A method for preparing a polyimide diamine monomer

Abstract

This invention relates to a method for preparing a polyimide diamine monomer, belonging to the field of chemical synthesis technology. The preparation method is as follows: (1) Under inert gas protection, reactant I reacts with a reducing agent in a solvent to obtain intermediate I; (2) Under the action of a catalyst and a dehydrating agent, intermediate I reacts with reactant II to obtain intermediate II; (3) Under inert gas protection, intermediate II, Raney nickel, glacial acetic acid, pyridine, and sodium hypophosphite aqueous solution are added to a solvent for reaction. After the reaction is completed, the polyimide diamine monomer is obtained after post-treatment. This invention uses a system of Raney nickel, glacial acetic acid, pyridine, and sodium hypophosphite to reduce nitro groups while retaining double bonds and ester groups to prepare this type of polyimide diamine monomer containing double bonds and ester groups, thereby obtaining a high-purity, high-yield target product. The reaction steps are short, the yield is high, the cost is low, the preparation method is simple, which is conducive to large-scale production and has broad application prospects.

Description

Technical Field

[0001] This invention relates to a method for preparing a polyimide diamine monomer, belonging to the field of chemical synthesis technology. Background Technology

[0002] In the existing technology, polyimide (PI) has excellent comprehensive performance in the field of semiconductor materials. Polyimide has good heat resistance, chemical corrosion resistance, low dielectric properties and good mechanical properties. Transparent polyimide materials have a very broad application prospect in the field of optoelectronic devices with optical performance requirements, such as foldable mobile phone screens, touch screens, flexible printed circuits and other fields.

[0003] Traditional engineering polyimide materials suffer from poor processing performance and dark color due to their rigid structure, which significantly limits their widespread application. In recent years, with the development of semiconductor materials research, researchers have discovered that introducing large-volume side-chain groups, fluorine atoms, aliphatic chains, aliphatic ring structures, or asymmetric non-coplanar structures into polyimides can yield polyimide materials with lighter colors that are suitable for dissolution and coating into films.

[0004] When synthesizing polyimide materials used in the semiconductor field, common diamine or dianhydride monomers often cannot simultaneously achieve optimal optical, heat resistance, mechanical, and dielectric properties. For example, in the field of flexible substrates, an ideal PI substrate requires high heat resistance to withstand the high temperatures of 300-500°C during LTPS-TFT processing, and also needs a low coefficient of thermal expansion (CTE) to prevent delamination and curling during processing. Therefore, designing and developing transparent polyimide monomer materials with excellent comprehensive performance, balancing mechanical, optical, and electrical properties, is of great significance to the development of the semiconductor industry. Currently, polyimide diamine monomers containing double bonds are a research hotspot in this industry. However, the preparation process of polyimide diamine monomers containing double bonds is quite complicated. In the existing preparation methods, most of the nitro reduction uses iron powder reduction. For example, the methods disclosed in publication numbers CN101321845A, WO2022045120A1 and CN105492965A use iron powder reduction, but this process is relatively outdated and causes significant pollution. Patent application CN116375591A discloses a method for preparing polyimide diamine monomers containing double bonds. This preparation method uses the combined action of diboronic acid and 4,4'-bipyridine as an efficient reduction system to selectively reduce nitro groups while retaining double bonds and ester groups, thereby obtaining polyimide diamine monomers with double bonds. However, in this method, when 4,4'-bipyridine is added for reaction, the system is violently exothermic and requires the use of an ice-water bath for cooling. The reaction is poorly controllable, and if the temperature in the system is not properly controlled, it will lead to an increase in side reactions, affecting the yield and purity of the final product, and making it difficult to scale up production.

[0005] In addition, some reaction routes are used, which have long reaction steps, low yields and high costs. These methods often cannot obtain high yields and high purity of polyimide diamine monomers containing double bonds and ester groups. Therefore, developing new synthetic routes is of great value. Summary of the Invention

[0006] This invention addresses the shortcomings of existing technologies by providing a method for preparing polyimide diamine monomers. The method utilizes an efficient and inexpensive reduction system to reduce nitro groups while retaining double bonds and ester groups to obtain the polyimide diamine monomer containing double bonds and ester groups. This synthetic route has short reaction steps, high yield, low cost, and simple preparation, which is conducive to large-scale production and has broad application prospects.

[0007] The technical solution of this invention to solve the above-mentioned technical problems is as follows: A method for preparing a polyimide diamine monomer, wherein the preparation method comprises: S1, reacting reactant I with a reducing agent to obtain intermediate I; the structural formula of reactant I is: The structural formula of the intermediate I is: ;

[0008] S2, intermediate I, and reactant II react to obtain intermediate II; the structural formula of reactant II is: The structural formula of intermediate II is: S3. Preparation of polyimide diamine monomer using intermediate II:

[0009] Under inert gas protection, intermediate II, Raney nickel, glacial acetic acid, pyridine, and sodium hypophosphite aqueous solution were added to a solvent to carry out the reaction, and after post-treatment, polyimide diamine monomer was obtained.

[0010] The polyimide diamine monomer is: ;

[0011] Wherein, R1 is a single bond or an alkylene group consisting of 1-5 carbon atoms, or any one of -O-, -CONH-, -NHCO-, -COO-, -OCO-, -NH-, -CO-; R2 is R3 is any one of hydrogen, alkyl or polycyclic heterocycles consisting of 1-5 carbon atoms, and the heteroatom on the heterocycle is a nitrogen atom or an oxygen atom; any methylene group on R3 can be replaced by any one of -O-, -CONH-, -NHCO-, -COO-, -OCO-, -NH-, -CO-, and one or more hydrogen atoms in the alkyl or polycyclic heterocycle consisting of 1-5 carbon atoms can be replaced by fluorine atoms or alkyl groups consisting of 1-5 carbon atoms.

[0012] Furthermore, R1 is any one of the following: single bond, -CH2-, -CH2CH2-, -CH2CH2CH2-, -CH2CH2CH2CH2-, -CH2CH2CH2CH2CH2-, -O-, -CONH-, -NHCO-, -COO-, -OCO-, -NH-, -CO-;

[0013] The R3 is any one of hydrogen, -CH3, -CH2CH3, -CH2CH2CH3, -CH2CH2CH2CH3, -CH2CH2CH2CH2CH3, -CF3, and polycyclic heterocycles.

[0014] Furthermore, the structural formula of the polyimide diamine monomer is selected from any one of the following structures:

[0015] ; ; ; ; ; ; ; .

[0016] Furthermore, the reducing agent used in the preparation of intermediate I is boranetetrahydrofuran; the catalyst used in the preparation of intermediate II is DMAP or triphenylphosphine; and the dehydrating agent used in the preparation of intermediate II is DCC or DIAD.

[0017] Furthermore, the solvent used in step S1 to prepare intermediate I is at least one of tetrahydrofuran and dichloromethane;

[0018] The solvent used in step S2 to prepare intermediate II is at least one of dichloromethane, tetrahydrofuran, and toluene;

[0019] The solvent used in step S3 to prepare the polyimide diamine monomer is at least one of water, ethanol, and methanol.

[0020] Furthermore, the reaction temperature in step S1 is 20-25℃; the reaction temperature in step S2 is 15-25℃; and the reaction temperature in step S3 is 50-60℃.

[0021] Furthermore, in step S1, the molar ratio of reactant I to reducing agent is 1:(1.2-1.6).

[0022] In step S2, the molar ratio of intermediate I to reactant II is 1:(1-1.1), the molar ratio of intermediate I to catalyst is 1:(0.1-0.15), and the molar ratio of intermediate I to dehydrating agent is 1:(1-1.1).

[0023] In step S3, the molar ratio of intermediate II to Raney nickel is 1:(5-6), the molar ratio of intermediate II to glacial acetic acid is 1:(5-6), the molar ratio of intermediate II to pyridine is 1:(8-9), and the molar ratio of intermediate II to sodium hypophosphite is 1:(10-12).

[0024] Furthermore, in step S1, after the reaction is complete, ethanol is added to quench the reaction, remove the solvent, and purify using a water-based pulping system to obtain intermediate I.

[0025] Furthermore, in step S2, after the reaction is complete, the byproducts are removed by solid-liquid separation, and the liquid phase after solid-liquid separation is passed through a column and recrystallized to obtain intermediate II.

[0026] Furthermore, in step S3, after the reaction is completed, the reaction system is extracted with an organic solvent, the insoluble matter is filtered off, the organic phase is repeatedly acid-washed and water-washed, the organic solvent is removed, the solution is prepared, column chromatography is performed, and recrystallization is performed to obtain the polyimide diamine monomer.

[0027] The beneficial effects of this invention are:

[0028] The preparation method described in this invention utilizes a highly efficient and inexpensive reduction system. The combined action of Raney nickel, glacial acetic acid, pyridine, and sodium hypophosphite aqueous solution constitutes the reduction system. This system slowly generates reducing hydrogen gas. Under the influence of this reducing hydrogen gas within the system, various nitrobenzenes and nitro aromatic hydrocarbon derivatives are selectively reduced. Other functional groups sensitive to catalytic hydrogenation reactions, such as ester groups and double bonds, remain unaffected. This allows for the preparation of polyimide diamine monomers containing double bonds and ester groups with excellent overall performance. The reaction process is more controllable, and the preparation method is simple. Compared to the scheme in patent CN116375591A, this method is milder and more controllable, facilitating scale-up production and large-scale application. Furthermore, the synthetic route of this invention provides valuable reference for the synthesis of other amino compounds containing cinnamic acid structures.

[0029] The preparation method described in this invention has short reaction steps, high yield, high product purity, and low cost, which is conducive to large-scale production. Attached Figure Description

[0030] Figure 1 The methyl ester (3,5-dinitrophenyl)-3-phenyl-2-acrylate in Example 1 1 H-NMR spectrum;

[0031] Figure 2 for Figure 1 Methyl (3,5-dinitrophenyl)-3-phenyl-2-acrylate with chemical shifts of 5.0-9.2 1 H-NMR spectrum;

[0032] Figure 3 The methyl ester (3,5-diaminophenyl)-3-phenyl-2-acrylate in Example 1 1 H-NMR spectrum;

[0033] Figure 4 for Figure 2 Methyl (3,5-diaminophenyl)-3-phenyl-2-acrylate with chemical shifts of 5.8-7.9 1 H-NMR spectrum;

[0034] Figure 5 The image shows the HPLC-MS chromatogram of methyl 3,5-diaminophenyl)-3-phenyl-2-acrylate from Example 1. Detailed Implementation

[0035] To make the above-mentioned objects, features, and advantages of the present invention more apparent and understandable, specific embodiments of the present invention are described in detail below. Many specific details are set forth in the following description to provide a thorough understanding of the present invention. However, the present invention can be practiced in many other ways different from those described herein, and those skilled in the art can make similar modifications without departing from the spirit of the present invention. Therefore, the present invention is not limited to the specific embodiments disclosed below.

[0036] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains. The terminology used herein in the description of the invention is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention.

[0037] A method for preparing a polyimide diamine monomer, wherein the preparation method comprises:

[0038] S1. Preparation of intermediate I:

[0039] Under inert gas protection, in a solvent, with the system temperature controlled, reactant I reacts with a reducing agent. After the reaction is complete, after post-processing, intermediate I is obtained.

[0040] The structural formula of reactant I is: ;

[0041] S2. Preparation of intermediate II:

[0042] Under inert gas protection, in a solvent, and with the help of a catalyst and a dehydrating agent, intermediate I and reactant II react. After the reaction is complete, post-processing is performed to obtain intermediate II.

[0043] The structural formula of reactant II is: ;

[0044] The structural formula of intermediate II is: ;

[0045] Preparation of S3, polyimide diamine monomer:

[0046] Under inert gas protection, intermediate II, Raney nickel, glacial acetic acid, pyridine, and sodium hypophosphite aqueous solution were added to a solvent to carry out the reaction. After the reaction was completed, the polyimide diamine monomer was obtained through post-treatment.

[0047] The structural formula of the polyimide diamine monomer is: ;

[0048] Wherein, R1 is a single bond or an alkylene group consisting of 1-5 carbon atoms, or any one of -O-, -CONH-, -NHCO-, -COO-, -OCO-, -NH-, -CO-; R2 is R3 is any one of hydrogen, alkyl or polycyclic heterocycles consisting of 1-5 carbon atoms, and the heteroatom on the heterocycle is a nitrogen atom or an oxygen atom; any methylene group on R3 can be replaced by any one of -O-, -CONH-, -NHCO-, -COO-, -OCO-, -NH-, -CO-, and one or more hydrogen atoms in the alkyl or polycyclic heterocycle consisting of 1-5 carbon atoms can be replaced by fluorine atoms or alkyl groups consisting of 1-5 carbon atoms.

[0049] Specifically, R1 is any one of the following: single bond, -CH2-, -CH2CH2-, -CH2CH2CH2-, -CH2CH2CH2CH2-, -CH2CH2CH2CH2CH2-, -O-, -CONH-, -NHCO-, -COO-, -OCO-, -NH-, -CO-;

[0050] The R3 is any one of hydrogen, -CH3, -CH2CH3, -CH2CH2CH3, -CH2CH2CH2CH3, -CH2CH2CH2CH2CH3, -CF3, and polycyclic heterocycles.

[0051] Specifically, the structural formula of the polyimide diamine monomer is selected from any one of the following structures:

[0052] ; ; ; ; ; ; ; .

[0053] Specifically, the reducing agent used in the preparation of intermediate I is boranetetrahydrofuran; the catalyst used in the preparation of intermediate II is DMAP or triphenylphosphine; and the dehydrating agent used in the preparation of intermediate II is DCC or DIAD.

[0054] More specifically, the borane used in the embodiments of the present invention is a complex of diborane and tetrahydrofuran, with the chemical formula BH3·THF.

[0055] Specifically, the solvent used in step S1 to prepare intermediate I is at least one of tetrahydrofuran and dichloromethane;

[0056] The solvent used in step S2 to prepare intermediate II is at least one of dichloromethane, tetrahydrofuran, and toluene;

[0057] The solvent used in step S3 to prepare the polyimide diamine monomer is at least one of water, ethanol, and methanol.

[0058] Specifically, the reaction temperature for step S1 is 20-25℃; the reaction temperature for step S2 is 15-25℃; and the reaction temperature for step S3 is 50-60℃.

[0059] Specifically, in step S1, the molar ratio of reactant I to reducing agent is 1:(1.2-1.6).

[0060] In step S2, the molar ratio of intermediate I to reactant II is 1:(1-1.1), the molar ratio of intermediate I to catalyst is 1:(0.1-0.15), and the molar ratio of intermediate I to dehydrating agent is 1:(1-1.1).

[0061] In step S3, the molar ratio of intermediate II to Raney nickel is 1:(5-6), the molar ratio of intermediate II to glacial acetic acid is 1:(5-6), the molar ratio of intermediate II to pyridine is 1:(8-9), and the molar ratio of intermediate II to sodium hypophosphite is 1:(10-12).

[0062] Specifically, in step S1, after the reaction is complete, ethanol is added to quench the reaction, remove the solvent, and purify using a water-based pulping system to obtain intermediate I.

[0063] Specifically, in step S2, after the reaction is complete, the byproducts are removed by solid-liquid separation, and the liquid phase of the solid-liquid separation is passed through a column and recrystallized to obtain intermediate II.

[0064] Specifically, in step S3, after the reaction is completed, the reaction system is extracted with an organic solvent, the insoluble matter is filtered off, the organic phase is repeatedly acid-washed and water-washed, the organic solvent is removed, the solution is prepared, column chromatography is performed, and recrystallization is performed to obtain the polyimide diamine monomer.

[0065] Example 1

[0066] The preparation of methyl (3,5-diaminophenyl)-3-phenyl-2-acrylate includes the following steps:

[0067] ;

[0068] (1) Preparation of 3,5-dinitrobenzyl alcohol:

[0069] Under nitrogen protection, 42.4 g (0.2 mol) of 3,5-dinitrobenzene and 172.8 g of tetrahydrofuran were added to a clean and dry three-necked flask. The mixture was mechanically stirred until all the solids in the system were dissolved and the system was light brownish-yellow and transparent.

[0070] Under nitrogen protection, the temperature inside the system was controlled at 20-25℃. 258g (actually containing 0.3mol borane) of borane tetrahydrofuran solution (concentration of 10%) was gradually added dropwise to the three-necked flask. After the addition was completed, the flask was kept at 20-25℃ for 3 hours. After the reaction was completed, the reaction solution was obtained and then quenched.

[0071] Under nitrogen protection, 200.0 g of anhydrous ethanol was added to a clean and dry three-necked flask. The anhydrous ethanol was preheated to <-5℃. The reaction solution was added dropwise to the anhydrous ethanol in the three-necked flask. The temperature inside the three-necked flask was controlled at -5 to 0℃ for quenching. After quenching, the mixture was stirred for 30 minutes. Then, 202.0 g of softened water was added and the mixture was stirred for another 30 minutes to remove most of the tetrahydrofuran and ethanol from the system. The system was heated to 50-55℃ and slurried with water for 1 hour. Then, the mixture was cooled, filtered, and dried to obtain 3,5-dinitrobenzyl alcohol with a purity of 98.0% and a yield of 96%.

[0072] (2) Preparation of methyl 3-(3,5-dinitrophenyl)-3-phenyl-2-acrylate:

[0073] Under nitrogen protection, add 53.46 g (0.27 mol) of 3,5-dinitrobenzyl alcohol, 3.66 g (0.03 mol) of DMAP, 41.88 g (0.283 mol) of cinnamic acid, and 500.0 g of dichloromethane to a clean and dry three-necked flask, and stir until the system is completely dissolved while maintaining the internal temperature at 15-25°C.

[0074] Under nitrogen protection, a solution prepared with 58.6 g (0.284 mol) DCC and 116.7 g dichloromethane was added dropwise at an internal temperature controlled at 15–25 °C. After addition, the reaction was maintained at this temperature for 2 hours, filtered, and washed with 300.0 g dichloromethane. The filtrate and eluent were collected and passed through a 60.0 g neutral alumina column. After column chromatography, the column was washed with 500.0 g dichloromethane. The column chromatography solution and eluent were combined and the solvent was removed. A solution was prepared with 708.0 g tetrahydrofuran and passed through a 60.0 g silica gel column. The column was washed with tetrahydrofuran, and the column chromatography solution and eluent were combined and the solvent was removed. The crude product was recrystallized from tetrahydrofuran to obtain methyl (3,5-dinitrophenyl)-3-phenyl-2-acrylate with a purity of 99.0% and a yield of 90%. 1 H-NMR, see Figures 1-2 .

[0075] (3) Preparation of methyl 3,5-diaminophenyl)-3-phenyl-2-acrylate:

[0076] Under nitrogen protection, add 30g (0.091mol) (3,5-dinitrophenyl) 3-phenyl-2-acrylate, 29.4g (0.501mol) Raney nickel, 30.1g (0.501mol) glacial acetic acid, 61.2g (0.774mol) pyridine, and 60.0g water to a clean and dry three-necked flask, stir, and heat the system to 50°C.

[0077] Under nitrogen protection, 88.1 g (1.0 mol) of sodium hypophosphite (33.33% aqueous solution) was added dropwise. The dropwise addition process was exothermic and gas was released. The temperature was controlled at 50-60℃ and the reaction was maintained for 1 hour. After all the raw materials and intermediates were converted into the product (the remaining raw materials and intermediates were tracked by TLC during the reaction, and the developing solvent was ethyl acetate), the reaction was stopped and the temperature was lowered to 20-30℃.

[0078] Under nitrogen protection, 300g of dichloromethane was added to a three-necked flask and stirred thoroughly for extraction. Insoluble matter was filtered off, and the mixture was allowed to stand for separation. The aqueous phase was separated, and the organic phase was washed once with 5% hydrochloric acid and then three times with water until neutral. The solvent was removed, and the solution was prepared using a 2:1 mixture of tetrahydrofuran and n-hexane and passed through a 36.6g silica gel column. The column was eluted with a mixture of tetrahydrofuran and n-hexane, and the eluents were combined and dried. Recrystallization using a toluene-ethanol system yielded the target product (3,5-diaminophenyl)-3-phenyl-2-acrylate with a purity of 99.0% and a yield of 92%. Testing was performed. 1 H-NMR and HPLC-MS, see Figures 3-5 .

[0079] Example 2

[0080] The preparation of methyl (3,5-diaminophenyl)-3-phenyl-2-acrylate includes the following steps:

[0081] (1) Preparation of 3,5-dinitrobenzyl alcohol:

[0082] Under nitrogen protection, 42.4 g (0.2 mol) of 3,5-dinitrobenzene and 173 g of tetrahydrofuran were added to a clean and dry three-necked flask. The mixture was mechanically stirred until all the solids in the system were dissolved and the system was light brownish-yellow and transparent.

[0083] Under nitrogen protection, the temperature inside the system was controlled at 20-25℃. 206g (actually containing 0.24mol borane) of borane tetrahydrofuran solution (concentration of 10%) was gradually added dropwise to the three-necked flask. After the addition was completed, the flask was kept at 20-25℃ for 3 hours. After the reaction was completed, the reaction solution was obtained and then quenched.

[0084] Under nitrogen protection, 200.0 g of anhydrous ethanol was added to a clean and dry three-necked flask. The anhydrous ethanol was preheated to <-5℃. The reaction solution was added dropwise to the anhydrous ethanol in the three-necked flask. The temperature inside the three-necked flask was controlled at -5 to 0℃ for quenching. After quenching, the mixture was stirred for 30 minutes. Then, 202.0 g of softened water was added and the mixture was stirred for another 30 minutes to remove most of the tetrahydrofuran and ethanol from the system. The system was heated to 50-55℃ and slurried with water for 1 hour. Then, the mixture was cooled, filtered, and dried to obtain 3,5-dinitrobenzyl alcohol with a purity of 97.0% and a yield of 95.6%.

[0085] (2) Preparation of methyl 3-(3,5-dinitrophenyl)-3-phenyl-2-acrylate:

[0086] Under nitrogen protection, add 53.46 g (0.27 mol) of 3,5-dinitrobenzyl alcohol, 4.94 g (0.0405 mol) of DMAP, 43.96 g (0.297 mol) of cinnamic acid, and 500.0 g of dichloromethane to a clean and dry three-necked flask, and stir until the system is completely dissolved while maintaining the internal temperature at 15-25°C.

[0087] Under nitrogen protection, a solution prepared with 61.28 g (0.297 mol) DCC and 116.7 g dichloromethane was added dropwise at an internal temperature controlled at 15–25 °C. After the addition was complete, the reaction was maintained at this temperature for 2 hours, filtered, and washed with 300.0 g dichloromethane. The filtrate and eluent were collected and passed through a 60.0 g neutral alumina column. After column chromatography, the column was washed with 500.0 g dichloromethane. The column chromatography solution and eluent were combined and the solvent was removed. A solution was prepared with 708.0 g tetrahydrofuran and passed through a 60.0 g silica gel column. The column was washed with tetrahydrofuran, and the column chromatography solution and eluent were combined and the solvent was removed. The crude product was recrystallized from tetrahydrofuran to obtain methyl (3,5-dinitrophenyl)-3-phenyl-2-acrylate with a purity of 98.0% and a yield of 89%.

[0088] (3) Preparation of methyl 3,5-diaminophenyl)-3-phenyl-2-acrylate:

[0089] Under nitrogen protection, add 30 g (0.091 mol) (3,5-dinitrophenyl) 3-phenyl-2-acrylate, 29.4 g (0.501 mol) Raney nickel, 30.1 g (0.501 mol) glacial acetic acid, 61.2 g (0.774 mol) pyridine, and 60.0 g ethanol to a clean and dry three-necked flask, stir, and heat the system to 50 °C.

[0090] Under nitrogen protection, 88.1 g (1.0 mol) of sodium hypophosphite (33.33% aqueous solution) was added dropwise. The dropwise addition process was exothermic and gas was released. The temperature was controlled at 50-60℃ and the reaction was maintained for 1 hour. After all the raw materials and intermediates were converted into the product (the remaining raw materials and intermediates were tracked by TLC during the reaction, and the developing solvent was ethyl acetate), the reaction was stopped and the temperature was lowered to 20-30℃.

[0091] Under nitrogen protection, 300g of dichloromethane was added to a three-necked reaction flask and stirred thoroughly for extraction. The insoluble matter in the system was filtered off, and the mixture was allowed to stand for separation. The aqueous phase was separated, and the organic phase was washed once with 5% hydrochloric acid and then washed three times with water until the organic phase was neutral. The solvent was removed, and the solution was prepared by passing it through a 36.6g silica gel column using a tetrahydrofuran:n-hexane = 2:1 mixture. The column was eluted with a mixture of tetrahydrofuran andn-hexane. The column eluents were combined and dried. The product (3,5-diaminophenyl)3-phenyl-2-acrylate was obtained by recrystallization using a toluene-ethanol system, with a purity of 99.0% and a yield of 89.6%.

[0092] Example 3

[0093] The preparation of methyl (3,5-diaminophenyl)-3-phenyl-2-acrylate includes the following steps:

[0094] (1) Preparation of 3,5-dinitrobenzyl alcohol:

[0095] Under nitrogen protection, 42.4 g (0.2 mol) of 3,5-dinitrobenzene and 173 g of tetrahydrofuran were added to a clean and dry three-necked flask. The mixture was mechanically stirred until all the solids in the system were dissolved and the system was light brownish-yellow and transparent.

[0096] Under nitrogen protection, the temperature inside the system was controlled at 20-22℃. 275g (actually containing 0.32mol borane) of borane tetrahydrofuran solution (concentration 10%) was gradually added dropwise to the three-necked flask. After the addition was completed, the flask was kept at 20-22℃ for 3 hours. After the reaction was completed, the reaction solution was obtained and then quenched.

[0097] Under nitrogen protection, 200.0 g of anhydrous ethanol was added to a clean and dry three-necked flask. The anhydrous ethanol was preheated to <-5℃. The reaction solution was added dropwise to the anhydrous ethanol in the three-necked flask. The temperature inside the three-necked flask was controlled at -5 to 0℃ for quenching. After quenching, the mixture was stirred for 30 minutes. Then, 202.0 g of softened water was added and the mixture was stirred for another 30 minutes to remove most of the tetrahydrofuran and ethanol from the system. The system was heated to 50-55℃ and slurried with water for 1 hour. Then, the mixture was cooled, filtered, and dried to obtain 3,5-dinitrobenzyl alcohol with a purity of 97.0% and a yield of 96.0%.

[0098] (2) Preparation of methyl 3-(3,5-dinitrophenyl)-3-phenyl-2-acrylate:

[0099] Under nitrogen protection, add 53.46 g (0.27 mol) of 3,5-dinitrobenzyl alcohol, 3.29 g (0.027 mol) of DMAP, 39.96 g (0.27 mol) of cinnamic acid, and 500.0 g of dichloromethane to a clean and dry three-necked flask, and stir until the system is completely dissolved while maintaining the internal temperature at 15-20°C.

[0100] Under nitrogen protection, a solution prepared with 55.71 g (0.27 mol) DCC and 116.7 g dichloromethane was added dropwise at an internal temperature controlled at 15–20 °C. After the addition was complete, the reaction was maintained at this temperature for 2 hours, filtered, and washed with 300.0 g dichloromethane. The filtrate and eluent were collected and passed through a 60.0 g neutral alumina column. After column chromatography, the column was washed with 500.0 g dichloromethane. The column chromatography solution and eluent were combined and the solvent was removed. A solution was prepared with 708.0 g tetrahydrofuran and passed through a 60.0 g silica gel column. The column was washed with tetrahydrofuran, and the column chromatography solution and eluent were combined and the solvent was removed. The crude product was recrystallized from tetrahydrofuran to obtain methyl (3,5-dinitrophenyl)-3-phenyl-2-acrylate with a purity of 98% and a yield of 88%.

[0101] (3) Preparation of methyl 3,5-diaminophenyl)-3-phenyl-2-acrylate:

[0102] Under nitrogen protection, add 30g (0.091mol) methyl 3-phenyl-2-acrylate (3,5-dinitrophenyl) 29.4g (0.501mol) Raney nickel, 30.1g (0.501mol) glacial acetic acid, 61.2g (0.774mol) pyridine, and 60.0g methanol to a clean and dry three-necked flask, stir, and heat the system to 50°C.

[0103] Under nitrogen protection, 88.1 g (1.0 mol) of sodium hypophosphite (33.33% aqueous solution) was added dropwise. The dropwise addition process was exothermic and gas was released. The temperature was controlled at 50-60℃ and the reaction was maintained for 1 hour. After all the raw materials and intermediates were converted into the product (the remaining raw materials and intermediates were tracked by TLC during the reaction, and the developing solvent was ethyl acetate), the reaction was stopped and the temperature was lowered to 20-30℃.

[0104] Under nitrogen protection, 300g of dichloromethane was added to a three-necked reaction flask and stirred thoroughly for extraction. The insoluble matter in the system was filtered off, and the mixture was allowed to stand for separation. The aqueous phase was separated, and the organic phase was washed once with 5% hydrochloric acid and then washed three times with water until the organic phase was neutral. The solvent was removed, and the solution was prepared by passing it through a 36.6g silica gel column using a tetrahydrofuran:n-hexane = 2:1 mixture. The column was then eluted with a mixture of tetrahydrofuran andn-hexane. The eluents were combined and dried, and the product (3,5-diaminophenyl)3-phenyl-2-acrylate methyl ester was obtained by recrystallization using a toluene-ethanol system with a purity of 99.0% and a yield of 90%.

[0105] Example 4

[0106] The preparation of methyl (3,5-diaminophenyl)-3-phenyl-2-acrylate includes the following steps:

[0107] (1) Preparation of 3,5-dinitrobenzyl alcohol:

[0108] Under nitrogen protection, 42.4 g (0.2 mol) of 3,5-dinitrobenzic acid and 172.8 g of dichloromethane were added to a clean and dry three-necked flask. The mixture was mechanically stirred until all the solids in the system were dissolved and the system was light brownish-yellow and transparent.

[0109] Under nitrogen protection, the temperature inside the system was controlled at 20-25℃. 260g (actually containing 0.32mol borane) of borane tetrahydrofuran solution was gradually added dropwise to the three-necked flask. After the addition was completed, the flask was kept at 20-25℃ for 3 hours. After the reaction was completed, the reaction solution was obtained and then quenched.

[0110] Under nitrogen protection, 200.0 g of anhydrous ethanol was added to a clean and dry three-necked flask. The anhydrous ethanol was preheated to <-5℃. The reaction solution was added dropwise to the anhydrous ethanol in the three-necked flask. The temperature inside the three-necked flask was controlled at -5 to 0℃ for quenching. After quenching, the mixture was stirred for 30 minutes. Then, 202.0 g of softened water was added and the mixture was stirred for another 30 minutes to remove most of the dichloromethane and ethanol from the system. The system was heated to 50-55℃ and slurried with water for 1 hour. Then, the mixture was cooled, filtered, and dried to obtain 3,5-dinitrobenzyl alcohol with a purity of 95.0% and a yield of 93.5%.

[0111] (2) Preparation of methyl 3-(3,5-dinitrophenyl)-3-phenyl-2-acrylate:

[0112] Under nitrogen protection, add 53.46 g (0.27 mol) 3,5-dinitrobenzyl alcohol, 74.5 g (0.284 mol) triphenylphosphine, 41.88 g (0.283 mol) cinnamic acid, and 500.0 g toluene to a clean and dry three-necked flask, and stir until the system is homogeneous while maintaining the internal temperature at 15-20℃.

[0113] Under nitrogen protection, a solution prepared with 57.4 g (0.284 mol) DIAD and 116.7 g toluene was added dropwise at an internal temperature controlled at 15–20 °C. After the addition was complete, the reaction was maintained at this temperature for 2 hours, filtered, and washed with 300.0 g toluene. The filtrate and eluent were collected and passed through a 60.0 g silica gel column. After column chromatography, the column was washed with 500.0 g toluene. The column chromatography solution and eluent were combined and the solvent was removed. A solution was prepared with 708.0 g tetrahydrofuran and passed through a 60.0 g silica gel column. The column was washed with tetrahydrofuran, and the column chromatography solution and eluent were combined and the solvent was removed. The crude product was recrystallized from tetrahydrofuran to obtain methyl (3,5-dinitrophenyl)-3-phenyl-2-acrylate with a purity of 96.0% and a yield of 89.5%.

[0114] (3) Preparation of methyl 3,5-diaminophenyl)-3-phenyl-2-acrylate:

[0115] Under nitrogen protection, add 30g (0.091mol) (3,5-dinitrophenyl) 3-phenyl-2-acrylate, 29.4g (0.501mol) Raney nickel, 30.1g (0.501mol) glacial acetic acid, 30.6g (0.387mol) pyridine, and 60.0g water to a clean and dry three-necked flask, stir, and heat the system to 50°C.

[0116] Under nitrogen protection, 88.1 g (1.0 mol) of sodium hypophosphite (33.33% aqueous solution) was added dropwise. The dropwise addition process was exothermic and gas was released. The temperature was controlled at 50-60℃ and the reaction was maintained for 2 hours. After all the raw materials and intermediates were converted into the product (the remaining raw materials and intermediates were tracked by TLC during the reaction, and the developing solvent was ethyl acetate), the reaction was stopped and the temperature was lowered to 20-30℃.

[0117] Under nitrogen protection, 300g of dichloromethane was added to a three-necked reaction flask and stirred thoroughly for extraction. The insoluble matter in the system was filtered off, and the mixture was allowed to stand for separation. The aqueous phase was separated, and the organic phase was washed once with 5% hydrochloric acid and then three times with water until the organic phase was neutral. The solvent was removed, and the solution was prepared by passing it through a 36.6g silica gel column using a tetrahydrofuran:n-hexane = 2:1 mixture. The column was then eluted with a mixture of tetrahydrofuran andn-hexane. The eluents were combined and dried, and the product (3,5-diaminophenyl)3-phenyl-2-acrylate was obtained by recrystallization using a toluene-ethanol system. The purity was 99.0%, and the yield was 89%.

[0118] Example 5

[0119] The preparation of ethyl (3,5-diaminophenyl)-3-phenyl-2-acrylate includes the following steps:

[0120] (1) Preparation of 3,5-dinitrophenylethanol:

[0121] Under nitrogen protection, 45.2 g (0.2 mol) of 3,5-dinitrophenylacetic acid and 173 g of tetrahydrofuran were added to a clean and dry three-necked flask. The mixture was mechanically stirred until all the solids in the system were dissolved and the system was light brownish-yellow and transparent.

[0122] Under nitrogen protection, the temperature inside the system was controlled at 20-25℃. 206g (actually containing 0.24mol borane) of borane tetrahydrofuran solution (concentration of 10%) was gradually added dropwise to the three-necked flask. After the addition was completed, the flask was kept at 20-25℃ for 3 hours. After the reaction was completed, the reaction solution was obtained and then quenched.

[0123] Under nitrogen protection, 200.0 g of anhydrous ethanol was added to a clean and dry three-necked flask. The anhydrous ethanol was preheated to <-5℃. The reaction solution was added dropwise to the anhydrous ethanol in the three-necked flask. The temperature inside the three-necked flask was controlled at -5 to 0℃ for quenching. After quenching, the mixture was stirred for 30 minutes. Then, 202.0 g of softened water was added and the mixture was stirred for another 30 minutes to remove most of the tetrahydrofuran and ethanol from the system. The system was heated to 50-55℃ and slurried with water for 1 hour. Then, the mixture was cooled, filtered, and dried to obtain 3,5-dinitrophenylethanol with a purity of 97.5% and a yield of 95.0%.

[0124] (2) Preparation of ethyl (3,5-dinitrophenyl)-3-phenyl-2-acrylate:

[0125] Under nitrogen protection, add 57.24 g (0.27 mol) of 3,5-dinitrophenylethanol, 4.94 g (0.0405 mol) of DMAP, 43.96 g (0.297 mol) of cinnamic acid, and 500.0 g of dichloromethane to a clean and dry three-necked flask, and stir until the system is completely dissolved while maintaining the internal temperature at 15-25°C.

[0126] Under nitrogen protection, a solution prepared with 61.28 g (0.297 mol) DCC and 116.7 g dichloromethane was added dropwise at an internal temperature controlled at 15–25 °C. After the addition was complete, the reaction was maintained at this temperature for 2 hours, filtered, and washed with 300.0 g dichloromethane. The filtrate and eluent were collected and passed through a 60.0 g neutral alumina column. After column chromatography, the column was washed with 500.0 g dichloromethane. The column chromatography solution and eluent were combined and the solvent was removed. A solution was prepared with 708.0 g tetrahydrofuran and passed through a 60.0 g silica gel column. The column was washed with tetrahydrofuran, and the column chromatography solution and eluent were combined and the solvent was removed. The crude product was recrystallized from tetrahydrofuran to obtain ethyl (3,5-dinitrophenyl)-3-phenyl-2-acrylate with a purity of 98.3% and a yield of 88.6%.

[0127] (3) Preparation of ethyl (3,5-diaminophenyl)-3-phenyl-2-acrylate:

[0128] Under nitrogen protection, add 31.27 g (0.091 mol) (3,5-dinitrophenyl) 3-phenyl-2-acrylate, 29.4 g (0.501 mol) Raney nickel, 30.1 g (0.501 mol) glacial acetic acid, 61.2 g (0.774 mol) pyridine, and 60.0 g ethanol to a clean and dry three-necked flask, stir, and heat the system to 50 °C.

[0129] Under nitrogen protection, 88.1 g (1.0 mol) of sodium hypophosphite (33.33% aqueous solution) was added dropwise. The dropwise addition process was exothermic and gas was released. The temperature was controlled at 50-60℃ and the reaction was maintained for 1 hour. After all the raw materials and intermediates were converted into the product (the remaining raw materials and intermediates were tracked by TLC during the reaction, and the developing solvent was ethyl acetate), the reaction was stopped and the temperature was lowered to 20-30℃.

[0130] Under nitrogen protection, 300g of dichloromethane was added to a three-necked reaction flask and stirred thoroughly for extraction. The insoluble matter in the system was filtered off, and the mixture was allowed to stand for separation. The aqueous phase was separated, and the organic phase was washed once with 5% hydrochloric acid and then washed three times with water until the organic phase was neutral. The solvent was removed, and the solution was prepared by passing it through a 36.6g silica gel column using a tetrahydrofuran:n-hexane = 2:1 mixture. The column was eluted with a mixture of tetrahydrofuran andn-hexane. The eluents were combined and dried, and the product (3,5-diaminophenyl)3-phenyl-2-acrylate was obtained by recrystallization using a toluene-ethanol system. The purity was 99.1% and the yield was 89.7%.

[0131] Comparative Example 1

[0132] Methyl 3,5-diaminophenyl)3-phenyl-2-acrylate was prepared using the same method as in Example 1, except that pyridine was not added in step (3), while all other conditions were exactly the same.

[0133] In Comparative Example 1, the yield of the target product (3,5-diaminophenyl) methyl 3-phenyl-2-acrylate was only 10%, with most of the product undergoing hydrolysis.

[0134] Comparative Example 2

[0135] Methyl 3,5-diaminophenyl)-3-phenyl-2-acrylate was prepared using the same method as in Example 1, except that sodium hypophosphite aqueous solution was not added in step (3), while all other conditions were exactly the same.

[0136] In Comparative Example 2, the target product (3,5-diaminophenyl) methyl 3-phenyl-2-acrylate was almost undetectable, and the yield was almost 0%.

[0137] Comparative Example 3

[0138] Methyl 3,5-diaminophenyl)3-phenyl-2-acrylate was prepared using the same method as in Example 1. The difference was that glacial acetic acid was not added in step (3). The target product (3,5-diaminophenyl)3-phenyl-2-acrylate could be detected, but the reaction rate was very slow. Even after 24 hours of heat preservation, there was still raw material remaining, and the yield of the target product was only 20%.

[0139] Comparative Example 4

[0140] Methyl 3,5-diaminophenyl)3-phenyl-2-acrylate was prepared using the same method as in Example 1. The difference was that Raney nickel was not added in step (3). The target product (3,5-diaminophenyl)3-phenyl-2-acrylate was completely undetectable, and the yield of the target product was 0%.

[0141] Comparative Example 5

[0142] Methyl 3,5-diaminophenyl)3-phenyl-2-acrylate was prepared using the same method as in Example 1. The difference was that in step (3), Raney nickel and hydrogen were used directly for the pressure reaction, and the yield of the target product was 0%.

[0143] The experimental results of Comparative Examples 1, 2, 3, 4, and 1 show that the preparation method of the present invention, by using a reduction system of Raney nickel, glacial acetic acid, pyridine, and sodium hypophosphite aqueous solution, can achieve good selective reducing properties to obtain the desired polyimide diamine monomer containing double bonds and ester groups. Raney nickel, glacial acetic acid, pyridine, and sodium hypophosphite are all indispensable; only when these substances are used in combination to form the reduction system can a good reducing effect be achieved. This reduction system slowly generates reducing hydrogen gas. Under the action of reducing hydrogen gas inside the system, various nitrobenzenes and various nitro aromatic hydrocarbon derivatives are selectively reduced. Other functional groups sensitive to catalytic hydrogenation reactions, such as ester groups and double bonds, are not affected.

[0144] Furthermore, a comparison of the experimental results of Comparative Example 5 and Example 1 shows that if a conventional hydrogenation reduction system is used, the yield of the polyimide diamine monomer containing double bonds and ester groups (i.e., methyl (3,5-diaminophenyl)3-phenyl-2-acrylate) decreases significantly or even fails to yield the product. This is because conventional reducing agents reduce the double bonds while reducing the nitro groups, resulting in poor reduction selectivity and ultimately a significant decrease in the yield of the target product or even failure to obtain the product. However, the reduction system described in this invention achieves excellent reduction selectivity, ultimately yielding a high-yield, high-purity polyimide diamine monomer containing double bonds and ester groups.

[0145] The technical features of the above embodiments can be combined in any way. For the sake of brevity, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0146] The embodiments described above are merely illustrative of several implementations of the present invention, and while the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the invention patent. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the present invention, and these all fall within the protection scope of the present invention. Therefore, the protection scope of this invention patent should be determined by the appended claims.

Claims

1. A method for preparing a polyimide diamine monomer, wherein the preparation method comprises: S1, reacting reactant I with a reducing agent to obtain intermediate I; the structural formula of reactant I is: The structural formula of the intermediate I is: ; S2, intermediate I, and reactant II react to obtain intermediate II; the structural formula of reactant II is: The structural formula of intermediate II is: S3. Using intermediate II to prepare polyimide diamine monomer, characterized in that, Under inert gas protection, intermediate II, Raney nickel, glacial acetic acid, pyridine, and sodium hypophosphite aqueous solution were added to a solvent to carry out the reaction, and after post-treatment, polyimide diamine monomer was obtained. The polyimide diamine monomer is: ; Wherein, R1 is any one of the following: single bond, -CH2-, -CH2CH2-, -CH2CH2CH2-, -CH2CH2CH2CH2-, -CH2CH2CH2CH2CH2-; R2 is... R3 is hydrogen.

2. The method for preparing a polyimide diamine monomer according to claim 1, characterized in that, The structural formula of the polyimide diamine monomer is selected from any one of the following structures: ； 。 3. The method for preparing a polyimide diamine monomer according to claim 1, characterized in that, The reducing agent used in the preparation of intermediate I is boranetetrahydrofuran; the catalyst used in the preparation of intermediate II is DMAP or triphenylphosphine; and the dehydrating agent used in the preparation of intermediate II is DCC or DIAD.

4. The method for preparing a polyimide diamine monomer according to claim 1, characterized in that, The solvent used in step S1 to prepare intermediate I is at least one of tetrahydrofuran and dichloromethane; The solvent used in step S2 to prepare intermediate II is at least one of dichloromethane, tetrahydrofuran, and toluene; The solvent used in step S3 to prepare the polyimide diamine monomer is at least one of water, ethanol, and methanol.

5. The method for preparing a polyimide diamine monomer according to claim 1, characterized in that, The reaction temperature for step S1 is 20-25℃; the reaction temperature for step S2 is 15-25℃; and the reaction temperature for step S3 is 50-60℃.

6. The method for preparing a polyimide diamine monomer according to claim 1, characterized in that, In step S1, the molar ratio of reactant I to reducing agent is 1:(1.2-1.6). In step S2, the molar ratio of intermediate I to reactant II is 1:(1-1.1), the molar ratio of intermediate I to catalyst is 1:(0.1-0.15), and the molar ratio of intermediate I to dehydrating agent is 1:(1-1.1). In step S3, the molar ratio of intermediate II to Raney nickel is 1:(5-6), the molar ratio of intermediate II to glacial acetic acid is 1:(5-6), the molar ratio of intermediate II to pyridine is 1:(8-9), and the molar ratio of intermediate II to sodium hypophosphite is 1:(10-12).

7. The method for preparing a polyimide diamine monomer according to claim 1, characterized in that, In step S1, after the reaction is complete, ethanol is added to quench the reaction, the solvent is removed, and the mixture is purified using a water-based pulping system to obtain intermediate I.

8. The method for preparing a polyimide diamine monomer according to claim 1, characterized in that, In step S2, after the reaction is complete, the byproducts are removed by solid-liquid separation. The liquid phase after solid-liquid separation is passed through a column and recrystallized to obtain intermediate II.

9. The method for preparing a polyimide diamine monomer according to claim 1, characterized in that, In step S3, after the reaction is complete, the reaction system is extracted with an organic solvent, the insoluble matter is filtered off, the organic phase is repeatedly acid-washed and water-washed, the organic solvent is removed, the solution is prepared, column chromatography is performed, and recrystallization is performed to obtain the polyimide diamine monomer.

Images