Preparation method of 3-bromo-7-chlorodibenzo [b, d] furan

Abstract

The invention discloses a preparation method of 3-bromo-7-chlorodibenzo [b, d] furan, relates to the technical field of synthesis of dibenzofuran compounds, and aims to solve the problems that an existing preparation method of 3-bromo-7-chlorodibenzo [b, d] furan is high in production cost, poor in reaction selectivity, low in total reaction yield, not environmentally friendly enough and not beneficial to industrial mass production. The preparation method comprises the following steps: by taking 2, 5-dibromo nitrobenzene and 3-chlorophenol as raw materials, under the action of a palladium catalyst, a copper catalyst, a ligand, an additive and alkali, preparing 3-bromo-7-chlorodibenzo [b, d] furan by a C-O coupling and C-C coupling cascade reaction one-pot method; the method has the advantages of short synthesis steps, simple preparation process, mild reaction conditions, low preparation cost, high atom utilization rate, high total reaction yield, economy and environmental protection, and is easy for industrial application.

Description

Technical Field

[0001] The invention relates to the technical field of synthesis of dibenzofuran compounds, in particular to a method for preparing 3-bromo-7-chlorodibenzo[b,d]furan. Background Art

[0002] Dibenzofuran photoelectric materials are a class of oxygen-containing condensed-ring aromatic compounds, which are widely used in blue light OLED fluorescent materials and phosphorescent iridium complex doped layer luminescent materials, and have the functions of reducing device driving voltage and improving device luminescence efficiency. Dibenzofuran photoelectric materials have broad application prospects and extremely high development and research value in organic light-emitting devices.

[0003] 3-Bromo-7-chlorodibenzo[b,d]furan is an important intermediate for introducing dibenzofuran skeleton in organic synthesis. It is widely used in biopharmaceuticals, luminescent materials and other fields. The study of its synthesis method is of great significance. At present, there are mainly three methods for preparing 3-bromo-7-chlorodibenzo[b,d]furan reported in domestic and foreign literature.

[0004] Route 1: First synthesize 4-bromo-4'-chloro-2'-fluoro-[1,1'-biphenyl]-2-ol, and then perform intramolecular nucleophilic substitution ring closure to prepare 3-bromo-7-chlorodibenzo[b,d]furan. For example, patent CN201710940389.1 reports a method for preparing 3-bromo-7-chlorodibenzo[b,d]furan, which uses 1-bromo-4-chloro-2-fluorobenzene and 4-bromo-2-methoxyphenylboronic acid as raw materials, and prepares 3-bromo-7-chlorodibenzo[b,d]furan through three steps of Suzuki coupling reaction, boron tribromide demethylation, and intramolecular nucleophilic substitution ring closure reaction. The total yield of the three-step reaction is 23.4%;

[0005]

[0006] Route 2: First synthesize 4'-bromo-4-chloro-2'-fluoro-[1,1'-biphenyl]-2-ol, and then perform intramolecular nucleophilic substitution ring closure to prepare 3-bromo-7-chlorodibenzo[b,d]furan. For example, patent CN201980030178.1 reports a method for preparing 3-bromo-7-chlorodibenzo[b,d]furan, which uses 1-bromo-3-fluoro-4-iodobenzene and (5-chloro-2-methoxyphenyl)boric acid as raw materials, and prepares 3-bromo-7-chlorodibenzo[b,d]furan through three steps of Suzuki coupling reaction, boron tribromide demethylation, and intramolecular nucleophilic substitution ring closure reaction. The total yield of the three-step reaction is 40.9%;

[0007]

[0008] Route 3: First synthesize 4'-bromo-4-chloro-[1,1'-biphenyl]-2-ol or 4-bromo-4'-chloro-[1,1'-biphenyl]-2-ol, and then perform intramolecular dehydrogenation and cyclization to prepare 3-bromo-7-chlorodibenzo[b,d]furan. For example, patent CN202010666532.4 reports a method for preparing 3-bromo-7-chlorodibenzo[b,d]furan, which first prepares 4'-bromo-4-chloro-[1,1'-biphenyl]-2-ol or 4-bromo-4'-chloro-[1,1'-biphenyl]-2-ol through a Suzuki coupling reaction, and then performs intramolecular dehydrogenation and cyclization under palladium catalysis to prepare 3-bromo-7-chlorodibenzo[b,d]furan in two steps;

[0009]

[0010] Among the above-mentioned synthetic routes, Route 1 and Route 2 adopt the commonly used synthetic method of dibenzofuran compounds, and both prepare 3-bromo-7-chlorodibenzo[b,d]furan through three-step reactions including Suzuki coupling, boron tribromide demethylation and nucleophilic ring closure. However, the starting raw materials 4-bromo-2-methoxyphenylboric acid or (5-chloro-2-methoxyphenyl)boric acid are relatively expensive, the boron trifluoride demethylation reaction produces a large amount of waste acid, and the total yield of the three-step reaction is low, which has major defects from both environmental protection and economic perspectives. Route 3 first prepares 4'-bromo-4-chloro-[1,1'-biphenyl]-2-ol or 4-bromo-4'-chloro-[1,1'-biphenyl]-2-ol through Suzuki coupling reaction, and then prepares 3-bromo-7-chlorodibenzo[b,d]furan through intramolecular dehydrogenation ring-closure reaction. The reaction conditions are mild and the preparation steps are short, but expensive hexafluorobenzene is required as a reaction solvent, 1,3-dimethyl-2-imidazolidinone is used as another reaction solvent, and two equivalents of tert-butyl peroxybenzoate are used as an oxidant. In the post-treatment process, environmental problems such as more waste, more pollution, and more difficulty in post-treatment purification are caused. Therefore, this route has the disadvantages of high raw material prices, great difficulty in post-treatment purification, and heavy pollution.

[0011] In summary, the existing synthesis methods generally have the disadvantages of high reaction raw material prices, poor reaction selectivity and atom economy, high production costs, and prominent environmental issues, which do not meet the development requirements of green chemistry and synthetic economy, and seriously restrict their industrial application in the preparation of 3-bromo-7-chlorodibenzo[b,d]furan. Therefore, a preparation method of 3-bromo-7-chlorodibenzo[b,d]furan is urgently needed to solve this problem. Summary of the invention

[0012] The object of the present invention is to provide a method for preparing 3-bromo-7-chlorodibenzo[b,d]furan, so as to solve the problem that the existing preparation method is not simple, economical, green and efficient enough.

[0013] To achieve the above object, the present invention provides the following technical scheme: a method for preparing 3-bromo-7-chlorodibenzo[b,d]furan, comprising the following specific contents: using 2,5-dibromonitrobenzene and 3-chlorophenol as raw materials, under the action of a palladium catalyst, a copper catalyst, a ligand, an additive and a base, a CO coupling and a CC coupling tandem reaction are carried out in a one-pot process to prepare 3-bromo-7-chlorodibenzo[b,d]furan;

[0014] Preferably, the molar ratio of 3-chlorophenol, 2,5-dibromonitrobenzene, palladium catalyst, copper catalyst, ligand, additive and base is 1:(1.05-2.0):(0.005-0.05):(0.05-0.2):(0.01-0.1):(0.1-0.5):(2.0-4.0);

[0015] Optionally, in the above method or preferred embodiment, the reaction temperature is 100 to 140° C. and the reaction time is 24 to 36 hours.

[0016] Optionally, in the above method or preferred embodiment, the palladium catalyst is one or more of palladium acetate, tris(dibenzylideneacetone)dipalladium, [1,1'-bis(diphenylphosphino)ferrocene]palladium dichloride, [1,1'-bis(di-tert-butylphosphino)ferrocene]palladium dichloride, [1,1'-bis(di-cyclohexylphosphino)ferrocene]palladium dichloride; the copper catalyst is one or more of copper acetate, copper trifluoromethanesulfonate, copper acetylacetonate, copper bromide, copper chloride, and cuprous iodide.

[0017] Optionally, in the above method or preferred embodiment, the ligand is an imidazolium salt nitrogen heterocyclic carbene ligand selected from one or more of 1,3-bis(2,6-diisopropylphenyl)imidazolium tetrafluoroborate, 1,3-bis(2,6-diisopropylphenyl)imidazolium chloride, 1,3-bis(2,4,6-trimethylphenyl)imidazolium chloride, and 1,3-bis(2,6-diisopropylphenyl)-4,5-dihydroimidazolium tetrafluoroborate.

[0018] Optionally, in the above method or preferred embodiment, the additive is one or more of tetrabutylammonium bromide and tetrabutylammonium chloride, preferably tetrabutylammonium bromide.

[0019] Optionally, in the above method or preferred embodiment, the base is selected from one or more of potassium phosphate, cesium carbonate, potassium carbonate, sodium tert-butoxide, and potassium tert-butoxide.

[0020] Optionally, in the above method or preferred embodiment, the reaction is carried out in a solvent, and the solvent is one or more of N,N-dimethylformamide, N,N-dimethylacetamide, dimethyl sulfoxide, and 1,4-dioxane.

[0021] Preferably, after the reaction is completed, post-processing and product purification is performed, and the steps include: adding water and an organic solvent to the reaction system for dilution and extraction after cooling to room temperature, washing the organic liquid, drying, filtering with silica gel, desolventizing, and recrystallizing to obtain the product;

[0022] Optionally, in the above preferred embodiment, the organic solvent used for dilution and extraction in the post-treatment is selected from one or more of ethyl acetate, dichloromethane and xylene; the solvent used for recrystallization is selected from one or more of ethyl acetate, dichloromethane, o-xylene, methanol, ethanol and n-hexane.

[0023] Compared with the prior art, the present invention has the following beneficial effects:

[0024] 1. The preparation method of 3-bromo-7-chlorodibenzo[b,d]furan uses 2,5-dibromonitrobenzene and 3-chlorophenol as starting raw materials. The raw materials are cheap and easy to obtain, the reaction process conditions are mild and easy to control, the preparation cost is low, and the atomic utilization rate and the total reaction yield are high, which can reach more than 60%.

[0025] 2. The preparation method of 3-bromo-7-chlorodibenzo[b,d]furan adopts palladium / copper bimetallic synergistic catalysis, does not require inert gas protection, is environmentally friendly, and has mild conditions. The product is obtained by a one-pot method, avoiding the phenolic hydroxyl demethylation reaction and intermediate separation process, and can also avoid the use of boron tribromide to demethylate A large amount of acidic waste liquid generated. It has the characteristics of short synthesis steps, simple preparation process, and green environmental protection, which is conducive to large-scale production and has industrial feasibility. It expands the synthesis method of 3-bromo-7-chlorodibenzo[b,d]furan for material design in the fields of optics and medicine. DETAILED DESCRIPTION

[0026] A preparation method of 3-bromo-7-chlorodibenzo[b,d]furan comprises the following specific contents: using 2,5-dibromonitrobenzene and 3-chlorophenol as raw materials, under the action of a palladium catalyst, a copper catalyst, a ligand, an additive and a base, a CO coupling and a CC coupling series reaction are carried out in one pot to prepare 3-bromo-7-chlorodibenzo[b,d]furan. For reference, the reaction temperature can be 100-140° C., and the reaction time can be controlled within 24-36 hours;

[0027] After the reaction is completed, the product can be purified by post-treatment. The purification method of the target product in the organic phase is relatively common in the field of chemical synthesis preparation. For reference, the steps may include: adding water and an organic solvent to the reaction system for dilution and extraction after cooling to room temperature, washing the organic liquid, drying, silica gel filtration, desolventizing and recrystallizing to obtain the target product;

[0028] In a preferred embodiment, the molar ratio of 3-chlorophenol, 2,5-dibromonitrobenzene, palladium catalyst, copper catalyst, ligand, additive, and base is 1:(1.05-2.0):(0.005-0.05):(0.05-0.2):(0.01-0.1):(0.1-0.5):(2.0-4.0);

[0029] In the above method, the palladium catalyst is one or more of palladium acetate, tris(dibenzylideneacetone)dipalladium, [1,1'-bis(diphenylphosphino)ferrocene]dichloropalladium, [1,1'-bis(di-tert-butylphosphino)ferrocene]dichloropalladium, [1,1'-bis(di-cyclohexylphosphino)ferrocene]dichloropalladium; the copper catalyst is one or more of copper acetate, copper trifluoromethanesulfonate, copper acetylacetonate, copper bromide, copper chloride, and cuprous iodide; the ligand is an imidazolium salt nitrogen heterocyclic carbene ligand selected from 1,3-bis(2,6-diisopropylphenyl)imidazolium tetrafluoroborate, 1,3-bis(2,6-diisopropylphenyl)imidazolium chloride , one or more of 1,3-bis(2,4,6-trimethylphenyl)imidazole chloride, and 1,3-bis(2,6-diisopropylphenyl)-4,5-dihydroimidazole tetrafluoroborate; the additive is one or more of tetrabutylammonium bromide and tetrabutylammonium chloride, preferably tetrabutylammonium bromide; the base is selected from one or more of potassium phosphate, cesium carbonate, potassium carbonate, sodium tert-butoxide, and potassium tert-butoxide; the organic solvent used for dilution and extraction in the post-treatment is selected from one or more of ethyl acetate, dichloromethane, and xylene; the solvent used for recrystallization is selected from one or more of ethyl acetate, dichloromethane, o-xylene, methanol, ethanol, and n-hexane.

[0030] In addition, as is well known in the art, CO coupling and CC coupling reactions are usually carried out in a solvent, and the reaction solvent may be one or more of N,N-dimethylformamide, N,N-dimethylacetamide, dimethyl sulfoxide, and 1,4-dioxane.

[0031] In order to make the purpose, technical solutions and advantages of the present invention clearer, the above contents of the present invention are further described in detail in conjunction with the embodiments below. However, it is obvious that the following are only a few embodiments of the present invention, and this should not be understood as the scope of the above subject matter of the present invention being limited to the following embodiments.

[0032] Embodiment 1:

[0033] At room temperature, 168.5 g of 2,5-dibromonitrobenzene (98%, 0.6 mol), 64.3 g of 3-chlorophenol (98%, 0.5 mol), 9.2 g of [1,1'-bis(diphenylphosphino)ferrocene]palladium dichloride (98%, 12.5 mmol), 9.1 g of copper acetate (99%, 50 mmol), 10.6 g of 1,3-bis(2,6-diisopropylphenyl)imidazole chloride (98%, 25.0 mmol), and 318.4 g of potassium phosphate (99%, 1.5 mol) were added to the reaction bottle. , 16.2g of tetrabutylammonium bromide (99%, 50mmol) and 1500mL of N,N-dimethylformamide, the temperature was raised to 120°C after the addition, the stirring speed was 550rpm, and the reaction was kept warm for 24h; after the reaction was completed, it was cooled to room temperature and filtered, water and ethyl acetate were added to the filtrate for dilution and extraction, the organic liquid was washed with saturated brine, dried over anhydrous sodium sulfate, and filtered on silica gel, the filtrate was distilled under reduced pressure to obtain a crude product, and 90.1g of 3-bromo-7-chlorodibenzo[b,d]furan was crystallized with a mixed solvent of petroleum ether / ethyl acetate, with a yield of 64.0%.

[0034] Embodiment 2:

[0035] At room temperature, 210.7 g of 2,5-dibromonitrobenzene (98%, 0.75 mol), 64.3 g of 3-chlorophenol (98%, 0.5 mol), 1.9 g of [1,1'-bis(di-cyclohexylphosphino)ferrocene]palladium dichloride (98%, 2.5 mmol), 36.2 g of copper trifluoromethanesulfonate (99%, 0.1 mol), 2.4 g of 1,3-bis(2,6-diisopropylphenyl)imidazolium tetrafluoroborate (97%, 5.0 mmol), 318.4 g of potassium phosphate (99%, 1 .5mol), 16.2g of tetrabutylammonium bromide (99%, 50mmol) and 1500mL of dimethyl sulfoxide, the temperature was raised to 140°C after the addition, the stirring speed was 550rpm, and the reaction was kept warm for 36h; after the reaction was completed, it was cooled to room temperature and filtered, water and ethyl acetate were added to the filtrate for dilution and extraction, the organic liquid was washed with saturated brine, dried over anhydrous sodium sulfate, and filtered with silica gel, the filtrate was desolvated by reduced pressure distillation to obtain a crude product, and 62.3g of 3-bromo-7-chlorodibenzo[b,d]furan was crystallized with a petroleum ether / dichloromethane mixed solvent, and the yield was 44.3%.

[0036] Embodiment 3:

[0037] At room temperature, 168.5 g of 2,5-dibromonitrobenzene (98%, 0.6 mol), 64.3 g of 3-chlorophenol (98%, 0.5 mol), 3.2 g of [1,1'-bis(di-tert-butylphosphino)ferrocene]palladium dichloride (98%, 5.0 mmol), 11.2 g of copper bromide (99%, 50 mmol), 3.4 g of 1,3-bis(2,4,6-trimethylphenyl)imidazole chloride (98%, 10.0 mmol), 325.82 g of cesium carbonate (99%, 1.0 mol) were added to the reaction bottle. ), 32.4 g of tetrabutylammonium bromide (99%, 0.1 mol) and 1500 mL of N,N-dimethylacetamide, the temperature was raised to 130°C after the addition, the stirring speed was 550 rpm, and the reaction was kept warm for 24 hours; after the reaction was completed, it was cooled to room temperature and filtered, water and ethyl acetate were added to the filtrate for dilution and extraction, the organic liquid was washed with saturated brine, dried over anhydrous sodium sulfate, and filtered on silica gel, the filtrate was desolvated by reduced pressure distillation to obtain a crude product, and crystallized with a petroleum ether / dichloromethane mixed solvent to obtain 75.3 g of 3-bromo-7-chlorodibenzo[b,d]furan, with a yield of 53.5%.

[0038] Embodiment 4:

[0039] At room temperature, 168.5 g of 2,5-dibromonitrobenzene (98%, 0.6 mol), 64.3 g of 3-chlorophenol (98%, 0.5 mol), 2.8 g of palladium acetate (98%, 12.5 mmol), 9.1 g of copper acetate (99%, 50 mmol), 4.8 g of 1,3-bis(2,6-diisopropylphenyl)-4,5-dihydroimidazole tetrafluoroborate (97%, 10.0 mmol), 276.4 g of potassium carbonate (99%, 2.0 mol), 16.2 g of tetrabutylammonium bromide (99%, 50 mmol) and 1500 mL of N,N-dimethylformamide, after adding the materials, heat to 120°C, stir at 550 rpm, and keep warm for 24 hours; after the reaction, cool to room temperature and filter, add water and ethyl acetate to the filtrate for dilution and extraction, wash the organic liquid with saturated brine, dry with anhydrous sodium sulfate, filter with silica gel, distill the filtrate under reduced pressure to obtain a crude product, and crystallize with a mixed solvent of petroleum ether / ethyl acetate to obtain 65.0 g of 3-bromo-7-chlorodibenzo[b,d]furan, with a yield of 46.2%.

[0040] Embodiment 5:

[0041] At room temperature, 168.5 g of 2,5-dibromonitrobenzene (98%, 0.6 mol), 64.3 g of 3-chlorophenol (98%, 0.5 mol), 3.7 g of [1,1'-bis(diphenylphosphino)ferrocene]palladium dichloride (98%, 5.0 mmol), 18.2 g of copper acetate (99%, 0.1 mol), 3.4 g of 1,3-bis(2,4,6-trimethylphenyl)imidazole chloride (98%, 10.0 mmol), and 192.2 g of sodium tert-butoxide (99%, 2.0 mol) were added to the reaction bottle. , 32.4 g of tetrabutylammonium bromide (99%, 0.1 mol) and 1500 mL of N,N-dimethylformamide, the temperature was raised to 130°C after the addition, the stirring speed was 550 rpm, and the reaction was kept warm for 36 hours; after the reaction was completed, it was cooled to room temperature and filtered, water and ethyl acetate were added to the filtrate for dilution and extraction, the organic liquid was washed with saturated brine, dried over anhydrous sodium sulfate, and filtered on silica gel, the filtrate was distilled under reduced pressure to obtain a crude product, and 47.3 g of 3-bromo-7-chlorodibenzo[b,d]furan was crystallized with a mixed solvent of petroleum ether / ethyl acetate, with a yield of 33.6%.

[0042] Embodiment 6:

[0043] At room temperature, 168.5 g of 2,5-dibromonitrobenzene (98%, 0.6 mol), 64.3 g of 3-chlorophenol (98%, 0.5 mol), 3.7 g of [1,1'-bis(diphenylphosphino)ferrocene]palladium dichloride (98%, 5.0 mmol), 9.1 g of copper acetate (99%, 50.0 mmol), 3.4 g of 1,3-bis(2,4,6-trimethylphenyl)imidazole chloride (98%, 10.0 mmol), 318.4 g of potassium phosphate (99%, 1.5 mol) were added to the reaction bottle. l), 32.4g of tetrabutylammonium bromide (99%, 50.0mmol) and 1000mL of dimethyl sulfoxide, after adding the materials, the temperature was raised to 120°C, the stirring speed was 550rpm, and the reaction was kept warm for 24h; after the reaction was completed, it was cooled to room temperature and filtered, water and ethyl acetate were added to the filtrate for dilution and extraction, the organic liquid was washed with saturated brine, dried over anhydrous sodium sulfate, and filtered with silica gel, the filtrate was desolvated by reduced pressure distillation to obtain a crude product, and 86.7g of 3-bromo-7-chlorodibenzo[b,d]furan was crystallized with a mixed solvent of petroleum ether / ethyl acetate, and the yield was 61.6%.

[0044] The above are only preferred embodiments of the present invention, but the protection scope of the present invention is not limited thereto. Any changes or substitutions that can be easily thought of by a person skilled in the art within the technical scope disclosed by the present invention should be included in the protection scope of the present invention. Therefore, the protection scope of the present invention should be based on the protection scope defined by the claims.

[0045] The matters not described in detail in the present invention are all known technologies to those skilled in the art.

Claims

1. A method for preparing 3-bromo-7-chlorodibenzo[b,d]furan, characterized in that: The specific contents include: 2,5-dibromonitrobenzene and 3-chlorophenol are used as raw materials, and 3-bromo-7-chlorodibenzo[b,d]furan is prepared in one pot through CO coupling and CC coupling tandem reactions under the action of palladium catalyst, copper catalyst, ligand, additive and base.

2. A method for preparing 3-bromo-7-chlorodibenzo[b,d]furan according to claim 1, characterized in that: The molar ratio of the 3-chlorophenol, 2,5-dibromonitrobenzene, palladium catalyst, copper catalyst, ligand, additive and base is 1:(1.05-2.0):(0.005-0.05):(0.05-0.2):(0.01-0.1):(0.1-0.5):(2.0-4.0).

3. A method for preparing 3-bromo-7-chlorodibenzo[b,d]furan according to claim 1 or 2, characterized in that: The reaction temperature is 100-140° C., and the reaction time is 24-36 hours.

4. A method for preparing 3-bromo-7-chlorodibenzo[b,d]furan according to claim 1 or 2, characterized in that: The palladium catalyst is one or more of palladium acetate, tris(dibenzylideneacetone)dipalladium, [1,1'-bis(diphenylphosphino)ferrocene]palladium dichloride, [1,1'-bis(di-tert-butylphosphino)ferrocene]palladium dichloride, [1,1'-bis(di-cyclohexylphosphino)ferrocene]palladium dichloride; the copper catalyst is one or more of copper acetate, copper trifluoromethanesulfonate, copper acetylacetonate, copper bromide, copper chloride, and cuprous iodide.

5. A method for preparing 3-bromo-7-chlorodibenzo[b,d]furan according to claim 1 or 2, characterized in that: The ligand is an imidazolium salt nitrogen heterocyclic carbene ligand, selected from one or more of 1,3-bis(2,6-diisopropylphenyl)imidazolium tetrafluoroborate, 1,3-bis(2,6-diisopropylphenyl)imidazolium chloride, 1,3-bis(2,4,6-trimethylphenyl)imidazolium chloride, and 1,3-bis(2,6-diisopropylphenyl)-4,5-dihydroimidazolium tetrafluoroborate.

6. A method for preparing 3-bromo-7-chlorodibenzo[b,d]furan according to claim 1 or 2, characterized in that: The additive is one or more of tetrabutylammonium bromide and tetrabutylammonium chloride.

7. A method for preparing 3-bromo-7-chlorodibenzo[b,d]furan according to claim 1 or 2, characterized in that: The base is selected from one or more of potassium phosphate, cesium carbonate, potassium carbonate, sodium tert-butoxide, and potassium tert-butoxide.

8. The method for preparing 3-bromo-7-chlorodibenzo[b,d]furan according to claim 1, characterized in that: The reaction is carried out in a solvent, and the solvent is one or more of N,N-dimethylformamide, N,N-dimethylacetamide, dimethyl sulfoxide, and 1,4-dioxane.

9. The method for preparing 3-bromo-7-chlorodibenzo[b,d]furan according to claim 1, characterized in that: After the reaction is completed, the product is purified by post-processing, and the steps include: cooling to room temperature, adding water and an organic solvent to the reaction system for dilution and extraction, washing the organic liquid, drying, filtering with silica gel, desolventizing, and recrystallizing to obtain the product.

10. A method for preparing 3-bromo-7-chlorodibenzo[b,d]furan according to claim 9, characterized in that: The organic solvent used for dilution and extraction in the post-treatment is selected from one or more of ethyl acetate, dichloromethane and xylene; the solvent used for recrystallization is selected from one or more of ethyl acetate, dichloromethane, o-xylene, methanol, ethanol and n-hexane.

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