Synthesis method of 2, 4, 6-trimethyl-1, 3-phenylenediamine

Abstract

The invention discloses a synthesis method of 2, 4, 6-trimethyl-1, 3-phenylenediamine, which comprises the following steps: (1) carrying out sulfonation reaction on mesitylene serving as an initial raw material and fuming sulfuric acid to obtain a first intermediate; (2) carrying out nitration reaction on the first intermediate obtained in the step (1) and concentrated nitric acid to obtain a second intermediate; (3) carrying out hydrolysis reaction on the second intermediate obtained in the step (2) under an acidic condition to obtain a third intermediate; and (4) carrying out catalytic hydrogenation reaction on the third intermediate obtained in the step (3) to obtain 2, 4, 6-trimethyl-1, 3-phenylenediamine. The method provided by the invention not only avoids the problem that an explosive compound trinitro-mesitylene is generated in the nitration process in the prior art, greatly improves the production safety, but also avoids the problems of serious pollution of bromination reaction and high production cost caused by incapability of applying a hydrogenation reaction catalyst in the prior art, and is suitable for industrial mass production.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of organic synthesis, and particularly relates to a synthesis method of 2,4,6-trimethyl-1,3-benzene diamine. BACKGROUND

[0002] As a kind of special engineering material, polyimide has been widely used in aviation, aerospace, microelectronics, nanometer, liquid crystal, separation membrane, laser and other fields. In the 1960s, the research, development and utilization of polyimide were listed as one of the most promising engineering plastics in the 21st century. Due to its outstanding characteristics in performance and synthesis, whether as a structural material or as a functional material, its huge application prospect has been fully recognized.

[0003] 2,4,6-trimethyl-1,3-benzene diamine is a kind of diamine monomer, the melting range is 89-91℃, the molecular formula is C9H 14 N2, the relative molecular weight is 150.22, the CAS number is 3102-70-3, and it is mainly used for the preparation of special polyimide materials.

[0004] The existing technology discloses two kinds of synthesis methods of 2,4,6-trimethyl-1,3-benzene diamine as follows: (1) Using mesitylene as a starting material, nitration is first carried out with mixed acid (sulfuric acid + nitric acid) to obtain 2,4,6-trimethyl-m-dinitrobenzene, and then catalytic hydrogenation is carried out to obtain 2,4,6-trimethyl-m-phenylenediamine

see documents CN105254510A and CN105461567A

[0005] The synthesis route is as follows: .

[0006] The deficiency of the method is that: the direct nitration of mesitylene will generate the explosive compound trinitromesitylene with high energy density, which has great safety risk and is not suitable for industrial mass production.

[0007] (2) Using mesitylene as a starting material, 2,4,6-trimethyl-1,3-benzene diamine is obtained through three steps of bromination, nitration and hydrogenation

see US5118880A

[0008] The synthesis route is as follows: .

[0009] The deficiency of the method is that: although the generation of trinitro compound can be avoided, the first step of bromination reaction is seriously polluted and is extremely unfriendly to the environment, and the reduction of nitro group and the removal of bromine in the third step will cause the deactivation of the noble metal catalyst and cannot be reused, resulting in very high production cost. SUMMARY

[0010] The present application aims to solve the above problems, and provides a synthesis method of 2,4,6-trimethyl-1,3-benzenediamine to solve the problems of great safety risk, serious environmental pollution and high production cost in the industrial production of the prior art.

[0011] The technical solution to achieve the object of the present application is: a synthesis method of 2,4,6-trimethyl-1,3-benzenediamine, having the following steps: ① Using mesitylene as a starting material, first performing a sulfonation reaction with fuming sulfuric acid to obtain a first intermediate 2,4,6-trisulfo-mesitylene; ② Performing a nitration reaction of the first intermediate obtained in step ① with concentrated nitric acid to obtain a second intermediate 2,4,6-trimethyl-5-sulfo-m-dinitrobenzene; ③ Performing a hydrolysis reaction of the second intermediate obtained in step ② under acidic conditions to obtain a third intermediate 2,4,6-trimethyl-m-dinitrobenzene; ④ Performing a catalytic hydrogenation reaction of the third intermediate obtained in step ③ to obtain 2,4,6-trimethyl-1,3-benzenediamine.

[0012] The specific synthesis route is as follows: .

[0013] In the above step ①, the concentration (i.e. sulfur trioxide content) of the fuming sulfuric acid is 20-30 wt%; the molar ratio of the mesitylene to the sulfur trioxide in the fuming sulfuric acid is 1:3-1:4.

[0014] In the above step ①, the mesitylene is added dropwise, the sulfonation reaction temperature is 50-80℃, and the first intermediate can be directly used in the next step without purification.

[0015] In the above step ②, the concentration of the concentrated nitric acid is 65-68 wt%; the molar ratio of the mesitylene to the concentrated nitric acid is 1:2-1:3.

[0016] In the above step ②, the concentrated nitric acid is added dropwise, the nitration reaction temperature is 20-30℃, and the second intermediate can be directly used in the next step without purification.

[0017] In the above step ③, the hydrolysis reaction temperature is 90-100℃, and after the hydrolysis reaction is completed, toluene recrystallization is further included, and the weight ratio of the third intermediate to the toluene is 1:3-1:5.

[0018] In the above step ④, the catalyst used in the catalytic hydrogenation reaction is platinum-carbon or palladium-carbon.

[0019] In step ④ above, the catalytic hydrogenation reaction temperature is 40–80°C and the reaction pressure is 0.2–1.0 MPa.

[0020] In step ④ above, the solvent used in the catalytic hydrogenation reaction is methanol, ethanol or isopropanol, and the weight ratio of the third intermediate to the solvent is 1:1 to 1:6.

[0021] The positive effects of this invention are: the method of this invention avoids the problem of producing explosive compounds such as trinitrotrimethylbenzene in the nitration process of existing technologies, which greatly improves production safety, and also avoids the problems of serious pollution in the bromination reaction and high production costs caused by the inability to use hydrogenation catalysts in existing technologies, making it suitable for large-scale industrial production. Attached Figure Description

[0022] Figure 1 The image shows the LC-MS spectrum of the second intermediate obtained in Example 1.

[0023] Figure 2 The image shows the LC-MS spectrum of the third intermediate obtained in Example 1.

[0024] Figure 3 The image shows the LC-MS spectrum of the final product obtained in Example 1.

[0025] Figure 4 The image shows the DSC spectrum of the final product obtained in Example 1. Detailed Implementation

[0026] (Example 1) The method for synthesizing 2,4,6-trimethyl-1,3-phenylenediamine in this embodiment is as follows: ① Add 366g of 30wt% fuming sulfuric acid (containing 1.37mol of sulfur trioxide) to a 1L three-necked flask, stir and cool to 10-15℃, and slowly add 50g of mesitylene (0.42mol) dropwise while keeping the temperature below 40℃. The addition is completed in about 2 hours. After the addition is completed, stir for 30 minutes, then raise the temperature to 60-65℃ and keep stirring for 2 hours to obtain a reaction solution containing the first intermediate.

[0027] ② Cool down to 20-25℃, and slowly add 89g of concentrated nitric acid (0.96mol) with a concentration of 68wt% at 20-30℃. The addition is completed in about 5 hours. After the addition is completed, continue to stir the reaction at 20-30℃ for 2 hours to obtain a reaction solution containing the second intermediate.

[0028] The LC-MS spectrum of the second intermediate is shown below. Figure 1 ,Depend on Figure 1 It can be seen that its molecular weight is 290.2, which is basically the same as that of 2,4,6-trimethyl-5-sulfo-m-dinitrobenzene.

[0029] (3) Into a 2 L three-necked flask was added 400 g of water, and the temperature was lowered to 0-5 °C. The reaction solution obtained in step (2) was slowly added dropwise at a temperature controlled below 50 °C, and the dropping was completed in about 2 h. The temperature was then raised to 98-100 °C for reflux reaction for 8 h. The temperature was then lowered to 10-15 °C, and the product was filtered. The filter cake was rinsed with 100 g of water, and the crude product of the third intermediate was obtained.

[0030] Into the crude product of the third intermediate was added 300 g of toluene, and the temperature was raised to 95-100 °C until the solid was completely dissolved. The solution was allowed to stand and separate into two layers. The lower aqueous layer was removed. 100 g of water was added to the organic layer, and the mixture was stirred at 95-100 °C for 15 min. The solution was allowed to stand and separate into two layers. The lower aqueous layer was removed. The organic layer was slowly cooled to 0-5 °C, and the product was filtered. The filter cake was rinsed with a small amount of toluene, and then dried in an oven at 30-35 °C under vacuum for 10 h. The yellowish third intermediate was obtained in an amount of 66.4 g, and the HPLC purity was 99.3%. The overall yield of the three steps was 75.9%.

[0031] The LC-MS spectrum of the third intermediate is shown in Figure 2 As can be seen, the molecular weight thereof is 210.1, which is basically consistent with that of 2,4,6-trimethyl-m-dinitrobenzene. Figure 2

[0032] (4) 60 g of the third intermediate obtained in step (3) was added to a 500 mL hydrogenation kettle, followed by the addition of 3 g of 5 wt% platinum-carbon catalyst and 120 g of methanol. The kettle was replaced with nitrogen for 3 times, and then replaced with hydrogen for 3 times. The reaction was carried out at 0.5±0.1 MPa and 55±2 °C for 3 h until no hydrogen was absorbed, and then the pressure was maintained for another 30 min. The hydrogen was released, and the kettle was replaced with nitrogen for 3 times. The reaction solution was filtered into a 500 mL three-necked flask (the catalyst was recovered for reuse). Then, 120 g of water was added, and the temperature was lowered to 10-15 °C while stirring for 30 min. The product was filtered, and the filter cake was rinsed with a small amount of water. The product was dried in an oven at 70-80 °C under vacuum for 6 h. The final product was obtained in an amount of 37.9 g, and the HPLC purity was 99.6%. The yield was 88.3%, and the melting point was 92.4-94.1 °C (see Figure 4 ).

[0033] The LC-MS spectrum of the final product is shown in Figure 3 As can be seen, the molecular weight thereof is 150.2, which is basically consistent with that of 2,4,6-trimethyl-1,3-phenylenediamine. Figure 3 (Example 2)

[0034] The synthesis method of 2,4,6-trimethyl-1,3-phenylenediamine in this example is as follows: ​​①Into a 1L flask, 560g of 20wt% oleum (containing 1.40mol of sulfur trioxide) was added, and the temperature was lowered to 10-15°C while stirring. Then, 50g of mesitylene (0.42mol) was slowly added dropwise at a temperature controlled below 40°C, and the dropping was completed in about 2h. After the dropping, the mixture was stirred for 30min, and then the temperature was raised to 65-70°C for 2h to obtain a reaction solution containing the first intermediate.

[0035] ②The temperature was lowered to 20-25°C, and 95g of 65wt% concentrated nitric acid (0.98mol) was slowly added dropwise at a temperature controlled at 20-30°C, and the dropping was completed in about 5h. After the dropping, the mixture was stirred for 2h at a temperature controlled at 20-30°C to obtain a reaction solution containing the second intermediate.

[0036] ③Into a 2L flask, 600g of water was added, and the temperature was lowered to 0-5°C. Then, the reaction solution obtained in step ② was slowly added dropwise at a temperature controlled below 50°C, and the dropping was completed in about 2h. After the dropping, the temperature was raised to 98-100°C for 7h to obtain a crude product of the third intermediate.

[0037] Into the crude product of the third intermediate, 300g of toluene was added, and the temperature was raised to 95-100°C until the solid was completely dissolved. After the separation of the lower aqueous phase, 100g of water was added to the organic phase, and the mixture was stirred at 95-100°C for 15min. After the separation of the lower aqueous phase, the organic phase was slowly cooled to 0-5°C, and the mixture was filtered. The filter cake was rinsed with a small amount of toluene and then dried in an oven at 30-35°C under vacuum for 10h to obtain 63.5g of the third intermediate in a light yellow color, with a purity of 99.0% by HPLC. The total yield of the three steps was 72.6%.

[0038] ④Into a 500mL hydrogenation reactor, 60g of the third intermediate obtained in step ③ was added, followed by the addition of 3g of 3wt% palladium-carbon catalyst and 90g of isopropyl alcohol. The reactor was replaced with nitrogen for 3 times and then replaced with hydrogen for 3 times. Then, the mixture was reacted at 0.5±0.1MPa and 55±2°C for 2h until no hydrogen was absorbed. The mixture was further reacted at 0.5±0.1MPa for 30min. Then, the temperature of the mixture was adjusted to 75-80°C, and the hydrogen was released. The mixture was replaced with nitrogen for 3 times, and then filtered into a 250mL flask (the catalyst was recovered for reuse). The mixture was cooled to 0-5°C and stirred for 30min. The mixture was filtered, and the filter cake was rinsed with a small amount of cold isopropyl alcohol and then dried in an oven at 50-60°C under vacuum for 6h to obtain 34.7g of the final product 2,4,6-trimethyl-1,3-phenylenediamine, with a purity of 99.8% by HLC and a yield of 80.9%.

Claims

1. A process for the synthesis of 2,4,6-trimethyl-1,3-benzenediamine, characterized in that The method comprises the following steps: ① taking mesitylene as a starting material, and performing a sulfonation reaction with fuming sulfuric acid to obtain a first intermediate 2,4,6-trisulfo-mesitylene; ② performing a nitration reaction of the first intermediate obtained in step ① with concentrated nitric acid to obtain a second intermediate 2,4,6-trimethyl-5-sulfo-m-dinitrobenzene; ③ performing a hydrolysis reaction of the second intermediate obtained in step ② under an acidic condition to obtain a third intermediate 2,4,6-trimethyl-m-dinitrobenzene; ④ performing a catalytic hydrogenation reaction of the third intermediate obtained in step ③ to obtain 2,4,6-trimethyl-1,3-phenylenediamine.

2. The process for the synthesis of 2,4,6-trimethyl-1,3-benzene diamine according to claim 1, characterized in that: In the step ①, the concentration of the fuming sulfuric acid is 20-30 wt%; and the molar ratio of the mesitylene to sulfur trioxide in the fuming sulfuric acid is 1:3-1:

4.

3. The process for the synthesis of 2,4,6-trimethyl-l,3-benzene diamine according to claim 1, characterized in that: In the step ①, the mesitylene is added dropwise, and the sulfonation reaction temperature is 50-80 ℃.

4. The process for the synthesis of 2,4,6-trimethyl-l,3-benzene diamine according to claim 1, characterized in that: In the step ②, the concentration of the concentrated nitric acid is 65-68 wt%; and the molar ratio of the mesitylene to the concentrated nitric acid is 1:2-1:

3.

5. The process for the synthesis of 2,4,6-trimethyl-l,3-benzene diamine as claimed in claim 1, wherein: In the step ②, the concentrated nitric acid is added dropwise, and the nitration reaction temperature is 20-30 ℃.

6. The process for the synthesis of 2,4,6-trimethyl-l,3-benzene diamine according to claim 1, characterized in that: In the step ③, the hydrolysis reaction temperature is 90-100 ℃, and after the hydrolysis reaction is completed, a toluene recrystallization is further included, and the weight ratio of the third intermediate to the toluene is 1:3-1:

5.

7. The process for the synthesis of 2,4,6-trimethyl-l,3-benzene diamine as claimed in claim 1, wherein: In the step ④, the catalyst used in the catalytic hydrogenation reaction is platinum-carbon or palladium-carbon.

8. The process for the synthesis of 2,4,6-trimethyl-l,3-benzene diamine as claimed in claim 1, wherein: In the step ④, the catalytic hydrogenation reaction temperature is 40-80 ℃, and the reaction pressure is 0.2-1.0 MPa.

9. The process for the synthesis of 2,4,6-trimethyl-l,3-benzene diamine as claimed in claim 1, wherein: In the step ④, the solvent used in the catalytic hydrogenation reaction is methanol, ethanol or isopropyl alcohol, and the weight ratio of the third intermediate to the solvent is 1:1-1:6.

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