CN107235891B - A kind of preparation method of 4-bromocarbazole - Google Patents

Abstract

The invention discloses a preparation method of 4-bromocarbazole, belonging to the field of organic chemical synthesis. The method comprises the following steps: (1) carrying out condensation reaction on 1, 3-cyclohexanedione and aniline to prepare 3-aniline-cyclohexene-2-ketone; (2) the 3-aniline-cyclohexene-2-ketone is subjected to cyclization reaction to prepare 1,2,3, 9-tetrahydrocarbazole-4-ketone; (3) reducing the 1,2,3, 9-tetrahydrocarbazole-4-ketone to prepare 4-hydroxy-1, 2,3, 9-tetrahydrocarbazole; (4) preparing 4-bromo-1, 2,3, 9-tetrahydrocarbazole through bromination reaction of the 4-hydroxy-1, 2,3, 9-tetrahydrocarbazole; (5) the 4-bromo-1, 2,3, 9-tetrahydrocarbazole is subjected to dehydrogenation reaction to prepare the 4-bromocarbazole. The method has the advantages of cheap and easily-obtained reaction raw materials, simple reaction operation, less side reaction and high yield; the prepared 4-bromocarbazole has high purity, can be used in the fields of OLED photoelectric materials, medicines and the like, and is an important carbazole intermediate.

Description

A kind of preparation method of 4-bromocarbazole

technical field

The invention relates to the field of organic chemical synthesis, in particular to a preparation method of 4-bromocarbazole.

Background technique

Carbazole derivatives are a large class of intermediates with a wide range of uses. It has good optoelectronic properties, and other derivatives prepared from carbazole are widely used in OLED optoelectronic materials, medicine, dyes and pesticides and other fields.

Halogenates with different substituent positions on carbazole were prepared by different methods. At present, carbazole derivatives such as 3-bromocarbazole, 2-bromocarbazole, and 1-bromocarbazole have been widely reported. Its derivatives are widely used in OLED optoelectronic materials, medicine, dyes and pesticides and other fields. Most of its synthetic methods are obtained through direct bromination, Cadogan ring closure or Fischer indole synthesis.

There are few reports on the preparation methods of 4-bromocarbazole and its derivatives, most of which are Suzuki coupling through o-nitrophenylboronic acid and o-bromoiodobenzene, and then under the high temperature action of triethyl phosphite or triphenylphosphine. obtained by cyclization. The raw materials are expensive, among which triethyl phosphite has a strong odor, and a large amount of by-products such as triphenylphosphine will be produced during the cyclization preparation with triphenylphosphine, and because the product is carried out at high temperature, the color of the final product is relatively low. Deep, purification is more difficult.

In addition, Chinese application CN 103936656A discloses a method for synthesizing 4-bromocarbazole. The method uses bromophenylboronic acid as a raw material, and undergoes Suzuki reaction to obtain 2-bromo-2'-nitrobiphenyl; and then 2-bromo- 4-Bromocarbazole was synthesized from 2'-nitrobiphenyl using triphenyl phosphite as reducing agent. It also has the problems of producing a large amount of triphenylphosphine by-products and difficulty in purification during the ring closure process. At present, the production process of 4-bromocarbazole needs to be improved in order to meet the increasing product demand.

SUMMARY OF THE INVENTION

In order to solve the above problems, the present invention provides a new method for preparing 4-bromocarbazole with mild reaction conditions, simple post-processing and purification, high yield and low cost.

The preparation method of 4-bromocarbazole of the present invention, its synthetic route is as follows:

The method includes the following steps:

(1) 1,3-cyclohexanedione and aniline carry out condensation reaction to obtain 3-aniline-cyclohexen-2-one;

(2) 1,2,3,9-tetrahydrocarbazol-4-one is prepared by cyclization of the 3-aniline-cyclohexen-2-one;

(3) The 1,2,3,9-tetrahydrocarbazol-4-one is reduced to obtain 4-hydroxy-1,2,3,9-tetrahydrocarbazole;

(4) The 4-hydroxy-1,2,3,9-tetrahydrocarbazole is brominated to obtain 4-bromo-1,2,3,9-tetrahydrocarbazole;

(5) The 4-bromo-1,2,3,9-tetrahydrocarbazole is subjected to dehydrogenation to obtain the 4-bromocarbazole.

In the preparation method of the present invention, the reaction conditions of each step (such as reaction temperature, selection of solvent, separation of products, etc.) can adopt conventional available means in the field, and satisfy the requirement that the above reaction scheme can be obtained to obtain 4-bromocarbazole, namely Can.

Only in order to further improve the quality of the preparation route and better realize the purpose of the invention, the present invention has carried out the following optimization to the specific conditions of the preparation method:

In the method of the present invention, in step (1), the ideal molar feeding ratio of the 1,3-cyclohexanedione and the aniline is 1:0.9-1.05, preferably 1:1. Under this charging ratio, the two raw materials can be fully reacted, with the advantages of high conversion rate and no other excess impurities.

In the method of the present invention, the catalyst used in the condensation reaction in step (1) is a metal oxide; preferably, the metal oxide is one of alumina, magnesia or calcium oxide; more preferably, alumina.

Wherein, the ideal molar dosage of the catalyst is aniline:catalyst=1:0.1-0.2.

In the method of the present invention, the condensation reaction in step (1) is carried out in a solvent; the solvent is preferably toluene, and the ideal amount of the solvent is aniline:solvent=1g:5-15mL.

In the method of the present invention, the reaction temperature of the condensation reaction in step (1) is 100-120°C; preferably 108-110°C.

Preferably, step (1) also includes separation of intermediate products, specifically: washing the organic layer obtained by the condensation reaction to neutrality, drying and concentrating to obtain the 3-aniline-cyclohexene-2 -ketone; this separation step can remove mechanical impurities and catalysts, which is conducive to the full progress of the next reaction.

In the method of the present invention, the cyclization reaction described in step (2) is carried out in the presence of a palladium catalyst and an inorganic base;

Wherein, the palladium catalyst is one of palladium acetate, 1,1'-bisdiphenylphosphinoferrocene palladium dichloride or tris(dibenzylideneacetone)dipalladium; preferably palladium acetate;

The inorganic base is one of potassium carbonate, sodium carbonate or cesium carbonate; preferably potassium carbonate.

Preferably, the ideal molar dosage of the palladium catalyst is 3-aniline-cyclohexen-2-one:palladium catalyst (molar ratio)=1:0.01-1, more preferably 1:0.02.

And/or, the ideal amount of the inorganic base is 3-aniline-cyclohexen-2-one: inorganic base (molar ratio)=1:2-3, preferably 1:2.

In the method of the present invention, the cyclization reaction in step (2) is carried out in a solvent, and the solvent is DMF, N,N-dimethylacetamide or NMP; preferably DMF. Wherein, the ideal amount of the solvent is 3-aniline-cyclohexen-2-one:solvent=1g:5-15mL.

In the method of the present invention, the ideal reaction temperature of the cyclization reaction in step (2) is 80-140°C; preferably 80-100°C.

Preferably, the step (2) also includes the separation of intermediate products, specifically: passing the product obtained by the cyclization reaction through a silica gel column, and then washing and drying the organic phase to obtain the 1, 2, 3, 9 -Tetrahydrocarbazol-4-one; this purification step can remove mechanical impurities and catalysts, which is beneficial to the next step reaction.

In the method of the present invention, in step (3), the 1,2,3,9-tetrahydrocarbazol-4-one is subjected to a reduction reaction with sodium borohydride; the molar dosage of the sodium borohydride is 1, 2,3,9-tetrahydrocarbazol-4-one: sodium borohydride (molar ratio)=1:1-3, preferably 1:2.

In the method of the present invention, in step (3), the reduction reaction is carried out in a solvent, and the preferred amount of the solvent is 1,2,3,9-tetrahydrocarbazol-4-one:solvent=1g:5- 20mL;

More preferably the solvent is tetrahydrofuran.

In the method of the present invention, the ideal reaction temperature of the reduction reaction in step (3) is 0-50°C; preferably 10-25°C.

Preferably, step (3) also includes separation of intermediate products, specifically: adding water to quench the reduction reaction, extracting the obtained product with dichloromethane, washing with water, and drying to obtain the 4-hydroxy-1,2 , 3,9-tetrahydrocarbazole.

In the method of the present invention, the bromination reagent used in the bromination reaction in step (4) is hydrobromic acid or phosphorus oxytribromide; preferably hydrobromic acid; the consumption of the bromination reagent is 4-hydroxy- 1,2,3,9-tetrahydrocarbazole:bromination reagent=1:1-1.1.

More desirably, when the brominating agent is hydrobromic acid, it exists in the form of a solution, and the suitable concentration of the hydrobromic acid solution is 30%-60%, preferably 48%.

In the method of the present invention, the bromination reaction in step (4) is carried out under the catalysis of a catalyst, preferably the catalyst is iron bromide.

Most preferably, the amount of the catalyst used is 1,2,3,9-tetrahydrocarbazol-4-one:ferric bromide (molar ratio)=1:0.1-0.5.

In the method of the present invention, the reaction temperature of the bromination reaction in step (4) is -20-50°C; preferably 10-20°C.

Preferably, step (4) also includes separation of intermediate products, specifically: washing the organic phase obtained by the bromination reaction with water, drying and concentrating to obtain the 4-bromo-1,2,3,9-tetrahydro Carbazole.

In the preparation method of the present invention, in step (5), the 4-bromo-1,2,3,9-tetrahydrocarbazole is subjected to a dehydrogenation reaction in the presence of tetrachlorobenzoquinone; The molar ratio of bromo-1,2,3,9-tetrahydrocarbazole and tetrachlorobenzoquinone is=1:2-4;

Among them, the use of tetrachlorobenzoquinone is a dehydrogenation agent, and the tetrachlorobenzoquinone is cheap and has good solubility, so that the reaction has a high conversion rate, and the post-processing is simple and easy.

In the preparation method of the present invention, the dehydrogenation reaction in step (5) is carried out in a solvent, and the amount of the solvent is preferably 4-bromo-1,2,3,9-tetrahydrocarbazole: solvent=1g : 5-20mL; more preferably, the solvent is toluene. The reaction conversion rate under the solvent is high, the post-processing is simple, and the solvent is easy to be recovered and applied mechanically.

In the preparation method of the present invention, the reaction temperature of the dehydrogenation reaction in step (5) is 90-130°C; preferably 100-110°C.

Preferably, step (5) also includes a product separation step, specifically: washing the organic phase obtained by the dehydrogenation reaction with water, drying, passing through a silica gel column, and then recrystallizing to obtain the 4-bromocarbazole.

Preferably, the above steps (1)-(5) are all carried out under the protection of an inert gas; the inert gas is preferably nitrogen.

Preferably, the preparation method of 4-bromocarbazole of the present invention comprises the following steps under the protection of inert gas:

(1) 1,3-cyclohexanedione and aniline carry out condensation reaction in toluene in the presence of metal oxide to obtain 3-aniline-cyclohexen-2-one;

(2) The 3-aniline-cyclohexen-2-one is subjected to a cyclization reaction in the presence of a palladium catalyst and an inorganic base to obtain 1,2,3,9-tetrahydrocarbazol-4-one;

The palladium catalyst is one of palladium acetate, 1,1'-bisdiphenylphosphinoferrocene palladium dichloride or tris(dibenzylideneacetone)dipalladium; the molar amount of the palladium catalyst is 3 -aniline-cyclohexen-2-one: palladium catalyst=1:0.01-1;

And/or, the inorganic base is one of potassium carbonate, sodium carbonate or cesium carbonate; the molar dosage of the inorganic base is 3-aniline-cyclohexen-2-one: inorganic base=1:2-3 ;

(3) The 1,2,3,9-tetrahydrocarbazol-4-one is subjected to a reduction reaction with sodium borohydride in tetrahydrofuran to obtain 4-hydroxy-1,2,3,9-tetrahydrocarbazole ;

The dosage of the sodium borohydride is 1,2,3,9-tetrahydrocarbazol-4-one: sodium borohydride=1:1-3;

(4) The 4-hydroxy-1,2,3,9-tetrahydrocarbazole is subjected to a bromination reaction in the presence of a brominating reagent and a catalyst to obtain 4-bromo-1,2,3,9-tetrahydrocarbazole Hydrocarbazole;

The brominating reagent is hydrobromic acid or phosphorus oxybromide, and the amount of the brominating reagent is 4-hydroxy-1,2,3,9-tetrahydrocarbazole:brominating reagent=1:1-1.1;

The catalyst is iron bromide;

(5) The 4-bromo-1,2,3,9-tetrahydrocarbazole is subjected to a dehydrogenation reaction in toluene in the presence of tetrachlorobenzoquinone to obtain the 4-bromocarbazole; the 4 - the molar ratio of bromo-1,2,3,9-tetrahydrocarbazole and tetrachlorobenzoquinone = 1:2-4.

The present invention adopts low-cost conventional raw materials such as 1,3-cyclohexanedione and aniline, and replaces expensive raw materials such as o-nitrophenylboronic acid and o-bromoiodobenzene, and the obtained intermediate can be directly After simple treatment, the next reaction is directly cast. The post-processing is simple and the yield is high, the total yield can reach more than 80%, and the gas chromatography content can reach 99%.

The invention adopts relatively mild processes such as reduction, bromination, dehydrogenation and the like after cyclization to replace high temperature reactions such as triethyl phosphite and triphenylphosphine, and mildly realizes the preparation of 4-bromocarbazole. It reduces the requirements of industrial production on equipment and other conditions, saves energy, and is conducive to the realization of industrial production.

Detailed ways

The following examples are intended to illustrate the present invention, but not to limit the scope of the present invention. The basic raw materials used in the present invention are all conventional commercial products.

Example 1

The present embodiment provides a preparation method of 4-bromocarbazole, specifically, the method comprises the following steps:

(1) Under nitrogen protection, 18.6 g of aniline (molecular weight 93.13, 0.2 mol), 22.4 g of 1,3-cyclohexanedione (molecular weight 112.13, 0.2 mol), 2.0 g of alumina (molecular weight 101.96, 0.02 mol), Toluene 224mL was added to the reaction flask with mechanical stirring, reflux condenser, thermometer and oil bath heating device. The temperature was raised to 110°C, the reaction was terminated after 4 hours, the obtained organic phase was washed with water until neutral, and dried with 20 g of sodium sulfate for 1 hour, and then the organic phase was concentrated to dryness to obtain an off-white solid 3-aniline-cyclohexene-2- Ketone 37.3 g (molecular weight 187.24, 0.2 mol); MS (FAB): m/z 187 (M+);

(2) Under nitrogen protection, 3-aniline-cyclohexen-2-one prepared in step (1), palladium acetate 0.9g (molecular weight 224.29, 0.004mol) and potassium carbonate 55.2g (molecular weight 138, 0.4mol) ) was added to 373 mL of DMF, heated to 100 ° C and reacted for 8 hours to complete the reaction, the resulting product was passed through a 18 g silica gel column, the column liquid was poured into 3740 mL of water, suction filtered, and dried to obtain brownish yellow intermediates 1, 2, 3, 9-Tetrahydrocarbazol-4-one 36.4 g; MS (FAB): m/z 185 (M+);

(3) The intermediate 1,2,3,9-tetrahydrocarbazol-4-one obtained in step (2) was dissolved in 364 mL of tetrahydrofuran, and 15.1 g of sodium borohydride (molecular weight: 37.83 g) was added in three batches at 15°C. , 0.4mol), after reacting at this temperature for 2 hours, 36.4mL of water was added to quench the reaction, the resulting product was extracted with 364mL of dichloromethane, washed with water, and dried with 20g of sodium sulfate to obtain 4-hydroxy-1,2 ,3,9-tetrahydrocarbazole;

(4) The organic phase obtained in step (3) was cooled to 20°C, and 33.7 g of HBr solution (48% concentration) (molecular weight 81, 0.2 mol) and ferric bromide 5.9 g (molecular weight 295.5, 0.02 mol) were added thereto. The reaction was terminated after 4 hours of reaction at 20 °C, the organic phase was washed with water until neutral, dried with 20 g of sodium sulfate, and concentrated to dryness to obtain 49 g of intermediate 4-bromo-1,2,3,9-tetrahydrocarbazole; MS (FAB): m/z 250 (M+);

(5) The intermediate 4-bromo-1,2,3,9-tetrahydrocarbazole obtained in step (4), 490 mL of toluene, and tetrachlorobenzoquinone (molecular weight: 245.88, 0.44 mol) were added to the reaction flask. The reaction was terminated after 4 hours of reaction at 110°C. The obtained organic phase was washed with water until neutral, dried with 20 g of sodium sulfate, then passed through a 18 g silica gel column to remove color, and the column liquid was concentrated to the remaining 49 mL, 100 mL of ethanol was added to it, crystallized at 15 ° C, suction filtration, drying, 38.8 g of white powder 4-bromocarbazole were obtained.

The total yield of the 4-bromocarbazole prepared by the method described in this example was 78.6%, and the purity was 99.36%.

Product melting point: 104.8°C-105.6°C. MS (FAB): m/z 246 (M+). Elemental Analysis C ₁₂ H ₈ BrN: Theory C: 58.51%; H: 3.25%; Br: 32.51%; N: 5.68%. Found C: 58.53%; H: 3.26%; Br: 32.5%; N: 5.67%.

Example 2

The present embodiment provides a preparation method of 4-bromocarbazole, specifically, the method comprises the following steps:

(1) Under nitrogen protection, 18.6 g of aniline (molecular weight 93.13, 0.2 mol), 22.4 g of 1,3-cyclohexanedione (molecular weight 112.13, 0.2 mol), 0.8 g of magnesium oxide (molecular weight 40.30, 0.02 mol), Toluene 224mL was added to the reaction flask with mechanical stirring, reflux condenser, thermometer and oil bath heating device. The temperature was raised to 110°C, the reaction was terminated after 4 hours, the obtained organic phase was washed with water until neutral, and dried with 20 g of sodium sulfate for 1 hour, and then the organic phase was concentrated to dryness to obtain an off-white solid 3-aniline-cyclohexene-2- Ketone 37.4g (molecular weight 187.24, 0.2mol);

(2) Under nitrogen protection, 3-aniline-cyclohexen-2-one, 1,1'-bisdiphenylphosphinoferrocene palladium 2.92 g (molecular weight 731.71 g) obtained in step (1) were , 0.004mol) and 130.3g of cesium carbonate (molecular weight 325.82, 0.4mol) were added to 374mL of N,N-dimethylacetamide, the temperature was raised to 80°C and the reaction was terminated after 8 hours, and the resulting product was passed through a 18g silica gel column. The column liquid was poured into 3740 mL of water, suction filtered, and dried to obtain 36.4 g of the brownish-yellow intermediate 1,2,3,9-tetrahydrocarbazol-4-one;

(3) The intermediate 1,2,3,9-tetrahydrocarbazol-4-one obtained in step (2) was dissolved in 364 mL of tetrahydrofuran, and 15.1 g of sodium borohydride (molecular weight: 37.83 g) was added in three batches at 20° C. , 0.4mol), after 2 hours of reaction at this temperature, 36.4mL of water was added to quench the reaction, the resulting product was extracted with 364mL of dichloromethane, washed with water, and dried with 20g of sodium sulfate to obtain 4-hydroxy-1,2, 3,9-tetrahydrocarbazole;

(4) The organic phase obtained in step (3) was cooled to 15°C, and 33.7 g of HBr solution (48% concentration) (molecular weight 81, 0.2 mol) and ferric bromide 5.9 g (molecular weight 295.5, 0.02 mol) were added thereto. After 4 hours of reaction at 15°C, the reaction was terminated, the organic phase was washed with water until neutral, dried with 20 g of sodium sulfate, and concentrated to dryness to obtain 48.9 g of the intermediate 4-bromo-1,2,3,9-tetrahydrocarbazole ;

(5) The intermediate 4-bromo-1,2,3,9-tetrahydrocarbazole, 489 mL of diethylbenzene, and tetrachlorobenzoquinone (molecular weight 245.88, 0.44 mol) obtained in step (4) were added to the reaction flask , and the reaction was completed after 4 hours at 110 °C. The obtained organic phase was washed with water until neutral, dried with 20 g of sodium sulfate, passed through a 18 g silica gel column to remove color, and the column liquid was concentrated to the remaining 45 mL, 150 mL of ethanol was added to it, crystallized at 10 ° C, suction filtration, and drying to obtain 40.2 g of white powder 4-bromocarbazole.

The total yield of the 4-bromocarbazole prepared by the method described in this example was 81.6%, and the purity was 99.1%.

Example 3

The present embodiment provides a preparation method of 4-bromocarbazole, specifically, the method comprises the following steps:

(1) Under nitrogen protection, 18.6 g of aniline (molecular weight 93.13, 0.2 mol), 22.4 g of 1,3-cyclohexanedione (molecular weight 112.13, 0.2 mol), 2.0 g of alumina (molecular weight 101.96, 0.02 mol), Toluene 224mL was added to the reaction flask with mechanical stirring, reflux condenser, thermometer and oil bath heating device. The temperature was raised to 110°C, the reaction was terminated after 4 hours, the obtained organic phase was washed with water until neutral, and dried with 20 g of sodium sulfate for 1 hour, and then the organic phase was concentrated to dryness to obtain an off-white solid 3-aniline-cyclohexene-2- Ketone 37.4g (molecular weight 187.24, 0.2mol);

(2) Under nitrogen protection, 3-aniline-cyclohexen-2-one obtained in step (1), tris(dibenzylideneacetone) dipalladium 3.66g (molecular weight 915.72, 0.004mol) and potassium carbonate 55.2g (molecular weight 138, 0.4mol) was added to 374mL of NMP, heated to 80°C and reacted for 8 hours to complete the reaction, the obtained product was passed through a 18g silica gel column, the column liquid was poured into 3740mL of water, suction filtered, and dried to obtain brownish yellow Intermediate 1,2,3,9-tetrahydrocarbazol-4-one 36.4g;

(3) The intermediate 1,2,3,9-tetrahydrocarbazol-4-one obtained in step (2) was dissolved in 364 mL of tetrahydrofuran, and 7.6 g of sodium borohydride (molecular weight: 37.83 g) was added in three batches at 15°C. , 0.2mol), after 2 hours of reaction at this temperature, 36.4mL of water was added to quench the reaction, the resulting product was extracted with 364mL of dichloromethane, washed with water, and dried with 20g of sodium sulfate to obtain 4-hydroxy-1,2, 3,9-tetrahydrocarbazole;

(4) The organic phase obtained in step (3) was cooled to 15° C., and 57.3 g of phosphorus oxybromide (molecular weight 286.69, 0.2 mol) was added thereto. After 4 hours of reaction at 15°C, the reaction was terminated, the organic phase was washed with water until neutral, dried with 20 g of sodium sulfate, and concentrated to dryness to obtain 49 g of the intermediate 4-bromo-1,2,3,9-tetrahydrocarbazole;

(5) The intermediate 4-bromo-1,2,3,9-tetrahydrocarbazole obtained in step (4), 490 mL of xylene, and 149.8 of dichlorodicyanobenzoquinone (molecular weight 227, 0.66 mol) were added to In the reaction flask, the reaction was completed after 4 hours at 110°C. The obtained organic phase was washed with water until neutral, dried with 20 g of sodium sulfate, passed through a 18 g silica gel column to remove color, and the column liquid was concentrated to the remaining 50 mL, then 200 mL of ethanol was added to it, crystallized at 10 °C, suction filtration, and drying to obtain a white powder 39.2 g of 4-bromocarbazole.

The total yield of 4-bromocarbazole prepared by the method described in this example was 79.6%, and the purity was 99.22%.

Although the present invention has been described in detail above with general description and specific embodiments, some modifications or improvements can be made on the basis of the present invention, which will be obvious to those skilled in the art. Therefore, these modifications or improvements made without departing from the spirit of the present invention fall within the scope of the claimed protection of the present invention.

Claims (23)

1. a preparation method of 4-bromocarbazole, is characterized in that, synthetic route is as follows:

The method includes the following steps: (1) 1,3-cyclohexanedione and aniline carry out condensation reaction to obtain 3-aniline-cyclohexen-2-one; (2) 1,2,3,9-tetrahydrocarbazol-4-one is prepared by cyclization of the 3-aniline-cyclohexen-2-one; (3) The 1,2,3,9-tetrahydrocarbazol-4-one is reduced to obtain 4-hydroxy-1,2,3,9-tetrahydrocarbazole; (4) The 4-hydroxy-1,2,3,9-tetrahydrocarbazole is brominated to obtain 4-bromo-1,2,3,9-tetrahydrocarbazole; (5) The 4-bromo-1,2,3,9-tetrahydrocarbazole is subjected to dehydrogenation to obtain the 4-bromocarbazole. 2. method according to claim 1, is characterized in that, in step (1), the molar charging ratio of described 1,3-cyclohexanedione and described aniline is 1:0.9-1.05. 3. method according to claim 2, is characterized in that, in step (1), the molar charging ratio of described 1,3-cyclohexanedione and described aniline is 1:1. 4. The method according to claim 1 or 2, wherein the catalyst used in the condensation reaction in step (1) is a metal oxide. 5. The method according to claim 4, wherein the metal oxide is one of alumina, magnesia or calcium oxide. 6. The method according to any one of claims 1 to 3 and 5, wherein the cyclization reaction in step (2) is carried out in the presence of a palladium catalyst and an inorganic base; the inorganic base is carbonic acid One of potassium, sodium carbonate or cesium carbonate. 7. method according to claim 6, is characterized in that, described palladium catalyst is palladium acetate, 1,1 '-bis-diphenylphosphinoferrocene palladium dichloride or tris(dibenzylideneacetone) two A type of palladium. 8. method according to claim 4 is characterized in that, described in step (2), the cyclization reaction is carried out in the presence of palladium catalyst and inorganic base; Described inorganic base is in potassium carbonate, sodium carbonate or cesium carbonate a kind of. 9. method according to claim 8, is characterized in that, described palladium catalyst is palladium acetate, 1,1 '-bis-diphenylphosphinoferrocene palladium dichloride or tris(dibenzylideneacetone) two A type of palladium. 10. The method according to claim 6, wherein the molar dosage of the palladium catalyst is 3-aniline-cyclohexene-2-one: palladium catalyst=1:0.01-1; the molar amount of the inorganic base The dosage is 3-aniline-cyclohexen-2-one: inorganic base=1:2-3. 11. The method according to any one of claims 1-3, 5, 8-10, wherein in step (3), the 1,2,3,9-tetrahydrocarbazol-4-one Reduction with sodium borohydride. 12. The method according to claim 11, wherein the consumption of the sodium borohydride is 1,2,3,9-tetrahydrocarbazol-4-one:sodium borohydride=1:1-3. 13. The method according to claim 12, wherein the consumption of the sodium borohydride is 1,2,3,9-tetrahydrocarbazol-4-one:sodium borohydride=1:2. 14. The method according to any one of claims 1 to 3, 5, 8 to 10, 12, and 13, wherein in step (3), the reduction reaction is carried out in a solvent, and the amount of the solvent is 1 , 2,3,9-tetrahydrocarbazol-4-one: solvent=1 g: 5-20 mL. 15. The method according to claim 14, wherein the solvent is tetrahydrofuran. 16. The method according to any one of claims 1 to 3, 5, 8 to 10, 12, 13, and 15, wherein the bromination reagent used in the bromination reaction described in step (4) is hydrogen bromide acid or phosphorus oxybromide; the bromination reaction described in step (4) is carried out under the catalysis of a catalyst. The method according to claim 16, wherein the amount of the brominating reagent is 4-hydroxy-1,2,3,9-tetrahydrocarbazole:brominating reagent=1:1-1.1. 18. The method of claim 16, wherein the catalyst is iron bromide. 19. The method according to any one of claims 1 to 3, 5, 8 to 10, 12, 13, 17, and 18, wherein in step (5), the 4-bromo-1,2, 3,9-tetrahydrocarbazole is subjected to dehydrogenation reaction in the presence of tetrachlorobenzoquinone; in step (5), the dehydrogenation reaction is carried out in a solvent. 20. The method according to claim 19, wherein the molar ratio of the 4-bromo-1,2,3,9-tetrahydrocarbazole and tetrachlorobenzoquinone is =1:2-4. 21. The method according to claim 19, wherein the amount of the solvent is 4-bromo-1,2,3,9-tetrahydrocarbazole:solvent=1g:5-20mL. 22. The method according to claim 21, wherein in step (5), the solvent is toluene. 23. The method according to claim 1 or 2, wherein the method comprises the following steps under the protection of an inert gas: (1) 1,3-cyclohexanedione and aniline carry out condensation reaction in toluene in the presence of metal oxide to obtain 3-aniline-cyclohexen-2-one; (2) The 3-aniline-cyclohexen-2-one is subjected to a cyclization reaction in the presence of a palladium catalyst and an inorganic base to obtain 1,2,3,9-tetrahydrocarbazol-4-one; The palladium catalyst is one of palladium acetate, 1,1'-bisdiphenylphosphinoferrocene palladium dichloride or tris(dibenzylideneacetone)dipalladium; the molar amount of the palladium catalyst is 3 -aniline-cyclohexene-2-one: palladium catalyst=1:0.01-1; the inorganic base is one of potassium carbonate, sodium carbonate or cesium carbonate; the molar amount of the inorganic base is 3-aniline- Cyclohexen-2-one: inorganic base=1:2-3; (3) The 1,2,3,9-tetrahydrocarbazol-4-one is subjected to a reduction reaction with sodium borohydride in tetrahydrofuran to obtain 4-hydroxy-1,2,3,9-tetrahydrocarbazole ; The consumption of the sodium borohydride is 1,2,3,9-tetrahydrocarbazol-4-one: sodium borohydride=1:1-3; (4) The 4-hydroxy-1,2,3,9-tetrahydrocarbazole is subjected to a bromination reaction in the presence of a brominating reagent and a catalyst to obtain 4-bromo-1,2,3,9-tetrahydrocarbazole Hydrocarbazole; The brominating reagent is hydrobromic acid or phosphorus oxybromide, and the consumption of the brominating reagent is 4-hydroxy-1,2,3,9-tetrahydrocarbazole:brominating reagent=1:1-1.1; The catalyst is iron bromide; (5) The 4-bromo-1,2,3,9-tetrahydrocarbazole is subjected to a dehydrogenation reaction in toluene in the presence of tetrachlorobenzoquinone to obtain the 4-bromocarbazole; the 4 - the molar ratio of bromo-1,2,3,9-tetrahydrocarbazole and tetrachlorobenzoquinone = 1:2-4.