Method for synthesizing 3-bromo-9-ethyl carbazole through reactive extrusion

Abstract

The invention discloses a method for synthesizing 3-bromine-9-ethyl carbazole through reactive extrusion. The method comprises the following reaction steps: (1) adding uniformly mixed 9-ethyl carbazole, N-bromosuccinimide and a solid diluent into a solid feeding bin of a double-screw extruder; (2) adjusting the feeding speed and the screw rotating speed of the double-screw extruder, and dropwise adding auxiliary liquid through a peristaltic pump; and (3) collecting the product, dissolving, filtering, evaporating to remove the solvent and the like to obtain the 3-bromine-9-ethyl carbazole. According to the present invention, the double-screw extruder is adopted to efficiently prepare the 3-bromo-9-ethyl carbazole through the reaction extrusion, such that the use amount of the toxic and harmful solvent is substantially reduced, the product yield is improved, and the good application prospect is provided.

Description

TECHNICAL FIELD

[0001] The present application belongs to the field of organic synthesis, and particularly relates to a method for reaction extrusion synthesis of 3-bromo-9-ethylcarbazole. BACKGROUND

[0002] 3-bromo-9-ethylcarbazole is an important intermediate in organic synthesis, and can be used for preparing optoelectronic devices such as organic light-emitting diodes (OLED) and organic field-effect transistors (OFET) due to its unique conjugated structure and electronic properties. In addition, after proper structural modification, it also has certain biological activity. For example, it can be used as a potential fluorescent probe for biological imaging. It can also be used as a structural unit of drug molecules to participate in drug design and research and development for the treatment of certain diseases by labeling and tracking specific substances or biological processes in the body. The synthesis method mainly uses 9-ethylcarbazole as raw material to react with brominating reagent in a suitable solvent and under initiation conditions to obtain the product.

[0003] On the other hand, due to the environmental pollution problem caused by the use of organic solvents, mechanical chemical methods such as ball mills are also widely used in solvent-free organic synthesis. However, the ball mill cannot realize continuous operation, and its scale-up is limited, and the reaction temperature cannot be accurately controlled. Therefore, it is urgent to develop new solvent-free continuous synthesis technology. Twin-screw extrusion refers to the forced forward conveying of materials under the action of rotating twin screws, and the screws have different thread elements and kneading blocks, which can generate conveying force and shearing and mixing effects, so that the materials can be fully mixed, contacted and interacted during the conveying process. This technology is widely used in the field of plastic processing, but there is not much research in the field of organic synthesis. SUMMARY

[0004] The purpose of the present application is to provide a method for reaction extrusion synthesis of 3-bromo-9-ethylcarbazole. The present application uses twin-screw reaction extrusion technology, uses sodium bicarbonate or potassium bicarbonate as a solid diluent, and uses N,N-dimethylformamide as an auxiliary liquid, and uses 9-ethylcarbazole and N-bromosuccinimide as raw materials, so that 3-bromo-9-ethylcarbazole can be efficiently prepared by reaction extrusion. In the synthesis process, the use of large amounts of organic solvents such as carbon tetrachloride is avoided, the pollution to the environment is reduced, and the yield of the product is higher than that of the traditional solution stirring method, which has the prospect of industrial application.

[0005] In order to achieve the above purpose, the technical scheme adopted by the present application includes: A method for reaction extrusion synthesis of 3-bromo-9-ethylcarbazole, comprising the following steps: (1) adding uniformly mixed 9-ethylcarbazole, N-bromosuccinimide and solid diluent into the solid feeding bin of the twin-screw extruder; (2) adjusting the feeding speed and screw rotation speed of the double screw extruder, and dropping the auxiliary liquid through the peristaltic pump; (3) collecting the product after dissolving, filtering and evaporating the solvent.

[0006] Optionally, the solid diluent is sodium bicarbonate or potassium bicarbonate.

[0007] Optionally, the molar ratio of 9-ethylcarbazole, N-bromosuccinimide and the solid diluent is 1: (1-1.1): (2-4).

[0008] Optionally, the auxiliary liquid is N,N-dimethylformamide.

[0009] Optionally, the feeding speed of the auxiliary liquid is 2-4 mL / min.

[0010] Optionally, the solid feeding speed is 10-20 g / min, and the screw rotation speed is 80-100 rpm.

[0011] Optionally, the reaction crude product is dissolved in an appropriate amount of ethyl acetate, filtered under reduced pressure, and the filtrate is washed with water, and then the ethyl acetate is evaporated to obtain 3-bromo-9-ethylcarbazole.

[0012] The beneficial effects of the present application are: The present application discloses a method for synthesizing 3-bromo-9-ethylcarbazole by reaction extrusion. Advantage one: avoids the large use of organic solvents such as carbon tetrachloride, and reduces environmental pollution; advantage two: the reaction yield can be improved (from 83% to 92%) by using reaction extrusion technology; advantage three: simple post-processing, without recrystallization or column chromatography purification. DETAILED DESCRIPTION

[0013] The technical solutions of the present application will be described below in conjunction with the embodiments, obviously, the described embodiments are part of the embodiments of the present application, rather than all the embodiments. The following reference examples are exemplary, and are only used to explain the present application, and cannot be explained as the limitation of the present application. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative labor are within the scope of protection of the present application.

[0014] The application belongs to the field of organic synthesis, and discloses a method for reaction-extrusion synthesis of 3-bromo-9-ethylcarbazole, which comprises the following reaction steps: (1) adding uniformly mixed 9-ethylcarbazole, N-bromosuccinimide and a solid diluent into a solid feeding bin of a double-screw extruder; (2) adjusting the feeding speed and screw rotating speed of the double-screw extruder, and simultaneously adding an auxiliary liquid dropwise through a peristaltic pump; and (3) collecting the product, and after post-processing such as dissolution, filtration and evaporation of the solvent, 3-bromo-9-ethylcarbazole is obtained. The method realizes efficient preparation of 3-bromo-9-ethylcarbazole through the double-screw extruder, greatly reduces the amount of toxic and harmful solvent used, improves the yield of the product, and has a good application prospect.

[0015] The method for reaction-extrusion synthesis of 3-bromo-9-ethylcarbazole according to the application comprises the following steps: (1) adding uniformly mixed 9-ethylcarbazole, N-bromosuccinimide and a solid diluent into a solid feeding bin of a double-screw extruder; (2) adjusting the feeding speed and screw rotating speed of the double-screw extruder, and simultaneously adding an auxiliary liquid dropwise through a peristaltic pump; (3) collecting the product, and after post-processing such as dissolution, filtration and evaporation of the solvent, 3-bromo-9-ethylcarbazole is obtained.

[0016] In the disclosure, the solid diluent is sodium bicarbonate or potassium bicarbonate, and the auxiliary liquid is N,N-dimethylformamide.

[0017] In the disclosure, the molar ratio of 9-ethylcarbazole, N-bromosuccinimide and the solid diluent is 1: (1-1.1): (2-4).

[0018] In the disclosure, the solid feeding speed is 10-20 g / min, the feeding speed of the auxiliary liquid is 2-4 mL / min, and the screw rotating speed is 80-100 rpm.

[0019] In the disclosure, all reagents are chemical pure reagents.

[0020] The double-screw extruder used in the following examples has the model of CHT20 (Nanjing Kexue Extrusion Machinery Co., Ltd.).

[0021] Example 1: (1) adding 195 g (1.0 mol) of 9-ethylcarbazole, 178 g (1.0 mol) of N-bromosuccinimide and 168 g (2.0 mol) of sodium bicarbonate which are uniformly mixed into a solid feeding bin of a double-screw extruder; (2) The feeding speed of the twin-screw extruder was adjusted to 10 g / min, the dropping speed of the peristaltic pump was adjusted to 2 mL / min, and the screw rotation speed was 80 rpm; (3) The reaction crude product was collected and dissolved in 2000 mL of ethyl acetate. The solution was filtered under reduced pressure through a Buchner funnel. The filtrate was washed with water and then transferred into a round-bottom flask. The ethyl acetate was removed by rotary evaporation to obtain 3-bromo-9-ethylcarbazole 253.9 g (0.93 mol) with a yield of 93.0%.

[0022] Example 2: In step (1), the amount of N-bromosuccinimide was increased to 195.8 g (1.1 mol), and the rest was the same as in Example 1. 3-bromo-9-ethylcarbazole 255.3 g (0.935 mol) was obtained with a yield of 93.5%.

[0023] Example 3: In step (2), the solid feeding speed of the twin-screw extruder was adjusted to 20 g / min, and the rest was the same as in Example 1. 3-bromo-9-ethylcarbazole 251.2 g (0.92 mol) was obtained with a yield of 92.0%.

[0024] Example 4: In step (2), the screw rotation speed was adjusted to 100 rpm, and the rest was the same as in Example 1. 3-bromo-9-ethylcarbazole 256.6 g (0.94 mol) was obtained with a yield of 94.0%.

[0025] Example 5: In step (2), the dropping speed of the peristaltic pump was adjusted to 4 mL / min, and the rest was the same as in Example 1. 3-bromo-9-ethylcarbazole 254.4 g (0.932 mol) was obtained with a yield of 93.2%.

[0026] Example 6: In step (1), the amount of sodium bicarbonate was increased to 336 g (4.0 mol), and the rest was the same as in Example 1. 3-bromo-9-ethylcarbazole 253.1 g (0.927 mol) was obtained with a yield of 92.7%.

[0027] Example 7: In step (1), an equimolar amount of potassium bicarbonate (2.0 mol, 200 g) was used to replace sodium bicarbonate, and the rest was the same as in Example 1. 3-bromo-9-ethylcarbazole 252.3 g (0.924 mol) was obtained with a yield of 92.4%.

[0028] To compare the effect of solid diluent and auxiliary liquid, we also did the experiment of synthesizing 3-bromo-9-ethylcarbazole by twin-screw reactive extrusion without solid diluent and auxiliary liquid: 195 g (1.0 mol) 9-ethylcarbazole and 178 g (1.0 mol) N-bromosuccinimide were mixed and then added into the solid feeding bin of the twin-screw extruder, the feeding speed was adjusted to 10 g / min, the screw rotation speed was 80 rpm, and after the product was collected, dissolved, filtered and the solvent was removed by evaporation, 3-bromo-9-ethylcarbazole was obtained, and the yield data are shown in Table 1.

[0029] Table 1. Control experiment data of solid diluent and auxiliary liquid

[0030] The yield of the control experiment without auxiliary liquid or solid diluent was 45% and 32% respectively, which was significantly lower than the data of Example 1, and it can be seen that both the solid diluent sodium bicarbonate and the auxiliary liquid N,N-dimethylformamide can promote the effect of reactive extrusion, thereby improving the yield of the product.

[0031] In addition, in order to compare the difference between the reactive extrusion technology and the traditional solution stirring reaction, we also did some experiments under the solution stirring condition for comparison, and the results are as follows (Table 2): 195 g (1.0 mol) 9-ethylcarbazole and corresponding N-bromosuccinimide and 3000 mL carbon tetrachloride were added into a reaction bottle, stirring was started and reacted for 12 hours, after the reaction was completed, the product 3-bromo-9-ethylcarbazole was collected after filtration and evaporation of the solvent.

[0032] Table 2. Product yield under traditional stirring mode

[0033] It can be seen that under the traditional solution stirring mode, the yield is higher when the mass ratio of 9-ethylcarbazole to N-bromosuccinimide is 1:1.1, which can reach 83%, but it is still lower than Example 1.

[0034] Therefore, by using the twin-screw reactive extrusion technology, the use of organic solvents is avoided, the pollution to the environment is reduced, and the yield is higher than that of the traditional solution stirring mode (from 83% to 92%).

[0035] It can be understood that the above implementation is only for illustrating the preferred embodiments of the present application, but the present application is not limited thereto. Those skilled in the art can make various modifications and improvements without departing from the spirit and essence of the present application, and these modifications and improvements are also within the protection scope of the present application.

Claims

1. A method for synthesizing 3-bromo-9-ethylcarbazole by reactive extrusion, characterized in that, Includes the following steps: (1) Add the mixed 9-ethylcarbazole, N-bromosuccinimide and solid diluent into the solid feed hopper of the twin-screw extruder; (2) Adjust the feeding speed and screw speed of the twin-screw extruder, and simultaneously add auxiliary liquid by peristaltic pump; (3) The product is obtained by dissolving, filtering and evaporating the solvent.

2. The method for synthesizing 3-bromo-9-ethylcarbazole by reactive extrusion according to claim 1, characterized in that, The solid diluent is sodium bicarbonate or potassium bicarbonate.

3. The method for synthesizing 3-bromo-9-ethylcarbazole by reactive extrusion according to claim 1 or 2, characterized in that, The molar ratio of 9-ethylcarbazole, N-bromosuccinimide and solid diluent is 1:(1-1.1):(2-4).

4. The method for synthesizing 3-bromo-9-ethylcarbazole by reactive extrusion according to claim 1 or 2, characterized in that, The auxiliary liquid is N,N-dimethylformamide.

5. The method for synthesizing 3-bromo-9-ethylcarbazole by reactive extrusion according to claim 1 or 2, characterized in that, The feeding rate of the auxiliary liquid is 2-4 mL / min.

6. The method for synthesizing 3-bromo-9-ethylcarbazole by reactive extrusion according to claim 1 or 2, characterized in that, The solid feeding rate is 10-20 g / min, and the screw speed is 80-100 rpm.

7. The method for synthesizing 3-bromo-9-ethylcarbazole by reactive extrusion according to claim 1 or 2, characterized in that, The crude product was collected, dissolved in an appropriate amount of ethyl acetate, filtered under reduced pressure, and the filtrate was washed with water and the ethyl acetate was removed by evaporation to obtain 3-bromo-9-ethylcarbazole.

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