CN118146181A

CN118146181A - 4-Bromophenic anhydride and its synthesis process

Info

Publication number: CN118146181A
Application number: CN202410261309.XA
Authority: CN
Inventors: 宋斌; 龚秦丽; 邓伟强
Original assignee: Hunan Jingshi New Material Co ltd
Current assignee: Hunan Jingshi New Material Co ltd
Priority date: 2024-03-07
Filing date: 2024-03-07
Publication date: 2024-06-07

Abstract

The application relates to 4-bromophthalic anhydride and a synthesis method thereof, and discloses a synthesis method of 4-bromophthalic anhydride, which comprises the following steps: furan and maleic anhydride are added into a first solvent for mixing, and then a first intermediate is generated through diene synthesis reaction; adding the first intermediate and bromine into a second solvent, mixing, and generating a second intermediate through addition reaction; mixing the second intermediate, acetic anhydride and an acidic catalyst, and then carrying out catalytic reaction to generate a third intermediate; and mixing the third intermediate with tertiary amine, and performing chemical reaction to obtain the 4-bromoaniline. The synthesis method can improve the yield and purity of the 4-bromophthalic anhydride.

Description

4-Bromophenic anhydride and its synthesis process

Technical Field

The application relates to the technical field of organic synthesis, in particular to 4-bromophthalic anhydride and a synthesis method thereof.

Background

4-Bromophthalic anhydride is an important chemical raw material for preparing the 4-bromophthalic anhydride, and on one hand, harsh reaction conditions may be required when the 4-bromophthalic anhydride is prepared, so that the conversion rate is lower; on the other hand, a large number of side reactions may occur, resulting in lower purity.

Disclosure of Invention

The application provides 4-bromophthalic anhydride and a synthesis method thereof, and the synthesis method can improve the yield and purity of the 4-bromophthalic anhydride.

In a first aspect, the application provides a method for synthesizing 4-bromophthalic anhydride, which comprises the following steps:

Step S100, adding furan and maleic anhydride into a first solvent, mixing, and generating a first intermediate through diene synthesis reaction;

step S200, adding the first intermediate and bromine into a second solvent, mixing, and generating a second intermediate through addition reaction;

step S300, mixing the second intermediate, acetic anhydride and an acidic catalyst, and then carrying out catalytic reaction to generate a third intermediate;

Step S400, mixing the third intermediate and tertiary amine, and performing chemical reaction to obtain the 4-bromoaniline.

In some embodiments, step S100 satisfies at least one of the following conditions,

(1) The reaction temperature of the diene synthesis reaction is 20-30 ℃; and/or

(2) The reaction time of the diene synthesis reaction is 24 hours to 48 hours;

(3) The first solvent comprises at least one of diethyl ether, methyl tertiary butyl ether, tetrahydrofuran, 2-methyltetrahydrofuran, ethylene glycol dimethyl ether, ethylene glycol diethyl ether and furan;

(4) The ratio of the amount of substance of furan to the amount of substance of maleic anhydride is 1.5 to 3.0.

In some embodiments, step S200 satisfies at least one of the following conditions,

(1) The reaction temperature of the addition reaction is 20 ℃ to 50 ℃;

(2) The reaction time of the addition reaction is 2 to 8 hours;

(3) The second solvent comprises at least one of 2-methyltetrahydrofuran, ethylene glycol dimethyl ether and ethylene glycol diethyl ether.

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

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 more than 0 hours and less than 12 hours;

(3) The acidic catalyst comprises at least one of sulfuric acid, methane sulfonic acid and p-toluene sulfonic acid.

In some embodiments, the ratio of the amount of material of the acid catalyst in step S300 to the amount of material of the maleic anhydride in step S100 is 0.01 to 0.05; and/or

The ratio of the amount of the substance of acetic anhydride in step S300 to the amount of the substance of maleic anhydride in step S100 is 1.1 to 1.5.

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 hours to 12 hours;

(4) The tertiary amine includes at least one of triethylamine, pyridine, 2-methylpyridine, N-diisopropylethylamine and N, N-dimethylaniline.

In some embodiments, the tertiary amine comprises at least one of N, N-diisopropylethylamine and N, N-dimethylaniline.

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

In a second aspect, the application provides 4-bromophthalic anhydride prepared by the synthesis method of any one of the embodiments of the first aspect of the application.

According to the method provided by the embodiment of the application, the yield and purity of the 4-bromophthalic anhydride can be improved. Specifically, firstly, the method is superior to the existing method in terms of yield, cost and product purification difficulty. The conversion rate of the chemical reaction corresponding to the four steps is high, and the yield of the finally obtained crude 4-bromophthalic anhydride can reach more than 87% and the purity can reach more than 98%. And secondly, impurities in the crude 4-bromophthalic anhydride product obtained by the application are mainly intermediate products which are remained in the first two steps and contain epoxy groups, salts of trace tertiary amine and the like. The solubility of these impurities in various organic solvents is much higher than that of 4-bromophthalic anhydride. The crude product is continuously crystallized or washed by only selecting a proper organic solvent, and the purity can be further improved to more than 99.5 percent. Furthermore, the steps S200, S300 and S400 of the present application may be performed by a one-pot method; it is even possible to synchronize the chemical reactions of step S300 and step S400. These simplify the operation of the whole preparation process and optimize the costs in terms of raw materials, equipment, time and energy consumption.

Detailed Description

In the related art, the conversion rate and purity of the synthesized 4-bromophthalic anhydride are relatively low.

For example, 4-bromophthalic anhydride is obtained from bromination of phthalic anhydride, and the synthetic route is as follows:

The above synthetic route has the following drawbacks:

The benzene ring of phthalic anhydride contains two carbonyl groups, so that the passivation of the benzene ring is serious, and when the bromination reaction is carried out, a higher reaction temperature (the boiling point of far super bromine) and a longer reaction time are required to achieve a higher conversion rate.

In order to prevent bromine from volatilizing in long-time reaction, a pressure-resistant sealing device is needed; the device is also resistant to corrosion by bromine and hydrogen bromide at high temperatures for long periods of time. Therefore, the method has strict requirements on equipment materials; the equipment loss after multiple uses is serious. In addition, the method is difficult to convert completely, and the residual raw material (phthalic anhydride) has similar properties with the product 4-bromophthalic anhydride and is difficult to separate; the loss of the 4-bromophthalic anhydride during purification is relatively large.

For another example, 4-bromo-o-xylene is obtained from o-xylene by bromination, and then 4-bromophthalic acid is obtained by reoxidation, and 4-bromophthalic anhydride is obtained by the following synthetic route:

The above synthetic route has the following drawbacks:

In the first-step bromination reaction, the target product 4-bromo-o-xylene is obtained, and by-products such as 3-bromo-o-xylene, 3, 4-dibromo-o-xylene, 3, 5-dibromo-o-xylene, 4, 5-dibromo-o-xylene and the like are also produced at the same time, wherein the total content of the by-products exceeds 15%; the residue of the raw material (o-xylene) which cannot be completely converted is also 5% or more. And the physical and chemical properties of the substances are similar, and the separation is difficult; resulting in a yield of no more than 60% after purification of 4-bromo-o-xylene; the yield of the whole process route is not higher than 40%.

In view of the above problems, the present application provides a method for synthesizing 4-bromophthalic anhydride, which uses furan and maleic anhydride which are cheap and easy to obtain as starting materials, and the reaction conditions are easy to realize industrialization; the yield of the obtained crude 4-bromophthalic anhydride can reach more than 87%, the purity can reach more than 98%, and the cost is obviously lower than that of the prior two methods; the obtained crude product does not contain impurities which are difficult to remove, and is easy to purify and obtain the 4-bromophthalic anhydride with higher purity. .

The synthesis method of the 4-bromophthalic anhydride comprises the following steps:

Step S100, after mixing furan and maleic anhydride, generating a first intermediate through diene synthesis reaction;

Step S200, mixing the first intermediate with bromine, and generating a second intermediate through an addition reaction;

Although the synthesis method of the present application includes the above four steps, the steps S200, S300 and S400 may be completed by a one-pot method.

Step S100

In step S100, a diene synthesis reaction is performed using furan and maleic anhydride to give a first intermediate, which is 4, 10-dioxatricyclo [5.2.1.0 (2, 6) ] dec-8-ene-3, 5-dione (abbreviated herein as compound 1A).

The reaction mechanism is as follows:

Specifically, to the reaction vessel, a quantity of maleic anhydride, furan, and a first solvent are added. Preserving heat at 20-30 ℃ under the protection of nitrogen, and stirring for 10-24 hours. Then, while gradually heating up, the mixture was distilled under normal pressure and concentrated under reduced pressure, and the solvent and excess furan were distilled off from the reaction mixture. Finally, controlling the liquid temperature at 70-80 ℃ and the vacuum degree at 2-4 Kpa until no liquid is distilled out. The concentrated residue is the crude product of compound 1A; the concentrated residue is cooled to be close to room temperature under the protection of nitrogen, and then can be directly used for the next step.

In some embodiments, where furan is not used as a solvent, the ratio of the amount of material of furan to the amount of material of maleic anhydride is 1.5 to 3.0. Of course, furan may be used as a solvent, and when furan is used as a solvent, furan may be used as a reaction raw material at the same time.

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, furan.

In some embodiments, the amount of the first solvent is not critical, as long as the maleic anhydride can be completely dissolved at a temperature between 20 ℃ and 30 ℃.

In some embodiments, the reaction temperature of step S100 is 20 ℃ to 30 ℃.

In some embodiments, the temperature of the incubation reaction is from 20 ℃ to 30 ℃.

In some embodiments, the incubation time is 24 hours to 48 hours.

Step S200

In step S200, the first intermediate is mixed with bromine and then undergoes an addition reaction to generate a second intermediate, which is a dibromo compound (abbreviated as compound 2A herein).

The reaction mechanism is as follows:

specifically, the crude product of compound 1A obtained in step S100 and the second solvent are added to a reaction vessel. Slowly dropwise adding bromine while stirring and controlling the liquid temperature to be between 20 and 50 ℃; after the dripping is finished, the temperature is kept between 20 ℃ and 50 ℃ and the mixture is stirred for 2 to 8 hours. The reaction solution thus obtained may be used directly in the next step without any treatment.

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

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

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

In some embodiments, the temperature at which bromine is added dropwise, and at which stirring is maintained after the completion of the addition, is maintained at 20 ℃ to 50 ℃, i.e., step S200 is completed at 20 ℃ to 50 ℃.

In some embodiments, the dropping rate is not critical, as long as the liquid temperature is maintained between 20℃and 50 ℃.

In some embodiments, the incubation and stirring time after the addition of bromine is 2 hours to 8 hours.

Step S300

In step S300, the second intermediate, acetic anhydride and acid catalyst are mixed and then subjected to catalytic reaction to produce a third intermediate (abbreviated herein as compound 3A).

The reaction mechanism is as follows:

Specifically, an acidic catalyst is added into the reaction liquid obtained after the reaction in the step S200, wherein the temperature is kept at 20 ℃ to 50 ℃; then dropwise adding acetic anhydride at the temperature of 20-50 ℃; after the dripping is finished, the temperature is kept between 20 ℃ and 50 ℃ for reaction for 0 to 12 hours. The reaction solution obtained was used directly in the next step without treatment.

In some embodiments, the acidic catalyst may include at least one of sulfuric acid, methane sulfonic acid, p-toluene sulfonic acid.

In some embodiments, the ratio of the amount of material of the acid catalyst to the amount of material of the maleic anhydride in step S100 is 0.01 to 0.05.

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

In some embodiments, the reaction temperature of step S300 is 20 ℃ to 50 ℃.

In some embodiments, the temperature at which the acidic catalyst is added and the acetic anhydride is added dropwise may be controlled to 20℃to 50 ℃.

In some embodiments, the rate of the acetic anhydride drop is not critical, as long as the liquid temperature can be maintained at 20℃to 50 ℃.

In some embodiments, after the acetic anhydride is added, the temperature is between 20 and 50 ℃ for more than 0 hours and less than 12 hours.

Step S400

In step S400, a third intermediate (compound 3A) and a tertiary amine are mixed and then chemically reacted to form 4-bromoaniline.

The reaction mechanism is as follows:

Specifically, the reaction solution containing the compound 3A is treated by tertiary amine, so that the target product 4-bromophthalic anhydride can be generated; and by-products such as acetate salts of tertiary amines, hydrogen bromide salts of tertiary amines, and the like. And then filtering, washing and concentrating to remove the solvent and byproducts, thus obtaining the crude product of the 4-bromophenic anhydride with the purity of more than 98 percent.

And (3) stirring and dropwise adding tertiary amine into the reaction liquid obtained after the reaction in the step S300 at the temperature of 50-70 ℃. After the dripping is finished, preserving heat at 50-70 ℃ and stirring for reaction for 6-12 hours; then the temperature of the reaction solution is controlled between 50 ℃ and 70 ℃, and the reaction solution is filtered when the reaction solution is hot; and washing the filter cake with a second solvent in a mass ratio of 2-4 times the filter cake (wet weight), heated to 50 to 70 ℃.

The washed filter cake is a mixture mainly comprising tertiary amine acetate and tertiary amine hydrogen bromide and can be used for recovering tertiary amine.

Combining the washing solution and the filtrate, controlling the temperature at 50-70 ℃ together, and concentrating under reduced pressure to evaporate the second solvent; after the concentration is carried out until a large amount of crystallization begins to appear in the residues, heating and vacuumizing are stopped, and cooling crystallization is carried out under the protection of nitrogen instead until the liquid temperature reaches-10 ℃ to-15 ℃. Filtering out the filter cake obtained by cooling and crystallizing, namely the crude product (wet product) of the 4-bromophthalic anhydride.

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

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

In some embodiments, the reaction temperature of step S400 is 50 ℃ to 70 ℃.

In some embodiments, the temperature at which tertiary amine is added dropwise is 50 ℃ to 70 ℃.

In some embodiments, the rate at which tertiary amine is added dropwise is not critical, provided that the liquid temperature can be maintained between 50 ℃ and 70 ℃.

In some embodiments, after the tertiary amine is added, the incubation is carried out at a temperature between 50 ℃ and 70 ℃ for a period of time between 6 hours and 12 hours.

In some embodiments, the second solvent used in washing the filter cake may be used in an amount of 2 to 4 times the mass ratio of the filter cake (wet weight).

In some embodiments, the temperature of the reaction solution at which the filter cake is filtered and washed is between 50 ℃ and 70 ℃ and the washing time is between 15-30 minutes.

In some embodiments, the temperature at which the filtrate and wash mixture is concentrated under reduced pressure is between 50 ℃ and 70 ℃.

In some embodiments, the final temperature at which the concentrated residue is subjected to reduced temperature crystallization is from-10 ℃ to-15 ℃.

The application can further improve the purity of the product and the yield of the product through the regulation and control of the parameters.

According to the synthetic method of the embodiment of the present application, step S100 prepares the first intermediate (compound 1A), and further prepares the target product through step S200, step S300 and step S400, which is an innovative design of the present application.

Specifically, in step S300, the ring-opening, elimination reaction of the third intermediate (compound 3A) prepared from the second intermediate (compound 2A) requires the use of a strongly acidic catalyst; in step S400, the elimination reaction for preparing 4-bromophthalic anhydride from the third intermediate (compound 3A) requires the use of an alkaline acid-binding agent. The conditions required for these two reactions are contradictory; typically, these two reactions need to be carried out in steps. However, the application realizes the continuous one-pot method of the two reactions by preferably selecting the reaction solvent and the raw materials; even the two reactions can be synchronously carried out, the operation of the whole process is simplified, and the whole reaction time and the energy consumption are shortened.

In the initial stage of the reaction, the second intermediate (compound 2A) starts to be converted into the third intermediate (compound 3A) by using the acid catalyst added first. In the middle and late stages of the reaction, the present application uses an ether solvent as a reaction solvent, and tertiary amines having a large fat-soluble group (such as at least one of N, N-diisopropylethylamine and N, N-dimethylaniline) may be preferable as an acid-binding agent. When the tertiary amine starts to be added, the acid catalyst and the tertiary amine generate corresponding tertiary amine salt; meanwhile, more hydrogen bromide salt of tertiary amine can be produced in the reaction. Since the salts of these two tertiary amines still have strong acidity; the preferable tertiary amine has larger fat-soluble groups, so that the two salts have certain solubility in ether solvents; the reaction to form the third intermediate (compound 3A) from the second intermediate (compound 2A) can be continued to be catalyzed. At this time, the two steps of reactions corresponding to the step S300 and the step S400 can be synchronously performed, and the heat preservation reaction time after the acetic anhydride is dripped in the step S300 can be reduced to 0 hour; the cost in terms of time and energy consumption is optimized.

In contrast to the prior art,

Firstly, the method for preparing 4-bromophthalic anhydride is superior to the existing method in the aspects of yield, cost and product purification difficulty. The conversion rate of the chemical reaction corresponding to the four steps is high, and the yield of the finally obtained crude 4-bromophthalic anhydride can reach more than 87% and the purity can reach more than 98%.

And secondly, impurities in the crude 4-bromophthalic anhydride product obtained by the application are mainly intermediate products which are remained in the first two steps and contain epoxy groups, salts of trace tertiary amine and the like. The solubility of these impurities in various organic solvents is much higher than that of 4-bromophthalic anhydride. The crude product is continuously crystallized or washed by only selecting a proper organic solvent, and the purity can be further improved to more than 99.5 percent.

Furthermore, the steps S200, S300 and S400 of the present application may be performed by a one-pot method; it is even possible to synchronize the chemical reactions of step S300 and step S400. These simplify the operation of the whole preparation process and optimize the costs in terms of raw materials, equipment, time and energy consumption.

The application also provides 4-bromophthalic anhydride, which is prepared from any one of the above examples. The 4-bromophthalic anhydride prepared by the method contains less impurity components and has higher purity.

Examples

Hereinafter, embodiments of the present application will be described. The embodiments described below are exemplary only for explaining the present application and are not to be construed as limiting the present application. The embodiments are not to be construed as limited to the particular techniques or conditions disclosed in the literature or as per the specifications of the product. The reagents or apparatus used were conventional products commercially available without the manufacturer's attention.

Example 1

Step S110, preparation of first intermediate (Compound 1A)

To a 1000ml three-necked flask, 49.0g (0.5 mol) of maleic anhydride, 51g (0.75 mol) of furan, and 490g of ethylene glycol dimethyl ether were added. Stirring continuously under nitrogen protection, heating and keeping the liquid temperature at 20-25 ℃ for 48 hours, and then slowly heating, distilling at normal pressure, concentrating under reduced pressure, and distilling out the ethylene glycol dimethyl ether and excess furan in the reaction liquid. Finally, controlling the liquid temperature at 70-80 ℃ and the vacuum degree at 2-4Kpa until no liquid is distilled out. The concentrated residue is the crude product of the compound 1A; the mass is about 93g, and the yield is more than or equal to 100 percent.

Step S210, preparation of second intermediate (Compound 2A)

Into a 5000ml reaction flask, 93g (about 0.5 mol) of crude compound 1A obtained in step S110 was added; and 744g of 2-methyltetrahydrofuran. Slowly dropwise adding 84g (0.525 mol) of bromine in total while stirring and controlling the liquid temperature between 40 and 50 ℃; after the dripping is finished, the temperature is kept at 40-50 ℃ and stirring is continued for 2 hours. The reaction solution obtained was used directly in the next step without treatment.

Step S310, preparing 4-bromoaniline

Adding 0.48g (0.005 mol) of methane sulfonic acid into the reaction solution obtained in the step S210 while maintaining stirring and keeping the temperature at 40-50 ℃; then, the mixture was kept at 40-50℃and 56.1g (0.55 mol) of acetic anhydride was slowly added dropwise with stirring. After the completion of the dropwise addition, the temperature was raised and kept at 60 to 70℃and 213g (1.65 mol) of N, N-diisopropylethylamine as a total was slowly added dropwise with stirring. After the dripping is finished, the temperature is kept between 60 and 70 ℃ and the stirring reaction is continued for 6 hours.

Filtering the hot reaction solution; the filter cake was washed with 2-methyltetrahydrofuran (wet weight of filter cake) in a mass ratio of 2-fold, heated to 60-70℃for 15 minutes with stirring, and filtered again while hot. And after the washing solution is combined with the previous filtrate, slowly vacuumizing and heating for concentration, and stopping heating and vacuumizing after a large amount of crystallization begins to appear in the concentrated residues. And stirring the concentrated residues under the protection of nitrogen, and cooling to the liquid temperature of-10 to-15 ℃ for crystallization. Filtering out the obtained crystals, and drying under reduced pressure to obtain 103.3g of crude 4-bromophthalic anhydride; the yield thereof was found to be 91% and the purity thereof by gas chromatography was found to be 98.2%.

Example 2

Step S120, preparation of first intermediate (Compound 1A)

Step S220, preparation of second intermediate (Compound 2A)

To a 5000ml reaction flask, 91g (about 0.5 mol) of crude compound 1A obtained in step S120 was added; and 1820g of ethylene glycol dimethyl ether. While stirring and controlling the liquid temperature between 20 and 30 ℃, 81.6g (0.51 mol) of bromine is slowly added dropwise in total; and after the dripping is finished, keeping the temperature at 20-30 ℃ and stirring for 8 hours. The reaction solution obtained was used directly in the next step without treatment.

Step S320, preparing 4-bromoaniline

Adding 2.45g (0.025 mol) of sulfuric acid to the reaction solution obtained in the step S220 while maintaining stirring and keeping the temperature at 20-30 ℃; then, the mixture was kept at 20 to 30℃and 76.5g (0.75 mol) of acetic anhydride was slowly added dropwise with stirring. After the dripping is finished, firstly preserving heat at 20-30 ℃ and stirring for 12 hours; then, the temperature was raised and kept at 50 to 60℃and 202g (2.0 mol) of triethylamine in total was slowly added dropwise with stirring. After the dripping is finished, the temperature is kept between 50 and 60 ℃ and the stirring reaction is continued for 12 hours.

Filtering the hot reaction solution; the filter cake is heated to 50-60 ℃ by using ethylene glycol dimethyl ether with the mass ratio of 4 times (the wet weight of the filter cake), stirred and washed for 30 minutes, and then filtered again when the filter cake is hot. And after the washing solution is combined with the previous filtrate, slowly vacuumizing and heating for concentration, and stopping heating and vacuumizing after a large amount of crystallization begins to appear in the concentrated residues. And stirring the concentrated residues under the protection of nitrogen, and cooling to the liquid temperature of-10 to-15 ℃ for crystallization. Filtering out the obtained crystals, and drying under reduced pressure to obtain 98.8g of crude 4-bromophthalic anhydride; the yield was 87% and the gas chromatography purity was 98.6%.

Although illustrative embodiments have been shown and described, it will be understood by those skilled in the art that the foregoing embodiments are not to be construed as limiting the application, and that changes, substitutions and alterations may be made herein without departing from the spirit, principles and scope of the application.

Claims

1. A method for synthesizing 4-bromophthalic anhydride comprises the following steps:

step S300, mixing the second intermediate, acetic anhydride and an acid catalyst, and then carrying out catalytic reaction to generate a third intermediate;

step S400, after the third intermediate and tertiary amine are mixed, the 4-bromoaniline is generated through chemical reaction.

2. The synthesis method according to claim 1, wherein step S100 satisfies at least one of the following conditions,

(2) The reaction time of the diene synthesis reaction is 24 hours to 48 hours;

(4) The ratio of the amount of the substance of furan to the amount of the substance 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 20-50 ℃;

(2) The reaction time of the addition reaction is 2 hours to 8 hours;

4. The synthesis method according to claim 1, wherein the ratio of the amount of the substance of bromine in step S200 to the amount of the substance 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 20-50 ℃;

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

7. The synthesis method according to claim 1, wherein step S400 satisfies at least one of the following conditions,

(1) The reaction temperature of the chemical reaction is 50-70 ℃;

(2) The reaction time of the chemical reaction is 6 hours to 12 hours;

(4) The tertiary amine includes at least one of triethylamine, pyridine, 2-methylpyridine, N-diisopropylethylamine, and N, N-dimethylaniline.

8. The synthetic method of claim 7, wherein the tertiary amine comprises at least one of N, N-diisopropylethylamine and N, N-dimethylaniline.

9. The synthesis method according to claim 1, wherein,

The ratio of the amount of the tertiary amine substance in step S400 to the amount of the maleic anhydride substance in step S100 is 3.3 to 4.0.

10. A 4-bromophthalic anhydride prepared by the synthetic method of any one of claims 1-9.