CN112209869B - Method for synthesizing high-purity 3-bromo-N-phenylcarbazole - Google Patents
Method for synthesizing high-purity 3-bromo-N-phenylcarbazole Download PDFInfo
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Abstract
The invention discloses a method for synthesizing high-purity 3-bromo-N-phenylcarbazole, belonging to the technical field of chemistry. The method comprises the following steps: dissolving N-phenylcarbazole in a solvent, sequentially adding a brominating agent and an oxidant at the low temperature of-20-10 ℃, after the adding is finished, keeping the reaction temperature at-20-10 ℃ for reaction until the conversion rate of the N-phenylcarbazole reaches more than or equal to 99%, and stopping the reaction, wherein the temperature change of the reaction system is kept within 5 ℃ when the brominating agent and the oxidant are added; after the reaction is finished, the reaction system is sequentially subjected to pH adjustment to be neutral, washing, rotary evaporation, recrystallization and vacuum drying to obtain the high-purity 3-bromine-N-phenylcarbazole. The oxidation bromination method used in the invention has the characteristics of high atom utilization rate, low raw material cost, high reaction selectivity, short preparation period, simple preparation operation and easy control of reaction.
Description
Technical Field
The invention belongs to the technical field of organic synthesis of N-phenylcarbazole derivatives, and particularly relates to a method for synthesizing 3-bromo-N-phenylcarbazole through oxidation bromination reaction of N-phenylcarbazole.
Background
An Organic Light Emitting Diode (OLED) has excellent characteristics of low power consumption, high brightness, fast response, thin thickness, wide viewing angle, full solid state, self-luminescence, flexibility, and the like; the organic light emitting diode can be applied to wider flat panel displays and semiconductors, has great market prospect in the fields of solid state lighting and flat panel display, and is one of the focus of attention and research hotspots in the scientific research community and the industrial community. OLEDs are composed of organic semiconductor materials, light emitting materials, and electrode stacks, with organic electroluminescent materials having the greatest impact on their performance. The organic electroluminescent material is divided into a carrier transport material and a luminescent material, the luminescent material is divided into three basic color light materials of red, green and blue, the chemical structure of the phosphorescent luminescent material as a main luminescent material mostly contains carbazole groups, and the application of a compound containing phenylcarbazole groups in phosphorescent main materials is most extensive. The 3-bromine-N-phenylcarbazole is an important intermediate for synthesizing a compound containing phenylcarbazole groups, can synthesize N-phenylcarbazole-3-boric acid, and then synthesizes a series of organic electroluminescent materials containing macromolecules containing phenylcarbazole groups through Suzuki coupling, Buchwald-Harwig coupling reaction and the like. For example, the N-aryl carbazole triphenylamine structural material has excellent hole transport performance and good thermal stability, and can be practically applied to organic electroluminescent materials as an important hole material.
Currently, the main four routes for the synthesis of 3-bromo-N-phenylcarbazole are:
chinese patent application No. 201110156767.X in 19/12/2012 and Chinese patent application No. 201310606035.5 in 26/2/2014 both disclose a preparation method of N-phenyl-3-bromocarbazole, carbazole is taken as a raw material, 3-bromocarbazole is obtained by NBS bromination, and then the carbazole and halobenzene are subjected to C-N coupling reaction to obtain a target product, wherein the synthesis process is as follows:
(II) Chinese patent application No. 201110382138.9 discloses a preparation method of high-purity 3-bromo-N-phenylcarbazole in 6.13.2012, carbazole is taken as a raw material, the carbazole and halobenzene are subjected to Ullmann reaction to obtain N-phenylcarbazole, and the N-phenylcarbazole is subjected to N-bromosuccinimide (NBS) bromination to obtain a target product, wherein the synthesis process is as follows:
thirdly, taking 2,2' -dibromo biphenyl as a raw material, and performing coupling, ring closing and NBS bromination on the raw material and aniline to obtain a target product as shown in the following;
in 2017, 12 and 8, the Chinese patent application No. 201710375444.7 discloses a preparation method of high-purity 3-bromo-9-phenylcarbazole, p-dibromobenzene is used as a raw material, nitration is carried out to obtain 1, 4-dibromo-2-nitrobenzene, the 1, 4-dibromo-2-nitrobenzene reacts with diphenylamine to obtain (4-bromo-2-nitrophenyl) diphenylamine, and then reduction and diazotization ring closure reaction are carried out to obtain 3-bromo-N-phenylcarbazole, wherein the route is shown as follows.
The method for synthesizing 3-bromo-N-phenylcarbazole comprises the following steps: in the route (I), electrophilic bromination reaction of carbazole may occur at C1, C8, C3 and C6, so that the disadvantage of more byproducts exists, and in addition, the 3-bromocarbazole has the defect of generating more complex byproducts by reacting with another molecule of 3-bromocarbazole in the Ullmann reaction; in the route (II), the N-phenylcarbazole can effectively avoid the interference of other nucleophilic reagents, and simultaneously the probability of electrophilic substitution of C1 and C8 can be effectively reduced and the selectivity of the target product 3-bromo-N-phenylcarbazole is improved due to the steric hindrance effect of a benzene ring of the N-phenylcarbazole, but the N-phenylcarbazole bromination reaction uses bromization reagents such as NBS, bromine, dibromohydantoin and the like, so that the N-phenylcarbazole has the defects of high cost, low atom utilization rate, serious pollution and the like; the routes (three) and (four) have the defects of complex reaction steps, harsh conditions, low total reaction yield and low price and easy obtainment of carbazole, and the method for synthesizing 3-bromo-N-phenylcarbazole by taking carbazole as a raw material is a more mature, economic and simple synthesis method. Therefore, the route (II) is a more ideal method for synthesizing 3-bromo-N-phenylcarbazole, but the preparation process of the existing 3-bromo-N-phenylcarbazole is complex, and the bromination reagent of N-phenylcarbazole has the defects of high cost, large pollution, low atom utilization rate, poor selectivity and the like, for example, NBS, dibromohydantoin and the like are used as electrophilic bromination reagents of the reaction: firstly, under the condition of a proton type solvent, the solubility and the solvation rate of N-phenylcarbazole are low, and the defects of poor reaction conversion rate and selectivity exist; ② under the condition of aprotic polar solvent or aprotic nonpolar solvent, because of the contradiction between the solubility of N-phenylcarbazole and the solvation rate of NBS, there is the defect that the reaction has high selectivity and high conversion rate; thirdly, the bromine source has high cost and more three wastes; in addition, the elemental bromine has strong corrosivity and toxicity, only half of bromine is utilized in the reaction process, and the other half generates hydrogen bromide without utilization, so that the defects of low bromine atom utilization rate, serious pollution and the like exist.
In 2012, Li Meng et al published a review article in Heilongjiang sciences (Vol. 3, No. 1, pages 26-27, 2012) entitled "Synthesis of 3-bromo-9-Phenylcarbazole" for the Synthesis of 3-bromo-9-Phenylcarbazole, which summarizes NBS, elemental bromine (Br)2)、KBr/KBrO3And the reaction yield of synthesizing the 3-bromo-9-phenylcarbazole from the N-phenylcarbazole under the conditions of three bromination reagents. Wherein, the bromine as brominating agent has poor reaction selectivity and low product yield; NBS as a brominating agent has high product yield, but has the defects of complex post-treatment, more three wastes and the like; KBr/KBrO3When the bromine compound is used as a brominating reagent, active bromine molecules are generated under the condition that acid (sulfuric acid or acetic acid) is used as a solvent and then participate in bromination reaction, but the defects of harsh reaction conditions, complex post-treatment, low atom utilization rate and the like exist. In particular, the bromination system is KBr/KBrO3In the process, potassium bromate and potassium bromide are jointly used as a brominating agent for reaction, namely a bromine source provider, wherein the potassium bromate also plays a role of an oxidizing agent, KBr is used as a reducing agent to firstly react to generate a bromine simple substance to participate in the reaction, and the reaction is carried out under the condition of an acidic solvent (sulfuric acid or acetic acid), so that the reaction risk coefficient is large, the post-treatment process is complex, and the industrial production is difficult.
Therefore, a green and environment-friendly preparation method is sought, and the problem of obtaining high-purity 3-bromo-N-phenylcarbazole is a problem which needs to be solved at present.
Disclosure of Invention
1. Problems to be solved
The invention aims to improve the existing method for synthesizing 3-bromo-N-phenylcarbazole by taking N-phenylcarbazole as a raw material, and provides a novel method for synthesizing 3-bromo-N-phenylcarbazole through N-phenylcarbazole oxidation bromination reaction, which has the advantages of high atom utilization rate, simple post-treatment operation, suitability for industrial production, greenness, economy and environmental protection.
2. Technical scheme
In order to solve the problems, the technical scheme adopted by the invention is as follows:
a method for synthesizing high-purity 3-bromine-N-phenylcarbazole comprises the following steps: dissolving N-phenylcarbazole in a solvent, sequentially adding a brominating agent and an oxidant at the low temperature of-20-10 ℃, after the adding is finished, keeping the reaction temperature at-20-10 ℃ for reaction until the conversion rate of the N-phenylcarbazole reaches more than or equal to 99%, and stopping the reaction, wherein the temperature change of the reaction system is kept within 5 ℃ when the brominating agent and the oxidant are added; after the reaction is finished, the reaction system is sequentially subjected to pH adjustment to be neutral, washing, rotary evaporation, recrystallization and vacuum drying to obtain the high-purity 3-bromine-N-phenylcarbazole.
Specifically, the method for synthesizing the high-purity 3-bromo-N-phenylcarbazole comprises the following steps:
dissolving N-phenylcarbazole in an organic solvent under the condition of room temperature, uniformly stirring, then reducing the temperature of a reaction system to-20-10 ℃, adding a quantitative brominating agent, adding an oxidant in batches after the temperature of the system is constant, continuously reacting for 4-12 hours under the condition of-20-10 ℃, and stopping the reaction when the conversion rate of the N-phenylcarbazole is more than or equal to 99% through liquid phase detection. After the reaction is finished, adding a quantitative saturated aqueous solution of sodium carbonate into the reaction system to adjust the pH of the mixed solution to be neutral, washing for 3 times by adopting a water washing separation method, and removing the organic solvent by rotary evaporation to obtain a crude product; and then, purifying the crude product for multiple times by adopting a recrystallization method, and drying in vacuum to obtain the high-purity 3-bromo-N-phenylcarbazole.
Further, the brominating agent is a bromine-containing compound, including hydrobromic acid, potassium bromide, sodium bromide, ammonium bromide and lithium bromide.
Further, the mass fraction of the brominating agent is 20-50%.
Further, the oxidant is a compound containing peroxide or potassium persulfate, preferably hydrogen peroxide, sodium peroxide and magnesium peroxide.
Further, the reaction formula of synthesizing 3-bromo-N-phenylcarbazole by N-phenylcarbazole oxybromination reaction with a compound containing peroxy groups as an oxidant is shown as follows:
further, the mass fraction of the oxidant is 20-40%.
Furthermore, the brominating agent is dropwise added in a titration mode, the titration speed is 1-5 mL/min, and the temperature change of a reaction system in the adding process of the brominating agent can be ensured to be small.
Furthermore, the oxidant is dropwise added in a titration mode, the titration speed is 0.5-1.5 mL/min, and the temperature change of a reaction system in the oxidant adding process can be ensured to be small.
Furthermore, the molar ratio of the brominating agent to the oxidant to the N-phenylcarbazole is (1.00-1.20): 1.05-1.25): 1.
Furthermore, the solvent is one or a mixture of more of n-hexane, dichlorobenzene, dichloromethane, dichloroethane, carbon tetrachloride, trichloromethane, chlorobenzene, carbon disulfide and the like, and is a solvent with poor water solubility, so that the purification of the product is facilitated.
Further, since the reaction product has high purity, purification can be achieved by recrystallization in which one or more of n-hexane, ethanol, methanol, xylene, ethyl acetate, and the like are used as a recrystallization solvent.
3. Advantageous effects
Compared with the prior art, the invention has the beneficial effects that:
(1) the oxidation bromination method used by the invention has the characteristics of high atom utilization rate, low raw material cost, high reaction selectivity, short preparation period, simple preparation operation and easy control of reaction;
(2) the invention has the advantages of better green, non-toxic and harmless performance, and avoids the pollution and harm of bromization reagents such as NBS, bromine, dibromohydantoin and the like to the environment;
(3) the method has the advantages of high yield and low preparation cost, has the feasibility of industrialization, and develops a synthetic method of 3-bromo-N-phenylcarbazole derivatives as intermediates in the design of organic photoelectric materials;
(4) the brominating agent is a bromine-containing compound, preferably hydrobromic acid, and avoids the complex post-treatment process caused by introducing other non-hydrogen ions; the mass fraction of the brominating agent is selected within the range of 20-50%, so that the reaction dropping speed and high solvent stability are conveniently controlled, and the generation of a dibromo product is conveniently controlled when a brominating agent solution is added, wherein the ratio of an inorganic phase to an organic phase is too high due to the fact that the mass fraction of the brominating agent is lower than 20%, so that the bromination conversion rate is influenced, and the reaction selectivity is poor due to the fact that a bromine simple substance with higher concentration exists and the acidity is too strong due to the fact that the mass fraction of the brominating agent is higher than 50%; the titration speed of the brominating agent is controlled to be 1-5 mL/min, so that the temperature of a reaction system is not greatly changed in the adding process of the brominating agent, and the generation of a dibromo product during the adding of the brominating agent is reduced;
(5) the oxidant of the invention is preferably a compound containing peroxy radicals, and the hydrogen peroxide is particularly selected to have the advantages of easy control of the concentration, the addition speed, high atom utilization rate (the only byproduct is water), convenient operation and treatment and the like, and sodium peroxide, magnesium peroxide and the like have the danger of explosion or combustion in organic solvents and are not easy to control the reaction temperature; the mass fraction of the oxidant is 20-40%, which is convenient for controlling the dropping speed and has high reaction selectivity, wherein the mass fraction of the oxidant is lower than 20% to cause slow reaction speed and excessive decomposition of hydrogen peroxide to influence the oxidation effect, and the mass fraction of the oxidant is higher than 40% to cause difficulty in controlling the reaction temperature and explosion danger in an organic solvent; the titration speed of the oxidant is controlled to be 0.5-1.5 mL/min, so that the temperature change of a reaction system in the adding process of the oxidant can be ensured to be small, and high reaction speed and high selectivity are ensured;
(6) the solvent with poor water solubility is used, and is convenient to recycle, so that the solvent loss is reduced, and the production cost is reduced;
(7) after the reaction is finished, the PH value is adjusted to be neutral so as to neutralize excessive bromine simple substance or hydrobromic acid, the bromine simple substance or the hydrobromic acid is converted into inorganic salts such as potassium bromide and the like dissolved in water, and the inorganic salts are removed from an inorganic layer in the liquid separation process, so that the bromine content of impurities in the product is reduced;
(8) the temperature of the reaction system is-20-10 ℃, wherein the reaction activity is high when the temperature is higher than 10 ℃, so that the competition of dibromo-reaction on mono-bromination reaction is facilitated, and the reaction selectivity is poor; when the temperature is lower than-20 ℃, N-phenylcarbazole is separated out from the solvent and has the condition of solid-liquid inclusion, so that dibromo products are increased, and the selectivity of the reaction is reduced;
(9) the excessive brominating agent ensures that the reaction conversion rate is more than or equal to 99 percent, and reduces the residue of raw materials; the purpose of excess oxidant is to make up for the shortage of oxidant caused by factors such as decomposition or reaction with impurities and ensure that the brominating reagent is completely converted into active bromine molecules;
(10) according to the invention, N-phenylcarbazole is used as a reactant raw material, the N-phenylcarbazole is obtained by introducing phenyl to N-H at the 9 th position of carbazole, and the introduction of phenyl increases the electricity supply of N pairs of carbazoles C1, C3, C6 and C8, so that the selectivity of carbazole bromination is greatly reduced; bromination at C1 and C8 positions of carbazole is relatively difficult due to steric hindrance of phenyl group; however, the selectivity of the C3 and C6 sites of the N-phenylcarbazole is more difficult than that of carbazole, and N-phenyl also participates in bromination reaction, so that the high-selectivity bromination of the N-phenylcarbazole to obtain 3-bromo-N-phenylcarbazole is more difficult, and the bromination process is not easy to control; n-phenylcarbazole is obviously better in solubility than carbazole due to the substitution of N-H by phenyl; but the solubility of the dibromo-product 3, 6-dibromo-N-phenylcarbazole is poor, if the bromine source is too much, more 3, 6-dibromo-N-phenylcarbazole is generated, and high-purity 3-bromo-N-phenylcarbazole is difficult to obtain; therefore, strict control of conditions such as bromine source selection, bromine source equivalent, reaction temperature and the like is the key to solving the problem of bromination selectivity of the N-phenylcarbazole and obtaining the high-purity 3-bromine-N-phenylcarbazole.
Drawings
FIG. 1 is a schematic diagram of the reaction formula for synthesizing 3-bromo-N-phenylcarbazole according to the present invention;
FIG. 2 is a NMR spectrum of 3-bromo-N-phenylcarbazole in example 1 of the present invention;
FIG. 3 is the NMR spectrum of 3-bromo-N-phenylcarbazole in example 1 of the present invention.
Detailed Description
The above-mentioned aspects of the present invention will be further described in detail with reference to the following examples for better understanding of the objects, technical solutions and advantages of the present invention, but the scope of the above-mentioned subject matter of the present invention should not be construed as being limited to the following examples, and all the techniques based on the above-mentioned aspects of the present invention are within the scope of the present invention.
Example 1
Adding 24.3g N-phenylcarbazole (99 percent, 0.10mol) and 50mL of dichloromethane into a 250mL four-neck round-bottom flask provided with a stirrer and a thermometer at room temperature, stirring until the materials are completely dissolved, and then reducing the temperature of a reaction system to-10 ℃; 24.3g of hydrobromic acid (40%, 0.12mol and 17.6mL) is dropwise added, 13.6g of hydrogen peroxide (30%, 0.12mol and 12.2mL) is dropwise added when the reaction temperature is constant at minus 10 ℃, wherein the dropping speed of a brominating agent is 3.0mL/min, the dropping speed of an oxidizing agent is 0.5mL/min, and the reaction temperature can be strictly controlled below minus 10 ℃ in the dropping process; reacting for 6 hours at the temperature of minus 10 ℃, and stopping the reaction when the conversion rate of the N-phenylcarbazole is more than or equal to 99% by liquid phase detection. Adding a certain amount of saturated aqueous solution of sodium carbonate into the reaction system after the reaction is finished to adjust the pH of the mixed solution to be neutral, washing for 3 times by adopting a water washing separation method, removing dichloromethane by rotary evaporation to obtain a crude product, recrystallizing the crude product with 100mL of ethanol for three times to obtain a white solid, transferring the white solid into a vacuum drying oven at 60 ℃ and PTrueDrying under the condition of 0.095MPa for 3 hours to obtain 26.3g of white crystalline 3-bromo-N-phenylcarbazole (the content is more than or equal to 99% by HPLC), and the yield is 81.6%.
FIG. 2 shows the NMR spectrum of 3-bromo-N-phenylcarbazole of this example, in which1H NMR(400MHz, DMSO-d6):δ＝7.30(s,1H),7.32(s,1H),7.62-7.56(m,6H),7.68(td,J＝8.0,4.0Hz,2H),8.58(s, 2H)。
FIG. 3 shows the NMR carbon spectrum of 3-bromo-N-phenylcarbazole of this example, in which13C NMR(151MHz, DMSO-d6):δ＝112.3,112.9,124.0,124.2,127.2,128.7,129.9,130.7,130.8,136.4,139.7。
Example 2
Adding 243.3g N-phenylcarbazole (99 percent, 1.00mol) and 500mL of dichloromethane into a 1000mL four-neck round-bottom flask provided with a stirrer and a thermometer at room temperature, stirring until the materials are completely dissolved, and then reducing the temperature of a reaction system to-10 ℃; dropwise adding 212.4g of hydrobromic acid (40%, 1.05mol, 153.9mL), and dropwise adding 119.0g of hydrogen peroxide (30%, 1.05mol, 107.2mL) at-10 ℃ until the reaction temperature is constant, wherein the dropping speed of a brominating agent is 3.0mL/min, the dropping speed of an oxidizing agent is 0.5mL/min, and the reaction temperature can be strictly controlled below-10 ℃ in the dropping process; reacting for 6 hours at the temperature of minus 10 ℃, and stopping the reaction when the conversion rate of the N-phenylcarbazole is more than or equal to 99% by liquid phase detection. Adding a certain amount of saturated aqueous solution of sodium carbonate into the reaction system after the reaction is finished to adjust the pH of the mixed solution to be neutral, washing for 3 times by adopting a water washing separation method, removing dichloromethane by rotary evaporation to obtain a crude product, recrystallizing the crude product with 500mL of ethanol for three times to obtain a white solid, transferring the white solid into a vacuum drying oven at 60 ℃ and PTrueDrying under the condition of 0.095MPa for 3 hours to obtain 283.2g of white crystalline 3-bromo-N-phenylcarbazole (the content is more than or equal to 99% by HPLC), and the yield is 87.9%.
Example 3
This embodiment is substantially the same as embodiment 1, except that: 40.5g of hydrobromic acid (20%, 0.10mol, 35.0mL) was added, and 17.9g of hydrogen peroxide (20%, 0.105mol, 16.7mL) was added.
In the embodiment, after the reaction is finished, the conversion rate of N-phenylcarbazole is not up to 99% by HPLC (high performance liquid chromatography) detection, and the yield of 3-bromo-N-phenylcarbazole is 24.5 g (the HPLC detection content is not less than 99%), and is 76.0%; in the reaction system process of adding hydrobromic acid and hydrogen peroxide, the volume ratio of an inorganic phase to an organic phase is close to 1:1, and the generated bromine molecule concentration is too low to cause that N-phenylcarbazole cannot be completely converted into 3-bromine-N-phenylcarbazole, so that the conversion rate and the yield of the reaction are influenced.
Example 4
This embodiment is substantially the same as embodiment 1, except that: 19.4g of hydrobromic acid (50%, 0.12mol, 12.8mL) was added, and 10.6g of hydrogen peroxide (40%, 0.125mol, 9.2mL) was added.
In the embodiment, after the reaction is finished, HPLC (high performance liquid chromatography) detects that N-phenylcarbazole is completely converted, and 23.4g of 3-bromo-N-phenylcarbazole (the HPLC detection content is not less than 99%) has a yield of 72.6%; in the process of adding hydrobromic acid and hydrogen peroxide, the temperature of a reaction system is not easy to control, an excessive bromine source system causes the increase of generated 3, 6-dibromo-N-phenylcarbazole, the solvent ratio of 3, 6-dibromo-N-phenylcarbazole in most organic solvents is poor, the 3, 6-dibromo-N-phenylcarbazole is not easy to separate from 3-bromo-N-phenylcarbazole through recrystallization and other means, and the defects of low selectivity, low yield and the like are overcome although the conversion rate is high.
Example 5
Under the condition of room temperature, adding 24.3g N-phenylcarbazole (99 percent, 0.10mol) and 50mL normal hexane into a 250mL four-neck round-bottom flask provided with a stirrer and a thermometer, stirring until the phenylcarbazole and the normal hexane are completely dissolved, and then reducing the temperature of a reaction system to-20 ℃; dropwise adding 35.7g of potassium bromide aqueous solution (40 percent and 0.12mol), and dropwise adding 108.1 g of potassium persulfate aqueous solution (30 percent and 0.12mol) at the temperature of minus 20 ℃ until the reaction temperature is constant, wherein the dropping speed of a brominating agent is 3.0mL/min, the dropping speed of an oxidizing agent is 0.5mL/min, and the reaction temperature can be strictly controlled below minus 20 ℃ in the dropping process; reacting for 12 hours at the temperature of minus 20 ℃, and stopping the reaction when the conversion rate of the N-phenylcarbazole is more than or equal to 99% by liquid phase detection. Adding quantitative saturated aqueous solution of sodium carbonate into the reaction system after the reaction is finished to adjust the pH of the mixed solution to be neutral, washing for 3 times by adopting a water washing separation method, removing n-hexane by rotary evaporation to obtain a crude product, recrystallizing the crude product for three times by using 100 x 3mL of ethanol to obtain a white solid, transferring the white solid into a vacuum drying oven at 60 ℃ and PTrueOven drying under 0.095MPa for 3 hrThen 23.7g of white crystalline 3-bromo-N-phenylcarbazole is obtained (the content is more than or equal to 99% by HPLC detection), and the yield is 73.6%.
The method for removing potassium ions and sulfate radicals in the reaction system comprises the following steps: after the reaction is finished and neutralized to be neutral, the inorganic layer is removed by extracting and separating for many times, and potassium ions and sulfate ions are separated and removed in the inorganic phase.
In the reaction process of the embodiment, under the conditions that the temperature is-20 ℃ and N-hexane is used as a solvent, part of N-phenylcarbazole exists in a solid state and is a solid-liquid mixture, the volume ratio of an inorganic phase to an organic phase is greater than 2:1 after a bromine source system is added, so that the bromine molecule concentration is too low, the reaction speed is seriously influenced, meanwhile, a large amount of 3, 6-dibromo-N-phenylcarbazole is generated, the separation is difficult, and the yield of 3-bromo-N-phenylcarbazole is not ideal.
Example 6
Adding 24.3g N-phenylcarbazole (99 percent, 0.10mol) and 50mL of carbon disulfide into a 250mL four-neck round-bottom flask provided with a stirrer and a thermometer at room temperature, stirring until the phenylcarbazole and the carbon disulfide are completely dissolved, and then reducing the temperature of a reaction system to 10 ℃; dropwise adding 30.9g of sodium bromide aqueous solution (40 percent and 0.12mol), and dropwise adding 31.2 g of sodium peroxide aqueous solution (30 percent and 0.12mol) at the constant reaction temperature of 10 ℃, wherein the dropping speed of a brominating agent is 3.0mL/min, the dropping speed of an oxidizing agent is 0.5mL/min, and the reaction temperature can be strictly controlled below 10 ℃ in the dropping process; reacting for 6 hours at the temperature of 10 ℃, and stopping the reaction when the conversion rate of the N-phenylcarbazole is more than or equal to 99% by liquid phase detection. Adding a certain amount of saturated aqueous solution of sodium carbonate into the reaction system after the reaction is finished to adjust the pH of the mixed solution to be neutral, washing for 3 times by adopting a water washing separation method, removing carbon disulfide by rotary evaporation to obtain a crude product, recrystallizing the crude product with 100mL of ethanol for three times to obtain a white solid, transferring the white solid into a vacuum drying oven at 60 ℃ and PTrueDrying under the condition of 0.095MPa for 3 hours to obtain 24.1g of white crystalline 3-bromo-N-phenylcarbazole (the content is more than or equal to 99% by HPLC), and the yield is 74.8%.
The method for removing sodium ions in the reaction system comprises the following steps: after the reaction is finished, the reaction solution is neutralized to be neutral, and sodium ions are separated and removed in the inorganic phase through multiple times of extraction and liquid separation.
In the synthesis reaction of this example, oxygen is generated during the process of dissolving sodium peroxide in water, and a part of the oxidant escapes to the air in the form of oxygen, so that the generated active bromine molecules are reduced, resulting in a decrease in the yield of 3-bromo-N-phenylcarbazole.
It is noted that the brominating agent may also be selected from other bromine-containing compounds, including but not limited to ammonium bromide, lithium bromide; the oxidizing agent may also be selected from other peroxides including, but not limited to, magnesium peroxide; except that the salt ion treatment was different.
Comparative example 1
Adding 24.3g N-phenylcarbazole (99 percent, 0.10mol) and 50mL tetrahydrofuran into a 250mL four-neck round-bottom flask provided with a stirrer and a thermometer at room temperature, stirring until the phenylcarbazole and the tetrahydrofuran are completely dissolved, and then reducing the temperature of a reaction system to-10 ℃; dropwise adding 24.3g of hydrobromic acid (40%, 0.12mol and 17.6mL), dropwise adding 13.6g of hydrogen peroxide (30%, 0.12mol and 12.2mL) at the reaction temperature of-10 ℃ when the reaction temperature is constant, and strictly controlling the reaction temperature below-10 ℃ in the dropwise adding process; reacting for 6 hours at the temperature of minus 10 ℃, and stopping the reaction when the conversion rate of the N-phenylcarbazole is more than or equal to 99% by liquid phase detection. Adding quantitative saturated sodium carbonate solution into the reaction system after the reaction is finished to adjust the pH of the mixed solution to be neutral, washing for 3 times by adopting a water washing separation method, removing tetrahydrofuran by rotary evaporation to obtain a crude product, recrystallizing the crude product with 100mL of ethanol for three times to obtain a white solid, transferring the white solid into a vacuum drying oven at 60 ℃ and PTrueDrying under the condition of 0.095MPa for 3 hours to obtain 17.8g of white crystalline 3-bromo-N-phenylcarbazole (the content is more than or equal to 99% by HPLC), and the yield is 55.2%.
Comparative example 1 Using tetrahydrofuran as a solvent, N-phenylcarbazole was good in solubility, Br+The solvation rate of the ions is high, the conversion rate of the reaction is high, but the selectivity of the reaction is poor.
Comparative example 2
24.3g N-phenylcarbazole (99%, 0.10mol) and 50mL of dichloromethane were added to a 250mL four-necked round-bottomed flask equipped with a stirrer and a thermometer at room temperature, stirred to be completely dissolved, and 24.3g of hydrobromic acid (40%, 0.12mol, 17.6 g) was added dropwisemL), after the reaction temperature is constant, 13.6g of hydrogen peroxide (30%, 0.12mol, 12.2mL) is added dropwise, and the reaction is stopped after 6 hours of reaction at room temperature. Adding a certain amount of saturated aqueous solution of sodium carbonate into the reaction system after the reaction is finished to adjust the pH of the mixed solution to be neutral, washing for 3 times by adopting a water washing separation method, removing dichloromethane by rotary evaporation to obtain a crude product, recrystallizing the crude product with 100mL of ethanol for three times to obtain a white solid, transferring the white solid into a vacuum drying oven at 60 ℃ and PTrueDrying under the condition of 0.095MPa for 3 hours to obtain 12.8g of white crystalline 3-bromo-N-phenylcarbazole (the content is more than or equal to 99% by HPLC), and the yield is 39.7%.
Comparative example 2 adopts dichloromethane as solvent, under room temperature condition, bromination selectivity of N-phenylcarbazole can not be controlled, more than 25% of N-phenylcarbazole generates 3, 6-dibromo-N-phenylcarbazole, N-phenylcarbazole has a small amount of residue (about 5%), separation is difficult, and finally the obtained HPLC detection content is more than or equal to 99%, and the product yield is low.
Comparative example 3
Adding 24.3g N-phenylcarbazole (99 percent, 0.10mol) and 50mL of dichloromethane into a 250mL four-neck round-bottom flask provided with a stirrer and a thermometer at room temperature, stirring until the materials are completely dissolved, and then reducing the temperature of a reaction system to-10 ℃; 47.9g of liquid bromine (40 percent, 0.12mol) is added dropwise, the dropping speed of the liquid bromine is 0.5mL/min when the reaction temperature is constant at minus 10 ℃, and the reaction temperature can be strictly controlled below minus 10 ℃ in the dropping process; the reaction was stopped at-10 ℃ for 6 hours. After the reaction is finished, adding a quantitative saturated aqueous solution of sodium carbonate into a reaction system to adjust the pH of the mixed solution to be neutral, washing for 3 times by adopting a water washing separation method, removing dichloromethane by rotary evaporation to obtain a crude product, recrystallizing the crude product with 100mL of ethanol for three times to obtain a white solid, and drying the white solid in a vacuum drying oven for 3 hours under the conditions of 60 ℃ and Pitrue ═ 0.095MPa to obtain 8.5g (the content is more than or equal to 99 percent by HPLC) of white crystalline 3-bromo-N-phenylcarbazole, wherein the yield is 26.4 percent.
The comparative example adopts dichloromethane as solvent, liquid bromine with the mass fraction of 40 percent is used as bromine source under the condition of-10 ℃, the reaction selectivity is poor, only half of the bromine of the liquid bromine is utilized, the conversion rate of the N-phenylcarbazole is only about 78 percent, the utilization rate of bromine atoms is low, and the reaction conversion rate is low.
Comparative example 4
Adding 24.3g N-phenylcarbazole (99 percent, 0.10mol) and 50mL of dichloromethane into a 250mL four-neck round-bottom flask provided with a stirrer and a thermometer at room temperature, stirring until the materials are completely dissolved, and then reducing the temperature of a reaction system to-10 ℃; evenly adding 12.3g of sodium bromide solid (99 percent, 0.12mol) for three times, evenly adding 9.4g of sodium peroxide solid (99 percent, 0.12mol) for five times when the reaction temperature is constant at minus 10 ℃, wherein the reaction temperature can be strictly controlled below minus 10 ℃ in the adding process; reacting at-10 deg.C, and stopping reaction when the conversion rate of N-phenylcarbazole is more than or equal to 99%. Adding a certain amount of saturated aqueous solution of sodium carbonate into the reaction system after the reaction is finished to adjust the pH of the mixed solution to be neutral, washing for 3 times by adopting a water washing separation method, removing dichloromethane by rotary evaporation to obtain a crude product, recrystallizing the crude product with 100mL of ethanol for three times to obtain a white solid, transferring the white solid into a vacuum drying oven at 60 ℃ and PTrueDrying under the condition of 0.095MPa for 3 hours to obtain 13.6g of white crystalline 3-bromo-N-phenylcarbazole (the content is more than or equal to 99% by HPLC), and the yield is 42.2%.
Comparative example 4 adopts dichloromethane as solvent, under-10 deg.C, sodium bromide as brominating agent, sodium peroxide as oxidant, the two are poor in solubility in dichloromethane, the reaction time is long, the temperature of the sodium peroxide addition process and the bromination reaction process is greatly increased, the control is not easy, and the final yield is low.
Comparative example 5
Adding 24.3g N-phenylcarbazole (99 percent, 0.10mol) and 50mL of dichloromethane into a 250mL four-neck round-bottom flask provided with a stirrer and a thermometer at room temperature, stirring until the materials are completely dissolved, and then reducing the temperature of a reaction system to-10 ℃; dropwise adding 24.3g of hydrobromic acid (40%, 0.12mol, 17.6mL), wherein the dropping speed of the hydrobromic acid is 3.0mL/min, and the reaction temperature can be strictly controlled below-10 ℃ in the dropping process; reacting for 6 hours at the temperature of-10 ℃, and detecting the conversion rate of the N-phenylcarbazole in a liquid phase.
Comparative example 5 adopts dichloromethane as solvent, under the condition of-10 ℃, hydrobromic acid is used as brominating agent, no oxidant is added, only a small amount of N-phenylcarbazole is brominated to generate 3-bromo-N-phenylcarbazole (about 7%), the reaction conversion rate cannot be improved by prolonging the reaction time, and the results prove that the hydrobromic acid is partially oxidized into bromine molecules, and the reaction conversion rate cannot reach more than or equal to 99% without adding the oxidant.
The method for synthesizing 3-bromine-N-phenylcarbazole through oxidation bromination reaction, which is used as a specific example of the green development trend of organic synthesis reaction, effectively overcomes the defects of low utilization rate of bromine atoms, poor regioselectivity, more three wastes, high requirements on production equipment and the like in the traditional method, and provides a bromination method which is cheap, environment-friendly, economical, high in utilization rate of bromine atoms and simple to operate for synthesizing 3-bromine-N-phenylcarbazole.
The invention is not limited to the embodiments of the invention described. The structure and the implementation of the present invention are explained by using the specific embodiments, and the above description of the embodiments is only used to help understand the core idea of the present invention. It should be noted that, for those skilled in the art, it is possible to make various improvements and modifications to the present invention without departing from the principle of the present invention, and those improvements and modifications also fall within the scope of the claims of the present invention.
Claims (7)
1. A method for synthesizing high-purity 3-bromine-N-phenylcarbazole is characterized in that: the method comprises the following steps: dissolving N-phenylcarbazole in a solvent, sequentially adding a brominating agent and an oxidant at the low temperature of-20-10 ℃, and after the adding is finished, keeping the reaction temperature at-20-10 ℃ until the conversion rate of the N-phenylcarbazole reaches more than or equal to 99%, and stopping the reaction, wherein the solvent is dichloromethane, the brominating agent is hydrobromic acid, potassium bromide, sodium bromide, ammonium bromide or lithium bromide, and the oxidant is hydrogen peroxide; keeping the temperature change of the reaction system within 5 ℃ when adding a brominating agent and an oxidant; after the reaction is finished, the reaction system is sequentially subjected to pH adjustment to be neutral, washing, rotary evaporation, recrystallization and vacuum drying to obtain the high-purity 3-bromine-N-phenylcarbazole.
2. The method of claim 1, wherein the synthesis of high purity 3-bromo-N-phenylcarbazole comprises: the mass fraction of the brominating agent is 20-50%.
3. The method of claim 1, wherein the synthesis of high purity 3-bromo-N-phenylcarbazole comprises: the mass fraction of the oxidant is 20-40%.
4. The method for synthesizing high-purity 3-bromo-N-phenylcarbazole according to any one of claims 1 to 3, wherein: the brominating agent is dropwise added in a titration mode, and the titration speed is 1-5 mL/min.
5. The method of claim 4, wherein the synthesis of high purity 3-bromo-N-phenylcarbazole comprises: the oxidant is dropwise added in a titration mode, and the titration speed is 0.5-1.5 mL/min.
6. The method of claim 5, wherein the synthesis of high purity 3-bromo-N-phenylcarbazole comprises: the mol ratio of the brominating agent to the oxidant to the N-phenylcarbazole is (1.00-1.20): 1.05-1.25): 1.
7. The method of claim 1, wherein the synthesis of high purity 3-bromo-N-phenylcarbazole comprises: in the recrystallization process, one or more of n-hexane, ethanol, methanol, xylene, ethyl acetate and the like are mixed to be used as a recrystallization solvent.
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