Preparation method of 3, 6-diacetylene carbazole

Abstract

The invention provides a preparation method of 3, 6-diacetylene carbazole, and relates to the technical field of organic synthesis. According to the preparation method, 3, 6-diiodocarbazole and Boc2O are taken as initial reaction raw materials for reaction, then the initial reaction raw materials react with 2-methyl-3-butyne-2-alcohol, and finally, 3, 6-diethynyl carbazole is obtained through deprotection reaction. According to the preparation method, an NH group in 3, 6-diiodocarbazole is protected by Boc2O, then the protected 3, 6-diiodocarbazole reacts with 2-methyl-3-butyne-2-alcohol, so that the reaction is very easy to occur, byproducts are few, the product yield is greatly improved, and the 3, 6-diethynyl carbazole is prepared through a protecting group removal reaction. The method has the advantages of high total yield of 3, 6-diethynyl carbazole, few system byproducts, easiness in post-treatment, low production cost and suitability for industrial production. The test result of the embodiment shows that the total yield of the 3, 6-diacetylene carbazole is 81.3% or above.

Description

Technical Field

[0001] The invention relates to the technical field of organic synthesis, and in particular to a method for preparing 3,6-diethynylcarbazole. Background Art

[0002] Organic light-emitting diodes (OLEDs) have been developed for commercial applications as flat panel displays or artificial light sources for solid-state lighting. Considering the poor performance of blue OLEDs before red and green OLEDs, and the need for efficient blue emitting materials in full-color displays and white OLEDs (WOLEDs), there is still a lot of research work devoted to the development of new emitting dyes with blue emission. The normal operation of OLED devices using blue emitting materials is affected by their inherent large band gap, which makes it difficult to inject charges into the light-emitting layer. Therefore, in order to produce OLED devices with high power efficiency and longer service life, there is still a need to develop new blue emitters with thermal stability and the ability to form amorphous thin films, as well as high quantum yield in the solid state and color purity.

[0003] Carbazole derivatives have been used in a wide range of electronic and optoelectronic applications, such as organic thin film transistors (OTFTs), organic solar cells, and certain OLEDs, due to their high thermal stability, emission efficiency, ease of chemical functionalization, film-forming ability, and potential hole transport mobility related to the power supply capability of the carbazole unit. Among them, 3,6-diethynylcarbazole plays an extremely important role in the synthesis of light-emitting diodes.

[0004] The prior art discloses the preparation of 3,6-diethynylcarbazole using 3,6-diiodo-9H-carbazole and trimethylsilyl acetylene as initial raw materials, and the reaction route is shown in route 1. However, the total yield of the preparation method is only 78.4%, which is low.

[0005]

[0006] The prior art discloses the preparation of 3,6-diethynylcarbazole using 3,6-dibromo-9H-carbazole and 2-methyl-3-butyn-2-ol as initial raw materials, and the reaction route is shown in route 2. However, the total yield of the preparation method is only 47.74%, which is low.

[0007] Summary of the invention

[0008] In view of this, the object of the present invention is to provide a method for preparing 3,6-diethynylcarbazole. The preparation method provided by the present invention has a high total yield of 3,6-diethynylcarbazole.

[0009] In order to achieve the above-mentioned object of the invention, the present invention provides the following technical solutions:

[0010] The present invention provides a method for preparing 3,6-diethynylcarbazole, comprising the following steps:

[0011] Mixing 3,6-diiodocarbazole, Boc2O, a catalyst and a first organic solvent to perform a first substitution reaction to obtain an intermediate 2;

[0012] The intermediate 2, 2-methyl-3-butyn-2-ol, a palladium catalyst, an organic amine, cuprous iodide and a second organic solvent are mixed to carry out a second substitution reaction to obtain an intermediate 3;

[0013] The intermediate 3, an inorganic strong base and a third organic solvent are mixed to carry out a deprotection reaction to obtain 3,6-diethynylcarbazole;

[0014]

[0015] Preferably, the catalyst comprises one or more of an organic amine, an alkali metal fluoride and an alkali metal hydroxide;

[0016] The first organic solvent includes one or more of dichloromethane, chloroform, tetrahydrofuran, toluene and dioxane.

[0017] Preferably, the mass ratio of 3,6-diiodocarbazole to Boc2O is 1:0.7-1.3;

[0018] The mass ratio of the 3,6-diiodocarbazole to the catalyst is 1:0.25-0.45.

[0019] Preferably, the temperature of the first substitution reaction is 10-25° C. and the time is 5-10 h.

[0020] Preferably, the palladium catalyst comprises one or more of bistriphenylphosphine palladium dichloride, tetrakis(triphenylphosphine)palladium, 1,1'-bis(diphenylphosphino)ferrocenepalladium(II) dichloride, palladium acetate and bis(cyanobenzene)palladium dichloride;

[0021] The second organic solvent includes one or both of acetonitrile and tetrahydrofuran.

[0022] Preferably, the mass ratio of the intermediate 2 to 2-methyl-3-butyn-2-ol is 1:1-3;

[0023] The mass of the palladium catalyst is 1 to 2.5% of the mass of the intermediate 2;

[0024] The mass ratio of the intermediate 2 to the organic amine is 1:1-4;

[0025] The mass of the cuprous iodide is 0.75-1% of the mass of the intermediate 2.

[0026] Preferably, the temperature of the second substitution reaction is 10-25° C. and the time is 5-15 h.

[0027] Preferably, the inorganic strong base comprises an alkali metal hydroxide;

[0028] The third organic solvent includes one or more of n-butanol, methanol and toluene.

[0029] Preferably, the mass ratio of the intermediate 3 to the inorganic strong base is 1:0.3-0.8.

[0030] Preferably, the temperature of the deprotection reaction is 100-125° C., and the time is 10-30 min.

[0031] The present invention protects the NH group in 3,6-diiodocarbazole with Boc2O, and then reacts with 2-methyl-3-butyn-2-ol, so that the reaction is very easy to occur and has few by-products, greatly improving the product yield; then, 3,6-diethynylcarbazole can be prepared by deprotection reaction. The 3,6-diethynylcarbazole prepared by the preparation method provided by the present invention has a high total yield, few system by-products, is easy to post-process, has a low production cost, and is suitable for industrial production. As shown in the test results of the embodiment, the total yield of 3,6-diethynylcarbazole is above 81.3%. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] Figure 1 The NMR image of intermediate 3 prepared in Example 1;

[0033] Figure 2 This is the NMR image of 3,6-diethynylcarbazole prepared in Example 1. DETAILED DESCRIPTION

[0034] The present invention provides a method for preparing 3,6-diethynylcarbazole, comprising the following steps:

[0035] Mixing 3,6-diiodocarbazole, Boc2O, a catalyst and a first organic solvent to perform a first substitution reaction to obtain an intermediate 2;

[0036] The intermediate 2, 2-methyl-3-butyn-2-ol, a palladium catalyst, an organic amine, cuprous iodide and a second organic solvent are mixed to carry out a second substitution reaction to obtain an intermediate 3;

[0037] The intermediate 3, an inorganic strong base and a third organic solvent are mixed to carry out a deprotection reaction to obtain 3,6-diethynylcarbazole;

[0038]

[0039] Unless otherwise specified, the materials and equipment used in the present invention are all commercially available products in the art.

[0040] In the present invention, 3,6-diiodocarbazole, Boc2O, a catalyst and a first organic solvent are mixed to carry out a first substitution reaction to obtain an intermediate 2.

[0041] In the present invention, the mass ratio of 3,6-diiodocarbazole to Boc2O is preferably 1:0.7-1.6, and in specific embodiments may be 1:0.7, 1:0.8, 1:0.9, 1:1, 1:1.1, 1:1.2, 1:1.3, 1:1.4, 1:1.5 or 1:1.6.

[0042] In the present invention, the catalyst preferably includes one or more of an organic amine, an alkali metal fluoride and an alkali metal hydroxide; the organic amine preferably includes at least one of 4-dimethylaminopyridine (DMAP) and triethylamine; the alkali metal fluoride preferably includes cesium fluoride; the alkali metal hydroxide preferably includes sodium hydroxide and / or potassium hydroxide. In the present invention, the mass ratio of the 3,6-diiodocarbazole to the catalyst is preferably 1:0.25 to 0.45, and in specific embodiments can be 1:0.25, 1:0.3, 1:0.35, 1:0.4 or 1:0.45.

[0043] In the present invention, the first organic solvent preferably includes one or more of dichloromethane, chloroform, tetrahydrofuran, toluene and dioxane. In the present invention, the ratio of the mass of the 3,6-diiodocarbazole to the volume of the first organic solvent is preferably 1g:7-30mL, and in specific embodiments, it can be 1g:7mL, 1g:10mL, 1g:15mL, 1g:20mL, 1g:25mL or 1g:30mL.

[0044] In the present invention, the temperature of the first substitution reaction is preferably 10-25°C, and in specific embodiments it can be 10°C, 15°C, 20°C or 25°C; the time of the first substitution reaction is preferably 5-10h, and in specific embodiments it can be 5h, 6h, 7h, 8h, 9h or 10h.

[0045] In the present invention, the mixing and the first substitution reaction are preferably carried out under a protective atmosphere, and the protective atmosphere preferably includes nitrogen, argon or helium.

[0046] After completing the first substitution reaction, the present invention preferably further comprises: adding water to the reaction system obtained by the first substitution reaction, stirring, separating the liquids, and obtaining an organic phase and an aqueous phase respectively; extracting the aqueous phase with an organic solvent to obtain an organic extraction phase; combining the organic phase and the organic extraction phase, washing with water, washing with saturated salt water, drying with a desiccant, filtering, concentrating the obtained liquid component under reduced pressure, filtering, eluting the obtained solid component with petroleum ether, and then recrystallizing with methyl tert-butyl ether to obtain an intermediate 2. In the present invention, the organic solvent for extraction preferably includes one or more of dichloromethane, ethyl acetate and toluene.

[0047] In the present invention, the ratio of the mass of the 3,6-diiodocarbazole to the volume of water (water added before separation) is preferably 1g:10-30mL, and in specific embodiments it can be 1g:10mL, 1g:15mL, 1g:20mL, 1g:25mL or 1g:30mL.

[0048] In the present invention, the number of extractions is preferably 3 to 5 times, and in a specific embodiment, it can be 3 times, 4 times or 5 times; the ratio of the mass of the 3,6-diiodocarbazole to the volume of the organic solvent for a single extraction is preferably 1g:10 to 65mL, and in a specific embodiment, it can be 1g:10mL, 1g:20mL, 1g:30mL, 1g:40mL, 1g:40mL, 1g:60mL or 1g:65mL; ​​the organic solvent for extraction preferably includes one or more of dichloromethane, ethyl acetate, toluene and methyl tert-butyl ether.

[0049] In the present invention, the ratio of the mass of the 3,6-diiodocarbazole to the volume of the washing water is preferably 1g:10-30mL, and in specific embodiments can be 1g:10mL, 1g:15mL, 1g:20mL, 1g:25mL or 1g:30mL.

[0050] In the present invention, the desiccant preferably includes anhydrous sodium sulfate and / or anhydrous magnesium sulfate.

[0051] In the present invention, the ratio of the mass of 3,6-diiodocarbazole to the volume of petroleum ether is preferably 1g:1.5-5mL, and in specific embodiments it can be 1g:1.5mL, 1g:2mL, 1g:3mL, 1g:4mL or 1g:5mL.

[0052] After obtaining intermediate 2, the present invention mixes intermediate 2, 2-methyl-3-butyn-2-ol, a palladium catalyst, an organic amine, cuprous iodide and a second organic solvent to perform a second substitution reaction to obtain intermediate 3.

[0053] In the present invention, the mass ratio of the intermediate 2 to 2-methyl-3-butyn-2-ol is preferably 1:1-3, and in specific embodiments may be 1:1, 1:1.5, 1:2, 1:2.5 or 1:3.

[0054] In the present invention, the palladium catalyst preferably includes one or more of bistriphenylphosphine palladium dichloride, tetrakis(triphenylphosphine)palladium, 1,1'-bis(diphenylphosphino)ferrocene palladium dichloride (II), palladium acetate and bis(cyanobenzene)palladium dichloride. In the present invention, the mass of the palladium catalyst is preferably 1 to 2.5% of the mass of the intermediate 2, and in specific embodiments, it can be 1%, 1.2%, 1.5%, 1.8%, 2%, 2.2% or 2.5%.

[0055] In the present invention, the organic amine preferably includes one or more of triethylamine, diethylamine and diisopropylamine. In the present invention, the mass ratio of the intermediate 2 to the organic amine is preferably 1:1-4, and in specific embodiments can be 1:1, 1:1.5, 1:2, 1:2.5, 1:3, 1:3.5 or 1:4.

[0056] In the present invention, the mass of the cuprous iodide is preferably 0.75-1% of the mass of the intermediate 2, and in specific embodiments may be 0.75%, 0.8%, 0.85%, 0.9%, 0.95% or 1%.

[0057] In the present invention, the second organic solvent preferably includes one or both of acetonitrile and tetrahydrofuran. In the present invention, the ratio of the mass of the intermediate 2 to the volume of the second organic solvent is preferably 1g:30-125mL, and in specific embodiments can be 1g:30mL, 1g:40mL, 1g:50mL, 1g:60mL, 1g:70mL, 1g:80mL, 1g:90mL, 1g:100mL, 1g:110mL, 1g:120mL or 1g:125mL.

[0058] In the present invention, the temperature of the second substitution reaction is preferably 10-25°C, and in specific embodiments it can be 10°C, 15°C, 20°C or 25°C; the time of the second substitution reaction is preferably 5-15h, and in specific embodiments it can be 5h, 6h, 7h, 8h, 9h, 10h, 11h, 12h, 13h, 14h or 15h.

[0059] In the present invention, the mixing and the second substitution reaction are preferably carried out under a protective atmosphere, and the protective atmosphere preferably includes nitrogen, argon or helium.

[0060] After completing the second substitution reaction, the present invention preferably further comprises: concentrating the reaction system obtained by the second substitution reaction under reduced pressure, adding water, extracting with an organic solvent, washing the obtained organic phase with water, washing with saturated brine, drying with a desiccant, filtering, concentrating the obtained filtrate and recrystallizing with methanol to obtain intermediate 3.

[0061] In the present invention, the ratio of the mass of the intermediate 2 to the volume of water (water added before organic solvent extraction) is preferably 1g:40-100mL, and in specific embodiments it can be 1g:40mL, 1g:50mL, 1g:60mL, 1g:70mL, 1g:80mL, 1g:90mL or 1g:100mL.

[0062] In the present invention, the number of extractions is preferably 2 to 5 times, and in specific embodiments it can be 2 times, 3 times, 4 times or 5 times; the ratio of the mass of the intermediate 2 to the volume of the organic solvent for a single extraction is preferably 1 g: 25 to 50 mL, and in specific embodiments it can be 1 g: 25 mL, 1 g: 30 mL, 1 g: 40 mL or 1 g: 50 mL; the organic solvent for extraction preferably includes one or more of dichloromethane, ethyl acetate and toluene.

[0063] In the present invention, the ratio of the mass of the intermediate 2 to the volume of the washing water is preferably 1g:25-125mL, and in specific embodiments it can be 1g:25mL, 1g:30mL, 1g:40mL, 1g:50mL, 1g:60mL, 1g:70mL, 1g:80mL, 1g:90mL, 1g:110mL, 1g:120mL or 1g:125mL.

[0064] In the present invention, the desiccant preferably includes anhydrous sodium sulfate and / or anhydrous magnesium sulfate.

[0065] After obtaining the intermediate 3, the present invention mixes the intermediate 3, an inorganic strong base and a third organic solvent to carry out a deprotection reaction to obtain 3,6-diethynylcarbazole.

[0066] In the present invention, the inorganic strong base preferably includes an alkali metal hydroxide, and more preferably includes at least one of sodium hydroxide and potassium hydroxide. In the present invention, the mass ratio of the intermediate 3 to the inorganic strong base is preferably 1:0.3-0.8, and in specific embodiments, it can be 1:0.3, 1:0.4, 1:0.5, 1:0.6, 1:0.7 or 1:0.8.

[0067] In the present invention, the third organic solvent preferably includes one or more of n-butanol, methanol and toluene. In the present invention, the ratio of the mass of the intermediate 3 to the volume of the third organic solvent is preferably 1g:10-25mL, and in specific embodiments can be 1g:10mL, 1g:15mL, 1g:20mL or 1g:25mL.

[0068] In the present invention, the temperature of the deprotection reaction is preferably 100-125°C, and in specific embodiments it can be 100°C, 105°C, 110°C, 115°C, 120°C or 125°C; the time of the deprotection reaction is preferably 10-30 min, and in specific embodiments it can be 10 min, 15 min, 20 min, 25 min or 30 min.

[0069] After the deprotection reaction is completed, the present invention preferably further comprises: cooling the reaction system obtained by the deprotection reaction to room temperature and then pouring it into ice water, adjusting the pH value to 3-5, extracting with an organic solvent, combining the organic phases, washing with water, washing with saturated brine, drying with a desiccant, filtering, concentrating the obtained filtrate and purifying it with a silica gel column to obtain 3,6-diethynylcarbazole.

[0070] In the present invention, the ratio of the mass of the intermediate 3 to the volume of ice water is preferably 1 g:20-50 mL, and in specific embodiments may be 1 g:20 mL, 1 g:30 mL, 1 g:40 mL or 1 g:50 mL.

[0071] In the present invention, the acid used to adjust the pH value preferably includes hydrochloric acid and / or sulfuric acid, and the concentration of the acid is preferably 5 to 15 mol / L, and in specific embodiments, it can be 5 mol / L, 8 mol / L, 10 mol / L, 12 mol / L or 15 mol / L. In the present invention, the pH value is preferably 3, 3.5, 4, 4.5 or 5.

[0072] In the present invention, the number of extractions is preferably 2 to 5 times, and in specific embodiments it can be 2 times, 3 times, 4 times or 5 times; the ratio of the mass of the intermediate 3 to the volume of the organic solvent for a single extraction is preferably 1g:50 to 100mL, and in specific embodiments it can be 1g:50mL, 1g:60mL, 1g:70mL, 1g:80mL, 1g:90mL or 1g:100mL; the organic solvent for extraction preferably includes one or more of dichloromethane, ethyl acetate and toluene.

[0073] In the present invention, the desiccant preferably includes anhydrous sodium sulfate and / or anhydrous magnesium sulfate.

[0074] In the present invention, the ratio of the mass of the intermediate 3 to the volume of the washing water is preferably 1g:30-100mL, and in specific embodiments it can be 1g:30mL, 1g:40mL, 1g:50mL, 1g:60mL, 1g:70mL, 1g:80mL, 1g:90mL or 1g:100mL.

[0075] In the present invention, the eluent used for the silica gel column purification preferably includes petroleum ether-ethyl acetate, petroleum ether-dichloromethane or n-hexane-ethyl acetate; the volume ratio of petroleum ether to ethyl acetate in the petroleum ether-ethyl acetate is preferably 8-15:1, and in a specific embodiment, it can be 8:1, 9:1, 10:1, 11:1, 12:1, 13:1, 14:1 or 15:1; the volume ratio of petroleum ether to dichloromethane in the petroleum ether-dichloromethane is preferably 10-15:1, and in a specific embodiment, it can be 10:1, 11:1, 12:1, 13:1, 14:1 or 15:1; the volume ratio of n-hexane to ethyl acetate in the n-hexane-ethyl acetate is preferably 8-15:1, and in a specific embodiment, it can be 8:1, 9:1, 10:1, 11:1, 12:1, 13:1, 14:1 or 15:1.

[0076] In route 1, 3,6-diiodo-9H-carbazole and trimethylsilyl acetylene are used as the initial raw materials, and the byproduct 3-iodo-6-((trimethylsilyl)ethynyl)-9H-carbazole is obtained. Since the polarity difference between the byproduct and 3,6-diethynyl carbazole is very small, it is very difficult to remove the byproduct, and the byproduct will also exist in the final 3,6-diethynyl carbazole after hydrolysis and cannot be purified cleanly, thereby affecting the performance of 3,6-diethynyl carbazole. In addition, the cost of iodinated raw materials is high, which will also increase the production cost of 3,6-diethynyl carbazole. In route 2, 3,6-diiodo-9H-carbazole and 2-methyl-3-butyn-2-ol are used as the initial raw materials, the reaction progress is very slow, and the reaction is very incomplete, the yield is low, and the reaction can only be fully achieved by consuming a large amount of metal target catalyst, which greatly increases the production cost of 3,6-diethynyl carbazole, which is not conducive to large-scale application. The present invention protects the NH group in 3,6-diiodocarbazole with Boc2O, so that the reaction is very easy to occur, and then the reaction is completed in a short time, the system has few by-products, the total yield of the product is high, and the post-processing is easy. The amount of palladium catalyst used is greatly reduced, thereby reducing the production cost of 3,6-diethynylcarbazole.

[0077] In order to further illustrate the present invention, the preparation method of 3,6-diethynylcarbazole provided by the present invention is described in detail below in conjunction with examples, but they should not be construed as limiting the scope of protection of the present invention.

[0078] Example 1

[0079]

[0080] Under nitrogen protection, 20 mL of dichloromethane, 3,6-diiodocarbazole (2 g, 4.77 mmol), and Boc2O (2.1 g, 9.62 mmol) were added to a 50 mL three-necked flask with magnetic stirring, the temperature was controlled at 15 ° C, 0.583 g of DMAP was added, and the reaction was stirred at room temperature for 6 h. The reaction was complete after TLC tracking. 25 mL of water was added, stirred, and separated to obtain an aqueous phase and an organic phase respectively; the aqueous phase was extracted with dichloromethane 3 times (30 mL each time), the organic phase and the dichloromethane extraction phase were combined, washed once with 25 mL of water, washed once with saturated brine, dried over anhydrous magnesium sulfate, filtered, concentrated under reduced pressure, filtered, the filter cake was rinsed with 5 mL of petroleum ether, and then recrystallized with methyl tert-butyl ether to obtain intermediate 2 (2.4 g, 4.62 mmol, yield 96.8%).

[0081] Under nitrogen protection, 100 mL of acetonitrile, bistriphenylphosphine palladium dichloride (27.2 mg, 0.0384 mmol), triethylamine (4 g, 39.5 mmol), intermediate 2 (2 g, 3.84 mmol), 2-methyl-3-butyn-2-ol (4.8 g, 57 mmol), and cuprous iodide (15.2 mg) were added to a three-necked flask with magnetic stirring, and the mixture was stirred at room temperature (15-25°C) for 7 h. The reaction was complete after TLC detection, and the mixture was concentrated under reduced pressure. 100 mL of water was added, and the mixture was extracted with ethyl acetate three times (50 mL each time), washed once with 100 mL of water, washed once with saturated brine, dried over anhydrous magnesium sulfate, filtered, concentrated the filtrate, and recrystallized from methanol to obtain intermediate 3 (1.6 g, yield was 96.25%, purity was 98.8%). The NMR of intermediate 3 is shown in Figure 1 .

[0082] Add 10 mL of n-butanol and potassium hydroxide (0.66 g) to a three-necked flask with magnetic stirring, raise the temperature to about 60°C, and the system dissolves and becomes a colorless liquid. The temperature rises to 118°C, refluxes, and intermediate 3 (1 g, 2.32 mmol) is added. The reaction is completed for 15 min, and TLC tracking shows that the reaction is complete. After cooling to room temperature, pour into 25 mL of ice water, adjust the pH value to 4 with hydrochloric acid (6 mol / L), extract with ethyl acetate 3 times (50 mL each time), combine the organic phases, wash once with 50 mL of water, wash once with saturated brine, dry over anhydrous magnesium sulfate, filter, concentrate, and purify on a silica gel column (volume ratio of petroleum ether: ethyl acetate = 10:1) to obtain 3,6-diethynylcarbazole (off-white solid, 0.47 g, yield is 94%, purity is 99.5%). The NMR of 3,6-diethynylcarbazole is shown in Figure 2 .

[0083] Example 2

[0084] Under nitrogen protection, 0 mL of dichloromethane, 3,6-diiodocarbazole (3.2 g, 7.63 mmol), and Boc2O (3.33 g, 15.26 mmol) were added to a three-necked flask with magnetic stirring, the temperature was controlled at 15°C, DMAP (0.95 g) was added, and the reaction was stirred at room temperature (15-25°C) for 7 hours. The reaction was complete by TLC tracking. 50 mL of water was added, stirred, and separated to obtain an aqueous phase and an organic phase respectively; the aqueous phase was extracted with dichloromethane 3 times (150 mL each time), the organic phase and the dichloromethane extraction phase were combined, washed once with 50 mL of water, washed once with saturated brine, dried over anhydrous magnesium sulfate, filtered to remove the desiccant, concentrated under reduced pressure, filtered, the filter cake was rinsed with 10 mL of petroleum ether, and recrystallized with methyl tert-butyl ether to obtain intermediate 2 (3.8 g, 7.32 mmol, yield 95.6%).

[0085] Under nitrogen protection, ethyltetrahydrofuran (50 mL), tetrakis(triphenylphosphine)palladium (26.6 mg, 0.023 mmol), triethylamine (2.4 g, 23.7 mmol), intermediate 2 (1.2 g, 2.3 mmol), 2-methyl-3-butyn-2-ol (2.88 g, 34.2 mmol), and 9.0 mg of cuprous iodide were added to a three-necked flask with magnetic stirring. The mixture was stirred at room temperature (15-25° C.) for 5 h. The reaction was complete when detected by TLC. The mixture was concentrated under reduced pressure, 50 mL of water was added, and the mixture was extracted with dichloromethane 3 times (50 mL each time), washed once with 50 mL of water, washed once with saturated brine, dried over anhydrous magnesium sulfate, filtered, and the filtrate was concentrated. The mixture was recrystallized from isopropanol to obtain intermediate 3 (0.93 g, yield was 93.2%, purity was 98.3%).

[0086] 10 mL of methanol and 0.46 g of potassium hydroxide were added to a three-necked flask with magnetic stirring, the temperature was raised to 110°C, intermediate 3 (0.7 g, 1.62 mmol) was added, and the reaction was completed for 18 min. The system was cooled to room temperature and poured into 20 mL of ice water. The pH value was adjusted to 4 with hydrochloric acid, and extracted with ethyl acetate 3 times (50 mL each time). The organic phases were combined, washed once with 30 mL of water, washed once with saturated brine, dried over anhydrous magnesium sulfate, filtered, concentrated, and purified on a silica gel column (n-hexane: ethyl acetate volume ratio = 10:1) to obtain 3,6-diethynylcarbazole (off-white solid, 0.32 g, yield 91.2%, purity 99.2%).

[0087] The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principle of the present invention. These improvements and modifications should also be regarded as the scope of protection of the present invention.

Claims

1. A method for preparing 3,6-diethynylcarbazole, characterized in that: The following steps are involved: Mixing 3,6-diiodocarbazole, Boc2O, a catalyst and a first organic solvent to perform a first substitution reaction to obtain an intermediate 2; The intermediate 2, 2-methyl-3-butyn-2-ol, a palladium catalyst, an organic amine, cuprous iodide and a second organic solvent are mixed to carry out a second substitution reaction to obtain an intermediate 3; The intermediate 3, an inorganic strong base and a third organic solvent are mixed to carry out a deprotection reaction to obtain 3,6-diethynylcarbazole; 2. The preparation method according to claim 1, characterized in that: The catalyst includes one or more of an organic amine, an alkali metal fluoride and an alkali metal hydroxide; The first organic solvent includes one or more of dichloromethane, chloroform, tetrahydrofuran, toluene and dioxane.

3. The preparation method according to claim 1, characterized in that: The mass ratio of 3,6-diiodocarbazole to Boc2O is 1:0.7-1.3; The mass ratio of the 3,6-diiodocarbazole to the catalyst is 1:0.25-0.

45.

4. The preparation method according to any one of claims 1 to 3, characterized in that: The temperature of the first substitution reaction is 10-25° C. and the time is 5-10 hours.

5. The preparation method according to claim 1, characterized in that: The palladium catalyst comprises one or more of bis(triphenylphosphine)palladium dichloride, tetrakis(triphenylphosphine)palladium, 1,1'-bis(diphenylphosphino)ferrocenepalladium dichloride (II), palladium acetate and bis(cyanobenzene)palladium dichloride; The second organic solvent includes one or both of acetonitrile and tetrahydrofuran.

6. The preparation method according to claim 1, characterized in that: The mass ratio of the intermediate 2 to 2-methyl-3-butyn-2-ol is 1:1-3; The mass of the palladium catalyst is 1 to 2.5% of the mass of the intermediate 2; The mass ratio of the intermediate 2 to the organic amine is 1:1-4; The mass of the cuprous iodide is 0.75-1% of the mass of the intermediate 2.

7. The preparation method according to claim 1, 5 or 6, characterized in that: The temperature of the second substitution reaction is 10-25° C. and the time is 5-15 hours.

8. The preparation method according to claim 1, characterized in that: The inorganic strong base includes an alkali metal hydroxide; The third organic solvent includes one or more of n-butanol, methanol and toluene.

9. The preparation method according to claim 1, characterized in that: The mass ratio of the intermediate 3 to the inorganic strong base is 1:0.3-0.

8.

10. The preparation method according to claim 1, characterized in that: The temperature of the deprotection reaction is 100-125° C., and the time is 10-30 minutes.

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