4-bromophthalic anhydride and a method for its synthesis

Abstract

The application relates to a 4-bromophthalic anhydride and a synthesis method thereof, and the synthesis method of the 4-bromophthalic anhydride comprises the following steps: after furan and maleic anhydride are mixed in a first solvent, a diene synthesis reaction is carried out to generate a first intermediate; after the first intermediate and bromine are mixed in a second solvent, an addition reaction is carried out to generate a second intermediate; after the second intermediate, acetic anhydride and an acidic catalyst are mixed, a catalytic reaction is carried out to generate a third intermediate; and after the third intermediate and tertiary amine are mixed, a chemical reaction is carried out to generate 4-bromoaniline. The synthesis method can improve the yield and purity of the 4-bromophthalic anhydride.

Description

Technical Field

[0001] This application relates to the field of organic synthesis technology, and more specifically, to 4-bromophthalic anhydride and its synthesis methods. Background Technology

[0002] 4-Bromophthalic anhydride is an important chemical raw material. The preparation of 4-bromophthalic anhydride may require harsh reaction conditions, resulting in a low conversion rate. On the other hand, it may produce a large number of side reactions, leading to low purity. Summary of the Invention

[0003] This application provides a method for synthesizing 4-bromophthalic anhydride, which can improve the yield and purity of 4-bromophthalic anhydride.

[0004] Firstly, this application proposes a method for synthesizing 4-bromophthalic anhydride, the method comprising: In step S100, furan and maleic anhydride are added to the first solvent and mixed, and then the first intermediate is generated by a diene synthesis reaction. Step S200: The first intermediate and bromine are added to the second solvent and mixed, and then an addition reaction is carried out to generate the second intermediate; In step S300, the second intermediate, acetic anhydride, and acidic catalyst are mixed and then subjected to a catalytic reaction to generate the third intermediate. In step S400, the third intermediate and the tertiary amine are mixed and then reacted chemically to produce 4-bromophthalic anhydride.

[0005] In some embodiments, step S100 satisfies at least one of the following conditions: (1) The reaction temperature for the diene synthesis reaction is 20°C to 30°C; and / or (2) The reaction time for the diene synthesis reaction is 24 to 48 hours; (3) The first solvent includes at least one of diethyl ether, methyl tert-butyl ether, tetrahydrofuran, 2-methyltetrahydrofuran, ethylene glycol dimethyl ether, ethylene glycol diethyl ether, and furan; (4) The ratio of the amount of furan to the amount of maleic anhydride is 1.5 to 3.0.

[0006] In some embodiments, step S200 satisfies at least one of the following conditions: (1) The reaction temperature for the addition reaction is 20℃ to 50℃; (2) The reaction time for the addition reaction is 2 to 8 hours; (3) The second solvent includes at least one of 2-methyltetrahydrofuran, ethylene glycol dimethyl ether, and ethylene glycol diethyl ether.

[0007] In some embodiments, the ratio of the amount of bromine in step S200 to the amount of maleic anhydride in step S100 is 1.02 to 1.05.

[0008] In some embodiments, step S300 satisfies at least one of the following conditions. (1) The reaction temperature of the catalytic reaction is 20℃ to 50℃; (2) The reaction time of the catalytic reaction is greater than 0 hours and less than 12 hours; (3) The acid catalyst includes at least one of sulfuric acid, methanesulfonic acid, and p-toluenesulfonic acid.

[0009] In some embodiments, the ratio of the amount of acidic catalyst in step S300 to the amount of maleic anhydride in step S100 is 0.01 to 0.05; and / or The ratio of the amount of acetic anhydride in step S300 to the amount of maleic anhydride in step S100 is 1.1 to 1.5.

[0010] In some embodiments, step S400 satisfies at least one of the following conditions. (1) The reaction temperature of the chemical reaction is 50℃ to 70℃; (2) The reaction time of the chemical reaction is 6 to 12 hours; (4) Tertiary amines include at least one of triethylamine, pyridine, 2-methylpyridine, N,N-diisopropylethylamine and N,N-dimethylaniline.

[0011] In some embodiments, the tertiary amine includes at least one of N,N-diisopropylethylamine and N,N-dimethylaniline.

[0012] In some embodiments, the ratio of the amount of tertiary amine in step S400 to the amount of maleic anhydride in step S100 is 3.3 to 4.0.

[0013] Secondly, this application provides a 4-bromophthalic anhydride prepared by the synthesis method of any embodiment of the first aspect of this application.

[0014] The method provided in the embodiments of this application can improve the yield and purity of 4-bromophthalic anhydride. Specifically, firstly, it is superior to existing methods in terms of yield, cost, and product purification difficulty. The conversion rates of the chemical reactions corresponding to the four steps in this application are all high, and the yield of the crude 4-bromophthalic anhydride can reach over 87%, and the purity can reach over 98%. Secondly, the impurities in the crude 4-bromophthalic anhydride obtained in this application are mainly intermediate products containing epoxy groups remaining from the first two steps, as well as trace amounts of tertiary amine salts. The solubility of these impurities in various organic solvents is much higher than that of 4-bromophthalic anhydride. The purity of the crude product can be further improved to over 99.5% by using a suitable organic solvent for further crystallization or washing. Furthermore, steps S200, S300, and S400 in this application can be carried out in a one-pot process; even the chemical reactions in steps S300 and S400 can be carried out simultaneously. These features simplify the operation of the entire preparation process and optimize the costs of raw materials, equipment, time, and energy consumption. Detailed Implementation

[0015] Among related technologies, the conversion rate and purity of the synthesis of 4-bromophthalic anhydride are relatively low.

[0016] For example, 4-bromophthalic anhydride is obtained by brominating phthalic anhydride via the following synthetic route: , The above synthetic route has the following drawbacks: Phthalic anhydride contains two carbonyl groups on its benzene ring, which severely passivates the benzene ring. Therefore, a high reaction temperature (far exceeding the boiling point of bromine) and a long reaction time are required to achieve a high conversion rate during the bromination reaction.

[0017] To prevent bromine from volatilizing during prolonged reactions, a pressure-resistant, sealed device is required. This device must also withstand corrosion from bromine and hydrogen bromide at high temperatures for extended periods. Therefore, this method places stringent requirements on the equipment materials; repeated use results in significant equipment wear and tear. Furthermore, this method is difficult to achieve complete conversion, and the residual raw material (phthalic anhydride) is similar in properties to the product 4-bromophthalic anhydride, making separation challenging; the purification of 4-bromophthalic anhydride also results in substantial losses.

[0018] For example, bromination of o-xylene yields 4-bromo-o-xylene, which is then oxidized to 4-bromophthalic acid, and subsequently 4-bromophthalic anhydride is prepared. The synthetic route is as follows: , The above synthetic route has the following drawbacks: In the first step of the bromination reaction, in addition to obtaining the target product 4-bromo-o-xylene, byproducts such as 3-bromo-o-xylene, 3,4-dibromo-o-xylene, 3,5-dibromo-o-xylene, and 4,5-dibromo-o-xylene are also produced simultaneously, with the total content of these byproducts exceeding 15%; the residual amount of incompletely converted raw material (o-xylene) is also above 5%. Moreover, these substances have similar physicochemical properties and are difficult to separate; resulting in a yield of 4-bromo-o-xylene after purification not exceeding 60%; and an overall process yield not exceeding 40%.

[0019] In view of the above problems, this application proposes a method for synthesizing 4-bromophthalic anhydride. This method uses inexpensive and readily available furan and maleic anhydride as starting materials, and the reaction conditions are easy to implement industrially. The yield of the crude 4-bromophthalic anhydride obtained can reach more than 87%, and the purity can reach more than 98%. The cost is significantly lower than the two existing methods. The crude product obtained does not contain impurities that are difficult to remove, and it is easy to purify to obtain 4-bromophthalic anhydride with higher purity.

[0020] The method for synthesizing 4-bromophthalic anhydride in this application includes: In step S100, furan and maleic anhydride are mixed and then subjected to a diene synthesis reaction to generate the first intermediate. Step S200: The first intermediate is mixed with bromine and then subjected to an addition reaction to generate the second intermediate; In step S300, the second intermediate, acetic anhydride, and acidic catalyst are mixed and then subjected to a catalytic reaction to generate the third intermediate. In step S400, the third intermediate and the tertiary amine are mixed and then reacted chemically to produce 4-bromophthalic anhydride.

[0021] Although the synthesis method of this application includes the above four steps, steps S200, S300 and S400 can be completed in a one-pot process.

[0022] [Step S100] In step S100, furan is used to react with maleic anhydride to undergo a diene synthesis reaction to obtain a first intermediate, which is 4,10-dioxatricyclo[5.2.1.0(2,6)]dec-8-en-3,5-dione (hereinafter referred to as compound 1A).

[0023] The reaction mechanism is as follows: .

[0024] Specifically, a certain amount of maleic anhydride, furan, and a first solvent are added to the reaction vessel. Under nitrogen protection, the mixture is kept at 20°C to 30°C and stirred for 10 to 24 hours. Then, while slowly increasing the temperature, the mixture is first distilled at atmospheric pressure and then concentrated under reduced pressure to remove the solvent and excess furan from the reaction solution. Finally, the temperature is controlled at 70°C to 80°C and the vacuum degree at 2 kPa to 4 kPa until no more liquid is distilled off. The concentrated residue is the crude product of compound 1A; after cooling to near room temperature under nitrogen protection, the concentrated residue can be directly used in the next step.

[0025] In some embodiments, when furan is not used as a solvent, the molar ratio of furan to maleic anhydride is 1.5 to 3.0. Of course, furan can also be used as a solvent, and when used as a solvent, furan can also simultaneously be used as a reactant.

[0026] In some embodiments, the first solvent may include at least one of diethyl ether, methyl tert-butyl ether, tetrahydrofuran, 2-methyltetrahydrofuran, ethylene glycol dimethyl ether, ethylene glycol diethyl ether, and furan.

[0027] In some embodiments, the amount of the first solvent is not strictly required, as long as it is sufficient to completely dissolve maleic anhydride between 20°C and 30°C.

[0028] In some embodiments, the reaction temperature of step S100 is 20°C to 30°C.

[0029] In some embodiments, the temperature of the heat preservation reaction is 20°C to 30°C.

[0030] In some embodiments, the heat treatment reaction time is 24 to 48 hours.

[0031] [Step S200] In step S200, the first intermediate is mixed with bromine and then subjected to an addition reaction to generate a second intermediate, which is a dibromo compound (hereinafter referred to as compound 2A).

[0032] The reaction mechanism is as follows: .

[0033] Specifically, the crude product of compound 1A obtained in step S100 and the second solvent are added to the reaction vessel. While stirring and controlling the liquid temperature between 20°C and 50°C, bromine is slowly added dropwise. After the addition is complete, the temperature is maintained between 20°C and 50°C, and the mixture is stirred for 2 to 8 hours. The resulting reaction solution can be used directly in the next step without further treatment.

[0034] In some embodiments, the second solvent may include at least one of 2-methyltetrahydrofuran, ethylene glycol dimethyl ether, and ethylene glycol diethyl ether.

[0035] In some embodiments, the mass ratio of the second solvent to the first intermediate (crude compound 1A) is 8 to 20.

[0036] In some embodiments, the ratio of the amount of bromine to the amount of maleic anhydride in step S100 is 1.02 to 1.05.

[0037] In some embodiments, the temperature during the addition of bromine and during the subsequent stirring and heat preservation is maintained between 20°C and 50°C, i.e., step S200 is completed at 20°C to 50°C.

[0038] In some embodiments, the dropping rate of bromine is not strictly required, as long as the liquid temperature is maintained between 20°C and 50°C.

[0039] In some embodiments, the incubation and stirring time after the bromine addition is completed is 2 to 8 hours.

[0040] [Step S300] In step S300, the second intermediate, acetic anhydride and acidic catalyst are mixed and then subjected to a catalytic reaction to generate the third intermediate (hereinafter referred to as compound 3A).

[0041] The reaction mechanism is as follows: .

[0042] Specifically, after the reaction in step S200 is completed, an acidic catalyst is first added to the reaction solution at a temperature of 20°C to 50°C; then, acetic anhydride is added dropwise while maintaining the temperature at 20°C to 50°C. After the addition is complete, the reaction is maintained at 20°C to 50°C for 0-12 hours. The resulting reaction solution requires no further treatment and can be used directly in the next step.

[0043] In some embodiments, the acidic catalyst may include at least one of sulfuric acid, methanesulfonic acid, and p-toluenesulfonic acid.

[0044] In some embodiments, the ratio of the amount of acidic catalyst to the amount of maleic anhydride in step S100 is 0.01 to 0.05.

[0045] In some embodiments, the ratio of the amount of acetic anhydride to the amount of maleic anhydride in step S100 is 1.1 to 1.5.

[0046] In some embodiments, the reaction temperature of step S300 is 20°C to 50°C.

[0047] In some embodiments, the temperature during the addition of the acidic catalyst and the dropwise addition of acetic anhydride can be controlled between 20°C and 50°C.

[0048] In some embodiments, there are no strict requirements on the rate of acetic anhydride addition, as long as the liquid temperature can be maintained between 20°C and 50°C.

[0049] In some embodiments, after the addition of acetic anhydride is completed, the temperature during the reaction is kept at 20-50°C for a period of more than 0 hours and less than 12 hours.

[0050] [Step S400] In step S400, the third intermediate (compound 3A) and the tertiary amine are mixed and then reacted chemically to generate 4-bromophthalic anhydride.

[0051] The reaction mechanism is as follows: .

[0052] Specifically, the reaction solution containing compound 3A is treated with a tertiary amine to generate the target product, 4-bromophthalic anhydride, as well as byproducts such as the acetate and hydrogen bromide salts of the tertiary amine. After filtration, washing, and concentration to remove the solvent and byproducts, crude 4-bromophthalic anhydride with a purity of over 98% is obtained.

[0053] After the reaction in step S300 is complete, the reaction solution is kept at a temperature between 50°C and 70°C and stirred while adding a tertiary amine dropwise. After the addition is complete, the reaction solution is kept at a temperature between 50°C and 70°C and stirred for 6 to 12 hours. Then, the reaction solution is kept at a temperature between 50°C and 70°C and filtered while hot. The filter cake is washed with a second solvent at a mass ratio of 2-4 times the wet weight of the filter cake and heated to 50°C to 70°C.

[0054] The washed filter cake is a mixture mainly composed of tertiary amine acetate and tertiary amine hydrogen bromide, which can be used to recover tertiary amines.

[0055] After combining the washing liquid and filtrate, the temperature is controlled at 50℃ to 70℃, and the second solvent is evaporated by vacuum concentration. After concentration until a large amount of crystallization begins to appear in the residue, heating and vacuum are stopped, and cooling crystallization under nitrogen protection is carried out until the liquid temperature reaches -10℃ to -15℃. The filter cake obtained from the cooling crystallization is the crude (wet) product of 4-bromophthalic anhydride.

[0056] In some embodiments, the tertiary amine may include at least one of triethylamine, pyridine, 2-methylpyridine, N,N-diisopropylethylamine, and N,N-dimethylaniline; optionally, the tertiary amine may include at least one of N,N-diisopropylethylamine and N,N-dimethylaniline.

[0057] In some embodiments, the ratio of the amount of tertiary amine to the amount of maleic anhydride in step S100 is 3.3 to 4.0.

[0058] In some embodiments, the reaction temperature of step S400 is 50°C to 70°C.

[0059] In some embodiments, the temperature during the addition of the tertiary amine is 50°C to 70°C.

[0060] In some embodiments, there are no strict requirements on the rate of addition of tertiary amine, as long as the liquid temperature can be maintained between 50°C and 70°C.

[0061] In some embodiments, after the addition of the tertiary amine is completed, the temperature during the reaction is kept between 50°C and 70°C for 6 to 12 hours.

[0062] In some embodiments, the amount of the second solvent used when washing the filter cake may be 2-4 times the mass ratio of the filter cake (wet weight).

[0063] In some embodiments, the temperature of the reaction solution during filtration and washing of the filter cake is between 50°C and 70°C, and the washing time is between 15 and 30 minutes.

[0064] In some embodiments, the temperature at which the mixture of filtrate and washing liquid is concentrated under reduced pressure is between 50°C and 70°C.

[0065] In some embodiments, the final temperature for cooling and crystallizing the concentrated residue is -10°C to -15°C.

[0066] By adjusting the parameters as described above, this application can further improve the purity and yield of the product.

[0067] According to the synthesis method of the embodiments of this application, the first intermediate (compound 1A) is prepared in step S100, and the target product is prepared in steps S200, S300 and S400. This is the innovative design of this application.

[0068] Specifically, in step S300, the ring-opening and elimination reaction from the second intermediate (compound 2A) to prepare the third intermediate (compound 3A) requires a strongly acidic catalyst; while in step S400, the elimination reaction from the third intermediate (compound 3A) to prepare 4-bromophthalic anhydride requires a basic acid-binding agent. The conditions required for these two reactions are contradictory; normally, these two reactions need to be carried out step-by-step. However, this application, by optimizing the above-mentioned reaction solvents and raw materials, enables the continuous one-pot reaction of these two reactions; it can even allow the two reactions to proceed simultaneously, simplifying the entire process and shortening the overall reaction time and energy consumption.

[0069] In the initial stage of the reaction, this application utilizes an acidic catalyst to initiate the conversion of the second intermediate (compound 2A) into the third intermediate (compound 3A). In the later stages of the reaction, this application uses an ether solvent as the reaction solvent, and preferably uses a tertiary amine with a large lipophilic group (such as at least one of N,N-diisopropylethylamine and N,N-dimethylaniline) as an acid-binding agent. When the tertiary amine is added, the acidic catalyst reacts with the tertiary amine to form the corresponding tertiary amine salt; simultaneously, a significant amount of tertiary amine hydrogen bromide salts are also produced as byproducts. Since these two tertiary amine salts still possess strong acidity, and the preferred tertiary amines have large lipophilic groups, these two salts also have a certain solubility in the ether solvent; therefore, the reaction from the second intermediate (compound 2A) to the third intermediate (compound 3A) can continue to catalyze the reaction. At this point, the two reactions corresponding to steps S300 and S400 in this application can be carried out simultaneously, and the heat preservation reaction time after the addition of acetic anhydride in step S300 can be reduced to 0 hours; thus optimizing the cost in terms of time and energy consumption.

[0070] Compared to existing technologies, First, the method for preparing 4-bromophthalic anhydride in this application is superior to existing methods in terms of yield, cost, and product purification difficulty. The conversion rates of the chemical reactions corresponding to the four steps in this application are all high, and the yield of the crude 4-bromophthalic anhydride can reach over 87%, with a purity of over 98%.

[0071] Secondly, the impurities in the crude 4-bromophthalic anhydride obtained in this application are mainly intermediate products containing epoxy groups remaining from the first two steps, as well as trace amounts of tertiary amine salts. These impurities have much higher solubility in various organic solvents than 4-bromophthalic anhydride. The purity of this crude product can be further improved to over 99.5% by using a suitable organic solvent for further crystallization or washing.

[0072] Furthermore, steps S200, S300, and S400 of this application can be carried out in a one-pot process; even the chemical reactions in steps S300 and S400 can be carried out simultaneously. These features simplify the entire preparation process and optimize costs related to raw materials, equipment, time, and energy consumption.

[0073] This application also provides a 4-bromophthalic anhydride prepared by any of the above embodiments. The 4-bromophthalic anhydride prepared by the above method contains fewer impurities and has higher purity. Example

[0074] The following describes the embodiments of this application. The embodiments described below are exemplary and are only used to explain this application, and should not be construed as limiting this application. Where specific techniques or conditions are not specified in the embodiments, they shall be performed in accordance with the techniques or conditions described in the literature in this field or according to the product instructions. Reagents or instruments whose manufacturers are not specified are all conventional products that can be obtained commercially. Example 1

[0075] Step S110: Prepare the first intermediate (compound 1A). .

[0076] Add 49.0 g (0.5 mol) of maleic anhydride, 51 g (0.75 mol) of furan, and 490 g of ethylene glycol dimethyl ether to a 1000 ml three-necked flask. Under nitrogen protection, continuously stir and heat to maintain the liquid temperature at 20-25 °C for 48 hours. Then, while slowly increasing the temperature, first distill at atmospheric pressure and then concentrate under reduced pressure to remove the ethylene glycol dimethyl ether and excess furan from the reaction solution. Finally, control the liquid temperature at 70-80 °C and the vacuum at 2-4 kPa until no liquid is distilled off. The concentrated residue is the crude product of compound 1A; the mass is approximately 93 g, with a yield ≥100%.

[0077] Step S210: Prepare the second intermediate (compound 2A). .

[0078] Add 93 g (approximately 0.5 mol) of crude compound 1A obtained in step S110 and 744 g of 2-methyltetrahydrofuran to a 5000 ml reaction flask. While stirring and controlling the liquid temperature between 40-50 °C, slowly add a total of 84 g (0.525 mol) of bromine dropwise; after the addition is complete, continue stirring at 40-50 °C for 2 hours. The resulting reaction solution requires no further treatment and can be used directly in the next step.

[0079] Step S310, Preparation of 4-bromophthalic anhydride

[0080] To the reaction solution obtained in step S210, while maintaining stirring and a temperature of 40-50°C, add 0.48 g (0.005 mol) of methanesulfonic acid; then, while maintaining the temperature at 40-50°C and stirring, slowly add a total of 56.1 g (0.55 mol) of acetic anhydride. After the addition is complete, raise the temperature and maintain it at 60-70°C, while stirring, slowly add a total of 213 g (1.65 mol) of N,N-diisopropylethylamine. After the addition is complete, maintain the temperature at 60-70°C and continue stirring for 6 hours.

[0081] The reaction solution was filtered while hot. The filter cake was washed with 2-methyltetrahydrofuran (wet weight of the filter cake) at a ratio of 2:1, heated to 60-70°C and stirred for 15 minutes, then filtered again while hot. The washing liquid was combined with the previous filtrate, and the mixture was slowly concentrated under vacuum and heating until a large amount of crystals began to appear in the concentrated residue. Heating and vacuuming were then stopped. The concentrated residue was stirred under nitrogen protection and cooled to -10 to -15°C to allow crystallization. The obtained crystals were filtered off and dried under reduced pressure to obtain 103.3 g of crude 4-bromophthalic anhydride; yield 91%, gas chromatographic purity 98.2%. Example 2

[0082] Step S120: Prepare the first intermediate (compound 1A). Add 49.0 g (0.5 mol) of maleic anhydride, 51 g (0.75 mol) of furan, and 490 g of ethylene glycol dimethyl ether to a 1000 ml three-necked flask. Under nitrogen protection, continuously stir and heat to maintain the liquid temperature at 20-25 °C for 48 hours. Then, while slowly increasing the temperature, first distill at atmospheric pressure and then concentrate under reduced pressure to remove the ethylene glycol dimethyl ether and excess furan from the reaction solution. Finally, control the liquid temperature at 70-80 °C and the vacuum at 2-4 kPa until no liquid is distilled off. The concentrated residue is the crude product of compound 1A; the mass is approximately 93 g, with a yield ≥100%.

[0083] Step S220: Prepare the second intermediate (compound 2A). Add 91 g (approximately 0.5 mol) of crude compound 1A obtained in step S120 and 1820 g of ethylene glycol dimethyl ether to a 5000 ml reaction flask. While stirring and controlling the liquid temperature between 20-30°C, slowly add a total of 81.6 g (0.51 mol) of bromine dropwise; after the addition is complete, continue stirring at 20-30°C for 8 hours. The resulting reaction solution requires no further treatment and can be used directly in the next step.

[0084] Step S320: Preparation of 4-bromophthalic anhydride Add 2.45 g (0.025 mol) of sulfuric acid to the reaction solution obtained in step S220, maintaining stirring and temperature at 20-30°C; then, while maintaining the temperature at 20-30°C, slowly add a total of 76.5 g (0.75 mol) of acetic anhydride dropwise with stirring. After the addition is complete, maintain the temperature at 20-30°C and stir for 12 hours; then, raise the temperature and maintain it at 50-60°C, slowly adding a total of 202 g (2.0 mol) of triethylamine dropwise with stirring. After the addition is complete, maintain the temperature at 50-60°C and continue stirring for 12 hours.

[0085] The reaction solution was filtered while hot. The filter cake was washed with ethylene glycol dimethyl ether at a ratio of 4 times its wet weight, heated to 50-60°C, and stirred for 30 minutes. The mixture was then filtered again while hot. The washings were combined with the previous filtrate, and the mixture was slowly concentrated under vacuum and heat until a large amount of crystals began to precipitate in the concentrated residue. Heating and vacuuming were then stopped. The concentrated residue was then crystallized under nitrogen protection by stirring and cooling to a liquid temperature of -10 to -15°C. The resulting crystals were filtered off and dried under reduced pressure to obtain 98.8 g of crude 4-bromophthalic anhydride; yield 87%, gas chromatographic purity 98.6%.

[0086] Although illustrative embodiments have been demonstrated and described, those skilled in the art should understand that the above embodiments should not be construed as limiting the present application, and that changes, substitutions and modifications can be made to the embodiments without departing from the spirit, principles and scope of the present application.

Claims

1. A method for synthesizing 4-bromophthalic anhydride, comprising: In step S100, furan and maleic anhydride are added to a first solvent and mixed, followed by a diene synthesis reaction to generate a first intermediate, which is compound 1A. The first solvent is selected from at least one of diethyl ether, methyl tert-butyl ether, tetrahydrofuran, 2-methyltetrahydrofuran, ethylene glycol dimethyl ether, ethylene glycol diethyl ether, and furan. The reaction mechanism of step S100 is as follows: ， In step S200, the first intermediate and bromine are added to a second solvent and mixed, followed by an addition reaction to generate a second intermediate, which is compound 2A. The second solvent is selected from at least one of 2-methyltetrahydrofuran, ethylene glycol dimethyl ether, and ethylene glycol diethyl ether. The reaction mechanism of step S200 is as follows: ， In step S300, the second intermediate, acetic anhydride, and acidic catalyst are mixed and then subjected to a catalytic reaction to generate a third intermediate, wherein the third intermediate is compound 3A. The reaction mechanism of step S300 is as follows: ， In step S400, the third intermediate and the tertiary amine are mixed and then reacted chemically to generate 4-bromophthalic anhydride; the tertiary amine is selected from at least one of triethylamine, pyridine, 2-methylpyridine, N,N-diisopropylethylamine, and N,N-dimethylaniline. The reaction mechanism of step S400 is as follows: ， Step S400 also satisfies the following conditions: (1) The reaction temperature of the chemical reaction is 50℃ to 70℃; (2) The reaction time of the chemical reaction is 6 to 12 hours.

2. The synthesis method according to claim 1, wherein, Step S100 satisfies at least one of the following conditions: (1) The reaction temperature of the diene synthesis reaction is 20°C to 30°C; (2) The reaction time for the diene synthesis reaction is 24 to 48 hours; (3) The ratio of the amount of furan to the amount of maleic anhydride is 1.5 to 3.

0.

3. The synthesis method according to claim 1, wherein, Step S200 satisfies at least one of the following conditions: (1) The reaction temperature of the addition reaction is 20°C to 50°C; (2) The reaction time of the addition reaction is 2 to 8 hours.

4. The synthesis method according to claim 1, wherein, The ratio of the amount of bromine in step S200 to the amount of maleic anhydride in step S100 is 1.02 to 1.

05.

5. The synthesis method according to claim 1, wherein, Step S300 satisfies at least one of the following conditions: (1) The reaction temperature of the catalytic reaction is 20℃ to 50℃; (2) The reaction time of the catalytic reaction is greater than 0 hours and less than 12 hours; (3) The acidic catalyst is selected from at least one of sulfuric acid, methanesulfonic acid, and p-toluenesulfonic acid.

6. The synthesis method according to claim 1, wherein, The ratio of the amount of acidic catalyst in step S300 to the amount of maleic anhydride in step S100 is 0.01 to 0.05; and / or The ratio of the amount of acetic anhydride in step S300 to the amount of maleic anhydride in step S100 is 1.1 to 1.

5.

7. The synthesis method according to claim 1, wherein, The tertiary amine is selected from at least one of N,N-diisopropylethylamine and N,N-dimethylaniline.

8. The synthesis method according to claim 1, wherein, The ratio of the amount of the tertiary amine in step S400 to the amount of maleic anhydride in step S100 is 3.3 to 4.0.

Images