A method for preparing bis(4-aminophenyl)terephthalate

Abstract

The invention provides a preparation method of bis(4-aminophenyl)terephthalate, comprising the following steps: (1) under protective gas, terephthalic acid, N-Boc-4-aminophenol, condensing agent, DMAP and organic solvent A are mixed uniformly, heated and stirred for reaction, after completion of the reaction, filtered, concentrated to dryness, added methanol, stirred, filtered, methanol rinsed, dried, and a compound shown in formula I is obtained; (2) under protective gas, the compound shown in formula I obtained in step (1) is mixed uniformly with organic solvent B, an acid catalyst is added, stirred and heated for reaction, after completion of the reaction, cooled and stirred, filtered, methanol rinsed, dried, and a compound shown in formula II is obtained. Beneficial effects of the invention: raw material terephthalic acid is cheap, reaction conditions are simple, reaction steps are short, and reaction yield is high. Therefore, the preparation method of the present invention is novel, raw materials are cheap and easily available, reaction conditions are easy to implement, and overall preparation cost is low and yield is high.

Description

Technical Field

[0001] The invention belongs to the technical field of organic chemical synthesis, and in particular relates to a method for preparing bis(4-aminophenyl)terephthalate. Background Art

[0002] Aromatic polyimide (API) is one of the thermoplastic engineering plastics with the best heat resistance. It has been widely used in aviation, aerospace, electromechanical, electronics, ships, automobiles, precision machinery and other fields. Aromatic polyimide is mainly formed by the gradual polymerization of aromatic diamines and dianhydrides. Its structure has a very stable aromatic heterocyclic structure, which makes it have excellent properties that other polymer materials cannot match. Polyimide has a wide range of practical applications, including plastics, films, adhesives, composite materials, fibers, foams, liquid crystal orientation agents, separation membranes, photoresists, etc. The polyimide film material with low hygroscopicity, low thermal expansion coefficient (CTE value) and high permeability obtained by the polycondensation of bis(4-aminophenyl) terephthalate (BAPT) and aromatic dianhydride has broad application prospects in the display field.

[0003] The structural formula of bis(4-aminophenyl)terephthalate is as follows:

[0004]

[0005] At present, the method for synthesizing bis(4-aminophenyl)terephthalate is mainly to react terephthaloyl chloride and p-nitrophenol as raw materials to generate dinitrophenyl ester, and then hydrogenate and reduce the nitro group to obtain bis(4-aminophenyl)terephthalate (Korean patent, KR201896151 A). The solubility of the dinitrophenyl ester intermediate in this method is extremely poor, and the chemical reduction method has a very poor effect. Only the hydrogenation reduction method can be used and only highly polar organic solvents such as DMF and DMSO can be used. The hydrogenation reduction method is prone to incomplete reaction intermediates and impurities, which are difficult to purify. Summary of the invention

[0006] In view of this, the present invention aims to provide a method for preparing bis(4-aminophenyl)terephthalate to solve the problems mentioned in the above background technology.

[0007] To achieve the above object, the technical solution of the present invention is achieved as follows:

[0008] A method for preparing bis(4-aminophenyl)terephthalate comprises the following steps:

[0009] (1) Under protective gas, terephthalic acid, oxycarbonyl-4-hydroxyaniline (N-Boc-4-aminophenol), a condensing agent, 4-dimethylaminopyridine (DMAP) and an organic solvent A are mixed uniformly, heated and stirred to react, and after the reaction is completed, filtered, concentrated to dryness, methanol is added, stirred, filtered, rinsed with methanol, and dried to obtain a compound represented by formula I;

[0010] (2) under protective gas, the compound of formula I obtained in step (1) is mixed evenly with an organic solvent B, an acid catalyst is added, and the mixture is stirred and heated to cause a de-tert-butyloxycarbonyl (Boc) reaction. After the reaction is completed, the mixture is cooled and stirred, filtered, rinsed with methanol, and dried to obtain a compound of formula II;

[0011] The synthetic route is as follows:

[0012]

[0013] Furthermore, in the step (1), under protective gas, terephthalic acid, N-Boc-4-aminophenol, a condensing agent and 4-dimethylaminopyridine (DMAP) are added to an organic solvent A, and the system is heated to 40°C and stirred for 1 hour. After the reaction is completed by HPLC, the reaction is filtered, the filtrate is concentrated to dryness, methanol is added for crystallization, filtered, rinsed, and dried to obtain the compound bis[4-(tert-butyloxycarbonylamino)phenyl]terephthalate shown in formula I. By controlling the reaction temperature and the amount of N-Boc-4-aminophenol and the condensing agent, incomplete reaction of the raw material terephthalic acid is avoided to the greatest extent.

[0014] Furthermore, in step (1), the molar ratio of terephthalic acid, N-Boc-4-aminophenol and condensing agent is: 1.0:(2.2-5.0):(2.2-5.0). Within this range, the reaction of terephthalic acid is most complete and the yield is the highest.

[0015] Furthermore, in the step (1), the organic solvent A is any one of dichloromethane, chloroform, dichloroethane, tetrahydrofuran, acetonitrile, N,N-dimethylformamide (DMF), N-methylpyrrolidone (NMP), and dimethyl sulfoxide (DMSO).

[0016] Furthermore, in the step (1), the condensing agent is any one of N,N'-dicyclohexylcarbodiimide (DCC), N,N'-diisopropylcarbodiimide (DIC), N,N'-carbonyldiimidazole (CDI), and 1-(3-dimethylaminopropyl)-3-ethylcarbodiimide hydrochloride (EDCI).

[0017] Furthermore, in the step (2), the reaction temperature is 50-70°C.

[0018] Furthermore, in the step (2), an acid catalyst is added to a mixed solution of bis[4-(tert-butyloxycarbonylamino)phenyl]terephthalate and an organic solvent B, and the system temperature is raised to 60° C. and stirred for 6 hours. After the reaction is completed by HPLC detection, the temperature is lowered to 10° C., stirred for 1 hour, filtered, rinsed, and dried to obtain bis(4-aminophenyl)terephthalate shown in formula II. By controlling the reaction temperature, incomplete de-Boc reaction is avoided to the greatest extent.

[0019] Furthermore, in the step (2), the molar ratio of bis[4-(tert-butoxycarbonylamino)phenyl]terephthalate to the acid is 1.0:(0.1-1.0).

[0020] Furthermore, in step (2), the organic solvent B is any one of methanol, ethanol, isopropanol, tetrahydrofuran, acetonitrile, and 1,4-dioxane.

[0021] Furthermore, in step (2), the acid catalyst is any one of hydrochloric acid, sulfuric acid, phosphoric acid, trifluoroacetic acid and trifluoromethanesulfonic acid.

[0022] Furthermore, the protective gas is an inert gas, preferably nitrogen.

[0023] Compared with the prior art, the method for preparing bis(4-aminophenyl)terephthalate of the present invention has the following advantages:

[0024] The method for preparing bis(4-aminophenyl)terephthalate of the present invention uses terephthalic acid as a main raw material, constructs the main carbon skeleton of bis(4-aminophenyl)terephthalate through a dehydration esterification reaction with N-Boc-4-aminophenol, and then obtains bis(4-aminophenyl)terephthalate through a de-Boc reaction. The main raw material is cheap and easy to obtain, the reaction steps are simple, the preparation method is easy to implement, the reaction selectivity is higher, the side reactions are less, and the reaction yield is high. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] The accompanying drawings constituting a part of the present invention are used to provide a further understanding of the present invention. The exemplary embodiments of the present invention and their descriptions are used to explain the present invention and do not constitute an improper limitation of the present invention. In the accompanying drawings:

[0026] Figure 1 HPLC spectrum of compound II described in the embodiment of the present invention;

[0027] Figure 2 This is the H NMR spectrum of compound II described in the example of the present invention. DETAILED DESCRIPTION

[0028] It should be noted that, in the absence of conflict, the embodiments and features in the embodiments of the present invention can be combined with each other. Unless otherwise defined, the technical terms used in the following embodiments have the same meanings as those generally understood by technicians in the field to which the present invention belongs. The test reagents used in the following embodiments, unless otherwise specified, are all conventional biochemical reagents; the experimental methods, unless otherwise specified, are all conventional methods.

[0029] The present invention will be described in detail below with reference to the accompanying drawings and in conjunction with embodiments.

[0030] The synthetic route of bis(4-aminophenyl)terephthalate is as follows:

[0031]

[0032] Embodiment 1:

[0033] A method for preparing bis(4-aminophenyl)terephthalate (BAPT) comprises the following steps:

[0034] Step (1): The molar ratio of terephthalic acid, N-Boc-4-aminophenol and condensing agent is 1.0:2.2:2.2. Under nitrogen protection, dichloromethane (300 ml) is added to a 2L four-necked bottle, and terephthalic acid (100 g, 1.0 eq), N-Boc-4-aminophenol (277.1 g, 2.2 eq), condensing agent DCC (273.2 g, 2.2 eq), and DMAP (3.7 g, 0.05 eq) are added under stirring, and the temperature is raised to 40° C. and stirred for 3 h. After the reaction is completed by HPLC detection, the filtrate is filtered, the filtrate is concentrated to dryness, methanol (500 ml) is added, stirred for 1 h, filtered, washed with methanol, and dried to obtain 318.0 g of the compound shown in formula I, bis[4-(tert-butyloxycarbonylamino)phenyl]terephthalate, with a yield of 96.3%.

[0035] Step (2): The molar ratio of the compound bis[4-(tert-butyloxycarbonylamino)phenyl]terephthalate of formula I to the acid catalyst is 1.0:0.1. In a 1L four-necked bottle, add the compound of formula I (100 g, 1 eq) and methanol (500 mL), stir evenly, add hydrochloric acid (1.8 g, 0.1 eq), stir and heat to 60°C for 6 h. After the reaction is completed by HPLC, the reaction solution is cooled to 10°C and stirred for 1 h. The reaction solution is filtered, washed with methanol and dried to obtain 58.5 g of bis(4-aminophenyl)terephthalate of formula II, with a yield of 92.1%.

[0036] Embodiment 2:

[0037] A method for preparing bis(4-aminophenyl)terephthalate (BAPT) comprises the following steps:

[0038] Step (1): The molar ratio of terephthalic acid, N-Boc-4-aminophenol and condensing agent is 1.0:3.2:3.2. Under nitrogen protection, chloroform (300 mL) is added to a 2L four-necked bottle, and terephthalic acid (100 g, 1.0 eq), N-Boc-4-aminophenol (403.1 g, 3.2 eq), condensing agent CDI (312.3 g, 3.2 eq) and DMAP (3.7 g, 0.05 eq) are added under stirring, and the temperature is raised to 40°C and stirred for 3 h. After the reaction is completed by HPLC detection, the filtrate is filtered, the filtrate is concentrated to dryness, methanol (500 mL) is added, stirred for 1 h, filtered, washed with methanol, and dried to obtain 305.8 g of the compound shown in formula I, bis[4-(tert-butyloxycarbonylamino)phenyl]terephthalate, with a yield of 92.6%.

[0039] Step (2): The molar ratio of the compound of formula I, bis[4-(tert-butyloxycarbonylamino)phenyl]terephthalate and the acid catalyst is 1.0:0.3. In a 1L four-necked bottle, add the compound of formula I (100 g, 1 eq) and ethanol (500 mL), stir evenly, add sulfuric acid (5.4 g, 0.3 eq), stir and heat to 60°C for 6 h. After the reaction is completed by HPLC, the reaction solution is cooled to 10°C and stirred for 1 h. The reaction solution is filtered, rinsed with methanol, and dried to obtain 61.9 g of bis(4-aminophenyl)terephthalate of the compound of formula II, with a yield of 97.5%.

[0040] Embodiment 3:

[0041] A method for preparing bis(4-aminophenyl)terephthalate (BAPT) comprises the following steps:

[0042] Step (1): The molar ratio of terephthalic acid, N-Boc-4-aminophenol and condensing agent is 1.0:4.2:4.2. Under nitrogen protection, tetrahydrofuran (300 mL) is added to a 2L four-necked bottle, and terephthalic acid (100 g, 1.0 eq), N-Boc-4-aminophenol (403.1 g, 3.2 eq), condensing agent EDCI (484.6 g, 4.2 eq) and DMAP (3.7 g, 0.05 eq) are added under stirring, and the temperature is raised to 40°C and stirred for 3 hours. After the reaction is completed by HPLC detection, the filtrate is filtered, the filtrate is concentrated to dryness, methanol (500 mL) is added, stirred for 1 hour, filtered, washed with methanol, and dried to obtain 292.2 g of the compound shown in formula I, bis[4-(tert-butyloxycarbonylamino)phenyl]terephthalate, with a yield of 88.5%.

[0043] Step (2): The molar ratio of the compound of formula I, bis[4-(tert-butyloxycarbonylamino)phenyl]terephthalate, to the acid catalyst is 1.0:0.8. In a 1L four-necked bottle, add the compound of formula I (100 g, 1 eq) and acetonitrile (500 mL), stir evenly, add phosphoric acid (14.3 g, 0.8 eq), stir and heat to 60°C for 6 h. After the reaction is completed by HPLC, the reaction solution is cooled to 10°C and stirred for 1 h. The reaction solution is filtered, rinsed with methanol, and dried to obtain 55.5 g of bis(4-aminophenyl)terephthalate of the compound of formula II, with a yield of 87.4%.

[0044] Bis(4-aminophenyl)terephthalate was prepared according to the method described in Example 1. Under nitrogen protection, terephthalic acid and N-Boc-4-aminophenol were catalyzed by condensation agents DCC and DMAP to obtain bis[4-(tert-butyloxycarbonylamino)phenyl]terephthalate, and then the Boc protecting group was removed under hydrochloric acid catalysis to obtain bis(4-aminophenyl)terephthalate. The HPLC spectrum of bis(4-aminophenyl)terephthalate synthesized in this example is shown in FIG. Figure 1 As shown, Figure 2 This is the H NMR spectrum using deuterated DMSO as solvent. The H spectrum shows that the product structure is correct.

[0045] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principle of the present invention should be included in the protection scope of the present invention.

Claims

1. A method for preparing bis(4-aminophenyl)terephthalate, characterized in that: The following steps are involved: (1) Under protective gas, terephthalic acid, N-Boc-4-aminophenol, a condensing agent, DMAP and an organic solvent A are mixed uniformly, heated and stirred to react, and after the reaction is completed, filtered, concentrated to dryness, methanol is added, stirred, filtered, rinsed with methanol, and dried to obtain a compound represented by formula I; (2) under protective gas, the compound of formula I obtained in step (1) is mixed evenly with an organic solvent B, an acid catalyst is added, and the mixture is stirred and heated for reaction. After the reaction is completed, the mixture is cooled and stirred, filtered, rinsed with methanol, and dried to obtain a compound of formula II; In step (1), the molar ratio of terephthalic acid, N-Boc-4-aminophenol and condensing agent is: 1.0:(2.2-5.0):(2.2-5.0), and the reaction temperature is 40°C; In step (2), the molar ratio of bis[4-(tert-butyloxycarbonylamino)phenyl]terephthalate to acid is 1.0:(0.1-1.0), and the reaction temperature is 50-70°C; 2. The method for preparing bis(4-aminophenyl)terephthalate according to claim 1, characterized in that: In step (1), the organic solvent A is any one of dichloromethane, chloroform, dichloroethane, tetrahydrofuran, acetonitrile, DMF, NMP, and DMSO.

3. The method for preparing bis(4-aminophenyl)terephthalate according to claim 1, characterized in that: In step (1), the condensation agent is any one of DCC, DIC, CDI and EDCI.

4. The method for preparing bis(4-aminophenyl)terephthalate according to claim 1, characterized in that: In step (2), the organic solvent B is any one of methanol, ethanol, isopropanol, tetrahydrofuran, acetonitrile and 1,4-dioxane.

5. The method for preparing bis(4-aminophenyl)terephthalate according to claim 1, characterized in that: In step (2), the acid catalyst is any one of hydrochloric acid, sulfuric acid, phosphoric acid, trifluoroacetic acid and trifluoromethanesulfonic acid.

6. The method for preparing bis(4-aminophenyl)terephthalate according to claim 1, characterized in that: In step (1) and step (2), the protective gas is an inert gas.

7. The method for preparing bis(4-aminophenyl)terephthalate according to claim 6, characterized in that: The inert gas is nitrogen.

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