Green preparation method of carbazole compound and carbazole oxime ester compound

Abstract

The invention provides a green preparation method of a carbazole compound and a carbazole oxime ester compound, and belongs to the technical field of photoinitiators. The green preparation method of the carbazole compound comprises the following steps: performing Friedel-Crafts acylation reaction on a compound shown as a formula I, o-toluic acid and acetic anhydride to obtain a compound shown as a formula II. Therefore, N-ethyl carbazole, o-toluic acid and acetic anhydride are used as raw materials, the Lewis acid type ionic liquid is used as a two-step Friedel-Crafts acylation reaction solvent, and the reaction for preparing 3-acetyl-6-o-methylbenzoyl-N-ethyl carbazole is homogeneous reaction, so that the reaction rate and selectivity are effectively improved, and the yield of 3-acetyl-6-o-methylbenzoyl-N-ethyl carbazole is increased. And after the reaction is finished, the ionic liquid is separated out through liquid separation, washed and recycled, so that the production cost is reduced, the generation of acidic wastewater is greatly reduced, and the treatment cost of three wastes is greatly reduced.

Description

Technical Field

[0001] The present invention relates to the technical field of photoinitiators, and particularly relates to a green preparation method of a carbazole compound and a carbazole oxime ester compound. Background Art

[0002] The chemical name of the carbazole oxime ester photoinitiator is 1-(6-o-methylbenzoyl-N-ethylcarbazole-3-yl)-ethanone oxime-0-acetyl, which has remarkable fluorescence properties and can effectively absorb ultraviolet light. It can undergo electron transfer under light induction and is mainly used in the photocuring process of unsaturated resins. Its structural formula is as follows:

[0003]

[0004] Currently, catalysts such as aluminum trichloride and zinc chloride are generally used for the Friedel-Crafts acylation reaction to synthesize the intermediate 3-acetyl-6-o-methylbenzoyl-N-ethylcarbazole.

[0005] However, this method has the following three disadvantages: Catalysts such as aluminum trichloride and zinc chloride are prone to hydrolysis to release hydrogen chloride, causing pollution; Catalysts such as aluminum trichloride and zinc chloride can complex with acyl chlorides and product ketones, resulting in an increase in the usage amounts of acyl chlorides and catalysts, causing waste of raw materials and increasing costs; Catalysts such as aluminum trichloride and zinc chloride generate a large amount of acidic wastewater during post-treatment and are difficult to recover, causing a large amount of pollution. Summary of the Invention

[0006] In view of this, the purpose of the present invention is to provide a green preparation method of a carbazole compound and a carbazole oxime ester compound, aiming to reduce production costs and the cost of treating three wastes.

[0007] To achieve the above purpose, the present invention provides a green preparation method of a carbazole compound, including the following steps:

[0008]

[0009] (1) The compound of formula I reacts with o-toluic acid and acetic anhydride through a Friedel-Crafts acylation reaction to obtain the compound of formula II.

[0010] Preferably, the step (1) includes:

[0011] (1-1) Prepare a Lewis acid-based ionic liquid;

[0012] (1-2) The compound of formula I reacts with o-toluic acid and acetic anhydride in the Lewis acid-based ionic liquid, and then undergoes post-treatment to obtain the compound of formula II.

[0013] Preferably, the reaction of the compound of formula I with o-toluic acid and acetic anhydride in the Lewis acid-based ionic liquid includes:

[0014] The compound of formula I reacts with o-toluic acid and acetic anhydride successively in a pre-prepared Lewis acid-based ionic liquid to obtain the compound of formula II.

[0015] Preferably, the reaction of the compound of formula I with o-toluic acid and acetic anhydride in the Lewis acid-based ionic liquid includes:

[0016] Adding the compound of formula I and o-toluic acid to the Lewis acid-based ionic liquid, heating to 115-125 °C and reacting for 5-8 h;

[0017] Adding acetic anhydride to the Lewis acid-based ionic liquid and reacting at 60-70 °C for 4-8 h;

[0018] The molar ratio of the compound of formula I to o-toluic acid is 1:1;

[0019] The molar ratio of the compound of formula I to acetic anhydride is 1:1-2.

[0020] Preferably, the reaction of the compound of formula I with o-toluic acid and acetic anhydride in the Lewis acid-based ionic liquid includes:

[0021] The compound of formula I reacts with acetic anhydride and o-toluic acid successively in a pre-prepared Lewis acid-based ionic liquid to obtain the compound of formula II.

[0022] Preferably, the steps of the reaction of the compound of formula I with o-toluic acid and acetic anhydride in the Lewis acid-based ionic liquid include:

[0023] Adding the compound I and acetic anhydride to the Lewis acid-based ionic liquid, heating to 60-70 °C and reacting for 4-8 h;

[0024] Adding o-toluic acid to the Lewis acid-based ionic liquid, heating to 115-125 °C and reacting for 5-8 h;

[0025] The molar ratio of the compound of formula I to acetic anhydride is 1:1;

[0026] The molar ratio of the compound of formula I to o-toluic acid is 1:1-2.

[0027] Preferably, the steps of the post-treatment include:

[0028] Adding a first organic solvent to extract the liquid after the reaction of the compound of formula I with o-toluic acid and acetic anhydride to obtain a first organic phase;

[0029] Adding water to the first organic phase, standing for stratification, adding a first basic solution to adjust the pH value to 6-8, separating the liquid to obtain a second organic phase;

[0030] After distilling and concentrating the second organic phase, a crystallization solvent is added for crystallization, followed by filtration and drying to obtain the compound of Formula II.

[0031] Preferably, the first organic solvent is selected from one of dichloromethane, chloroform, and ethyl acetate;

[0032] The first basic solution is selected from one of sodium bicarbonate solution, sodium carbonate solution, potassium carbonate solution, potassium hydroxide solution, and sodium hydroxide solution;

[0033] The crystallization solvent is selected from one of isopropanol, ethanol, and methanol.

[0034] Preferably, the step of preparing the Lewis acid-based ionic liquid includes:

[0035] N-methylimidazole is added to n-butyl chloride, and the temperature is raised to 70-90 °C for reaction for 20-30 h. Then, the temperature is lowered to 10-30 °C for static separation, and the lower-layer product is obtained by liquid separation;

[0036] The lower-layer product is washed with a second organic solvent, and rotary evaporation is carried out at 70-90 °C for 0.5-2 h to obtain [Bmim]Cl;

[0037] The Lewis acid is added to [Bmim]Cl in a preset ratio in batches to obtain the Lewis acid-based ionic liquid.

[0038] Preferably, the second organic solvent is selected from one of ethyl acetate, isopropyl acetate, dichloromethane, and chloroform;

[0039] The Lewis acid is selected from one of aluminum trichloride, iron trichloride, and zinc chloride;

[0040] The molar ratio of N-methylimidazole to n-butyl chloride is 1:1.1-2;

[0041] The preset ratio is that the molar ratio of [Bmim]Cl to the Lewis acid is 1:1-3.

[0042] The present invention also provides a green preparation method of a carbazole oxime ester compound, including the preparation method of a carbazole compound. The preparation method of the carbazole oxime ester compound further includes:

[0043]

[0044] (2) The compound of Formula II undergoes an oximation reaction to obtain the compound of Formula III;

[0045] (3) The compound of Formula III undergoes an esterification reaction to obtain the compound of Formula IV.

[0046] Preferably, step (2) includes: using a saturated fatty alcohol as a solvent, in the presence of a buffer salt, reacting the compound of formula II with hydroxylamine hydrochloride at a temperature of 75 - 85 °C for 2 - 4 h, then filtering to obtain a filter cake, and finally washing and drying the filter cake with a third organic solvent to obtain the compound of formula III;

[0047] Preferably, step (3) includes: using a halogenated hydrocarbon as a solvent, reacting the compound of formula III with acetic anhydride at a temperature of 25 - 35 °C for 1 - 1.5 h, then separating the liquid and concentrating to obtain a crude product; finally, recrystallizing and purifying the crude product with a fourth organic solvent to obtain the compound of formula IV;

[0048] Preferably, the saturated fatty alcohol is selected from one or more of methanol, ethanol, and isopropanol;

[0049] The buffer salt is selected from one or more of sodium acetate, sodium hydroxide, sodium phosphate, potassium acetate, pyridine, potassium carbonate, and sodium carbonate;

[0050] The third organic solvent is selected from one or more of methanol, ethanol, and isopropanol;

[0051] The halogenated hydrocarbon is selected from one or more of dichloromethane, chloroform, carbon tetrachloride, 1,2 - dichloroethane, and chlorobenzene;

[0052] The fourth organic solvent is selected from one or more of isopropanol, methanol, and ethanol;

[0053] The molar ratio of the compound of formula II to hydroxylamine hydrochloride is 1:1.1 - 1.5;

[0054] The molar ratio of the compound of formula III to acetic anhydride is 1:1.5 - 2.5.

[0055] The present invention provides a green preparation method for a carbazole compound, including the following steps: The compound of formula I reacts with o - toluic acid and acetic anhydride through a Friedel - Crafts acylation reaction to obtain the compound of formula II. Thus, the present invention uses N - ethylcarbazole, o - toluic acid, and acetic anhydride as raw materials, and uses a Lewis acid - type ionic liquid as the solvent for the two - step Friedel - Crafts acylation reaction. The reaction for preparing 3 - acetyl - 6 - o - methylbenzoyl - N - ethylcarbazole is a homogeneous reaction, effectively improving the reaction rate and selectivity. After the reaction, the ionic liquid is separated by liquid separation, washed, and recycled, reducing the production cost. At the same time, the generation of acidic wastewater is greatly reduced, and the three - waste treatment cost is significantly reduced. Description of the Drawings

[0056] Figure 1 It is the HPLC chromatogram of 3 - acetyl - 6 - o - methylbenzoyl - N - ethylcarbazole of the present invention.

[0057] Figure 2This is the HPLC chromatogram of 1-(6-o-methylbenzoyl-N-ethylcarbazole-3-yl)-ethanone oxime-0-acetyl of the present invention. Detailed implementation mode

[0058] Next, the technical solutions in the present invention will be clearly and completely described in conjunction with the embodiments in the present invention.

[0059] The present invention provides a green preparation method for a preparation method of a carbazole compound, including the following steps:

[0060]

[0061] (1) The compound of formula I reacts with o-toluic acid and acetic anhydride through a Friedel-Crafts acylation reaction to obtain the compound of formula II.

[0062] Unless otherwise specified, the present invention has no special requirements for the sources of the preparation raw materials used, and commercially available products well-known to those skilled in the art can be used.

[0063] In the present invention, the step (1) includes:

[0064] (1-1) Prepare a Lewis acid-based ionic liquid;

[0065] (1-2) The compound of formula I reacts with o-toluic acid and acetic anhydride in a Lewis acid-based ionic liquid, and then post-treatment is carried out to obtain the compound of formula II.

[0066] In the present invention, the reaction of the compound of formula I with o-toluic acid and acetic anhydride in a Lewis acid-based ionic liquid may include:

[0067] The compound of formula I reacts with o-toluic acid and acetic anhydride in a pre-prepared Lewis acid-based ionic liquid respectively and successively to obtain the compound of formula II.

[0068] In the present invention, the reaction of the compound of formula I with o-toluic acid and acetic anhydride in a Lewis acid-based ionic liquid may also include:

[0069] Add the compound of formula I and o-toluic acid to a Lewis acid-based ionic liquid, heat up to 115-125 °C and react for 5-8 h;

[0070] Add acetic anhydride to a Lewis acid-based ionic liquid and react at 60-70 °C for 4-8 h;

[0071] The molar ratio of the compound of formula I to o-toluic acid is 1:1;

[0072] The molar ratio of the compound of formula I to acetic anhydride is 1:1-2.

[0073] In the present invention, the reaction of the compound of formula I with o-toluic acid and acetic anhydride in a Lewis acid ionic liquid may include:

[0074] The compound of formula I reacts with acetic anhydride and o-toluic acid successively in a pre-prepared Lewis acid ionic liquid to obtain the compound of formula II.

[0075] In the present invention, the reaction of the compound of formula I with o-toluic acid and acetic anhydride in a Lewis acid ionic liquid may also include:

[0076] Add the compound of formula I and acetic anhydride to the Lewis acid ionic liquid, heat up to 60-70 °C and react for 4-8 h;

[0077] Add o-toluic acid to the Lewis acid ionic liquid, heat up to 115-125 °C and react for 5-8 h;

[0078] The molar ratio of the compound of formula I to acetic anhydride is 1:1;

[0079] The molar ratio of the compound of formula I to o-toluic acid is 1:1-2.

[0080] In the present invention, the post-treatment steps include:

[0081] Add a first organic solvent to extract the liquid after the reaction of the compound of formula I with o-toluic acid and acetic anhydride to obtain a first organic phase;

[0082] Add water to the first organic phase, let it stand for stratification, and add a first basic solution to adjust the pH value to 6-8, separate the layers, and obtain a second organic phase;

[0083] After distilling and concentrating the second organic phase, add a crystallization solvent for crystallization, filtration, and drying to obtain the compound of formula II.

[0084] In the present invention, the first organic solvent is selected from one of dichloromethane, chloroform, and ethyl acetate;

[0085] The first basic solution is selected from one of sodium bicarbonate solution, sodium carbonate solution, potassium carbonate solution, potassium hydroxide solution, and sodium hydroxide solution;

[0086] The crystallization solvent is selected from one of isopropanol, ethanol, and methanol.

[0087] In the present invention, the steps for preparing the Lewis acid ionic liquid include:

[0088] Add N-methylimidazole to n-butyl chloride, heat up to 70-90 °C and react for 20-30 h, then cool down to 10-30 °C, let it stand for stratification, and separate the lower layer product by liquid separation;

[0089] Wash the lower-layer product with a second organic solvent, heat it to 70 - 90 °C and perform rotary evaporation for 0.5 - 2 h to obtain [Bmim]Cl;

[0090] Add the Lewis acid to [Bmim]Cl in batches according to a preset ratio to obtain a Lewis acid-based ionic liquid.

[0091] In the present invention, the reaction equation for preparing [Bmim]Cl is as follows:

[0092]

[0093] In the present invention, the second organic solvent is selected from one of ethyl acetate, isopropyl acetate, dichloromethane, and chloroform;

[0094] The Lewis acid is selected from one of aluminum trichloride, iron trichloride, and zinc chloride.

[0095] The molar ratio of N-methylimidazole to n-butyl chloride is 1:1.1 - 2;

[0096] The preset ratio is that the molar ratio of [Bmim]Cl to the Lewis acid is 1:1 - 3.

[0097] When the molar ratio of [Bmim]Cl to the Lewis acid is 1:1, the chemical formula of the Lewis acid-based ionic liquid is [Bmim]Cl - AlCl 3 、[Bmim]Cl - FeCl 3 、[Bmim]Cl - ZnCl 2 ;

[0098] When the molar ratio of [Bmim]Cl to the Lewis acid is 1:2, the chemical formula of the Lewis acid-based ionic liquid is [Bmim]Cl - Al 2 Cl 6 、[Bmim]Cl - Fe 2 Cl 6 、[Bmim]Cl - Zn 2 Cl 4 ;

[0099] When the molar ratio of [Bmim]Cl to the Lewis acid is 1:3, the chemical formula of the Lewis acid-based ionic liquid is [Bmim]Cl - Al 3 Cl 9 、[Bmim]Cl - Fe 3 Cl 9 、[Bmim]Cl - Zn 3 Cl 6 。

[0100] In the present invention, the reaction equation for preparing the carbazole compound is as follows:

[0101]

[0102] The present invention also provides a green preparation method of a carbazole oxime ester compound, including a preparation method of a carbazole compound. The preparation method of the carbazole oxime ester compound further includes:

[0103] (2) The compound of formula II undergoes an oximation reaction to obtain a compound of formula III;

[0104] (3) The compound of formula III undergoes an esterification reaction to obtain a compound of formula IV.

[0105] In the present invention, step (2) includes: using a saturated fatty alcohol as a solvent, in the presence of a buffer salt, reacting the compound of formula II with hydroxylamine hydrochloride at a temperature of 75 - 85 °C for 2 - 4 h, then filtering to obtain a filter cake, and finally washing and drying the filter cake with a third organic solvent to obtain the compound of formula III;

[0106] In the present invention, step (3) includes: using a halogenated hydrocarbon as a solvent, reacting the compound of formula III with acetic anhydride at a temperature of 25 - 35 °C for 1 - 1.5 h, then separating the liquid and concentrating to obtain a crude product; finally, recrystallizing and purifying the crude product with a fourth organic solvent to obtain the compound of formula IV;

[0107] In the present invention, the saturated fatty alcohol is selected from one or more of methanol, ethanol, and isopropanol;

[0108] The buffer salt is selected from one or more of sodium acetate, sodium hydroxide, sodium phosphate, potassium acetate, pyridine, potassium carbonate, and sodium carbonate;

[0109] The third organic solvent is selected from one or more of methanol, ethanol, and isopropanol;

[0110] The halogenated hydrocarbon is selected from one or more of dichloromethane, chloroform, carbon tetrachloride, 1,2 - dichloroethane, and chlorobenzene;

[0111] The fourth organic solvent is selected from one or more of isopropanol, methanol, and ethanol;

[0112] The molar ratio of the compound of formula II to hydroxylamine hydrochloride is 1:1.1 - 1.5;

[0113] The molar ratio of the compound of formula III to acetic anhydride is 1:1.5 - 2.5.

[0114] In the present invention, the reaction equation for preparing the carbazole oxime ester compound is as follows:

[0115]

[0116] Next, the technical solutions in the present invention will be clearly and completely described in conjunction with the embodiments in the present invention.

[0117] Example 1

[0118] 1) Preparation of intermediate [Bmim]Cl: Add N-methylimidazole (41.05 g) and n-butyl chloride (46.29 g) to a 250 mL three-necked flask in sequence, and heat under oil bath reflux at 80 °C for 24 h to obtain a light yellow liquid. Cool and let stand for liquid separation, and remove the unreacted substances in the upper layer. Then wash the lower layer product with ethyl acetate, and after rotary evaporation at 70 °C for 0.5 h without distillate, 81.2 g of white solid [Bmim]Cl is obtained.

[0119] 2) Prepare Lewis acid ionic liquid according to the molar ratio of [Bmim]Cl / Lewis acid of 1 / 2: Add intermediate [Bmim]Cl (19.49 g) to a 250 mL three-necked flask, start stirring, and add AlCl 3 (29.82 g) in batches until a transparent solution is obtained, and 50 g of Lewis acid ionic liquid [Bmim]Cl-Al 2 Cl 6 .

[0120] 3) Preparation of 3-acetyl-6-o-toluoyl-N-ethylcarbazole: Add the prepared Lewis acid ionic liquid (50 g), N-ethylcarbazole (20 g, 102 mmol) and o-toluic acid (13.95 g, 102 mmol) to a 250 mL three-necked flask, heat to 115 °C and reflux. After the raw materials are completely converted, cool to 60 °C and add acetic anhydride for reaction; after the reaction is completed, extract with dichloromethane to separate the organic phase and the ionic liquid phase. Add water to the organic phase to hydrolyze the unreacted acetic anhydride. After standing for liquid separation, wash with sodium hydroxide solution until nearly neutral. After liquid separation, remove dichloromethane from the organic layer by vacuum distillation. Concentrate the residue, add a crystallization solvent, cool to crystallize, filter and dry to obtain 29 g of 3-acetyl-6-o-toluoyl-N-ethylcarbazole, with a purity of 98.2% and a yield of 79.7%. The remaining ionic liquid phase can be reused after rinsing with hexane and rotary evaporation.

[0121] 4) Add the compound of formula II, 3-acetyl-6-o-methylbenzoyl-N-ethylcarbazole (100 g, 281.3 mmol), absolute ethanol (600 g), sodium acetate trihydrate (49.8 g, 366.0 mmol) and hydroxylamine hydrochloride (22.6 g, 325.2 mmol) to a 2 L three-necked flask, and heat up to 75 °C and stir for reaction for 3 h. After the reaction is completed, slowly cool down to 10 °C, stir and crystallize at 10 °C for 1.5 h and filter to obtain a filter cake; wash the filter cake with 100 g of absolute ethanol; stir and pulp the filter cake with purified water at 30 °C for 80 min and then filter; wash the filter cake with purified water again, and dry the washed filter cake at 50 °C for 40 h to obtain 94.8 g of the compound of formula III, 1-(6-o-methylbenzoyl-N-ethylcarbazol-3-yl)-ethanone oxime, with a purity of 95.2% and a yield of 91.0%.

[0122] 5) Add the compound of formula III, 1-(6-o-methylbenzoyl-N-ethylcarbazol-3-yl)-ethanone oxime (100 g, 269.9 mmol), dichloromethane (300 g), and acetic anhydride (28.8 g, 282.1 mmol) to a 2 L three-necked flask, and stir and react at 25 - 35 °C for 1 - 1.5 h. After the reaction is completed, add 500 g of purified water and stir at 0 - 10 °C for 20 - 40 min, then separate the liquid to obtain the organic phase; concentrate the organic phase under reduced pressure to dryness at 30 - 40 °C. Add 1000 g of isopropanol to the concentrated solid, heat up to 55 - 65 °C and keep stirring for 20 - 40 min, then slowly cool down to 0 - 10 °C for crystallization and filtration. Wash the filter cake with 100 g of isopropanol and dry it under reduced pressure at 40 - 50 °C for 16 - 20 h to obtain 89 g of the compound of formula IV, 1-(6-o-methylbenzoyl-N-ethylcarbazol-3-yl)-ethanone oxime-O-acetyl, with a purity of 98.8% and a yield of 80.0%.

[0123] Example 2

[0124] 1) Preparation of intermediate [Bmim]Cl: Add N-methylimidazole (41.05 g) and n-butyl chloride (46.29 g) to a 250 mL three-necked flask in sequence, heat and reflux in an oil bath at 70 °C for 20 h to obtain a light yellow liquid. Cool and let it stand for layering, and remove the unreacted substances in the upper layer. Wash the lower layer product with ethyl acetate, and after rotary evaporation at 80 °C for 1 h without distillate, obtain 80.7 g of white solid [Bmim]Cl.

[0125] 2) Prepare a Lewis acid-based ionic liquid according to the molar ratio of [Bmim]Cl / Lewis acid of 1 / 1: Add the intermediate [Bmim]Cl (77.96 g) to a 250 mL three-necked flask, start stirring, and add ZnCl 2(60.84 g) until a transparent solution is obtained, and 138.8 g of the Lewis acid ionic liquid [Bmim]Cl-ZnCl is obtained 2 .

[0126] 3) Preparation of 3-acetyl-6-o-methylbenzoyl-N-ethylcarbazole: Add the prepared Lewis acid ionic liquid (100 g), N-ethylcarbazole (40 g, 205 mmol), and o-toluic acid (27.88 g, 205 mmol) to a 250 mL three-necked flask, heat to 125 °C and reflux. After the raw materials are completely converted, cool to 70 °C and add acetic anhydride for reaction; after the reaction is completed, extract with dichloromethane to separate the organic phase and the ionic liquid phase. Add water to the organic phase to hydrolyze the unreacted acetic anhydride. After standing and separating, wash with sodium hydroxide solution until nearly neutral. After liquid separation, the organic layer is distilled under reduced pressure to remove dichloromethane. The remaining concentrate is added with a crystallization solvent and cooled to crystallize. After filtration and drying, 60 g of 3-acetyl-6-o-methylbenzoyl-N-ethylcarbazole is obtained, with a purity of 98.3% and a yield of 82.4%.

[0127] 4) Add 3-acetyl-6-o-methylbenzoyl-N-ethylcarbazole (96 g, 270.1 mmol), methanol (450 g), sodium hydroxide (16 g, 400.0 mmol), and hydroxylamine hydrochloride (22.6 g, 325.2 mmol) to a 2 L three-necked flask, heat to 85 °C and stir for reaction for 2 h. After the reaction is completed, slowly cool to 0 °C, stir and crystallize at 0 °C for 1 h and filter to obtain a filter cake; wash the filter cake with 100 g of anhydrous ethanol; stir and pulp the filter cake with purified water at 20 °C for 40 min and then filter; wash the filter cake with purified water again, and dry the washed filter cake at 40 °C for 20 h to obtain 92.2 g of the compound of formula III, 1-(6-o-methylbenzoyl-N-ethylcarbazol-3-yl)-ethanone oxime, with a purity of 95.9% and a yield of 92.1%.

[0128] 5) Add 1-(6-o-methylbenzoyl-N-ethylcarbazol-3-yl)-ethanone oxime (102 g, 275.3 mmol), dichloromethane (300 g), and acetic anhydride (28.8 g, 282.1 mmol) to a 2 L three-necked flask, stir and react at 25 °C for 1.5 h; after the reaction is completed, add 500 g of purified water and stir at 5 °C for 0.5 h to take the organic phase, and add 2% citric acid aqueous solution to the organic phase multiple times, stir and separate liquid multiple times and then concentrate to dryness under reduced pressure. Then add 1000 g of isopropanol, heat to 60 °C, pulp, filter, and dry to obtain 88.9 g of the compound of formula IV, 1-(6-o-methylbenzoyl-N-ethylcarbazol-3-yl)-ethanone oxime-O-acetyl, with a purity of 99.1% and a yield of 78.3%.

[0129] Example 3

[0130] 1) Preparation of intermediate [Bmim]Cl: Add N-methylimidazole (41.05 g) and n-butyl chloride (46.29 g) to a 250 mL three-necked flask in sequence, and heat under an oil bath at 90 °C for reflux for 30 h to obtain a light yellow liquid. Cool and let it stand for layering, and remove the unreacted substances in the upper layer. Then wash the lower layer product with ethyl acetate, and after rotary evaporation at 90 °C for 1.5 h without distillate, 81.9 g of white solid [Bmim]Cl is obtained.

[0131] 2) Preparation of Lewis acid ionic liquid according to the molar ratio of [Bmim]Cl / Lewis acid of 1 / 1: Add intermediate [Bmim]Cl (77.96 g) to a 250 mL three-necked flask, start stirring, and add ZnCl 2 (60.84 g) in batches until a transparent solution is obtained, and 137.9 g Lewis acid ionic liquid [Bmim]Cl-ZnCl 2 .

[0132] 3) Preparation of 3-acetyl-6-o-toluoyl-N-ethylcarbazole: Add the prepared Lewis acid ionic liquid (100 g), N-ethylcarbazole (40 g, 205 mmol), and o-toluic acid (27.88 g, 205 mmol) to a 250 mL three-necked flask, heat to 120 °C for reflux, and after the raw materials are completely converted, cool to 65 °C and add acetic anhydride for reaction; after the reaction is completed, extract with dichloromethane to separate the organic phase and the ionic liquid phase, add water to the organic phase to hydrolyze the unreacted acetic anhydride, wash with sodium hydroxide solution to near neutral after standing for layering, separate the liquid, and remove dichloromethane by vacuum distillation from the organic layer. Concentrate the residue, add a crystallization solvent, cool to crystallize, filter and dry to obtain 60 g of 3-acetyl-6-o-toluoyl-N-ethylcarbazole, with a purity of 97.8% and a yield of 82.4%.

[0133] 4) Add 3-acetyl-6-o-toluoyl-N-ethylcarbazole (97 g, 272.9 mmol) of formula II compound, propanol (800 g), sodium phosphate (56 g, 341.6 mmol), and hydroxylamine hydrochloride (22.6 g, 325.2 mmol) to a 2 L three-necked flask, heat to 80 °C and stir for reaction for 4 h. After the reaction is completed, slowly cool to 5 °C, stir and crystallize at 5 °C for 1.2 h and filter to obtain a filter cake; wash the filter cake with 100 g of absolute ethanol; stir and pulp the filter cake with purified water at 25 °C for 60 min and then filter; wash the filter cake with purified water again, and dry the washed filter cake at 45 °C for 30 h to obtain 94.3 g of 1-(6-o-toluoyl-N-ethylcarbazol-3-yl)-ethanone oxime of formula III compound, with a purity of 96.1% and a yield of 93.3%.

[0134] 5) Add the compound of formula III, 1-(6-o-methylbenzoyl-N-ethylcarbazole-3-yl)-ethanone oxime (97 g, 261.8 mmol), dichloromethane (300 g), and acetic anhydride (28.8 g, 282.1 mmol) into a 2 L three-necked flask, and stir the reaction at 25 °C for 1.5 h; after the reaction is completed, add 500 g of purified water, stir at 5 °C for 0.5 h, take the organic phase, and add 2% citric acid aqueous solution to the organic phase multiple times, stir and separate the liquid multiple times, and then concentrate under reduced pressure to dryness. Then add 1000 g of isopropanol, heat up to 60 °C, slurry, filter, and dry to obtain 87.1 g of the compound of formula IV, 1-(6-o-methylbenzoyl-N-ethylcarbazole-3-yl)-ethanone oxime-O-acetyl, with a purity of 99.2% and a yield of 80.6%.

[0135] Compared with the prior art, the preparation method of 3-acetyl-6-o-methylbenzoyl-N-ethylcarbazole of the present invention uses N-ethylcarbazole, o-toluic acid and acetic anhydride as raw materials, and uses a Lewis acid-type ionic liquid as the solvent for the two-step Friedel-Crafts acylation reaction. The reaction for preparing 3-acetyl-6-o-methylbenzoyl-N-ethylcarbazole is a homogeneous reaction, which effectively improves the reaction rate and selectivity. After the reaction is completed, the ionic liquid is separated by liquid separation, washed and recycled, reducing the production cost. At the same time, the generation of acidic wastewater is greatly reduced, and the three-waste treatment cost is greatly reduced.

[0136] Although the above embodiments have described the present invention in detail, they are only a part of the embodiments of the present invention rather than all embodiments. People can also obtain other embodiments without creative work based on these embodiments, and these embodiments all belong to the protection scope of the present invention.

Claims

1. A green preparation method of a carbazole compound, characterized in that: The following steps are involved: (1) The compound of formula I is reacted with o-toluic acid and acetic anhydride through Friedel-Crafts acylation to obtain the compound of formula II.

2. The green preparation method of the carbazole compound according to claim 1, characterized in that: The step (1) comprises: (1-1) Preparing Lewis acid ionic liquid; (1-2) The compound of formula I is reacted with o-toluic acid and acetic anhydride in a Lewis acid type ionic liquid, and then post-treated to obtain a compound of formula II.

3. The green preparation method of the carbazole compound according to claim 2, characterized in that: The reaction of the compound of formula I with o-toluic acid and acetic anhydride in a Lewis acidic ionic liquid comprises: Add the compound of formula I and o-toluic acid into Lewis acid type ionic liquid, raise the temperature to 115-125°C and react for 5-8h; Add acetic anhydride to the Lewis acid ionic liquid and react at 60-70° C. for 4-8 hours.

4. The green preparation method of the carbazole compound according to claim 2, characterized in that: The step of reacting the compound of formula I with o-toluic acid and acetic anhydride in a Lewis acid type ionic liquid also includes: Add compound I and acetic anhydride to Lewis acid ionic liquid, raise the temperature to 60-70°C and react for 4-8 hours; Add o-toluic acid into Lewis acid ionic liquid, raise the temperature to 115-125°C and react for 5-8 hours.

5. The green preparation method of the carbazole compound according to any one of claims 2 to 4, characterized in that: The post-processing steps include: Adding a first organic solvent to the liquid after the reaction of the compound of formula I with o-toluic acid and acetic anhydride for extraction to obtain a first organic phase; Add water to the first organic phase and allow to stand for stratification, add the first alkaline solution to adjust the pH value to 6-8, separate the liquids, and obtain a second organic phase; The second organic phase is distilled and concentrated, and then a crystallization solvent is added to crystallize, filtered, and dried to obtain a compound of formula II.

6. The green preparation method of the carbazole compound according to claim 5, characterized in that: The first organic solvent is selected from one of dichloromethane, chloroform and ethyl acetate; The first alkaline solution is selected from one of sodium bicarbonate solution, sodium carbonate solution, potassium carbonate solution, potassium hydroxide solution and sodium hydroxide solution; The crystallization solvent is selected from one of isopropanol, ethanol and methanol.

7. The green preparation method of the carbazole compound according to claim 2, 3, 4 or 6, characterized in that: The step of preparing the Lewis acid type ionic liquid comprises: Add N-methylimidazole to n-butyl chloride, heat to 70-90°C, react for 20-30 hours, cool to 10-30°C, stand and separate to obtain the lower layer product; The lower layer product is washed with a second organic solvent, and the temperature is raised to 70-90°C and rotary evaporated for 0.5-2h to obtain [Bmim]Cl; Lewis acid is added to [Bmim]Cl in batches according to a preset ratio to obtain a Lewis acid type ionic liquid.

8. The green preparation method of the carbazole compound according to claim 7, characterized in that: The second organic solvent is selected from one of ethyl acetate, isopropyl acetate, dichloromethane and chloroform; The Lewis acid is selected from one of aluminum chloride, ferric chloride and zinc chloride; The molar ratio of N-methylimidazole to n-butyl chloride is 1:1.1-2; The preset ratio is a molar ratio of [Bmim]Cl to Lewis acid of 1:1 to 3.

9. A green preparation method of a carbazole oxime ester compound, comprising the green preparation method of 3-acetyl-6-o-methylbenzoyl-N-ethylcarbazole according to any one of claims 1 to 8, wherein the green preparation method of the carbazole oxime ester compound further comprises: (2) the compound of formula II is subjected to an oximation reaction to obtain a compound of formula III; (3) The compound of formula III is subjected to esterification reaction to obtain the compound of formula IV.

10. The green preparation method of oxime ester compound according to claim 9, characterized in that: The step (2) comprises: using a saturated fatty alcohol as a solvent, in the presence of a buffer salt, reacting the compound of formula II with hydroxylamine hydrochloride at a temperature of 75 to 85° C. for 2 to 4 hours, filtering to obtain a filter cake, and finally washing the filter cake with a third organic solvent and drying to obtain a compound of formula III; The step (3) comprises: using a halogenated hydrocarbon as a solvent, reacting the compound of formula III with acetic anhydride at a temperature of 25 to 35° C. for 1 to 1.5 hours, and then separating and concentrating the liquids to obtain a crude product; and finally, recrystallizing and purifying the crude product with a fourth organic solvent to obtain a compound of formula IV; The saturated fatty alcohol is selected from one or more of methanol, ethanol and isopropanol; The buffer salt is selected from one or more of sodium acetate, sodium hydroxide, sodium phosphate, potassium acetate, pyridine, potassium carbonate, and sodium carbonate; The third organic solvent is selected from one or more of methanol, ethanol, and isopropanol; The halogenated hydrocarbon is selected from one or more of dichloromethane, chloroform, carbon tetrachloride, 1,2-dichloroethane, and chlorobenzene; The fourth organic solvent is selected from one or more of isopropanol, methanol, and ethanol; The molar ratio of the compound of formula II to hydroxylamine hydrochloride is 1:1.1-1.5; The molar ratio of the compound of formula III to acetic anhydride is 1:1.5-2.5.

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