A synthesis process of 2,3,6,7-naphthalene tetracarboxylic dianhydride

Abstract

The application belongs to the technical field of high polymer materials, and particularly relates to a synthesis process of 2,3,6,7-naphthalene tetracarboxylic dianhydride. The steps are as follows: alpha,alpha,alpha',alpha',4,5-hexabromo-o-xylene is reacted with 2-(triphenylphosphoranyl) butanedioic acid dialkyl ester in an organic solvent in the presence of an acid-binding agent to obtain 6,7-dibromo-2,3-naphthalene dicarboxylate; the 6,7-dibromo-2,3-naphthalene dicarboxylate is reacted with a cyanation reagent to obtain 6,7-dicyano-2,3-naphthalene dicarboxylate; the 6,7-dicyano-2,3-naphthalene dicarboxylate is hydrolyzed in an alkaline aqueous solution, and after the reaction is completed, acidification is performed to obtain 2,3,6,7-naphthalene tetracarboxylic acid; and the 2,3,6,7-naphthalene tetracarboxylic acid is dehydrated in an acid anhydride environment to obtain 2,3,6,7-naphthalene tetracarboxylate dianhydride. The application has the advantages that raw and auxiliary materials are easy to obtain and low in cost, is suitable for mass industrial production, the synthesis process avoids harsh environments such as high temperature and high pressure, the conversion rate is high, the product quality is stable, and high-purity products can be obtained.

Description

Technical Field

[0001] This invention belongs to the field of polymer materials technology, specifically relating to a synthesis process of 2,3,6,7-naphthalenetetracarboxylic dianhydride. Background Technology

[0002] Naphthalenetetracarboxylic dianhydride (NTCDA) is an important organic synthetic intermediate with broad application prospects in high-performance polymers, dyes, and optoelectronic materials. However, current synthetic routes all have many drawbacks, making it difficult to achieve efficient, economical, and safe large-scale industrial production processes. A detailed analysis follows: The literature Bulletin of the Chemical Society of Japan, 1975, vol. 48, pp. 2842-2847 reports a route for the synthesis of 2,3,6,7-naphthalenetetracarboxylic acid: The process involves lengthy synthesis steps, low yield, high cost, and high-level oxidation operations. It also has high equipment requirements and poor safety, making it unfeasible for industrial production and widespread application.

[0003] 2. The literature *Chemistry Letters*, 1988, pp. 1933-1936, proposes using potassium salts of 1-naphthoic acid or 2-naphthoic acid as raw materials, reacting them under high temperature and high pressure conditions at 480°C in the presence of a catalyst to obtain a mixture containing approximately 18% product (sodium 2,3,6,7-naphthotetrate / potassium 2,3,6,7-naphthotetrate). This mixture is then separated to obtain the final product. However, this method not only requires harsh high-temperature reaction conditions and equipment with high pressure and temperature resistance, but also suffers from low product yield and difficulties in subsequent separation and purification.

[0004] 3. Literature such as *Chinese Chemical Letters*, 2025, vol. 36, #6, art. no. 110290 and *Journal of Materials Chemistry*, 2020, vol. 8, #6, pp. 2186-2195, reports a synthetic process for 6,7-dibromo-2,3-naphthalenedicarboxylate, which involves reacting α,α,α',α',4,5-hexabromo-o-xylene with dimethyl maleate in the presence of equimolar sodium iodide. This process requires a large amount of expensive iodide, resulting in extremely high costs and poor atom economy, thus limiting its commercial viability.

[0005] 4. Another synthetic process reported in the literature Journal of Organometallic Chemistry, 1994, vol. 468, #1-2, p.273-278: The raw materials used are difficult to obtain, and the production conditions are harsh, making it unsuitable for large-scale production.

[0006] In summary, current synthesis processes for naphthalene tetracarboxylic dianhydride (NTCDA) generally suffer from problems such as numerous reaction steps, low overall yield, high production costs, high operational risks, and the use of expensive materials. No synthesis process suitable for large-scale industrial production has been found on the market.

[0007] Therefore, developing a process for synthesizing naphthalene tetracarboxylic dianhydride that uses readily available raw materials, involves simple steps, operates under mild conditions, has high yield, low cost, and is resistant to high temperatures is of significant industrial application value and is a technical problem that urgently needs to be solved in this field. Summary of the Invention

[0008] The purpose of this invention is to solve the problem that naphthalene tetracarboxylic dianhydride (NTCDA) cannot be produced on a large industrial scale in the prior art, and to provide a synthesis process for 2,3,6,7-naphthalene tetracarboxylic dianhydride.

[0009] To achieve the above objectives, the present invention provides a synthesis process for 2,3,6,7-naphthalenetetracarboxylic dianhydride, characterized in that the synthesis process includes the following steps. The specific steps are as follows: α,α,α',α',4,5-hexabromo-o-xylene and 2-(triphenylphosphine)-succinic acid dialkyl ester were reacted in an organic solvent in the presence of an acid-binding agent to give 6,7-dibromo-2,3-naphthalenedicarboxylate. 6,7-dibromo-2,3-naphthalenedicarboxylate was reacted with a cyaniding agent to give 6,7-dicyano-2,3-naphthalenedicarboxylate. 6,7-dicyano-2,3-naphthalenedicarboxylate was hydrolyzed in an alkaline aqueous solution, and then acidified after the reaction to obtain 2,3,6,7-naphthalenetetracarboxylic acid; 2,3,6,7-naphthocarboxylic acid is dehydrated in an anhydride environment to give 2,3,6,7-naphthocarboxylic dianhydride.

[0010] The molar ratio of α,α,α',α',4,5-hexabromo-o-xylene to 2-(triphenylphosphine)-dialkyl succinate is 1:(1-1.2); the molar ratio of 2-(triphenylphosphine)-dialkyl succinate to the acid-binding agent is 1:(4-8); and the reaction temperature in step a is 20~100℃.

[0011] The organic solvent in step a is selected from one or more of N,N-dimethylformamide, N-methylpyrrolidone, hexamethylphosphoric triamine, and dimethyl sulfoxide; the acid-binding agent is selected from one or more of sodium carbonate, potassium carbonate, sodium formate, sodium acetate, 1,8-diazabicycloundec-7-ene, and triethylamine.

[0012] The cyaniding agent is cuprous cyanide; the molar ratio of 6,7-dibromo-2,3-naphthalenedicarboxylate to cuprous cyanide is 1:(2-3); the reaction solvent is selected from one or more of N,N-dimethylformamide, N-methylpyrrolidone, hexamethylphosphoric triamine, and dimethyl sulfoxide; the reaction temperature is controlled at 60~150℃.

[0013] The alkaline aqueous solution is an aqueous solution of sodium hydroxide; the amount of sodium hydroxide used is 8 to 12 times the molar amount of 6,7-dibromo-2,3-naphthalenedicarboxylate; the reaction temperature is 80 to 100°C; the acidification is to adjust the pH value to 1 to 2.

[0014] The acid anhydride mentioned is acetic anhydride, and the amount of acetic anhydride used is 6 to 20 times the molar amount of 2,3,6,7-naphthalenetetracarboxylic acid.

[0015] The synthesis process steps are in the following order: S1. S2. S3. The specific steps of step S1 are as follows: under the protection of an inert gas, triphenylphosphine is reacted with alkyl halogenated acetate in an organic solvent, and then an alkaline substance is added for treatment to obtain 2-(triphenylphosphine)-dialkyl succinate.

[0016] The specific steps of step S3 are as follows: 2,3,6,7-naphthalenetetracarboxylic acid is mixed with acetic anhydride, and the mixture is heated to 80~120℃. Then it is filtered, and the filter cake is recrystallized with toluene and dried to obtain 2,3,6,7-naphthalenetetracarboxylic acid dianhydride.

[0017] The beneficial effects of this invention are as follows: The raw and auxiliary materials used in this synthesis process are readily available and inexpensive, making it suitable for large-scale industrial production.

[0018] This synthesis process avoids the harsh conditions that make industrial implementation difficult, such as high temperature and high pressure.

[0019] This synthesis process has a high conversion rate, stable product quality, and can produce high-purity products.

[0020] The naphthalene tetracarboxylic dianhydride (NTCDA) synthesized by this process exhibits high-temperature resistance: after polyimide resins are synthesized from NTCDA, they can withstand high-temperature environments exceeding 300°C, making them widely used in temperature-sensitive fields such as electronic packaging materials and aerospace components. As a monomer for high-performance polyimide materials, NTCDA can also be used to manufacture flexible circuit board substrates and semiconductor packaging materials, featuring high insulation and low dielectric constant. Attached Figure Description

[0021] Figure 1This is the 1H NMR spectrum of 2,3,6,7-naphthalenetetracarboxylic dianhydride prepared in the embodiments of the present invention.

[0022] Figure 2 This is the 1H NMR spectrum of 2,3,6,7-naphthocarboxylic acid prepared in the embodiments of the present invention.

[0023] Figure 3 This is the 1H NMR spectrum of the 6,7-dibromo-2,3-naphthalenedicarboxylate prepared in this invention.

[0024] Figure 4 This is the 1H NMR spectrum of the 6,7-dicyano-2,3-naphthalenedicarboxylate prepared in this invention. Detailed Implementation

[0025] The present invention will be further described in detail below with reference to specific embodiments.

[0026] 5.1 Preparation of 2-(triphenylphosphine)-succinic acid diester Example: 26.2 g of triphenylphosphine and 80 mL of dichloromethane were added to a 250 mL three-necked flask. Under N2 protection, 16.7 g of ethyl bromoacetate was added dropwise over 0–3 hours with stirring at room temperature. During the addition, a white solid precipitated. After the addition was complete, the mixture was stirred at 0–50 °C for 6–20 hours. After the reaction was maintained at this temperature, 24 g of potassium carbonate was added in portions. After the addition was complete, another 16.7 g of ethyl bromoacetate was added, and the mixture was refluxed for 4 hours. After the reaction was monitored by TLC, the mixture was cooled to room temperature and filtered. The filtrate was distilled under reduced pressure to remove the solvent and recrystallized from cyclohexane to obtain 34.1 g of dimethyl 2-(triphenylphosphine)-succinate (yield: 83.8%, LC: 98.3%, relative to triphenylphosphine).

[0027] 5.2. Preparation of 6,7-dibromo-2,3-naphthalenedicarboxylate Example 1: DMF: 145g, g α,α,α',α',4,5-hexabromo-o-xylene: 29.02g, dimethyl 2-(triphenylphosphine)-succinate: 22.3g, sodium acetate: 32.8g were added sequentially to a 500ml three-necked flask; the reaction temperature was controlled at 40~60℃ and stirred for 6 hours; after the reaction was completed by TLC (PE:EA=5:1), the reaction solution was cooled to 10~20℃, 300g of water was added and stirred for 10 minutes, and then filtered; the filter cake was purified with 380g methanol:water = 2:1 mixture to obtain 16.72g of methyl 6,7-dibromo-2,3-naphthalenedicarboxylate (HPLC: 98.6%; yield: 83.2%).

[0028] Example 2: NMP: 150g, g α,α,α',α',4,5-hexabromo-o-xylene: 29.02g, dimethyl 2-(triphenylphosphine)-succinate: 22.3g, sodium acetate: 32.8g were added sequentially to a 500ml three-necked flask; the reaction temperature was controlled at 65~80℃ and stirred for 8 hours; after the reaction was completed by TLC (PE:EA=5:1), the reaction solution was cooled to 10~20℃, 300g of water was added and stirred for 10 minutes, and then filtered; the filter cake was purified with 380g methanol:water = 2:1 mixture to obtain 15.6g of methyl 6,7-dibromo-2,3-naphthalenedicarboxylate (HPLC: 97.8%; yield: 77.6%).

[0029] Example 3: DMF: 145g, g α,α,α',α',4,5-hexabromo-o-xylene: 29.02g, dimethyl 2-(triphenylphosphine)-succinate: 22.3g, and triethylamine: 30.35g were added sequentially to a 500ml three-necked flask; the reaction temperature was controlled at 60~80℃ and stirred for 6 hours; after the reaction was completed by TLC (PE:EA=5:1), the reaction solution was cooled to 10~20℃, 300g of water was added and stirred for 10 minutes, and then filtered; the filter cake was purified with 380g of methanol:water = 2:1 mixture to obtain 15.25g of methyl 6,7-dibromo-2,3-naphthalenedicarboxylate (HPLC: 98.1%; yield: 75.85%).

[0030] Example 4: DMF: 145g, g α,α,α',α',4,5-hexabromo-o-xylene: 29.02g, dimethyl 2-(triphenylphosphine)-succinate: 22.3g, sodium formate: 27.2g were added sequentially to a 500ml three-necked flask; the reaction temperature was controlled at 40~60℃ and stirred for 6 hours; after the reaction was completed by TLC (PE:EA=5:1), the reaction solution was cooled to 10~20℃, 300g of water was added and stirred for 10 minutes, and then filtered; the filter cake was purified with 380g methanol:water = 2:1 mixture to obtain 18.5g of methyl 6,7-dibromo-2,3-naphthalenedicarboxylate (HPLC: 99.2%; yield: 92.0%).

[0031] Preparation of 5,3,6,7-dicyano-2,3-naphthalenedicarboxylate Example 1: In a 1000ml three-necked flask, the following were added sequentially: NMP: 100.0g, methyl 6,7-dibromo-2,3-naphthalenedicarboxylate: 20.1g, and cuprous cyanide: 13.45g. After adding the materials, the mixture was purged with nitrogen three times. The temperature was raised to 135℃~140℃ and stirred for 14 hours. After TLC showed the disappearance of the intermediate, the temperature was lowered to an internal temperature of 30~40℃. 600g of dichloromethane was added to the reaction solution and stirred for 15 minutes. The temperature was then lowered to 10~20℃. The mixture was filtered, and the filtrate was washed three times with 300ml of 2% ammonia water, retaining the organic layer. 500~550g of dichloromethane was distilled off the organic layer under normal pressure, and the mixture was cooled to 0~5℃ and filtered. The filter cake was dried in a forced-air oven at 60℃ to obtain 8.53g of methyl 6,7-dicyano-2,3-naphthalenedicarboxylate (purity: 98.7%; yield: 58.0%).

[0032] Example 2: DMF was added sequentially to a 1000ml three-necked bottle. 80.0g of methyl 6,7-dibromo-2,3-naphthalenedicarboxylate, 20.1g of methyl 6,7-dibromo-2,3-naphthalenedicarboxylate, and 13.45g of cuprous cyanide were added under stirring at room temperature. After the addition was completed, the mixture was purged with nitrogen three times. The temperature was raised to 120℃~130℃ and stirred for 8 hours. After TLC showed the disappearance of the intermediate, the temperature was lowered to 30~40℃. 600g of dichloromethane was added to the reaction solution and stirred for 15 minutes. The temperature was then lowered to 10~20℃ and filtered. The filter cake was slurried and filtered at room temperature with 200ml of dichloromethane. The filtrates were combined and washed three times with 2% ammonia water (250ml). The organic layer was retained. 700~750g of dichloromethane was distilled off the organic layer under normal pressure. The mixture was then cooled to 0~5℃ and filtered. The filter cake was dried in a forced-air oven at 60℃ to obtain 10.86g of methyl 6,7-dicyano-2,3-naphthalenedicarboxylate (purity: 99.3%; yield: 73.8%).

[0033] Preparation of 5.4,2,3,6,7-naphthotetracarboxylic acid Example: 67.8 g of water and 19.76 g of sodium hydroxide were added to a 250 ml three-necked flask. After stirring until dissolved, 14.53 g of methyl 6,7-dicyano-2,3-naphthalenedicarboxylate was added. The mixture was heated to 100°C and held at that temperature for 18 hours. After the reaction was complete as detected by liquid chromatography, the mixture was cooled to an internal temperature of 5-15°C. The pH was adjusted to 1-2 with hydrochloric acid. A large amount of solid precipitated out. The mixture was filtered, and the filter cake was washed with water and then slurried with 30 ml of methanol at room temperature. The resulting white to off-white solid was dried at 60°C to obtain 12.93 g of 2,3,6,7-naphthalenedicarboxylate (HPLC 99.6%; yield 86.04%). The 1H NMR spectrum of the obtained product is shown below. Figure 2 As shown.

[0034] 5.5 Preparation of 2,3,6,7-naphthalenetetracarboxylic dianhydride Example: Acetic anhydride (52.0 g) and 2,3,6,7-naphthalenetetracarboxylic acid (15.2 g) were added to a 250 ml three-necked flask. Under nitrogen protection, the mixture was refluxed for 24 hours and then cooled to 10-25°C. The mixture was filtered, and the filter cake was purified with toluene to obtain the product 2,3,6,7-naphthalenetetracarboxylic acid dianhydride. The 1H NMR spectrum of the obtained product is shown below. Figure 1 As shown.

[0035] The above is a detailed description of the embodiments, which is intended to enable those skilled in the art to correctly understand and use the present invention. Any improvements or modifications to technical solutions obtained by those skilled in the art based on the present invention and on the existing technology, without innovative effort but only through analysis, analogy, or limited enumeration, should be within the scope of protection defined by the claims.

Claims

1. A process for synthesizing 2,3,6,7-naphthalenetetracarboxylic dianhydride, characterized in that... The synthesis process includes the following steps: 。 2. The synthesis process of 2,3,6,7-naphthalenetetracarboxylic dianhydride as described in claim 1, characterized in that... The specific steps are as follows: α,α,α',α',4,5-hexabromo-o-xylene and 2-(triphenylphosphine)-succinic acid dialkyl ester were reacted in an organic solvent in the presence of an acid-binding agent to give 6,7-dibromo-2,3-naphthalenedicarboxylate. 6,7-dibromo-2,3-naphthalenedicarboxylate was reacted with a cyaniding agent to give 6,7-dicyano-2,3-naphthalenedicarboxylate. 6,7-dicyano-2,3-naphthalenedicarboxylate was hydrolyzed in an alkaline aqueous solution, and then acidified after the reaction to obtain 2,3,6,7-naphthalenetetracarboxylic acid; 2,3,6,7-naphthalenetetracarboxylic acid is dehydrated in an anhydride environment to give 2,3,6,7-naphthalenetetracarboxylic dianhydride.

3. The synthesis process of 2,3,6,7-naphthalenetetracarboxylic dianhydride as described in claim 2, characterized in that... The molar ratio of α,α,α',α',4,5-hexabromo-o-xylene to 2-(triphenylphosphine)-dialkyl succinate is 1:(1-1.2); the molar ratio of 2-(triphenylphosphine)-dialkyl succinate to the acid-binding agent is 1:(4-8); and the reaction temperature in step a is 20~100℃.

4. The synthesis process of 2,3,6,7-naphthalenetetracarboxylic dianhydride as described in claim 2, characterized in that... The organic solvent in step a is selected from one or more of N,N-dimethylformamide, N-methylpyrrolidone, hexamethylphosphoric triamine, and dimethyl sulfoxide; the acid-binding agent is selected from one or more of sodium carbonate, potassium carbonate, sodium formate, sodium acetate, 1,8-diazabicycloundec-7-ene, and triethylamine.

5. The synthesis process of 2,3,6,7-naphthalenetetracarboxylic dianhydride as described in claim 2, characterized in that... The cyaniding agent is cuprous cyanide; the molar ratio of 6,7-dibromo-2,3-naphthalenedicarboxylate to cuprous cyanide is 1:(2-3); the reaction solvent is selected from one or more of N,N-dimethylformamide, N-methylpyrrolidone, hexamethylphosphoric triamine, and dimethyl sulfoxide; the reaction temperature is controlled at 60~150℃.

6. The synthesis process of 2,3,6,7-naphthalenetetracarboxylic dianhydride as described in claim 2, characterized in that... The alkaline aqueous solution is an aqueous solution of sodium hydroxide; the amount of sodium hydroxide used is 8 to 12 times the molar amount of 6,7-dibromo-2,3-naphthalenedicarboxylate; the reaction temperature is 80 to 100°C; the acidification is to adjust the pH value to 1 to 2.

7. The synthesis process of 2,3,6,7-naphthalenetetracarboxylic dianhydride as described in claim 2, characterized in that... The acid anhydride mentioned is acetic anhydride, and the amount of acetic anhydride used is 6 to 20 times the molar amount of 2,3,6,7-naphthalenetetracarboxylic acid.

8. The synthesis process of 2,3,6,7-naphthalenetetracarboxylic dianhydride as described in claim 1, characterized in that... The synthesis process steps are in the following order: S1. ； S2. ； S3. 。 9. The synthesis process of 2,3,6,7-naphthalenetetracarboxylic dianhydride as described in claim 7, characterized in that... The specific steps of step S1 are as follows: under the protection of an inert gas, triphenylphosphine is reacted with alkyl halogenated acetate in an organic solvent, and then an alkaline substance is added for treatment to obtain 2-(triphenylphosphine)-dialkyl succinate.

10. The synthesis process of 2,3,6,7-naphthalenetetracarboxylic dianhydride as described in claim 7, characterized in that... The specific steps of step S3 are as follows: 2,3,6,7-naphthalenetetracarboxylic acid is mixed with acetic anhydride, and the mixture is heated to 80~120℃. Then it is filtered, and the filter cake is recrystallized with toluene and dried to obtain 2,3,6,7-naphthalenetetracarboxylic acid dianhydride.

Images