A method for synthesizing phthalaldehyde
By adding an appropriate amount of water and optimizing the reaction conditions during the bromination of o-xylene, the yield of α,α,α',α'-tetrabromo-o-xylene was improved, solving the problems of low yield and high cost in the existing synthesis of o-phthalaldehyde and realizing efficient production of o-phthalaldehyde.
Patent Information
- Application Number
- CN202510021151.3
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-01-07
- Publication Date
- 2026-07-07
AI Technical Summary
Among the existing methods for synthesizing phthalaldehyde, the bromination hydrolysis method has low yield and high cost, the naphthalene ozone oxidation hydrogenation method has complicated steps and is difficult to separate by-products, the phthalimide oxidation method has high cost and generates a lot of nitrogen oxides, and the Br2 method has low yield and high storage requirements, making it difficult to achieve industrial production.
During the bromination of o-xylene, an appropriate amount of water is added at a suitable time, and the reaction is carried out by ultraviolet light irradiation to generate α,α,α',α'-tetrabromo-o-xylene, which is then hydrolyzed to obtain o-phthalaldehyde. The bromination process is optimized to improve the yield of intermediate products.
The yield of α,α,α',α'-tetrabromo-o-xylene was significantly improved, with the yield of o-phthalaldehyde reaching 86.35%. This overcame the disadvantages of brominated reagents being volatile and highly toxic, and reduced production costs.
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Abstract
Description
Technical Field
[0001] This invention belongs to the field of organic chemistry technology, and specifically relates to a method for synthesizing o-phthalaldehyde. Background Technology
[0002] Phthalate is a pale yellow crystalline solid, sensitive to light and air, and soluble in water, ethanol, ether, and other organic solvents. Phthalate is mainly used in the determination of amine alkaloids, as a reagent for histamine assays using fluorometers, and in pharmaceutical testing. In the biomedical field, phthalate exhibits excellent performance in the disinfection of medical endoscopes.
[0003] Currently, glutaraldehyde is mainly used for endoscopic disinfection. Glutaraldehyde has the advantages of high efficiency, rapid disinfection, and wide applicability, and can be used to eliminate a variety of bacteria and microorganisms. However, glutaraldehyde has significant mucosal toxicity, skin irritation, and cytotoxicity, and can induce complications such as colitis and pneumonia. Using phthalaldehyde instead of glutaraldehyde for sterilization and disinfection not only provides the high sterilization efficiency and low corrosiveness of glutaraldehyde, but also overcomes the disadvantages of glutaraldehyde such as irritation, toxicity, high concentration requirements, and long action time. Therefore, phthalaldehyde, as a novel disinfectant, has received extensive research and application.
[0004] The main synthetic routes for o-xylene include o-xylene bromide hydrolysis, chlorination hydrolysis, naphthalene ozone oxidation hydrogenation, and o-phthalimide oxidation.
[0005] The o-xylene chlorination hydrolysis method uses chlorine gas as raw material. The intermediate product o-tetrachloromethylbenzene has a low yield (not higher than 40%) and is difficult to separate. The hydrolysis yield is not higher than 75%, and the final product has high cost and low yield.
[0006] The naphthalene ozone oxidation hydrogenation method involves complicated steps and is difficult to control process conditions. It is difficult to separate the by-product ester from phthalaldehyde, resulting in low product purity. This leads to high production costs, serious pollution, high equipment investment, and is not easy to industrialize.
[0007] The phthalic acid oxidation method uses phthalic acid as raw material and then oxidizes it through an acetic acid-nitric acid system to obtain high-purity phthalaldehyde. A large amount of nitrogen oxides are generated in the reaction, and phthalic acid is expensive and difficult to obtain, resulting in high costs.
[0008] Using Br2 as a brominating agent to prepare o-phthalaldehyde via the bromination and hydrolysis of o-xylene is a widely reported method. However, the overall yield of this method is currently low (around 50%), and Br2 is highly volatile and toxic, requiring strict storage conditions. Summary of the Invention
[0009] Objective of the Invention: The objective of this invention is to address the shortcomings of existing technologies by providing a method for synthesizing o-phthalaldehyde. This invention optimizes the bromination and hydrolysis process by adding an appropriate amount of water at a suitable time during the o-xylene bromination process, thereby increasing the yield of the intermediate product α,α,α',α'-tetrabromo-o-xylene and consequently improving the yield of the final product, o-phthalaldehyde.
[0010] Technical solution: The objective of this invention is achieved through the following technical solution:
[0011] This invention provides a method for synthesizing o-phthalaldehyde, comprising the following steps:
[0012] (1) Mix o-xylene, brominating reagent and organic solvent, and react under ultraviolet light to generate brominated products with different degrees of bromination;
[0013] (2) Add water to the above reaction solution and continue the reaction;
[0014] (3) After the reaction is complete, the organic solvent and water are evaporated to obtain crude α,α,α',α'-tetrabromo-o-xylene; the crude product is recrystallized to obtain α,α,α',α'-tetrabromo-o-xylene product.
[0015] (4) Hydrolyze α,α,α',α'-tetrabromo-o-xylene to obtain the o-phthalaldehyde.
[0016] Preferably, in step (1), the reaction temperature is 100-150°C and the reaction time is 3-10h.
[0017] If the bromination reaction is too short, the selectivity of α,α,α',α'-tetrabromo-o-xylene is too low; if the bromination reaction is too long, the subsequent improvement in the selectivity of α,α,α',α'-tetrabromo-o-xylene is not significant, thus affecting the reaction efficiency. Therefore, in this invention, an appropriate amount of water is added after the bromination reaction has proceeded for a certain period of time.
[0018] This invention involves adding an appropriate amount of water at a suitable time. Since the byproduct HBr generated during the bromination process enters the aqueous phase, it promotes the bromination reaction equilibrium to shift to the right, significantly increasing the yield of α,α,α',α'-tetrabromo-o-xylene, thereby increasing the yield of the final product o-phthalaldehyde. The optimal yield of o-phthalaldehyde reaches 86.35%.
[0019] Preferably, in step (1), the brominating agent is selected from NBS, 1,3-dibromo-5,5-dimethylhydantoin, pyridine bromide 3-PyHBr3, carbon tetrabromide, 5,5-dibromo-2,2-dimethyl-4,6-dione-1,3-dioxane, dibromocyanoacetamide, dibromoisocyanuric acid, 1,3,5-tribromo-1,3,5-triazine-2,4,6-trione, N-bromoacetamide, or N-bromo-o-sulfonylbenzeneimide.
[0020] Preferably, in step (1), the organic solvent is selected from carbon tetrachloride or dichloromethane.
[0021] Preferably, in step (1), the molar amount of the brominating agent is 4 to 10 times the molar amount of o-xylene;
[0022] Furthermore, the molar amount of the halogenated reagent is 5 to 8 times the molar amount of o-xylene.
[0023] Preferably, in step (1), the wavelength of the ultraviolet light is controlled between 295 and 400 nm.
[0024] Preferably, in step (2), the temperature for the continued reaction is 100-150°C, and the reaction time is 1-3 hours.
[0025] Preferably, in step (2), the volume of water added is 0.2 to 2 times the volume of the organic solvent. If the volume of water added is too small, it will affect the entry of HBr into the aqueous phase and reduce efficiency; if the volume of water added is too large, the separation difficulty will increase and the distillation burden will be increased.
[0026] Furthermore, the volume of water added is 0.4-1 times the volume of the organic solvent.
[0027] Preferably, in step (3), the recrystallization solvent is chloroform.
[0028] Preferably, in step (4), the hydrolysis method is as follows: α,α,α',α'-tetrabromo-o-xylene is added to an organic acid, followed by the addition of an alkaline solution, and the reaction is carried out by heating and stirring; the organic acid is selected from formic acid, acetic acid, propionic acid, or butyric acid; the alkaline solution is selected from NaOH aqueous solution or KOH aqueous solution.
[0029] Furthermore, the reaction temperature is 100–150°C; the reaction time after adding the alkaline solution is 3–10 h.
[0030] Furthermore, the reaction temperature is 120–140°C; the reaction time after adding the alkaline solution is 3–7 hours.
[0031] Furthermore, the molar amount of the organic acid is 10 to 25 times that of α,α,α',α'-tetrabromo-o-xylene.
[0032] Furthermore, the molar amount of the organic acid is 12 to 16 times that of α,α,α',α'-tetrabromo-o-xylene.
[0033] Furthermore, the molar amount of the base is 3 to 9 times the molar amount of α,α,α',α'-tetrabromo-o-xylene.
[0034] Furthermore, the molar amount of the base is 3 to 6 times the molar amount of α,α,α',α'-tetrabromo-o-xylene.
[0035] Beneficial effects:
[0036] (1) In the process of brominating o-xylene, the present invention adds an appropriate amount of water at the right time, which improves the yield of α,α,α',α'-tetrabromo-o-xylene and realizes the efficient synthesis of o-xylene into o-phthalaldehyde with a yield of up to 86.35%.
[0037] (2) The present invention uses other brominating reagents such as NBS to overcome the disadvantages of Br2 being volatile and highly toxic, and is safer in the reaction process. Attached Figure Description
[0038] Figure 1 The results of gas chromatography analysis of the o-xylene bromination reaction product in Example 1 of this invention are shown.
[0039] Figure 2 The results of gas chromatography analysis of the o-xylene bromination reaction product of Comparative Example 2 of this invention are shown. Detailed Implementation
[0040] The technical solution of the present invention will be described in detail below through specific embodiments, but the scope of protection of the present invention is not limited to the embodiments described.
[0041] Unless otherwise specified, the experimental methods used in the following examples are conventional methods. Unless otherwise specified, the experimental materials used in the following examples are commercially available products.
[0042] Example 1
[0043] 0.01 mol o-xylene, 0.06 mol NBS, and 50 mL CCl4 were added to a round-bottom flask. The mixture was heated and stirred at 145 °C, and irradiated with a UV lamp (395 nm). After 7 h of reaction, 20 mL of water was added to the reaction solution, and the mixture was heated at 145 °C for another 2 h. The product was analyzed by gas chromatography, and the results are shown in the figure. Figure 1 The conversion rate of o-xylene was 100%, and the selectivity for α,α,α',α'-tetrabromo-o-xylene was 97.3%.
[0044] CCl4 and water were removed by vacuum distillation to obtain crude α,α,α',α'-tetrabromo-o-xylene. The product was recrystallized twice with chloroform to give 3.69 g of product, with a yield of 87.57%.
[0045] 3.69 g of α,α,α',α'-tetrabromo-o-xylene was added to a round-bottom flask, followed by 0.13 mol of CH3COOH. The mixture was stirred at 120 °C for 10 min. Then, 20 mL of 2 mol / L NaOH solution was added, and the mixture was heated and stirred for another 5 h. Gas chromatography analysis of the product showed that the conversion rate of α,α,α',α'-tetrabromo-o-xylene was 100%, the selectivity for o-phthalaldehyde was 96.4%, and the yield was 86.35%.
[0046] Example 2
[0047] 0.01 mol of o-xylene, 0.07 mol of N-bromoacetamide, and 50 mL of CCl4 were added to a round-bottom flask. The mixture was heated and stirred at 135 °C, and irradiated with a UV lamp at a wavelength of 365 nm. After reacting for 7 h, 20 mL of water was added to the reaction solution, and the reaction was continued at 135 °C for another 2 h. Gas chromatography analysis of the product showed that the conversion rate of o-xylene was 100%, and the selectivity for α,α,α',α'-tetrabromo-o-xylene was 90.2%.
[0048] CCl4 and water were removed by vacuum distillation to obtain crude α,α,α',α'-tetrabromo-o-xylene. The product was recrystallized twice with chloroform to give 3.42 g of product, with a yield of 81.18%.
[0049] 3.42 g of the obtained α,α,α',α'-tetrabromo-o-xylene was added to a round-bottom flask, followed by 0.12 mol CH3COOH. The mixture was stirred at 140 °C for 10 min. Then, 22 mL of 2 mol / L KOH solution was added, and the mixture was heated and stirred for another 5 h. Gas chromatography analysis of the product showed that the conversion rate of α,α,α',α'-tetrabromo-o-xylene was 100%, the selectivity for o-phthalaldehyde was 92.3%, and the yield was 74.93%.
[0050] Example 3
[0051] 0.01 mol of o-xylene, 0.05 mol of NBS, and 50 mL of CH₂Cl₂ were added to a round-bottom flask. The mixture was heated and stirred at 125 °C, and irradiated with a UV lamp at a wavelength of 295 nm. After reacting for 4 h, 30 mL of water was added to the reaction solution, and the reaction was continued at 125 °C for another 2 h. Gas chromatography analysis of the product showed that the conversion rate of o-xylene was 100%, and the selectivity for α,α,α',α'-tetrabromo-o-xylene was 91.3%.
[0052] CH2Cl2 and water were removed by vacuum distillation to obtain crude α,α,α',α'-tetrabromo-o-xylene. The product was recrystallized twice with chloroform to give 3.50 g of product, with a yield of 83.08%.
[0053] 3.50 g of the obtained α,α,α',α'-tetrabromo-o-xylene was added to a round-bottom flask, followed by 0.13 mol CH3CH2COOH. The mixture was stirred at 130 °C for 10 min. Then, 18 mL of 2 mol / L NaOH solution was added, and the mixture was heated and stirred for another 5 h. Gas chromatography analysis of the product showed that the conversion rate of α,α,α',α'-tetrabromo-o-xylene was 100%, the selectivity for o-phthalaldehyde was 93.7%, and the yield was 77.85%.
[0054] Example 4
[0055] 0.01 mol of o-xylene, 0.07 mol of 3-PyHBr3, and 50 mL of CH2Cl2 were added to a round-bottom flask. The mixture was heated and stirred at 145 °C, and irradiated with a UV lamp at a wavelength of 295 nm. After reacting for 7 h, 25 mL of water was added to the reaction solution, and the reaction was continued for another 2 h. Gas chromatography analysis of the product showed that the conversion rate of o-xylene was 100%, and the selectivity for α,α,α',α'-tetrabromo-o-xylene was 93.3%.
[0056] Carbon tetrachloride and water were removed by vacuum distillation to obtain crude α,α,α',α'-tetrabromo-o-xylene. The product was recrystallized twice with chloroform to give 3.46 g of product, with a yield of 82.10%.
[0057] 3.46 g of the obtained α,α,α',α'-tetrabromo-o-xylene was added to a round-bottom flask, followed by 0.13 mol HCOOH. The mixture was stirred at 130 °C for 10 min. Then, 23 mL of 2 mol / L KOH solution was added, and the mixture was heated and stirred for another 4 h. Gas chromatography analysis of the product showed that the conversion rate of α,α,α',α'-tetrabromo-o-xylene was 100%, the selectivity for o-phthalaldehyde was 95.7%, and the yield was 78.57%.
[0058] Example 5
[0059] 0.01 mol of o-xylene, 0.07 mol of 1,3-dibromo-5,5-dimethylhydantoin, and 50 mL of CCl4 were added to a round-bottom flask. The mixture was heated and stirred at 140 °C, and irradiated with a UV lamp at a wavelength of 325 nm. After reacting for 6 h, 35 mL of water was added to the reaction solution, and the reaction was continued for another 3 h. Gas chromatography analysis of the product showed that the conversion rate of o-xylene was 100%, and the selectivity for α,α,α',α'-tetrabromo-o-xylene was 95.7%.
[0060] CCl4 and water were removed by vacuum distillation to obtain crude α,α,α',α'-tetrabromo-o-xylene. The product was recrystallized twice with chloroform to give 3.57 g of product, with a yield of 84.65%.
[0061] 3.57 g of the obtained α,α,α',α'-tetrabromo-o-xylene was added to a round-bottom flask, followed by 0.12 mol CH3COOH. The mixture was stirred at 130 °C for 10 min. Then, 20 mL of 2 mol / L NaOH solution was added, and the mixture was heated and stirred for another 6 h. Gas chromatography analysis of the product showed that the conversion rate of α,α,α',α'-tetrabromo-o-xylene was 100%, the selectivity for o-phthalaldehyde was 98.7%, and the yield was 83.55%.
[0062] Example 6
[0063] 0.05 mol of o-xylene, 0.2 mol of 3-PyHBr3, and 150 mL of CCl4 were added to a round-bottom flask. The mixture was heated and stirred at 100 °C, and irradiated with a UV lamp at a wavelength of 325 nm. After reacting for 6 h, 300 mL of water was added to the reaction solution, and the reaction was continued for another 1 h. Gas chromatography analysis of the product showed that the conversion rate of o-xylene was 100%, and the selectivity for α,α,α',α'-tetrabromo-o-xylene was 92.7%.
[0064] CCl4 and water were removed by vacuum distillation to obtain crude α,α,α',α'-tetrabromo-o-xylene. The product was recrystallized twice with chloroform to give 17.62 g of product, with a yield of 83.56%.
[0065] 17.62 g of the obtained α,α,α',α'-tetrabromo-o-xylene was added to a round-bottom flask, followed by 0.50 mol CH3COOH. The mixture was stirred at 150 °C for 10 min. Then, 63 mL of 2 mol / L KOH solution was added, and the mixture was heated and stirred for another 8 h. Gas chromatography analysis of the product showed that the conversion rate of α,α,α',α'-tetrabromo-o-xylene was 100%, the selectivity for o-phthalaldehyde was 93.9%, and the yield was 78.46%.
[0066] Example 7
[0067] 0.5 mol of o-xylene, 3 mol of NBS, and 1000 mL of CCl4 were added to a round-bottom flask. The mixture was heated and stirred at 150 °C, and irradiated with a UV lamp at a wavelength of 375 nm. After reacting for 10 h, 200 mL of water was added to the reaction solution, and the reaction was continued for another 3 h. Gas chromatography analysis of the product showed that the conversion rate of o-xylene was 100%, and the selectivity for α,α,α',α'-tetrabromo-o-xylene was 94.1%.
[0068] CCl4 and water were removed by vacuum distillation to obtain crude α,α,α',α'-tetrabromo-o-xylene. The product was recrystallized twice with chloroform to give 186.29 g of product, with a yield of 88.34%.
[0069] 186.29 g of the obtained α,α,α',α'-tetrabromo-o-xylene was added to a round-bottom flask, followed by 7.17 mol of CH3COOH. The mixture was stirred at 100 °C for 30 min. Then, 1320 mL of 2 mol / L NaOH solution was added, and the mixture was heated and stirred for another 10 h. Gas chromatography analysis of the product showed that the conversion rate of α,α,α',α'-tetrabromo-o-xylene was 100%, the selectivity for o-phthalaldehyde was 99.5%, and the yield was 85.87%.
[0070] Comparative Example 1
[0071] 0.01 mol of o-xylene, 0.06 mol of Br2, and 50 mL of CCl4 were added to a round-bottom flask. The mixture was heated and stirred at 145 °C, and irradiated with a UV lamp (395 nm) for 7 h. Gas chromatography analysis showed that the conversion of o-xylene was 100%, the selectivity for α,α,α',α'-tetrabromo-o-xylene was 43.7%, and the selectivity for α,α,α'-tribromo-o-xylene was 45.4%.
[0072] CCl4 was removed by vacuum distillation, and the product was recrystallized twice with chloroform to obtain a mixture mainly composed of α,α,α',α'-tetrabromo-o-xylene and α,α,α'-tribromo-o-xylene. The resulting mixture was added to a round-bottom flask, and 0.11 mol CH3COOH was added. The mixture was stirred at 130 °C for 10 min. Then, 17 mL of 2 mol / L NaOH solution was added, and the mixture was heated and stirred for another 6 h. Gas chromatography analysis showed that both α,α,α',α'-tetrabromo-o-xylene and α,α,α'-tribromo-o-xylene were completely converted, with a selectivity of 40.5% for o-phthalaldehyde and a yield of 33.2%.
[0073] Comparative Example 2
[0074] 0.01 mol o-xylene, 0.06 mol NBS, and 50 mL CCl4 were added to a round-bottom flask. The mixture was heated and stirred at 145 °C, and irradiated with a UV lamp (395 nm) for 7 h. The product was analyzed by gas chromatography, and the results are shown below. Figure 2 The conversion rate of o-xylene was 100%, the selectivity for α,α,α',α'-tetrabromo-o-xylene was 50.6%, and the selectivity for α,α,α'-tribromo-o-xylene was 30.8%.
[0075] CCl4 was removed by vacuum distillation, and the product was recrystallized twice with chloroform to obtain a mixture mainly composed of α,α,α',α'-tetrabromo-o-xylene and α,α,α'-tribromo-o-xylene. The resulting mixture was added to a round-bottom flask, and 0.10 mol CH3COOH was added. The mixture was stirred at 140 °C for 10 min. Then, 15 mL of 2 mol / L KOH solution was added, and the mixture was heated and stirred for another 6 h. Gas chromatography analysis showed that both α,α,α',α'-tetrabromo-o-xylene and α,α,α'-tribromo-o-xylene were completely converted, with a selectivity of 46.5% for o-phthalaldehyde and a yield of 41.5%.
[0076] Comparative Example 3
[0077] 0.01 mol of o-xylene, 0.06 mol of NBS, and 50 mL of CH₂Cl₂ were added to a round-bottom flask. The mixture was heated and stirred at 130 °C, and irradiated with a UV lamp at a wavelength of 325 nm. After reacting for 1 h, 20 mL of water was added to the reaction solution, and the reaction was continued for another 2 h. Gas chromatography analysis of the product showed that the conversion rate of o-xylene was 77.1%, the selectivity for α,α,α',α'-tetrabromo-o-xylene was 67.3%, and the selectivity for α,α,α'-tribromo-o-xylene was 21.7%.
[0078] CCl4 and water were removed by vacuum distillation, and the mixture was recrystallized twice with chloroform to obtain a mixture mainly composed of α,α,α',α'-tetrabromo-o-xylene and α,α,α'-tribromo-o-xylene. The resulting mixture was added to a round-bottom flask, and 0.10 mol CH3COOH was added. The mixture was stirred at 120 °C for 10 min. Then, 18 mL of 2 mol / L NaOH solution was added, and the mixture was heated and stirred for another 5 h. Gas chromatography analysis showed that both α,α,α',α'-tetrabromo-o-xylene and α,α,α'-tribromo-o-xylene were completely converted, with a selectivity of 60.5% for o-phthalaldehyde and a yield of 51.2%.
[0079] Comparative Example 4
[0080] 0.01 mol of o-xylene, 0.08 mol of 1,3-dibromo-5,5-dimethylhydantoin, and 50 mL of CCl4 were added to a round-bottom flask. The mixture was heated and stirred at 145 °C, and irradiated with a UV lamp at a wavelength of 325 nm. After reacting for 5 h, 5 mL of water was added to the reaction solution, and the reaction was continued for another 2 h. Gas chromatography analysis of the product showed that the conversion rate of o-xylene was 100%, the selectivity for α,α,α',α'-tetrabromo-o-xylene was 75.3%, and the selectivity for α,α,α'-tribromo-o-xylene was 14.7%.
[0081] CCl4 and water were removed by vacuum distillation, and the mixture was recrystallized twice with chloroform to obtain a mixture mainly composed of α,α,α',α'-tetrabromo-o-xylene and α,α,α'-tribromo-o-xylene. The resulting mixture was added to a round-bottom flask, and 0.13 mol CH3COOH was added. The mixture was stirred at 120 °C for 10 min. Then, 22 mL of 2 mol / L NaOH solution was added, and the mixture was heated and stirred for another 5 h. Gas chromatography analysis showed that both α,α,α',α'-tetrabromo-o-xylene and α,α,α'-tribromo-o-xylene were completely converted, with a selectivity of 68.5% for o-phthalaldehyde and a yield of 58.4%.
[0082] As described above, although the invention has been shown and described with reference to specific preferred embodiments, it should not be construed as limiting the invention itself. Various changes in form and detail may be made without departing from the spirit and scope of the invention as defined in the appended claims.
Claims
1. A method for synthesizing o-phthalaldehyde, characterized in that, Includes the following steps: (1) Mix o-xylene, brominating reagent and organic solvent, and react under ultraviolet light to generate brominated products with different degrees of bromination; (2) Add water to the above reaction solution and continue the reaction; (3) After the reaction is complete, the organic solvent and water are evaporated to obtain crude α,α,α',α'-tetrabromo-o-xylene; the crude product is recrystallized to obtain α,α,α',α'-tetrabromo-o-xylene product. (4) Hydrolyze α,α,α',α'-tetrabromo-o-xylene to obtain the o-phthalaldehyde.
2. The synthesis method according to claim 1, characterized in that, In step (1), the reaction temperature is 100-150℃ and the reaction time is 3-10h.
3. The synthesis method according to claim 1, characterized in that, In step (1), the brominating reagent is selected from NBS, 1,3-dibromo-5,5-dimethylhydantoin, pyridine bromide 3-PyHBr3, carbon tetrabromide, 5,5-dibromo-2,2-dimethyl-4,6-dione-1,3-dioxane, dibromocyanoacetamide, dibromoisocyanuric acid, 1,3,5-tribromo-1,3,5-triazine-2,4,6-trione, N-bromoacetamide, or N-bromo-o-sulfonylbenzeneimide.
4. The synthesis method according to claim 1, characterized in that, In step (1), the organic solvent is selected from carbon tetrachloride or dichloromethane.
5. The synthesis method according to claim 1, characterized in that, In step (1), the molar amount of the brominated reagent is 4 to 10 times that of o-xylene, preferably 5 to 8 times.
6. The synthesis method according to claim 1, characterized in that, In step (1), the wavelength of the ultraviolet light is controlled between 295 and 400 nm.
7. The synthesis method according to claim 1, characterized in that, In step (2), the temperature for the continued reaction is 100-150°C, and the reaction time is 1-3 hours.
8. The synthesis method according to claim 1, characterized in that, In step (2), the volume of water added is 0.2 to 2 times the volume of the organic solvent, preferably 0.4 to 1 times.
9. The synthesis method according to claim 1, characterized in that, In step (4), the hydrolysis method is as follows: add α,α,α',α'-tetrabromo-o-xylene to an organic acid, then add an alkaline solution, and heat and stir to react; the organic acid is selected from formic acid, acetic acid, propionic acid or butyric acid; the alkaline solution is selected from NaOH aqueous solution or KOH aqueous solution.
10. The synthesis method according to claim 9, characterized in that, The reaction temperature is 100–150°C, preferably 120–140°C; the reaction time after adding the alkaline solution is 3–10 h, preferably 3–7 h.
11. The synthesis method according to claim 9, characterized in that, The molar amount of the organic acid is 10 to 25 times that of α,α,α',α'-tetrabromo-o-xylene, preferably 12 to 16 times.
12. The synthesis method according to claim 9, characterized in that, The molar amount of the base is 3 to 9 times that of α,α,α',α'-tetrabromo-o-xylene, preferably 3 to 6 times.