Preparation method of a carbazole-based organic electroluminescent host material

Abstract

The present application provides a preparation method of a carbazole-based organic electroluminescent host material. Using inexpensive substrates 2-bromo-5-fluoro-nitrobenzene and 1-naphthylboronic acid, the coupling intermediate S1 is obtained through a Suzuki coupling reaction, and the ring-closing intermediate S2 is obtained by reduction with triphenylphosphine; the brominated product S3 is obtained by reacting with a brominating reagent in a suitable solvent; the intermediate S4 is synthesized using iodobenzene or an iodobenzene derivative; the intermediate S5 is obtained by reacting an arylamine with intermediate 4; the ring closure is achieved through C-H activation under Pd catalysis to obtain the intermediate S6; the 7,9-dihydrobenzo[g]indolo[2,3-b]carbazole derivative S7 is synthesized using iodobenzene or a benzene derivative.

Description

Technical Field

[0001] This application relates to the field of organic synthesis, and particularly to a method for preparing 7,9-dihydrobenzo[g]indolo[2,3-b]carbazole derivatives. Background Art

[0002] The organic light-emitting phenomenon refers to the phenomenon of converting electrical energy into light energy of organic materials. An organic electro-accelerator using the organic light-emitting phenomenon usually has a structure including an anode, a cathode, and an inorganic material layer therebetween. The organic material layer has a multilayer structure, which respectively has different materials to improve the efficiency and stability of the organic electrical component.

[0003] When only one material is used as the light-emitting material, due to intermolecular interactions, there will be a problem that the maximum emission wavelength shifts to a longer wavelength, and due to the deterioration of color purity or the reduction of luminous efficiency, the efficiency of the corresponding element will be reduced. A host material / dopant system can be used as the light-emitting material to enhance color purity and improve luminous efficiency through energy transfer. The selection of the host material is important because the host material greatly affects the efficiency and performance of the light-emitting device. In traditional technologies, 4,4'-N,N'-dicarbazolylbiphenyl (CBP) is the most well-known phosphorescent host material. Pioneers (Japan) et al. have currently developed a highly efficient organic EL device using phenol (BCP), aluminum(III) bis(2-methyl-8-quinolinolato)(BAlq), etc. as host materials for the hole-blocking layer.

[0004] Although these phosphorescent host materials have good luminescent properties, they have the following disadvantages: (1) Due to their low glass transition temperature and poor thermal stability, they may degrade during the high-temperature deposition process in a vacuum. (2) The power efficiency of an organic EL device is represented by [(π / v) x current efficiency], and the power efficiency is inversely proportional to the voltage. An organic EL device containing a phosphorescent host material provides a higher current efficiency (cd / A) and has a higher driving voltage than a device containing a fluorescent host material. Therefore, an organic EL device using a traditional phosphorescent host material has no advantage in terms of power efficiency (lm / W). (3) In addition, both the operating life and luminous efficiency of the organic EL device are not satisfactory.

[0005] 7,9-Dihydrobenzo[g]indolo[2,3-b]carbazole derivatives are a class of organic electroluminescent compounds with high luminous efficiency. Organic light-emitting devices using such compounds as host materials have the characteristics of low power consumption, long driving life, and high luminous efficiency.

[0006] The existing techniques for synthesizing 7,9-dihydrobenzo[g]indolo[2,3-b]carbazole derivatives are usually Method 1:

[0007]

[0008] For S1, 3% mol of tetrakis(triphenylphosphine)palladium is used. For both S4 and S5, 4% mol of palladium acetate is used. And for S4 →

[0009] During the ring - closing process of S5, ring - closing may occur at both ortho - positions of the imine. Especially when the substituents on the halide are all small groups, the steric hindrance is small, the content of isomers increases significantly, and purification is difficult. See WO2015099486A1 for details.

[0010] Method 2:

[0011]

[0012] For S1, 3% mol of tetrakis(triphenylphosphine)palladium is used. For S2, 3% Pd(dppf)Cl2 is used, and the yield of S3 is only 39%;

[0013] The main reason for the low yield is also that there are two ring - closing sites during the ring - closing process of S2 → S3, generating isomers and making purification difficult. See WO2018021737A1 for details.

[0014] Method 3:

[0015]

[0016] For S1, 2% mol of Pd2(dba)3 is used. For S3, 2% mol of tetrakis(triphenylphosphine)palladium is used, and the yield of S4 is only 31% - 77%; There are two sites during the ring - closing process of S3 → S4, and the steric hindrance is small, with isomers and difficult purification. See CN202110915767.7 for details.

[0017] When synthesizing 7,9 - dihydrobenzo[g]indolo[2,3 - b]carbazole derivatives using the existing technologies, whether it is Method 1, Method 2, or Method 3 above, isomers will be generated: isomers are generated when preparing S5 from S4 in Method 1, when preparing S3 from S2 in Method 2, and when preparing S4 from S3 in Method 3, resulting in extremely difficult purification, low product content, low yield, and high cost; at the same time, the above three methods use a large amount of expensive palladium catalysts multiple times, further leading to high costs and being not conducive to industrial production. Summary of the Invention

[0018] The technical problem to be solved by the present invention is: to solve the problem of isomers existing in the process of synthesizing carbazole - based organic electroluminescent host materials in the prior art;

[0019] To solve the technical problem of the present invention, the following technical solutions are adopted in the present invention:

[0020] This application provides a preparation method of a carbazole - based organic electroluminescent host material, and the reaction route of the preparation method is as follows:

[0021]

[0022] Among them, R1 to R11 are each independently selected from H, halogen, C1-C12 alkyl, C1-C20 substituted or unsubstituted aryl, and a benzene ring fused on one side;

[0023] Step 1: Use the substrate 2-bromo-5-fluoro-nitrobenzene and 1-naphthaleneboronic acid to obtain the coupling intermediate S1 through the Suzuki coupling reaction;

[0024] Step 2: Use triphenylphosphine to reduce the coupling intermediate S1 obtained in the ring-closing step 1 to obtain S2;

[0025] Step 3: Brominate the S2 bromide prepared in step 2 to obtain the bromide S3;

[0026] Step 4: Use iodobenzene or an iodobenzene derivative to synthesize the intermediate S4 from the S3 prepared in step 3;

[0027] Step 5: React an arylamine with the intermediate S4 obtained in step 4 to obtain the intermediate S5;

[0028] Step 6: Achieve ring closure through the C-H activation of S5 in step 5 under the catalysis of a Pd catalyst to obtain the intermediate S6;

[0029] Step 7: Use iodobenzene or an iodobenzene derivative to synthesize the 7,9-dihydrobenzo[g]indolo[2,3-b]carbazole derivative S7 from the S6 prepared in step 6.

[0030] The present invention adopts the above technical solutions and has the following beneficial technical effects compared with the prior art:

[0031] 1. In the reaction route of the present application, in the fifth reaction (S5), a palladium catalyst is not used, and the arylamine is directly aminated at the fluorine group, and the bromine group is retained; in the sixth reaction (S6), the amino group of the arylamine is directly coupled with the bromine group at the ortho position, with high selectivity, greatly reducing the generation of isomers.

[0032] 2. The present application uses inexpensive catalysts, 1% mol of tetrakis(triphenylphosphine)palladium and 1% mol of palladium acetate, and the dosage is reduced to less than 50% of the commonly used methods in the prior art; at the same time, it should be noted that the initial raw materials 2-bromo-5-fluoronitrobenzene and 1-naphthaleneboronic acid of the present application are cheap and easily available, with low cost;

[0033] 3. The reaction temperature is in the range of 5-160 °C, without reactions at ultra-low temperatures of -70 to -80 °C, avoiding the use of ultra-low temperature media such as liquid nitrogen and ultra-low temperature equipment, reducing the difficulty of temperature control, and at the same time avoiding the use of a large amount of anhydrous magnesium sulfate for drying, which is economical and environmentally friendly. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] Figure 1 1H NMR characterization diagram of the final product of Example 1. Detailed implementation mode

[0035] An embodiment of the present application provides a preparation method of a carbazole-based organic electroluminescent host material, and the reaction route of the preparation method is as follows:

[0036]

[0037] Wherein, each of R1 to R11 is independently selected from H, halogen, C1-C12 alkyl, C1-C20 substituted or unsubstituted aryl, and a benzene ring fused on one side;

[0038] Step 1: Use the substrate 2-bromo-5-fluoro-nitrobenzene and 1-naphthaleneboronic acid to obtain a coupling intermediate S1 through a Suzuki coupling reaction;

[0039] Step 2: Use triphenylphosphine to reduce the coupling intermediate S1 obtained in the ring closing step 1 to obtain S2;

[0040] Step 3: Brominate the S2 bromide prepared in step 2 to obtain a bromide S3;

[0041] Step 4: Use iodobenzene or an iodobenzene derivative to synthesize an intermediate S4 from the S3 prepared in step 3;

[0042] Step 5: React arylamine with the intermediate S4 obtained in step 4 to obtain an intermediate S5;

[0043] Step 6: Achieve ring closure by C-H activation of S5 in step 5 under the catalysis of a Pd catalyst to obtain an intermediate S6;

[0044] Step 7: Use iodobenzene or an iodobenzene derivative to synthesize a 7,9-dihydrobenzo[g]indolo[2,3-b]carbazole derivative S7 from the S6 prepared in step 6.

[0045] In one embodiment, the iodobenzene or iodobenzene derivative has the following structure:

[0046]

[0047]

[0048] In one embodiment, the arylamine has the following structure:

[0049]

[0050] In one embodiment, the Pd catalyst includes: palladium acetate, tris(dibenzylideneacetone)dipalladium, and bis(dibenzylideneacetone)palladium.

[0051] In one embodiment, in the step 1, 2-bromo-5-fluoronitrobenzene, 1-naphthaleneboric acid, potassium carbonate, toluene, ethanol and water are added to the reactor, the atmosphere is replaced with nitrogen, a catalyst Pd(PPh3)4 is added, the temperature is raised to reflux for reaction for 7 to 9 hours, the temperature is lowered to 50±5°C for separation, the organic phase is washed with water and then concentrated under reduced pressure, ethanol is added, the temperature is raised to reflux for 1 to 2 hours, the temperature is lowered to 30±5°C, and the light yellow solid S1 is filtered and dried;

[0052] In step 2, S1, triphenylphosphine and o-dichlorobenzene are added to a reactor, the temperature is raised to 160±5°C and the reaction is carried out for 9 to 11 hours, the reaction is concentrated under reduced pressure, ethanol and toluene are added, the temperature is refluxed and beaten for 1 to 2 hours, the temperature is lowered to 20±5°C, and the reaction is filtered and dried to obtain an off-white solid S2;

[0053] In step 3, S2 and dichloromethane are added to the reactor, the temperature is lowered to 5±5°C, NBS is added, the temperature is kept for 2 to 3 hours, the temperature is naturally returned to 30±5°C, and the reaction is carried out overnight. The reaction is quenched with 10% sodium bisulfite, the liquid is separated, the organic phase is washed with 20 ml of water × 3, concentrated under reduced pressure, ethanol is added, the temperature is raised to reflux and slurrying for 1 to 2 hours, the temperature is lowered to 30±5°C, and the white solid S3 is obtained by filtration and drying.

[0054] In one embodiment, in step 4, S3, iodobenzene or 4-iodobiphenyl, cuprous iodide, 1,10-phenanthroline, potassium carbonate, and toluene are added to a reactor, the temperature is raised to reflux and the reaction is carried out overnight, the temperature is lowered to 80±5°C, the reaction is filtered, the filter cake is rinsed with toluene, and the reaction is concentrated under reduced pressure. Methanol is added and the temperature is raised to reflux and slurrying for 1 to 2 hours, the temperature is lowered to 20±5°C, and the reaction is filtered and dried to obtain a white solid S4.

[0055] In one embodiment, in step 5, S4, DMF and aniline or p-toluidine are added to the reactor, the temperature is lowered to 5±5°C, potassium tert-butoxide is added, the temperature is kept at 5±5°C for two hours, the temperature is raised to 120±5°C for overnight reaction, the temperature is lowered to 20±5°C, water is added, the temperature is kept stirred for 4-5 hours, ethanol is added after filtration, the mixture is beaten at room temperature at 30±5°C for 1-2 hours, the mixture is filtered, dichloroethane is added under normal pressure, the temperature is raised to reflux and the temperature is kept for 1-2 hours, the temperature is lowered to 20±5°C, the mixture is filtered and dried to obtain a light yellow solid S5.

[0056] In one embodiment, in step 6, S5 and xylene are added to a reactor, the atmosphere is replaced with nitrogen, and then sodium tert-butoxide, palladium acetate and 10% tri-tert-butylphosphine toluene solution are added, the temperature is raised to 140±5°C for reaction for 8-10 hours, the temperature is lowered to 80±5°C, the mixture is filtered through a silica gel pad, the organic phase is washed with water and concentrated, and then toluene and ethanol are added, the temperature is raised to reflux under normal pressure for 2-3 hours, the temperature is lowered to 10±5°C, the mixture is kept warm for 4-5 hours, and the mixture is filtered and dried to obtain a light yellow solid S6.

[0057] In one embodiment, in step 7, S6, iodobenzene or 4-iodobiphenyl, cuprous iodide, 1,10-phenanthroline, potassium carbonate, and xylene are added to a reactor. The temperature is raised to reflux and the reaction is kept overnight. Then the temperature is lowered to 100 ± 5 °C. Silica gel is padded and suction filtration is carried out. The filter cake is rinsed with xylene, concentrated under reduced pressure, toluene is added, the temperature is raised to reflux and pulping is carried out for 1 - 2 hours, the temperature is lowered to 30 ± 5 °C, and filtration and drying are carried out to obtain the white solid 7,9-dihydrobenzo[g]indolo[2,3-b]carbazole derivative S7.

[0058] In one embodiment, the carbazole-based organic electroluminescent host material includes any one of the following compounds:

[0059]

[0060]

[0061] To further illustrate the relevant content of this application, the present invention selects the experimental data of some synthetic substrates for auxiliary explanation.

[0062] Example 1 (Aniline + Iodobenzene)

[0063]

[0064] S1: Add 5.00 g (22.73 mmol) of 2-bromo-5-fluoronitrobenzene, 3.91 g (22.73 mmol) of 1-naphthaleneboronic acid, 6.28 g (45.46 mmol) of potassium carbonate, 20 ml of toluene, 10 ml of ethanol and 10 ml of water to a reaction flask. After purging with nitrogen, add 0.26 g (0.23 mmol) of Pd(PPh3)4 as a catalyst. Raise the temperature to reflux and react for 8 hours. Lower the temperature to 50 °C and carry out liquid separation. Wash the organic phase with 20 ml of water × 3 times. Concentrate under reduced pressure. Add 20 ml of ethanol, raise the temperature to reflux and carry out pulping for 1.5 hours. Lower the temperature to 25 °C, filter and dry to obtain 5.52 g of a light yellow solid, with a yield of 90.9% and an HPLC purity of 99%.

[0065] S2: Add 5.00 g (18.71 mmol) of S1, 14.72 g (56.13 mmol) of triphenylphosphine and 30 ml of o-dichlorobenzene to a reaction flask. Raise the temperature to 160 °C and react for 10 hours. Concentrate under reduced pressure. Add 10 ml of ethanol and 1 ml of toluene, raise the temperature to reflux and carry out pulping for 1.5 hours. Lower the temperature to 20 °C, filter and dry to obtain 3.65 g of an off-white solid, with a yield of 82.9% and an HPLC purity of 99%.

[0066] S3: Add 3.60 g (15.30 mmol) of S2 and 30 ml of dichloromethane to the reaction flask. Cool the temperature to 5 °C, add 12.00 g (45.71 mmol) of NBS, keep the temperature at 5 °C for 2.5 hours, and then let it return to room temperature naturally and react overnight. After overnight reaction, add 10 ml of 10% sodium bisulfite to quench the reaction. Separate the layers by liquid separation. Wash the organic phase with 20 ml of water three times, concentrate it under reduced pressure, add 10 ml of ethanol, heat it to reflux and stir for 1 hour. Cool the temperature to 30 °C, filter and dry to obtain 4.57 g of white solid, with a yield of 93.6% and an HPLC purity of 99%.

[0067] S4: Add 4.00 g (12.73 mmol) of S3, 3.12 g (15.28 mmol) of iodobenzene, 0.24 g (1.27 mmol) of cuprous iodide, 0.23 g (1.27 mmol) of 1,10-phenanthroline, 3.52 g (25.46 mmol) of potassium carbonate and 40 ml of toluene to the reaction flask. Heat it to reflux and keep the reaction overnight. Cool the temperature to 80 °C, filter by suction. Wash the filter cake with 20 ml of toluene. Concentrate it under reduced pressure, add 20 ml of methanol, heat it to reflux and stir for 1.5 hours. Cool the temperature to 20 °C, filter and dry to obtain 4.05 g of white solid, with a yield of 81.5% and an HPLC purity of 98%.

[0068] S5: Add 3.00 g (7.69 mmol) of S4, 30 ml of DMF and 1.43 g (15.37 mmol) of aniline to the reaction flask. Cool the temperature to 5 °C, add 1.29 g (11.53 mmol) of potassium tert-butoxide, keep the temperature at 5 °C for two hours, then heat it to 120 °C and react overnight. Cool the temperature to 20 °C, add 120 ml of water, keep the temperature for 4 hours, filter by suction to obtain 4.72 g. Add 20 ml of ethanol and stir at room temperature for 1 hour, filter by suction to obtain 4.40 g. Add 10 g of dichloroethane, heat it to reflux and keep the temperature for 1.5 hours. Cool the temperature to 20 °C, filter by suction and dry to obtain 3.34 g of light yellow solid, with a yield of 93.8% and an HPLC purity of 99%.

[0069] S6: Add 2.00 g (4.32 mmol) of S5 and 40 ml of xylene to the reaction flask. Replace the air with nitrogen. Add 1.66 g (17.28 mmol) of sodium tert-butoxide, 0.01 g (0.04 mmol) of palladium acetate and 0.17 g (0.08 mmol) of 10% tri-tert-butylphosphine toluene solution. Heat it to 140 °C and react for 9 hours. Cool the temperature to 80 °C, filter through 10 g of silica gel. Wash the filtrate with 20 ml of water three times. Concentrate the organic phase, then add 6 ml of toluene and 6 ml of ethanol, heat it to reflux for 2.5 hours. Cool the temperature to 10 °C, keep the temperature for 4.5 hours, filter by suction and dry to obtain 1.30 g of light yellow solid, with a yield of 78.8% and an HPLC purity of 98%.

[0070] S7: Add 1.00 g (2.62 mmol) of S6, 0.80 g (3.92 mmol) of iodobenzene, 0.05 g (0.26 mmol) of cuprous iodide, 0.05 g (0.26 mmol) of 1,10-phenanthroline, 1.08 g (25.46 mmol) of potassium carbonate, and 50 ml of xylene into the reaction flask. Heat up to reflux and keep the reaction overnight. Cool down to 100 °C, filter with 5.00 g of silica gel pad. Wash the filter cake with 40 ml of xylene. Concentrate under reduced pressure. Add 20 ml of toluene, heat up to reflux and slurry for 1.5 hours. Cool down to 30 °C, filter and dry to obtain 0.89 g of white solid, with a yield of 74.2% and an HPLC purity of 99.6%.

[0071] Example 2 (p-toluidine + iodobenzene)

[0072]

[0073] S1: Add 5.00 g (22.73 mmol) of 2-bromo-5-fluoronitrobenzene, 3.91 g (22.73 mmol) of 1-naphthylboronic acid, 6.28 g (45.46 mmol) of potassium carbonate, 20 ml of toluene, 10 ml of ethanol and 10 ml of water into the reaction flask. Replace the air with nitrogen. Add 0.26 g (0.23 mmol) of Pd(PPh3)4 as the catalyst. Heat up to reflux and react for 7 hours. Cool down to 45 °C and separate the layers. Wash the organic layer with 20 ml of water for 3 times. Concentrate under reduced pressure. Add 20 ml of ethanol, heat up to reflux and slurry for 1 hour. Cool down to 25 °C, filter and dry to obtain 5.55 g of light yellow solid, with a yield of 91.5% and an HPLC purity of 99%.

[0074] S2: Add 5.00 g (18.71 mmol) of S1, 14.72 g (56.13 mmol) of triphenylphosphine and 30 ml of o-dichlorobenzene into the reaction flask. Heat up to 155 °C and react for 9 hours. Concentrate under reduced pressure. Add 10 ml of ethanol and 1 ml of toluene, heat up to reflux and slurry for 1 hour. Cool down to 15 °C, filter and dry to obtain 3.67 g of off-white solid, with a yield of 83.4% and an HPLC purity of 99%.

[0075] S3: Add 3.60 g (15.30 mmol) of S2 and 30 ml of dichloromethane into the reaction flask. Cool down to 0 °C, add 12.00 g (45.71 mmol) of NBS, keep the temperature at 0 °C for 2 hours, and then let it warm up to 25 °C naturally and react overnight. After overnight reaction, add 10 ml of 10% sodium bisulfite to quench the reaction. Separate the layers. Wash the organic layer with 20 ml of water for 3 times. Concentrate under reduced pressure. Add 10 ml of ethanol, heat up to reflux and slurry for 1 hour. Cool down to 25 °C, filter and dry to obtain 4.59 g of white solid, with a yield of 94.0% and an HPLC purity of 99%.

[0076] S4: Add 4.00 g (12.73 mmol) of S3, 3.12 g (15.28 mmol) of iodobenzene, 0.24 g (1.27 mmol) of cuprous iodide, 0.23 g (1.27 mmol) of 1,10-phenanthroline, 3.52 g (25.46 mmol) of potassium carbonate, and 40 ml of toluene to the reaction flask. Heat up to reflux and keep the reaction overnight. Cool down to 75 °C, perform suction filtration. Wash the filter cake with 20 ml of toluene. Concentrate under reduced pressure. Add 20 ml of methanol, heat up to reflux and stir for 1.0 hour. Cool down to 15 °C, filter and dry to obtain 4.08 g of white solid, with a yield of 82.3% and an HPLC purity of 98%.

[0077] S5: Add 3.00 g (7.69 mmol) of S4, 30 ml of DMF, and 1.64 g (15.37 mmol) of p-toluidine to the reaction flask. Cool down to 0 °C, add 1.29 g (11.53 mmol) of potassium tert-butoxide, keep at 0 °C for two hours, heat up to 120 °C and react overnight. Cool down to 20 °C, add 120 ml of water, keep warm for 4 hours, perform suction filtration to obtain 4.70 g. Add 20 ml of ethanol, stir at room temperature for 1 hour, perform suction filtration to obtain 4.42 g. Add 10 g of dichloroethane, heat up to reflux and keep warm for 1 hour. Cool down to 15 °C, filter and dry to obtain 3.46 g of light yellow solid, with a yield of 94.3% and an HPLC purity of 99%.

[0078] S6: Add 2.06 g (4.32 mmol) of S5 and 40 ml of xylene to the reaction flask. Replace the air with nitrogen. Add 1.66 g (17.28 mmol) of sodium tert-butoxide, 0.01 g (0.04 mmol) of palladium acetate, and 0.17 g (0.08 mmol) of 10% tri-tert-butylphosphine toluene solution. Heat up to 135 °C and react for 8 hours. Cool down to 75 °C, filter through 10 g of silica gel. Wash the filtrate with 20 ml × 3 of water. Concentrate the organic phase. Add 6 ml of toluene and 6 ml of ethanol, heat up to reflux for 2 hours. Cool down to 5 °C, keep warm for 4 hours, filter and dry to obtain 1.37 g of light yellow solid, with a yield of 80.1% and an HPLC purity of 98%.

[0079] S7: Add 1.03 g (2.62 mmol) of S6, 0.80 g (3.92 mmol) of iodobenzene, 0.05 g (0.26 mmol) of cuprous iodide, 0.05 g (0.26 mmol) of 1,10-phenanthroline, 1.08 g (25.46 mmol) of potassium carbonate, and 50 ml of xylene to the reaction flask. Heat up to reflux and keep the reaction overnight. Cool down to 95 °C, filter through 5.00 g of silica gel. Wash the filter cake with 40 ml of xylene. Concentrate under reduced pressure. Add 20 ml of toluene, heat up to reflux and stir for 1 hour. Cool down to 30 °C, filter and dry to obtain 0.93 g of white solid, with a yield of 75.4% and an HPLC purity of 99.6%.

[0080] Example 3 (Aniline + 4-Iodobiphenyl)

[0081]

[0082] S1: Add 5.00 g (22.73 mmol) of 2-bromo-5-fluoronitrobenzene, 3.91 g (22.73 mmol) of 1-naphthaleneboronic acid, 6.28 g (45.46 mmol) of potassium carbonate, 20 ml of toluene, 10 ml of ethanol and 10 ml of water into the reaction flask. Replace the air with nitrogen. Add 0.26 g (0.23 mmol) of Pd(PPh3)4 as the catalyst. Heat up to reflux and react for 9 hours. Cool down to 55 °C and separate the layers. Wash the organic phase with 20 ml of water for 3 times. Concentrate under reduced pressure. Add 20 ml of ethanol, heat up to reflux and slurry for 2 hours. Cool down to 35 °C, filter and dry to obtain 5.54 g of light yellow solid, with a yield of 91.3% and an HPLC purity of 99%.

[0083] S2: Add 5.00 g (18.71 mmol) of S1, 14.72 g (56.13 mmol) of triphenylphosphine and 30 ml of o-dichlorobenzene into the reaction flask. Heat up to 175 °C and react for 11 hours. Concentrate under reduced pressure. Add 10 ml of ethanol and 1 ml of toluene, heat up to reflux and slurry for 2 hours. Cool down to 25 °C, filter and dry to obtain 3.63 g of off-white solid, with a yield of 82.5% and an HPLC purity of 99%.

[0084] S3: Add 3.60 g (15.30 mmol) of S2 and 30 ml of dichloromethane into the reaction flask. Cool down to 5 °C. Add 12.00 g (45.71 mmol) of NBS. Keep the temperature at 10 °C for two hours. Let it warm up to 35 °C naturally and then react overnight. Quench with 10 ml of 10% sodium bisulfite. Separate the layers. Wash the organic phase with 20 ml of water for 3 times. Concentrate under reduced pressure. Add 10 ml of ethanol, heat up to reflux and slurry for 2 hours. Cool down to 35 °C, filter and dry to obtain 4.54 g of white solid, with a yield of 92.9% and an HPLC purity of 99%.

[0085] S4: Add 4.00 g (12.73 mmol) of S3, 4.27 g (15.28 mmol) of 4-iodobiphenyl, 0.24 g (1.27 mmol) of cuprous iodide, 0.23 g (1.27 mmol) of 1,10-phenanthroline, 3.52 g (25.46 mmol) of potassium carbonate and 40 ml of toluene into the reaction flask. Heat up to reflux and keep the temperature for reaction overnight. Cool down to 85 °C, filter by suction. Wash the filter cake with 20 ml of toluene. Concentrate under reduced pressure. Add 20 ml of methanol, heat up to reflux and slurry for 2 hours. Cool down to 25 °C, filter and dry to obtain 4.87 g of white solid, with a yield of 82.3% and an HPLC purity of 98%.

[0086] S5: Add 3.60 g (7.69 mmol) of S4, 30 ml of DMF and 1.43 g (15.37 mmol) of aniline to the reaction flask. Cool down the temperature to 10 °C, add 1.29 g (11.53 mmol) of potassium tert-butoxide, keep the temperature at 10 °C for two hours, then raise the temperature to 125 °C and react overnight. Cool down the temperature to 25 °C, add 120 ml of water, keep the temperature for 4 hours, filter by suction to obtain 4.72 g. Add 20 ml of ethanol and stir at room temperature for 2 hours, filter by suction to obtain 5.15 g. Add 10 g of dichloroethane, raise the temperature to reflux and keep the temperature for 2 hours, cool down the temperature to 25 °C, filter by suction and dry to obtain 3.89 g of light yellow solid, with a yield of 94.1% and an HPLC purity of 99%.

[0087] S6: Add 2.33 g (4.32 mmol) of S5 and 40 ml of xylene to a 100-ml reaction flask, displace with nitrogen, add 1.66 g (17.28 mmol) of sodium tert-butoxide, 0.01 g (0.04 mmol) of palladium acetate and 0.17 g (0.08 mmol) of 10% tri-tert-butylphosphine toluene solution. Raise the temperature to 145 °C and react for 10 hours, then cool down the temperature to 85 °C, filter through 10 g of silica gel, wash the filtrate with 20 ml of water for 3 times, concentrate the organic phase, add 6 ml of toluene and 6 ml of ethanol, raise the temperature to reflux for 3 hours, cool down the temperature to 15 °C, keep the temperature for 5 hours, filter by suction and dry to obtain 1.57 g of light yellow solid, with a yield of 79.4% and an HPLC purity of 98%.

[0088] S7: Add 1.20 g (2.62 mmol) of S6, 1.09 g (3.92 mmol) of 4-iodobiphenyl, 0.05 g (0.26 mmol) of copper iodide, 0.05 g (0.26 mmol) of 1,10-phenanthroline, 1.08 g (25.46 mmol) of potassium carbonate and 50 ml of xylene to the reaction flask, raise the temperature to reflux and keep the temperature for reaction overnight, then cool down the temperature to 105 °C, filter through 5.00 g of silica gel by suction, wash the filter cake with 40 ml of xylene, concentrate under reduced pressure, add 20 ml of toluene, raise the temperature to reflux and stir for 1 hour, cool down the temperature to 35 °C, filter and dry to obtain 1.21 g of white solid, with a yield of 76.1% and an HPLC purity of 99.6%.

[0089] Example 4 (p-toluidine + 4-iodobiphenyl)

[0090]

[0091] S1: Add 5.00 g (22.73 mmol) of 2-bromo-5-fluoronitrobenzene, 3.91 g (22.73 mmol) of 1-naphthaleneboronic acid, 6.28 g (45.46 mmol) of potassium carbonate, 20 ml of toluene, 10 ml of ethanol and 10 ml of water into a reaction flask. Replace the air with nitrogen, add 0.26 g (0.23 mmol) of Pd(PPh3)4 as a catalyst, heat up to reflux and react for 8.5 hours. Cool down to 56 °C and separate the layers. Wash the organic phase with 20 ml of water for 3 times, concentrate under reduced pressure, add 20 ml of ethanol, heat up to reflux and stir for 2 hours. Cool down to 28 °C, filter and dry to obtain 5.50 g of light yellow solid, with a yield of 90.5% and an HPLC purity of 99%.

[0092] S2: Add 5.00 g (18.71 mmol) of S1, 14.72 g (56.13 mmol) of triphenylphosphine and 30 ml of o-dichlorobenzene into a reaction flask. Heat up to 173 °C and react for 10.5 hours. Concentrate under reduced pressure, add 10 ml of ethanol and 1 ml of toluene, heat up to reflux and stir for 2 hours. Cool down to 28 °C, filter and dry to obtain 3.61 g of off-white solid, with a yield of 82.0% and an HPLC purity of 99%.

[0093] S3: Add 3.60 g (15.30 mmol) of S2 and 30 ml of dichloromethane into a reaction flask. Cool down to 5 °C, add 12.00 g (45.71 mmol) of NBS, keep the temperature at 8 °C for two hours, naturally warm up to 30 °C and then react overnight. Quench with 10 ml of 10% sodium bisulfite, separate the layers. Wash the organic phase with 20 ml of water for 3 times, concentrate under reduced pressure, add 10 ml of ethanol, heat up to reflux and stir for 1.5 hours. Cool down to 28 °C, filter and dry to obtain 4.53 g of white solid, with a yield of 92.8% and an HPLC purity of 99%.

[0094] S4: Add 4.00 g (12.73 mmol) of S3, 4.28 g (15.28 mmol) of 4-iodobiphenyl, 0.24 g (1.27 mmol) of cuprous iodide, 0.23 g (1.27 mmol) of 1,10-phenanthroline, 3.52 g (25.46 mmol) of potassium carbonate and 40 ml of toluene into a reaction flask. Heat up to reflux and keep the temperature for overnight reaction. Cool down to 77 °C, filter by suction. Wash the filter cake with 20 ml of toluene, concentrate under reduced pressure, add 20 ml of methanol, heat up to reflux and stir for 2 hours. Cool down to 28 °C, filter and dry to obtain 4.83 g of white solid, with a yield of 81.3% and an HPLC purity of 98%.

[0095] S5: Add 3.60 g (7.69 mmol) of S4, 30 ml of DMF and 1.64 g (15.37 mmol) of p-toluidine to the reaction flask. Cool the temperature to 8 °C, add 1.29 g (11.53 mmol) of potassium tert-butoxide, keep the temperature at 7 °C for two hours, then raise the temperature to 122 °C and react overnight. Cool the temperature to 18 °C, add 120 ml of water, keep the temperature for 4 hours, filter by suction to obtain 4.81 g. Add 20 ml of ethanol and stir at room temperature for 2 hours, then filter by suction to obtain 5.19 g. Add 10 g of dichloroethane, raise the temperature to reflux and keep the temperature for 1.5 hours, then cool the temperature to 25 °C, filter by suction and dry to obtain 3.40 g of a light yellow solid, with a yield of 94.2% and an HPLC purity of 99%.

[0096] S6: Add 2.33 g (4.32 mmol) of S5 and 40 ml of xylene to a 100 ml reaction flask, displace with nitrogen, add 1.66 g (17.28 mmol) of sodium tert-butoxide, 0.01 g (0.04 mmol) of palladium acetate and 0.17 g (0.08 mmol) of 10% tri-tert-butylphosphine toluene solution. Raise the temperature to 142 °C and react for 9.5 hours, then cool the temperature to 83 °C, filter through 10 g of silica gel. Wash the filtrate with 20 ml of water three times, concentrate the organic phase, add 6 ml of toluene and 6 ml of ethanol, raise the temperature to reflux for 3 hours, then cool the temperature to 13 °C, keep the temperature for 4 hours, filter by suction and dry to obtain 1.61 g of a light yellow solid, with a yield of 79.3% and an HPLC purity of 98%.

[0097] S7: Add 1.20 g (2.62 mmol) of S6, 1.09 g (3.92 mmol) of 4-iodobiphenyl, 0.05 g (0.26 mmol) of cuprous iodide, 0.05 g (0.26 mmol) of 1,10-phenanthroline, 1.08 g (25.46 mmol) of potassium carbonate and 50 ml of xylene to the reaction flask. Raise the temperature to reflux and keep the temperature for reaction overnight, then cool the temperature to 102 °C, filter through 5.00 g of silica gel by suction. Wash the filter cake with 40 ml of xylene, concentrate under reduced pressure, add 20 ml of toluene, raise the temperature to reflux and stir for 1.3 hours, then cool the temperature to 28 °C, filter and dry to obtain 1.23 g of a white solid, with a yield of 75.4% and an HPLC purity of 99.6%.

[0098] The above are only specific embodiments of the present invention, which are only used to help understand the principle and core idea of the present invention, and are not used to limit the present invention. Within the idea and principle of the present invention, any modification, equivalent substitution, etc. made by those skilled in the art to the technical solutions described in the present invention should be included within the protection scope of the present invention.

Claims

1. A preparation method of a carbazole-based organic electroluminescent host material, characterized in that The reaction route of the preparation method is as follows: Wherein, each of R1 to R11 is independently selected from H, halogen, C1-C12 alkyl, and C1-C20 aryl; Step 1: Using the substrate 2-bromo-5-fluoro-nitrobenzene and 1-naphthylboronic acid, obtain the coupling intermediate S1 through the Suzuki coupling reaction; Step 2: Use triphenylphosphine to reduce and cyclize the coupling intermediate S1 obtained in Step 1 to obtain S2; Step 3: Brominate S2 prepared in Step 2 to obtain the bromide S3; Step 4: Use iodobenzene or iodobenzene derivative to synthesize the intermediate S4 from S3 prepared in Step 3; Step 5: React arylamine with the intermediate S4 obtained in Step 4 to obtain the intermediate S5; Step 6: Through C-H activation of S5 in Step 5 under the catalysis of a Pd catalyst, ring closure is achieved to obtain the intermediate S6; Step 7: The S6 prepared in Step 6 is synthesized into the carbazole-based organic electroluminescent host material 7,9-dihydrobenzo[g]indolo[2,3-b]carbazole derivative S7 through iodobenzene or iodobenzene derivative.

2. The preparation method according to claim 1, characterized in that, The iodobenzene or iodobenzene derivative has the following structure: Any one of 3. A preparation method of a carbazole-based organic electroluminescent host material, characterized in that, The reaction route of the preparation method is as follows: Wherein, R6 is selected from H, halogen, C1-C12 alkyl, and C1-C20 aryl; Step 1: Using the substrate 2-bromo-5-fluoro-nitrobenzene and 1-naphthylboronic acid, obtain the coupling intermediate S1 through the Suzuki coupling reaction; Step 2: Use triphenylphosphine to reduce and cyclize the coupling intermediate S1 obtained in Step 1 to obtain S2; Step 3: Brominate S2 prepared in Step 2 to obtain the bromide S3; Step 4: Use iodobenzene derivative to synthesize the intermediate S4 from S3 prepared in Step 3; Step 5: React arylamine with the intermediate S4 obtained in Step 4 to obtain the intermediate S5; Step 6: Through C-H activation of S5 in Step 5 under the catalysis of a Pd catalyst, ring closure is achieved to obtain the intermediate S6; Step 7: The S6 prepared in Step 6 is synthesized into the carbazole-based organic electroluminescent host material 7,9-dihydrobenzo[g]indolo[2,3-b]carbazole derivative S7 through iodobenzene derivative, and the iodobenzene derivative has the following structure: Any one of 4. According to the preparation method described in any one of claims 1-2, the arylamine has the following structure: Any one of 5. The preparation method according to claims 1-3, characterized in that, The Pd catalyst is: palladium acetate, tris(dibenzylideneacetone)dipalladium, and bis(dibenzylideneacetone)palladium.

6. The preparation method according to any one of claims 1-3, characterized in that, In Step 1, add 2-bromo-5-fluoronitrobenzene, 1-naphthylboronic acid, potassium carbonate, toluene, ethanol, and water into the reactor, displace with nitrogen, add the catalyst Pd(PPh3)4, heat up to reflux for 7-9 hours, cool down to 50±5°C for liquid separation, wash the organic phase with water and then concentrate under reduced pressure, add ethanol and heat up to reflux for pulping for 1-2 hours, cool down to 30±5°C, filter and dry to obtain the light yellow solid S1; In Step 2, add S1, triphenylphosphine, and o-dichlorobenzene into the reactor, heat up to 160±5°C for reaction for 9-11 hours, concentrate under reduced pressure, add ethanol and toluene and heat up to reflux for pulping for 1-2 hours, cool down to 20±5°C, filter and dry to obtain the off-white solid S2; In step 3, add S2 and dichloromethane into the reactor, cool down the temperature to 5 ± 5 °C, add NBS, keep the temperature for 2 - 3 hours, let it return to room temperature naturally to 30 ± 5 °C and then react overnight, quench with 10% sodium bisulfite, separate the liquid, wash the organic phase with 20 ml of water for 3 times, concentrate under reduced pressure, add ethanol, heat up to reflux and beat for 1 - 2 hours, cool down to 30 ± 5 °C, filter and dry to obtain white solid S3.

7. The preparation method according to any one of claims 1-2, characterized in that, In step 4, add S3, iodobenzene or 4-iodobiphenyl, cuprous iodide, 1,10-phenanthroline, potassium carbonate and toluene into the reactor, heat up to reflux and keep the temperature for reaction overnight, cool down to 80 ± 5 °C, filter by suction, wash the filter cake with toluene, concentrate under reduced pressure, add methanol, heat up to reflux and beat for 1 - 2 hours, cool down to 20 ± 5 °C, filter and dry to obtain white solid S4.

8. The preparation method according to any one of claims 1 to 3, characterized in that, In step 5, add S4, DMF and aniline or p-toluidine into the reactor, cool down the temperature to 5 ± 5 °C, add potassium tert-butoxide, keep the temperature at 5 ± 5 °C for two hours, heat up to 120 ± 5 °C and react overnight, cool down to 20 ± 5 °C, add water and keep stirring for 4 - 5 hours, filter by suction, add ethanol and beat at room temperature of 30 ± 5 °C for 1 - 2 hours, filter by suction, add dichloroethane under normal pressure, heat up to reflux and keep the temperature for 1 - 2 hours, cool down to 20 ± 5 °C, filter and dry to obtain light yellow solid S5.

9. The preparation method according to any one of claims 1 to 3, characterized in that, In step 6, add S5 and xylene into the reactor, displace with nitrogen, then add sodium tert-butoxide, palladium acetate and 10% tris(tert-butyl)phosphine toluene solution, heat up to 140 ± 5 °C and react for 8 - 10 hours, cool down to 80 ± 5 °C, filter through silica gel, wash the organic phase with water and then concentrate, add toluene and ethanol, heat up to reflux under normal pressure for 2 - 3 hours, cool down to 10 ± 5 °C, keep the temperature for 4 - 5 hours, filter and dry to obtain light yellow solid S6.

10. The preparation method according to any one of claims 1-2, characterized in that, In step 7, add S6, iodobenzene or 4-iodobiphenyl, cuprous iodide, 1,10-phenanthroline, potassium carbonate and xylene into the reactor, heat up to reflux and keep the temperature for reaction overnight, cool down to 100 ± 5 °C, filter through silica gel by suction, wash the filter cake with xylene, concentrate under reduced pressure, add toluene, heat up to reflux and beat for 1 - 2 hours, cool down to 30 ± 5 °C, filter and dry to obtain white solid 7,9-dihydrobenzo[g]indolo[2,3-b]carbazole derivative S7.

11. The preparation method according to any one of claims 1-2, characterized in that, The carbazole-based organic electroluminescent host material is any one of the following compounds:

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