Preparation method of organic luminescent material intermediate 1-bromodibenzofuran

Abstract

The invention relates to the technical field of preparation of organic luminescent material intermediates, in particular to a preparation method of an organic luminescent material intermediate 1-bromodibenzofuran, which comprises the following steps: under inert gas and alkaline conditions, o-fluorophenol and o-fluoronitrobenzene react to obtain an intermediate A-1; carrying out reduction reaction on the intermediate A-1 under the action of a catalyst and a reducing agent to obtain an intermediate A-2, namely 2-fluorophenyl-2 '-aminophenyl ether; under an acidic condition, sodium nitrite and the intermediate A-2 are subjected to a diazotization reaction to generate diazonium salt, and then the diazonium salt and potassium iodide are subjected to a nucleophilic aromatic substitution reaction to generate an intermediate A-3, namely 2-fluorophenyl-2 '-iodophenyl ether; and reacting the intermediate A-3 with n-butyllithium to generate 1-lithium dibenzofuran, and reacting with a bromination reagent to obtain 1-bromo dibenzofuran. The preparation method has the advantages of cheap and easily available raw materials, short route, simple process and high yield, and is suitable for industrial production.

Description

Technical Field

[0001] The present invention relates to a preparation method of an organic light-emitting material intermediate 1-bromodibenzofuran, and belongs to the technical field of the preparation of organic light-emitting material intermediates. Background Art

[0002] As a new type of flat panel display technology, organic electroluminescent devices (OLEDs) have been widely used in the display field in recent years due to their advantages of self-luminescence, wide viewing angle, high contrast, bright color, fast response speed, low power consumption, light weight, flexibility and bendability. Organic electroluminescent materials are the key components to realize OLEDs. Luminescent materials containing dibenzofuran structural units can be applied in the hole transport layer, electron transport layer and light-emitting layer of OLEDs, which can effectively improve the optoelectronic performance of OLED devices. 1-Bromodibenzofuran is a dibenzofuran derivative and an important intermediate for introducing dibenzofuran units in the synthesis process of organic light-emitting materials.

[0003] There are many technical problems in the existing methods for synthesizing 1-bromodibenzofuran. For example, the yield is low, the route is long, the raw materials used are expensive, resulting in high costs, the reaction types involved are complex and difficult to synthesize, high-risk chemicals are used in the reaction process, the risk is high, the equipment requirements are harsh, the post-treatment process is cumbersome, the production cycle is long, and a large amount of waste gas and waste water are generated, seriously polluting the environment, all of which are not conducive to industrial production.

[0004] Currently, there are mainly the following two synthesis methods for 1-bromodibenzofuran: The patent application with the publication number WO2015169412A1 reported a synthesis route for preparing 1-bromodibenzofuran using 2-bromo-6-fluoroiodobenzene and 2-methoxyphenylboronic acid as starting materials. The specific process is as follows: First, the substituted biphenyl is obtained through Suzuki-Miyaura coupling, then demethylation is carried out under the action of boron tribromide, and finally HF is eliminated intramolecularly to obtain 1-bromodibenzofuran. The starting materials and the precious metal catalyst bis(triphenylphosphine)palladium dichloride used in this route are expensive, and the synthesis route has a high cost. Moreover, the boron tribromide used is a dangerous chemical, which has a strong stimulating effect on human tissues, its vapor is highly toxic, and it has strong corrosiveness, with relatively large potential safety hazards. During the post-treatment process of adding water, boron tribromide generates boric acid and hydrogen bromide, which causes certain damage to the equipment. The waste gas and waste liquid generated during the reaction process are difficult to treat, and the risk of the reaction is relatively high.

[0005] The patent with the publication number CN115947704B discloses a preparation method of an organic light-emitting material intermediate 1-bromodibenzofuran. Using 1,4-cyclohexanediol as the starting material, it undergoes an O-acylation reaction of alcohol with an acyl chloride compound to obtain a 4-hydroxycyclohexyl ester compound. The 4-hydroxycyclohexyl ester compound is oxidized by TEMPO to obtain a ketone, and then a chlorination reaction at the α-position of the carbonyl group is carried out with trichloroisocyanuric acid to finally generate an α,α-dichlorocyclohexanone compound. The α,α-dichlorocyclohexanone compound and 1,3-cyclohexanedione undergo a Feist-Benary furan synthesis reaction to construct a furan ring, and then an elimination reaction occurs under acidic conditions to obtain 3,4-dihydrodibenz[b,d]furan-1(2H)-one. 3,4-Dihydrodibenz[b,d]furan-1(2H)-one is dehydrogenated by chloranil to dibenz[b,d]furan-1-ol. Finally, this compound undergoes a halogen displacement reaction of the hydroxyl group under the action of phosphorus tribromide to generate the target product 1-bromodibenzofuran. This synthesis route has a long number of steps, and the reaction time for each step is long, up to 18 h at most. The post-treatment process is complex and cumbersome, resulting in a low total product yield, only 25% - 28%, and it is not suitable for industrial production.

[0006] Therefore, it is of great significance to develop a synthesis method of 1-bromodibenzofuran with low cost, short route, simple process, high yield, and suitable for industrial production. Summary of the Invention

[0007] In view of the deficiencies in the prior art, the present invention provides a preparation method of an organic light-emitting material intermediate 1-bromodibenzofuran. The raw materials of the preparation method are cheap and easily available, the route is short, the process is simple, the yield is high, and it is suitable for industrial production.

[0008] The technical solution of the present invention to solve the above technical problems is as follows: A preparation method of an organic light-emitting material intermediate 1-bromodibenzofuran, and the preparation method is as follows: S1. Under an inert gas and in a basic condition, o-fluorophenol reacts with o-fluoronitrobenzene to obtain intermediate A-1, that is, 2-fluorophenyl-2'-nitrophenyl ether; S2. Under an inert gas, intermediate A-1 undergoes a reduction reaction under the action of a catalyst and a reducing agent to obtain intermediate A-2, that is, 2-fluorophenyl-2'-aminophenyl ether; S3. Under an inert gas and in an acidic condition, sodium nitrite and intermediate A-2 undergo a diazotization reaction to form a diazonium salt, and then a nucleophilic aromatic substitution reaction with potassium iodide to obtain intermediate A-3, that is, 2-fluorophenyl-2'-iodophenyl ether; S4. Under an inert gas, intermediate A-3 reacts with n-butyllithium to generate 1-lithiodibenzofuran, and then undergoes an electrophilic aromatic substitution reaction with a brominating reagent to obtain 1-bromodibenzofuran.

[0009] Further, in step S1, the base used is at least one of cesium carbonate, potassium carbonate, and sodium carbonate; The molar ratio of o-fluoronitrobenzene, o-fluorophenol, and the base is 1: (1.0 - 1.3): (2 - 3).

[0010] Further, in step S1, the reaction temperature is 80 - 90 °C.

[0011] Further, in step S2, the catalyst is ferric chloride hexahydrate, the carrier is activated carbon, and the reducing agent is hydrazine hydrate; The molar ratio of intermediate A-1, ferric chloride hexahydrate, activated carbon, and hydrazine hydrate is 1: (0.2 - 0.5): (6 - 9): (8 - 12.5).

[0012] Further, the solvent used in step S2 is toluene and ethanol, and the reaction process is a reflux reaction.

[0013] Further, in step S3, sulfuric acid is used to provide an acidic condition; The molar ratio of intermediate A-2, sulfuric acid, sodium nitrite, and potassium iodide is 1: (6 - 12): (1 - 1.2): (1 - 1.3).

[0014] Further, in step S3, the temperature conditions for the diazotization reaction and the nucleophilic aromatic substitution reaction are 0 - 5 °C.

[0015] Further, in step S4, the brominating reagent is at least one of 1,2-dibromoethane, 1,2-dibromotetrafluoroethane, and NBS.

[0016] Further, in step S4, the molar ratio of intermediate A-3, n-butyllithium, and the brominating reagent is 1: (2 - 2.5): (1 - 3).

[0017] Further, in step S4, the temperature condition for the reaction of intermediate A-3 with n-butyllithium is -35 to -30 °C; the temperature condition for the electrophilic aromatic substitution reaction of 1-lithiobenzodifuran with the brominating reagent is -80 to -75 °C.

[0018] The beneficial effects of the present invention are: The preparation method of the present invention has cheap and easily available raw materials, a short route, a high product yield, a green and environmentally friendly production process, and is more suitable for industrial production. Moreover, the preparation method of the present invention uses the method of benzyne to synthesize intermediate 1-bromobenzodifuran, which is a new synthesis method.

[0019] The preparation method of the present invention uses cheap and easily available o-fluoronitrobenzene and o-fluorophenol as starting materials. Almost no purification is required in the intermediate steps, the loss of intermediate products is small, the product yield is high, and the total yield can reach more than 70%, thus greatly reducing the cost.

[0020] The synthesis route of the preparation method of the present invention is short, and the synthesis and post-treatment processes are simple and efficient. There is no use of highly polluting materials and generation of high-risk wastes. The production process is efficient and environmentally friendly, greatly shortening the production cycle, improving the production efficiency, and being conducive to industrial production. Description of the Drawings

[0021] Figure 1 The gas chromatogram of 1-bromodibenzofuran prepared in Example 1; Figure 2 The gas chromatogram of 1-bromodibenzofuran prepared in Example 1 by GC-MS; Figure 3 The mass spectrum of 1-bromodibenzofuran prepared in Example 1 by GC-MS. Detailed Description of the Invention

[0022] The following is a detailed description of the specific implementation manners of the present invention. The present invention can be implemented in many other ways different from those described herein. Those skilled in the art can make similar improvements without departing from the connotation of the present invention. Therefore, the present invention is not limited by the specific embodiments disclosed.

[0023] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by those skilled in the technical field to which the present invention belongs. The terms used are only for describing specific implementation manners and do not limit the present invention.

[0024] A preparation method of an organic light-emitting material intermediate 1-bromodibenzofuran, the preparation method comprising: S1. Under an inert gas and in a basic condition, o-fluorophenol reacts with o-fluoronitrobenzene to obtain intermediate A-1, namely 2-fluorophenyl-2'-nitrophenyl ether; S2. Under an inert gas, intermediate A-1 undergoes a reduction reaction under the action of a catalyst and a reducing agent to obtain intermediate A-2, namely 2-fluorophenyl-2'-aminophenyl ether; S3. Under an inert gas and in an acidic condition, sodium nitrite and intermediate A-2 undergo a diazotization reaction to form a diazonium salt, and then undergo a nucleophilic aromatic substitution reaction with potassium iodide to obtain intermediate A-3, namely 2-fluorophenyl-2'-iodophenyl ether; S4. Under inert gas, intermediate A-3 simultaneously undergoes an iodine-lithium exchange reaction and a deprotonation reaction with n-butyllithium to form the active intermediate benzyne lithium salt. Then, it immediately undergoes an intramolecular nucleophilic addition substitution reaction to form the active intermediate 1-lithiodibenzofuran, which then undergoes an electrophilic aromatic substitution reaction with a brominating reagent to obtain the target product 1-bromodibenzofuran.

[0025] The process principle of the preparation method is as follows: 。

[0026] Specifically, in step S1, the base used is at least one of cesium carbonate, potassium carbonate, and sodium carbonate; The molar ratio of the o-fluoronitrobenzene, o-fluorophenol, and the base is 1:(1.0 - 1.3):(2 - 3).

[0027] Preferably, the base is potassium carbonate; the molar ratio of the o-fluoronitrobenzene, o-fluorophenol, and the base is 1:1.05:2.

[0028] More specifically, in the embodiment of the present invention, the solvent used in step S1 is N,N-dimethylformamide.

[0029] Specifically, in step S1, the reaction temperature is 80 - 90 °C.

[0030] Specifically, in step S2, the catalyst is ferric chloride hexahydrate, the carrier is activated carbon, and the reducing agent is hydrazine hydrate; The molar ratio of intermediate A-1, ferric chloride hexahydrate, activated carbon, and hydrazine hydrate is 1:(0.2 - 0.5):(6 - 9):(8 - 12.5).

[0031] Preferably, the molar ratio of intermediate A-1, ferric chloride hexahydrate, activated carbon, and hydrazine hydrate is 1:0.35:7.8:10.

[0032] Specifically, the solvent used in step S2 is toluene and ethanol, and the reaction process is a reflux reaction.

[0033] Specifically, in step S3, sulfuric acid is used to provide an acidic condition; The molar ratio of intermediate A-2, sulfuric acid, sodium nitrite, and potassium iodide is 1:(6 - 12):(1 - 1.2):(1 - 1.3).

[0034] Preferably, the molar ratio of intermediate A-2, sulfuric acid, sodium nitrite, and potassium iodide is 1:10:1.1:1.2.

[0035] More specifically, in the embodiment of the present invention, the solvent used in step S3 is ethyl acetate and water.

[0036] Specifically, in step S3, the temperature conditions for the diazotization reaction and the nucleophilic aromatic substitution reaction are 0 to 5 °C.

[0037] Specifically, in step S4, the brominating reagent is at least one of 1,2-dibromoethane, 1,2-dibromotetrafluoroethane, and NBS.

[0038] Preferably, in step S4, the brominating reagent is 1,2-dibromoethane.

[0039] Specifically, in step S4, the molar ratio of intermediate A-3, n-butyllithium, and the brominating reagent is 1:(2 - 2.5):(1 - 3).

[0040] Preferably, in step S4, the molar ratio of intermediate A-3, n-butyllithium, and the brominating reagent is 1:2.5:2.

[0041] Specifically, in step S4, the temperature conditions for the reaction of intermediate A-3 with n-butyllithium are -35 to -30 °C; the temperature conditions for the electrophilic aromatic substitution reaction of 1-lithiobenzodifuran with the brominating reagent are -80 to -75 °C.

[0042] More specifically, in the embodiment of the present invention, the solvent used in step S4 is tetrahydrofuran.

[0043] Example 1 S1. Synthesis of 2-fluorophenyl-2'-nitrophenyl ether (intermediate A-1): Under nitrogen protection, add 239.8 g of o-fluoronitrobenzene, 480 mL of DMF, and 469 g of potassium carbonate to a three-necked flask, heat to 85 °C, control the temperature at 80 - 90 °C, and dropwise add a DMF solution of o-fluorophenol (200 g of o-fluorophenol dissolved in 480 mL of DMF). After the addition is complete, time and control the temperature at 85 °C for reaction for 3.5 h. After the reaction is complete, concentrate under reduced pressure until no solvent comes out basically. After cooling, add 1981 mL of toluene and 480 mL of water to the flask, heat to dissolve and clarify, let it stand for liquid separation. After the organic phase is washed to neutrality with water, it is directly put into the next step. The yield is 100%, and the purity is 98.5%.

[0044] S2. Synthesis of 2-fluorophenyl-2'-aminophenyl ether (intermediate A-2): Under nitrogen protection, add a 1981 mL toluene solution containing 396.2 g of intermediate A-1 to a three-necked flask, add 160.7 g of ferric chloride hexahydrate, 159 g of activated carbon, and 594 mL of ethanol, heat to reflux, and keep refluxing while dropwise adding 1062 g of hydrazine hydrate. After the addition is complete, time the reaction for 1.5 h. After the reaction is complete, add 690 mL of water dropwise to the system, then cool to room temperature and filter. The filtrate is allowed to stand for liquid separation, and the organic phase is washed to neutrality with water and concentrated to dryness under reduced pressure to obtain intermediate A-2. The yield is 100%, and the purity is 96.4%.

[0045] S3. Synthesis of 2-fluorophenyl-2'-iodophenyl ether (Intermediate A-3): Under nitrogen protection, 849 mL of water was added to a 10 L three-necked flask, and 1698 g of concentrated sulfuric acid was added dropwise while controlling the temperature below 50 °C. After the addition was completed, an ethyl acetate solution of Intermediate A-2 (345.2 g of Intermediate A-2 dissolved in 690 mL of ethyl acetate) was continuously added dropwise. After the addition was completed, the temperature was lowered to 0 °C, and an aqueous solution of sodium nitrite (128.9 g of sodium nitrite dissolved in 516 mL of water) was added dropwise. After the addition was completed, the mixture was stirred at 0 °C for 1 h, and then an aqueous solution of potassium iodide (338.4 g of potassium iodide dissolved in 339 mL of water) was added dropwise at 0 °C. After the addition was completed, the reaction was timed for 1.5 h. After the reaction was completed, 2668 mL of toluene was added and stirred for 30 min. The mixture was allowed to stand for liquid separation, and the organic phase was washed once with a 10% aqueous solution of sodium bisulfite and then washed with water until neutral. After concentration to dryness under reduced pressure, distillation was carried out under reduced pressure to obtain 458.9 g of Intermediate A-3, with a yield of 86% and a purity of 98%.

[0046] S4. Synthesis of the target compound (1-bromodibenzofuran) Under nitrogen protection, 1461 mL of n-butyllithium (a 2.5 M n-butyllithium n-hexane solution) was added to a 10 L three-necked flask, and the temperature was lowered to -35 °C. A tetrahydrofuran solution of Intermediate A-3 (458.9 g of Intermediate A-3 dissolved in 2295 mL of tetrahydrofuran) was added dropwise. After the addition was completed, the mixture was stirred while maintaining the temperature for 2.5 h. The temperature was lowered to -80 °C, and a THF solution of 1,2-dibromoethane (548.9 g of 1,2-dibromoethane dissolved in 1098 mL of THF) was added dropwise. After the addition was completed, the mixture was stirred while maintaining the temperature for 1 h, and then naturally warmed to about 0 °C. While controlling the temperature below 30 °C, a 12% aqueous solution of dilute hydrochloric acid was added dropwise to the system to adjust the pH to 1-2. Then, 1805 mL of toluene was added and stirred for 15 min. After standing for liquid separation, the organic phase was washed with water until neutral, passed through a column, concentrated to dryness under reduced pressure, and then distilled under reduced pressure. Recrystallization was carried out with methanol to obtain 299.6 g of the target compound (1-bromodibenzofuran), with a yield of 83% and a purity of 99.8%. The gas chromatogram is as shown in Figure 1 shown, and the detection data of the gas chromatography are shown in Table 1 below. The total yield of 1-bromodibenzofuran is 71.38%, and the GC-MS combined analysis spectrum of the target compound 1-bromodibenzofuran is as shown in Figures 2 - 3 shown.

[0047] Table 1 Detection data of gas chromatography

[0048] Example 2 S1. Synthesis of 2-fluorophenyl-2'-nitrophenyl ether (Intermediate A-1): Under nitrogen protection, 239.8 g of 2-fluoronitrobenzene, 480 mL of DMF, and 540 g of sodium carbonate were added to a three-necked flask. The temperature was raised to 80 °C and maintained at 80 °C. A DMF solution of 2-fluorophenol (246 g of 2-fluorophenol dissolved in 480 mL of DMF) was added dropwise. After the addition was complete, the reaction was carried out at 80 °C for 4 h while timing. After the reaction was completed, the mixture was concentrated under reduced pressure until no solvent was distilled out. After cooling, 1982 mL of toluene and 480 mL of water were added to the flask. The temperature was raised to dissolve until clear, and then allowed to stand for liquid separation. After the organic phase was washed with water until neutral, it was directly fed into the next step. The yield was 100% and the purity was 98.4%.

[0049] S2. Synthesis of 2-fluorophenyl-2'-aminophenyl ether (Intermediate A-2): Under nitrogen protection, 1982 mL of a toluene solution containing Intermediate A-1 was added to a three-necked flask. 94 g of ferric chloride hexahydrate, 123 g of activated carbon, and 594 mL of ethanol were added, and the temperature was raised to reflux. While maintaining reflux, 845 g of hydrazine hydrate was added dropwise. After the addition was complete, the reaction was carried out for 2 h while timing. After the reaction was completed, 690 mL of water was added dropwise to the system, and then the temperature was lowered to room temperature and filtered. The filtrate was allowed to stand for liquid separation. The organic phase was washed with water until neutral and concentrated to dryness under reduced pressure to obtain Intermediate A-2. The yield was 100% and the purity was 96.1%.

[0050] S3. Synthesis of 2-fluorophenyl-2'-iodophenyl ether (Intermediate A-3): Under nitrogen protection, 845 mL of water was added to a 10 L three-necked flask. Concentrated sulfuric acid (1000 g) was added dropwise while controlling the temperature below 50 °C. After the addition was complete, an ethyl acetate solution of Intermediate A-2 (Intermediate A-2 obtained in Step S2 dissolved in 690 mL of ethyl acetate) was added dropwise. After the addition was complete, the temperature was lowered to 5 °C, and an aqueous solution of sodium nitrite (118 g of sodium nitrite dissolved in 515 mL of water) was added dropwise. After the addition was complete, the mixture was stirred at 5 °C for 1 h, and then an aqueous solution of potassium iodide (283 g of potassium iodide dissolved in 335 mL of water) was added dropwise while controlling the temperature at 5 °C. After the addition was complete, the reaction was carried out for 1 h while timing. After the reaction was completed, 2668 mL of toluene was added and stirred for 30 min. The mixture was allowed to stand for liquid separation. The organic phase was washed once with a 10% aqueous solution of sodium bisulfite and then washed with water until neutral. After concentration to dryness under reduced pressure, it was distilled under reduced pressure to obtain 464.1 g of Intermediate A-3. The yield was 87% and the purity was 98.2%.

[0051] S4. Synthesis of the target compound (1-bromodibenzofuran) Under nitrogen protection, 1190 mL of n-butyllithium (n-butyllithium hexane solution with a concentration of 2.5 M) was added to a 10 L three-necked flask. The temperature was lowered to -30 °C, and a tetrahydrofuran solution of intermediate A-3 (the intermediate A-3 obtained in step S4 was dissolved in 2295 mL of tetrahydrofuran) was added dropwise. After the addition was completed, the mixture was stirred at a constant temperature for 2 h. The temperature was lowered to -75 °C, and a THF solution of 1,2-dibromoethane (840 g of 1,2-dibromoethane was dissolved in 1200 mL of THF) was added dropwise. After the addition was completed, the mixture was stirred at a constant temperature for 1 h, and then naturally warmed to about 0 °C. While controlling the temperature below 30 °C, 12% dilute hydrochloric acid aqueous solution was added dropwise to the system to adjust the pH to 1 - 2. Then, 1805 mL of toluene was added and stirred for 15 min. After standing and separating the liquid, the organic phase was washed with water until neutral, passed through a column, concentrated under reduced pressure to dryness, and then distilled under reduced pressure. Recrystallization was carried out with methanol to obtain 314.1 g of the target compound (1-bromodibenzofuran), with a yield of 86% and a purity of 99.6%. The total yield of 1-bromodibenzofuran was 74.82%.

[0052] Example 3 S1. Synthesis of 2-fluorophenyl-2'-nitrophenyl ether (intermediate A-1): Under nitrogen protection, 239.8 g of o-fluoronitrobenzene, 680 mL of DMF, and 1110 g of cesium carbonate were added to a three-necked flask. The temperature was raised to 90 °C and controlled at 90 °C. A DMF solution of o-fluorophenol (192 g of o-fluorophenol was dissolved in 500 mL of DMF) was added dropwise. After the addition was completed, the reaction was carried out at 90 °C for 3 h while timing. After the reaction was completed, the mixture was concentrated under reduced pressure until almost no solvent was distilled out. After cooling, 1990 mL of toluene and 500 mL of water were added to the flask. The temperature was raised to dissolve until clear, and then left to stand for liquid separation. After the organic phase was washed with water until neutral, it was directly used in the next step. The yield was 100% and the purity was 98.1%.

[0053] S2. Synthesis of 2-fluorophenyl-2'-aminophenyl ether (intermediate A-2): Under nitrogen protection, 229 g of ferric chloride hexahydrate, 183 g of activated carbon, and 600 mL of ethanol were added to a three-necked flask containing 1990 mL of toluene solution of intermediate A-1. The temperature was raised to reflux, and 681 g of hydrazine hydrate was added dropwise while maintaining reflux. After the addition was completed, the reaction was carried out for 1 h while timing. After the reaction was completed, 690 mL of water was added dropwise to the system, and then the temperature was lowered to room temperature and filtered. The filtrate was left to stand for liquid separation. The organic phase was washed with water until neutral and concentrated to dryness under reduced pressure to obtain intermediate A-2. The yield was 100% and the purity was 96.2%.

[0054] S3. Synthesis of 2-fluorophenyl-2'-iodophenyl ether (intermediate A-3): Under nitrogen protection, 880 mL of water was added to a 10 L three-necked flask, and concentrated sulfuric acid (1997 g) was added dropwise while controlling the temperature below 50 °C. After the addition was completed, an ethyl acetate solution of intermediate A-2 (the intermediate A-2 obtained in step S2 was dissolved in 690 mL of ethyl acetate) was added dropwise continuously. After the addition was completed, the temperature was lowered to 3 °C, and an aqueous solution of sodium nitrite (140 g of sodium nitrite dissolved in 520 mL of water) was added dropwise. After the addition was completed, the mixture was stirred at 3 °C for 1 h, and then an aqueous solution of potassium iodide (366 g of potassium iodide dissolved in 339 mL of water) was added dropwise while controlling the temperature at 3 °C. After the addition was completed, the reaction was timed for 1.5 h. After the reaction was completed, 2668 mL of toluene was added and stirred for 30 min. The mixture was allowed to stand and separated. The organic phase was washed once with a 10% aqueous solution of sodium bisulfite and then washed with water until neutral. After concentration under reduced pressure to dryness, vacuum distillation was carried out to obtain 474.7 g of intermediate A-3, with a yield of 89% and a purity of 98.0%.

[0055] S4. Synthesis of the target compound (1-bromodibenzofuran) Under nitrogen protection, 1255 mL of n-butyllithium (a 2.5 M solution of n-butyllithium in n-hexane) was added to a 10 L three-necked flask, and the temperature was lowered to -32 °C. An ethyl acetate solution of intermediate A-3 (the intermediate A-3 obtained in step S4 was dissolved in 2295 mL of ethyl acetate) was added dropwise. After the addition was completed, the mixture was stirred at the same temperature for 3 h. Then the temperature was lowered to -78 °C, and a THF solution of 1,2-dibromotetrafluoroethane (395 g of 1,2-dibromotetrafluoroethane dissolved in 1090 mL of THF) was added dropwise. After the addition was completed, the mixture was stirred at the same temperature for 1 h, and then naturally warmed to about 0 °C. While controlling the temperature below 30 °C, a 12% aqueous solution of dilute hydrochloric acid was added dropwise to the system to adjust the pH to 1-2. Then 1805 mL of toluene was added and stirred for 15 min. The mixture was allowed to stand and separated. The organic phase was washed with water until neutral, passed through a column, concentrated under reduced pressure to dryness, and then vacuum distilled. Recrystallization was carried out with methanol to obtain 328.7 g of the target compound (1-bromodibenzofuran), with a yield of 88% and a purity of 99.2%. The total yield of 1-bromodibenzofuran was 78.32%.

[0056] Comparative Example 1 1-Bromodibenzofuran was prepared by the same method as in Example 2, except that: the reaction temperature in step S1 was increased, and the reaction temperature in step S1 in this Comparative Example 1 was 150 °C (higher than the temperature range defined in the present invention).

[0057] The purity of intermediate A-1 in step S1 in this Comparative Example 1 was 87%; The total yield of 1-bromodibenzofuran was 58.73% and the purity was 98.4%.

[0058] It can be seen from the comparison of the experimental results of Example 2 and Comparative Example 1 that: if the reaction temperature is increased in step S1, the purity of intermediate A-1 will decrease significantly. Because after the reaction temperature is increased, the intermediate A-1 generated in the system will continue to react with o-fluorophenol, and o-fluorophenol will also react with itself, resulting in a decrease in the product purity.

[0059] Comparative Example 2 1-bromodibenzofuran was prepared by the same method as in Example 2, except that: the amount of hydrazine hydrate added in step S2 was reduced. In step S2 of this Comparative Example 2, the molar ratio of intermediate A-1 to hydrazine hydrate was 1:4.

[0060] In this Comparative Example 2, the total yield of 1-bromodibenzofuran was 61.33% and the purity was 97.9%.

[0061] It can be seen from the comparison of the experimental results of Example 2 and Comparative Example 2 that: if the amount of hydrazine hydrate added in step S2 is reduced, the yield of the target compound 1-bromodibenzofuran will decrease significantly. Because the reducing agent is insufficient, resulting in incomplete reaction of the raw materials, thereby reducing the conversion rate and yield.

[0062] Comparative Example 3 1-bromodibenzofuran was prepared by the same method as in Example 2, except that: the amount of sulfuric acid added in step S3 was reduced. In step S3 of this Comparative Example 3, the molar ratio of intermediate A-2 to sulfuric acid was 1:3.

[0063] In this Comparative Example 3, the total yield of 1-bromodibenzofuran was 61.01% and the purity was 99.0%.

[0064] It can be seen from the comparison of the experimental results of Example 3 and Comparative Example 3 that: if the amount of sulfuric acid added in step S3 is reduced, the yield of the target compound 1-bromodibenzofuran will decrease significantly. Because the reduction of the amount of sulfuric acid will make the diazonium salt unstable and easy to decompose, resulting in a decrease in the yield.

[0065] Comparative Example 4 1-bromodibenzofuran was prepared by the same method as in Example 2, except that: the amount of n-butyllithium added in step S4 was reduced. In step S4 of this Comparative Example 4, the molar ratio of intermediate A-3 to n-butyllithium was 1:1.2.

[0066] In this Comparative Example 4, the total yield of 1-bromodibenzofuran was 39.23% and the purity was 98.3%.

[0067] It can be seen from the comparison of the experimental results of Example 3 and Comparative Example 4 that: if the amount of n-butyllithium added in step S4 is reduced, the yield of the target compound 1-bromodibenzofuran will decrease significantly.

[0068] Comparative Example 5 1-Bromodibenzofuran was prepared by the same method as in Example 2, except that: the reaction temperature of n-butyllithium and intermediate A-3 in Step S4 was lowered. In Step S4 of this Comparative Example 5, the reaction temperature of n-butyllithium and intermediate A-3 was -50 °C (lower than the temperature range defined in the present invention).

[0069] In this Comparative Example 5, the total yield of 1-bromodibenzofuran was 65.84% and the purity was 98.8%.

[0070] It can be seen from the comparison of the experimental results of Example 3 and Comparative Example 5 that: if the reaction temperature of n-butyllithium and intermediate A-3 in Step S4 is lowered, the yield of the target compound 1-bromodibenzofuran will decrease significantly, because too low reaction temperature will cause the formation of benzyne to be slow or impossible, ultimately leading to a decrease in yield.

[0071] Comparative Example 6 1-Bromodibenzofuran was prepared by the same method as in Example 2, except that: the reaction temperature of n-butyllithium and intermediate A-3 in Step S4 was raised. In Step S4 of this Comparative Example 6, the reaction temperature of n-butyllithium and intermediate A-3 was -20 °C (higher than the temperature range defined in the present invention).

[0072] In this Comparative Example 6, the total yield of 1-bromodibenzofuran was 60.96% and the purity was 98.2%.

[0073] It can be seen from the comparison of the experimental results of Example 3 and Comparative Example 6 that: if the reaction temperature of n-butyllithium and intermediate A-3 in Step S4 is raised, the yield of the target compound 1-bromodibenzofuran will decrease significantly, because if the reaction temperature in the system is too high, the benzyne intermediate is unstable and easily decomposes, ultimately leading to a decrease in the product yield.

[0074] The technical features of the above-described embodiments can be combined arbitrarily. For the sake of brevity of description, all possible combinations of the technical features in the above embodiments are not exhaustively listed. However, as long as there is no contradiction in the combination of these technical features, it should be considered as the scope recorded in this specification.

[0075] For those of ordinary skill in the art, without departing from the concept of the present invention, several modifications and improvements can still be made, and these all belong to the protection scope of the present invention. The protection scope of the present invention shall be subject to the appended claims.

Claims

1. A method for preparing 1-bromodibenzofuran, an organic luminescent material intermediate, characterized in that: The preparation method is: S1. Under an inert gas and alkaline conditions, o-fluorophenol and o-fluoronitrobenzene react to obtain intermediate A-1, i.e. 2-fluorophenyl-2'-nitrophenyl ether; S2, under inert gas, intermediate A-1 is subjected to reduction reaction under the action of a catalyst and a reducing agent to obtain intermediate A-2, which is 2-fluorophenyl-2'-aminophenyl ether; S3, under inert gas and acidic conditions, sodium nitrite and intermediate A-2 undergo diazotization reaction to generate diazonium salt, which then undergoes nucleophilic aromatic substitution reaction with potassium iodide to generate intermediate A-3, i.e. 2-fluorophenyl-2'-iodophenyl ether; S4. Under inert gas, intermediate A-3 reacts with n-butyl lithium to generate 1-lithiodibenzofuran, which then undergoes electrophilic aromatic substitution reaction with a bromination reagent to obtain 1-bromodibenzofuran.

2. The method for preparing 1-bromodibenzofuran, an organic light-emitting material intermediate, according to claim 1, characterized in that: In step S1, the base used is at least one of cesium carbonate, potassium carbonate, and sodium carbonate; The molar ratio of o-fluoronitrobenzene, o-fluorophenol and base is 1:(1.0-1.3):(2-3).

3. The method for preparing 1-bromodibenzofuran, an organic light-emitting material intermediate, according to claim 1, characterized in that: In step S1, the reaction temperature is 80-90°C.

4. The method for preparing 1-bromodibenzofuran, an organic light-emitting material intermediate, according to claim 1, characterized in that: In step S2, the catalyst is ferric chloride hexahydrate, the carrier is activated carbon, and the reducing agent is hydrazine hydrate; The molar ratio of intermediate A-1, ferric chloride hexahydrate, activated carbon and hydrazine hydrate is 1:(0.2-0.5):(6-9):(8-12.5).

5. The method for preparing 1-bromodibenzofuran, an organic light-emitting material intermediate, according to claim 1, characterized in that: The solvents used in step S2 are toluene and ethanol, and the reaction process is a reflux reaction.

6. The method for preparing 1-bromodibenzofuran, an organic light-emitting material intermediate, according to claim 1, characterized in that: In step S3, sulfuric acid is used to provide acidic conditions; The molar ratio of intermediate A-2, sulfuric acid, sodium nitrite and potassium iodide is 1:(6-12):(1-1.2):(1-1.3).

7. The method for preparing 1-bromodibenzofuran, an organic light-emitting material intermediate, according to claim 1, characterized in that: In step S3, the temperature conditions for the diazotization reaction and the nucleophilic aromatic substitution reaction are 0-5°C.

8. The method for preparing 1-bromodibenzofuran, an organic light-emitting material intermediate, according to claim 1, characterized in that: In step S4, the bromination reagent is at least one of 1,2-dibromoethane, 1,2-dibromotetrafluoroethane, and NBS.

9. The method for preparing 1-bromodibenzofuran, an organic light-emitting material intermediate, according to claim 1, characterized in that: In step S4, the molar ratio of intermediate A-3, n-butyl lithium and bromination reagent is 1:(2-2.5):(1-3).

10. The method for preparing 1-bromodibenzofuran, an organic light-emitting material intermediate, according to claim 1, characterized in that: In step S4, the temperature condition for the reaction of intermediate A-3 with n-butyl lithium is -35 to -30°C; the temperature condition for the electrophilic aromatic substitution reaction of 1-lithiodibenzofuran with the bromination reagent is -80 to -75°C.

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