Preparation method of 1,3,5-tris(9-carbazolyl)benzene

Abstract

The present invention relates to a preparation method of 1,3,5-tris(9-carbazolyl)benzene, belonging to the technical field of organic synthesis. The present invention uses 1,3,5-trichlorobenzene and carbazole as raw materials, [2-(2,4,6-triisopropyl-3-(4-methoxyphenyl)phenyl)-6-(2,4,6-triisopropylphenyl)phenyl]-dicyclohexylphosphine and {[2-(2,4,6-triisopropyl-3-(4-methoxyphenyl)phenyl)-6-(2,4,6-triisopropylphenyl)phenyl]-dicyclohexylphosphine}(allyl-η3)trifluoromethanesulfonate palladium(II) as catalysts, and catalyzes carbon-nitrogen coupling to prepare 1,3,5-tris(9-carbazolyl)benzene under the conditions of an organomagnesium reagent and an inert gas atmosphere. The method of the present invention has the advantages of low cost, simple operation, high yield, good environmental protection, etc., and has broad application prospects.

Description

Technical Field

[0001] The invention belongs to the technical field of organic synthesis, and in particular relates to a method for preparing 1,3,5-tris(9-carbazolyl)benzene. Background Art

[0002] Polycarbazolyl organic compounds are commonly used in the research and application of organic optoelectronic materials. 1,3,5-Tris(9-carbazolyl)benzene is a common chemical component of OLED devices. Traditionally, its preparation relies on the copper-catalyzed Ullmann reaction, but this method requires high reaction temperatures, large amounts of Cu catalyst, and the presence of heavy metal residues, resulting in a product with insufficient purity that fails to meet the requirements of many optoelectronic materials.

[0003] In the 1990s, palladium-catalyzed CN coupling reactions gradually entered the field of vision of chemists, especially Professor Hartwig and Professor Buchwald of MIT who conducted the most in-depth research on this type of reaction. At present, this type of palladium-catalyzed CN coupling reaction is also called Buchwald-Hartwig coupling amination reaction, which has been widely used in the amination reaction of aryl halides. There are few literature reports on palladium-catalyzed coupling reactions of carbazole and aryl halides. For details, see [1) G Mann, et al., J. Am. Chem. Soc., 1998, 120, 827; 2) J F Hartwig, et al., J. Org. Chem., 1999, 64, 5575; 3) D. W Old, et al., Org. Lett., 2002, 2, 1403; 4) M. Watanabe, et al., Tetrahedron [5] GA. Grasa, et al., J. Org. Chem., 2001, 66, 7729; [6] K. Suzuki, et al., Adv. Synth. Catal., 2008, 350, 652.] The main reason is the p-π conjugation between the nitrogen atom and the benzene ring in carbazole, which reduces the nucleophilicity of the nitrogen atom. In these reported literature, the amount of catalyst used is often as high as 5%.

[0004] With the gradual improvement of synthesis technology, in 2013, Japan's Takasago Corporation described in patent WO2013032035A1 that its phosphine ligand, (2,2-diphenyl-1-methyl-cyclopropyl-1)-di-tert-butylphosphine (cBRIDP), outperformed the biphenyl phosphine ligand developed by Buchwald et al. at MIT in the palladium-catalyzed coupling reaction of carbazole with chloroaryl hydrocarbons. This technology is currently the world's most advanced for the preparation of N-arylcarbazole derivatives. Takasago's patents and literature (Y. Nakayama, et al., Adv. Synth. Catal. 2015, 357, 322) describe a process in which 1,3,5-trichlorobenzene reacts with carbazole using a catalytic system comprising 0.3 mol% allylpalladium chloride and 0.6 mol% cBRIDP phosphine ligand under heating and reflux at 110°C. Using 3.06 equivalents of methylmagnesium chloride as a base, 1,3,5-tris(9-carbazolyl)benzene is obtained in a 95% yield.

[0005] In 2018, the domestic Dongguan Juncheng High-tech Materials Co., Ltd. disclosed in patent CN 111039923A that 2,6-bis(2,4,6-triisopropyl-phenyl)phenyl-dicyclohexylphosphine (TXPhos) has excellent performance in the palladium-catalyzed CN coupling reaction of primary aromatic amines (a) F Zhou, L. Zhang, J.-c. Shi, J. Catal. 402 (2021) 238-243) (b) F. Zhou, L. Zhang, W Hu, B. Yuan, J.-c. Shi, J. Catal. 422 (2023) 36-42), significantly broadening the substrate range and reducing the catalyst dosage, and breaking through the range of bases. In many reactions, KHCO3 and KOAc are the best base choices. It also has excellent performance in the CN coupling reaction of secondary aromatic amines and is the best supporting ligand for many substrates including carbazole (CN111056986A, CN1 11039848A and CN1 11039923A). However, the amount of Pd catalyst used in this patent is still relatively high.

[0006] Since palladium metal is scarce and expensive, developing coupling reaction processes with low catalyst dosage is an important topic in green chemistry research. Summary of the Invention

[0007] In order to solve the above technical problems, the present invention proposes a new method for preparing 1,3,5-tris(9-carbazolyl)benzene.

[0008] One of the technical solutions of the present invention:

[0009] The present invention provides a phosphine ligand, the chemical name of which is [2-(2,4,6-triisopropyl-3-(4-methoxyphenyl)phenyl)-6-(2,4,6-triisopropylphenyl)phenyl]-dicyclohexylphosphine (TAIPhos), and the structural formula thereof is as follows:

[0010]

[0011] The second technical solution of the present invention:

[0012] The present invention provides a method for preparing the phosphine ligand: sodium phenolate, tetrahydrofuran and 4-methoxychlorobenzene are added to [2,6-bis(2,4,6-triisopropyl-phenyl)phenyl-dicyclohexylphosphine](allyl-η3)palladium(II) chloride, the mixture is heated for reaction, and after the reaction is complete, the mixture is passed through diatomaceous earth and then subjected to column chromatography to obtain the phosphine ligand. In the above reaction, [2,6-bis(2,4,6-triisopropyl-phenyl)phenyl-dicyclohexylphosphine](allyl-η3)palladium(II) chloride is added to sodium phenolate. The alkaline conditions activated the zero-valent palladium species, which then underwent an oxidative addition reaction with 4-methoxychlorobenzene to generate [2,6-bis(2,4,6-triisopropyl-phenyl)phenyl-dicyclohexylphosphine](4-methoxyphenyl)palladium(II) chloride. Subsequently, under the same reaction conditions, the hydrogen at the 3-position on the benzene ring containing the 2,4,6-triisopropyl group was activated by the Pd complex formed by the oxidative addition, enabling it to react with 4-methoxychlorobenzene to finally generate TAlPhos.

[0013] Preferably, in the method for preparing the phosphine ligand, the heating reaction temperature is 80° C. and the time is 2 hours.

[0014] More preferably, the preparation method of the phosphine ligand is: add 860 mg of [2,6-bis(2,4,6-triisopropyl-phenyl)phenyl-dicyclohexylphosphine](allyl-η3)palladium(II) chloride into a pressure tube, add 116 mg of sodium phenolate, 2 mL of tetrahydrofuran and 142 mg of 4-methoxychlorobenzene, heat at 80°C for 2 hours, pass through diatomaceous earth after the reaction is complete, and obtain the phosphine ligand by column chromatography.

[0015] The third technical solution of the present invention:

[0016] The present invention also provides a palladium complex of a phosphine ligand, the chemical name of which is {[2-(2,4,6-triisopropyl-3-(4-methoxyphenyl)phenyl)-6-(2,4,6-triisopropylphenyl)phenyl]-dicyclohexylphosphine}(allyl-η3)trifluoromethanesulfonate palladium (ID(TAlPhos palladium complex), and the structural formula is as follows:

[0017]

[0018] The fourth technical solution of the present invention:

[0019] The present invention also provides a preparation method of the palladium complex of the phosphine ligand, which comprises the following steps: adding allyl palladium dimer and silver trifluoromethanesulfonate into a dry pressure-resistant tube, adding tetrahydrofuran, and stirring at room temperature for 2 hours to generate allyl palladium trifluoromethanesulfonate, then adding [2-(2,4,6-triisopropyl-3-(4-methoxyphenyl)phenyl)-6-(2,4,6-triisopropylphenyl)phenyl]-dicyclohexylphosphine, and stirring at room temperature for 2 hours to fully complex the phosphine ligand with the allyl palladium trifluoromethanesulfonate, and after the reaction is complete, passing through diatomaceous earth and drying in a rotary evaporation cycle to obtain the palladium complex of the phosphine ligand.

[0020] Preferably, in the preparation method of the palladium complex of the phosphine ligand, the molar ratio of the allyl dimer palladium, silver trifluoromethanesulfonate and [2-(2,4,6-triisopropyl-3-(4-methoxyphenyl)phenyl)-6-(2,4,6-triisopropylphenyl)phenyl]-dicyclohexylphosphine is 1:2:2.

[0021] More preferably, the preparation method of the palladium complex of the phosphine ligand is as follows: allyl palladium dimer (0.18 g, 0.5 mmol) and silver trifluoromethanesulfonate (0.26 g, 1.0 mmol) are added to a dry 15 mL pressure tube, 2 mL of tetrahydrofuran is added, and the mixture is stirred at room temperature for 30 min, and then [2-(2,4,6-triisopropyl-3-(4-methoxyphenyl)phenyl)-6-(2,4,6-triisopropylphenyl)phenyl]-dicyclohexylphosphine (0.76 g, 1.0 mmol) is added and stirred for 2 h. After the reaction is complete, the mixture is passed through diatomaceous earth and dried to obtain the palladium complex of the phosphine ligand.

[0022] The fifth technical solution of the present invention:

[0023] The present invention also provides a 1,3,5-tris(9-carbazolyl)benzene Preparation method: 1,3,5-trichlorobenzene and carbazole As a raw material, an organic magnesium reagent, the phosphine ligand and the palladium complex of the phosphine ligand are added to prepare the 1,3,5-tris(9-carbazolyl)benzene through a carbon-nitrogen coupling (CN coupling) reaction.

[0024] Preferably, the preparation method of 1,3,5-tris(9-carbazolyl)benzene comprises the following steps:

[0025] Under an inert atmosphere, a stirring bar is added to a dry Schlenk flask, carbazole and xylene are added, and the mixture is cooled to 5° C., an organic magnesium reagent is added dropwise, and the mixture is stirred for reaction after the addition is completed. After the reaction is completed, the mixture is transferred to a glove box; in the glove box, 1,3,5-trichlorobenzene, the palladium complex of the phosphine ligand, the phosphine ligand and an organic solvent are added to another pressure-resistant tube, and the reaction liquid in the Schlenk flask is transferred to the pressure-resistant tube at room temperature, and the mixture is reacted in an oil bath. After the reaction is completed, the mixture is separated and purified to obtain the 1,3,5-tris(9-carbazolyl)benzene.

[0026] The present invention designs and synthesizes a new phosphine ligand, namely [2-(2,4,6-triisopropyl-3-(4-methoxyphenyl)phenyl)-6-(2,4,6-triisopropylphenyl)phenyl]-dicyclohexylphosphine (TAlPhos), and a palladium complex supported by it, namely {[2-(2,4,6-triisopropyl-3-(4-methoxyphenyl)phenyl)-6-(2,4,6-triisopropylphenyl)phenyl]-dicyclohexylphosphine}(allyl-η3)trifluoromethanesulfonate palladium(II) (TAlPhos palladium complex). By adding a 4-methoxyphenyl group to the 3-position of the 2,4,6-triisopropylphenyl ring, the steric hindrance of the phosphorus atom on the phosphine ligand is increased. As the steric hindrance of the phosphorus atom increases, the performance of the palladium catalyst is greatly improved compared with the prior art due to the principle that the dicyclohexyl group itself is electron-rich. Whether compared with the cBRIDP series ligand catalysts of Takasago Co., Ltd. or the terphenylphosphine TXPhos series catalysts in CN111039923 A, the method for preparing 1,3,5-tris(9-carbazolyl)benzene by carbon-nitrogen coupling using 1,3,5-trichlorobenzene and carbazole as raw materials using a palladium catalyst of the present invention can not only significantly reduce the amount of palladium used, but also obtain 1,3,5-tris(9-carbazolyl)benzene in high yield, thereby greatly reducing the cost.

[0027] Preferably, in the method for preparing 1,3,5-tris(9-carbazolyl)benzene, the molar ratio of 1,3,5-trichlorobenzene to the palladium complex of the phosphine ligand is 1:0.0003.

[0028] Preferably, in the preparation method of 1,3,5-tris(9-carbazolyl)benzene, the molar ratio of the phosphine ligand to the palladium complex of the phosphine ligand is (1-3):1.

[0029] Preferably, in the preparation method of 1,3,5-tris(9-carbazolyl)benzene, the molar ratio of 1,3,5-trichlorobenzene to carbazole is 1:(3.0-3.3).

[0030] Preferably, in the method for preparing 1,3,5-tris(9-carbazolyl)benzene, the molar ratio of carbazole to the organomagnesium reagent is 1:(1-1.1).

[0031] Preferably, in the preparation method of 1,3,5-tris(9-carbazolyl)benzene, the organomagnesium reagent is RM[gX; wherein R is selected from methyl or isopropyl; X is selected from chlorine or bromine; more preferably isopropylmagnesium bromide or methylmagnesium chloride.

[0032] Preferably, in the method for preparing 1,3,5-tris(9-carbazolyl)benzene, the organic solvent is selected from at least one of tetrahydrofuran (THF), dioxane, toluene, and xylene, and the organic solvent contains THF. That is, the present invention introduces the solvent tetrahydrofuran when adding the organomagnesium reagent. Therefore, the organic solvent here is preferably tetrahydrofuran and toluene or xylene; or dioxane, tetrahydrofuran and toluene or xylene.

[0033] In the present invention, both isopropylmagnesium bromide and methylmagnesium chloride react with carbazole to generate the same N-Mg species and isopropane and methane, respectively. The N-Mg species involved in the catalytic cycle are the same, so the difference in the types of the two Grignard reagents has no practical effect on the reaction process and results, and there is no significant difference in the yield of 1,3,5-tris(9-carbazolyl)benzene.

[0034] Preferably, in the preparation method of 1,3,5-tris(9-carbazolyl)benzene, when heating under reflux in an oil bath, the reaction temperature is 100-150°C for 6 hours, and more preferably the reaction temperature is 110°C.

[0035] The 1,3,5-tris(9-carbazolyl)benzene prepared by the method of the present invention can be used in the fields of medicine or agricultural chemical products, organic photoconductor materials, organic electroluminescent element materials, etc. at low cost and high efficiency.

[0036] Compared with the prior art, the present invention has the following advantages and technical effects:

[0037] The present invention uses 1,3,5-trichlorobenzene and carbazole as raw materials, [2-(2,4,6-triisopropyl-3-(4-methoxyphenyl)phenyl)-6-(2,4,6-triisopropylphenyl)phenyl]-dicyclohexylphosphine and {[2-(2,4,6-triisopropyl-3-(4-methoxyphenyl)phenyl)-6-(2,4,6-triisopropylphenyl)phenyl]-dicyclohexylphosphine}(allyl-η3)trifluoromethanesulfonate palladium(II) as catalysts, and catalyzes carbon-nitrogen coupling under the conditions of an organomagnesium reagent and an inert gas atmosphere to prepare 1,3,5-tris(9-carbazolyl)benzene. The method of the present invention has the advantages of low cost, simple operation, high yield, good environmental protection, and the like, and has broad application prospects. DETAILED DESCRIPTION

[0038] Various exemplary embodiments of the present invention will now be described in detail. This detailed description should not be considered as limiting the present invention, but rather as a more detailed description of certain aspects, features, and embodiments of the present invention.

[0039] It should be understood that the terms described herein are intended only to describe particular embodiments and are not intended to limit the present invention. In addition, for numerical ranges herein, it should be understood that each intermediate value between the upper and lower limits of the range is also specifically disclosed. Each smaller range between any intermediate value within a stated value or stated range and any other stated value or intermediate value within the stated range is also encompassed by the present invention. The upper and lower limits of these smaller ranges may be independently included or excluded within the scope.

[0040] Unless otherwise indicated, all technical and scientific terms used herein have the same meaning as commonly understood by those skilled in the art. Although only preferred methods and materials are described herein, any methods and materials similar or equivalent to those described herein may also be used in the practice or testing of the present invention. All documents mentioned in this specification are incorporated by reference to disclose and describe the methods and / or materials associated with the documents. In the event of any conflict with any incorporated document, the contents of this specification shall prevail.

[0041] It will be apparent to those skilled in the art that various modifications and variations may be made to the specific embodiments described herein without departing from the scope or spirit of the invention. Other embodiments will be apparent to those skilled in the art from the description of the invention. The description and examples are intended to be illustrative only.

[0042] The words “include,” “including,” “have,” “contain,” etc. used in this document are open-ended terms, meaning including but not limited to.

[0043] Unless otherwise specified, the room temperature in the present invention is 25±2°C.

[0044] In an embodiment of the present invention, the preparation method of [2-(2,4,6-triisopropyl-3-(4-methoxyphenyl)phenyl)-6-(2,4,6-triisopropylphenyl)phenyl]-dicyclohexylphosphine (TAlPhos) is as follows: 860 mg of [2,6-bis(2,4,6-triisopropyl-phenyl)phenyl-dicyclohexylphosphine](allyl-η3)palladium(II) chloride is added to a pressure tube, 116 mg of sodium phenolate, 2 mL of tetrahydrofuran and 142 mg of 4-methoxychlorobenzene are added, and the mixture is heated at 80° C. for 2 h. After the reaction is complete, the mixture is passed through diatomaceous earth and subjected to column chromatography to obtain TAlPhos, whose structural formula is as follows:

[0045]

[0046] In an embodiment of the present invention, the preparation method of {[2-(2,4,6-triisopropyl-3-(4-methoxyphenyl)phenyl)-6-(2,4,6-triisopropylphenyl)phenyl]-dicyclohexylphosphine}(allyl-η3)trifluoromethanesulfonate palladium(II) (TAIPhos palladium complex) is as follows: allyl dimer palladium (0.18 g, 0.5 mmol), trifluoromethanesulfonate silver (0.26 g, 1.0 mmol) 1) was added to a dry 15 mL pressure tube, 2 mL of tetrahydrofuran was added, and the mixture was stirred at room temperature for 30 min. Then, [2-(2,4,6-triisopropyl-3-(4-methoxyphenyl)phenyl)-6-(2,4,6-triisopropylphenyl)phenyl]-dicyclohexylphosphine (0.76 g, 1.0 mmol) was added and stirred for 2 h. After the reaction was complete, the mixture was passed through celite and dried to obtain a TAlPhos palladium complex having the following structural formula:

[0047]

[0048] In the embodiments of the present invention, except for TAlPhos and TAlPhos palladium complex, other raw materials and solvents are purchased. As examples, carbazole CAS No. 86-74-8; xylene CAS No. 1330-20-7; tetrahydrofuran CAS No. 109-99-9; dioxane CAS No. 123-91-1; toluene CAS No. 108-88-3; methylmagnesium chloride CAS No. 676-58-4; isopropylmagnesium bromide CAS No. 920-39-8; 1,3,5-trichlorobenzene CAS No. 108-70-3; dodecane CAS No. 112-40-3; 4-methoxychlorobenzene CAS No. 824-94-2; [2, 6-bis(2,4,6-triisopropyl-phenyl)phenyl-dicyclohexylphosphine](allyl-η3)palladium chloride (ID CAS No. 2376379-97-2; sodium phenolate CAS No. 139-02-6. Carbazole, xylene, tetrahydrofuran, dioxane, toluene, methylmagnesium chloride, isopropylmagnesium bromide, 1,3,5-trichlorobenzene, dodecane, 4-methoxychlorobenzene, [2,6-bis(2,4,6-triisopropyl-phenyl)phenyl-dicyclohexylphosphine](allyl-η3)palladium chloride (ID and sodium phenolate were purchased from Shanghai Titan Technology Co., Ltd.

[0049] The technical solution of the present invention is further illustrated by the following examples.

[0050] Example 1 Preparation of [2-(2,4,6-triisopropyl-3-(4-methoxyphenyl)phenyl)-6-(2,4,6-triisopropylphenyl)phenyl]-dicyclohexylphosphine (TAIPhos)

[0051] 860 mg of [2,6-bis(2,4,6-triisopropyl-phenyl)phenyl-dicyclohexylphosphine](allyl-η3)palladium chloride (ID) was added to a pressure tube, and 116 mg of sodium phenolate, 2 mL of tetrahydrofuran and 142 mg of 4-methoxychlorobenzene were added. The mixture was heated at 80° C. for 2 h. After the reaction was complete, the mixture was filtered through celite and column chromatography to obtain 0.62 g of TAlPhos with a yield of 78.98%. The melting point was 213.9-217.4° C., and the structural formula was as follows:

[0052]

[0053] 1 H NMR (400MHz, CDCl3) δ7.26-7.14 (m, 4H), 7.09 (dd, J=13.6, 7.5Hz, 2H), 7.03 (d, J=5.0Hz, 2H ), 6.91 (d, J=8.0Hz, 2H), 3.87 (s, 3H), 3.01 (p, J=9.7, 8.4Hz, 1H), 2.93 (p, J=7.0Hz, 1H), 2.7 5 (dp, J=13.8, 6.9Hz, 2H), 2.63 (p, J=6.6Hz, 1H), 2.52 (p, J=6.7Hz, 1H), 1.79 (d, J=35.0Hz, 3H), 1.53 (s, 5H), 1.33 (dd, J=18.5, 6.8Hz, 19H), 1.22-0.74 (m, 31H), 0.67 (d, J=7.1Hz, 3H).

[0054] 13C NMR (101MHz, CDCl3) δ158.2, 148.5, 148.3, 147.5, 147.4, 147.2, 145.7, 145.4, 142.4, 140.5, 140.4, 139.3, 139.2, 137.7, 13 7.4, 137.3, 133.9, 132.9, 132.0, 132.0, 132.0, 131.9, 131.8, 131.8, 131.7, 126.3, 121.1, 120.9, 120.7, 119.5, 119.1, 112. 5,112.2,55.2,34.5,34.2,34.1,33.4,33.2,32.5,31.9,31.7,31.7,31.6,31.1,31.0,31.0,30.8,30.7,30.4,30.3,29.4,27.6,27.6,27.3,27.3,27.2,27.1,27.0,26.4,26.3,26.2,25.9,25.8,24.4,24.4,24.3,24.2,24.1,23.7,23.4,22.9,22.9.

[0055] 31 P NMR (162 MHz, CDCl3) δ 10.1.

[0056] Example 2 Preparation of {[2-(2,4,6-triisopropyl-3-(4-methoxyphenyl)phenyl)-6-(2,4,6-triisopropylphenyl)phenyl]-dicyclohexylphosphine}(allyl-η3)trifluoromethanesulfonate palladium(II) (TAIPhos palladium complex)

[0057] Allyl dimer palladium (0.18 g, 0.5 mmol) and silver trifluoromethanesulfonate (0.26 g, 1.0 mmol) were added to a dry 15 mL pressure tube, and 2 mL of tetrahydrofuran was added. The mixture was stirred at room temperature for 30 min, and then [2-(2,4,6-triisopropyl-3-(4-methoxyphenyl)phenyl)-6-(2,4,6-triisopropylphenyl)phenyl]-dicyclohexylphosphine (0.76 g, 1.0 mmol) was added. The mixture was stirred for 2 h. After the reaction was complete, the mixture was passed through celite and dried to obtain 1.07 g of TAlPhos palladium complex with a yield of 99.98%. Its structural formula is as follows:

[0058]

[0059] 31 p NMR (162MHz, CDCl3) δ: 69.3.

[0060] Example 3 Preparation of 1,3,5-tris(9-carbazolyl)benzene

[0061] Under an inert atmosphere (nitrogen, the same below), a stirrer was added to a dry 50 mL Schlenk flask, carbazole (0.552 g, 3.3 mmol) and xylene (3 mL), and the flask was cooled to 5°C. Methylmagnesium chloride (3.0 M in THF, 3.5 mmol, 1.15 mL) was added dropwise via syringe (about 1.5 min). After addition, the mixture was stirred for 15 min and transferred to a glove box for later use.

[0062] In a glove box, 1,3,5-trichlorobenzene (0.181 g, 1.0 mmol), {[2-(2,4,6-triisopropyl-3-(4-methoxyphenyl)phenyl)-6-(2,4,6-triisopropylphenyl)phenyl]-dicyclohexylphosphine}(allyl-η3)trifluoromethanesulfonate palladium(II) (0.33 mg, 0.0003 mmol) prepared in Example 2, [2-(2,4,6-triisopropyl-3-(4-methoxyphenyl)phenyl)-6-(2,4,6-triisopropylphenyl)phenyl]-dicyclohexylphosphine (0.23 mg, 0.0003 mmol) prepared in Example 1, 0.13 mL of dodecane (as an internal standard for GC analysis), and 1 mL of xylene were added to another pressure tube. The reaction solution in the Schlenk flask was transferred to the pressure tube at room temperature, sealed, and heated under reflux in an oil bath at 110°C for 6 h. The reaction solution was filtered through silica gel and celite, and the filtrate was concentrated under reduced pressure. The residue was separated and purified by silica gel column chromatography (petroleum ether:ethyl acetate = 10:1 (volume ratio, the same below)) to obtain 0.573 g of a white solid, which was 1,3,5-tris(9-carbazolyl)benzene, with a yield of 99.88%.

[0063] 1 H NMR (400MHz, CDCl3) δ: 8.19 (d, J=7.5Hz, 6H), 7.99 (s, 3H), 7.70 (d, J=8.2Hz, 6 H), 7.50 (ddd, J=8.3, 7.3, 1.2Hz, 6H), 7.39-7.32 (ddd, J=7.8, 6.8, 0.9Hz, 6H).

[0064] 13 C NMR (101MHz, CDCl3) δ: 140.82, 140.35, 126.41, 123.88, 123.57, 120.78, 120.63, 109.70.

[0065] Example 4 Preparation of 1,3,5-tris(9-carbazolyl)benzene

[0066] Under an inert atmosphere, a stirrer was placed in a dry 50 mL Schlenk flask, and carbazole (0.552 g, 3.3 mmol) and xylene (3 mL) were added. The flask was cooled to 5°C, and methylmagnesium chloride (3.0 M inTHF, 3.5 mmol, 1.15 mL) was added dropwise via syringe (approximately 1.5 min). After addition, the flask was stirred for 15 min and transferred to a glove box for later use.

[0067] In a glove box, 1,3,5-trichlorobenzene (0.181 g, 1.0 mmol), {[2-(2,4,6-triisopropyl-3-(4-methoxyphenyl)phenyl)-6-(2,4,6-triisopropylphenyl)phenyl]-dicyclohexylphosphine}(allyl-η3)trifluoromethanesulfonatepalladium(II) (0.33 mg, 0.0003 mmol) prepared in Example 2, [2-(2,4,6-triisopropyl-3-(4-methoxyphenyl)phenyl)-6-(2,4,6-triisopropylphenyl)phenyl]-dicyclohexylphosphine (0.46 mg, 0.0006 mmol) prepared in Example 1, 0.13 mL of dodecane (as an internal standard for GC analysis), and 1 mL of toluene were added to another pressure tube. The reaction solution in the Schlenk flask was transferred to the pressure tube at room temperature, sealed, and heated under reflux in an oil bath at 110°C for 6 h. The reaction solution was filtered through silica gel and celite, and the filtrate was concentrated under reduced pressure. The residue was separated and purified by silica gel column chromatography (petroleum ether:ethyl acetate=10:1) to obtain 0.573 g of a white solid, namely 1,3,5-tris(9-carbazolyl)benzene, with a yield of 99.88%.

[0068] Example 5 Preparation of 1,3,5-tris(9-carbazolyl)benzene

[0069] Under an inert atmosphere, a stirrer was placed in a dry 50 mL Schlenk flask, and carbazole (0.552 g, 3.3 mmol) and xylene (3 mL) were added. The flask was cooled to 5°C, and methylmagnesium chloride (3.0 M inTHF, 3.5 mmol, 1.15 mL) was added dropwise via syringe (approximately 1.5 min). After addition, the flask was stirred for 15 min and transferred to a glove box for later use.

[0070] In a glove box, 1,3,5-trichlorobenzene (0.181 g, 1.0 mmol), {[2-(2,4,6-triisopropyl-3-(4-methoxyphenyl)phenyl)-6-(2,4,6-triisopropylphenyl)phenyl]-dicyclohexylphosphine}(allyl-η3)trifluoromethanesulfonate palladium(II) (0.33 mg, 0.0003 mmol) prepared in Example 2, [2-(2,4,6-triisopropyl-3-(4-methoxyphenyl)phenyl)-6-(2,4,6-triisopropylphenyl)phenyl]-dicyclohexylphosphine (0.69 mg, 0.0009 mmol) prepared in Example 1, 0.13 mL of dodecane (as an internal standard for GC analysis), and 1 mL of tetrahydrofuran were added to another pressure tube. The reaction solution in the Schlenk flask was transferred to the pressure tube at room temperature, sealed, and heated under reflux in an oil bath at 110°C for 6 h. The reaction solution was filtered through silica gel and celite, and the filtrate was concentrated under reduced pressure. The residue was separated and purified by silica gel column chromatography (petroleum ether:ethyl acetate=10:1) to obtain 0.572 g of a white solid, namely 1,3,5-tris(9-carbazolyl)benzene, with a yield of 99.70%.

[0071] Example 6 Preparation of 1,3,5-tris(9-carbazolyl)benzene

[0072] Under an inert atmosphere, a stirrer was placed in a dry 50 mL Schlenk flask, and carbazole (0.552 g, 3.3 mmol) and toluene (3 mL) were added. The flask was cooled to 5°C, and methylmagnesium chloride (3.0 M in THF, 3.5 mmol, 1.15 mL) was added dropwise via syringe (approximately 1.5 min). After addition, the flask was stirred for 15 min and transferred to a glove box for later use.

[0073] In a glove box, 1,3,5-trichlorobenzene (0.181 g, 1.0 mmol), {[2-(2,4,6-triisopropyl-3-(4-methoxyphenyl)phenyl)-6-(2,4,6-triisopropylphenyl)phenyl]-dicyclohexylphosphine}(allyl-η3)trifluoromethanesulfonate palladium(II) (0.33 mg, 0.0003 mmol) prepared in Example 2, [2-(2,4,6-triisopropyl-3-(4-methoxyphenyl)phenyl)-6-(2,4,6-triisopropylphenyl)phenyl]-dicyclohexylphosphine (0.23 mg, 0.0003 mmol) prepared in Example 1, 0.13 mL of dodecane (as an internal standard for GC analysis), and 1 mL of xylene were added to another pressure tube. The reaction solution in the Schlenk flask was transferred to the pressure tube at room temperature, sealed, and heated under reflux in an oil bath at 110°C for 6 h. The reaction solution was filtered through silica gel and celite, and the filtrate was concentrated under reduced pressure. The residue was separated and purified by silica gel column chromatography (petroleum ether:ethyl acetate=10:1) to obtain 0.573 g of a white solid, namely 1,3,5-tris(9-carbazolyl)benzene, with a yield of 99.88%.

[0074] Example 7 Preparation of 1,3,5-tris(9-carbazolyl)benzene

[0075] Under an inert atmosphere, a stirrer was placed in a dry 50 mL Schlenk flask, and carbazole (0.507 g, 3.0 mmol) and xylene (3 mL) were added. The flask was cooled to 5°C, and methylmagnesium chloride (3.0 M in THF, 3.5 mmol, 1.15 mL) was added dropwise via syringe (approximately 1.5 min). After addition, the flask was stirred for 15 min and transferred to a glove box for later use.

[0076] In a glove box, 1,3,5-trichlorobenzene (0.181 g, 1.0 mmol), {[2-(2,4,6-triisopropyl-3-(4-methoxyphenyl)phenyl)-6-(2,4,6-triisopropylphenyl)phenyl]-dicyclohexylphosphine}(allyl-η3)trifluoromethanesulfonate palladium(II) (0.33 mg, 0.0003 mmol) prepared in Example 2, [2-(2,4,6-triisopropyl-3-(4-methoxyphenyl)phenyl)-6-(2,4,6-triisopropylphenyl)phenyl]-dicyclohexylphosphine (0.23 mg, 0.0003 mmol) prepared in Example 1, 0.13 mL of dodecane (as an internal standard for GC analysis), and 1 mL of dioxane were added to another pressure tube. The reaction solution in the Schlenk flask was transferred to the pressure tube at room temperature, sealed, and heated under reflux in an oil bath at 110°C for 6 h. The reaction solution was filtered through silica gel and celite, the filtrate was concentrated under reduced pressure, and the residue was separated and purified by silica gel column chromatography (petroleum ether:ethyl acetate=10:1) to obtain 0.573 g of a white solid, namely 1,3,5-trichlorobenzene, with a yield of 99.88%.

[0077] Example 8 Preparation of 1,3,5-tris(9-carbazolyl)benzene

[0078] Under an inert atmosphere, a stirrer was placed in a dry 50 mL Schlenk flask, and carbazole (0.552 g, 3.3 mmol) and xylene (3 mL) were added. The flask was cooled to 5°C, and isopropylmagnesium bromide (2.0 Min THF, 3.5 mmol, 1.75 mL) was added dropwise via syringe (approximately 1.5 min). After addition, the flask was stirred for 15 min and transferred to a glove box for later use.

[0079] In a glove box, 1,3,5-trichlorobenzene (0.181 g, 1.0 mmol), {[2-(2,4,6-triisopropyl-3-(4-methoxyphenyl)phenyl)-6-(2,4,6-triisopropylphenyl)phenyl]-dicyclohexylphosphine}(allyl-η3)trifluoromethanesulfonate palladium(II) (0.33 mg, 0.0003 mmol) prepared in Example 2, [2-(2,4,6-triisopropyl-3-(4-methoxyphenyl)phenyl)-6-(2,4,6-triisopropylphenyl)phenyl]-dicyclohexylphosphine (0.23 mg, 0.0003 mmol) prepared in Example 1, 0.13 mL of dodecane (as an internal standard for GC analysis), and 1 mL of xylene were added to another pressure tube. The reaction solution in the Schlenk flask was transferred to the pressure tube at room temperature, sealed, and heated under reflux in an oil bath at 110°C for 6 h. The reaction solution was filtered through silica gel and celite, and the filtrate was concentrated under reduced pressure. The residue was separated and purified by silica gel column chromatography (petroleum ether:ethyl acetate=10:1) to obtain 0.573 g of a white solid, namely 1,3,5-tris(9-carbazolyl)benzene, with a yield of 99.88%.

[0080] Example 9 Preparation of 1,3,5-tris(9-carbazolyl)benzene

[0081] Under an inert atmosphere, a stirrer was placed in a dry 50 mL Schlenk flask, and carbazole (0.552 g, 3.3 mmol) and tetrahydrofuran (3 mL) were added. The flask was cooled to 5°C, and methylmagnesium chloride (3.0 M in THF, 3.5 mmol, 1.15 mL) was added dropwise via syringe (approximately 1.5 min). After addition, the flask was stirred for 15 min and transferred to a glove box for later use.

[0082] In a glove box, 1,3,5-trichlorobenzene (0.181 g, 1.0 mmol), {[2-(2,4,6-triisopropyl-3-(4-methoxyphenyl)phenyl)-6-(2,4,6-triisopropylphenyl)phenyl]-dicyclohexylphosphine}(allyl-η3)trifluoromethanesulfonate palladium(II) (0.33 mg, 0.0003 mmol) prepared in Example 2, [2-(2,4,6-triisopropyl-3-(4-methoxyphenyl)phenyl)-6-(2,4,6-triisopropylphenyl)phenyl]-dicyclohexylphosphine (0.23 mg, 0.0003 mmol) prepared in Example 1, 0.13 mL of dodecane (as an internal standard for GC analysis), and 1 mL of xylene were added to another pressure tube. The reaction solution in the Schlenk flask was transferred to the pressure tube at room temperature, sealed, and heated under reflux in an oil bath at 110°C for 6 h. The reaction solution was filtered through silica gel and celite, and the filtrate was concentrated under reduced pressure. The residue was separated and purified by silica gel column chromatography (petroleum ether:ethyl acetate=10:1) to obtain 0.570 g of a white solid, namely 1,3,5-tris(9-carbazolyl)benzene, with a yield of 99.36%.

[0083] Example 10 Preparation of 1,3,5-tris(9-carbazolyl)benzene

[0084] Under an inert atmosphere, a stirrer was placed in a dry 50 mL Schlenk flask, and carbazole (0.552 g, 3.3 mmol) and dioxane (3 mL) were added. The flask was cooled to 5°C, and methylmagnesium chloride (3.0 M in THF, 3.5 mmol, 1.15 mL) was added dropwise via syringe (approximately 1.5 min). After addition, the mixture was stirred for 15 min and transferred to a glove box for later use.

[0085] In a glove box, 1,3,5-trichlorobenzene (0.181 g, 1.0 mmol), {[2-(2,4,6-triisopropyl-3-(4-methoxyphenyl)phenyl)-6-(2,4,6-triisopropylphenyl)phenyl]-dicyclohexylphosphine}(allyl-η3)trifluoromethanesulfonate palladium(II) (0.33 mg, 0.0003 mmol) prepared in Example 2, [2-(2,4,6-triisopropyl-3-(4-methoxyphenyl)phenyl)-6-(2,4,6-triisopropylphenyl)phenyl]-dicyclohexylphosphine (0.23 mg, 0.0003 mmol) prepared in Example 1, 0.13 mL of dodecane (as an internal standard for GC analysis), and 1 mL of xylene were added to another pressure tube. The reaction solution in the Schlenk flask was transferred to the pressure tube at room temperature, sealed, and heated under reflux in an oil bath at 110°C for 6 h. The reaction solution was filtered through silica gel and celite, and the filtrate was concentrated under reduced pressure. The residue was separated and purified by silica gel column chromatography (petroleum ether:ethyl acetate=10:1) to obtain 0.571 g of a white solid, namely 1,3,5-tris(9-carbazolyl)benzene, with a yield of 99.53%.

[0086] Different phosphine ligands [1] Preparation of 1,3,5-tris(9-carbazolyl)benzene via CN coupling reaction [2] The dosage and yield are shown in Table 1, wherein No. 11 represents Example 3.

[0087] Table 1

[0088] serial number Phosphine ligand Palladium complex (mol%) Time (h) Yield (%) 1 TXPhos [(TXPhos)(allyl)PdOTf](0.075) 6 93.62 2 TXPhos [(TXPhos)(allyl)PdOTf](0.1) 6 98.28 3 <![CDATA[ i PrTXPhos]]> <]]> 6 91.07 4 <![CDATA[ i PrTXPhos]]> <]]> 6 98.67 5 3-pentylTXPhos [(3-pentylTXPhos)(allyl)PdOTf](0.1) 6 95.49 6 TKPhos [(TKPhos)(allyl)PdOTf](0.1) 6 94.36 7 tBuXPhos [(tBuXPhos)(allyl)PdOTf](0.1) 6 45.01 8 BippyPhos [(BippyPhos)(allyl)PdOTf](0.1) 6 41.95 9 cBRIDP [(cBRIDP)(allyl)PdOTf](0.1) 6 33.46 10 <![CDATA[DmpPMe2]]> <]]> 6 0.86 11 TAIPhos [(TAlPhos)(allyl)PdOTf](0.03) 6 99.88

[0089] [1]

[0090] [2] Under an inert atmosphere (nitrogen), a stirring bar was added to a dry 50 mL Schlenk flask, and carbazole (0.552 g, 3.3 mmol) and xylene (3 mL) were added. The flask was cooled to 5°C, and methylmagnesium chloride (3.0 M in THF, 3.5 mmol, 1.15 mL) was added dropwise via a syringe (about 1.5 min). After addition, the mixture was stirred for 15 min and transferred to a glove box for later use.

[0091] In a glove box, add 1,3,5-trichlorobenzene (0.181 g, 1.0 mmol), the corresponding palladium complex, the phosphine ligand, 0.13 mL of dodecane (as an internal standard for GC analysis), and 1 mL of xylene to another pressure tube. Transfer the reaction mixture from the Schlenk flask to the pressure tube at room temperature, seal it, and heat under reflux in an oil bath at 110°C for 6 h. Filter the reaction mixture through silica gel and celite, concentrate the filtrate under reduced pressure, and purify the residue by silica gel column chromatography (petroleum ether:ethyl acetate = 10:1) to yield 1,3,5-tris(9-carbazolyl)benzene.

[0092] 1 H NMR (400MHz, CDCl3) δ: 8.19 (d, J=7.5Hz, 6H), 7.99 (s, 3H), 7.70 (d, J=8.2Hz, 6 H), 7.50 (ddd, J=8.3, 7.3, 1.2Hz, 6H), 7.39-7.32 (ddd, J=7.8, 6.8, 0.9Hz, 6H).

[0093] 13 C NMR (101MHz, CDCl3) δ: 140.82, 140.35, 126.41, 123.88, 123.57, 120.78, 120.63, 109.70.

[0094] As shown in Table 1, TAlPhos and its palladium complex catalyze the carbon-nitrogen coupling reaction of 1,3,5-trichlorobenzene with carbazole. Compared with existing commercially available catalysts and conventional tert-arylphosphine ligand catalysts of the same type, the palladium dosage is significantly reduced, and the dosage is only less than half of that of TXPhos. Moreover, the catalytic effect is better than that of TXPhos, and the yield can reach 99.88%.

[0095] The above are merely preferred embodiments of the present application, but the scope of protection of the present application is not limited thereto. Any changes or substitutions that can be easily conceived by a person skilled in the art within the technical scope disclosed in this application should be included in the scope of protection of the present application. Therefore, the scope of protection of the present application should be based on the scope of protection of the claims.

Claims

1. A phosphine ligand, characterized in that The chemical name is [2-(2,4,6-triisopropyl-3-(4-methoxyphenyl)phenyl)-6-(2,4,6-triisopropylphenyl)phenyl]-dicyclohexylphosphine, and its structural formula is as follows:

2. A method for preparing the phosphine ligand according to claim 1, characterized in that: Sodium phenolate, tetrahydrofuran and 4-methoxychlorobenzene are added to [2,6-bis(2,4,6-triisopropyl-phenyl)phenyl-dicyclohexylphosphine](allyl-η3)palladium(II) chloride, and the mixture is heated for reaction. After the reaction is complete, the mixture is passed through celite and then subjected to column chromatography to obtain the phosphine ligand.

3. A palladium complex of the phosphine ligand according to claim 1, characterized in that The chemical name is {[2-(2,4,6-triisopropyl-3-(4-methoxyphenyl)phenyl)-6-(2,4,6-triisopropylphenyl)phenyl]-dicyclohexylphosphine}(allyl-η3)trifluoromethanesulfonate palladium(II), and its structural formula is as follows:

4. A method for preparing the palladium complex of the phosphine ligand according to claim 3, characterized in that: Allyl dimer palladium and silver trifluoromethanesulfonate are added to a dry pressure-resistant tube, tetrahydrofuran is added, and the mixture is stirred evenly at room temperature. Then, [2-(2,4,6-triisopropyl-3-(4-methoxyphenyl)phenyl)-6-(2,4,6-triisopropylphenyl)phenyl]-dicyclohexylphosphine is added, and the mixture is reacted under stirring. After the reaction is complete, the mixture is passed through diatomaceous earth and dried in a spin-drying process to obtain a palladium complex of the phosphine ligand.

5. The method for preparing the palladium complex of the phosphine ligand according to claim 4, wherein The molar ratio of allyl dimer palladium, silver trifluoromethanesulfonate and [2-(2,4,6-triisopropyl-3-(4-methoxyphenyl)phenyl)-6-(2,4,6-triisopropylphenyl)phenyl]-dicyclohexylphosphine is 1:2:

2.

6. A method for preparing 1,3,5-tris(9-carbazolyl)benzene, characterized in that: 1,3,5-trichlorobenzene and carbazole are used as raw materials, an organic magnesium reagent, the phosphine ligand according to claim 1 and a palladium complex of the phosphine ligand according to claim 3 are added, and the 1,3,5-tris(9-carbazolyl)benzene is prepared through a carbon-nitrogen coupling reaction.

7. The method for preparing 1,3,5-tris(9-carbazolyl)benzene according to claim 6, wherein: The following steps are involved: Under an inert atmosphere, a stirring bar is added to a dry Schlenk flask, carbazole and xylene are added, and the mixture is cooled to 5° C., an organomagnesium reagent is added dropwise, and the mixture is stirred for reaction after the addition is completed. After the reaction is completed, the mixture is transferred to a glove box; in the glove box, 1,3,5-trichlorobenzene, the palladium complex of the phosphine ligand according to claim 3, the phosphine ligand according to claim 1, and an organic solvent are added to another pressure-resistant tube, and the reaction solution in the Schlenk flask is transferred to the pressure-resistant tube at room temperature, and the mixture is heated under reflux in an oil bath for reaction. After the reaction is completed, the mixture is separated and purified to obtain the 1,3,5-tris(9-carbazolyl)benzene.

8. The method for preparing 1,3,5-tris(9-carbazolyl)benzene according to claim 7, wherein: The molar ratio of 1,3,5-trichlorobenzene to the palladium complex of the phosphine ligand according to claim 3 is 1:0.0003.

9. The method for preparing 1,3,5-tris(9-carbazolyl)benzene according to claim 7, wherein: The molar ratio of the phosphine ligand according to claim 1 to the palladium complex of the phosphine ligand according to claim 3 is (1 to 3):

1.

10. The method for preparing 1,3,5-tris(9-carbazolyl)benzene according to claim 7, wherein: The molar ratio of 1,3,5-trichlorobenzene to carbazole is 1:(3.0-3.3).

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