Preparation method of 3, 4-dichlorobenzotrifluoride

Abstract

The invention relates to the technical field of chemical synthesis, in particular to a preparation method of 3, 4-dichlorobenzotrifluoride, which comprises the following steps: firstly, adding dibenzoyl peroxide and N-hydroxyphthalimide into parachlorotoluene, and performing side chain chlorination reaction under ultraviolet irradiation and chlorine atmosphere to generate parachlorobenzotrifluoride; secondly, the obtained p-chlorobenzotrifluoride and tetrabutylammonium fluoride and potassium fluoride composite fluorination reagent are subjected to a fluorination reaction in the presence of a copper powder-1, 10-phenanthroline complex, and p-chlorobenzotrifluoride is prepared; and finally, under the catalysis of the mesoporous silica supported ferric trichloride catalyst, performing aromatic electrophilic chlorination on chlorobenzotrifluoride and sulfuryl chloride to obtain the high-purity 3, 4-dichlorobenzotrifluoride. Through synergistic application of photochemical chlorination, a composite fluorination system and the supported catalyst, the method has the advantages of mild reaction conditions, safe operation, high yield and good selectivity, and is suitable for industrial production.

Description

Technical Field

[0001] This invention relates to the field of chemical synthesis technology, and in particular to a method for preparing 3,4-dichlorotrifluorotoluene. Background Technology

[0002] 3,4-Dichlorotrifluorotoluene is an important fluorinated aromatic intermediate widely used in pharmaceuticals, pesticides, dyes, and functional materials. Its molecular structure contains both chlorine atoms and trifluoromethyl groups. The synergistic effect of these two groups gives it unique chemical activity and stability, making it a key raw material for the synthesis of a variety of high-value-added fine chemicals, and market demand continues to grow.

[0003] In current technologies for preparing 3,4-dichlorotrifluorotoluene, p-chlorotoluene is typically used as the starting material, and the synthesis is completed in three steps: side-chain chlorination, fluorination, and aromatic ring chlorination. However, existing processes suffer from significant technical bottlenecks at each reaction stage. The side-chain chlorination stage often employs traditional thermal initiation or ordinary ultraviolet lamp irradiation. Thermal initiation involves harsh reaction conditions, requiring high temperatures and exhibiting poor reaction selectivity, which can easily lead to chlorination side reactions of the benzene ring, generating polychlorinated impurities and reducing product purity. Ordinary ultraviolet lamps have a wide wavelength range and dispersed energy, resulting in low energy utilization and difficulty in precisely controlling the chlorine free radical generation rate, leading to unstable reaction efficiency and affecting the continuity of subsequent processes.

[0004] The fluorination stage is the riskiest and most challenging part of the existing process, with traditional methods generally relying on anhydrous hydrogen fluoride as the fluorinating agent. Anhydrous hydrogen fluoride is extremely corrosive and toxic, highly volatile, and reacts violently with water. The operation requires specialized corrosion-resistant alloy equipment, resulting in high equipment investment costs and serious safety hazards. Leaks can cause significant harm to operator health and the environment. Furthermore, the reactivity of anhydrous hydrogen fluoride with p-chlorotrichlorotoluene is difficult to control, easily leading to incomplete or over-fluorination, resulting in a decrease in the yield of the target product. The aromatic ring chlorination stage often uses ferric chloride as a catalyst. Ferric chloride is prone to agglomeration and has poor dispersion in the reaction system, leading to uneven distribution of active sites, low efficiency in chloride cation formation, and highly random attack on benzene ring positions. This easily generates chlorinated byproducts at non-target positions, further reducing the purity and yield of the final product, making it difficult to meet the demands of industrial production for high efficiency, safety, and high purity. Summary of the Invention

[0005] To address the aforementioned technical problems, this invention provides a method for preparing 3,4-dichlorotrifluorotoluene. This method utilizes ultraviolet light to initiate side-chain chlorination, a composite fluorinating agent to replace anhydrous hydrogen fluoride, and a supported catalyst to catalyze the chlorination of aromatic rings. This solves the technical problems of poor safety, numerous side reactions, low selectivity, and severe environmental pollution in traditional processes for preparing 3,4-dichlorotrifluorotoluene. Specifically, this is achieved through the following technical solutions.

[0006] This invention discloses a method for preparing 3,4-dichlorotrifluorotoluene, comprising the following steps: Step 1: Under ultraviolet light irradiation with a wavelength of 350–380 nm and a light intensity of 8–12 W / m², p-chlorotoluene and chlorine gas are reacted in the presence of benzoyl peroxide and N-hydroxyphthalimide at a reaction temperature of 80–100 °C and a chlorine gas introduction rate of 0.1–0.13 L / min for 8 hours to produce p-chlorotrichlorotoluene. Step 2: Add p-chlorotrichlorotoluene, a fluorinating agent composed of tetrabutylammonium fluoride and potassium fluoride in a molar ratio of 1:2, and copper powder-1,10-phenanthroline complex to the solvent N-methylpyrrolidone, and react at 80°C for 2 hours to generate p-chlorotrifluorotoluene. Step 3: Add p-chlorotrifluorotoluene, thioyl chloride and ferric chloride catalyst supported on mesoporous silica into a flask and react at 40°C for 3 hours to generate 3,4-dichlorotrifluorotoluene; The preparation method of the mesoporous silica-supported ferric chloride catalyst includes the following steps: S1: Calcine mesoporous silica at 300℃ for 2 hours; S2: Mix the calcined mesoporous silica with an ethanol solution of ferric chloride, wherein the mass ratio of ferric chloride, ethanol and mesoporous silica is 1:12-14:9-12; S3: After the mixed material has been left to stand at room temperature for 4 hours, it is transferred to a vacuum environment at 60°C and dried for 12 hours. S4: The dried material is heated to 300°C at a rate of 2°C / min in air and calcined at a constant temperature for 3 hours to obtain the catalyst.

[0007] Preferably, the mass ratio of p-chlorotoluene, benzoyl peroxide, and N-hydroxyphthalimide in step 1 is 100:1-2:1-2.

[0008] Preferably, after the reaction in step 1 is completed, the mixture is purged with nitrogen for 30 minutes to remove chlorine and hydrogen chloride.

[0009] Preferably, the molar ratio of fluoride ions to p-chlorotrichlorotoluene in the fluorinating reagent in step 2 is 1.05 to 1.1:1.

[0010] Preferably, the mass of the copper powder-1,10-phenanthroline complex added in step 2 is 5% to 6% of the mass of p-chlorotrichlorotoluene.

[0011] Preferably, the reaction in step 2 is carried out at a stirring speed of 400 to 600 rpm.

[0012] Preferably, after the reaction in step 2 is completed, the reaction solution is injected into a mixture of 4 to 5 times its volume of ice and water to quench it. The organic phase is washed three times with saturated NaCl solution, dried with anhydrous magnesium sulfate, and then subjected to vacuum distillation.

[0013] Preferably, the mass of the catalyst added in step 3 is 3% to 5% of the mass of p-chlorotrifluorotoluene, and the molar ratio of thioyl chloride to p-chlorotrifluorotoluene is 1.05 to 1.1:1.

[0014] Preferably, after the reaction in step 3 is completed, the catalyst is separated by hot filtration, washed with anhydrous ethanol, and then vacuum dried at 60-80°C for 4-6 hours for reuse. The reaction solution is washed with 5% sodium bicarbonate solution until neutral, and then vacuum distilled at 1.3-2.5 kPa and 120-140°C to obtain the final product.

[0015] After adopting the above technical solution, the beneficial effects of the present invention are: 1. By using ultraviolet light to excite the homolytic cleavage of chlorine molecules to generate chlorine free radicals, and combining the synergistic effect of benzoyl peroxide and N-hydroxyphthalimide, the reaction rate and selectivity of side chain chlorination were significantly improved, and the occurrence of side reactions of benzene ring chlorination was effectively suppressed, thus achieving the preparation of p-chlorotrichlorotoluene with high yield and high purity.

[0016] 2. By using a tetrabutylammonium fluoride-potassium fluoride complex as a fluorinating agent to replace traditional anhydrous hydrogen fluoride, the use of highly corrosive and toxic reagents is completely eliminated, significantly improving operational safety and environmental friendliness. At the same time, the catalytic effect of copper powder-1,10-phenanthroline complex promotes the nucleophilic attack of fluoride ions, improving the efficiency and selectivity of the fluorination reaction.

[0017] 3. Using mesoporous silica-supported ferric chloride as a catalyst not only provides highly dispersed and stable active sites, effectively promoting electrophilic chlorination reactions on aromatic rings, but also enables easy recovery and multiple reuse of the catalyst, reducing production costs and environmental impact.

[0018] 4. The overall process conditions are mild, requiring no high pressure or special equipment. The steps are closely linked, with few side reactions. The final product has excellent yield and purity, making it suitable for large-scale industrial production while reducing waste generation and subsequent treatment burden. Attached Figure Description

[0019] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0020] Figure 1 The infrared spectrum of the intermediate product p-chlorotrichlorotoluene; Figure 2 The infrared spectrum of the intermediate product p-chlorotrifluorotoluene; Figure 3 The image shows the infrared spectrum of the final product, 3,4-dichlorotrifluorotoluene. Detailed Implementation

[0021] The features and exemplary embodiments of various aspects of the present invention will now be described in detail. To make the objectives, technical solutions, and advantages of the present invention clearer, the present invention will be further described in detail below with reference to specific embodiments. It should be understood that the specific embodiments described herein are only configured to explain the present invention and are not configured to limit the present invention. For those skilled in the art, the present invention can be practiced without some of these specific details. The following description of the embodiments is merely intended to provide a better understanding of the present invention by illustrating examples of the invention.

[0022] An embodiment of the present invention provides a method for preparing 3,4-dichlorotrifluorotoluene, specifically including the following steps: Step 1: p-chlorotoluene, benzoyl peroxide, and N-hydroxyphthalimide were added to a reactor equipped with a UV LED light source. After the addition was completed, the UV LED light was turned on and the reactor was stirred. The temperature was raised to 80-100°C, and chlorine gas was continuously introduced into the reactor. After the reaction was completed for 8 hours, the chlorine gas was stopped, and the chlorine and hydrogen chloride in the reactor were removed by purging with nitrogen gas. After purging, the heating was stopped and the reaction solution was cooled to room temperature. After washing with water and separating the liquid, the lower organic phase of p-chlorotrichlorotoluene was obtained.

[0023] In the above steps, the mass ratio of p-chlorotoluene, benzoyl peroxide, and N-hydroxyphthalimide is 100:1~2:1~2.

[0024] In the above steps, the wavelength of the ultraviolet LED lamp is 350–380 nm, and the light intensity is 8–12 W / m². 2 The chlorine gas was introduced at a rate of 0.1–0.13 L / min, and the nitrogen purging time was 30 minutes.

[0025] The water washing process of the reaction solution is as follows: it is washed three times with deionized water, and the volume of deionized water used in each wash is equal to the volume of the reaction solution.

[0026] During the reaction, the stirring speed is always controlled at 300-500 rpm.

[0027] In the above reaction process, ultraviolet light excites chlorine molecules to homolytically cleave and generate chlorine free radicals. The chlorine free radicals attack the hydrogen atoms on the p-chlorotoluene methyl group to form benzyl free radicals, which then react with chlorine molecules to generate chlorination products and regenerate chlorine free radicals, gradually completing the trichlorination process.

[0028] See appendix Figure 1 In the generated p-chlorotrichlorotoluene, 3093.82 cm -1 The corresponding characteristic peak is the stretching vibration peak of the CH bond in the benzene ring, at 1593.20 cm⁻¹. -1 The corresponding characteristic peak is the vibrational peak of the benzene ring skeleton, 894.97 cm⁻¹. -1 The corresponding characteristic peak is the stretching vibration peak of the C-Cl bond in trichloromethyl. The detection of the C-Cl bond stretching vibration peak during the above steps proves that the -CH3 side chain of chlorotoluene is chlorinated to -CCl3.

[0029] In this process, benzoyl peroxide acts as an initiator, decomposing under ultraviolet light to generate free radicals and initiate the chain reaction; N-hydroxyphthalimide acts as a catalyst, enhancing the generation rate of chlorine free radicals by forming an imine free radical intermediate, thereby reducing the activation energy of the reaction and improving the reaction efficiency.

[0030] In addition, the photochemical chlorination conditions are mild and highly selective, reducing the side reactions of benzene ring chlorination. Through the stepwise chlorination of the methyl group on the side chain of p-chlorotoluene, p-chlorotrichlorotoluene is generated.

[0031] Step 2: The p-chlorotrichlorotoluene obtained in step 1 and N-methylpyrrolidone were added to a reaction vessel. A fluorinating agent and copper powder-1,10-phenanthroline complex were added to the reaction vessel. The mixture was stirred and heated to 80°C for 2 hours. After the reaction was completed, the reaction solution was quenched in an ice-water mixture. The organic phase was washed, dried, and then distilled under reduced pressure to obtain p-chlorotrifluorotoluene.

[0032] In the above steps, the mass ratio of p-chlorotrichlorotoluene to N-methylpyrrolidone is 1:2 to 2.3.

[0033] In the above steps, the fluorinating agent is a complex of tetrabutylammonium fluoride and potassium fluoride. The fluorinating agent is prepared by mixing tetrabutylammonium fluoride and potassium fluoride in a molar ratio of 1:2 and then grinding and mixing them in a dry inert atmosphere. The molar ratio of fluoride ions in the fluorinating agent to p-chlorotrichlorotoluene is 1.05 to 1.1:1.

[0034] The added copper powder-1,10-phenanthroline complex has a mass of 5% to 6% of p-chlorotrichlorotoluene, and the copper powder-1,10-phenanthroline complex is prepared by refluxing copper powder and 1,10-phenanthroline in ethanol at a molar ratio of 1:2 for 2 hours, filtering and drying.

[0035] In the above steps, the organic phase is subjected to vacuum distillation at 50–60 °C and 1.3–2.5 kPa.

[0036] During the quenching process, the volume of the ice-water mixture is 4 to 5 times the volume of the reaction liquid.

[0037] During the above reaction process, the stirring speed is 400-600 rpm to keep the solid reagent completely suspended.

[0038] The specific process of washing and drying the organic phase is as follows: wash three times with a saturated NaCl solution of equal volume to the organic phase, and after separation, add anhydrous magnesium sulfate to the organic phase and dry for 30 minutes.

[0039] In the above reaction process, the fluorinating reagent composed of tetrabutylammonium fluoride and potassium fluoride complex provides fluoride ions, which attack the carbon atoms in trichloromethyl, gradually replacing the chlorine atoms to form monofluoro, difluoro, and trifluoromethyl intermediates. In this process, the copper powder-1,10-phenanthroline complex acts as an electron transfer medium, stabilizing the reaction intermediates through coordination, promoting the nucleophilic attack of fluoride ions, lowering the energy barrier of the fluorination reaction, and improving the substitution efficiency.

[0040] See appendix Figure 2 In the generated p-chlorotrifluorotoluene, 1325.10 cm -1 The corresponding characteristic peak is the stretching vibration peak of the CF bond in the trifluoromethyl group, and is associated with the attached peak. Figure 1 Compared to the characteristic peaks of the C-Cl bond, the characteristic peak of the C-Cl bond in trichloromethyl disappears, which corresponds to the structural transformation of the fluorination reaction in the process, that is, the -CCl3 in the side chain is replaced by the composite fluorinating agent as -CF3.

[0041] In this step, a tetrabutylammonium fluoride and potassium fluoride complex is used as the fluorinating agent to replace the traditional anhydrous hydrogen fluoride, which fundamentally improves safety, operability and environmental friendliness. It eliminates the extremely high safety risks brought by the highly toxic, corrosive and volatile hydrogen fluoride, so that the reaction does not need to rely on special corrosion-resistant alloy equipment and high pressure conditions, but can be safely carried out in a conventional reactor at normal pressure and mild temperature.

[0042] Furthermore, this fluorinating reagent forms a highly active fluorination system with potassium fluoride through the phase transfer catalysis of tetrabutylammonium fluoride, effectively solving the problems of poor solubility and low reactivity of potassium fluoride in organic phases, thereby ensuring excellent reaction efficiency and high selectivity for side-chain chlorine atoms.

[0043] Step 3: The p-chlorotrifluorotoluene obtained in step 2 and the catalyst were added to a flask and preheated to 40°C under stirring. Thionyl chloride was added dropwise to the flask using a dropping funnel at a rate of 1-2 drops / second. After the addition was complete, the reaction was continued for 3 hours. After the reaction was completed, the solid catalyst was separated by hot filtration. The catalyst was washed, dried, activated and reused. The remaining reaction solution was washed with 5% sodium bicarbonate solution until neutral and then dried. The final product, 3,4-dichlorotrifluorotoluene, was obtained by vacuum distillation.

[0044] The added catalyst is a ferric chloride catalyst supported on mesoporous silica, and its added mass is 3% to 5% of the mass of p-chlorotrifluorotoluene. The molar ratio of the added thioyl chloride to p-chlorotrifluorotoluene is 1.05 to 1.1:1.

[0045] The specific process for reusing the catalyst after cleaning, drying and activation is as follows: the catalyst surface is rinsed with anhydrous ethanol, the cleaned catalyst is transferred to a vacuum drying oven, and dried at 60-80°C under vacuum for 4-6 hours before reuse.

[0046] In the above process, rinsing with anhydrous ethanol can remove adsorbed unreacted raw materials, by-products and residual reaction liquid, avoiding impurities from clogging the catalyst pores or affecting subsequent activity; drying thoroughly removes residual organic solvents and moisture, thereby ensuring the activity of the catalyst.

[0047] The residual hydrogen chloride and undecomposed thioyl chloride in the reaction solution in the above steps are both acidic substances. A 5% sodium bicarbonate solution can be used to react with these acidic substances to neutralize the reaction solution and avoid the acidic substances from corroding the equipment or reacting with the product during the subsequent distillation process.

[0048] In addition, the sodium chloride and sodium sulfate produced by the above neutralization reaction are both water-soluble substances and can be removed along with the aqueous phase after washing; at the same time, the sodium bicarbonate solution can dissolve some polar impurities, further purifying the organic phase.

[0049] The vacuum distillation conditions for the final product 3,4-dichlorotrifluorotoluene are: pressure 1.3–2.5 kPa and temperature 120–140 °C.

[0050] In the above steps, an electrophilic aromatic chlorination reaction occurs, introducing a second chlorine atom onto the benzene ring of p-chlorotrifluorotoluene to generate 3,4-dichlorotrifluorotoluene.

[0051] See appendix Figure 3 In the generated 3,4-dichlorotrifluorotoluene, 1608.63 cm -1 The corresponding characteristic peak is the vibrational peak of the benzene ring skeleton, and this characteristic peak is related to the attached... Figure 1 Appendix Figure 2The vibrational peaks of the benzene ring skeleton showed a slight shift, indicating that a new chlorine substitution was added at the ortho position of the benzene ring of p-chlorotrifluorotoluene, forming a 3,4-dichloro structure.

[0052] The added thioyl chloride acts as a chlorinating agent, which decomposes to produce chlorocations under the action of ferric chloride-supported catalyst. Due to the strong electron-withdrawing effect of trifluoromethyl, chlorine substitution mainly occurs at the ortho position of the original chlorine atom, thus forming a 3,4-dichloro product.

[0053] The preparation method of the above-mentioned mesoporous silica-supported ferric chloride catalyst includes the following steps: S1: Place the mesoporous silica SBA-15 in a muffle furnace and calcine it at 300°C for 2 hours. After calcination, transfer it to a desiccator to cool to room temperature for later use.

[0054] This step activates and purifies the catalyst support mesoporous silica SBA-15 through sintering. High-temperature calcination can utilize thermal energy to destroy the adsorption effect, thereby removing moisture and impurities in the pores and exposing a clean silanol surface, preparing it for subsequent loading of active components.

[0055] The mesoporous silica is a silica material with a nanoscale mesoporous structure. As a prior art readily known to those skilled in the art, the mesoporous silica here can be MCM-41, MCM-48, SBA-15, SBA-16, HMS-1, FDU-12, or other silica materials with a nanoscale mesoporous structure. The SBA-15 selected in this application is merely one feasible example of mesoporous silica and is not intended to limit the technical solution of this application. Those skilled in the art can replace SBA-15 in this application with other types of mesoporous silica to obtain similar technical effects.

[0056] S2: Mix anhydrous FeCl3 and anhydrous ethanol evenly to prepare a loaded mixture. Add the loaded mixture dropwise to the SBA-15 after calcination in step S1 and continue stirring until the loaded mixture is completely absorbed.

[0057] In the above steps, the mass ratio of anhydrous FeCl3, anhydrous ethanol and SBA-15 is 1:12-14:9-12.

[0058] In the above steps, the prepared FeCl3 / ethanol solution is added dropwise to the continuously stirred SBA-15 powder. Driven by capillary force, the ethanol solution rapidly enters the nanoscale channels of SBA-15 and carries the dissolved FeCl3 molecules in, thereby ensuring the uniform distribution of the active component precursor inside the carrier.

[0059] S3: Seal the SBA-15 that has absorbed the loaded mixture in step S2, let it stand at room temperature for 4 hours, and then transfer it to a vacuum drying oven at 60°C to dry for 12 hours.

[0060] In the above steps, the principle of molecular diffusion driven by concentration gradient is utilized, so that the FeCl3 molecules dissolved in the pores have enough time to redistribute from the pore opening to the depth and throughout the entire three-dimensional pore network during the settling process, thereby achieving a more balanced adsorption.

[0061] In addition, by using a vacuum drying environment to lower the boiling point of ethanol, it can be rapidly and gently evaporated and removed. The remaining solid FeCl3 crystals or monolayers are highly dispersed and attached to the pore wall surface of SBA-15.

[0062] S4: Transfer the dried solid powder to a crucible and place it in a muffle furnace; under an air atmosphere, heat the powder from room temperature to 300°C at a heating rate of 2°C / min, and calcine it at 300°C for 3 hours. After calcination, allow it to cool naturally to below 80°C in the furnace, then remove it and transfer it to a desiccator, seal it, and cool it to room temperature to complete the preparation.

[0063] In the above steps, the anhydrous FeCl3 loaded in the SBA-15 carrier maintains the active component morphology during calcination, and achieves high dispersibility through the mesoporous silica carrier, avoiding agglomeration and deactivation.

[0064] The slow, programmed heating process ensures the smooth decomposition of the precursor and prevents the collapse of the pore structure caused by rapid venting. Maintaining a constant temperature of 300°C for 3 hours ensures complete conversion. Cooling the catalyst to below 80°C during furnace operation is to prevent it from absorbing moisture when it comes into contact with air during removal, thus maintaining its stability.

[0065] Through the above four steps, a highly dispersed, structurally stable, highly active, and reproducible supported catalyst is finally prepared to ensure efficient and selective catalysis of the aromatic chlorination reaction in step 3.

[0066] To facilitate understanding of the present invention, several embodiments and comparative examples are given below.

[0067] Example 1 A method for preparing 3,4-dichlorotrifluorotoluene specifically includes the following steps: Phase 1: Catalyst Preparation S1: Place 50g of mesoporous silica SBA-15 in a muffle furnace and calcine at 300℃ for 2 hours. After calcination, transfer it to a desiccator to cool to room temperature for later use.

[0068] S2: Mix 3g of anhydrous FeCl3 with 36g of anhydrous ethanol to prepare a loaded mixture. Add the loaded mixture dropwise to 27g of SBA-15 after calcination in step S1 and stir continuously until the loaded mixture is completely absorbed.

[0069] S3: Seal the SBA-15 that has absorbed the loaded mixture in step S2, let it stand at room temperature for 4 hours, and then transfer it to a vacuum drying oven at 60°C to dry for 12 hours.

[0070] S4: Transfer the dried solid powder to a crucible, place it in a muffle furnace, and heat it from room temperature to 300°C at a rate of 2°C / min under an air atmosphere. Then, calcine it at a constant temperature of 300°C for 3 hours. After calcination, allow it to cool naturally to below 80°C in the furnace. Then, remove it and transfer it to a desiccator, seal it, and cool it to room temperature to complete the preparation.

[0071] Phase 2: Preparation of 3,4-dichlorotrifluorotoluene Step 1: Add 500g of p-chlorotoluene, 5g of benzoyl peroxide, and 5g of N-hydroxyphthalimide to a reactor equipped with a UV LED lamp light source. After addition, turn on the UV LED lamp and stir. The wavelength of the UV LED lamp is 350nm, and the light intensity is 8W / m². 2 The stirring rate was 300 rpm, the temperature was raised to 80°C, and chlorine gas was continuously introduced into the reactor at a rate of 0.1 L / min. After 8 hours of reaction, the chlorine gas was stopped, and the reactor was purged with nitrogen for 30 minutes. After purging, the heating was stopped and the reaction solution was cooled to room temperature. The reaction solution was washed three times with equal volumes of deionized water and then separated to obtain the lower organic phase of trichlorotoluene.

[0072] Step 2: 200g of p-chlorotrichlorotoluene and 400g of N-methylpyrrolidone obtained in step 1 were added to a reaction vessel. A fluorinating agent prepared by grinding and mixing 79.6g of tetrabutylammonium fluoride and 35.4g of potassium fluoride under a dry inert atmosphere was added to the reaction vessel. Then, 10g of copper powder-1,10-phenanthroline complex prepared by refluxing in ethanol at a molar ratio of 1:2 for 2 hours, filtering and drying was added to the reaction vessel. The mixture was stirred at 400 rpm and heated to 80°C for 2 hours. After the reaction was completed, the reaction solution was quenched in a mixture of 4 times its volume of ice and water. The organic phase was washed three times with an equal volume of saturated NaCl solution. After separation, the organic phase was dried with anhydrous magnesium sulfate for 30 minutes and then distilled under reduced pressure at 50°C and 1.3 kPa to obtain p-chlorotrichlorotoluene.

[0073] Step 3: 100g of p-chlorotrifluorotoluene obtained in step 2 and 3g of the catalyst prepared in the first stage were added to a flask. The mixture was preheated to 40°C under stirring. 78.5g of thioyl chloride was added dropwise to the flask using a dropping funnel at a rate of 1 drop / second. After the addition was complete, the reaction was continued for 3 hours. After the reaction was completed, the solid catalyst was separated by hot filtration and washed with anhydrous ethanol. The washed catalyst was transferred to a vacuum drying oven and dried at 60°C under vacuum for 6 hours before reuse. The remaining reaction solution was washed with 5% sodium bicarbonate solution until neutral. The organic phase was dried and then distilled at a pressure of 1.3 kPa and a temperature of 120°C to obtain the final product 3,4-dichlorotrifluorotoluene.

[0074] Example 2 A method for preparing 3,4-dichlorotrifluorotoluene specifically includes the following steps: Phase 1: Catalyst Preparation S1: Place 50g of mesoporous silica SBA-15 in a muffle furnace and calcine at 300℃ for 2 hours. After calcination, transfer it to a desiccator to cool to room temperature for later use.

[0075] S2: Mix 3g of anhydrous FeCl3 with 42g of anhydrous ethanol to prepare a loaded mixture. Add the loaded mixture dropwise to 36g of SBA-15 after calcination in step S1 and stir continuously until the loaded mixture is completely absorbed.

[0076] S3: Seal the SBA-15 that has absorbed the loaded mixture in step S2, let it stand at room temperature for 4 hours, and then transfer it to a vacuum drying oven at 60°C to dry for 12 hours.

[0077] S4: Transfer the dried solid powder to a crucible, place it in a muffle furnace, and heat it from room temperature to 300°C at a rate of 2°C / min under an air atmosphere. Then, calcine it at a constant temperature of 300°C for 3 hours. After calcination, allow it to cool naturally to below 80°C in the furnace. Then, remove it and transfer it to a desiccator, seal it, and cool it to room temperature to complete the preparation.

[0078] Phase 2: Preparation of 3,4-dichlorotrifluorotoluene Step 1: Add 500g of p-chlorotoluene, 10g of benzoyl peroxide, and 10g of N-hydroxyphthalimide to a reactor equipped with a UV LED lamp light source. After addition, turn on the UV LED lamp and stir. The wavelength of the UV LED lamp is 380nm, and the light intensity is 12W / m². 2The stirring rate was 500 rpm, the temperature was raised to 100°C, and chlorine gas was continuously introduced into the reactor at a rate of 0.13 L / min. After 8 hours of reaction, the chlorine gas was stopped, and the reactor was purged with nitrogen for 30 minutes. After purging, the heating was stopped and the reaction solution was cooled to room temperature. The reaction solution was washed three times with equal volumes of deionized water and then separated to obtain the lower organic phase of trichlorotoluene.

[0079] Step 2: 200g of p-chlorotrichlorotoluene and 460g of N-methylpyrrolidone obtained in step 1 were added to a reaction vessel. A fluorinating agent prepared by grinding and mixing 83.4g of tetrabutylammonium fluoride and 37.1g of potassium fluoride under a dry inert atmosphere was added to the reaction vessel. Then, 12g of copper powder-1,10-phenanthroline complex prepared by refluxing in ethanol at a molar ratio of 1:2 for 2 hours, filtering and drying was added to the reaction vessel. The mixture was stirred at 600 rpm and heated to 80°C for 2 hours. After the reaction was completed, the reaction solution was quenched in a mixture of 5 times its volume of ice and water. The organic phase was washed 3 times with an equal volume of saturated NaCl solution. After separation, the organic phase was dried with anhydrous magnesium sulfate for 30 minutes and then distilled under reduced pressure at 60°C and 2.5 kPa to obtain p-chlorotrichlorotoluene.

[0080] Step 3: 100g of p-chlorotrifluorotoluene obtained in step 2 and 5g of the catalyst prepared in the first stage were added to a flask. The mixture was preheated to 40°C under stirring. 82.2g of thioyl chloride was added dropwise to the flask using a dropping funnel at a rate of 2 drops / second. After the addition was complete, the reaction was continued for 3 hours. After the reaction was completed, the solid catalyst was separated by hot filtration and washed with anhydrous ethanol. The washed catalyst was transferred to a vacuum drying oven and dried at 80°C under vacuum for 4 hours before reuse. The remaining reaction solution was washed with 5% sodium bicarbonate solution until neutral. The organic phase was dried and then distilled at a pressure of 2.5 kPa and a temperature of 140°C to obtain the final product 3,4-dichlorotrifluorotoluene.

[0081] Example 3 A method for preparing 3,4-dichlorotrifluorotoluene specifically includes the following steps: Phase 1: Catalyst Preparation S1: Place 50g of mesoporous silica SBA-15 in a muffle furnace and calcine at 300℃ for 2 hours. After calcination, transfer it to a desiccator to cool to room temperature for later use.

[0082] S2: Mix 3g of anhydrous FeCl3 with 39g of anhydrous ethanol to prepare a loaded mixture. Add the loaded mixture dropwise to 33g of SBA-15 after calcination in step S1 and stir continuously until the loaded mixture is completely absorbed.

[0083] S3: Seal the SBA-15 that has absorbed the loaded mixture in step S2, let it stand at room temperature for 4 hours, and then transfer it to a vacuum drying oven at 60°C to dry for 12 hours.

[0084] S4: Transfer the dried solid powder to a crucible, place it in a muffle furnace, and heat it from room temperature to 300°C at a rate of 2°C / min under an air atmosphere. Then, calcine it at a constant temperature of 300°C for 3 hours. After calcination, allow it to cool naturally to below 80°C in the furnace. Then, remove it and transfer it to a desiccator, seal it, and cool it to room temperature to complete the preparation.

[0085] Phase 2: Preparation of 3,4-dichlorotrifluorotoluene Step 1: Add 500g of p-chlorotoluene, 7.5g of benzoyl peroxide, and 7.5g of N-hydroxyphthalimide to a reactor equipped with a UV LED lamp light source. After addition, turn on the UV LED lamp and stir. The wavelength of the UV LED lamp is 365nm, and the light intensity is 10W / m². 2 The stirring rate was 400 rpm, the temperature was raised to 90°C, and chlorine gas was continuously introduced into the reactor at a rate of 0.12 L / min. After 8 hours of reaction, the chlorine gas was stopped, and the reactor was purged with nitrogen for 30 minutes. After purging, the heating was stopped and the reaction solution was cooled to room temperature. The reaction solution was washed three times with equal volumes of deionized water and then separated to obtain the lower organic phase of trichlorotoluene.

[0086] Step 2: 200g of p-chlorotrichlorotoluene and 430g of N-methylpyrrolidone obtained in step 1 were added to a reaction vessel. A fluorinating agent prepared by grinding and mixing 81.9g of tetrabutylammonium fluoride and 36.4g of potassium fluoride under a dry inert atmosphere was added to the reaction vessel. Then, 11g of copper powder-1,10-phenanthroline complex prepared by refluxing in ethanol at a molar ratio of 1:2 for 2 hours, filtering and drying was added to the reaction vessel. The mixture was stirred at 500 rpm and heated to 80°C for 2 hours. After the reaction was completed, the reaction solution was quenched in a mixture of 4.5 times its volume of ice and water. The organic phase was washed three times with an equal volume of saturated NaCl solution. After separation, the organic phase was dried with anhydrous magnesium sulfate for 30 minutes and then distilled under reduced pressure at 55°C and 1.9 kPa to obtain p-chlorotrichlorotoluene.

[0087] Step 3: 100g of p-chlorotrifluorotoluene obtained in step 2 and 4g of the catalyst prepared in the first stage were added to a flask. The mixture was preheated to 40°C under stirring. 83.5g of thioyl chloride was added dropwise to the flask using a dropping funnel at a rate of 1.5 drops / second. After the addition was complete, the reaction was continued for 3 hours. After the reaction was completed, the solid catalyst was separated by hot filtration and washed with anhydrous ethanol. The washed catalyst was transferred to a vacuum drying oven and dried at 70°C under vacuum for 5 hours before reuse. The remaining reaction solution was washed with 5% sodium bicarbonate solution until neutral. The organic phase was dried and then distilled at a pressure of 1.9 kPa and a temperature of 130°C to obtain the final product 3,4-dichlorotrifluorotoluene.

[0088] Comparative Example 1 This comparative example is based on Example 3, with adjustments made to step 1 of the second stage. The ultraviolet LED lamp is not turned on during the reaction process. Specifically: Step 1: 500g of p-chlorotoluene, 7.5g of benzoyl peroxide, and 7.5g of N-hydroxyphthalimide were added to the reactor. After the addition was complete, stirring was started at a speed of 400 rpm. The temperature was raised to 90°C, and chlorine gas was continuously introduced into the reactor at a rate of 0.12 L / min. After the reaction was completed for 8 hours, the chlorine gas was stopped, and the reactor was purged with nitrogen for 30 minutes. After purging, the heating was stopped, and the reaction solution was cooled to room temperature. The reaction solution was washed three times with an equal volume of deionized water and then separated to obtain the lower organic layer of p-chlorotrichlorotoluene.

[0089] The remaining steps are exactly the same as in Example 3.

[0090] Comparative Example 2 This comparative example is based on Example 3, with adjustments made to step 2 of the second stage. Anhydrous hydrogen fluoride is used instead of the fluorinating reagent, and the copper powder-1,10-phenanthroline complex is no longer used. Specifically: Step 2: 200g of p-chlorotrichlorotoluene and 430g of N-methylpyrrolidone obtained in step 1 were added to a reaction vessel. 18.8g of anhydrous hydrogen fluoride was added to the reaction vessel. The mixture was stirred at 500 rpm and heated to 80°C for 2 hours. After the reaction was completed, the reaction solution was quenched in a mixture of 4.5 times its volume of ice and water. The organic phase was washed three times with an equal volume of saturated NaCl solution. After separation, the organic phase was dried with anhydrous magnesium sulfate for 30 minutes. The mixture was then distilled under reduced pressure at 55°C and 1.9 kPa to obtain p-chlorotrichlorotoluene.

[0091] The remaining steps are exactly the same as in Example 3.

[0092] Comparative Example 3 This comparative example is based on Example 3, but with adjustments made to step 3 of the second stage. Instead of using ferric chloride catalyst supported on mesoporous silica as the catalyst, FeCl3 is used directly as the catalyst. Specifically: Step 3: 100g of p-chlorotrifluorotoluene and 4g of FeCl3 obtained in step 2 were added to a flask and preheated to 40°C with stirring. 83.5g of thioyl chloride was added dropwise to the flask using a dropping funnel at a rate of 1.5 drops / second. After the addition was completed, the reaction was continued for 3 hours. The reaction solution was washed with 5% sodium bicarbonate solution until neutral, and the organic phase was dried. Then, it was distilled at a pressure of 1.9 kPa and a temperature of 130°C to obtain the final product 3,4-dichlorotrifluorotoluene.

[0093] The remaining steps are exactly the same as in Example 3.

[0094] According to the methods of the above embodiments and comparative examples, 3,4-dichlorotrifluorotoluene was prepared. During the preparation process, the yield and purity of steps 1, 2, and the final result were detected and recorded. The data are as follows:

[0095] Comparison and analysis of the above test data show that: Examples 1, 2, and 3 employed the optimized preparation conditions of this invention, including ultraviolet light excitation, composite fluorinating reagents, and supported catalysts.

[0096] Data shows that the yield of step 1 was between 91.45% and 93.87%, with a purity of 97.83% to 98.12%, indicating that the UV LED lamp can effectively promote the generation of chlorine free radicals, achieve efficient side-chain chlorination, and reduce the side reaction of benzene ring chlorination. The yield of step 2 was between 87.62% and 89.53%, with a purity of 96.91% to 97.25%, indicating that the tetrabutylammonium fluoride complex with potassium fluoride and the copper powder-1,10-phenanthroline complex can synergistically improve fluorination efficiency, ensuring high selectivity and mild reaction conditions. The yield of the final step was between 84.78% and 86.91%, with a purity of 98.95% to 99.12%, confirming that the ferric chloride catalyst supported on mesoporous silica can efficiently catalyze the electrophilic chlorination reaction to generate high-purity 3,4-dichlorotrifluorotoluene.

[0097] Overall, the yield and purity of the embodiments are high, and the repeatability is good, demonstrating the reliability and superiority of the method of the present invention.

[0098] In Comparative Example 1, the UV LED lamp was not turned on in step 1, resulting in a significant decrease in yield to 74.68% and purity to 94.77%. This indicates that UV light excitation is crucial for the generation of chlorine free radicals and the initiation of chain reactions. Without light, the reaction efficiency decreases and side reactions increase, thus affecting subsequent steps.

[0099] Although the conditions for steps 2 and 3 are the same as in Example 3, the low yield and low purity of step 1 resulted in a final yield of only 69.83%, lower than in the other examples. This highlights the crucial role of photochemical conditions in improving reaction selectivity and yield.

[0100] In Comparative Example 2, anhydrous hydrogen fluoride was used instead of the complex fluorinating reagent in step 2, and the copper powder-1,10-phenanthroline complex was not used. The yield in step 2 decreased to 77.59%, the purity decreased to 94.86%, and the final yield was 74.92%.

[0101] Anhydrous hydrogen fluoride, as a traditional fluorinating agent, can perform fluorination, but it suffers from problems such as strong corrosivity, dangerous operation, and difficulty in controlling reaction conditions, resulting in low fluorination efficiency and poor selectivity. In contrast, the composite fluorinating reagent and catalyst in the examples provide a milder and safer environment, promoting the nucleophilic attack of fluoride ions, thereby improving the yield and purity. The results of Comparative Example 2 confirm the advantages of the fluorination system of the present invention.

[0102] In Comparative Example 3, FeCl3 was used directly as a catalyst in step 3 instead of a supported catalyst. The yield in step 3 was significantly reduced, with a final yield of 71.75% and a purity of 95.87%.

[0103] Unsupported catalysts are prone to aggregation and poor dispersibility, leading to a reduction in active sites and an increase in side reactions, thereby decreasing yield and purity. In contrast, the supported catalysts in the examples exhibit high dispersibility and stability, effectively promoting the attack of chlorocations on specific positions of the benzene ring, thus improving selectivity and efficiency. The results of Comparative Example 3 highlight the importance of supported catalysts in the reaction.

[0104] The embodiments described above are not exhaustive and do not limit the invention to only certain specific embodiments. Clearly, many modifications and variations can be made based on the above description. These embodiments are selected and specifically described in this specification to better explain the principles and practical applications of the invention, thereby enabling those skilled in the art to effectively utilize the invention and its modifications. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the invention should be included within the scope of protection of the invention.

Claims

1. A method for preparing 3,4-dichlorotrifluorotoluene, characterized in that, Includes the following steps: Step 1: At a wavelength of 350–380 nm and an illumination intensity of 8–12 W / m 2 Under ultraviolet light irradiation, p-chlorotoluene was reacted with chlorine gas in the presence of benzoyl peroxide and N-hydroxyphthalimide at a reaction temperature of 80–100 °C and a chlorine gas introduction rate of 0.1–0.13 L / min for 8 hours to produce p-chlorotrichlorotoluene. Step 2: Add p-chlorotrichlorotoluene, a fluorinating agent composed of tetrabutylammonium fluoride and potassium fluoride in a molar ratio of 1:2, and copper powder-1,10-phenanthroline complex to the solvent N-methylpyrrolidone, and react at 80°C for 2 hours to generate p-chlorotrifluorotoluene. Step 3: Add p-chlorotrifluorotoluene, thioyl chloride and ferric chloride catalyst supported on mesoporous silica into a flask and react at 40°C for 3 hours to generate 3,4-dichlorotrifluorotoluene; The preparation method of the mesoporous silica-supported ferric chloride catalyst includes the following steps: S1: Calcine mesoporous silica at 300℃ for 2 hours; S2: Mix the calcined mesoporous silica with an ethanol solution of ferric chloride, wherein the mass ratio of ferric chloride, ethanol and mesoporous silica is 1:12-14:9-12; S3: After the mixed material has been left to stand at room temperature for 4 hours, it is transferred to a vacuum environment at 60°C and dried for 12 hours. S4: The dried material is heated to 300°C at a rate of 2°C / min in air and calcined at a constant temperature for 3 hours to obtain the catalyst.

2. The method for preparing 3,4-dichlorotrifluorotoluene according to claim 1, characterized in that, The mass ratio of p-chlorotoluene, benzoyl peroxide, and N-hydroxyphthalimide in step 1 is 100:1~2:1~2.

3. The method for preparing 3,4-dichlorotrifluorotoluene as described in claim 1, characterized in that, After the reaction in step 1 is completed, purge with nitrogen for 30 minutes to remove chlorine and hydrogen chloride.

4. The method for preparing 3,4-dichlorotrifluorotoluene according to claim 1, characterized in that, In step 2, the molar ratio of fluoride ions to p-chlorotrichlorotoluene in the fluorinating reagent is 1.05 to 1.1:

1.

5. The method for preparing 3,4-dichlorotrifluorotoluene according to claim 1, characterized in that, The mass of copper powder-1,10-phenanthroline complex added in step 2 is 5% to 6% of the mass of p-chlorotrichlorotoluene.

6. The method for preparing 3,4-dichlorotrifluorotoluene according to claim 1, characterized in that, The reaction in step 2 is carried out at a stirring speed of 400-600 rpm.

7. The method for preparing 3,4-dichlorotrifluorotoluene according to claim 1, characterized in that, After the reaction in step 2 is completed, the reaction solution is quenched by injecting it into a mixture of 4 to 5 times its volume of ice and water. The organic phase is washed three times with saturated NaCl solution, dried with anhydrous magnesium sulfate, and then subjected to vacuum distillation.

8. The method for preparing 3,4-dichlorotrifluorotoluene according to claim 1, characterized in that, The catalyst added in step 3 is 3% to 5% of the mass of p-chlorotrifluorotoluene, and the molar ratio of thioyl chloride to p-chlorotrifluorotoluene is 1.05 to 1.1:

1.

9. The method for preparing 3,4-dichlorotrifluorotoluene according to claim 1, characterized in that, After the reaction in step 3 is completed, the catalyst is separated by hot filtration, rinsed with anhydrous ethanol, and then vacuum dried at 60-80℃ for 4-6 hours for reuse. The reaction solution is washed with 5% sodium bicarbonate solution until neutral, and then vacuum distilled at 1.3-2.5 kPa and 120-140℃ to obtain the final product.

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