Preparation method of fluorine-containing carbazole phosphonic acid compound

Abstract

The invention discloses a preparation method of a fluorine-containing carbazole phosphonic acid compound, which solves the technical problems of harsh reaction conditions, high raw material price and low yield in the existing preparation process, 4-trifluoromethoxyaniline and 4-trifluoromethoxyiodobenzene are used as initial raw materials, and Ullmann reaction is performed under a solvent-free condition to obtain 4, 4 '-difluorocarbazole phosphonic acid. The preparation method comprises the following steps: taking 3, 4 '-bis (trifluoromethoxy) diphenylamine as a raw material, carrying out palladium acetate catalytic oxidation cyclization to obtain 3, 6-bis (trifluoromethoxy) carbazole, reacting the 3, 6-bis (trifluoromethoxy) carbazole with 2-bromoethyl dimethyl phosphonate to obtain N-(2-ethyl dimethyl phosphonate) 3, 6-bis (trifluoromethoxy) carbazole, and finally hydrolyzing to obtain the N-(2-ethyl phosphonate) 3, 6-bis (trifluoromethoxy) carbazole. The reaction process is simpler to operate, the yield is guaranteed, and the method is suitable for large-scale production. In the preparation method disclosed by the invention, a solvent is not required to be used in multiple steps, the reaction is performed under a solvent-free condition, and the preparation method is high in safety and environment-friendly.

Description

Technical Field

[0001] The invention relates to the technical field of organic synthesis, and in particular to a method for preparing a fluorine-containing carbazole phosphonic acid compound. Background Art

[0002] Human demand for energy is constantly increasing, environmental pollution and greenhouse effect are becoming increasingly prominent, these problems have prompted scientists to develop clean and renewable energy. The development and utilization of solar energy has become a research hotspot in the field of new energy. There are many forms of solar energy utilization, and photoelectric conversion is the main form of effective utilization of solar cells. Solar cells are considered to be one of the most effective low-cost renewable clean energy sources, thereby achieving the goal of carbon neutrality.

[0003] In 1883, scientist Charles Fritts first produced solar cells that can directly convert solar energy into electrical energy. In the following century, scientists developed traditional photoelectric conversion materials such as silicon-based solar cells and compound solar cells. In 2009, Japanese scientist Miyasaka introduced the perovskite material MAPBI3 into solar cell devices. After nearly ten years of development, the efficiency of the cell has increased from the initial 3.8% to the current 25.5%, making perovskite solar cells with good photoelectric properties, high light absorption rate, simple preparation and large-area flexible preparation.

[0004] In recent years, SAMS self-assembled monolayer materials (carbazole derivatives with phosphonic acid anchoring groups, such as MEO-2PACZ, 2PACZ, ME-4PACZ, Br-2PACZ, TPA, and EADR04) have been applied to solar cells due to their simple preparation, small parasitic absorption, low material consumption, and conformal coverage with the substrate. The key to their synthesis lies in the construction of carbazole, a synthetic building block, and there are currently two main synthesis routes.

[0005] 1. Synthesis (2020; 52(06): 917-927) reported the synthesis of 3,6-ditrifluoromethoxycarbazole, the reaction process is as follows:

[0006]

[0007] The method uses 4-trifluoromethoxy-2-bromoaniline to undergo acetylation and Ullmann coupling reaction, and then react at 200° C. The raw materials used in the method are not easy to obtain and the reaction conditions are harsh.

[0008] 2. J.Med.Chem. (2023, 66, 1972-1989) reported another synthetic route, the reaction process is as follows:

[0009]

[0010] The method uses 4-trifluoromethoxyaniline and 4-trifluoromethoxybromobenzene to couple with palladium acetate as a catalyst, and then undergoes oxidative cyclization to obtain 3,6-ditrifluoromethoxycarbazole. The catalyst and ligand used in the first step of the method are expensive and have a low yield.

[0011] It can be seen that the existing technology has conducted many studies and improvements on the method of synthesizing 3,6-ditrifluoromethoxycarbazole, but there is still a demand and room for improvement in terms of improving safety and environmental protection, simplifying the process, reducing costs, and increasing the yield. Summary of the invention

[0012] The object of the present invention is to provide a method for preparing a fluorine-containing carbazole phosphonic acid compound, so as to solve the technical problems of harsh reaction conditions, high raw material prices and low yield in the existing preparation process.

[0013] To achieve the above object, the present invention provides the following technical solutions:

[0014] The present invention provides a method for preparing a fluorine-containing carbazole phosphonic acid compound, comprising the following steps:

[0015] (1) Ullmann coupling reaction: 4-trifluoromethoxyaniline, 4-trifluoromethoxyiodobenzene and cuprous iodide are added to a reaction vessel I, and the mixture is stirred. The reaction vessel is heated in the absence of a solvent. After the reaction is completed, the reaction vessel is cooled to room temperature and separated by column chromatography to obtain 4,4'-ditrifluoromethoxydiphenylamine.

[0016] (2) Cyclization reaction: Add 4,4'-ditrifluoromethoxydiphenylamine obtained in step (1) to reaction vessel II, add palladium acetate, heat for cyclization reaction, add sodium hydroxide to adjust the pH value after the reaction, then use ethyl acetate for extraction, remove the ethyl acetate by rotation, and separate by column chromatography to obtain 3,6-ditrifluoromethoxycarbazole;

[0017] (3) Alkylation reaction: Add 3,6-ditrifluoromethoxycarbazole obtained in step (2) to reaction vessel III, add sodium hydride, react for several hours, add dimethyl 2-bromoethylphosphonate, react at room temperature, add ice water and stir, extract with ethyl acetate, remove ethyl acetate by rotation, separate by column chromatography, and obtain N-(dimethyl 2-ethylphosphonate) 3,6-ditrifluoromethoxycarbazole;

[0018] (4) Hydrolysis reaction: Add N-(2-ethylphosphonic acid dimethyl ester) 3,6-ditrifluoromethoxycarbazole, dichloromethane and trimethylsilyl bromide obtained in step (3) into reaction vessel IV and react at room temperature. After the reaction, remove dichloromethane and add ice water to stir to obtain a solid, which is recrystallized from methanol to obtain N-(2-ethylphosphonic acid) 3,6-ditrifluoromethoxycarbazole.

[0019] Its synthetic route is as follows:

[0020]

[0021] Preferably, in step (1), the molar ratio of 4-trifluoromethoxyaniline to 4-trifluoromethoxyiodobenzene is 1.2:1 to 2:1.

[0022] More preferably, the molar ratio of the 4-trifluoromethoxyiodobenzene to the 4-trifluoromethoxyaniline is 1:1.5.

[0023] Preferably, in step (1), the reaction temperature of the coupling reaction is 120-140° C., and the reaction time is 8 to 14 h.

[0024] More preferably, the reaction temperature of the coupling reaction is 130° C. and the reaction time is 10 h.

[0025] Preferably, in step (1), a catalyst is also added to the coupling reaction, the catalyst used is cuprous iodide, and the co-catalyst is bipyridine.

[0026] Preferably, in step (2), a solvent is also added to the cyclization reaction, the solvent used is pivalic acid, and the molar ratio of pivalic acid to reactant is 1:2 to 4:1; more preferably, the molar ratio of pivalic acid to reactant is 1:2.

[0027] Preferably, in step (2), the reaction temperature of the cyclization reaction is 100-130° C., and the reaction time is 4-10 h; more preferably, the reaction temperature is 110° C., and the reaction time is 6 h.

[0028] Preferably, in step (3), the molar ratio of 3,6-ditrifluoromethoxycarbazole to 2-bromoethyl dimethyl phosphate is 1:1 to 1:1.2.

[0029] More preferably, the molar ratio of 3,6-ditrifluoromethoxycarbazole to 2-bromoethyl dimethyl phosphate in the alkylation reaction is 1:1.2.

[0030] Preferably, in step (3), a solvent is added to the alkylation reaction, and the solvent used is N,N-dimethylformamide.

[0031] Preferably, in step (3), the reaction temperature of the alkylation reaction is 20-50° C., and the reaction time is 10-14 h; more preferably, the reaction temperature is 20° C., and the reaction time is 12 h.

[0032] Preferably, in step (4), the molar ratio of N-(dimethyl 2-ethylphosphonate) 3,6-ditrifluoromethoxycarbazole to trimethylsilyl bromide is 1:1.5 to 1:2; more preferably, the molar ratio is 1:1.5.

[0033] Based on the above technical solution, the embodiments of the present invention can at least produce the following technical effects:

[0034] Compared with the prior art, the present invention provides a novel preparation method of N-(2-ethylphosphonic acid) 3,6-ditrifluoromethoxycarbazole, using 4-trifluoromethoxyaniline and 4-trifluoromethoxyiodobenzene as initial raw materials, performing coupling reaction under solvent-free conditions to obtain 4,4'-ditrifluoromethoxydiphenylamine, performing cyclization reaction to obtain 3,6-ditrifluoromethoxycarbazole, performing alkylation reaction to obtain N-(2-ethylphosphonic acid dimethyl ester) 3,6-ditrifluoromethoxycarbazole, and finally hydrolyzing N-(2-ethylphosphonic acid) 3,6-ditrifluoromethoxycarbazole. The present invention has cheap reaction raw materials, multi-step solvent-free reaction, guaranteed yield, and provides a new path for the production and preparation of N-(2-ethylphosphonic acid) 3,6-ditrifluoromethoxycarbazole. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on the structures shown in these drawings without paying creative work.

[0036] Figure 1 This is the H NMR spectrum of 4,4'-bis(trifluoromethoxy)diphenylamine prepared in Example 1 of the present invention;

[0037] Figure 2 This is the carbon NMR spectrum of 4,4'-ditrifluoromethoxydiphenylamine prepared in Example 1 of the present invention;

[0038] Figure 3 is the H NMR spectrum of 3,6-ditrifluoromethoxycarbazole prepared in Example 1 of the present invention;

[0039] Figure 4 is the NMR carbon spectrum of 3,6-ditrifluoromethoxycarbazole prepared in Example 1 of the present invention;

[0040] Figure 5 is the H NMR spectrum of N-(2-ethylphosphonic acid dimethyl ester) 3,6-ditrifluoromethoxycarbazole prepared in Example 1 of the present invention;

[0041] Figure 6is the NMR carbon spectrum of N-(2-ethylphosphonic acid dimethyl ester) 3,6-ditrifluoromethoxycarbazole prepared in Example 1 of the present invention;

[0042] Figure 7 This is the H NMR spectrum of N-(2-ethylphosphonic acid) 3,6-ditrifluoromethoxycarbazole prepared in Example 1 of the present invention. DETAILED DESCRIPTION

[0043] The technical solutions in the embodiments of the present invention will be described clearly and completely below. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments in the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention. In addition, the technical solutions between the various embodiments can be combined with each other, but they must be based on the ability of ordinary technicians in this field to implement them. When the combination of technical solutions is contradictory or cannot be implemented, it should be considered that such a combination of technical solutions does not exist and is not within the scope of protection required by the present invention.

[0044] The objective of the present invention is achieved through the following technical solutions:

[0045] Example 1

[0046] (1) 4-Trifluoromethoxyiodobenzene (2.87 g, 50 mmol), 4-trifluoromethoxyaniline (2.12 g, 12 mmol), potassium carbonate (2.07 g, 15 mmol), cuprous iodide (0.189 g, 1 mmol), and bipyridine (0.156 g, 1 mmol) were added to a 500 ml single-necked flask, heated to 120°C, reacted for 10 h, cooled to room temperature, added with water, extracted with ethyl acetate, separated, added with 18% aqueous hydrochloric acid solution to ethyl acetate, stirred for 0.5 h, separated, added with 18% aqueous hydrochloric acid solution again, stirred for 0.5 h, separated, washed with water, dried over anhydrous magnesium sulfate, filtered, and the filtrate was taken and the ethyl acetate was removed by vortexing to obtain 1.75 g of 4,4'-ditrifluoromethoxydiphenylamine with a yield of 52%.

[0047] 1 H NMR (400 MHz, CDCl 3 )δppm:7.10-7.13(d,J=11.0Hz,2H),6.98-7.01(d,J=11.25Hz,2H);5.69(s,1H),

[0048] 13 CNMR (100MHz, CDCl 3 )δppm:143.2,141.5,122.5,118.6.

[0049] (2) 4,4'-ditrifluoromethoxydiphenylamine (3.37 g, 10 mmol), palladium acetate (0.22 g, 1 mmol), and pivalic acid (20.4 g, 200 mmol) were added to a single-necked flask, heated to 110°C under oxygen, and reacted for 6 h. Sodium hydroxide aqueous solution was added, and then ethyl acetate was used for extraction and separation. The upper ethyl acetate liquid was washed with water, dried over anhydrous magnesium sulfate, filtered, and ethyl acetate was removed. 3,6-ditrifluoromethoxycarbazole (1.07 g) was obtained by column chromatography separation with a yield of 32%.

[0050] 1 H NMR (400 MHz, CDCl 3 )δppm:8.29(S,1H),7.89(s,2H),7.33-7.38(m,4H),

[0051] 13 CNMR (100MHz, CDCl 3 )δppm:142.6,138.5,123.2,120.4,113.3,111.5.

[0052] (3) 3,6-ditrifluoromethoxycarbazole (3.35 g, 10 mmol), DMF (20 ml), and sodium hydride (0.6 g, 15 mmol) were added to a single-necked flask. After stirring for 6 h, diethyl 2-bromoethylphosphonate (2.94 g, 12 mmol) was added. After continuing the reaction for 8 h, the product was directly separated by column chromatography to obtain N-(2-ethylphosphonic acid dimethyl ester) 3,6-ditrifluoromethoxycarbazole (4.09 g) with a yield of 82%.

[0053] 1 H NMR (400 MHz, CDCl 3 )δppm:7.90(S,2,H),7.39-7.45(m,4H),4.58-4.65(m,2H),4.01-4.08(m,4H),2,21-2.30(m,2H),1.23(t,J=7.08Hz,6H)

[0054] 13 CNMR (100MHz, CDCl 3 )δppm:142.6,138.7,122.8,120.4,113.6,109.6,62.0,61.9,37.4,26.0,24.6,16.2.

[0055] (4) Add N-(2-ethylphosphonic acid dimethyl ester) 3,6-ditrifluoromethoxycarbazole (4.99 g, 10 mmol) and dichloromethane (50 ml) into a single-necked flask, slowly add trimethylsilyl bromide (4.59 g, 30 mmol), and then stir at room temperature for 8 h. Then remove the dichloromethane, add n-hexane (50 ml × 2), and then remove the n-hexane by decantation. Add DMF (10 ml), and then add it dropwise into ice water to obtain the product N-(2-ethylphosphonic acid) 3,6-ditrifluoromethoxycarbazole (3.23 g) with a yield of 73%.

[0056] 1 H NMR (400 MHz, CDCl 3 )δppm:8.38(s,2H),7.68(d,J=8.9Hz,2H),7.51(d,J=8.85Hz,2H),6.99(d, J=8.4Hz,1H),6.60(d,J=8.85Hz,1H),4.57-4.62(m,2H),2.03-2.10(m,2H).

[0057] Example 2

[0058] (1) 4-Trifluoromethoxyiodobenzene (2.87 g, 50 mmol), 4-trifluoromethoxyaniline (2.12 g, 12 mmol), potassium carbonate (2.07 g, 15 mmol), cuprous iodide (0.189 g, 1 mmol), and bipyridine (0.156 g, 1 mmol) were added to a 500 ml single-necked flask, heated to 130°C, reacted for 10 h, cooled to room temperature, added with water, extracted with ethyl acetate, separated, added with 18% aqueous hydrochloric acid solution to ethyl acetate, stirred for 0.5 h, separated, added with 18% aqueous hydrochloric acid solution again, stirred for 0.5 h, separated, washed with water, dried over anhydrous magnesium sulfate, filtered, and the filtrate was taken and the ethyl acetate was removed by vortexing to obtain 4,4'-ditrifluoromethoxydiphenylamine with a yield of 63%.

[0059] (2) 4,4'-ditrifluoromethoxydiphenylamine (3.37 g, 10 mmol), palladium acetate (0.22 g, 1 mmol), and pivalic acid (20.4 g, 200 mmol) were added to a single-necked flask, heated to 120°C under air, and reacted for 6 h. Sodium hydroxide aqueous solution was added, and then ethyl acetate was used for extraction and separation. The upper ethyl acetate liquid was washed with water, dried over anhydrous magnesium sulfate, filtered, and ethyl acetate was removed. 3,6-ditrifluoromethoxycarbazole was obtained by column chromatography with a yield of 32%.

[0060] (3) 3,6-ditrifluoromethoxycarbazole (3.35 g, 10 mmol), DMF (20 ml), and sodium hydride (0.6 g, 15 mmol) were added to a single-necked flask. After stirring for 6 h, diethyl 2-bromoethylphosphonate (2.94 g, 12 mmol) was added. After continuing the reaction for 8 h, the obtained product was directly separated by column chromatography to obtain N-(2-ethylphosphonic acid dimethyl ester) 3,6-ditrifluoromethoxycarbazole with a yield of 78%.

[0061] (4) Add N-(2-ethylphosphonic acid dimethyl ester) 3,6-ditrifluoromethoxycarbazole (4.99 g, 10 mmol) and dichloromethane (50 ml) into a single-necked flask, slowly add trimethylsilyl bromide (4.59 g, 30 mmol), and then stir at room temperature for 8 h. Then, remove the dichloromethane, add n-hexane, and then pour off the n-hexane. Add DMF, and then add it dropwise into ice water to obtain the product N-(2-ethylphosphonic acid) 3,6-ditrifluoromethoxycarbazole with a yield of 74%.

[0062] Example 3

[0063] (1) 4-Trifluoromethoxyiodobenzene (2.87 g, 50 mmol), 4-trifluoromethoxyaniline (2.12 g, 12 mmol), potassium carbonate (2.07 g, 15 mmol), cuprous iodide (0.189 g, 1 mmol), and bipyridine (0.156 g, 1 mmol) were added to a 500 ml single-necked flask, heated to 140°C, reacted for 10 h, cooled to room temperature, added with water, extracted with ethyl acetate, separated, added with 18% aqueous hydrochloric acid solution to ethyl acetate, stirred for 0.5 h, separated, added with 18% aqueous hydrochloric acid solution again, stirred for 0.5 h, separated, washed with water, dried over anhydrous magnesium sulfate, filtered, and the filtrate was taken and the ethyl acetate was removed by vortexing to obtain 4,4'-ditrifluoromethoxydiphenylamine with a yield of 52%.

[0064] (2) 4,4'-ditrifluoromethoxydiphenylamine (3.37 g, 10 mmol), palladium acetate (0.22 g, 1 mmol), and pivalic acid (20.4 g, 200 mmol) were added to a single-necked flask, heated to 130°C under oxygen, and reacted for 6 h. Sodium hydroxide aqueous solution was added, and then ethyl acetate was used for extraction and separation. The upper ethyl acetate liquid was washed with water, dried over anhydrous magnesium sulfate, filtered, and ethyl acetate was removed. 3,6-ditrifluoromethoxycarbazole was obtained by column chromatography with a yield of 15%.

[0065] (3) 3,6-ditrifluoromethoxycarbazole (3.35 g, 10 mmol), DMF (20 ml), and sodium hydride (0.6 g, 15 mmol) were added to a single-necked flask. After stirring for 6 h, diethyl 2-bromoethylphosphonate (2.94 g, 12 mmol) was added. After continuing the reaction for 6 h, the obtained product was directly separated by column chromatography to obtain N-(2-ethylphosphonic acid dimethyl ester) 3,6-ditrifluoromethoxycarbazole with a yield of 81%.

[0066] (4) Add N-(2-ethylphosphonic acid dimethyl ester) 3,6-ditrifluoromethoxycarbazole (4.99 g, 10 mmol) and dichloromethane (50 ml) into a single-necked flask, slowly add trimethylsilyl bromide (4.59 g, 30 mmol), and then stir at room temperature for 8 h. Then, remove the dichloromethane, add n-hexane, and then remove the n-hexane by decantation. Add DMF, and then add it dropwise into ice water to obtain the product N-(2-ethylphosphonic acid) 3,6-ditrifluoromethoxycarbazole with a yield of 70%.

[0067] Example 4

[0068] The technical features in this embodiment are basically the same as those described in Example 3, and the same technical features and technical solutions are not repeated here. The difference is that in step (1), 4-trifluoromethoxy iodobenzene and 4-trifluoromethoxy aniline are added to a single-necked flask in a molar ratio of 1:1, and the amounts of the other raw materials remain unchanged. The mixture is heated to 140° C., and finally 4,4'-ditrifluoromethoxy diphenylamine is obtained with a yield of 35%.

[0069] Example 5

[0070] The technical features in this embodiment are basically the same as those described in Example 1, and the same technical features and technical solutions are not repeated here. The difference is that the acid added in step (2) is acetic acid, and the final yield of 3,6-ditrifluoromethoxycarbazole is 15%.

[0071] Example 6

[0072] The technical features in this embodiment are basically the same as those described in Example 1, and the same technical features and technical solutions are not repeated here. The difference is that the acid added in step (2) is acetic acid, and the mixture is heated to 120° C. in air and reacted for 12 hours to finally obtain 3,6-ditrifluoromethoxycarbazole with a yield of 10%.

[0073] The above shows and describes the basic principles and main features of the present invention and the advantages of the present invention. It should be understood by those skilled in the art that the present invention is not limited to the above embodiments, and the above embodiments and descriptions are only for explaining the principles of the present invention. Without departing from the spirit and scope of the present invention, the present invention may have various changes and improvements, and these changes and improvements fall within the scope of the present invention to be protected. The scope of the present invention to be protected is defined by the attached claims and their equivalents.

Claims

1. A method for preparing a fluorine-containing carbazole phosphonic acid compound, characterized in that: The steps include: (1) Coupling reaction: 4-trifluoromethoxyaniline, 4-trifluoromethoxyiodobenzene and cuprous iodide are added to a reaction vessel I, and the mixture is stirred. The reaction vessel is heated in the absence of a solvent. After the reaction is completed, the reaction vessel is cooled to room temperature and separated by column chromatography to obtain 4,4'-ditrifluoromethoxydiphenylamine; (2) Cyclization reaction: Add 4,4'-ditrifluoromethoxydiphenylamine obtained in step (1) to reaction vessel II, add palladium acetate, heat for cyclization reaction, add sodium hydroxide to adjust the pH value after the reaction, then use ethyl acetate for extraction, remove the ethyl acetate by rotation, and separate by column chromatography to obtain 3,6-ditrifluoromethoxycarbazole; (3) Alkylation reaction: Add 3,6-ditrifluoromethoxycarbazole obtained in step (2) to reaction vessel III, add sodium hydride, react for several hours, add dimethyl 2-bromoethylphosphonate, react at room temperature, add ice water and stir, extract with ethyl acetate, remove ethyl acetate by rotation, separate by column chromatography, and obtain N-(dimethyl 2-ethylphosphonate) 3,6-ditrifluoromethoxycarbazole; (4) Hydrolysis reaction: Add N-(2-ethylphosphonic acid dimethyl ester) 3,6-ditrifluoromethoxycarbazole, dichloromethane and trimethylsilyl bromide obtained in step (3) into reaction vessel IV and react at room temperature. After the reaction, remove dichloromethane and add ice water to stir to obtain a solid, which is recrystallized from methanol to obtain N-(2-ethylphosphonic acid) 3,6-ditrifluoromethoxycarbazole.

2. The method for preparing the fluorine-containing carbazole phosphonic acid compound according to claim 1, characterized in that: In step (1), the molar ratio of 4-trifluoromethoxyaniline to 4-trifluoromethoxyiodobenzene is 1.2:1 to 2:

1.

3. The method for preparing the fluorine-containing carbazole phosphonic acid compound according to claim 1, characterized in that: In step (1), the reaction temperature of the coupling reaction is 120-140° C., and the reaction time is 8-14 h.

4. The method for preparing the fluorine-containing carbazole phosphonic acid compound according to claim 1, characterized in that: In step (1), a catalyst and a co-catalyst are added to the coupling reaction. The catalyst used is cuprous iodide and the co-catalyst is bipyridine.

5. The method for preparing the fluorine-containing carbazole phosphonic acid compound according to claim 1, characterized in that: In step (2), a solvent is also added to the cyclization reaction, and the solvent used is pivalic acid, and the molar ratio of pivalic acid to reactant is 1:2 to 4:

1.

6. The method for preparing the fluorine-containing carbazole phosphonic acid compound according to claim 1, characterized in that: In step (2), the reaction temperature of the cyclization reaction is 100-130° C., and the reaction time is 4-10 h.

7. The method for preparing the fluorine-containing carbazole phosphonic acid compound according to claim 1, characterized in that: In step (3), the molar ratio of 3,6-ditrifluoromethoxycarbazole to 2-bromoethyl dimethyl phosphate is 1:1 to 1:1.

2.

8. The method for preparing the fluorine-containing carbazole phosphonic acid compound according to claim 1, characterized in that: In step (3), a solvent is also added to the alkylation reaction, and the solvent used is N,N-dimethylformamide.

9. The method for preparing the fluorine-containing carbazole phosphonic acid compound according to claim 1, characterized in that: In step (3), the reaction temperature of the alkylation reaction is 20 to 50° C., and the reaction time is 10 to 14 hours.

10. The method for preparing the fluorine-containing carbazole phosphonic acid compound according to claim 1, characterized in that: In step (4), the molar ratio of N-(dimethyl 2-ethylphosphonate) 3,6-ditrifluoromethoxycarbazole to trimethylsilyl bromide is 1:1.5 to 1:2.

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