A method for preparing 1,4-bis(4-aminophenoxy)benzene

Abstract

This invention provides a method for preparing 1,4-bis(4-aminophenoxy)benzene. In a protective atmosphere, 4-aminophenol and p-dibromobenzene react in an organic solvent under the catalysis of a copper salt, a ligand, and a base to obtain 1,4-bis(4-aminophenoxy)benzene as shown in Formula I. The advantages of this invention are: the coupling method used in this invention has higher reaction selectivity and higher yield; therefore, the preparation method described in this invention is novel, has short reaction steps, good selectivity, and low overall preparation cost with high yield.

Description

Technical Field

[0001] This invention belongs to the field of polyimide monomer synthesis technology, and in particular relates to a method for preparing 1,4-bis(4-aminophenoxy)benzene. Background Technology

[0002] 1,4-Bis(4-aminophenoxy)benzene (TPE-Q) is an important monomer for synthesizing high-performance polyimides. Polyimide (PI) is one of the most heat-resistant thermoplastic engineering plastics currently available, widely used in aerospace, electromechanical, and electronics fields, and is hailed as one of the most promising engineering plastics of the 21st century. 1,4-Bis(4-aminophenoxy)benzene can polymerize with multifunctional anhydrides to form polyimides containing ether bonds, exhibiting even better properties such as improved water resistance, heat resistance, and electrical insulation. It is mainly used in aerospace, electronics, and medical fields. Therefore, the efficient, simple, and low-cost synthesis of 1,4-bis(4-aminophenoxy)benzene through molecular design has significant theoretical and practical application value.

[0003] The structural formula of 1,4-bis(4-aminophenoxy)benzene is as follows:

[0004] Currently, the general method for synthesizing 1,4-bis(4-aminophenoxy)benzene involves the Williamson etherification reaction of hydroquinone with p-halononitrobenzene under alkaline conditions to obtain a dinitro compound, followed by palladium-carbon catalytic hydrogenation or hydrazine hydrate reduction to obtain the product. The reaction steps are lengthy. The first step, the Williamson etherification reaction, usually takes place at high temperatures for a long time and typically uses high-boiling-point aprotic solvents such as DMF and DMSO, making aqueous solution recovery difficult and processing challenging. The second step, the reduction and hydrogenation, requires specialized equipment, and the catalyst palladium-carbon is expensive. Hydrazine hydrate is a potentially explosive chemical, posing significant safety risks to the reaction. (German Patent DE178803C, Chinese Patent CN110256255A)(RSCAdv.,2014,4,7959-7966; Dyes Pigments,2015,121,170-177; RSCAdv.,2016,6,84284-84293; New J.Chem.,2017,41,6607-6615) Summary of the Invention

[0005] In view of this, the present invention aims to provide a method for preparing 1,4-bis(4-aminophenoxy)benzene, which has a simple synthetic route and improves reaction selectivity and product yield.

[0006] To achieve the above objectives, the technical solution of the present invention is implemented as follows:

[0007] A method for preparing 1,4-bis(4-aminophenoxy)benzene includes the following steps:

[0008] Under a protective atmosphere, 4-aminophenol reacts with p-dibromobenzene in an organic solvent in the presence of a copper salt, a ligand, and a base to give 1,4-bis(4-aminophenoxy)benzene.

[0009] The synthesis route is as follows:

[0010]

[0011] Further, under a protective atmosphere, copper salt and ligands were added to an organic solvent, followed by the addition of 4-aminophenol and p-dibromobenzene with stirring. Finally, alkali was added, and the temperature was controlled at 20-40°C. The system was maintained at 40°C with stirring for 2 hours. After the reaction was completed as detected by HPLC, the mixture was cooled, water was added, filtered, washed with water and ethanol, and dried to obtain 1,4-bis(4-aminophenoxy)benzene.

[0012] Furthermore, the molar ratio of the starting materials p-dibromobenzene, 4-aminophenol, copper salt, ligand, and base is 1:(2-4):(0.01-0.05):(0.02-0.1):(2-4). Within this range, the reaction of p-dibromobenzene is most complete, resulting in the highest yield.

[0013] Furthermore, the organic solvent is one or more of tetrahydrofuran, acetone, acetonitrile, ethylene glycol dimethyl ether, chloroform, and 1,4-dioxane.

[0014] Furthermore, the base is one or more of sodium hydroxide, potassium hydroxide, sodium carbonate, potassium carbonate, cesium carbonate, triethylamine, N,N-diisopropylethylamine, tri-n-propylamine, and N-methylmorpholine.

[0015] Furthermore, the copper salt is one or more of copper sulfate, copper bromide, copper chloride, copper iodide, copper acetate, copper nitrate, and copper oxalate.

[0016] Furthermore, the ligand is one or more of glycine, alanine, leucine, proline, and valine.

[0017] Furthermore, the protective gas is an inert gas, preferably nitrogen.

[0018] Compared with the prior art, the method for preparing 1,4-bis(4-aminophenoxy)benzene described in this invention has the following advantages:

[0019] This invention uses p-dibromobenzene and 4-aminophenol as main raw materials to obtain 1,4-bis(4-aminophenoxy)benzene via copper-catalyzed coupling. The reaction steps are simple, and the coupling method used in this invention has higher reaction selectivity and higher reaction yield. Therefore, the preparation method described in this invention is novel, has short reaction steps, good selectivity, and low overall preparation cost with high yield. Detailed Implementation

[0020] It should be noted that, unless otherwise specified, the embodiments and features described in the present invention can be combined with each other.

[0021] The present invention will now be described in detail with reference to the embodiments.

[0022] The synthetic route for 1,4-bis(4-aminophenoxy)benzene is as follows:

[0023]

[0024] Example 1:

[0025] A method for preparing 1,4-bis(4-aminophenoxy)benzene includes the following steps:

[0026] The molar ratio of p-dibromobenzene to 4-aminophenol was 1:2. Under nitrogen protection, copper sulfate (0.68 g, 0.01 eq), glycine (0.64 g, 0.02 eq), and tetrahydrofuran (1000 mL) were added to a 2 L four-necked flask and stirred until homogeneous. Then, 4-aminophenol (92.5 g, 2 eq) and p-dibromobenzene (100 g, 1 eq) were added, followed by sodium hydroxide (33.9 g, 2 eq). The temperature was controlled at 20-40 °C and stirred at 40 °C for 6 h. After the reaction was completed by HPLC, the mixture was cooled, water was added, filtered, washed with water, rinsed with cold ethanol, and dried to obtain 111.5 g of compound 1,4-bis(4-aminophenoxy)benzene, as shown in Formula I, with a yield of 90.0%.

[0027] In the above reaction, in order to ensure that the substrates dibromobenzene and 4-aminophenol can fully contact and participate in the reaction, a polar organic solvent should be selected. Therefore, tetrahydrofuran can also be replaced by acetone, acetonitrile, ethylene glycol dimethyl ether, chloroform or 1,4-dioxane.

[0028] The alkali acts as an acid-binding agent and can be a commonly used inorganic or organic alkali. Therefore, sodium hydroxide can also be replaced with potassium hydroxide, sodium carbonate, potassium carbonate, cesium carbonate, triethylamine, N,N-diisopropylethylamine, tri-n-propylamine, or N-methylmorpholine.

[0029] The copper salt plays a catalytic role by coordinating with the ligand. Commonly used divalent copper salts can be selected. Therefore, copper sulfate can also be replaced by copper bromide, copper chloride, copper iodide, copper acetate, copper nitrate, or copper oxalate.

[0030] The ligand plays a catalytic role in coordination with copper and can be selected from commonly used α amino acids. Therefore, glycine can also be replaced with alanine, leucine, proline, or valine.

[0031] Example 2:

[0032] A method for preparing 1,4-bis(4-aminophenoxy)benzene includes the following steps:

[0033] The molar ratio of p-dibromobenzene to 4-aminophenol was 1:2.5. Under nitrogen protection, copper bromide (1.89 g, 0.02 eq), alanine (1.51 g, 0.04 eq), and acetonitrile (1000 mL) were added to a 2 L four-necked flask and stirred until homogeneous. Then, 4-aminophenol (115.7 g, 2.5 eq) and p-dibromobenzene (100 g, 1 eq) were added, followed by potassium carbonate (146.5 g, 2.5 eq). The temperature was maintained at 20-40 °C and stirred for 6 h at 40 °C. After the reaction was completed as determined by HPLC, the mixture was cooled, water was added, filtered, washed with water, rinsed with cold ethanol, and dried to obtain 115.5 g of 1,4-bis(4-aminophenoxy)benzene, as shown in Formula I, with a yield of 93.2%.

[0034] Example 3:

[0035] A method for preparing 1,4-bis(4-aminophenoxy)benzene includes the following steps:

[0036] The molar ratio of p-dibromobenzene to 4-aminophenol was 1:3. Under nitrogen protection, copper acetate (2.31 g, 0.03 eq), proline (2.93 g, 0.06 eq), and ethylene glycol dimethyl ether (1000 mL) were added to a 2 L four-necked flask and stirred until homogeneous. Then, 4-aminophenol (138.8 g, 3 eq) and p-dibromobenzene (100 g, 1 eq) were added, followed by triethylamine (128.7 g, 3 eq). The temperature was controlled at 20-40 °C and stirred at 40 °C for 6 h. After the reaction was completed as determined by HPLC, the mixture was cooled, water was added, filtered, washed with water, rinsed with cold ethanol, and dried to obtain 122.2 g of 1,4-bis(4-aminophenoxy)benzene, as shown in Formula I, with a yield of 98.6%.

[0037] Example 4:

[0038] A method for preparing 1,4-bis(4-aminophenoxy)benzene includes the following steps:

[0039] The molar ratio of p-dibromobenzene to 4-aminophenol was 1:3.5. Under nitrogen protection, copper nitrate (2.15 g, 0.04 eq), leucine (4.45 g, 0.08 eq), and chloroform (1000 mL) were added to a 2 L four-necked flask and stirred until homogeneous. Then, 4-aminophenol (161.9 g, 3.5 eq) and p-dibromobenzene (100 g, 1 eq) were added, followed by N,N-diisopropylethylamine (191.8 g, 3.5 eq). The temperature was controlled at 20-40 °C and stirred at 40 °C for 6 h. After the reaction was completed by HPLC, the mixture was cooled, water was added, filtered, washed with water, rinsed with cold ethanol, and dried to obtain 119.1 g of 1,4-bis(4-aminophenoxy)benzene, as shown in Formula I, with a yield of 96.1%.

[0040] Example 5:

[0041] A method for preparing 1,4-bis(4-aminophenoxy)benzene includes the following steps:

[0042] The molar ratio of p-dibromobenzene to 4-aminophenol was 1:4. Under nitrogen protection, copper oxalate (3.21 g, 0.05 eq), valine (4.97 g, 0.1 eq), and chloroform (1000 mL) were added to a 2 L four-necked flask and stirred until homogeneous. Then, 4-aminophenol (185.0 g, 4 eq) and p-dibromobenzene (100 g, 1 eq) were added, followed by N-methylmorpholine (171.5 g, 4 eq). The temperature was controlled at 20-40 °C and stirred at 40 °C for 6 h. After the reaction was completed as detected by HPLC, the mixture was cooled, water was added, filtered, washed with water, rinsed with cold ethanol, and dried to obtain 113.1 g of compound 1,4-bis(4-aminophenoxy)benzene, as shown in Formula I, with a yield of 91.3%.

[0043] Comparative Example 1:

[0044] The molar ratio of p-dibromobenzene to 4-aminophenol was 1:3. Under nitrogen protection, copper acetate (2.31 g, 0.03 eq) and ethylene glycol dimethyl ether (1000 mL) were added to a 2 L four-necked flask and stirred until homogeneous. Then, 4-aminophenol (138.8 g, 3 eq) and p-dibromobenzene (100 g, 1 eq) were added, followed by triethylamine (128.7 g, 3 eq). The temperature was controlled at 20-40 °C and stirred at 40 °C for 24 h. HPLC analysis showed that 70% of the p-dibromobenzene remained in the feedstock.

[0045] Comparative Example 2:

[0046] The molar ratio of p-dibromobenzene to 4-aminophenol was 1:3. Under nitrogen protection, proline (2.93 g, 0.06 eq) and ethylene glycol dimethyl ether (1000 mL) were added to a 2 L four-necked flask and stirred until homogeneous. Then, 4-aminophenol (138.8 g, 3 eq) and p-dibromobenzene (100 g, 1 eq) were added, followed by triethylamine (128.7 g, 3 eq). The temperature was controlled at 20-40 °C and stirred at 40 °C for 24 h. HPLC analysis showed no formation of the target product.

[0047] The conventional route involves first preparing the dinitro compound and then reducing it to an amino group, requiring at least two steps. The route described in this application is a one-step reaction. Existing technologies typically use palladium on carbon as a catalyst in the nitro reduction step, which is expensive. The copper salt catalyst used in this application is cheaper, resulting in a synthesis cost at least 1000 yuan / kg lower.

[0048] 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 principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for preparing 1,4-bis(4-aminophenoxy)benzene, characterized in that: The process includes the following steps: In a protective gas atmosphere, 4-aminophenol and p-dibromobenzene react in an organic solvent under the catalysis of copper salt, ligand, and base to give 1,4-bis(4-aminophenoxy)benzene as shown in Formula I; （Ⅰ）； The copper salt is copper acetate; The ligand is proline; The base is triethylamine.

2. The method for preparing 1,4-bis(4-aminophenoxy)benzene according to claim 1, characterized in that: The molar ratio of p-dibromobenzene, 4-aminophenol, copper salt, ligand and base is 1:(2~4):(0.01~0.05):(0.02~0.1):(2~4).

3. The method for preparing 1,4-bis(4-aminophenoxy)benzene according to claim 1, characterized in that: Organic solvents include one or more of tetrahydrofuran, acetone, acetonitrile, ethylene glycol dimethyl ether, chloroform, and 1,4-dioxane.

4. The method for preparing 1,4-bis(4-aminophenoxy)benzene according to claim 1, characterized in that: Dibromobenzene, 4-aminophenol, copper salt, ligand, and base are added to an organic solvent, and the system temperature is controlled at 30-50℃.

5. The method for preparing 1,4-bis(4-aminophenoxy)benzene according to claim 1, characterized in that: The protective gas is an inert gas.

6. The method for preparing 1,4-bis(4-aminophenoxy)benzene according to claim 1, characterized in that: The protective gas is nitrogen.

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