CN110845415B - Environment-friendly synthesis method of 2-ethyl-4-methylimidazole - Google Patents
Environment-friendly synthesis method of 2-ethyl-4-methylimidazole Download PDFInfo
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- CN110845415B CN110845415B CN201911080429.5A CN201911080429A CN110845415B CN 110845415 B CN110845415 B CN 110845415B CN 201911080429 A CN201911080429 A CN 201911080429A CN 110845415 B CN110845415 B CN 110845415B
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- 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
- C07D233/58—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 with only hydrogen atoms or radicals containing only hydrogen and carbon atoms, attached to ring nitrogen atoms
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Abstract
The invention discloses a green synthesis method of 2-ethyl-4-methylimidazole, belonging to the technical field of organic synthesis; the invention adopts low-toxicity methyl propionate and 1,2-propane diamine to generate aminopropyl propionamide at the temperature of 80 ℃ according to a proper reaction proportion, and then uses Guan Huansheng of aromatic hydrocarbon with water to prepare 2-ethyl-4-methylimidazoline in the presence of a catalyst; dehydrogenating 2-ethyl-4-methylimidazoline at 120-140 ℃ in the presence of pd/c catalyst to obtain 2-ethyl-4-methylimidazole; the method for preparing the 2-ethyl-4-methylimidazole avoids using high-toxicity propionitrile, high-pollution aldehyde and ammonia and a Raney nickel catalyst which is burnt in air and has high risk, does not generate waste ammonia in the production process, and belongs to an environment-friendly method for preparing the 2-ethyl-4-methylimidazole.
Description
Technical Field
The invention relates to a preparation method of environment-friendly 2-ethyl-4-methylimidazole, belonging to the technical field of organic synthesis.
Background
The 2-ethyl-4-methylimidazole is an epoxy resin curing agent with excellent performance. The epoxy resin is liquid at normal temperature, the dosage is less, the epoxy resin can be easily mixed with the epoxy resin, the mixture has long working life, and the curing temperature is not high; the cured product has excellent heat resistance, adhesiveness and insulativity, and is widely applied to the fields of adhesives, coatings, composite materials and the like. There are three main methods for producing 2-ethyl-4-methylimidazole: the first is aldehyde ammonia process, which adopts n-propyl aldehyde, water solution of acetone aldehyde and ammonia water as material to prepare 2-ethyl-4-methyl imidazole in one pot, and has low yield, complicated purification and produced great amount of aldehyde ammonia effluent incapable of being treated. The other is imidazoline dehydrogenation, which is to prepare 2-ethyl-4-methylimidazole with 1,2-propane diamine and propionitrile under the catalysis of sulfur and prepare 2-ethyl-4-methylimidazole through the catalytic dehydrogenation of raney nickel. The propionitrile in the method belongs to a highly toxic pipe product, the labor protection requirement is strict, a large amount of solid waste is generated by sulfur and sulfur-removing zinc powder, the ammonia gas discharged by the reaction pollutes the atmosphere, a large amount of impure ammonia-containing wastewater can be generated even if the ammonia gas is absorbed by water, and the operation risk is increased by using Raney nickel which spontaneously combusts when meeting air. Thirdly, cuprous salt is used as a catalyst, propionitrile and 2-aminopropionaldehyde diglycol are firstly reacted to generate an intermediate, alcohol and hydrochloric acid are then added to decompose the intermediate to generate 2-ethyl-4-methylimidazole, and the method not only uses virulent propionitrile and expensive 2-aminopropionaldehyde glycol, but also generates a large amount of wastewater in the acidolysis process. In conclusion, the existing preparation method of 2-ethyl-4-methylimidazole has the production difficulties of high toxicity, high pollution, operation danger and the like, and is also the reason that the price of 2-ethyl-4-methylimidazole is high.
Disclosure of Invention
The invention aims to provide a preparation method of 2-ethyl-4-methylimidazole, which abandons high-toxicity and dangerous raw materials, generates few three wastes in the production process and belongs to an environment-friendly preparation method.
In order to achieve the purpose, the technical scheme adopted by the invention is as follows:
methyl propionate and 1,2-propane diamine in proper proportion are subjected to reflux reaction to generate aminopropyl propionamide, a ring closing catalyst and aromatic hydrocarbon are added for dehydration and ring closing reaction to generate 2-ethyl-4-methylimidazoline, a pd/c catalyst is added for medium-temperature dehydrogenation reaction, and the 2-ethyl-4-methylimidazole is prepared by reduced pressure distillation after filtration. The preparation method does not use high-toxicity propionitrile, high-pollution aldehyde ammonia and flammable Raney nickel, and no waste ammonia is discharged in the reaction process;
the ratio of the methyl propionate to 1,2-propanediamine is 1:2 to 4 (molar ratio);
the reaction of the methyl propionate with 1,2-propanediamine is carried out under reflux (about 80 ℃);
the ring closing catalyst is active alumina or dibutyl tin oxide or a 5A molecular sieve;
the medium-temperature dehydrogenation reaction refers to dehydrogenation reaction at 120-140 ℃;
the aromatic hydrocarbon is toluene, xylene and trimethylbenzene;
the specifications of the palladium-carbon catalyst are 5% and 10%.
The invention adopts methyl propionate and 1,2-propane diamine in excess to react to generate aminopropyl propionamide firstly, and the purpose of 1,2-propane diamine in excess is to reduce the generation of dipropionamide by-product. The aminopropyl propionamide generates dehydration ring-closing reaction in the presence of a catalyst, and the released water molecules are azeotropically taken away by aromatic hydrocarbon, so that the reaction equilibrium is moved to the product. The yield of the ring-closing product, namely 2-ethyl-4-methylimidazoline, can reach over 90 percent. The dehydrogenation catalyst of imidazoline is Raney nickel as conventional catalyst, but the Raney nickel is spontaneously combusted when meeting air, which causes great hidden trouble to production, so that the invention adopts a relatively stable palladium-carbon catalyst as the dehydrogenation catalyst of imidazoline. Dehydrogenating 2-ethyl-4-methylimidazoline with palladium-carbon catalyst to obtain 2-ethyl-4-methylimidazole with yield over 80%. The method for preparing the 2-ethyl-4-methylimidazole has the advantages of high yield, non-toxic and non-dangerous raw materials, belonging to conventional chemical raw materials, and little discharge of three wastes in the production process, and belonging to an environment-friendly preparation process.
Detailed Description
The present invention is further illustrated by the following examples, which are provided only for illustrating the present invention and are not intended to limit the scope of the present invention.
Example 1
Putting 88g of methyl propionate and 222g of 1, 2-propane diamine into a flask, carrying out reflux reaction at 80 ℃ for 3 hours, adding 3g of dibutyltin oxide and 176g of trimethylbenzene, distilling out unreacted reactants with low boiling point at low temperature, heating to 180 ℃, carrying out reflux for 3 hours with water, and distilling off anhydrous components. Vacuum distillation is carried out, 102-112 ℃/2.0kpa of fraction is collected, 98g of 2-ethyl-4-methylimidazoline is prepared, and the yield is 87.5%.
Example 2
88g of methyl propionate and 296g of 1, 2-propanediamine are placed in a flask and refluxed for 3 hours at 80 ℃, unreacted substances are distilled off, and then, 5g of a 5A molecular sieve and 176g of toluene are added to carry out reflux reaction with water until anhydrous substances are distilled off. Finally, reduced pressure distillation is carried out, 102-112 ℃/2.0kpa fractions are collected, 92g of 2-ethyl-4-methylimidazoline is prepared, and the yield is 82%.
Example 3
Putting 88g of methyl propionate and 148g of 1, 2-propane diamine into a flask, carrying out reflux reaction for 3 hours at the temperature of 80 ℃, adding 3g of activated alumina and 176g of dimethylbenzene, distilling out unreacted reactants at low temperature, heating up, carrying out reflux dehydration reaction until anhydrous components are distilled out. Vacuum distillation is carried out, 102-112 ℃/2.0kpa fractions are collected, 101g of 2-ethyl-4-methylimidazoline is prepared, and the yield is 90%.
Example 4
112g of the thus-obtained 2-ethyl-4-methylimidazoline was taken in a flask, and 1.1g of a pd/c catalyst was added thereto in an amount of 10% by weight, and the mixture was slowly heated to 120 ℃ to conduct dehydrogenation reaction for about 6 hours until no bubble was released. Suction filtration and reduced pressure distillation are carried out, and 91g of fraction with the boiling point of 150-160 ℃/1.33kpa is collected, and the yield is 82.7%.
Example 5
112g of the 2-ethyl-4-methylimidazoline prepared above was taken, 2.2g of 5% pd/c catalyst was added, the mixture was slowly heated to 140 ℃ and the dehydrogenation reaction was continued for about 10 hours until no bubbles were released. Suction filtering, reduced pressure distillation, and collection of 95.5g fraction with boiling point of 150-160 deg.C/1.33 kpa, yield 86.8%.
Claims (1)
1. A synthetic method of 2-ethyl-4-methylimidazole is characterized by comprising the following steps: putting 88g of methyl propionate and 148g of 1, 2-propane diamine into a flask, carrying out reflux reaction for 3 hours at the temperature of 80 ℃, adding 3g of activated alumina and 176g of dimethylbenzene, evaporating unreacted reactants at low temperature, heating to carry out reflux dehydration reaction until anhydrous components are distilled out; carrying out reduced pressure distillation, and collecting 102-112 ℃/2.0kpa of fraction to prepare 2-ethyl-4-methylimidazoline;
112g of 2-ethyl-4-methylimidazoline was added to 2.2g of a pd/c catalyst (5%; wt%) and the mixture was slowly heated to 140 ℃ to conduct dehydrogenation for 10 hours until no bubbles were released; suction filtering, reduced pressure distillation, and collecting the fraction with the boiling point of 150-160 ℃/1.33kpa to obtain the 2-ethyl-4-methylimidazole.
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Citations (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US4298748A (en) * | 1978-12-16 | 1981-11-03 | Basf Aktiengesellschaft | Preparation of 2-imidazolines |
| CN101212898A (en) * | 2005-05-03 | 2008-07-02 | 拜尔农作物科学股份公司 | Insecticidal substituted aminoalkyl heterocyclic and heteroaryl derivatives |
| CN105367499A (en) * | 2015-12-24 | 2016-03-02 | 上海三爱思试剂有限公司 | Preparation method of 2-ethyl-4-methylimidazole |
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- 2019-11-07 CN CN201911080429.5A patent/CN110845415B/en active Active
Patent Citations (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US4298748A (en) * | 1978-12-16 | 1981-11-03 | Basf Aktiengesellschaft | Preparation of 2-imidazolines |
| CN101212898A (en) * | 2005-05-03 | 2008-07-02 | 拜尔农作物科学股份公司 | Insecticidal substituted aminoalkyl heterocyclic and heteroaryl derivatives |
| CN105367499A (en) * | 2015-12-24 | 2016-03-02 | 上海三爱思试剂有限公司 | Preparation method of 2-ethyl-4-methylimidazole |
Non-Patent Citations (3)
| Title |
|---|
| 2-咪唑啉类化合物的合成及应用研究新进展;周葆悦 等;《有机化学》;20131231;第33卷;第423-435页 * |
| Catalytic Synthesis of C-Alkylimidazoles Over Platinum-Alumina Catalysis;K. M. Gitis, et al;《Organic Chemistry》;19921231;第728-734页 * |
| 响应面法优化咪唑啉硫酸酯盐的合成及性能研究;郭睿 等;《日用化学工业》;20160630;第46卷(第6期);第314-319,343页 * |
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