Preparation method of polyimide diamine monomer

Abstract

The invention relates to a preparation method of a polyimide diamine monomer, and belongs to the technical field of chemical synthesis. The preparation method comprises the following steps: (1) reacting a reactant I with a reducing agent in a solvent under the protection of inert gas to obtain an intermediate I; (2) reacting the intermediate I with the reactant II under the action of a catalyst and a dehydrating agent to obtain an intermediate II; and (3) adding the intermediate II, raney nickel, glacial acetic acid, pyridine and a sodium hypophosphite aqueous solution into the solvent under the protection of inert gas, reacting, and after the reaction is finished, performing post-treatment to obtain the polyimide diamine monomer. Raney nickel, glacial acetic acid, pyridine and a sodium hypophosphite system are used for reducing nitryl and retaining double bonds and ester groups to prepare the polyimide diamine monomer containing the double bond and ester group structure, so that a high-purity and high-yield target product is obtained, the reaction steps are short, the yield is high, the cost is low, the preparation method is simple, large-scale production is facilitated, and the method is suitable for industrial production. Wide application prospects are realized.

Description

Technical Field

[0001] The invention relates to a preparation method of a polyimide diamine monomer, belonging to the technical field of chemical synthesis. Background Art

[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 constant and good mechanical properties. Transparent polyimide materials have very broad application prospects in the field of optoelectronic devices that require optical properties, such as folding mobile phone screens, touch screens, flexible printed circuits and other fields.

[0003] Traditional engineering polyimide materials suffer from poor processing properties and dark color in finished products due to their rigid structure. These drawbacks have significantly limited their widespread application. In recent years, with the advancement of semiconductor material research, researchers have discovered that introducing bulky side chains, fluorine atoms, aliphatic chains, aliphatic ring structures, or asymmetric, non-coplanar structures into polyimides can produce polyimides with lighter colors and suitable for dissolution and subsequent coating.

[0004] When synthesizing polyimide materials used in the semiconductor industry, some common diamine or dianhydride monomers often struggle to balance optical properties, heat resistance, mechanical properties, and dielectric properties. For example, in the flexible substrate field, ideal PI substrates require high heat resistance to withstand the high temperatures of 300-500°C during LTPS-TFT processing, while also having a low coefficient of thermal expansion (CTE) to prevent delamination and warping during processing. Therefore, the design and development of transparent polyimide monomer materials with excellent overall performance, balancing mechanical, optical, and electrical properties, is of great significance to the development of the semiconductor industry. At present, polyimide diamine monomers containing double bonds are a research hotspot in the industry, but the preparation process of polyimide diamine monomers containing double bonds is relatively complicated. Among the existing preparation methods, most of the nitro reduction methods use iron powder reduction. For example, the methods disclosed in publication numbers CN101321845A, WO2022045120A1 and CN105492965A use iron powder reduction, but the process is relatively backward and polluting. A patent application with publication number CN116375591A discloses a preparation method for polyimide diamine monomers containing double bonds. In this preparation method, the combined action of diboric acid and 4,4'-bipyridine is used as an efficient reduction system to selectively reduce the nitro group, retain the double bond and ester group, and prepare a double-bonded polyimide diamine monomer. However, in this method, when 4,4'-bipyridine is added to the reaction, the system releases heat violently, requiring an ice-water bath for cooling. The reaction is poorly controllable. 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 there are great difficulties in scaling up production.

[0005] In addition, some methods use reaction routes with long reaction steps, low yield and high cost. These methods often cannot obtain high-yield and high-purity polyimide diamine monomers containing double bonds and ester groups. Therefore, the development of new synthetic routes is of great value. Summary of the Invention

[0006] The present invention addresses the deficiencies in the prior art and provides a method for preparing a polyimide diamine monomer. The method uses an efficient and inexpensive reduction system to reduce nitro groups while retaining double bonds and ester groups to prepare the polyimide diamine monomer containing double bonds and ester groups. The synthetic route has short reaction steps, high yield, low cost, simple preparation, is conducive to large-scale production, and has broad application prospects.

[0007] The technical solution of the present invention to solve the above technical problems is as follows: A method for preparing a polyimide diamine monomer, wherein the preparation method comprises: S1, reactant I reacts with a reducing agent to obtain an intermediate I; the structural formula of the 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 the reactant II is: ; The structural formula of intermediate II is: ; S3, using intermediate II to prepare polyimide diamine monomer: Under inert gas protection, intermediate II, Raney nickel, glacial acetic acid, pyridine and sodium hypophosphite aqueous solution are added to a solvent for reaction, and then post-treated to obtain a polyimide diamine monomer; The polyimide diamine monomer is: ; Wherein, R1 is a single bond or an alkylene group consisting of 1 to 5 carbon atoms or any one of -O-, -CONH-, -NHCO-, -COO-, -OCO-, -NH-, and -CO-; R2 is ; R3 is any one of hydrogen, an alkyl group consisting of 1-5 carbon atoms or a polycyclic heterocycle, and the heteroatom on the heterocycle is a nitrogen atom or an oxygen atom; and any methylene group on R3 can be replaced by any group of -O-, -CONH-, -NHCO-, -COO-, -OCO-, -NH-, -CO-, and one or more hydrogen atoms in the alkyl group consisting of 1-5 carbon atoms or the polycyclic heterocycle can be replaced by a fluorine atom or an alkyl group consisting of 1-5 carbon atoms.

[0008] Further, R1 is any one of a single bond, -CH2-, -CH2CH2-, -CH2CH2CH2-, -CH2CH2CH2CH2-, -CH2CH2CH2CH2CH2-, -O-, -CONH-, -NHCO-, -COO-, -OCO-, -NH-, and -CO-; The R3 is any one of hydrogen, -CH3, -CH2CH3, -CH2CH2CH3, -CH2CH2CH2CH3, -CH2CH2CH2CH2CH3, -CF3 and a polycyclic heterocycle.

[0009] Furthermore, the structural formula of the polyimide diamine monomer is selected from any one of the following structures: ; ; ; ; ; ; ; .

[0010] Furthermore, the reducing agent used in the preparation of intermediate I is borane tetrahydrofuran; 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.

[0011] Furthermore, the solvent used in the preparation of intermediate I in step S1 is at least one of tetrahydrofuran and dichloromethane; The solvent used in the preparation of intermediate II in step S2 is at least one of dichloromethane, tetrahydrofuran, and toluene; The solvent used in preparing the polyimide diamine monomer in step S3 is at least one of water, ethanol, and methanol.

[0012] Furthermore, the reaction temperature of step S1 is 20-25°C; the reaction temperature of step S2 is 15-25°C; and the reaction temperature of step S3 is 50-60°C.

[0013] Furthermore, 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 the intermediate II to Raney nickel is 1:(5-6), the molar ratio of the intermediate II to glacial acetic acid is 1:(5-6), the molar ratio of the intermediate II to pyridine is 1:(8-9), and the molar ratio of the intermediate II to sodium hypophosphite is 1:(10-12).

[0014] Furthermore, in step S1, after the reaction is completed, ethanol is added to quench the reaction, the solvent is removed, and the product is purified using a water beating system to obtain intermediate I.

[0015] Furthermore, in step S2, after the reaction is completed, the by-products 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.

[0016] Furthermore, in step S3, after the reaction is completed, the reaction system is extracted with an organic solvent, insoluble matter is filtered out, the organic phase is acid-washed and water-washed multiple times, the organic solvent is removed, the mixture is column-filtered, and recrystallized to obtain the polyimide diamine monomer.

[0017] The beneficial effects of the present invention are: A kind of efficient and cheap reduction system is used in the preparation method of the present invention, the combined action of Raney nickel, glacial acetic acid, pyridine, and sodium hypophosphite aqueous solution constitutes a reduction system, and the reduction system can slowly produce reducing hydrogen. Under the effect of reducing hydrogen inside the system, various nitrobenzenes and various nitroaromatic derivatives are selectively reduced. Other functional groups such as ester groups that are sensitive to catalytic hydrogenation reactions, double bonds, etc. will not be affected, so that a polyimide diamine monomer containing a double bond and an ester group structure with excellent comprehensive performance can be prepared. The reaction process is more controllable, and the preparation method is simple. Compared with the scheme in the CN116375591A patent, the method is mild and controllable, is conducive to amplification of production, and can be applied on a large scale. And the synthetic route of the present invention also has a good reference role in the synthesis of other amino compounds containing cinnamic acid structures.

[0018] The preparation method of the present invention has short reaction steps, high yield, high product purity, low cost, and is conducive to large-scale production. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 is the (3,5-dinitrophenyl) 3-phenyl-2-propenoic acid methyl ester in Example 1 1 H-NMR spectrum; Figure 2 for Figure 1 (3,5-dinitrophenyl) 3-phenyl-2-propenoic acid methyl ester with chemical shifts of 5.0-9.2 1 H-NMR spectrum; Figure 3is (3,5-diaminophenyl) 3-phenyl-2-methyl propenoate in Example 1 1 H-NMR spectrum; Figure 4 for Figure 2 (3,5-diaminophenyl) 3-phenyl-2-propenoic acid methyl ester with chemical shifts of 5.8-7.9 1 H-NMR spectrum; Figure 5 This is the HPLC-MS spectrum of (3,5-diaminophenyl)-3-phenyl-2-propenoic acid methyl ester in Example 1. DETAILED DESCRIPTION

[0020] To make the above-mentioned objects, features, and advantages of the present invention more readily apparent, specific embodiments of the present invention are described in detail below. The following description sets forth numerous specific details to facilitate a full understanding of the present invention. However, the present invention can be implemented in many other ways than those described herein, and those skilled in the art may make similar modifications without departing from the scope of the present invention. Therefore, the present invention is not limited to the specific embodiments disclosed below.

[0021] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as those commonly understood by those skilled in the art of the present invention. The terms used in the specification of the present invention herein are only for the purpose of describing specific embodiments and are not intended to limit the present invention.

[0022] A method for preparing a polyimide diamine monomer, the preparation method comprising: S1. Preparation of Intermediate I: Under the protection of inert gas, in a solvent, with the system temperature controlled, reactant I reacts with a reducing agent. After the reaction is completed, intermediate I is obtained through post-treatment; The structural formula of the reactant I is: ; S2. Preparation of Intermediate II: Under the protection of inert gas, in a solvent, in the presence of a catalyst and a dehydrating agent, the intermediate I reacts with the reactant II. After the reaction is completed, the intermediate II is obtained through post-treatment. The structural formula of the reactant II is: ; The structural formula of the intermediate II is: ; S3. Preparation of polyimide diamine monomer: Under the protection of inert gas, 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 by post-treatment; The structural formula of the polyimide diamine monomer is: ; Wherein, R1 is a single bond or an alkylene group consisting of 1 to 5 carbon atoms or any one of -O-, -CONH-, -NHCO-, -COO-, -OCO-, -NH-, and -CO-; R2 is ; R3 is any one of hydrogen, an alkyl group consisting of 1-5 carbon atoms or a polycyclic heterocycle, and the heteroatom on the heterocycle is a nitrogen atom or an oxygen atom; and any methylene group on R3 can be replaced by any group of -O-, -CONH-, -NHCO-, -COO-, -OCO-, -NH-, -CO-, and one or more hydrogen atoms in the alkyl group consisting of 1-5 carbon atoms or the polycyclic heterocycle can be replaced by a fluorine atom or an alkyl group consisting of 1-5 carbon atoms.

[0023] Specifically, R1 is any one of a single bond, -CH2-, -CH2CH2-, -CH2CH2CH2-, -CH2CH2CH2CH2-, -CH2CH2CH2CH2CH2-, -O-, -CONH-, -NHCO-, -COO-, -OCO-, -NH-, and -CO-; The R3 is any one of hydrogen, -CH3, -CH2CH3, -CH2CH2CH3, -CH2CH2CH2CH3, -CH2CH2CH2CH2CH3, -CF3 and a polycyclic heterocycle.

[0024] Specifically, the structural formula of the polyimide diamine monomer is selected from any one of the following structures: ; ; ; ; ; ; ; .

[0025] Specifically, the reducing agent used in the preparation of intermediate I is borane tetrahydrofuran; 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.

[0026] More specifically, the borane used in the embodiment of the present invention is a complex of diborane and tetrahydrofuran, and its chemical formula is BH3·THF.

[0027] Specifically, the solvent used in preparing the intermediate I in step S1 is at least one of tetrahydrofuran and dichloromethane; The solvent used in the preparation of intermediate II in step S2 is at least one of dichloromethane, tetrahydrofuran, and toluene; The solvent used in preparing the polyimide diamine monomer in step S3 is at least one of water, ethanol, and methanol.

[0028] Specifically, the reaction temperature of step S1 is 20-25°C; the reaction temperature of step S2 is 15-25°C; and the reaction temperature of step S3 is 50-60°C.

[0029] Specifically, 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 the intermediate II to Raney nickel is 1:(5-6), the molar ratio of the intermediate II to glacial acetic acid is 1:(5-6), the molar ratio of the intermediate II to pyridine is 1:(8-9), and the molar ratio of the intermediate II to sodium hypophosphite is 1:(10-12).

[0030] Specifically, in step S1, after the reaction is completed, ethanol is added to quench the reaction, the solvent is removed, and the intermediate I is obtained by refining using a water beating system.

[0031] Specifically, in step S2, after the reaction is completed, the by-products 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.

[0032] Specifically, in step S3, after the reaction is completed, the reaction system is extracted with an organic solvent, and the insoluble matter is filtered out. The organic phase is washed with acid and water multiple times, and then the organic solvent is removed. The mixture is mixed, passed through a column, and recrystallized to obtain the polyimide diamine monomer.

[0033] Example 1 The preparation of methyl (3,5-diaminophenyl) 3-phenyl-2-propenoate comprises the following steps: ; (1) Preparation of 3,5-dinitrobenzyl alcohol: Under nitrogen protection, add 42.4 g (0.2 mol) of 3,5-dinitrobenzoic acid and 172.8 g of tetrahydrofuran into a clean and dry three-necked flask, and stir mechanically until the solid in the system is completely dissolved and the system is light brown and transparent.

[0034] Under nitrogen protection, the temperature in the system was controlled at 20-25°C, and 258 g (actually containing 0.3 mol of borane) of borane tetrahydrofuran solution (concentration of 10%) was gradually added dropwise to the three-necked flask. After the addition was completed, the mixture was kept at 20-25°C for 3 hours. After the reaction was completed, a reaction solution was obtained and quenched.

[0035] Under nitrogen protection, 200.0 g of anhydrous ethanol was added to a clean and dry three-necked flask, and the anhydrous ethanol was cooled to <-5°C in advance. The reaction solution was added dropwise to the anhydrous ethanol in the three-necked flask, and the temperature in the three-necked flask was controlled to -5~0°C for quenching. After quenching, stirring was carried out for 30 minutes. 202.0 g of softened water was added and stirring was continued for 30 minutes to remove most of the tetrahydrofuran and ethanol in the system. The system was heated to 50~55°C and slurried with water for 1 hour. Then the temperature was cooled, filtered and dried to obtain 3,5-dinitrobenzyl alcohol with a purity of 98.0% and a yield of 96%.

[0036] (2) Preparation of (3,5-dinitrophenyl) 3-phenyl-2-propenoic acid methyl ester: Under nitrogen protection, add 53.46g (0.27mol) 3,5-dinitrobenzyl alcohol, 3.66g (0.03mol) DMAP, 41.88g (0.283mol) cinnamic acid, and 500.0g dichloromethane into a clean and dry three-necked flask. Control the internal temperature at 15-25℃ and stir until the system is dissolved.

[0037] Under nitrogen protection, control the internal temperature at 15-25°C and dropwise add a solution prepared by 58.6g (0.284mol) DCC and 116.7g dichloromethane. After the addition is completed, keep warm for 2 hours, filter, and rinse with 300.0g dichloromethane. Collect the filtrate and the eluent and pass it through a 60.0g neutral alumina column. After passing through the column, rinse the column with 500.0g dichloromethane. Combine the column liquid and the eluent to remove the solvent. Prepare the solution with 708.0g tetrahydrofuran, pass it through a 60.0g silica gel column, rinse the column with tetrahydrofuran, combine the column liquid and the eluent, and remove the solvent. The crude product was recrystallized from tetrahydrofuran to obtain (3,5-dinitrophenyl) 3-phenyl-2-propenoic acid methyl ester with a purity of 99.0% and a yield of 90%. Test 1 H-NMR, see Figure 1-Figure 2 .

[0038] (3) Preparation of (3,5-diaminophenyl) 3-phenyl-2-propenoic acid methyl ester: Under nitrogen protection, add 30g (0.091mol) (3,5-dinitrophenyl) 3-phenyl-2-propenoic acid methyl ester, 29.4g (0.501mol) Raney nickel, 30.1g (0.501mol) glacial acetic acid, 61.2g (0.774mol) pyridine, and 60.0g water into a clean and dry three-necked flask, stir, and heat the system to 50℃.

[0039] Under nitrogen protection, 88.1 g (1.0 mol) of sodium hypophosphite (33.33% aqueous solution) was added dropwise. The addition process was significantly exothermic and gas overflowed. The temperature was controlled at 50-60°C and the reaction was kept warm for 1 hour. After all the raw materials and intermediates were converted into products (the remaining raw materials and intermediates were tracked by TLC spot plate during the reaction, and the developing solvent was ethyl acetate), the reaction was terminated and the temperature was lowered to 20-30°C.

[0040] Under nitrogen protection, 300g of dichloromethane was added to the three-necked reaction flask and stirred thoroughly for extraction. The insoluble matter in the system was filtered out, the stratification was allowed to stand, the aqueous phase was separated, and the organic phase was washed once with 5% hydrochloric acid, and then washed 3 times with water until the organic phase was neutral. The solvent was removed and then a mixture of tetrahydrofuran and n-hexane was used to prepare the solution and pass it through a 36.6g silica gel column. The column was eluted with a mixture of tetrahydrofuran and n-hexane. The column liquid was combined with the eluent to dry it, and the target product (3,5-diaminophenyl) 3-phenyl-2-propenoic acid methyl ester was obtained after recrystallization using a toluene ethanol system with a purity of 99.0% and a yield of 92%. 1 H-NMR and HPLC-MS, see Figure 3-Figure 5 .

[0041] Example 2 The preparation of methyl (3,5-diaminophenyl) 3-phenyl-2-propenoate comprises the following steps: (1) Preparation of 3,5-dinitrobenzyl alcohol: Under nitrogen protection, add 42.4 g (0.2 mol) of 3,5-dinitrobenzoic acid and 173 g of tetrahydrofuran into a clean and dry three-necked flask, and stir mechanically until the solid in the system is completely dissolved and the system is light brown and transparent.

[0042] Under nitrogen protection, the temperature in the system was controlled at 20-25°C, and 206 g (actually containing 0.24 mol of borane) of borane tetrahydrofuran solution (concentration of 10%) was gradually added dropwise to the three-necked flask. After the addition was completed, the mixture was kept at 20-25°C for 3 hours. After the reaction was completed, a reaction solution was obtained and quenched.

[0043] Under nitrogen protection, 200.0 g of anhydrous ethanol was added to a clean and dry three-necked flask, and the anhydrous ethanol was cooled to <-5°C in advance. The reaction solution was added dropwise to the anhydrous ethanol in the three-necked flask, and the temperature in the three-necked flask was controlled to -5~0°C for quenching. After quenching, stirring was carried out for 30 minutes. 202.0 g of softened water was added and stirring was continued for 30 minutes to remove most of the tetrahydrofuran and ethanol in the system. The system was heated to 50~55°C and slurried with water for 1 hour. Then the temperature was cooled, filtered and dried to obtain 3,5-dinitrobenzyl alcohol with a purity of 97.0% and a yield of 95.6%.

[0044] (2) Preparation of (3,5-dinitrophenyl) 3-phenyl-2-propenoic acid methyl ester: Under nitrogen protection, add 53.46g (0.27mol) 3,5-dinitrobenzyl alcohol, 4.94g (0.0405mol) DMAP, 43.96g (0.297mol) cinnamic acid, and 500.0g dichloromethane into a clean and dry three-necked flask. Control the internal temperature at 15-25℃ and stir until the system is dissolved.

[0045] Under nitrogen, a solution prepared by adding 61.28 g (0.297 mol) of DCC and 116.7 g of dichloromethane was added dropwise at an internal temperature of 15-25°C. The mixture was allowed to react for 2 hours, filtered, and rinsed with 300 g of dichloromethane. The filtrate and the rinse were collected and passed through a 60.0 g neutral alumina column. The column was then rinsed with 500 g of dichloromethane. The filtrate and the rinse were combined and the solvent was removed. The mixture was then passed through a 60.0 g silica gel column with 708.0 g of tetrahydrofuran, rinsed with tetrahydrofuran, and the filtrate and rinse were combined and the solvent was removed. The crude product was recrystallized from tetrahydrofuran to obtain (3,5-dinitrophenyl)-3-phenyl-2-propenoic acid methyl ester with a purity of 98.0% and a yield of 89%.

[0046] (3) Preparation of (3,5-diaminophenyl) 3-phenyl-2-propenoic acid methyl ester: Under nitrogen protection, 30 g (0.091 mol) of (3,5-dinitrophenyl) 3-phenyl-2-propenoic acid methyl ester, 29.4 g (0.501 mol) of Raney nickel, 30.1 g (0.501 mol) of glacial acetic acid, 61.2 g (0.774 mol) of pyridine, and 60.0 g of ethanol were added to a clean and dry three-necked flask, stirred, and the system was heated to 50°C.

[0047] Under nitrogen protection, 88.1 g (1.0 mol) of sodium hypophosphite (33.33% aqueous solution) was added dropwise. The addition process was significantly exothermic and gas overflowed. The temperature was controlled at 50-60°C and the reaction was kept warm for 1 hour. After all the raw materials and intermediates were converted into products (the remaining raw materials and intermediates were tracked by TLC spot plate during the reaction, and the developing solvent was ethyl acetate), the reaction was terminated and the temperature was lowered to 20-30°C.

[0048] Under nitrogen protection, 300 g of dichloromethane was added to a three-necked reaction flask and stirred thoroughly for extraction. The insoluble matter in the system was filtered out, the system was allowed to stand and stratify, 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 then passed through a 36.6 g silica gel column with a mixture of tetrahydrofuran and n-hexane in a ratio of 2:1. The column was eluted with a mixture of tetrahydrofuran and n-hexane, the column liquid was combined with the eluent, and the eluent was dried. After recrystallization using a toluene ethanol system, the target product (3,5-diaminophenyl) 3-phenyl-2-propenoic acid methyl ester was obtained with a purity of 99.0% and a yield of 89.6%.

[0049] Example 3 The preparation of methyl (3,5-diaminophenyl) 3-phenyl-2-propenoate comprises the following steps: (1) Preparation of 3,5-dinitrobenzyl alcohol: Under nitrogen protection, add 42.4 g (0.2 mol) of 3,5-dinitrobenzoic acid and 173 g of tetrahydrofuran into a clean and dry three-necked flask, and stir mechanically until the solid in the system is completely dissolved and the system is light brown and transparent.

[0050] Under nitrogen protection, the temperature in the system was controlled at 20-22°C, and 275 g (actually containing 0.32 mol of borane) of borane tetrahydrofuran solution (concentration 10%) was gradually added dropwise to the three-necked flask. After the addition, the mixture was kept at 20-22°C for 3 hours. After the reaction was completed, a reaction solution was obtained and quenched.

[0051] Under nitrogen protection, 200.0 g of anhydrous ethanol was added to a clean and dry three-necked flask, and the anhydrous ethanol was cooled to <-5°C in advance. The reaction solution was added dropwise to the anhydrous ethanol in the three-necked flask, and the temperature in the three-necked flask was controlled to -5~0°C for quenching. After quenching, stirring was carried out for 30 minutes. 202.0 g of softened water was added and stirring was continued for 30 minutes to remove most of the tetrahydrofuran and ethanol in the system. The system was heated to 50~55°C and slurried with water for 1 hour. Then the temperature was cooled, filtered and dried to obtain 3,5-dinitrobenzyl alcohol with a purity of 97.0% and a yield of 96.0%.

[0052] (2) Preparation of (3,5-dinitrophenyl) 3-phenyl-2-propenoic acid methyl ester: Under nitrogen protection, add 53.46g (0.27mol) 3,5-dinitrobenzyl alcohol, 3.29g (0.027mol) DMAP, 39.96g (0.27mol) cinnamic acid, and 500.0g dichloromethane into a clean and dry three-necked flask. Control the internal temperature at 15-20℃ and stir until the system is dissolved.

[0053] Under nitrogen, a solution prepared by adding 55.71 g (0.27 mol) of DCC and 116.7 g of dichloromethane was added dropwise at an internal temperature of 15-20°C. The mixture was allowed to react for 2 hours, filtered, and rinsed with 300 g of dichloromethane. The filtrate and rinse were collected and passed through a 60.0 g neutral alumina column. The column was then rinsed with 500 g of dichloromethane. The filtrate and rinse were combined and the solvent was removed. The mixture was then passed through a 60.0 g silica gel column with 708.0 g of tetrahydrofuran, rinsed with tetrahydrofuran, and the filtrate and rinse were combined and the solvent was removed. The crude product was recrystallized from tetrahydrofuran to obtain (3,5-dinitrophenyl)-3-phenyl-2-propenoic acid methyl ester with a purity of 98% and a yield of 88%.

[0054] (3) Preparation of (3,5-diaminophenyl) 3-phenyl-2-propenoic acid methyl ester: Under nitrogen protection, 30 g (0.091 mol) of (3,5-dinitrophenyl) 3-phenyl-2-propenoic acid methyl ester, 29.4 g (0.501 mol) of Raney nickel, 30.1 g (0.501 mol) of glacial acetic acid, 61.2 g (0.774 mol) of pyridine, and 60.0 g of methanol were added to a clean and dry three-necked flask, stirred, and the system was heated to 50 °C.

[0055] Under nitrogen protection, 88.1 g (1.0 mol) of sodium hypophosphite (33.33% aqueous solution) was added dropwise. The addition process was significantly exothermic and gas overflowed. The temperature was controlled at 50-60°C and the reaction was kept warm for 1 hour. After all the raw materials and intermediates were converted into products (the remaining raw materials and intermediates were tracked by TLC spot plate during the reaction, and the developing solvent was ethyl acetate), the reaction was terminated and the temperature was lowered to 20-30°C.

[0056] Under nitrogen protection, 300 g of dichloromethane was added to a three-necked reaction flask and stirred thoroughly for extraction. The insoluble matter in the system was filtered out, the system was allowed to stand and stratify, 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 then passed through a 36.6 g silica gel column with a mixture of tetrahydrofuran and n-hexane in a ratio of 2:1. The column was eluted with a mixture of tetrahydrofuran and n-hexane, the column liquid was combined with the eluent, and the eluent was dried. After recrystallization using a toluene ethanol system, the target product (3,5-diaminophenyl) 3-phenyl-2-propenoic acid methyl ester was obtained with a purity of 99.0% and a yield of 90%.

[0057] Example 4 The preparation of methyl (3,5-diaminophenyl) 3-phenyl-2-propenoate comprises the following steps: (1) Preparation of 3,5-dinitrobenzyl alcohol: Under nitrogen protection, add 42.4 g (0.2 mol) of 3,5-dinitrobenzoic acid and 172.8 g of dichloromethane into a clean and dry three-necked flask and stir mechanically until the solid in the system is completely dissolved and the system is light brown and transparent.

[0058] Under nitrogen protection, the temperature in the system was controlled at 20-25°C, and 260 g (actually containing 0.32 mol of borane) of borane tetrahydrofuran solution was gradually added dropwise to the three-necked flask. After the addition was completed, the temperature was kept at 20-25°C for 3 hours. After the reaction was completed, a reaction solution was obtained and quenched.

[0059] Under nitrogen protection, 200.0 g of anhydrous ethanol was added to a clean and dry three-necked flask, and the anhydrous ethanol was cooled to <-5°C in advance. The reaction solution was added dropwise to the anhydrous ethanol in the three-necked flask, and the temperature in the three-necked flask was controlled to -5~0°C for quenching. After quenching, stirring was carried out for 30 minutes. 202.0 g of softened water was added and stirring was continued for 30 minutes to remove most of the dichloromethane and ethanol in the system. The system was heated to 50~55°C and slurried with water for 1 hour. Then the temperature was cooled, filtered and dried to obtain 3,5-dinitrobenzyl alcohol with a purity of 95.0% and a yield of 93.5%.

[0060] (2) Preparation of (3,5-dinitrophenyl) 3-phenyl-2-propenoic acid methyl ester: Under nitrogen protection, add 53.46g (0.27mol) 3,5-dinitrobenzyl alcohol, 74.5g (0.284mol) triphenylphosphine, 41.88g (0.283mol) cinnamic acid, and 500.0g toluene into a clean and dry three-necked flask. Control the internal temperature at 15-20℃ and stir until the system is uniform.

[0061] Under nitrogen, a solution prepared by adding 57.4 g (0.284 mol) of DIAD and 116.7 g of toluene was added dropwise at an internal temperature of 15-20°C. The mixture was allowed to react for 2 hours, filtered, and rinsed with 300 g of toluene. The filtrate and the rinse were collected and passed through a 60.0 g silica gel column. The column was then rinsed with 500 g of toluene. The filtrate and the rinse were combined and the solvent was removed. The solution was then passed through a 60.0 g silica gel column, rinsed with tetrahydrofuran, and the filtrate and rinse were combined and the solvent was removed. The crude product was recrystallized from tetrahydrofuran to obtain (3,5-dinitrophenyl)-3-phenyl-2-propenoic acid methyl ester with a purity of 96.0% and a yield of 89.5%.

[0062] (3) Preparation of (3,5-diaminophenyl) 3-phenyl-2-propenoic acid methyl ester: Under nitrogen protection, 30 g (0.091 mol) of (3,5-dinitrophenyl) 3-phenyl-2-propenoic acid methyl ester, 29.4 g (0.501 mol) of Raney nickel, 30.1 g (0.501 mol) of glacial acetic acid, 30.6 g (0.387 mol) of pyridine, and 60.0 g of water were added to a clean and dry three-necked flask, stirred, and the system was heated to 50°C.

[0063] Under nitrogen protection, 88.1 g (1.0 mol) of sodium hypophosphite (33.33% aqueous solution) was added dropwise. The addition process was significantly exothermic and gas overflowed. The temperature was controlled at 50-60°C and the reaction was kept warm for 2 hours. After all the raw materials and intermediates were converted into products (the remaining raw materials and intermediates were tracked by TLC spot plate during the reaction, and the developing solvent was ethyl acetate), the reaction was terminated and the temperature was lowered to 20-30°C.

[0064] Under nitrogen protection, 300 g of dichloromethane was added to a three-necked reaction flask and stirred thoroughly for extraction. The insoluble matter in the system was filtered out, the system was allowed to stand and stratify, 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 then passed through a 36.6 g silica gel column with a mixture of tetrahydrofuran and n-hexane in a ratio of 2:1. The column was eluted with a mixture of tetrahydrofuran and n-hexane, the column liquid was combined with the eluent, and the eluent was dried. After recrystallization using a toluene ethanol system, the target product (3,5-diaminophenyl) 3-phenyl-2-propenoic acid methyl ester was obtained with a purity of 99.0% and a yield of 89%.

[0065] Example 5 The preparation of ethyl (3,5-diaminophenyl) 3-phenyl-2-acrylate comprises the following steps: (1) Preparation of 3,5-dinitrophenylethanol: Under nitrogen protection, add 45.2 g (0.2 mol) of 3,5-dinitrophenylacetic acid and 173 g of tetrahydrofuran into a clean and dry three-necked flask and stir mechanically until the solid in the system is completely dissolved and the system is light brown and transparent.

[0066] Under nitrogen protection, the temperature in the system was controlled at 20-25°C, and 206 g (actually containing 0.24 mol of borane) of borane tetrahydrofuran solution (concentration of 10%) was gradually added dropwise to the three-necked flask. After the addition was completed, the mixture was kept at 20-25°C for 3 hours. After the reaction was completed, a reaction solution was obtained and quenched.

[0067] Under nitrogen protection, 200.0 g of anhydrous ethanol was added to a clean and dry three-necked flask, and the anhydrous ethanol was cooled to <-5°C in advance. The reaction solution was added dropwise to the anhydrous ethanol in the three-necked flask, and the temperature in the three-necked flask was controlled to -5~0°C for quenching. After quenching, stirring was carried out for 30 minutes. 202.0 g of softened water was added and stirring was continued for 30 minutes to remove most of the tetrahydrofuran and ethanol in the system. The system was heated to 50~55°C and slurried with water for 1 hour. Then the temperature was cooled, filtered and dried to obtain 3,5-dinitrophenylethanol with a purity of 97.5% and a yield of 95.0%.

[0068] (2) Preparation of (3,5-dinitrophenyl) 3-phenyl-2-propenoic acid ethyl ester: Under nitrogen protection, add 57.24g (0.27mol) 3,5-dinitrophenylethanol, 4.94g (0.0405mol) DMAP, 43.96g (0.297mol) cinnamic acid, and 500.0g dichloromethane into a clean and dry three-necked flask. Control the internal temperature at 15-25℃ and stir until the system is dissolved.

[0069] Under nitrogen, a solution prepared by adding 61.28 g (0.297 mol) of DCC and 116.7 g of dichloromethane was added dropwise at an internal temperature of 15-25°C. The mixture was allowed to react for 2 hours, filtered, and rinsed with 300 g of dichloromethane. The filtrate and rinse were collected and passed through a 60.0 g neutral alumina column. The column was then rinsed with 500 g of dichloromethane. The filtrate and rinse were combined and the solvent was removed. The mixture was then passed through a 60.0 g silica gel column with 708.0 g of tetrahydrofuran, rinsed with tetrahydrofuran, and the filtrate and rinse were combined and the solvent was removed. The crude product was recrystallized from tetrahydrofuran to obtain (3,5-dinitrophenyl)-3-phenyl-2-propenoic acid ethyl ester with a purity of 98.3% and a yield of 88.6%.

[0070] (3) Preparation of (3,5-diaminophenyl) 3-phenyl-2-propenoic acid ethyl ester: Under nitrogen protection, 31.27 g (0.091 mol) of (3,5-dinitrophenyl) 3-phenyl-2-propenoic acid ethyl ester, 29.4 g (0.501 mol) of Raney nickel, 30.1 g (0.501 mol) of glacial acetic acid, 61.2 g (0.774 mol) of pyridine, and 60.0 g of ethanol were added to a clean and dry three-necked flask, stirred, and the system was heated to 50°C.

[0071] Under nitrogen protection, 88.1 g (1.0 mol) of sodium hypophosphite (33.33% aqueous solution) was added dropwise. The addition process was significantly exothermic and gas overflowed. The temperature was controlled at 50-60°C and the reaction was kept warm for 1 hour. After all the raw materials and intermediates were converted into products (the remaining raw materials and intermediates were tracked by TLC spot plate during the reaction, and the developing solvent was ethyl acetate), the reaction was terminated and the temperature was lowered to 20-30°C.

[0072] Under nitrogen protection, 300 g of dichloromethane was added to a three-necked reaction flask and stirred thoroughly for extraction. The insoluble matter in the system was filtered out, the system was allowed to stand and stratify, 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 then passed through a 36.6 g silica gel column with a mixture of tetrahydrofuran and n-hexane in a ratio of 2:1. The column was eluted with a mixture of tetrahydrofuran and n-hexane, the column liquid was combined with the eluent, and the eluent was dried. After recrystallization using a toluene ethanol system, the target product (3,5-diaminophenyl) 3-phenyl-2-propenoic acid ethyl ester was obtained with a purity of 99.1% and a yield of 89.7%.

[0073] Comparative Example 1 (3,5-Diaminophenyl) 3-phenyl-2-propenoic acid methyl ester was prepared by the same method as in Example 1, except that pyridine was not added in step (3). Other conditions were exactly the same.

[0074] In this comparative example 1, the yield of the target product (3,5-diaminophenyl) 3-phenyl-2-propenoic acid methyl ester was only 10%, and most of the product was hydrolyzed.

[0075] Comparative Example 2 (3,5-diaminophenyl) 3-phenyl-2-propenoic acid methyl ester was prepared by the same method as in Example 1, except that no sodium hypophosphite aqueous solution was added in step (3). Other conditions were exactly the same.

[0076] In this comparative example 2, the target product (3,5-diaminophenyl) 3-phenyl-2-propenoic acid methyl ester was almost undetectable, and the yield was almost 0.

[0077] Comparative Example 3 (3,5-diaminophenyl)3-phenyl-2-propenoic acid methyl ester was prepared by the same method as in Example 1, except that glacial acetic acid was not added in step (3). The target product (3,5-diaminophenyl)3-phenyl-2-propenoic acid methyl ester could be detected, but the reaction rate was very slow, and there was still residual raw material after keeping the temperature for 24 hours. The yield of the target product was only 20%.

[0078] Comparative Example 4 (3,5-diaminophenyl) 3-phenyl-2-propenoic acid methyl ester was prepared by the same method as in Example 1, except that Raney nickel was not added in step (3). The target product (3,5-diaminophenyl) 3-phenyl-2-propenoic acid methyl ester was completely undetectable, and the yield of the target product was 0%.

[0079] Comparative Example 5 (3,5-diaminophenyl) 3-phenyl-2-propenoic acid methyl ester was prepared by the same method as in Example 1, except that in step (3), Raney nickel and hydrogen were directly used for pressure reaction, and the yield of the target product was 0%.

[0080] It can be seen from the experimental results of Comparative Examples 1, 2, 3, 4 and Example 1 that in the preparation method of the present invention, by using a reduction system of Raney nickel, glacial acetic acid, pyridine and sodium hypophosphite aqueous solution, good selective reduction can be achieved to obtain the desired polyimide diamine monomer containing double bonds and ester groups. Raney nickel, glacial acetic acid, pyridine and sodium hypophosphite are four indispensable substances. Only when these substances are used in combination to form a reduction system can a good reduction effect be achieved. The reduction system will slowly generate reducing hydrogen. Under the action of the reducing hydrogen inside the system, various nitrobenzenes and various nitroaromatic hydrocarbon derivatives are selectively reduced, and other functional groups sensitive to catalytic hydrogenation reactions, such as ester groups and double bonds, will not be affected.

[0081] Furthermore, a comparison of the experimental results of Comparative Example 5 and Example 1 shows that the yield of the polyimide diamine monomer containing double bonds and ester groups (i.e., (3,5-diaminophenyl)-3-phenyl-2-propenoic acid methyl ester) is significantly reduced, or even no product is obtained, when a conventional hydrogenation reduction system is used. This is because conventional reducing agents reduce the double bonds simultaneously with the nitro group, resulting in poor reduction selectivity and ultimately a significantly reduced yield of the target product, or even no product is obtained. However, the reduction system of the present invention achieves excellent reduction selectivity, ultimately yielding a high-yield, high-purity polyimide diamine monomer containing double bonds and ester groups.

[0082] The technical features of the above-mentioned embodiments can be combined arbitrarily. In order to make the description concise, not all possible combinations of the technical features in the above-mentioned 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.

[0083] The above-described embodiments merely illustrate several implementations of the present invention, and while their descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the patent. It should be noted that a person skilled in the art would be able to make numerous variations and improvements without departing from the spirit of the present invention, all of which fall within the scope of protection of the present invention. Therefore, the scope of protection of the patent for this invention shall be determined by the appended claims.

Claims

1. A method for preparing a polyimide diamine monomer, comprising: S1, reacting a reactant I with a reducing agent to obtain an intermediate I; the reactant I has the structural formula: ; The structural formula of the intermediate I is: ; S2, intermediate I and reactant II react to obtain intermediate II; the structural formula of the reactant II is: ; The structural formula of intermediate II is: ; S3, using intermediate II to prepare a polyimide diamine monomer, characterized in that, Under inert gas protection, intermediate II, Raney nickel, glacial acetic acid, pyridine and sodium hypophosphite aqueous solution are added to a solvent for reaction, and then post-treated to obtain a polyimide diamine monomer; The polyimide diamine monomer is: ; Wherein, R1 is a single bond or an alkylene group consisting of 1 to 5 carbon atoms or any one of -O-, -CONH-, -NHCO-, -COO-, -OCO-, -NH-, and -CO-; R2 is ; R3 is any one of hydrogen, an alkyl group consisting of 1-5 carbon atoms or a polycyclic heterocycle, and the heteroatom on the heterocycle is a nitrogen atom or an oxygen atom; and any methylene group on R3 can be replaced by any group of -O-, -CONH-, -NHCO-, -COO-, -OCO-, -NH-, -CO-, and one or more hydrogen atoms in the alkyl group consisting of 1-5 carbon atoms or the polycyclic heterocycle can be replaced by a fluorine atom or an alkyl group consisting of 1-5 carbon atoms.

2. The method for preparing a polyimide diamine monomer according to claim 1, wherein: R1 is any one of a single bond, -CH2-, -CH2CH2-, -CH2CH2CH2-, -CH2CH2CH2CH2-, -CH2CH2CH2CH2CH2-, -O-, -CONH-, -NHCO-, -COO-, -OCO-, -NH-, and -CO-; The R3 is any one of hydrogen, -CH3, -CH2CH3, -CH2CH2CH3, -CH2CH2CH2CH3, -CH2CH2CH2CH2CH3, -CF3 and a polycyclic heterocycle.

3. The method for preparing a polyimide diamine monomer according to claim 1, wherein: The structural formula of the polyimide diamine monomer is selected from any one of the following structures: ； ； ； ； ； ； ； 。 4. The method for preparing a polyimide diamine monomer according to claim 1, wherein: The reducing agent used in the preparation of intermediate I is borane tetrahydrofuran; the catalyst used in the preparation of intermediate II is DMAP or triphenylphosphine; the dehydrating agent used in the preparation of intermediate II is DCC or DIAD.

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

6. The method for preparing a polyimide diamine monomer according to claim 1, wherein: The reaction temperature of step S1 is 20-25°C; the reaction temperature of step S2 is 15-25°C; and the reaction temperature of step S3 is 50-60°C.

7. The method for preparing a polyimide diamine monomer according to claim 1, wherein: 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 the intermediate II to Raney nickel is 1:(5-6), the molar ratio of the intermediate II to glacial acetic acid is 1:(5-6), the molar ratio of the intermediate II to pyridine is 1:(8-9), and the molar ratio of the intermediate II to sodium hypophosphite is 1:(10-12).

8. The method for preparing a polyimide diamine monomer according to claim 1, wherein: In step S1, after the reaction is completed, ethanol is added to quench the reaction, the solvent is removed, and the product is purified using a water beating system to obtain intermediate I.

9. The method for preparing a polyimide diamine monomer according to claim 1, wherein: In step S2, after the reaction is completed, the by-products 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.

10. The method for preparing a polyimide diamine monomer according to claim 1, wherein: In step S3, after the reaction is completed, the reaction system is extracted with an organic solvent, and the insoluble matter is filtered out. The organic phase is washed with acid and water for multiple times, and then the organic solvent is removed. The mixture is then passed through a column and recrystallized to obtain the polyimide diamine monomer.

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