A method for preparing 2,4-diamino-6-[2-(2-methyl-1-imidazole)ethyl]-1,3,5-triazine

Abstract

The present invention relates to a method for preparing 2,4-diamino-6-[2-(2-methyl-1-imidazole)ethyl]-1,3,5-triazine, comprising the following steps: (1) mixing an imidazole raw material and acrylonitrile and heating and refluxing the mixture to obtain an intermediate; (2) continuously adding dicyandiamide, a high boiling point solvent and a catalyst to the reaction system of step (1), heating and stirring the mixture for reaction, and after the reaction is completed, removing the solvent by reduced pressure distillation, filtering, washing and drying to obtain 2,4-diamino-6-[2-(2-methyl-1-imidazole)ethyl]-1,3,5-triazine; the high boiling point solvent in the step (2) is one or more of ethanol, toluene, chloroform, isopropanol, tert-butyl alcohol and dimethyl sulfoxide; and the heating temperature in the step (2) is 80-150° C. The present invention clarifies a two-step synthesis route from raw materials to the synthesis of a target product and the control of reaction conditions, and solves the problem of low yield of products in the prior art.

Description

Technical Field

[0001] The invention belongs to the technical field of preparation of nitrogen heterocyclic compounds, and particularly relates to a method for preparing 2,4-diamino-6-[2-(2-methyl-1-imidazole)ethyl]-1,3,5-triazine. Background Art

[0002] Nitrogen heterocyclic compounds, especially azoles and triazines, are widely used in gas generating agents, solid propellants, pyrotechnic materials and other fields due to their high density, positive heat generation and high stability. They also show important value in materials science, such as ink additives. Although such compounds have great application potential, the synthesis technology reports for specific structural compounds are relatively scarce.

[0003] CN106279118A describes a method for preparing 2,4-diamino-6-[2-(2-methyl-1-imidazole)ethyl]-1,3,5-triazine, which uses 2-methylimidazole to react with acrylonitrile to generate an intermediate, which is then cyclized with dicyandiamide to obtain the target product. However, the method has the problem of unclear reaction conditions in the key cyclization step, resulting in the inability to stably obtain the expected product.

[0004] KR100423020B1 also describes a method for preparing 2,4-diamino-6-[2-(2-methyl-1-imidazole)ethyl]-1,3,5-triazine, the main feature of which is in-situ generation without generating organic waste liquid. However, the reaction temperature used in this method is 60-90°C, the reaction temperature of the two-step synthesis is low, and the synthesis efficiency is insufficient.

[0005] Therefore, the inventors found that when synthesizing 2,4-diamino-6-[2-(2-methyl-1-imidazole)ethyl]-1,3,5-triazine in the prior art, the synthesis conditions were too simplified, which made it difficult to reproduce in actual operation. In addition, there were problems such as low reaction temperature and low product yield, which limited its further development and application. Summary of the invention

[0006] The technical problem to be solved by the present invention is to provide a method for preparing 2,4-diamino-6-[2-(2-methyl-1-imidazole)ethyl]-1,3,5-triazine, which clarifies a two-step synthesis route from raw materials to the synthesis of the target product and the control of reaction conditions, and solves the problem of low yield of products in the prior art.

[0007] The present invention provides a method for preparing 2,4-diamino-6-[2-(2-methyl-1-imidazole)ethyl]-1,3,5-triazine, comprising the following steps:

[0008] (1) mixing an imidazole raw material and acrylonitrile and heating them under reflux to react to obtain an intermediate;

[0009] (2) adding dicyandiamide, a high boiling point solvent and a catalyst to the reaction system of step (1), heating and stirring to react, and after the reaction is completed, removing the solvent by distillation under reduced pressure, filtering, washing and drying to obtain 2,4-diamino-6-[2-(2-methyl-1-imidazole)ethyl]-1,3,5-triazine;

[0010] The high boiling point solvent in step (2) is one or more of ethanol, toluene, chloroform, isopropanol, tert-butyl alcohol and dimethyl sulfoxide; the heating temperature in step (2) is 80-150°C.

[0011] Preferably, the imidazole raw material in step (1) is 2-methylimidazole.

[0012] Preferably, the molar ratio of the imidazole raw material to acrylonitrile in step (1) is 1:1-1.2.

[0013] Preferably, the heating temperature in step (1) is 80-90°C.

[0014] Preferably, the intermediate in step (1) is 1-cyanoethyl-2-methylimidazole.

[0015] Preferably, the mass ratio of the intermediate, dicyandiamide and high boiling point solvent in step (2) is 1:1.1-2:1-5.

[0016] Preferably, the high boiling point solvent in step (2) is dimethyl sulfoxide.

[0017] Preferably, the heating temperature in step (2) is 120-150°C.

[0018] Preferably, the catalyst in step (2) is one or more of sodium hydroxide, potassium hydroxide, methyl magnesium bromide, sodium hydride, potassium hydride, sodium ethoxide, potassium tert-butoxide, 2-methoxyethanol, potassium carbonate, and ammonia.

[0019] Preferably, the mass ratio of the catalyst to the solvent in step (2) is 1:50-500.

[0020] The reaction equation of the present invention is as follows:

[0021] .

[0022] Beneficial Effects

[0023] The present invention clarifies a two-step synthesis route from raw materials to synthesized target products and the control of reaction conditions, while solving the problem of low yield of products in the prior art; the present invention uses a solvent with a higher boiling point in the preparation process, which on the one hand improves reaction stability, shortens reaction time, and reduces the generation of by-products; on the other hand, the introduction of a recyclable organic solvent and a higher reaction temperature can increase the contact probability of reactants and increase the reaction yield, and has good application prospects. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 To prepare the H 1 NMR spectrum.

[0025] Figure 2 HPLC spectrum for the preparation of 2,4-diamino-6-[2-(2-methyl-1-imidazole)ethyl]-1,3,5-triazine. DETAILED DESCRIPTION

[0026] The present invention will be further described below in conjunction with specific embodiments. It should be understood that these embodiments are only used to illustrate the present invention and are not intended to limit the scope of the present invention. In addition, it should be understood that after reading the content taught by the present invention, those skilled in the art can make various changes or modifications to the present invention, and these equivalent forms fall within the scope limited by the appended claims of the application equally.

[0027] In the following examples, 2-methylimidazole, acrylonitrile, intermediates and high boiling point solvents are all expressed in parts by mass;

[0028] Example 1

[0029] (1) Place 1 part of 2-methylimidazole and 2 parts of acrylonitrile in a three-necked flask and reflux at 80°C for 6 hours to obtain the intermediate 1-cyanoethyl-2-methylimidazole.

[0030] (2) Step (1) Add 2 parts of dicyandiamide and 2 parts of ethanol to the reaction flask, and add 1phr of the catalyst KOH as a solvent, heat to 80°C, stir at this temperature for 6 hours, and as the reaction proceeds, solids are continuously precipitated. After the reaction is completed, remove the solvent by distillation under reduced pressure, add hot water, stir evenly, filter while hot, cool and crystallize the product, filter to obtain a solid, wash three times with pure water, and dry to obtain the target product, which is characterized by HPLC and HNMR. The yield of this embodiment is 80% and the purity is 97%. (HNMR determines the substance, HPLC characterizes the purity, and the yield can be obtained by calculation)

[0031] Example 2

[0032] (1) Same as Example 1.

[0033] (2) Step (1) Add 2 parts of dicyandiamide and 2 parts of dimethyl sulfoxide to the reaction flask, and add 1phr of the solvent amount of catalyst KOH, heat to 80°C, stir at this temperature for 6 hours, and as the reaction proceeds, solids are continuously precipitated. After the reaction is completed, remove the solvent by distillation under reduced pressure, add hot water and stir evenly, filter while hot, cool and crystallize the product, filter to obtain a solid, wash three times with pure water, and dry to obtain the target product, which is characterized by HPLC and HNMR. The yield of this example is 85% and the purity is 99%.

[0034] Example 3

[0035] (1) Same as Example 1.

[0036] (2) Step (1) Add 2 parts of dicyandiamide and 2 parts of dimethyl sulfoxide to the reaction flask, and add 1phr of the solvent amount of the catalyst KOH, and heat to 130°C. Stir at this temperature for 3 hours. As the reaction proceeds, solids are continuously precipitated. After the reaction is completed, the solvent is removed by distillation under reduced pressure, hot water is added and stirred evenly, filtered while hot, cooled and crystallized to precipitate the product, filtered to obtain a solid, washed three times with pure water, and dried to obtain the target product, which is characterized by HPLC and HNMR. The yield of this example is 97% and the purity is 99%.

[0037] refer to Figure 1 , H of the product of Example 3 1 NMR (CDCL3) showed: at the abscissa 1.25 (methyl H connected to imidazole, single peak), at the abscissa 1.52 (methylene H connected to two rings, single peak), it was shown that the target product 2,4-diamino-6-[2-(2-methyl-1-imidazole)ethyl]-1,3,5-triazine was prepared.

[0038] refer to Figure 2 As shown in the HPLC spectrum of the product of Example 3, the peak area of ​​the main peak at 5.9 min accounts for 99.9%, indicating that there are few by-products and high purity.

[0039] Comparison of Examples 1 to 3 of the present invention shows that the present invention improves the use of solvents and thereby increases the reaction temperature of the synthesis step (2), thereby significantly improving the yield of preparing 2,4-diamino-6-[2-(2-methyl-1-imidazole)ethyl]-1,3,5-triazine, and further improving the purity of the product, which plays an important role in the development and application of 2,4-diamino-6-[2-(2-methyl-1-imidazole)ethyl]-1,3,5-triazine.

Claims

1. A method for preparing 2,4-diamino-6-[2-(2-methyl-1-imidazole)ethyl]-1,3,5-triazine, comprising the following steps: (1) mixing an imidazole raw material and acrylonitrile and heating them under reflux to react to obtain an intermediate; (2) adding dicyandiamide, a high boiling point solvent and a catalyst to the reaction system of step (1), heating and stirring to react, and after the reaction is completed, removing the solvent by distillation under reduced pressure, filtering, washing and drying to obtain 2,4-diamino-6-[2-(2-methyl-1-imidazole)ethyl]-1,3,5-triazine; The high boiling point solvent in step (2) is one or more of ethanol, toluene, chloroform, isopropanol, tert-butyl alcohol and dimethyl sulfoxide; the heating temperature in step (2) is 80-150°C.

2. The method according to claim 1, characterized in that: The imidazole raw material in step (1) is 2-methylimidazole.

3. The method according to claim 1, characterized in that: The molar ratio of the imidazole raw material to acrylonitrile in the step (1) is 1:1-1.

2.

4. The method according to claim 1, characterized in that: The heating temperature in step (1) is 80-90°C.

5. The method according to claim 1, characterized in that: The intermediate in step (1) is 1-cyanoethyl-2-methylimidazole.

6. The method according to claim 1, characterized in that: The mass ratio of the intermediate, dicyandiamide and high boiling point solvent in the step (2) is 1:1.1-2:1-5.

7. The method according to claim 1, characterized in that: The high boiling point solvent in step (2) is dimethyl sulfoxide.

8. The method according to claim 7, characterized in that: The heating temperature in step (2) is 120-150°C.

9. The method according to claim 1, characterized in that: The catalyst in step (2) is one or more of sodium hydroxide, potassium hydroxide, methyl magnesium bromide, sodium hydride, potassium hydride, sodium ethoxide, potassium tert-butoxide, 2-methoxyethanol, potassium carbonate, and ammonia.

10. The method according to claim 7, characterized in that: The mass ratio of the catalyst to the high boiling point solvent in step (2) is 1:50-500.

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