Synthesis method of DBU

Abstract

The invention discloses a synthetic method of DBU, and belongs to the technical field of chemical synthesis, under an alkaline condition, caprolactam and 2-haloethylamine react to directly generate an aminopropyl caprolactam intermediate in one step, and the intermediate generates DBU under the action of an acid catalyst; according to the method, the 2-haloethylamine is used for replacing a traditional acrylamide raw material, the aminopropyl caprolactam intermediate is directly generated in one step, by-products caused by self-polymerization of the raw material are completely eradicated from the source, a Raney nickel catalyst system is avoided, high-pressure operation is not used, the safety risk of production is reduced, the technical problems existing in DBU production at present can be solved, and the method is suitable for industrial production. The method is suitable for industrial application.

Description

Technical Field

[0001] The invention belongs to the technical field of chemical synthesis, and specifically relates to a method for synthesizing DBU. Background Art

[0002] 1,8-diazabicyclo[5.4.0]undec-7-ene (hereinafter referred to as DBU, chemical formula C9H16N2) is an amidine compound with a unique chemical structure. It has important applications in organic synthesis due to its large steric hindrance and high basicity. The molecular structure of DBU contains a two-ring system containing two nitrogen atoms, which gives it extremely strong non-nucleophilic base properties, enabling it to catalyze a variety of chemical reactions without side reactions with the reaction substrate. This property makes DBU an important representative of non-nucleophilic base catalysts.

[0003] In the field of industrial production and synthesis, DBU is widely used in a variety of important chemical processes, such as curing agent for epoxy resin and as a protective agent. In addition, in the production process of polyurethane, DBU is also widely used as a catalyst, especially in the reaction of alicyclic and aliphatic isocyanates. The efficient catalytic effect of DBU improves production efficiency and product quality. With the continuous expansion of the application scope of DBU in the fields of medicine, materials, chemicals, etc., especially in the production of pharmaceutical synthesis, electronic materials and new polymer materials, the demand is particularly significant, and its market potential in the future is huge.

[0004] At present, industrial synthesis of DBU mainly uses ε-caprolactam and acrylonitrile as raw materials to synthesize cyanoethyl caprolactam intermediate, then reduce the cyano group to aminopropyl caprolactam, and finally obtain DBU through acid dehydration. The reaction equation is as follows:

[0005] According to prior art reports, the main problem of this process is: when synthesizing the cyanoethyl caprolactam intermediate in the first step of the reaction, acrylonitrile is prone to polymerization, resulting in more by-products. The reaction temperature is usually reduced to reduce the generation of polymerization products, which in turn causes acrylonitrile to remain too much in the crude product, and the presence of acrylonitrile polymer or unreacted acrylonitrile will cause the final product color to deepen, increasing the difficulty of post-processing. In the second step of cyano reduction, generally in the presence of ammonia, Raney Ni is used as a catalyst to achieve cyano reduction, but nickel Raney is easy to ignite, anhydrous ammonia tastes bad and is also toxic, involving hazardous material operations, and the industrial process is complicated. Patent JP2003286257 proposes the use of cobalt Raney catalyst instead of nickel Raney catalyst, and cyano reduction is carried out in the absence of ammonia. Although the danger in the production process is reduced, high-pressure equipment still needs to be used, the cost budget is too high, and large-scale production is limited. Summary of the invention

[0006] In order to solve the problems of polymerization of raw material acrylonitrile and excessive raw material residue in the first step reaction of the above-mentioned DBU synthesis prior art, and the use of Raney Ni in the second step cyanide reduction has safety production risks, the purpose of the present invention is to provide a method for synthesizing DBU.

[0007] In order to achieve the above object, the present invention is implemented through the following technical solutions: A method for synthesizing DBU comprises the following steps: 1) Add the solvent and caprolactam into a reaction vessel, stir and mix evenly, then drop alkali and 2-haloethylamine therein in sequence, control the system temperature at 5-15°C, continue stirring and reacting for 30-120 minutes after the dropwise addition is completed, cool to 0-30°C after the reaction is completed, stand for 30-120 minutes, filter the obtained reaction solution, and distill the obtained filtrate under reduced pressure to remove the unreacted alkali to obtain an aminopropyl caprolactam solution; 2) adding an organic acid catalyst to the aminopropyl caprolactam solution obtained in step 1), heating to reflux for reaction and removing water, distilling the obtained anhydrous reaction solution under reduced pressure to remove the solvent, collecting the fraction at 145-150° C., and obtaining DBU.

[0008] The solvent in step 1) is toluene or xylene.

[0009] The base in step 1) is triethylamine or trimethylamine.

[0010] The 2-haloethylamine in step 1) is 2-bromoethylamine or 2-chloroethylamine.

[0011] In step 1), the molar ratio of caprolactam, 2-haloethylamine and base is 1:0.9~1.2:1~2.

[0012] The molar volume ratio of caprolactam to solvent in step 1) is 1 mol: 300-1000 mL.

[0013] The method of adding the base and 2-haloethylamine in step 1) is to first add the base with a mass fraction of 10-50%, and then add the 2-haloethylamine.

[0014] The organic acid catalyst in step 2) is benzenesulfonic acid, p-toluenesulfonic acid or m-toluenesulfonic acid.

[0015] The molar ratio of the amount of the organic acid catalyst added in step 2) to the amount of caprolactam in step 1) is 0.01-0.1:1.

[0016] Preferably, in step 1), the solvent is toluene; the base is triethylamine; the 2-haloethylamine is 2-bromoethylamine; the molar ratio of caprolactam, 2-haloethylamine and base is 1:1:1.5; and the molar volume ratio of caprolactam and solvent is 1 mol:500~600 mL.

[0017] Preferably, the method of adding the base and 2-haloethylamine in step 1) is to first add a base with a mass fraction of 20%, and then add 2-haloethylamine; in step 1), the system temperature is controlled at 10°C, and after the addition is completed, the stirring reaction is continued for 60 minutes. After the reaction is completed, the temperature is lowered to 10°C and allowed to stand for 60 minutes.

[0018] Preferably, the organic acid catalyst in step 2) is p-toluenesulfonic acid; the molar ratio of the amount of the organic acid catalyst added to the amount of caprolactam in step 1) is 0.05-0.06:1.

[0019] The synthetic route of DBU of the present invention is (when the raw material is 2-bromoethylamine): .

[0020] Compared with the prior art, the present invention has the following advantages: The synthesis method of DBU of the present invention directly generates an aminopropyl caprolactam intermediate by reacting caprolactam and 2-haloethylamine under alkaline conditions in one step, and the intermediate generates DBU under the action of an acidic catalyst. The present invention replaces the traditional acrylamide raw material with 2-haloethylamine, directly generates the aminopropyl caprolactam intermediate in one step, eliminates byproducts caused by raw material self-polymerization from the root, avoids the use of Raney nickel catalyst system, does not use high-pressure operation, reduces the safety risk of production, can solve the technical problems existing in the current DBU production, and is suitable for industrial application.

[0021] The synthesis method of DBU of the present invention adopts 2-haloethylamine as a raw material to couple with caprolactam in the first step reaction, the reaction conditions of the whole process are mild, the post-treatment is simpler, the problem of dark color of the product due to polymerization in the acrylonitrile route is avoided, the post-treatment steps are greatly reduced, and the danger caused by the use of Raney catalyst is avoided; the two-step reaction adopts the same solvent, the first step reaction liquid is directly used for the second step reaction after simple distillation, the energy consumption and solvent loss are reduced, the reaction steps are reduced, and it is conducive to industrial production; the product is white in color and has good stability, which exceeds the industry standard, the purity of the prepared product is above 99.5%, and it is in line with the modern green industrialization concept as a whole. DETAILED DESCRIPTION

[0022] In order to better understand the technical solution of the present invention, the above content of the present invention is further described in detail below through specific implementation methods in the form of embodiments, but this should not be understood as the scope of the above subject matter of the present invention being limited to the following examples. All technologies realized based on the above content of the present invention belong to the scope of the present invention.

[0023] Example 1 500 mL of toluene and 113 g of caprolactam were added to a reaction container, stirred and mixed evenly, and then 151.8 g of triethylamine was added dropwise thereto. After 20% of the total mass of triethylamine was added dropwise, 124 g of 2-bromoethylamine was started to be added dropwise, and the system temperature was controlled at 10°C. After the addition was completed, the reaction was continued to stir for 60 minutes. After the reaction was completed, the temperature was lowered to 10°C and allowed to stand for 60 minutes. The obtained reaction solution was filtered, and the obtained filtrate was distilled under reduced pressure to remove unreacted alkali to obtain an aminopropyl caprolactam solution; 8.6 g of p-toluenesulfonic acid was added to the obtained aminopropyl caprolactam solution, heated to reflux for reaction and water was separated, and the obtained anhydrous reaction solution was distilled under reduced pressure to remove the solvent, and the 145-150°C fraction was collected to obtain 138.6 g of white DBU with a purity of 99.7%.

[0024] Example 2 600 mL of toluene and 113 g of caprolactam were added to a reaction container, stirred and mixed evenly, and then 88.6 g of trimethylamine was added dropwise thereto. After 30% of the total mass of trimethylamine was added dropwise, 79.53 g of 2-chloroethylamine was started to be added dropwise. The system temperature was controlled at 10°C. After the addition was completed, the reaction was continued with stirring for 60 min. After the reaction was completed, the temperature was lowered to 10°C and allowed to stand for 60 min. The obtained reaction solution was filtered, and the obtained filtrate was distilled under reduced pressure to remove unreacted alkali to obtain an aminopropyl caprolactam solution; 7.9 g of benzenesulfonic acid was added to the obtained aminopropyl caprolactam solution, heated to reflux for reaction and separated from water, and the obtained anhydrous reaction solution was distilled under reduced pressure to remove the solvent, and the 145-150°C fraction was collected to obtain 138.3 g of white DBU with a purity of 99.6%.

[0025] Example 3 550 mL of toluene and 113 g of caprolactam were added to a reaction container, stirred and mixed evenly, and then 151.78 g of triethylamine was added dropwise thereto. After 20% of the total mass of triethylamine was added dropwise, 124 g of 2-bromoethylamine was started to be added dropwise. The system temperature was controlled at 8°C. After the addition was completed, the reaction was continued to stir for 90 min. After the reaction was completed, the temperature was lowered to 20°C and allowed to stand for 90 min. The obtained reaction solution was filtered, and the obtained filtrate was distilled under reduced pressure to remove unreacted alkali to obtain an aminopropyl caprolactam solution; 10.3 g of m-toluenesulfonic acid was added to the obtained aminopropyl caprolactam solution, heated to reflux for reaction and separated from water, and the obtained anhydrous reaction solution was distilled under reduced pressure to remove the solvent, and the 145-150°C fraction was collected to obtain 138.4 g of white DBU with a purity of 99.6%.

[0026] Example 4 800 mL of xylene and 113 g of caprolactam were added to a reaction container, stirred and mixed evenly, and then 180 g of triethylamine was added dropwise thereto. After 40% of the total mass of triethylamine was added dropwise, 85 g of 2-chloroethylamine was started to be added dropwise. The system temperature was controlled at 8°C. After the addition was completed, the reaction was continued to stir for 100 min. After the reaction was completed, the temperature was lowered to 15°C and allowed to stand for 60 min. The obtained reaction solution was filtered, and the obtained filtrate was distilled under reduced pressure to remove unreacted alkali to obtain an aminopropyl caprolactam solution; 15 g of p-toluenesulfonic acid was added to the obtained aminopropyl caprolactam solution, heated to reflux for reaction and separated from water, and the obtained anhydrous reaction solution was distilled under reduced pressure to remove the solvent, and the 145-150°C fraction was collected to obtain 138.1 g of white DBU with a purity of 99.6%.

[0027] Example 5 300 mL of xylene and 113 g of caprolactam were added to a reaction container, stirred and mixed evenly, and then 59.1 g of trimethylamine was added dropwise thereto. After 10% of the total mass of trimethylamine was added dropwise, 71.5 g of 2-chloroethylamine was started to be added dropwise. The system temperature was controlled at 5°C. After the addition was completed, the reaction was continued to stir for 30 min. After the reaction was completed, the temperature was lowered to 0°C and allowed to stand for 30 min. The obtained reaction solution was filtered, and the obtained filtrate was distilled under reduced pressure to remove unreacted alkali to obtain an aminopropyl caprolactam solution; 1.58 g of benzenesulfonic acid was added to the obtained aminopropyl caprolactam solution, heated to reflux for reaction and separated from water, and the obtained anhydrous reaction solution was distilled under reduced pressure to remove the solvent, and the 145-150°C fraction was collected to obtain 137.8 g of white DBU with a purity of 99.5%.

[0028] Example 6 1000mL of xylene and 113g of caprolactam were added to a reaction container, stirred and mixed evenly, and then 118g of trimethylamine was added dropwise thereto. After 50% of the total mass of trimethylamine was added dropwise, 148.8g of 2-bromoethylamine was started to be added dropwise, and the system temperature was controlled at 15°C. After the addition was completed, the reaction was continued to stir for 120min. After the reaction was completed, the temperature was lowered to 30°C and allowed to stand for 120min. The obtained reaction solution was filtered, and the obtained filtrate was distilled under reduced pressure to remove unreacted alkali to obtain an aminopropyl caprolactam solution; 17.2g of p-toluenesulfonic acid was added to the obtained aminopropyl caprolactam solution, heated to reflux for reaction and separated from water, and the obtained anhydrous reaction solution was distilled under reduced pressure to remove the solvent, and the 145-150°C fraction was collected to obtain 137.6g of white DBU with a purity of 99.5%.

[0029] Although the above describes the specific implementation methods of the present invention, it does not limit the scope of protection of the present invention. Based on the technical solution of the present invention, various modifications or variations that can be made by those skilled in the art without creative work are still within the scope of protection of the present invention.

Claims

1. A method for synthesizing DBU, characterized in that: The following steps are involved: 1) Add the solvent and caprolactam into a reaction vessel, stir and mix evenly, then drop alkali and 2-haloethylamine therein in sequence, control the system temperature at 5-15°C, continue stirring and reacting for 30-120 minutes after the dropwise addition is completed, cool to 0-30°C after the reaction is completed, stand for 30-120 minutes, filter the obtained reaction solution, and distill the obtained filtrate under reduced pressure to remove the unreacted alkali to obtain an aminopropyl caprolactam solution; 2) adding an organic acid catalyst to the aminopropyl caprolactam solution obtained in step 1), heating to reflux for reaction and removing water, distilling the obtained anhydrous reaction solution under reduced pressure to remove the solvent, collecting the fraction at 145-150° C., and obtaining DBU.

2. The method for synthesizing DBU according to claim 1, wherein: The solvent in step 1) is toluene or xylene; the base in step 1) is triethylamine or trimethylamine; the 2-haloethylamine in step 1) is 2-bromoethylamine or 2-chloroethylamine.

3. The synthetic method of DBU as claimed in claim 1, characterized in that: In step 1), the molar ratio of caprolactam, 2-haloethylamine and base is 1:0.9~1.2:1~2.

4. The method for synthesizing DBU according to claim 1, wherein: The molar volume ratio of caprolactam to solvent in step 1) is 1 mol: 300-1000 mL.

5. The method for synthesizing DBU according to claim 1, wherein: The method of adding the base and 2-haloethylamine in step 1) is to first add the base with a mass fraction of 10-50%, and then add the 2-haloethylamine.

6. The method for synthesizing DBU according to claim 1, wherein: The organic acid catalyst in step 2) is benzenesulfonic acid, p-toluenesulfonic acid or m-toluenesulfonic acid.

7. The method for synthesizing DBU according to claim 1, wherein: The molar ratio of the amount of the organic acid catalyst added in step 2) to the amount of caprolactam in step 1) is 0.01-0.1:

1.

8. The method for synthesizing DBU according to claim 1, wherein: In step 1), the solvent is toluene; the base is triethylamine; the 2-haloethylamine is 2-bromoethylamine; the molar ratio of caprolactam, 2-haloethylamine and base is 1:1:1.5; and the molar volume ratio of caprolactam and solvent is 1 mol:500-600 mL.

9. The method for synthesizing DBU according to claim 1, wherein: The method of adding the base and 2-haloethylamine in step 1) is to first add a base with a mass fraction of 20%, and then add 2-haloethylamine; the temperature of the system in step 1) is controlled at 10°C. After the addition is completed, the reaction is continued to be stirred for 60 minutes. After the reaction is completed, the temperature is lowered to 10°C and allowed to stand for 60 minutes.

10. The method for synthesizing DBU according to claim 1, wherein: The organic acid catalyst in step 2) is p-toluenesulfonic acid; the molar ratio of the amount of the organic acid catalyst added to the caprolactam in step 1) is 0.05-0.06:1.

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