A process for the preparation of 2-trifluoromethyl-4-heptafluoroisopropyl aniline

Abstract

The application provides a preparation method of 2-trifluoromethyl-4-heptafluoroisopropylaniline and relates to the technical field of fluorine-containing organic intermediate preparation. The preparation method uses 2-aminotrifluorotoluene and heptafluorobromopropane as reaction raw materials, uses sodium hyposulfite as an initiator, and realizes the efficient synthesis of 2-trifluoromethyl-4-heptafluoroisopropylaniline by continuously introducing heptafluorobromopropane to control the reaction pressure in the presence of a solvent and an acidic additive. The preparation method of 2-trifluoromethyl-4-heptafluoroisopropylaniline can effectively solve the problems of incomplete reaction of raw materials, difficulty in separation of products, low reaction conversion rate and low product purity in the existing preparation method, can improve the reaction conversion rate, product separation yield and product purity, and effectively inhibit the occurrence of side reactions.

Description

Technical Field

[0001] This invention relates to the field of fluorinated organic intermediate preparation technology, specifically to a method for preparing 2-trifluoromethyl-4-heptafluoroisopropylaniline. Background Technology

[0002] 2-Trifluoromethyl-4-heptafluoroisopropylaniline is an important fluorinated fine chemical, currently mainly used to synthesize brofenoxuron-methyl and cyclopropiconazole. Brofenoxuron-methyl is a novel compound created by Mitsui Chemicals Agriculture; it is a low-toxicity pesticide, without teratogenic, carcinogenic, or mutagenic properties, and exhibits low toxicity to environmental organisms such as birds and earthworms. In March 2018, Mitsui Chemicals' brofenoxuron-methyl was registered in Japan as a soil treatment agent for termite control, and it was launched in Japan in November 2019. The increasing production and application of brofenoxuron-methyl has driven market demand for 2-trifluoromethyl-4-heptafluoroisopropylaniline.

[0003] The production and storage conditions for 2-trifluoromethyl-4-heptafluoroisopropylaniline are extremely demanding, resulting in very few manufacturers worldwide possessing industrial-scale production capabilities. Existing synthetic routes typically use 2-aminotrifluorotoluene and 2-iodoheptafluoropropane as starting materials, reacting them in a two-phase system of sodium dithionite, a phase-transfer catalyst, and a water-organic solvent, followed by post-processing to obtain the target product. However, this process has an overall yield of only about 30%, and the raw material costs are high, resulting in poor overall economic viability and making large-scale industrial production impractical.

[0004] Chinese patent CN114478264A discloses a method for preparing 2-trifluoromethyl-4-heptafluoroisopropylaniline. This method utilizes the synergistic effect of specific amine compounds and a phase transfer catalyst to construct the target molecule via a free radical electrophilic substitution reaction pathway. The core of this patented technology lies in using an amine catalyst to activate halogen bonds, causing perfluoroalkyl halides (such as heptafluorobromopropane) to undergo CX bond cleavage under relatively mild conditions, generating perfluoroalkyl free radicals, which then selectively attack the para-position of the benzene ring of 2-aminotrifluorotoluene. However, this technical solution still has significant technical drawbacks in practical applications: the primary conversion rate and overall yield are relatively low. Based on literature review and feedback from industrialization practice, the inventors found that the overall yield of this method typically remains in the 70-80% range. According to the inventors' analysis, this technical bottleneck is mainly due to two aspects: First, the reaction raw material heptafluorobromopropane has a low boiling point (about 14°C) and is easily volatilized and dispersed during the reaction, resulting in insufficient substrate concentration to effectively participate in the free radical chain reaction; Second, along with the generation of the target product, disubstituted or polymerized byproducts are easily generated in the system, and the unreacted 2-aminotrifluorotoluene is difficult to separate, which complicates the product separation and purification steps.

[0005] To address the shortcomings of existing technologies, Chinese patent CN117623938A discloses a method for preparing high-content 2-trifluoromethyl-4-heptafluoroisopropylaniline. In the presence of dithionite, a solvent, and a catalyst, 2-trifluoromethylaniline reacts with heptafluorobromopropane, followed by post-treatment to obtain high-content 2-trifluoromethyl-4-heptafluoroisopropylaniline. The reaction conversion rate reaches over 96%, the post-treatment steps are few, distillation is unnecessary, and the final product content is over 98%. However, during the preparation process, some raw materials cannot react completely, and the boiling points of the raw materials and products are close, making separation difficult, resulting in a final product purity of approximately 98 wt%. Summary of the Invention

[0006] To address the technical problems existing in the prior art, this invention provides a method for preparing 2-trifluoromethyl-4-heptafluoroisopropylaniline, which effectively solves the problems of incomplete reaction of raw materials, difficulty in product separation, and low reaction conversion rate and product purity in existing preparation methods. It can improve the reaction conversion rate, product separation yield and product purity, and effectively suppress the occurrence of side reactions.

[0007] To solve the above technical problems, the technical solution adopted by the present invention is as follows: A method for preparing 2-trifluoromethyl-4-heptafluoroisopropylaniline includes the following steps: adding solvent, 2-aminotrifluorotoluene, and an acidic auxiliary agent into a reaction vessel, stirring the reaction, adding an initiator, sealing the reaction vessel, completely replacing the air in the reaction vessel with nitrogen, raising the temperature to 60-90°C, and maintaining the temperature; continuously introducing heptafluorobromopropane, and controlling the pressure inside the reaction vessel to 0.5-1.0 MPa by continuously introducing heptafluorobromopropane, maintaining the temperature for the reaction, and then cooling the reaction vessel; condensing and recovering the remaining gas in the reaction vessel to obtain the reaction material; purifying the reaction material to obtain 2-trifluoromethyl-4-heptafluoroisopropylaniline.

[0008] Furthermore, the purification process involves centrifuging the reaction material to remove solids, then desolventizing the centrifuged liquid; after desolventizing, the liquid is centrifuged again to remove solids, and then vacuum dried to obtain 2-trifluoromethyl-4-heptafluoroisopropylaniline.

[0009] Furthermore, the acidic additive is one of the following: sodium bisulfate, sodium bisulfite, sodium dihydrogen phosphate, or phosphoric acid.

[0010] Preferably, the molar ratio of the acidic additive to 2-aminotrifluorotoluene is 0.4~1.2:1.

[0011] Preferably, the solvent is one of the following: ethyl acetate, N,N-dimethylformamide, dimethyl sulfoxide, acetonitrile, or ethylene glycol dimethyl ether.

[0012] Preferably, the molar ratio of the solvent to 2-aminotrifluorotoluene is 3 to 10:1.

[0013] Preferably, the initiator comprises sodium dithionite; The molar ratio of the initiator to 2-aminotrifluorotoluene is 0.7~1.2:1.

[0014] Preferably, the stirring reaction time after adding the solvent, 2-aminotrifluorotoluene, and acidic additive to the reactor is 5-10 minutes.

[0015] Preferably, the heat preservation reaction time is 2-8 hours; After the heat treatment reaction, the temperature is lowered to 30~50℃.

[0016] Preferably, the condensation temperature in the residual gas in the condensation recovery reactor is controlled to be between -10°C and 0°C.

[0017] Compared with the prior art, the beneficial effects of the present invention are as follows: (1) The low primary conversion rate of 2-aminotrifluorotoluene in the prior art is mainly due to the low activity of 2-aminotrifluorotoluene and the low solubility of sodium dithionite in organic solvents, which together result in the incomplete reaction of the raw material 2-aminotrifluorotoluene. Moreover, the boiling points of the raw material 2-aminotrifluorotoluene and the product are high, resulting in high energy consumption for distillation separation. If separation is carried out by vacuum distillation alone, the product purity will be poor and the distillation energy consumption will be high. In view of the above-mentioned defects, the preparation method of 2-trifluoromethyl-4-heptafluoroisopropylaniline of the present invention first reacts 2-aminotrifluorotoluene with an acidic auxiliary agent for a period of time in a solvent environment to generate 2-aminotrifluorotoluene salt. This process introduces additional steric hindrance at the ortho position of the amino group, which can effectively inhibit the generation of ortho-substituted byproducts and improve product selectivity. On the other hand, it can avoid the decomposition reaction caused by direct contact between sodium dithionite (initiator) and acidic auxiliary agent, thereby preventing the reaction failure caused by initiator deactivation.

[0018] Furthermore, after the reaction of 2-aminotrifluorotoluene with an acidic auxiliary agent, sodium dithionite is added, and heptafluorobromopropane is continuously introduced while the pressure is controlled at a predetermined level. By increasing the pressure, the solubility of heptafluorobromopropane in the solvent is increased, thereby improving the contact probability of the gas-liquid-solid three phases and thus increasing the conversion rate of 2-aminotrifluorotoluene (from 96% in the prior art to 99.9%). This avoids the subsequent problem of separating the residual 2-aminotrifluorotoluene from the product, simplifies the separation process, reduces separation energy consumption, and achieves a product purity of 99.89% with a product separation molar yield of 96.1~97.4%.

[0019] (2) This invention adds a condenser 6 and a storage tank 7 above the high-pressure reactor. By condensing the remaining gas in the reactor after the reaction is completed, excess heptafluorobromopropane and a small amount of solvent are collected and reused in the next batch of feed, thus realizing the recycling of heptafluorobromopropane. Given the current high price of heptafluorobromopropane, its recycling can significantly improve the economic efficiency of the reaction. It effectively overcomes the difficulties in recovering heptafluorobromopropane and the environmental pollution and economic losses caused by directly venting excess heptafluorobromopropane in the existing technology.

[0020] (3) The preparation method of 2-trifluoromethyl-4-heptafluoroisopropylaniline of the present invention has a simple process flow, the preparation process is easy to control, and the post-processing operations such as purification are simple, the separation energy consumption is low, and it is conducive to industrial-scale production and application. Attached Figure Description

[0021] Figure 1 This is a process flow diagram for preparing 2-trifluoromethyl-4-heptafluoroisopropylaniline in an embodiment of the present invention; in the diagram, 1-heptafluorobromopropane gas source, 2-heptafluorobromopropane regulating valve, 3-nitrogen cylinder, 4-nitrogen regulating valve, 5-high pressure reactor, 6-condenser, 7-storage tank, 8-discharge valve, 9-centrifuge, 10-rotary evaporator, 11-vacuum drying oven.

[0022] Figure 2 This is the gas phase purity spectrum of the product from Example 1.

[0023] Figure 3 The image shows the gas phase purity spectrum of the product in Comparative Example 1. Detailed Implementation

[0024] To provide a clearer understanding of the technical features, objectives, and effects of this invention, specific embodiments are now described. It should be noted that the following detailed descriptions are exemplary and intended to provide further explanation of the invention. Unless otherwise specified, all technical and scientific terms used in this invention have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains.

[0025] It should be noted that the terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit the exemplary embodiments of the present invention. As used herein, "first," "second," etc., are used to distinguish similar objects and are not used to describe a particular order or sequence. Furthermore, it should be understood that when the terms "comprising" and / or "including" are used in this specification, they indicate the presence of features, steps, operations, devices, components, and / or combinations thereof.

[0026] like Figure 1As shown, this embodiment of the invention provides a method for preparing 2-trifluoromethyl-4-heptafluoroisopropylaniline. First, the various devices are connected to form a reaction system: a heptafluorobromopropane gas source 1 is connected to a high-pressure reactor 5 via a pressure gauge and a heptafluorobromopropane regulating valve 2; the outlet of a nitrogen cylinder 3 is connected to the high-pressure reactor 5 via a nitrogen regulating valve 4; the top outlet of the high-pressure reactor 5 is connected to a condenser 6 and a storage tank 7 via an outlet valve; the bottom outlet of the storage tank 7 is connected to the top reflux outlet of the high-pressure reactor 5 via a reflux valve; the material outlet at the bottom of the high-pressure reactor 5 is connected to the inlet of a centrifuge 9 via a discharge valve 8; the liquid outlet of the centrifuge 9 is connected to a rotary evaporator 10 and a vacuum drying oven 11; the reflux outlet of the rotary evaporator 10 is connected to the inlet of the centrifuge 9.

[0027] The preparation of 2-trifluoromethyl-4-heptafluoroisopropylaniline using the above reaction system includes the following steps: Add solvent, 2-aminotrifluorotoluene, and acidic additive to a high-pressure reactor 5. After stirring, add an initiator, seal the high-pressure reactor 5, open the nitrogen regulating valve 4, and purge with nitrogen 3-4 times. Then close the nitrogen regulating valve 4, raise the temperature to 60-90℃, and maintain the temperature. Open the heptafluorobromopropane regulating valve 2, continuously introduce heptafluorobromopropane, and control the pressure of the high-pressure reactor 5 at 0.5-1.0 MPa. After maintaining the temperature, lower the temperature to 30-50℃, close the heptafluorobromopropane regulating valve 2, open the outlet valve, and control the condenser. 6. At a temperature of -10℃ to 0℃, excess gas is condensed and recovered to storage tank 7 until the pressure inside the reactor becomes atmospheric pressure. Then, the gas outlet valve is closed. The heptafluorobromopropane and a small amount of solvent condensed and recovered in storage tank 7 are reused in the next batch of feed. The discharge valve 8 is opened, and the reaction material enters centrifuge 9 for centrifugation. The centrifuged solids are collected and processed externally, while the centrifuged liquid is introduced into rotary evaporator 10 for solvent removal. The solvent is collected and recycled. The liquid product after solvent removal (i.e., crude product) is centrifuged again in centrifuge 9 to remove solids. Then, it is vacuum dried to remove the small amount of residual solvent in the liquid product, yielding 2-trifluoromethyl-4-heptafluoroisopropylaniline product.

[0028] In this embodiment of the invention, 2-aminotrifluorotoluene reacts with an acidic auxiliary agent in a solvent environment for a period of time to generate 2-aminotrifluorotoluene salt. This process introduces additional steric hindrance at the ortho-amino position, which on the one hand effectively inhibits the formation of ortho-substituted byproducts and improves product selectivity; on the other hand, it avoids the subsequent decomposition reaction between sodium dithionite (initiator) and the acidic auxiliary agent, thus preventing reaction failure due to initiator deactivation. Then, the initiator is added, and heptafluorobromopropane is continuously introduced while the pressure is controlled at a predetermined level. By increasing the pressure, the solubility of heptafluorobromopropane in the solvent is increased, improving the contact probability of the gas-liquid-solid three phases, thereby increasing the conversion rate of 2-aminotrifluorotoluene. This avoids the subsequent separation problem of residual 2-aminotrifluorotoluene from the product, simplifies the separation process, reduces separation energy consumption, and improves product purity and yield.

[0029] According to some embodiments of the present invention, the solvent is one of the following: ethyl acetate, N,N-dimethylformamide, dimethyl sulfoxide, acetonitrile, ethylene glycol dimethyl ether; the molar ratio of the solvent to 2-aminotrifluorotoluene is 3 to 10:1; for example, it can be 3:1, 4:1, 5:1, 6:1, 7:1, 8:1, 9:1, 10:1 or any range between the above values.

[0030] According to some embodiments of the present invention, the acidic additive is one of the following: sodium bisulfate, sodium bisulfite, sodium dihydrogen phosphate, or phosphoric acid; the molar ratio of the acidic additive to 2-aminotrifluorotoluene is 0.4 to 1.2:1; for example, it can be 0.4:1, 0.5:1, 0.6:1, 0.7:1, 0.8:1, 0.9:1, 1.0:1, 1.1:1, 1.2:1, or any range between the above values.

[0031] According to some embodiments of the present invention, the initiator comprises sodium dithionite; the molar ratio of the initiator to 2-aminotrifluorotoluene is 0.7 to 1.2:1; for example, it can be 0.7:1, 0.8:1, 0.9:1, 1.0:1, 1.1:1, 1.2:1 or any range between the above values.

[0032] According to some embodiments of the present invention, the stirring reaction time after adding the solvent, 2-aminotrifluorotoluene, and acidic additive to the reaction vessel is 5 to 10 minutes; for example, it can be 5 minutes, 6 minutes, 7 minutes, 8 minutes, 9 minutes, 10 minutes, or any range between the above values.

[0033] According to some embodiments of the present invention, the heat preservation reaction time is 2 to 8 hours; for example, it can be 2 hours, 3 hours, 4 hours, 5 hours, 6 hours, 7 hours, 8 hours or any range between the above values.

[0034] According to some embodiments of the present invention, during the condensation process of the remaining heptafluorobromopropane gas in condenser 6, the temperature of condenser 6 is controlled to be between -10°C and 0°C; for example, it can be -10°C, -9°C, -8°C, -7°C, -6°C, -5°C, -4°C, -3°C, -2°C, -1°C, 0°C or any range between the above values.

[0035] To enable those skilled in the art to better understand the technical solution of the present invention, the present invention will be further described below in conjunction with some specific embodiments.

[0036] Example 1 This embodiment provides a method for preparing 2-trifluoromethyl-4-heptafluoroisopropylaniline, specifically including the following steps: In a 1L high-pressure reactor 5, 10mol of acetonitrile, 1mol of 2-aminotrifluorotoluene, and 0.4mol of phosphoric acid were added. After stirring at room temperature for 10min, 0.7mol of sodium dithionite was added. The high-pressure reactor 5 was sealed, and the air inside the reactor 5 was replaced with nitrogen. The temperature was then raised to 60℃, maintained, and heptafluorobromopropane was continuously introduced. The pressure of the high-pressure reactor 5 was controlled at 0.3MPa by the continuous introduction of heptafluorobromopropane. After the reaction was maintained at this temperature for 8h, the temperature was lowered to 30℃, and the introduction of heptafluorobromopropane was stopped. The temperature of the condenser 6 was controlled at 0℃. The remaining gas in the high-pressure reactor 5 was condensed by the condenser 6 and collected in the storage tank 7 for recycling in subsequent batches. The reactants in the high-pressure reactor 5 are introduced into the centrifuge 9 for centrifugation. The centrifuged solids are collected and processed externally, while the centrifuged liquids are introduced into the rotary evaporator 10 for solvent removal. The solvents are collected and recycled. The liquid product after solvent removal (i.e., the crude product) is centrifuged again in the centrifuge 9 to remove solids, and then vacuum dried to remove the small amount of residual solvent, yielding 319.3g of the finished product 2-trifluoromethyl-4-heptafluoroisopropylaniline.

[0037] Based on sampling and testing, the conversion rate of 2-aminotrifluorotoluene in this embodiment was 99.9%, and the selectivity was 99.9%; the gas phase purity of the obtained 2-trifluoromethyl-4-heptafluoroisopropylaniline was 99.89 wt% (e.g., Figure 2 As shown), the molar yield of 2-trifluoromethyl-4-heptafluoroisopropylaniline (based on the molar yield of 2-aminotrifluorotoluene) was 96.9%.

[0038] Example 2 This embodiment provides a method for preparing 2-trifluoromethyl-4-heptafluoroisopropylaniline, specifically including the following steps: In a 1L high-pressure reactor 5, 3 mol of ethyl acetate, 1 mol of 2-aminotrifluorotoluene, and 0.4 mol of sodium bisulfite were added. After stirring at room temperature for 10 min, 1.2 mol of sodium dithionite was added. The high-pressure reactor 5 was sealed, and the air inside the reactor 5 was replaced with nitrogen. The temperature was then raised to 90℃, maintained, and heptafluorobromopropane was continuously introduced. The pressure of the high-pressure reactor 5 was controlled at 0.8 MPa by the continuous introduction of heptafluorobromopropane. After the reaction was maintained at this temperature for 2 h, the temperature was lowered to 50℃, and the introduction of heptafluorobromopropane was stopped. The temperature of the condenser 6 was controlled at -10℃. The remaining gas in the high-pressure reactor 5 was condensed by the condenser 6 and collected in the storage tank 7 for recycling in subsequent batches. The reactants in the high-pressure reactor 5 are introduced into the centrifuge 9 for centrifugation. The centrifuged solids are collected and processed externally, while the centrifuged liquids are introduced into the rotary evaporator 10 for solvent removal. The solvents are collected and recycled. The liquid product after solvent removal (i.e., the crude product) is centrifuged again in the centrifuge 9 to remove solids, and then vacuum dried to remove the small amount of residual solvent, yielding 317.2g of the finished product 2-trifluoromethyl-4-heptafluoroisopropylaniline.

[0039] Based on sampling and testing, the conversion rate of 2-aminotrifluorotoluene in this embodiment was 99.9%, and the selectivity was 99.8%. The gas phase purity of the obtained 2-trifluoromethyl-4-heptafluoroisopropylaniline was 99.74 wt%, and the molar yield of 2-trifluoromethyl-4-heptafluoroisopropylaniline (based on the molar yield of 2-aminotrifluorotoluene) was 96.1%.

[0040] Example 3 This embodiment provides a method for preparing 2-trifluoromethyl-4-heptafluoroisopropylaniline, specifically including the following steps: In a 1L high-pressure reactor 5, 5mol of N,N-dimethylformamide, 1mol of 2-aminotrifluorotoluene, and 1mol of sodium bisulfate were added. After stirring at room temperature for 10 minutes, 1mol of sodium dithionite was added. The high-pressure reactor 5 was sealed, and the air inside the reactor 5 was replaced with nitrogen. The temperature was then raised to 75°C, maintained at this temperature, and heptafluorobromopropane was continuously introduced. The pressure of the high-pressure reactor 5 was controlled at 0.5MPa by the continuous introduction of heptafluorobromopropane. After the reaction was maintained at this temperature for 4 hours, the temperature was lowered to 40°C, and the introduction of heptafluorobromopropane was stopped. The temperature of the condenser 6 was controlled at -5°C. The remaining gas in the high-pressure reactor 5 was condensed by the condenser 6 and collected in the storage tank 7 for recycling in subsequent batches. The reactants in the high-pressure reactor 5 are introduced into the centrifuge 9 for centrifugation. The centrifuged solids are collected and processed externally, while the centrifuged liquids are introduced into the rotary evaporator 10 for solvent removal. The solvents are collected and recycled. The liquid product after solvent removal (i.e., the crude product) is centrifuged again in the centrifuge 9 to remove solids, and then vacuum dried to remove the small amount of residual solvent, yielding 321.5g of the finished product 2-trifluoromethyl-4-heptafluoroisopropylaniline.

[0041] Based on sampling and testing, the conversion rate of 2-aminotrifluorotoluene in this embodiment was 99.9%, and the selectivity was 99.7%. The gas phase purity of the obtained 2-trifluoromethyl-4-heptafluoroisopropylaniline was 99.68 wt%, and the molar yield of 2-trifluoromethyl-4-heptafluoroisopropylaniline (based on the molar yield of 2-aminotrifluorotoluene) was 97.4%.

[0042] Example 4 This embodiment provides a method for preparing 2-trifluoromethyl-4-heptafluoroisopropylaniline, specifically including the following steps: In a 1L high-pressure reactor 5, 5mol of dimethyl sulfoxide, 1mol of 2-aminotrifluorotoluene, and 0.6mol of sodium dihydrogen phosphate were added. After stirring at room temperature for 10 minutes, 0.9mol of sodium dithionite was added. The high-pressure reactor 5 was sealed, and the air inside the reactor 5 was replaced with nitrogen. The temperature was then raised to 80℃, maintained, and heptafluorobromopropane was continuously introduced. The pressure of the high-pressure reactor 5 was controlled at 0.6MPa by the continuous introduction of heptafluorobromopropane. After the reaction was maintained at this temperature for 6 hours, the temperature was lowered to 35℃, and the introduction of heptafluorobromopropane was stopped. The temperature of the condenser 6 was controlled at -5℃. The remaining gas in the high-pressure reactor 5 was condensed by the condenser 6 and collected in the storage tank 7 for recycling in subsequent batches. The reactants in the high-pressure reactor 5 are introduced into the centrifuge 9 for centrifugation. The centrifuged solids are collected and processed externally, while the centrifuged liquids are introduced into the rotary evaporator 10 for solvent removal. The solvents are collected and recycled. The liquid product after solvent removal (i.e., the crude product) is centrifuged again in the centrifuge 9 to remove solids, and then vacuum dried to remove the small amount of residual solvent, yielding 318.5g of the finished product 2-trifluoromethyl-4-heptafluoroisopropylaniline.

[0043] Based on sampling and testing, the conversion rate of 2-aminotrifluorotoluene in this embodiment was 99.9%, and the selectivity was 99.8%. The gas phase purity of the obtained 2-trifluoromethyl-4-heptafluoroisopropylaniline was 99.75 wt%, and the molar yield of 2-trifluoromethyl-4-heptafluoroisopropylaniline (based on the molar yield of 2-aminotrifluorotoluene) was 96.5%.

[0044] Example 5 This embodiment provides a method for preparing 2-trifluoromethyl-4-heptafluoroisopropylaniline, specifically including the following steps: In a 1L high-pressure reactor 5, 4 mol of ethylene glycol dimethyl ether, 1 mol of 2-aminotrifluorotoluene, and 1 mol of sodium bisulfite were added. After stirring at room temperature for 10 min, 0.8 mol of sodium dithionite was added. The high-pressure reactor 5 was sealed, and the air inside the reactor 5 was replaced with nitrogen. The temperature was then raised to 80℃, maintained, and heptafluorobromopropane was continuously introduced. The pressure of the high-pressure reactor 5 was controlled at 0.4 MPa by the continuous introduction of heptafluorobromopropane. After the reaction was maintained at this temperature for 5 h, the temperature was lowered to 30℃, and the introduction of heptafluorobromopropane was stopped. The temperature of the condenser 6 was controlled at 0℃. The remaining gas in the high-pressure reactor 5 was condensed by the condenser 6 and collected in the storage tank 7 for recycling in subsequent batches. The reactants in the high-pressure reactor 5 are introduced into the centrifuge 9 for centrifugation. The centrifuged solids are collected and processed externally, while the centrifuged liquids are introduced into the rotary evaporator 10 for solvent removal. The solvents are collected and recycled. The liquid product after solvent removal (i.e., the crude product) is centrifuged again in the centrifuge 9 to remove solids, and then vacuum dried to remove the small amount of residual solvent, yielding 319.8g of the finished product 2-trifluoromethyl-4-heptafluoroisopropylaniline.

[0045] Based on sampling and testing, the conversion rate of 2-aminotrifluorotoluene in this embodiment was 99.9%, and the selectivity was 99.7%. The gas phase purity of the obtained 2-trifluoromethyl-4-heptafluoroisopropylaniline was 99.64 wt%, and the molar yield of 2-trifluoromethyl-4-heptafluoroisopropylaniline (based on the molar yield of 2-aminotrifluorotoluene) was 96.8%.

[0046] Example 6 This embodiment provides a method for preparing 2-trifluoromethyl-4-heptafluoroisopropylaniline, specifically including the following steps: In a 1L high-pressure reactor 5, 8mol of acetonitrile, 1mol of 2-aminotrifluorotoluene, and 1mol of sodium bisulfite were added. After stirring at room temperature for 10 minutes, 0.9mol of sodium dithionite was added. The high-pressure reactor 5 was sealed, and the air inside the reactor 5 was replaced with nitrogen. The temperature was then raised to 85℃, maintained at this temperature, and heptafluorobromopropane was continuously introduced. The pressure of the high-pressure reactor 5 was controlled at 0.5MPa by the continuous introduction of heptafluorobromopropane. After the reaction was maintained at this temperature for 3 hours, the temperature was lowered to 30℃, and the introduction of heptafluorobromopropane was stopped. The temperature of the condenser 6 was controlled at 0℃. The remaining gas in the high-pressure reactor 5 was condensed by the condenser 6 and collected in the storage tank 7 for recycling in subsequent batches. The reactants in the high-pressure reactor 5 are introduced into the centrifuge 9 for centrifugation. The centrifuged solids are collected and processed externally, while the centrifuged liquids are introduced into the rotary evaporator 10 for solvent removal. The solvents are collected and recycled. The liquid product after solvent removal (i.e., the crude product) is centrifuged again in the centrifuge 9 to remove solids, and then vacuum dried to remove the small amount of residual solvent, yielding 320.9g of the finished product 2-trifluoromethyl-4-heptafluoroisopropylaniline.

[0047] Based on sampling and testing, the conversion rate of 2-aminotrifluorotoluene in this embodiment was 99.9%, and the selectivity was 99.9%. The gas phase purity of the obtained 2-trifluoromethyl-4-heptafluoroisopropylaniline was 99.84 wt%, and the molar yield of 2-trifluoromethyl-4-heptafluoroisopropylaniline (based on the molar yield of 2-aminotrifluorotoluene) was 97.3%.

[0048] Comparative Example 1 The difference from Example 1 is that the pressure of the high-pressure reactor 5 is controlled at 0.2 MPa by continuously introducing heptafluorobromopropane; other operations and process parameters are the same as in Example 1.

[0049] Comparative Example 1 yielded 312.7 g of the final product 2-trifluoromethyl-4-heptafluoroisopropylaniline. Sampling and analysis showed that its 2-aminotrifluorotoluene conversion rate was 96.5%, and its selectivity was 99.9%. The gas phase purity of the obtained 2-trifluoromethyl-4-heptafluoroisopropylaniline was 96.40 wt%, and the separated molar yield of 2-trifluoromethyl-4-heptafluoroisopropylaniline (based on the molar yield of 2-aminotrifluorotoluene) was 91.6%.

[0050] Comparative Example 2 The difference from Example 1 is that the amount of phosphoric acid was reduced to 0.1 mol; and acetonitrile, phosphoric acid, and sodium dithionite were first added to the high-pressure reactor 5, and a large number of bubbles were observed to emerge. Then 2-aminotrifluorotoluene was added, and the high-pressure reactor 5 was sealed. Other operations and process parameters were the same as in Example 1.

[0051] Comparative Example 2 yielded 252.6 g of the final product 2-trifluoromethyl-4-heptafluoroisopropylaniline. Sampling and analysis showed that its 2-aminotrifluorotoluene conversion rate was 60.2%, and its selectivity was 94.8%. The gas phase purity of the obtained 2-trifluoromethyl-4-heptafluoroisopropylaniline was 58.83 wt%, and the separated molar yield of 2-trifluoromethyl-4-heptafluoroisopropylaniline (based on the molar yield of 2-aminotrifluorotoluene) was 45.1%.

[0052] The preparation data for Examples 1-6 and Comparative Examples 1-2 are shown in the table below:

[0053] As can be seen from the table above, in the preparation of 2-trifluoromethyl-4-heptafluoroisopropylaniline in Examples 1-6, the conversion rate of 2-aminotrifluorotoluene can reach 99.9%, the selectivity is 99.7-99.9%, the product purity is 99.64-99.89 wt%, and the molar yield is 96.1-97.4%.

[0054] In Comparative Example 1, reducing the reaction pressure of 2-bromoheptafluoropropane affected the solubility of heptafluorobromopropane in the solvent, reduced the contact probability of the gas-liquid-solid three phases, and ultimately led to a decrease in the conversion rate of 2-amino-trifluoromethylbenzene and a decrease in the separation molar yield of the product 2-trifluoromethyl-4-heptafluoroisopropylaniline.

[0055] Comparative Example 2 changed the feeding sequence, causing sodium dithionite to come into direct contact with the acidic auxiliary agent (phosphoric acid) and undergo a decomposition reaction, affecting the conversion rate of the reaction; at the same time, reducing the amount of acidic auxiliary agent (phosphoric acid) led to a decrease in the steric hindrance of the ortho-amino group, which could not effectively suppress the formation of ortho-substituted byproducts, resulting in a decrease in selectivity.

[0056] Unless otherwise stated, all percentages used in this invention are mass percentages.

[0057] Finally, it should be noted that the above descriptions are merely preferred embodiments of the present invention and are not intended to limit the present invention. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art can still modify the technical solutions described in the foregoing embodiments or make equivalent substitutions for some of the technical features. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for preparing 2-trifluoromethyl-4-heptafluoroisopropylaniline, characterized in that, Includes the following steps: Solvent, 2-aminotrifluorotoluene, and acidic additives were added to a reactor. After stirring and reacting, an initiator was added, the reactor was sealed, and the air inside the reactor was completely replaced with nitrogen. The temperature was then raised to 60-90°C and maintained. Heptafluorobromopropane was continuously introduced into the reactor, and the pressure inside the reactor was controlled at 0.5-1.0 MPa by continuously introducing heptafluorobromopropane. After maintaining the temperature for the reaction, the temperature was lowered. The remaining gas in the reactor was condensed and recovered to obtain the reaction material. The reaction material was purified to obtain 2-trifluoromethyl-4-heptafluoroisopropylaniline.

2. The method for preparing 2-trifluoromethyl-4-heptafluoroisopropylaniline according to claim 1, characterized in that, The purification process involves centrifuging the reaction material to remove solids, then desolventizing the centrifuged liquid; the desolventized liquid is then centrifuged again to remove solids and dried to obtain 2-trifluoromethyl-4-heptafluoroisopropylaniline.

3. The method for preparing 2-trifluoromethyl-4-heptafluoroisopropylaniline according to claim 1, characterized in that, The acidic additive is one of the following: sodium bisulfate, sodium bisulfite, sodium dihydrogen phosphate, or phosphoric acid.

4. The method for preparing 2-trifluoromethyl-4-heptafluoroisopropylaniline according to claim 1, characterized in that, The molar ratio of the acidic additive to 2-aminotrifluorotoluene is 0.4~1.2:

1.

5. The method for preparing 2-trifluoromethyl-4-heptafluoroisopropylaniline according to claim 1, characterized in that, The solvent is one of the following: ethyl acetate, N,N-dimethylformamide, dimethyl sulfoxide, acetonitrile, or ethylene glycol dimethyl ether.

6. The method for preparing 2-trifluoromethyl-4-heptafluoroisopropylaniline according to claim 1, characterized in that, The molar ratio of the solvent to 2-aminotrifluorotoluene is 3~10:

1.

7. The method for preparing 2-trifluoromethyl-4-heptafluoroisopropylaniline according to claim 1, characterized in that, The initiator includes sodium dithionite; The molar ratio of the initiator to 2-aminotrifluorotoluene is 0.7~1.2:

1.

8. The method for preparing 2-trifluoromethyl-4-heptafluoroisopropylaniline according to claim 1, characterized in that, The reaction time after adding the solvent, 2-aminotrifluorotoluene, and acidic additives to the reactor is 5-10 minutes.

9. The method for preparing 2-trifluoromethyl-4-heptafluoroisopropylaniline according to claim 1, characterized in that, The heat preservation reaction time is 2-8 hours; After the heat treatment reaction, the temperature is lowered to 30~50℃.

10. The method for preparing 2-trifluoromethyl-4-heptafluoroisopropylaniline according to claim 1, characterized in that, The residual gas in the condensation recovery reactor is condensed, and the condensation temperature is controlled between -10℃ and 0℃.

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