with each other preferably at about 15-30 deg.C. Subsequently, methylglyoxal is charged to the system (preferably by dripping) and the reaction is continued at 15-30 deg.C to obtain 4-methylimidazole. The compound is useful as an intermediate for organic chemicals such as various pharmaceuticals, agricultural chemicals, etc., and as an epoxy resin hardener.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application] The present invention relates to a method for producing 4-methylimidazole with good yield.

[Prior Art 1] A method for producing 4-methylimidazole by reacting methylimidazole, formaldehyde and ammo 7 is known.

Problems to be Solved by the Invention 1 However, such a reaction has a low yield of the target product, and problems remain in industrial implementation. As one of such measures, 1. It has been proposed to use ammonium salts such as ammonium sulfate, but in this case, the by-product acid forms a salt with 4-methylimidazole, so a post-treatment step is required, and this is not necessarily advantageous as an industrial production method. It's hard to say that there is.

[Means for Solving the Problems 1] Based on the knowledge that it is more advantageous to use Ammo 7 as an industrial production method, the present inventors have realized that the desired product can be produced with a higher yield than conventional methods. As a result of extensive research to develop a method for producing methylglyoxal, we found that when reacting methylglyoxal, an aldehyde with 1 to 3 carbon atoms, and ammo7 in an aqueous medium, first the aldehyde and ammour were reacted, and then methyl glyoxal was added to the system. It was discovered that 4-methylimidazole can be produced in good yield when glyoxal is supplied and the reaction is continued, and the present invention has been completed.

In the present invention, as described above, the supply means for each raw material has a v
The purpose cannot be achieved by supplying methods other than those specified in the present application, such as charging such raw materials in bulk.

The aldehyde having 1 to 3 carbon atoms used in the present invention is formaldehyde and acetofludehyde V1 propionaldehyde.

The amounts of methylglyoxal, aldehyde V, and ammonia used in the reaction were 1,071,0 to 1.5/molar ratio.
2, θ~2.5 is appropriate.

The reaction is carried out in an aqueous medium, but a small amount of an organic solvent can also be used if necessary.

In carrying out the reaction, first, an aldehyde and 7 ammonia are supplied into an aqueous medium and the two are allowed to react.

Ammonia (usually 7 mm, 7 water) may be charged, and then aldehyde may be added dropwise or all at once.

The reaction temperature during such reaction is 5 to 40°C,
The reaction time is preferably about 15 to 30°C.
About 1 to 2.0 hours is preferable.

Subsequently, methylglyoxal is charged into the system and the reaction is continued. Although the preparation method may be batch preparation, it is preferable to use drip preparation.

The reaction temperature at this time is 5 to 60°C, preferably 15 to 30°C.
The preferred reaction time is approximately 1.0 to 6.0 hours.

The reaction is completed by aging for about 0.5 to 2.0 hours after the completion of the preparation.

The reaction product liquid is then subjected to distillation to remove volatile components, and then the resulting concentrated liquid is rectified to remove the target product.

The obtained target product is subjected to known purification such as activated carbon treatment, if necessary.

[Function] The 4-methylimidazole obtained in the present invention is useful as an intermediate for organic chemicals such as various medicines and agricultural chemicals, or as a curing agent for epoxy resins.

[Example] Next, the method of the present invention will be explained in more detail with reference to Examples.

Example 1 23Bg of 12.5% 7mm water (1,
75 mol), and 56.8 g (0.98 mol) of propionaldehyde was charged in 5 minutes while keeping the temperature at 20°C, followed by 126 g of a 40% aqueous methylglyoxal solution
g (0.7 mol) was added dropwise over 2 hours. After the completion of the 0 dropwise addition, the mixture was aged at the same temperature for 30 minutes.

The obtained reaction product liquid was concentrated with a tally evaporator, and the yield of the obtained 2-ethyl-4-methylimidazole was 80% (purity 99%) based on methylglyoxal.
)Met.

Example 2 238 g (1.75 mol) of 12.5% 7-moni-7 water,
56.8 g (0,70 mol) of 37% formaldehyde and 126 g (0,70 mol) of 40% methylglyoxal
The same method as in Example 1 was carried out using 70 mol).

The concentrated solution was subjected to rectification and a 150° C./30 Torr fraction was collected.

The yield of the obtained 4-methylimidazole was 75% (purity 98.5%).

Example 3 The same reaction as in Example 1 was carried out except that 33.9 g (0.77 mol) of 7cetaldehyde was used in place of propionaldehyde.

The concentrated liquid was subjected to rectification, and a 150° C./20 Torr fraction was collected.

The yield of 2,4-dimethylimidazole obtained was 80%.
(purity 98.5%).

Control Example: Put 105 g of water in a reaction vessel, heat it to 20°C, then add 10 sg (i, s 4 mol) of water and 40%
126 g (0.7 mol) of methylglyoxal and 65 g (1.12 mol) of propionaldehyde were simultaneously fed, and the reaction was carried out for 2 hours.

When the resulting reaction product liquid was subjected to streak zero analysis, the yield of 2-ethyl-4-methylimidazole was only 60%.

[Effects of the Invention] In the present invention, 4-methylimidazole can be produced in good yield by reacting aldehyde and ammonia in advance and then reacting methylglyoxal.

Claims (1)

[Claims] When producing 4-methylimidazole by reacting methylglyoxal, an aldehyde having 1 to 3 carbon atoms, and ammore in an aqueous medium, the aldehyde and ammore are first reacted, and then methylglyoxal is supplied to the system to carry out the reaction. A method for producing 4-methylimidazole, characterized in that the method is continued.