Method for synthesizing 2,3,3',4'-biphenyltetracarboxylic dianhydride

Abstract

The application discloses a synthesis method of 2,3,3',4'-biphenyl tetracarboxylic dianhydride, characterized in that 2,3-dimethylaniline is used as a starting raw material, 2,3-dimethylaniline diazonium salt is prepared through a diazotization reaction, then 2,3,3',4'-tetramethyl biphenyl is prepared through a coupling reaction of the 2,3-dimethylaniline diazonium salt and o-xylene under the catalysis of cuprous chloride, and finally 2,3,3',4'-biphenyl tetracarboxylic dianhydride is prepared through an oxidation reaction and dehydration to form anhydride. The coupling reaction in the synthesis method has good selectivity, 3,3,4',4'-tetramethyl biphenyl which is difficult to separate is not generated, high-purity a-BPDA can be finally obtained, and the coupling reaction in the synthesis method only needs to use low-cost cuprous chloride as a catalyst, so that the production cost is greatly reduced compared to a high-cost catalytic system in the prior art, and the synthesis method is more suitable for industrial mass production.

Description

Technical Field

[0001] This invention belongs to the field of organic synthesis technology, specifically relating to a method for synthesizing 2,3,3',4'-biphenyltetracarboxylic dianhydride. Background Technology

[0002] 2,3,3',4'-Biphenyltetracarboxylic dianhydride, abbreviated as α-BPDA, is a white solid with a melting point of 195–205 °C and a molecular formula of C2. 16 H6O6, with a relative molecular weight of 294.22 and CAS number 36978-41-3, has the following structural formula:

[0003] .

[0004] Polyimides possess excellent mechanical properties, heat resistance, radiation resistance, low dielectric constant, and hydrolysis resistance, leading to their widespread application in aerospace, defense, and electronics industries. Among these, biphenyl dianhydride polymers are one of the most widely used products in high-temperature resistant polyimide materials. In biphenyl dianhydrides, asymmetric biphenyl dianhydrides (i.e., 2,3,3',4'-biphenyl dianhydrides) can both increase the glass transition temperature and reduce the melt viscosity of the resin, significantly improving the material's processing performance.

[0005] Currently, the main methods for synthesizing 2,3,3',4'-biphenyltetracarboxylic dianhydride are as follows:

[0006] (1) 2,3,3',4'-biphenyltetracarboxylic dianhydride is prepared by cross-coupling, hydrolysis and dehydration of 3- and 4-halophthalic acid diesters to anhydride [CN1436780A], or 2,3,3',4'-biphenyltetracarboxylic dianhydride is prepared by cross-coupling, hydrolysis and dehydration of 3- and 4-halophthalimides to anhydride [CN101481366A], or 2,3,3',4'-biphenyltetracarboxylic dianhydride is prepared by cross-coupling, hydrolysis and dehydration of 3- and 4-o-xylenes to anhydride. 2,3,3',4'-biphenyltetracarboxylic dianhydride can be prepared by aqueous anhydride formation [CN102020622A], or by direct cross-coupling of 3- and 4-halophthalic anhydrides to obtain 2,3,3',4'-biphenyltetracarboxylic dianhydride [CN108250169A], or by cross-coupling and dehydration of 3- and 4-halophthalic acids to obtain 2,3,3',4'-biphenyltetracarboxylic dianhydride [CN118666788A].

[0007] The shortcomings of the above methods are: (1) The cross-coupling reaction has poor selectivity, and the three isomers are not easy to separate and purify, resulting in low purity of the target product 2,3,3',4'-biphenyltetracarboxylic dianhydride [the above literature does not have data on the purity of the target product]. (2) The cross-coupling reaction requires an expensive catalytic system, resulting in high production costs.

[0008] (2) Starting with 2,3-methylaniline, 2,3-methylbromobenzene is first reacted to obtain 2,3-methylbromobenzene, and then 2,3-dimethylphenylboronic acid is obtained by Grignard reaction. Then, it is reacted with N-methyl-4-chlorophthalimide in the presence of palladium catalyst to obtain 5-(2,3-dimethylphenyl)-2-methylisoindole-1,3-dione. Finally, it is oxidized and dehydrated to form anhydride to obtain 2,3,3',4'-biphenyltetracarboxylic dianhydride [CN114230540A].

[0009] Although this method has high selectivity for coupling reaction and high purity of target product, it still has the following shortcomings: (1) It still requires the use of expensive catalytic system, resulting in high production cost; (2) The synthesis route is long and the overall yield is low. In particular, the Grignard reaction has low safety and is not suitable for large-scale industrial production.

[0010] (3) 4-Chlorophthalic acid diester first reacts with diboronic acid / diboronic acid ester in the presence of palladium catalyst to obtain intermediate arylboronic acid / boronic acid ester, then couples with 3-chlorophthalic acid ester to obtain 2,3,3',4'-biphenyltetracarboxylate tetraester, and finally hydrolyzes and dehydrates to form anhydride to obtain 2,3,3',4'-biphenyltetracarboxylic dianhydride [CN115894416A].

[0011] Although this method has high selectivity for coupling reaction and high purity of target product, it still has the following shortcomings: (1) It still requires the use of expensive catalytic system, resulting in high production cost; (2) The coupling reaction temperature is high, resulting in high energy consumption, which is not suitable for large-scale industrial production.

[0012] (4) 3-Halogenated o-xylene is first reacted with a lithium reagent to obtain 3-lithiumized o-xylene, and then coupled with 4-halogenated o-xylene to obtain 2,3,3',4'-tetramethylbiphenyl. Finally, it is oxidized and dehydrated to form an anhydride to obtain 2,3,3',4'-biphenyltetracarboxylic dianhydride [CN116478114A].

[0013] Although this method has high selectivity for coupling reaction and high purity of target product, it still has the following shortcomings: (1) It still requires the use of expensive catalytic system, resulting in high production cost; (2) The lithiation reaction conditions are harsh and the safety is low, making it unsuitable for large-scale industrial production. Summary of the Invention

[0014] The purpose of this invention is to solve the above-mentioned problems and provide a method for synthesizing 2,3,3',4'-biphenyltetracarboxylic dianhydride that not only has high selectivity in the coupling reaction, resulting in high purity of the target product, but also has a low-cost catalytic system, resulting in low production cost.

[0015] The technical solution for achieving the objective of this invention is: a method for synthesizing 2,3,3',4'-biphenyltetracarboxylic dianhydride, characterized in that: 2,3-dimethylaniline is used as the starting material, firstly, 2,3-dimethylaniline diazonium salt is obtained through a diazotization reaction, then, under cuprous chloride catalysis, it is coupled with o-xylene to obtain 2,3,3',4'-tetramethylbiphenyl, and finally, 2,3,3',4'-biphenyltetracarboxylic dianhydride is obtained through an oxidation reaction and dehydration to form anhydride.

[0016] The synthesis route is as follows:

[0017] .

[0018] The 2,3-dimethylaniline diazonium salt is preferably a hydrochloride salt.

[0019] The diazotization reaction is carried out at a temperature of -10 to 10°C.

[0020] The coupling reaction is carried out in the presence of an organic solvent, which is acetone or butanone.

[0021] The initiation temperature of the coupling reaction is 45–56°C, and the reaction temperature after initiation is 15–35°C.

[0022] The oxidation reaction is a conventional method in the art, such as the pyridine-potassium permanganate method, the catalyst-oxygen method, the nitric acid method, etc.

[0023] The dehydration to anhydride formation is a conventional method in the art, such as heating acetic anhydride to form anhydride, solvent-free high-temperature dehydration to form anhydride, and xylene reflux dehydration to form anhydride.

[0024] The positive effects of this invention are as follows: (1) The coupling reaction in the synthesis method of this invention has good selectivity. It will only generate the intermediates 2,3,3',4'-tetramethylbiphenyl and 2,2,3',3'-tetramethylbiphenyl, which are scarce and expensive in the market. It will not generate the intermediate 3,3,4',4'-tetramethylbiphenyl, which has a relatively low added value to s-BPDA. In particular, 2,3,3',4'-tetramethylbiphenyl and 2,2,3',3'-tetramethylbiphenyl can be effectively separated by distillation, while 3,3,4',4'-tetramethylbiphenyl is difficult to separate from 2,3,3',4'-tetramethylbiphenyl by distillation. Thus, 2,3,3',4'-tetramethylbiphenyl with high purity can be obtained, and finally, 2,3,3',4'-tetramethylbiphenyl with high purity can be obtained. (2) The coupling reaction in the synthesis method of the present invention only requires the use of inexpensive cuprous chloride as a catalyst, which greatly reduces the production cost compared with the expensive catalytic system of the prior art, and is more suitable for large-scale industrial production. Attached Figure Description

[0025] Figure 1The image shows the HPLC spectrum of 2,3,3',4'-tetramethylbiphenyl obtained in Example 1.

[0026] Figure 2 The image shows the EI-MS spectrum of 2,3,3',4'-biphenyltetracarboxylic acid prepared in Example 1.

[0027] Figure 3 The image shows the ESI-MS spectrum of 2,3,3',4'-biphenyltetracarboxylic dianhydride prepared in Example 1 after preparation with methanol. Detailed Implementation

[0028] (Example 1)

[0029] The method for synthesizing 2,3,3',4'-biphenyltetracarboxylic dianhydride in this embodiment includes the following steps:

[0030] S1, diazotization reaction.

[0031] S11. Add 40.7g of sodium nitrite (0.59mol) to 72g of water, stir to dissolve, and obtain an aqueous solution of sodium nitrite for later use.

[0032] S12. Add 69.1g of 2,3-dimethylaniline (0.57mol) and 200g of water to a reaction flask, and add 130.5g of 36wt% concentrated hydrochloric acid while controlling the temperature at 0-30℃. After the addition is complete, stir to dissolve and obtain 2,3-dimethylaniline hydrochloride.

[0033] S13. Cool to -5 to 0℃, add the sodium nitrite aqueous solution obtained in step S11 dropwise (complete the dropwise addition in 30 to 60 minutes), stir the reaction for 30 minutes after the dropwise addition is complete, then slowly add 120 mL of acetone, stir to crystallize, filter, wash the filter cake with a small amount of acetone to obtain 103 g of wet 2,3-dimethylaniline diazonium hydrochloride, which is directly added to the next step of the reaction.

[0034] S2, coupling reaction.

[0035] S21. Add 200 mL of o-xylene (1.66 mol), 100 mL of acetone and 3 g of cuprous chloride to the reaction flask, heat to 50 °C, and then add 10 g of the wet product of 2,3-dimethylaniline diazonium hydrochloride obtained in step ①. Stir until a large number of bubbles overflow, and the reaction starts.

[0036] S22. Cool to 20-30℃, add the remaining 93g of wet 2,3-dimethylaniline diazonium hydrochloride in batches (add in 4 batches, about 40 minutes each time), and keep warm and stir until the reaction is complete.

[0037] S23. Heat to 30-40℃, concentrate under reduced pressure to recover acetone, add 100mL of water to the residue, stir, separate into layers, and wash the organic layer once with 50mL of water.

[0038] S24. The organic layer is first distilled under reduced pressure (bottom temperature 80℃, vacuum degree -0.95MPa) to remove the organic solvent. The distillation residue is then subjected to rectification (bottom temperature 230℃, vacuum degree -0.98MPa). The fractions at 265-270℃ yield 25.8g of 2,2,3',3'-tetramethylbiphenyl, and the fractions at 285-290℃ yield 77.3g of 2,3,3',4'-tetramethylbiphenyl.

[0039] The HPLC spectrum of the 2,3,3',4'-tetramethylbiphenyl obtained in this embodiment is shown in the figure below. Figure 1 ,Depend on Figure 1 As can be seen, its purity is as high as 99.2%.

[0040] S3, oxidation reaction.

[0041] S31. Add 300 mL of glacial acetic acid to the reaction flask, and while stirring, add 60 g of 2,3,3',4'-tetramethylbiphenyl obtained in step S2, 1.6 g of cobalt acetate tetrahydrate, 1.1 g of manganese acetate, and 3.2 g of sodium bromide in sequence. Heat to 100-120°C and introduce oxygen to react.

[0042] S32. After the reaction was completed, the mixture was cooled, filtered, and concentrated under reduced pressure to recover the solvent. 56 mL of water was added, followed by 30 wt% sodium hydroxide aqueous solution to adjust the pH to 9. 2.5 g of activated carbon was added, and the mixture was heated to 80-90 °C. The mixture was stirred and decolorized for 30 min, filtered, and the pH was adjusted to 1-1.5 with 30 wt% hydrochloric acid. The mixture was cooled to crystallize, filtered, and dried to obtain 85.5 g of white solid 2,3,3',4'-biphenyltetracarboxylic acid. The yield was 90.8%, and the purity was 99.2%.

[0043] The EI-MS spectrum of the intermediate obtained in this embodiment is shown below. Figure 2 ,Depend on Figure 2 It can be seen that the molecular weight of this intermediate is 330 (M-1), which is consistent with 2,3,3',4'-biphenyltetracarboxylic acid.

[0044] S4, anhydride formation reaction.

[0045] 160 mL of toluene, 180 mL of acetic anhydride, and 80 g of 2,3,3',4'-biphenyltetracarboxylic acid prepared in step S3 were added to a reaction flask. The mixture was heated to 105–110 °C and reacted until complete. After cooling, the mixture was filtered and dried to obtain 67.8 g of a white solid, 2,3,3',4'-biphenyltetracarboxylic acid dianhydride, with a yield of 95.2%, a purity of 99.6%, and a melting point of 196.5–197.5 °C.

[0046] The ESI-MS spectrum of the target product obtained in this embodiment after methanol preparation is shown below. Figure 3 ,Depend on Figure 3 It can be seen that the molecular weight of the target product is 294 (M-1), which is consistent with that of 2,3,3',4'-biphenyltetracarboxylic dianhydride.

[0047] (Example 2)

[0048] The method for synthesizing 2,3,3',4'-biphenyltetracarboxylic dianhydride in this embodiment includes the following steps:

[0049] S1, diazotization reaction.

[0050] S11. Add 203.5g of sodium nitrite (2.95mol) to 360g of water, stir to dissolve, and obtain an aqueous solution of sodium nitrite for later use.

[0051] S12. Add 345.5g of 2,3-dimethylaniline (2.85mol) and 1000g of water to a reaction flask, and add 652.5g of 36wt% concentrated hydrochloric acid while controlling the temperature at 0-30℃. After the addition is complete, stir to dissolve and obtain 2,3-dimethylaniline hydrochloride.

[0052] S13. Cool to -5 to 0℃, add the sodium nitrite aqueous solution obtained in step S11 dropwise (complete the dropwise addition in 30 to 60 minutes), stir the reaction for 30 minutes after the dropwise addition is complete, then slowly add 580 mL of acetone, stir to crystallize, filter, wash the filter cake with a small amount of acetone to obtain 515 g of wet 2,3-dimethylaniline diazonium hydrochloride, which is directly added to the next step of the reaction.

[0053] S2, coupling reaction.

[0054] S21. Add 1000 mL of o-xylene (8.3 mol), 500 mL of acetone and 15 g of cuprous chloride to the reaction flask, heat to 50 °C, and then add 50 g of the wet product of 2,3-dimethylaniline diazonium salt obtained in step ①. Stir until a large number of bubbles overflow, and the reaction starts.

[0055] S22. Cool to 20-30℃, add the remaining 565g of wet 2,3-dimethylaniline diazonium hydrochloride in batches (add in 6 batches, about 60 minutes each time), and keep warm and stir until the reaction is complete.

[0056] S23. Heat to 30-40℃, concentrate under reduced pressure to recover acetone, add 500mL of water to the residue, stir, separate into layers, and wash the organic layer once with 250mL of water.

[0057] S24. The organic layer is first distilled under reduced pressure (bottom temperature 80℃, vacuum degree -0.95MPa) to remove the organic solvent. The distillation residue is then subjected to rectification (bottom temperature 230℃, vacuum degree -0.98MPa). The fractions at 265-270℃ yield 130.2g of 2,2,3',3'-tetramethylbiphenyl (purity 98.9%), and the fractions at 285-290℃ yield 387.3g of 2,3,3',4'-tetramethylbiphenyl (purity 99.3%).

[0058] S3, oxidation reaction.

[0059] S31. Add 1500 mL of glacial acetic acid to the reaction flask, and while stirring, add 300 g of 2,3,3',4'-tetramethylbiphenyl obtained in step S2, 8 g of cobalt acetate tetrahydrate, 5.5 g of manganese acetate, and 16 g of sodium bromide in sequence. Heat to 100-120°C and introduce oxygen to react.

[0060] S32. After the reaction was completed, the mixture was cooled, filtered, and concentrated under reduced pressure to recover the solvent. 280 mL of water was added, followed by 30 wt% sodium hydroxide aqueous solution to adjust the pH to 9. 12.5 g of activated carbon was added, and the mixture was heated to 80-90 °C. The mixture was stirred and decolorized for 30 min, filtered, and the pH was adjusted to 1-1.5 with 30 wt% hydrochloric acid. The mixture was cooled to crystallize, filtered, and dried to obtain 428.2 g of white solid 2,3,3',4'-biphenyltetracarboxylic acid. The yield was 90.9% and the purity was 99.3%.

[0061] ④ Anhydride formation reaction.

[0062] 400 g of 2,3,3',4'-biphenyltetracarboxylic acid obtained in step S3 was added to the reaction flask. The mixture was heated to 210-220 °C under nitrogen purging and reacted for 2 h. After cooling, the mixture was discharged to obtain 340.8 g of off-white solid 2,3,3',4'-biphenyltetracarboxylic acid dianhydride, with a yield of 95.6%, a purity of 99.0%, and a melting point of 196.2-197.2 °C.

[0063] (Example 3)

[0064] The method for synthesizing 2,3,3',4'-biphenyltetracarboxylic dianhydride in this embodiment includes the following steps:

[0065] S1, diazotization reaction.

[0066] S11. Add 42.6g sodium nitrite (0.62mol) and 135mL water to a reaction flask, stir to dissolve, then cool to 0℃, and add a mixture of 14.9mL concentrated sulfuric acid, 59.8mL isoamyl alcohol and 37.5mL water dropwise at 0-5℃ (to be completed in about 90min). After the addition is complete, keep the reaction at this temperature for 45min. After the reaction is complete, separate the layers, wash the organic layer with ice water (50mL×2) to obtain an isoamyl nitrite solution, and store it for later use.

[0067] S12. Add 69.1 g of 2,3-dimethylaniline (0.57 mol) and 200 mL of ethanol to a reaction flask, and add 145 mL of 4 mol / L hydrogen chloride ethanol solution while controlling the temperature at 0-30℃. After the addition is complete, stir to dissolve and obtain 2,3-dimethylaniline hydrochloride.

[0068] S13. Cool to -5 to 0℃, add the isoamyl nitrite solution obtained in step S11 dropwise (complete the dropwise addition in 30 to 60 minutes), stir the reaction for 30 minutes after the dropwise addition is complete, then slowly add 100 mL of petroleum ether, stir to crystallize, filter, wash the filter cake with a small amount of petroleum ether to obtain 105 g of wet 2,3-dimethylaniline diazonium hydrochloride, which is directly added to the next reaction step.

[0069] S2, coupling reaction.

[0070] S21. Add 210 mL of o-xylene (1.74 mol), 100 mL of acetone and 3.1 g of cuprous chloride to the reaction flask, heat to 50 °C, and then add 10 g of the wet product of 2,3-dimethylaniline diazonium hydrochloride obtained in step ①. Stir until a large number of bubbles overflow, and the reaction starts.

[0071] S22. Cool to 20-30℃, add the remaining 95g of wet 2,3-dimethylaniline diazonium hydrochloride in batches (add in 4 batches, about 40 minutes each time), and keep warm and stir until the reaction is complete.

[0072] S23. Heat to 30-40℃, concentrate under reduced pressure to recover acetone, add 100mL of water to the residue, stir, separate into layers, and wash the organic layer once with 50mL of water.

[0073] S24. The organic layer is first distilled under reduced pressure (bottom temperature 80℃, vacuum degree -0.95MPa) to remove the organic solvent. The distillation residue is then subjected to rectification (bottom temperature 230℃, vacuum degree -0.98MPa). The fractions at 265-270℃ yield 26.2g of 2,2,3',3'-tetramethylbiphenyl (purity 98.6%), and the fractions at 285-290℃ yield 78.3g of 2,3,3',4'-tetramethylbiphenyl (purity 99.3%).

[0074] S3, oxidation reaction.

[0075] S31. Add 320 mL of glacial acetic acid to the reaction flask, and while stirring, add 60 g of 2,3,3',4'-tetramethylbiphenyl obtained in step S2, 1.5 g of cobalt acetate tetrahydrate, 1.0 g of manganese acetate, and 3.2 g of sodium bromide in sequence. Heat to 100-120°C and introduce oxygen to react.

[0076] S32. After the reaction was completed, the mixture was cooled, filtered, and concentrated under reduced pressure to recover the solvent. 58 mL of water was added, followed by 30 wt% sodium hydroxide aqueous solution to adjust the pH to 9. 2.5 g of activated carbon was added, and the mixture was heated to 80-90 °C. The mixture was stirred and decolorized for 30 min, filtered, and the pH was adjusted to 1-1.5 with 30 wt% hydrochloric acid. The mixture was cooled to crystallize, filtered, and dried to obtain 85.8 g of white solid 2,3,3',4'-biphenyltetracarboxylic acid. The yield was 91.1%, and the purity was 99.3%.

[0077] ④ Anhydride formation reaction.

[0078] 150 mL of toluene, 170 mL of acetic anhydride, and 80 g of 2,3,3',4'-biphenyltetracarboxylic acid prepared in step S3 were added to a reaction flask. The mixture was heated to 105–110 °C and reacted until complete. After cooling, the mixture was filtered and dried to obtain 68.0 g of a white solid, 2,3,3',4'-biphenyltetracarboxylic acid dianhydride, with a yield of 95.4%, a purity of 99.5%, and a melting point of 196.4–197.5 °C.

[0079] (Example 4)

[0080] The method for synthesizing 2,3,3',4'-biphenyltetracarboxylic dianhydride in this embodiment includes the following steps:

[0081] S1, diazotization reaction, same as in Example 1.

[0082] S2, Coupling reaction, same as in Example 1.

[0083] S3, oxidation reaction.

[0084] 436 g of potassium permanganate (2.8 mol) and 500 mL of pyridine were added to a reaction flask, followed by 60 g (0.285 mol) of 2,3,3',4'-tetramethylbiphenyl obtained in step S2. The mixture was heated under reflux for 20 h, filtered, concentrated, and the concentrated residue was added to 150 g of water. The pH was adjusted to 2-3 with 2 mol / L hydrochloric acid, filtered, washed with water, and dried to obtain 83.7 g of white solid 2,3,3',4'-biphenyltetracarboxylic acid, with a yield of 88.9% and a purity of 99.1%.

[0085] ④ Anhydride formation reaction.

[0086] 170 mL of toluene, 180 mL of acetic anhydride, and 80 g of 2,3,3',4'-biphenyltetracarboxylic acid prepared in step S3 were added to a reaction flask. The mixture was heated to 100–110 °C until the reaction was complete. After cooling, the mixture was filtered and dried to obtain 67.8 g of a white solid, 2,3,3',4'-biphenyltetracarboxylic acid dianhydride, with a yield of 95.1%, a purity of 99.7%, and a melting point of 196.5–197.6 °C.

Claims

1. A method for synthesizing 2,3,3',4'-biphenyltetracarboxylic dianhydride, characterized by: 2,3-dimethylaniline as starting material, first by diazotization reaction to obtain 2,3-dimethylaniline diazonium salt, then in the presence of cuprous chloride catalyst, with o-xylene by coupling reaction to obtain 2,3,3',4'-tetramethyl biphenyl, finally by oxidation reaction, dehydration to anhydride to obtain 2,3,3',4'-biphenyl tetra carboxylic dianhydride.

2. The method for synthesizing 2,3,3',4'-biphenyltetracarboxylic dianhydride according to claim 1, characterized in that: The 2,3-dimethylaniline diazonium salt is 2,3-dimethylaniline diazonium hydrochloride.

3. The method for synthesizing 2,3,3',4'-biphenyltetracarboxylic dianhydride according to claim 1, characterized in that: The diazotization reaction is at a temperature of -10-10℃.

4. The method for synthesizing 2,3,3',4'-biphenyltetracarboxylic dianhydride according to claim 1, characterized in that: The coupling reaction is carried out in the presence of an organic solvent; the organic solvent is acetone or butanone.

5. The method for synthesizing 2,3,3',4'-biphenyltetracarboxylic dianhydride according to claim 1, characterized in that: The starting temperature of the coupling reaction is 45-56℃, and the reaction temperature after starting is 15-35℃.

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