Novel method for synthesizing p-trifluoromethylaniline through p-chloro trifluorotoluidine

Abstract

The invention relates to a novel method for synthesizing p-trifluoromethylaniline from p-chlorotrifluoromethylaniline, and relates to the technical field of organic synthesis.The method comprises the following steps that arylamine is dispersed into a solvent, oxalyl chloride and caustic soda liquid are added, standing and layering are conducted after the reaction is finished, and an organic phase is concentrated, crystallized, filtered, washed and dried to obtain an auxiliary catalyst; the method comprises the following steps: dispersing parachlorobenzotrifluoride and a catalyst into a solvent, adding an auxiliary catalyst, sealing, introducing liquid ammonia, heating, carrying out an amination reaction, after the reaction is finished, releasing pressure to release excessive ammonia gas to obtain a product mixture, carrying out rotary evaporation on the product mixture to obtain a steamed material and a residual material, and carrying out reduced pressure rectification on the steamed material to obtain the parachlorobenzotrifluoride. The p-trifluoromethylaniline is obtained; and adding water into the residual material, stirring, and filtering, wherein filter cakes are the auxiliary catalyst and the catalyst. The method has the effects of improving the yield of p-trifluoromethylaniline and the recovery rate of the catalyst, and has good industrial application value.

Description

Technical Field

[0001] The present application relates to the technical field of organic synthesis, and in particular to a new method for synthesizing p-trifluoromethylaniline from p-chlorotrifluorotoluidine. Background Art

[0002] p-Trifluoromethylaniline is an important organic compound widely used in pesticides, pharmaceuticals, and new materials. In the pesticide field, p-trifluoromethylaniline serves as a key intermediate in the synthesis of highly effective pesticides such as fipronil and fluvalinate. In the pharmaceutical field, it can be used to prepare important drugs such as leflunomide and teriflunomide. Furthermore, in the field of new materials, p-trifluoromethylaniline can be used to synthesize high-performance liquid crystal materials. Given its wide range of applications and importance, the development of efficient and environmentally friendly methods for the synthesis of p-trifluoromethylaniline is of great significance.

[0003] Currently, the synthesis of p-trifluoromethylaniline primarily involves various routes, including the p-nitrotoluene method, the p-chlorobenzotrifluoride method, the p-methylaniline method, the aniline trifluoromethylation method, and the p-nitrobenzoic acid method. While the p-nitrotoluene method utilizes readily available raw materials, it is complex and produces a significant amount of waste. The p-methylaniline method is difficult to commercialize due to its cumbersome operation and demanding conditions. While the aniline trifluoromethylation method can produce the target product, it suffers from low conversion rates and high costs. The p-nitrobenzoic acid method also suffers from waste and difficulty separating byproducts. In contrast, the p-chlorobenzotrifluoride method is widely used due to its readily available raw materials and simplified process.

[0004] However, existing synthesis methods using parachlorobenzotrifluoride as a raw material still have significant shortcomings. Although this method has a relatively short process flow, the reaction conversion rate is low. Furthermore, the catalyst dosage is large, and the catalyst is difficult to reuse after the reaction, resulting in waste of resources and exacerbated environmental pollution. Therefore, how to improve the reaction conversion rate and achieve catalyst recycling has become an urgent problem to be solved. Summary of the Invention

[0005] In order to improve the reaction conversion rate and realize the recycling of the catalyst, the present application provides a new method for synthesizing p-trifluoromethylaniline from p-chlorotrifluorotoluidine.

[0006] The present application provides a novel method for synthesizing p-trifluoromethylaniline from p-chlorotrifluorotoluidine using the following technical solution: A new method for synthesizing p-trifluoromethylaniline from p-chlorotrifluorotoluidine comprises the following steps: (1) dispersing aromatic amine in a solvent, adding oxalyl chloride and liquid alkali, and allowing the reaction to stand for stratification after completion. The organic phase is concentrated, crystallized, filtered, washed, and dried to obtain a cocatalyst; (2) dispersing parachlorobenzotrifluoride and the catalyst in a solvent, adding the auxiliary catalyst prepared in step (1), introducing liquid ammonia after sealing, raising the temperature, and performing an amination reaction at 120-200° C. After the reaction is completed, depressurizing to release excess ammonia to obtain a product mixture, rotary distilling the product mixture to obtain a distilled material and a remaining material, and performing vacuum distillation on the distilled material to obtain para-trifluoromethylaniline; (3) adding water to the remaining material in step (2), stirring, and filtering; the filter cake is the auxiliary catalyst and catalyst, which can be recycled.

[0007] Preferably, the solvent in step (1) comprises one or more of ethyl acetate, dichloroethane, and dichloromethane; Preferably, the solvent in step (2) comprises one or more of ethanol, methanol, acetonitrile, and tetrahydrofuran; Preferably, the catalyst in step (2) comprises cuprous chloride and potassium fluoride.

[0008] By introducing an auxiliary catalyst to form a composite catalytic system with cuprous chloride and potassium fluoride catalysts, and utilizing the nitrogen-containing ligand generated by the reaction of aromatic amine and oxalyl chloride to form a coordination complex with copper salt, the active site density of the 4-chlorotrifluorotoluene amination reaction is increased, the reaction activation energy is reduced, and thus the yield of 4-trifluoromethylaniline is increased; by optimizing the recovery conditions and utilizing the solubility properties of the auxiliary catalyst and the catalyst, efficient recovery of the auxiliary catalyst and cuprous chloride in the solid filter cake is achieved, avoiding the cost waste and environmental pollution problems caused by the one-time use of the catalyst in the traditional process; by combining the catalytic synergistic effect with the directional separation technology, this method not only improves the yield of the target product but also constructs a green synthesis path for catalyst recycling, and has good industrial application value.

[0009] Preferably, the aromatic amine in step (1) includes one or more of aminopyridine, aminopyrazole, aminopyrazine, and aminopyrrole.

[0010] The types of aromatic amines are limited to aminopyridine, aminopyrazole, aminopyrazine, aminopyrrole and their combinations, and a highly active composite catalytic center is constructed by utilizing the lone pair electrons of the nitrogen atom in the heterocyclic amine compounds to form a strong coordination effect with cuprous chloride. Among them, the conjugated structure of the pyridine ring can enhance the efficiency of electron transfer, the dinitrogen atom coordination mode of the pyrazole and pyrazine rings can improve the stability of the complex, and the electron-rich characteristics of the pyrrole ring optimize the activation ability of the chlorine atom in para-chlorotrifluorotoluene. These structures enable the auxiliary catalyst to regulate the coordination strength and steric hindrance, adapt to different reaction conditions, and thus significantly improve the universality of the amination reaction and the yield of the target product. At the same time, the rigid structure of the heterocyclic amine auxiliary catalyst reduces its swelling loss in polar solvents. Combined with the recovery process, the recovery rate of the auxiliary catalyst can be improved, providing a structural basis for the efficient recycling of catalysts in industrial production.

[0011] Preferably, the aromatic amine includes one of 2-aminopyridine, 3-aminopyridine, 4-aminopyridine, 2-aminopyrazine and 3-aminopyrazine.

[0012] The aromatic amine is further limited to one of 2-aminopyridine, 3-aminopyridine, 4-aminopyridine, 2-aminopyrazine and 3-aminopyrazine. By precisely controlling the nitrogen atom substitution position and electron distribution of the heterocyclic amine, the coordination ability and reaction selectivity of the auxiliary catalyst are optimized; among them, the ortho nitrogen atom of 2-aminopyridine can form a five-membered ring chelate with cuprous chloride, significantly enhancing the stability of the catalytic active center; the meta nitrogen atom of 3-aminopyridine reduces steric hindrance by extending the coordination distance, making it suitable for the amination of substrates with large steric hindrance; the para nitrogen atom of 4-aminopyridine enhances the electron delocalization ability through the conjugation effect, accelerating the amination of the chlorine atom Nucleophilic substitution; the dinitrogen conjugated system of 2-aminopyrazine and 3-aminopyrazine can form a double-bridged coordination mode, strengthening the adsorption of fluoride ions in potassium fluoride and synergistically promoting the activation of C-Cl bonds; this structural design gives the auxiliary catalyst good thermal stability within the amination reaction temperature range, reducing the activity decay of traditional catalysts caused by high-temperature decomposition, thereby improving the catalytic efficiency and the yield of trifluoromethylaniline; the rigid structure of the heterocyclic skeleton makes the auxiliary catalyst less likely to hydrolyze or fragment during the recovery process. Combined with the recovery process, it can improve the catalyst recovery rate, enhance the recycling efficiency of the catalytic system and improve the process stability.

[0013] Preferably, the ortho position of the amino group of the aromatic amine contains one of a C1-C2 alkyl group and a C1-C2 alkoxy group.

[0014] By introducing a C1-C2 alkyl or alkoxy group at the ortho position of the aromatic amine amino group, such as the 6-position of the 2-amino group of the pyridine ring, the 2 / 4-position of the 3-amino group, or the 6-position of the 2-amino group of the pyrazine ring, the electron-donating effect of the substituent is utilized to enhance the coordination ability of the aromatic amine nitrogen atom with cuprous chloride, thereby forming a more stable chelate complex, thereby improving the activation efficiency of the C-Cl bond in para-chlorotrifluorotoluene, and further improving the yield of para-trifluoromethylaniline; the steric hindrance effect of the substituent optimizes the spatial configuration of the catalytic center, inhibits side reactions and improves product selectivity; the hydrophobicity of the substituent reduces the dissolution loss of the auxiliary catalyst in the aqueous phase, and combined with the recovery process, the recovery rate of the catalyst is improved, thereby achieving synergistic optimization of catalytic activity, product selectivity and circulation efficiency.

[0015] Preferably, the molar ratio of aromatic amine to oxalyl chloride in step (1) is (1.5-2.5):1.

[0016] When the auxiliary catalyst is prepared according to the above molar ratio, the two acyl chloride groups of oxalyl chloride can fully undergo acylation reaction with aromatic amine, forming a stable auxiliary catalyst structure, and achieving a good balance between the yield and quality of the auxiliary catalyst. The generated high-quality auxiliary catalyst can form an efficient composite catalytic system with cuprous chloride and potassium fluoride, enhance the activation of the C-Cl bond in para-chlorobenzotrifluoride, improve the activity and selectivity of the amination reaction, and thus increase the yield of para-trifluoromethylaniline. At the same time, the suitable auxiliary catalyst structure and performance also facilitate the efficient recovery of the catalyst and the auxiliary catalyst.

[0017] Preferably, the mass ratio of parachlorotrifluorotoluene, catalyst and auxiliary catalyst in step (2) is 100:(1-10):(0.5-5).

[0018] Preferably, the mass ratio of parachlorotrifluorotoluene, catalyst and auxiliary catalyst in step (2) is 100:(3-4):(4-5).

[0019] Carrying out the amination reaction according to the above ratio can ensure sufficient active sites to activate the C-Cl bond of para-chlorotrifluorotoluene while avoiding catalyst aggregation and deactivation. At the same time, the nitrogen-containing ligand of the auxiliary catalyst and the copper ion form a stable coordination structure through an appropriate ratio, which improves the reaction activity and product selectivity of the catalytic system and facilitates subsequent recovery and separation, achieving a synergistic improvement in catalytic efficiency and circular economy.

[0020] Preferably, the conditions for the amination reaction in step (2) are: reaction at 120-140° C. for 1.5-2.5 h, reaction at 150-170° C. for 3.5-4.5 h, and reaction at 170-190° C. for 1.5-2.5 h.

[0021] The staged temperature-controlled reaction process achieves multiple optimizations by matching the activity of the catalytic system with the reaction progress in stages: in the low-temperature stage, the auxiliary catalyst gradually forms a stable coordination complex with cuprous chloride and potassium fluoride, gently activating the C-Cl bond of para-chlorotrifluorotoluene while avoiding violent vaporization of liquid ammonia and inhibiting the formation of by-products such as diamines; in the medium-temperature stage, the activity of the complex is maximized, accelerating the nucleophilic substitution reaction of ammonia and promoting substrate conversion; the high-temperature stage promotes deep conversion of residual substrates and promotes decomplexation of the catalyst and product, causing the auxiliary catalyst to fall off the copper center, improving the catalyst separation efficiency in the recovery step; the staged temperature-controlled strategy improves the yield and selectivity of the target product and the catalyst recycling performance by dynamically balancing reaction kinetics and thermodynamics.

[0022] Preferably, after adding water in step (3), sodium chloride and glacial acetic acid are added to obtain a mixed solution; the mixed solution is ultrasonicated for 8-12 minutes, stirred at a speed of 200-300 rpm for 10-15 minutes, filtered, washed, and dried to obtain a filter cake.

[0023] Sodium chloride reduces the solubility of the auxiliary catalyst in water through salting out, promoting its efficient precipitation; glacial acetic acid adjusts the pH to weak acidity, stabilizes the precipitation form of cuprous chloride and inhibits the hydrolysis of the auxiliary catalyst. The two work together to improve the recovery rate of the catalyst and optimize the recycling performance of the catalytic system.

[0024] Preferably, the concentration of sodium chloride in the mixed solution is 0.5-1 mol / L, and the pH is 4-5.

[0025] A sodium ion concentration of 0.5-1 mol / L can produce a significant salting-out effect, which reduces the solubility of the auxiliary catalyst in water by compressing the double electrical layer on the surface of the auxiliary catalyst, prompting it to precipitate in the form of complete crystals. A weakly acidic environment can inhibit the hydrolysis of cuprous chloride, allowing it to exist in a stable solid state, while preventing the amide bond of the auxiliary catalyst from breaking under strongly acidic conditions. This pH range can also enhance the positive charge of the nitrogen atom of the auxiliary catalyst through protonation, making its coordination bond with the copper ion easier to break, facilitating its dissociation and recovery from the complex. The appropriate salt concentration and pH value work together to improve the recovery rate of the auxiliary catalyst.

[0026] In summary, this application includes at least one of the following beneficial technical effects: 1. By introducing an auxiliary catalyst to form a composite catalytic system with cuprous chloride and potassium fluoride catalysts, the nitrogen-containing ligand generated by the reaction of aromatic amine and oxalyl chloride forms a coordination complex with copper salt, thereby increasing the active site density of the 4-chlorotrifluorotoluene amination reaction and reducing the reaction activation energy, thereby increasing the yield of 4-trifluoromethylaniline; by optimizing the recovery conditions and utilizing the solubility properties of the auxiliary catalyst and the catalyst, efficient recovery of the auxiliary catalyst and cuprous chloride in the solid filter cake is achieved, avoiding the cost waste and environmental pollution problems caused by the one-time use of the catalyst in the traditional process; this method combines catalytic synergistic effects with directional separation technology, while increasing the yield of the target product, constructing a green synthesis path for catalyst recycling, and has good industrial application value.

[0027] 2. By introducing a C1-C2 alkyl or alkoxy group at the ortho position of the aromatic amine amino group, such as the 6-position of the 2-amino group on the pyridine ring, the 2 / 4-position of the 3-amino group, or the 6-position of the 2-amino group on the pyrazine ring, the electron-donating effect of the substituent is utilized to enhance the coordination ability of the aromatic amine nitrogen atom with cuprous chloride, forming a more stable chelate complex, thereby improving the activation efficiency of the C-Cl bond in para-chlorotrifluorotoluene and, in turn, increasing the yield of para-trifluoromethylaniline. The steric hindrance effect of the substituent optimizes the spatial configuration of the catalytic center, inhibiting side reactions and improving product selectivity. The hydrophobicity of the substituent reduces the dissolution loss of the auxiliary catalyst in the aqueous phase. Combined with the recovery process, the catalyst recovery rate is improved, achieving synergistic optimization of catalytic activity, product selectivity, and cycle efficiency.

[0028] 3. Sodium chloride reduces the solubility of the auxiliary catalyst in water through salting out, promoting its efficient precipitation; glacial acetic acid adjusts the pH to a weakly acidic state, stabilizes the precipitated form of cuprous chloride, and inhibits the hydrolysis of the auxiliary catalyst. The two synergistically improve the catalyst recovery rate and optimize the recycling performance of the catalytic system. DETAILED DESCRIPTION

[0029] The present invention discloses a novel method for synthesizing p-trifluoromethylaniline from p-chlorotrifluorotoluidine. The raw materials used in the present invention can be obtained from commercially available raw materials unless otherwise specified. The present invention is further described in detail below in conjunction with the following examples and comparative examples: Raw materials description: 2-aminopyridine (CAS No.: 504-29-0), oxalyl chloride (CAS No.: 79-37-8), 4-chlorobenzotrifluoride (CAS No.: 98-56-6), 2-aminopyrazine (CAS No.: 5049-61-6), 2-amino-6-methylpyridine (CAS No.: 1824-81-3).

[0030] Example 1 (1) Add 500 mL of dichloroethane and 94.2 g of 2-aminopyridine to a 1000 mL four-necked glass bottle, stir uniformly at 200 rpm, control the system temperature at 0-10° C., add 72.5 g of oxalyl chloride dropwise over 2 h, keep the temperature at 15° C. for 1 h, add 10% sodium hydroxide aqueous solution dropwise until the pH is neutral, keep the temperature for 1 h, let stand for phase separation, collect the organic phase, and evaporate about 250 g of dichloroethane under reduced pressure to concentrate the phase to obtain a concentrated solution, cool the concentrated solution to 10° C. and crystallize to obtain a crystal solution, filter the crystal solution to obtain a filter cake, wash the filter cake with deionized water, and dry it under reduced pressure to obtain a co-catalyst.

[0031] (2) In a 1000 mL autoclave, 300 g of parachlorobenzotrifluoride, 5 g of cuprous chloride and 5 g of potassium fluoride were dispersed in 250 mL of ethanol, 15 g of the auxiliary catalyst prepared in step (1) was added, 120 g of liquid ammonia was introduced after sealing, and the temperature was raised to 150 ° C at a rate of 5 ° C / min to carry out amination reaction, and the temperature was kept for 8 hours. After the reaction was completed, the temperature was lowered to below 30 ° C, and the pressure was released to release excess ammonia to obtain a product mixture. The product mixture was transferred to a rotary evaporator for rotary evaporation to obtain a steamed material and a remaining material, and the steamed material was subjected to vacuum distillation to obtain trifluoromethylaniline.

[0032] (3) Add 200 g of water to the remaining material in the rotary evaporator in step (2), stir and heat to 50° C., then filter, rinse the filter cake with 50° C. hot water once, drain and vacuum dry to obtain a solid mixture.

[0033] Example 2 (1) Add 500 mL of dichloroethane and 95.1 g of 2-aminopyrazine to a 1000 mL four-necked glass bottle, stir evenly at 200 rpm, control the system temperature at 0-5°C, add 72.5 g of oxalyl chloride dropwise over 3 h, keep the temperature at 10°C for 1.5 h, add 10% sodium hydroxide aqueous solution dropwise until the pH is neutral, keep the temperature for 1.5 h, let stand for phase separation, collect the organic phase, and evaporate about 250 g of dichloroethane under reduced pressure to concentrate to obtain a concentrated solution. Cool the concentrated solution to 5°C and crystallize to obtain a crystal solution. Filter the crystal solution to obtain a filter cake. Wash the filter cake with deionized water and dry it under reduced pressure to obtain a co-catalyst.

[0034] (2) In a 1000 mL autoclave, 300 g of parachlorobenzotrifluoride, 5 g of cuprous chloride and 5 g of potassium fluoride were dispersed in 250 mL of ethanol, 15 g of the auxiliary catalyst prepared in step (1) was added, 120 g of liquid ammonia was introduced after sealing, and the temperature was raised to 140 ° C at a rate of 3 ° C / min to carry out amination reaction, and the temperature was kept for 9 hours. After the reaction was completed, the temperature was lowered to below 30 ° C, and the pressure was released to release excess ammonia to obtain a product mixture. The product mixture was transferred to a rotary evaporator for rotary evaporation to obtain a steamed material and a remaining material. The steamed material was subjected to vacuum distillation to obtain trifluoromethylaniline.

[0035] (3) Add 200 g of water to the remaining material in the rotary evaporator in step (2), stir and heat to 45° C., then filter, rinse the filter cake once with 45° C. hot water, drain and vacuum dry to obtain a solid mixture.

[0036] Example 3 (1) Add 500 mL of dichloroethane and 108.14 g of 2-amino-6-methylpyridine to a 1000 mL four-necked glass bottle, stir evenly at 200 rpm, control the system temperature at 0-10°C, add 72.5 g of oxalyl chloride dropwise over 2.5 hours, keep warm at 15°C for 1.5 hours, add 10% sodium hydroxide aqueous solution dropwise until the pH is neutral, keep warm for 1 hour, and allow to stand for phase separation. Collect the organic phase and evaporate about 250 g of dichloroethane under reduced pressure to concentrate to obtain a concentrated solution. Cool the concentrated solution to 10°C and crystallize to obtain a crystal solution. Filter the crystal solution to obtain a filter cake. Wash the filter cake with deionized water and dry it under reduced pressure to obtain a cocatalyst.

[0037] (2) In a 1000 mL autoclave, 300 g of parachlorobenzotrifluoride, 5 g of cuprous chloride and 5 g of potassium fluoride were dispersed in 250 mL of ethanol, 15 g of the auxiliary catalyst prepared in step (1) was added, 120 g of liquid ammonia was introduced after sealing, and the temperature was raised to 155 ° C at a rate of 4 ° C / min to carry out amination reaction, and the temperature was kept for 8.5 hours. After the reaction was completed, the temperature was lowered to below 30 ° C, and the pressure was released to release excess ammonia to obtain a product mixture. The product mixture was transferred to a rotary evaporator for rotary evaporation to obtain a steamed material and a remaining material. The steamed material was subjected to vacuum distillation to obtain trifluoromethylaniline.

[0038] (3) Add 200 g of water to the remaining material in the rotary evaporator in step (2), stir and heat to 50° C., then filter, rinse the filter cake with 50° C. hot water once, drain and vacuum dry to obtain a solid mixture.

[0039] Example 4 Example 4 is based on Example 1. The only difference between Example 4 and Example 1 is that the molar ratio of aromatic amine, i.e., 2-aminopyridine, and oxalyl chloride in Example 4 is 1:1.

[0040] Example 5 Example 5 is based on Example 1. The only difference between Example 5 and Example 1 is that in Example 5, the molar ratio of aromatic amine, 2-aminopyridine, and oxalyl chloride is 3:1.

[0041] Example 6 Example 6 is based on Example 1. The only difference between Example 6 and Example 1 is that in Example 6, the mass ratio of p-chlorobenzotrifluoride, cuprous chloride and auxiliary catalyst is 100:2:6.

[0042] Example 7 Example 7 is based on Example 1. The only difference between Example 7 and Example 1 is that in Example 7, the mass ratio of p-chlorobenzotrifluoride, cuprous chloride and auxiliary catalyst is 100:5:3.

[0043] Example 8 Example 8 is based on Example 1. The only difference between Example 8 and Example 1 is that in Example 8, the conditions of the amination reaction are replaced by reaction at 130° C. for 2 h, reaction at 160° C. for 4 h, and reaction at 180° C. for 2 h.

[0044] Example 9 Example 9 is based on Example 1. The only difference between Example 9 and Example 1 is that after adding 25°C water in step (3) of Example 9, sodium chloride and glacial acetic acid are added to make the concentration of sodium chloride 0.75 mol / L and the pH of the mixed solution 4.5. The mixture is stirred at 250 rpm for 12.5 min, filtered, washed, and dried to obtain a filter cake.

[0045] Example 10 Example 10 is based on Example 9. The only difference between Example 10 and Example 9 is that the concentration of sodium chloride in Example 10 is 2 mol / L and the pH of the mixed solution is 3.

[0046] Comparative Example 1 (1) In a 1000 mL autoclave, 300 g of parachlorobenzotrifluoride, 8 g of cuprous chloride, and 8 g of potassium fluoride were dispersed in 250 mL of ethanol. After sealing, 120 g of liquid ammonia was introduced, and the temperature was raised to 160°C at a rate of 5°C / min to carry out an amination reaction. The temperature was kept for 10 hours. After the reaction was completed, the temperature was lowered to below 30°C, and the pressure was released to release excess ammonia to obtain a product mixture. The product mixture was transferred to a rotary evaporator for rotary evaporation to obtain a distilled material and a residual material. The distilled material was subjected to vacuum distillation to obtain para-trifluoromethylaniline; (2) Add 200 g of water to the remaining material in the rotary evaporator in step (1), stir and heat to 50° C., then filter, rinse the filter cake once with 50° C. hot water, drain and vacuum dry to obtain a solid mixture.

[0047] Performance testing Detection of the yield of trifluoromethylaniline and catalyst recovery: The content of p-trifluoromethylaniline in the product was detected by gas chromatography, and the yield was calculated; the contents of cuprous chloride and auxiliary catalyst in the recovered solid mixture were detected, and the recovery rates of cuprous chloride and auxiliary catalyst were calculated. The results are recorded in Table 1.

[0048] Table 1 Test results of trifluoromethylaniline yield and catalyst recovery As shown in Table 1, the yield of Example 1-2 is greater than 83.22%, the recovery rate of cuprous chloride is greater than 84.72%, and the recovery rate of the auxiliary catalyst is greater than 96.96%, which shows that the synthesis method of the present application has a high yield and a high catalyst recovery rate.

[0049] As shown in Table 1, the yield of Example 3 is 85.84%, the recovery rate of cuprous chloride is 83.89%, and the recovery rate of the auxiliary catalyst is 98.14%. Compared with Example 1, the performance of Example 3 is improved. This is because a methyl group is added to the ortho position of the amino group of the aromatic amine, which improves the catalytic reaction activity, thereby improving the product yield and catalyst recovery rate.

[0050] As can be seen from Table 1, the only difference between Examples 4 and 5 and Example 3 is that the molar ratio of aromatic amine, i.e., 2-aminopyridine, and oxalyl chloride in Example 4 is 1:1, and the molar ratio of aromatic amine, i.e., 2-aminopyridine, and oxalyl chloride in Example 5 is 3:1. Compared with Example 3, the yield and recovery rates of Examples 4 and 5 are reduced. This is because when the proportion of aromatic amine is too low, oxalyl chloride may not react completely, resulting in waste of raw materials and an incomplete structure of the generated auxiliary catalyst, which affects its subsequent synergistic effect with the main catalyst. If the proportion of aromatic amine is too high, the excess aromatic amine may participate in side reactions, generate impurities, and also reduce the quality and performance of the auxiliary catalyst. Therefore, the product yield and catalyst recovery rate are reduced.

[0051] As can be seen from Table 1, the only difference between Examples 6 and 7 and Example 3 is that the mass ratio of p-chlorobenzotrifluoride, cuprous chloride and auxiliary catalyst in Example 6 is 100:2:6, and the mass ratio of p-chlorobenzotrifluoride, cuprous chloride and auxiliary catalyst in Example 7 is 100:5:3. Compared with Example 3, the product yield and catalyst recovery rate of Examples 6 and 7 are reduced. This is because the use ratio of the catalyst is adjusted, and the destruction of the optimal ratio of the catalyst and the auxiliary catalyst will lead to a decrease in activation efficiency and catalytic activity, thereby reducing the product yield and affecting the recovery of the catalyst to a certain extent.

[0052] As can be seen from Table 1, the only difference between Example 8 and Example 3 is that in Example 8, the conditions of the amination reaction are replaced with reaction at 130°C for 2 hours, reaction at 160°C for 4 hours, and reaction at 180°C for 2 hours. Compared with Example 3, the performance of Example 8 is improved; this is because the staged temperature control treatment allows the reaction to proceed more stably and efficiently, thereby improving the preparation efficiency and reducing the generation of by-products.

[0053] As can be seen from Table 1, the only difference between Examples 9 and 10 and Example 3 is that: in Example 9, after adding 25°C water in step (3), sodium chloride and glacial acetic acid are added to make the concentration of sodium chloride 0.75 mol / L and the pH of the mixed solution 4.5, and the mixture is stirred at a speed of 250 rpm for 12.5 min, filtered, washed, and dried to obtain a filter cake. Compared with Example 3, the recovery rate of Example 9 is increased; this is because the recovery conditions are optimized, and the efficiency of solid-liquid separation is improved by salting out effect and charge neutralization, so the recovery rate is increased; in Example 10, the concentration of sodium chloride is 2 mol / L, and the pH of the mixed solution is 3, and the performance of Example 10 is reduced; this is because the optimal range is destroyed, and the strong acidity may cause part of the copper chloride to dissolve, affecting the recovery rate.

[0054] As can be seen from Table 1, the only difference between Comparative Example 1 and Example 3 is that no auxiliary catalyst is added during the synthesis in Comparative Example 1. Compared with Example 3, the product yield in Comparative Example 1 is significantly reduced. This is because without the addition of the auxiliary catalyst, the catalytic activity is significantly reduced, the product yield is seriously affected, and at the same time, cuprous chloride is easily agglomerated, the washing loss increases, and thus the recovery rate is also affected.

[0055] This specific embodiment is merely an explanation of the present application and does not limit the present application. Based on the above description, relevant personnel can make various changes and modifications without departing from the technical scope of the present application. The technical scope of the present application is not limited to the contents of the specification and must be determined according to the scope of the claims.

Claims

1. A novel method for synthesizing p-trifluoromethylaniline from p-chlorotrifluorotoluidine, characterized in that: The following steps are involved: (1) Dispersing aromatic amine in a solvent, adding oxalyl chloride and liquid alkali, allowing the reaction to stand and separate, concentrating, crystallizing, filtering, washing and drying the organic phase to obtain a cocatalyst; (2) dispersing parachlorotrifluorotoluene and the catalyst in a solvent, adding the auxiliary catalyst prepared in step (1), introducing liquid ammonia after sealing, raising the temperature, and carrying out an amination reaction at 120-200°C. After the reaction is completed, the pressure is released to release excess ammonia to obtain a product mixture, and the product mixture is rotary evaporated to obtain a distilled material and a residual material, and the distilled material is subjected to vacuum distillation to obtain para-trifluoromethylaniline; (3) Add water to the remaining material in step (2), stir, and filter. The filter cake is the auxiliary catalyst and catalyst and can be recycled.

2. The novel method for synthesizing p-trifluoromethylaniline from p-chlorotrifluorotoluidine according to claim 1, characterized in that: The aromatic amine in step (1) includes one or more of aminopyridine, aminopyrazole, aminopyrazine, and aminopyrrole.

3. The novel method for synthesizing p-trifluoromethylaniline from p-chlorotrifluorotoluidine according to claim 2, characterized in that: The aromatic amine includes one of 2-aminopyridine, 3-aminopyridine, 4-aminopyridine, 2-aminopyrazine and 3-aminopyrazine.

4. The novel method for synthesizing p-trifluoromethylaniline from p-chlorotrifluorotoluidine according to claim 3, characterized in that: The amino group ortho position of the aromatic amine contains one of a C1-C2 alkyl group and a C1-C2 alkoxy group.

5. The novel method for synthesizing p-trifluoromethylaniline from p-chlorotrifluorotoluidine according to claim 1, characterized in that: The molar ratio of aromatic amine to oxalyl chloride in step (1) is (1.5-2.5):

1.

6. The novel method for synthesizing p-trifluoromethylaniline from p-chlorotrifluorotoluidine according to claim 1, characterized in that: The mass ratio of parachlorotrifluorotoluene, catalyst and auxiliary catalyst in step (2) is 100: (1-10): (0.5-5).

7. The novel method for synthesizing p-trifluoromethylaniline from p-chlorotrifluorotoluidine according to claim 6, characterized in that: The mass ratio of parachlorotrifluorotoluene, catalyst and auxiliary catalyst in step (2) is 100:(3-4):(4-5).

8. The novel method for synthesizing p-trifluoromethylaniline from p-chlorotrifluorotoluidine according to claim 1, characterized in that: The conditions for the amination reaction in step (2) are as follows: reaction at 120-140° C. for 1.5-2.5 h, reaction at 150-170° C. for 3.5-4.5 h, and reaction at 170-190° C. for 1.5-2.5 h.

9. The novel method for synthesizing p-trifluoromethylaniline from p-chlorotrifluorotoluidine according to claim 1, characterized in that: After adding water in step (3), sodium chloride and glacial acetic acid are added to obtain a mixed solution; the mixed solution is ultrasonicated for 8-12 minutes, stirred at a speed of 200-300 rpm for 10-15 minutes, filtered, washed, and dried to obtain a filter cake.

10. The novel method for synthesizing p-trifluoromethylaniline from p-chlorotrifluorotoluidine according to claim 9, characterized in that: The sodium chloride concentration in the mixed solution is 0.5-1 mol / L, and the pH is 4-5.

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