CN113501788A - Synthesis method of N-cyanoethylimidazole compound - Google Patents
Synthesis method of N-cyanoethylimidazole compound Download PDFInfo
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- CN113501788A CN113501788A CN202110684476.1A CN202110684476A CN113501788A CN 113501788 A CN113501788 A CN 113501788A CN 202110684476 A CN202110684476 A CN 202110684476A CN 113501788 A CN113501788 A CN 113501788A
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- cyanoethylimidazole
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- imidazole
- acrylonitrile
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- C—CHEMISTRY; METALLURGY
- C07—ORGANIC CHEMISTRY
- C07D—HETEROCYCLIC COMPOUNDS
- C07D233/00—Heterocyclic compounds containing 1,3-diazole or hydrogenated 1,3-diazole rings, not condensed with other rings
- C07D233/54—Heterocyclic compounds containing 1,3-diazole or hydrogenated 1,3-diazole rings, not condensed with other rings having two double bonds between ring members or between ring members and non-ring members
- C07D233/56—Heterocyclic compounds containing 1,3-diazole or hydrogenated 1,3-diazole rings, not condensed with other rings having two double bonds between ring members or between ring members and non-ring members with only hydrogen atoms or radicals containing only hydrogen and carbon atoms, attached to ring carbon atoms
Abstract
The invention provides a method for synthesizing an N-cyanoethylimidazole compound, which takes imidazole and derivatives thereof as raw materials and acrylonitrile as a Michael addition acceptor to synthesize the N-cyanoethylimidazole compound in a one-step method with high yield and high selectivity in an atmosphere without catalyst, solvent and air. The method is simple to operate, environment-friendly, economical, practical, stable in performance and wide in product market; no special post-treatment is needed in the reaction, no by-product is generated, and the method is suitable for industrial production.
Description
Technical Field
The invention relates to a green synthesis method of imidazole compounds, in particular to a method for synthesizing N-cyanoethyl imidazole compounds by taking imidazole derivatives as raw materials through Michael addition reaction, belonging to the technical field of green organic synthesis.
Background
In recent years, the wide application of epoxy resin curing materials has made the research of related curing agents become a hot research of chemists. Imidazole derivatives are a good epoxy resin curing agent, but imidazole compounds are generally solid at room temperature, have the problems of uneven mixing and the like in use, and have tertiary amine nitrogen atoms and active hydrogen in molecules, so that the curing reaction is more complex. The imidazole containing active hydrogen is improved into single tertiary amine imidazole through reaction, so that the structure of a cured product is more regular, and the thermal deformation temperature of the cured product is increased. In order to improve the usability of the imidazole compound, the N-cyanoethyl imidazole compound is synthesized by the Michael addition reaction of acrylonitrile and imidazole containing active hydrogen and derivatives thereof, and the product is liquid or solid with lower melting point at normal temperature, so that the use is more convenient; due to the unique structural characteristics, the epoxy resin curing agent is widely applied to epoxy resin curing agents, accelerators, drug intermediates and the like, and has wide application in organic synthesis. The structural formula of the N-cyanoethylimidazole compound is shown as the following figure:
wherein R is1Hydrogen, alkyl, cycloalkyl, aryl, aliphatic; r2、R3Hydrogen, alkyl, cycloalkyl, aryl, aliphatic, nitro, hydroxymethyl, and the like.
In view of this, a number of synthetic methods have been used for the preparation of such compounds. The literature "Zhao Feiming, synthesis and composition analysis of cyanoethylimidazole compound, aerospace material technology" uses benzene as solvent, 2-methylimidazole and acrylonitrile as raw material, and makes them produce reaction to synthesize cyanoethyl compound. Patent CN103980204 reports that quaternary ammonium salt ionic liquid catalyzes acrylonitrile and imidazole compound to prepare N-cyanoethylimidazole at room temperature, the catalyst dosage is up to 40%, after the reaction is finished, the catalyst needs to be recovered by extraction, and the product is purified by column chromatography, which is not suitable for large-scale production. Patent CN103450090 reports that under the condition of ethanol as solvent, imidazole and acrylonitrile react to generate N-cyanoethylimidazole, and after the reaction is finished, the solvent needs to be removed by concentration under reduced pressure, which increases production cost. Similarly, patents CN103450090 and CN106575791 respectively report the reaction of imidazole and acrylonitrile to form N-cyanoethylimidazole in the presence of ethyl acetate and methanol as solvents. The reactions involving the organic solvent and the catalyst all need further post-treatment, which not only increases the production cost, but also brings certain pollution to the environment. The compound has large demand and considerable economic benefit, and a novel simple, efficient and green synthesis method is developed and has important application value.
Disclosure of Invention
The invention aims to provide a synthetic method of cyanoethyl imidazole compounds, which has the advantages of simple process, convenient operation, low cost, environmental protection and the like, aiming at the defects of the prior art.
A synthetic method of an N-cyanoethylimidazole compound is characterized in that an imidazole derivative is used as a raw material, acrylonitrile is used as a Michael acceptor, the reaction is carried out in an air atmosphere, and the reaction is carried out for 3-16 hours under the condition that the temperature is 50-100 ℃ by stirring to obtain the N-cyanoethylimidazole compound. The reaction formula is shown as follows,
further, the structural formula of the imidazole derivative is as follows:
wherein R is1Is hydrogen, alkyl, cycloalkyl, aryl or aliphatic; r2Is hydrogen, alkyl, cycloalkyl, aryl, aliphatic, nitro or hydroxymethyl, R3Hydrogen, alkyl, cycloalkyl, aryl, aliphatic, nitro or hydroxymethyl.
Furthermore, the molar ratio of the imidazole derivative to acrylonitrile is 1: 1.1-1.5.
Further, the reaction temperature is 70-100 ℃.
Further, the reaction time is 5 to 10 hours.
The imidazole derivative is insoluble in acrylonitrile under the condition of room temperature, so that the prior art mostly adopts a mode of catalyst or solvent addition to enable the reaction to be carried out in a uniform liquid phase, and the inventor researches and discovers that when the reaction temperature reaches 50 ℃, the imidazole and the derivative thereof and the acrylonitrile just start to react, the system is converted into a uniform liquid state along with the reaction, and the reaction can be carried out under the autocatalysis condition because the imidazole compound is alkaline, so the inventor successfully synthesizes the N-cyanoethyl imidazole compound with high purity and high yield by adopting a synthesis method without adding any organic solvent and catalyst.
The synthesized product is detected by nuclear GC and IR, and is an N-cyanoethylimidazole compound with the purity of more than or equal to 98.5 percent, and the yield of the N-cyanoethylimidazole compound is more than or equal to 97 percent.
Compared with the prior art, the method has the following advantages:
1. the N-cyanoethylimidazole compound is prepared by taking imidazole and derivatives thereof as raw materials and acrylonitrile as a Michael acceptor in a system without a catalyst and a solvent at 50-100 ℃. The imidazole raw material involved in the operation process is an industrial raw material, has stable performance and high use safety, and is green and environment-friendly;
2. the invention adopts a one-step method, directly mixes the imidazole derivative and acrylonitrile, does not need to drop acrylonitrile, and simply and efficiently synthesizes the N-cyanoethylimidazole compound.
3. The reaction is carried out in the air atmosphere, no solvent is needed in the reaction, the post-treatment is simple, the environmental pollution is small, and the method is green and environment-friendly and is suitable for industrial production.
Drawings
FIG. 1 is a GC spectrum of 1-cyanoethylimidazole synthesized in example 1 of the present invention.
FIG. 2 is an IR spectrum of 1-cyanoethylimidazole synthesized in example 1 of the present invention.
FIG. 3 is a GC spectrum of 1-cyanoethyl-2-methylimidazole, a synthesized product of example 2 of the present invention.
FIG. 4 is an IR spectrum of 1-cyanoethyl-2-methylimidazole synthesized in example 2 of the present invention.
FIG. 5 is a GC spectrum of 1-cyanoethyl-2-phenylimidazole, a synthesized product of example 3 of the present invention.
FIG. 6 is an IR spectrum of 1-cyanoethyl-2-phenylimidazole, a synthesized product of example 3 of the present invention.
Detailed Description
The process for synthesizing cyanoethylimidazole compounds according to the present invention is further illustrated by the following specific examples.
Example 1: synthesis of 1-cyanoethylimidazole
3.40 g of imidazole (50mol) was added to a 50mL round-bottom flask, and 3.18 g of acrylonitrile (60mol) was added, and the reaction was stirred at 70 ℃ for 7 hours. After the reaction is detected by GC, the unreacted acrylonitrile is removed by vacuum concentration, and the target product (pale yellow liquid) 1-cyanoethylimidazole can be obtained, wherein the yield is 97 percent, and the purity is 99.7 percent. The synthesis reaction formula is as follows:
IR data and analysis of product 1-cyanoethylimidazole: as can be seen from FIG. 1, 3300-2800 cm-1The large absorption peak is a typical characteristic of the existence of imidazole ring, and the wave number of the cyano absorption peak is reduced to 2230cm by the conjugation of the carbon-carbon double bond and the cyano in acrylonitrile-1The non-conjugated cyano absorption peak appears in 2260-2240 cm-1Within the range. Therefore 2253cm in FIG. 1-1The absorption peak of the cyano group is the absorption peak of aliphatic saturated cyanogen generated after the reaction of acrylonitrile and imidazole.
The GC and IR spectrum of the product is shown in FIG. 1.
Example 2: synthesis of 1-cyanoethyl-2-methylimidazole
4.1 g of 2-methylimidazole (50mol) was charged into a 50mL round-bottom flask, and 3.18 g of acrylonitrile (60mol) was added, and the reaction was stirred at 90 ℃ for 5 hours. After GC detection reaction, vacuum concentration is carried out to obtain the target product (pale yellow liquid) 1-cyanoethyl-2-methylimidazole, the yield is 97 percent, and the purity is more than or equal to 98 percent. The synthesis reaction formula is as follows:
the GC and IR spectrum of the product is shown in FIG. 2.
Example 3: synthesis of 1-cyanoethyl-2-phenylimidazole
2.88 g of 2-phenylimidazole (20mol) was added to a 50mL round-bottom flask, and 1.38 g of acrylonitrile (26mol) was added, and the reaction was stirred at 100 ℃ for 8 hours. After GC detection reaction, vacuum concentration is carried out, and the target product (pale yellow liquid) 1-cyanoethyl-2-phenylimidazole can be obtained, wherein the yield is 97%, and the purity is 98.8%. The synthesis reaction formula is as follows:
the GC and IR spectrum of the product is shown in FIG. 3.
Example 4: synthesis of 1-cyanoethyl-2-ethyl-4-methylimidazole
3.3 grams of 2-ethyl-4-methylimidazole (30mol) was added to a 50mL round bottom flask, and 1.91 grams of acrylonitrile (36mol) was added, followed by a quantity of deionized water, and the reaction stirred at 80 deg.C for 8 hours. After GC detection reaction, vacuum concentration is carried out, and the target product (pale yellow liquid) 1-cyanoethyl-2-ethyl-4-methylimidazole can be obtained, wherein the yield is 97%, and the purity is 98.4%. The synthesis reaction formula is as follows:
example 5: synthesis of 1-cyanoethyl-2, 4-dimethylimidazole
2.88 g of 2, 4-dimethylimidazole (30mol) was added to a 50mL round-bottom flask, and 1.91 g of acrylonitrile (36mol) was added, and the reaction was stirred at 85 ℃ for 10 hours. After GC detection reaction, vacuum concentration is carried out, and the target product (pale yellow liquid) 1-cyanoethyl-2, 4-dimethyl imidazole can be obtained, wherein the yield is 97%, and the purity is 98.1%. The synthesis reaction formula is as follows:
the above examples are only for illustrating the present invention and not for limiting the technical solutions described in the present invention, and any person skilled in the art can easily make component changes or substitutions after the present invention is disclosed, and all technical modifications without departing from the present invention shall be covered by the scope of the claims of the present invention.
Claims (7)
1. A synthesis method of an N-cyanoethylimidazole compound is characterized in that imidazole and derivatives thereof are used as raw materials, acrylonitrile is used as a Michael acceptor, and the N-cyanoethylimidazole compound is obtained through reaction in an air atmosphere.
2. The method for synthesizing N-cyanoethylimidazole compounds according to claim 1, wherein the structural formula of imidazole and its derivatives is as follows:
wherein R is1Is hydrogen, alkyl, cycloalkyl, aryl or aliphatic; r2Is hydrogen, alkyl, cycloalkyl, aryl, aliphatic, nitro or hydroxymethyl, R3Hydrogen, alkyl, cycloalkyl, aryl, aliphatic, nitro or hydroxymethyl.
3. The method for synthesizing the N-cyanoethylimidazole compound as claimed in claim 1, wherein the molar ratio of the imidazole derivative to acrylonitrile is 1: 1.1-1.5.
4. The method for synthesizing N-cyanoethylimidazole compounds according to claim 1, wherein the reaction temperature is 50-100 ℃.
5. The method for synthesizing N-cyanoethylimidazole compounds according to claim 4, wherein the reaction temperature is 70-100 ℃.
6. The method for synthesizing N-cyanoethylimidazole compounds according to claim 1, wherein the reaction time is 3-16 hours.
7. The method for synthesizing N-cyanoethylimidazole compounds according to claim 6, wherein the reaction time is 5-10 hours.
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Citations (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN102906133A (en) * | 2010-05-18 | 2013-01-30 | 3M创新有限公司 | Polymerizable ionic liquid compositions |
| CN106279118A (en) * | 2016-08-12 | 2017-01-04 | 江苏康乐新材料科技有限公司 | One prepares the method for 2,4 diaminourea 6 [2 (2 methyl 1 imidazoles) ethyl] 1,3,5 triazines |
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Patent Citations (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN102906133A (en) * | 2010-05-18 | 2013-01-30 | 3M创新有限公司 | Polymerizable ionic liquid compositions |
| CN106279118A (en) * | 2016-08-12 | 2017-01-04 | 江苏康乐新材料科技有限公司 | One prepares the method for 2,4 diaminourea 6 [2 (2 methyl 1 imidazoles) ethyl] 1,3,5 triazines |
Non-Patent Citations (2)
| Title |
|---|
| HENRIK LUND等: "Synthesis and Structure of Ionic Liquids Containing the [Al(OC6H4CN)4]–Anion", 《Z. ANORG. ALLG. CHEM.》 * |
| KODOLITSCH, KATHARINA等: "Solvent- and Catalyst-Free Aza-Michael Addition of Imidazoles and Related Heterocycles", 《EUROPEAN JOURNAL OF ORGANIC CHEMISTRY》 * |
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