A process for the preparation of phenyldiethanolamine

Abstract

The application discloses a preparation method of phenyldiethanolamine and belongs to the technical field of organic synthesis intermediates. The preparation method of the phenyldiethanolamine comprises the following steps: stirring and uniformly mixing aniline and ethylene oxide, adding a bifunctional ionic liquid catalyst to react, and obtaining after treatment, wherein the bifunctional ionic liquid catalyst is obtained by reacting 1-pentyl imidazole and DL-bromosuccinic acid. The bifunctional ionic liquid catalyst prepared in the application contains imidazole cations, carboxyl groups and pentyl alkyl chains in the molecules, and the synergistic effect of the structures promotes the ring-opening reaction of aniline to ethylene oxide, improves the reaction rate and the selectivity of the target product, and the prepared phenyldiethanolamine has a high yield.

Description

Technical Field

[0001] This invention relates to the field of organic synthesis intermediates, and specifically to a method for preparing phenyldiethanolamine. Background Technology

[0002] Phenylacetylene diethanolamine is an important organic synthesis intermediate, widely used in the synthesis of pharmaceuticals, dyes, surfactants and polymer auxiliaries. Currently, the main industrial method is the direct addition of aniline to ethylene oxide, but the traditional process has the following drawbacks: (1) High pressure is required to control the selectivity of mono / diaddition, which is complicated and poses a risk of ethylene oxide explosion; (2) Without a catalyst or when using homogeneous acid / base catalysts, there are many byproducts (such as monoadditions and triadditions), the yield is low and separation is difficult; (3) The catalyst is difficult to recycle, which greatly increases the cost.

[0003] Chinese invention patent CN115073311A discloses an efficient method for preparing N,N′-di(2-hydroxyethyl)aniline. The method involves adding catalyst Co(II), zinc powder, an organic solvent, nitrobenzene or heteroarylbenzene, and 2-haloethanol to a reaction vessel. The reaction is carried out at 60-90°C. After the reaction is complete as detected by TLC, the mixture is extracted with a mixture of ethyl acetate and distilled water. The organic phases are combined, dried with anhydrous sodium sulfate, and separated by column chromatography to obtain N,N′-di(2-hydroxyethyl)aniline. All reagents used in this invention are commercially available, and the reaction has no intermediate steps, making it simple and convenient to operate. This invention uses nitrobenzene or heteroarylbenzene as raw materials to synthesize the target product, broadening the synthesis methods for N,N′-di(2-hydroxyethyl)aniline. However, its preparation process requires a metal catalyst (Co(II)) + zinc powder and a haloethanol, resulting in metal residues and halogen waste, which is not conducive to green production.

[0004] Therefore, developing a mild, catalyst-recoverable, solvent-free, and highly selective green method for preparing phenyldiethanolamine has significant industrial value and innovative implications. Summary of the Invention

[0005] In view of the shortcomings of the existing technology, the purpose of this invention is to provide a method for preparing phenyldiethanolamine.

[0006] A method for preparing phenyldiethanolamine involves stirring and mixing aniline with ethylene oxide, adding a bifunctional ionic liquid catalyst, and then performing post-treatment. The chemical structural formula of the bifunctional ionic liquid catalyst is as follows: .

[0007] The bifunctional ionic liquid catalyst was obtained by reacting 1-pentylimidazol with DL-bromosuccinic acid.

[0008] The molar ratio of 1-pentylimidazolium to DL-bromosuccinic acid is 1:(1.03-1.05).

[0009] The solvent used in the reaction of 1-pentylimidazol with DL-bromosuccinic acid is DMF.

[0010] The reaction temperature of 1-pentylimidazol with DL-bromosuccinic acid is 60-70℃.

[0011] The reaction time of 1-pentylimidazol with DL-bromosuccinic acid is 18-20 h.

[0012] The molar ratio of aniline to ethylene oxide is 1:(2.05-2.1).

[0013] The amount of the bifunctional ionic liquid catalyst used is 1%-3% of the molar amount of aniline.

[0014] The reaction temperature is 50-55℃.

[0015] The reaction time is 6-7 hours.

[0016] Due to the adoption of the above technical solutions, the beneficial effects of the present invention include: This invention achieves effective activation and selective control of the ring-opening reaction of ethylene oxide in the preparation of phenyldiethanolamine by using a bifunctional ionic liquid catalyst containing imidazole cations and carboxyl functional groups. Highly selective dihydroxyethylation of aniline can be achieved under solvent-free and mild conditions (50-55℃). Compared with traditional processes, this invention eliminates the need for strong acid or strong base catalysts, significantly reducing side reactions and improving the selectivity of the target product. Simultaneously, by controlling the dropping rate of ethylene oxide, excessive alkylation and polymerization reactions are effectively suppressed, making the reaction process safer and more controllable. The yield of the obtained product is as high as 99.23%, and the process reproducibility is excellent. Furthermore, the bifunctional ionic liquid catalyst requires a small amount and can be efficiently recovered and recycled through simple filtration, exhibiting good stability and significantly reducing production costs. The entire process is simple, mild, and environmentally friendly, possessing excellent prospects for industrial scale-up and application value. Detailed Implementation

[0017] Example 1: Preparation of bifunctional ionic liquid catalysts Under nitrogen protection, 150 ml of DMF (N,N-dimethylformamide), 0.1 mol of 1-pentylimidazole, and 0.103 mol of DL-bromosuccinic acid were stirred and mixed thoroughly. The mixture was heated to 60 °C and reacted for 20 h. After cooling to room temperature, the mixture was rotary evaporated at 50 °C to constant weight. 120 ml of ethyl acetate was slowly added and stirred to precipitate the precipitate. The precipitate was filtered, and the filter cake was washed successively with 50 ml of ethyl acetate and 50 ml of anhydrous diethyl ether. The precipitate was dried under vacuum at 40 °C for 12 h to obtain the bifunctional ionic liquid catalyst. The reaction equation is shown below:

[0018] Its 1H NMR data are as follows: 1 H NMR (400 MHz, Chloroform- d ) δ 11.80 (s, 1H),10.93 (s, 1H), 9.08 (s, 1H), 8.11 (d, J = 3.5 Hz, 1H), 7.71 (d, J = 3.7 Hz,1H), 5.63-5.57 (m, 1H), 4.13 (d, J = 2.2 Hz, 2H), 3.36 – 3.24 (m, 2H), 1.77(d, J = 4.5 Hz, 2H), 1.34 (d, J = 1.3 Hz, 4H), 0.90 (t, J = 6.3 Hz, 3H); HRMS(m / z):255.1346[M-Br] + .

[0019] Example 2 Preparation of bifunctional ionic liquid catalysts Under nitrogen protection, 150 ml of DMF, 0.1 mol of 1-pentylimidazole, and 0.104 mol of DL-bromosuccinic acid were stirred and mixed. The mixture was heated to 65 °C and reacted for 19 h. After cooling to room temperature, the mixture was rotary evaporated at 50 °C to constant weight. 120 ml of ethyl acetate was slowly added and stirred to precipitate the precipitate. The precipitate was filtered, and the filter cake was washed successively with 50 ml of ethyl acetate and 50 ml of anhydrous diethyl ether. The precipitate was dried under vacuum at 40 °C for 12 h to obtain the bifunctional ionic liquid catalyst.

[0020] Example 3 Preparation of bifunctional ionic liquid catalysts Under nitrogen protection, 150 ml of DMF, 0.1 mol of 1-pentylimidazole, and 0.105 mol of DL-bromosuccinic acid were stirred and mixed. The mixture was heated to 70 °C and reacted for 18 h. After cooling to room temperature, the mixture was rotary evaporated at 50 °C to constant weight. 120 ml of ethyl acetate was slowly added and stirred to precipitate the precipitate. The precipitate was filtered, and the filter cake was washed successively with 50 ml of ethyl acetate and 50 ml of anhydrous diethyl ether. The precipitate was dried under vacuum at 40 °C for 12 h to obtain the bifunctional ionic liquid catalyst.

[0021] Example 4 Preparation of phenyldiethanolamine Under nitrogen protection, 0.1 mol aniline and 1 mmol bifunctional ionic liquid catalyst (prepared in Example 1) were added to a reaction flask, stirred and mixed, heated to 50°C, and 0.205 mol ethylene oxide was slowly added dropwise over 1 hour. The reaction continued for 7 hours, cooled to room temperature, and 20 ml ethyl acetate was added and stirred for 10 minutes. The catalyst was recovered by filtration (the filter cake was washed twice with 20 ml ethyl acetate, dried under vacuum at 80°C for 12 hours, and then recycled). The filtrates were combined and rotary evaporated at 50°C to constant weight. The crude product was dissolved in 80 ml ethyl acetate, washed with deionized water until neutral, dried with 20 g anhydrous magnesium sulfate, filtered, and rotary evaporated at 50°C to constant weight to obtain 17.91 g phenyldiethanolamine, with a yield of 98.84%.

[0022] Example 5 Preparation of phenyldiethanolamine Under nitrogen protection, 0.1 mol aniline and 2 mmol bifunctional ionic liquid catalyst (prepared in Example 2) were added to a reaction flask, stirred and mixed, heated to 50°C, and 0.208 mol ethylene oxide was slowly added dropwise over 1 hour. The reaction continued for 7 hours, cooled to room temperature, and 20 ml ethyl acetate was added and stirred for 10 minutes. The catalyst was recovered by filtration (the filter cake was washed twice with 20 ml ethyl acetate, dried under vacuum at 80°C for 12 hours, and then recycled). The filtrates were combined and rotary evaporated at 50°C to constant weight. The crude product was dissolved in 80 ml ethyl acetate, washed with deionized water until neutral, dried with 20 g anhydrous magnesium sulfate, filtered, and rotary evaporated at 50°C to constant weight to obtain 17.98 g phenyldiethanolamine, with a yield of 99.23%.

[0023] Example 6 Preparation of phenyldiethanolamine Under nitrogen protection, 0.1 mol aniline and 3 mmol bifunctional ionic liquid catalyst (prepared in Example 3) were added to a reaction flask, stirred and mixed, heated to 55°C, and 0.21 mol ethylene oxide was slowly added dropwise over 1 hour. The reaction continued for 6 hours, cooled to room temperature, and 20 ml ethyl acetate was added and stirred for 10 minutes. The catalyst was recovered by filtration (the filter cake was washed twice with 20 ml ethyl acetate, dried under vacuum at 80°C for 12 hours, and then recycled). The filtrates were combined and rotary evaporated at 50°C to constant weight. The crude product was dissolved in 80 ml ethyl acetate, washed with deionized water until neutral, dried with 20 g anhydrous magnesium sulfate, filtered, and rotary evaporated at 50°C to constant weight to obtain 17.94 g phenyldiethanolamine, with a yield of 99.01%.

[0024] Example 7 Preparation of phenyldiethanolamine Under nitrogen protection, 0.1 mol of aniline and 2 mmol of the bifunctional ionic liquid catalyst recovered from Example 5 after 5 cycles were added to a reaction flask, stirred and mixed, heated to 50°C, and 0.208 mol of ethylene oxide was slowly added dropwise over 1 hour. The reaction continued for 7 hours, cooled to room temperature, and 20 ml of ethyl acetate was added and stirred for 10 minutes. The mixture was filtered, and the filtrates were combined and rotary evaporated at 50°C to constant weight. The crude product was dissolved in 80 ml of ethyl acetate, washed with deionized water until neutral, dried over 20 g of anhydrous magnesium sulfate, filtered, and rotary evaporated at 50°C to constant weight to obtain 17.75 g of phenyldiethanolamine, with a yield of 97.96%.

[0025] Comparative Example 1 The preparation method of phenyldiethanolamine is basically the same as that in Example 5, except that the bifunctional ionic liquid catalyst is replaced with an equimolar amount of a bifunctional ionic liquid catalyst prepared by the following method: The preparation method of the bifunctional ionic liquid catalyst is basically the same as that in Example 2, except that DL-bromosuccinic acid is replaced with an equimolar amount of 4-bromobutyric acid.

[0026] The yield of Comparative Example 1 was 95.51%.

[0027] Comparative Example 2 The preparation method of phenyldiethanolamine is basically the same as that in Example 5, except that the bifunctional ionic liquid catalyst is replaced with an equimolar amount of a bifunctional ionic liquid catalyst prepared by the following method: The preparation method of the bifunctional ionic liquid catalyst is basically the same as that in Example 2, except that 1-pentylimidazole is replaced with an equimolar amount of 1-methylimidazole.

[0028] The yield of Comparative Example 2 was 97.64%.

[0029] Comparative Example 3 The preparation method of phenyldiethanolamine is basically the same as that in Example 5, except that the bifunctional ionic liquid catalyst is replaced with an equimolar amount of DL-bromosuccinic acid.

[0030] The yield of Comparative Example 3 was 93.81%.

[0031] Comparative Example 4 The preparation method of phenyldiethanolamine is basically the same as that in Example 5, except that the bifunctional ionic liquid catalyst is replaced with an equimolar amount of 1-pentylimidazole.

[0032] The yield of Comparative Example 4 was 94.64%.

[0033] The bifunctional ionic liquid catalyst prepared in this application contains an imidazole cation, a carboxyl group, and a pentylalkyl chain, belonging to a novel acid-base bifunctional ionic liquid. In the preparation of phenyldiethanolamine, this catalyst plays a key synergistic role: the carboxyl group acts as a Br... The nsted acidic sites can activate ethylene oxide molecules through protonation, enhancing the polarization of the epoxy ring and thus lowering the activation energy of the ring-opening reaction. Simultaneously, the imidazole cation provides weakly basic sites, promoting nucleophilic attack of the nitrogen atom in aniline. Furthermore, the pentylalkyl chain endows the catalyst with good compatibility and lipophilicity in solvent-free systems, which is beneficial for improving the mass transfer efficiency of the reaction system. The synergistic effect of the various structures in the catalyst molecule promotes the ring-opening reaction of aniline with ethylene oxide, improving the reaction rate and the selectivity of the target product; the prepared phenyldiethanolamine exhibits a high yield.

[0034] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. However, any modifications, alterations, and variations made by those skilled in the art without departing from the scope of the present invention based on the disclosed technical content are equivalent embodiments of the present invention. Furthermore, any modifications, alterations, and variations made to the above embodiments based on the essential technology of the present invention are still within the protection scope of the present invention.

Claims

1. A method for preparing phenyldiethanolamine, characterized in that, The product is obtained by stirring and mixing aniline and ethylene oxide, adding a bifunctional ionic liquid catalyst, and then undergoing post-treatment. The chemical structural formula of the bifunctional ionic liquid catalyst is as follows: 。 2. The method for preparing phenyldiethanolamine according to claim 1, characterized in that, The bifunctional ionic liquid catalyst was obtained by reacting 1-pentylimidazol with DL-bromosuccinic acid.

3. The method for preparing phenyldiethanolamine according to claim 2, characterized in that, The molar ratio of 1-pentylimidazolium to DL-bromosuccinic acid is 1:(1.03-1.05).

4. The method for preparing phenyldiethanolamine according to claim 2, characterized in that, The solvent used in the reaction of 1-pentylimidazol with DL-bromosuccinic acid is DMF.

5. The method for preparing phenyldiethanolamine according to claim 2, characterized in that, The reaction temperature of 1-pentylimidazol with DL-bromosuccinic acid is 60-70℃.

6. The method for preparing phenyldiethanolamine according to claim 2, characterized in that, The reaction time of 1-pentylimidazol with DL-bromosuccinic acid is 18-20 h.

7. The method for preparing phenyldiethanolamine according to claim 1, characterized in that, The molar ratio of aniline to ethylene oxide is 1:(2.05-2.1).

8. The method for preparing phenyldiethanolamine according to claim 1, characterized in that, The amount of the bifunctional ionic liquid catalyst used is 1%-3% of the molar amount of aniline.

9. The method for preparing phenyldiethanolamine according to claim 1, characterized in that, The reaction temperature is 50-55℃.

10. The method for preparing phenyldiethanolamine according to claim 1, characterized in that, The reaction time is 6-7 hours.

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