The invention relates to N, Napos; preparation method of-dichloro-1, 4-benzenedicarboxamide

Abstract

The invention relates to the technical field of organic synthesis, in particular to a preparation method of N, N '-dichloro-1, 4-benzenedicarboxamide, which comprises the following steps: taking terephthalamide as an initial raw material and tert-butyl hypochlorite as a chlorination reagent; the method comprises the following steps: carrying out a chlorination reaction on terephthalamide and tert-butyl hypochlorite in a solvent under the protection of inert gas by controlling the reaction temperature, and after the reaction is finished, carrying out post-treatment to obtain N, N-dichloro-1, 4-phthalimide. The preparation method of the N, N '-dichloro-1, 4-benzenedicarboxamide comprises the following steps: taking terephthalamide and tert-butyl hypochlorite as raw materials, and carrying out one-step reaction to generate a dichloro product. Compared with a traditional N, N '-dichloro-1, 4-benzenedicarboxamide production method, the preparation method has the advantages that the amount of three wastes generated is small, the product yield is high, the product purity is high, the operation is safe and convenient, and the preparation method is more suitable for industrial application.

Description

TECHNICAL FIELD

[0001] The application relates to a preparation method of N,N'-dichloro-1,4-benzene dicarboxamide and belongs to the technical field of organic synthesis. BACKGROUND

[0002] N,N'-dichloro-1,4-benzene dicarboxamide is also called N,N'-dichloro terephthalamide, is an important pesticide and pharmaceutical intermediate, N,N'-dichloro-1,4-benzene dicarboxamide is a white to white crystalline powder, and N,N'-dichloro-1,4-benzene dicarboxamide has the characteristics of releasing chlorine oxide, can be used as a mild bleaching agent in the industrial field of textiles, paper pulp and the like, and can be used to oxidize pigments by using the released hypochlorous acid. The structural formula of N,N'-dichloro-1,4-benzene dicarboxamide is as follows: .

[0003] In addition, the N-Cl bond in the N,N'-dichloro-1,4-benzene dicarboxamide molecule endows it with excellent chlorination ability, and can be used as a high-efficiency chlorinating agent to participate in various organic synthesis reactions, can accurately introduce chlorine atoms in pesticide and pharmaceutical synthesis, and reduce the generation of by-products. In practical application, it is used for synthesizing benzimidazole and thiocarbamate fungicides, effectively preventing and treating crop fungal diseases; as a key building block of antibacterial and antitumor drugs, such as chlorination modification of quinolone derivatives; can also be used as a green chlorinating agent for olefin addition and aromatic ring chlorination reaction, replacing traditional sulfuryl chloride. The patent application with the publication number US5319133A discloses a method for rearranging N,N'-dichloro terephthalamide and liquid alkali in oil-water two phases under the catalysis of quaternary ammonium salt at 0-60 DEG C to generate isocyanate. Therefore, it is very important to develop a preparation method for efficiently preparing N,N'-dichloro-1,4-benzene dicarboxamide.

[0004] At present, the synthesis method of N,N'-dichloro-1,4-benzene dicarboxamide mainly uses terephthalamide as a starting material, prepares a dilute solution by selecting polar solvents such as dichloromethane and DMF, passes chlorine gas at low temperature, stirs for about 4-8 hours, then filters, washes with cold water, and dries to obtain white solid. The traditional method involves simple equipment, is suitable for small-scale production, but the chlorination reaction is highly exothermic, and strict temperature control is required to prevent excessive chlorination; secondly, the utilization rate of chlorine gas is as low as about 50%, and the tail gas treatment cost is high; finally, the traditional method has low production efficiency, poor safety, and is difficult to scale up.

[0005] Chinese patent application CN102993026A discloses a preparation method of p-phenylenediamine, wherein the chlorination step uses terephthalamide as raw material, water as solvent, and generates N,N'-dichloro-terephthalamide through chlorination, and the chlorination product is used as raw material to generate p-phenylenediamine. However, the method continuously passes chlorine for 4-5 hours, which is dangerous and not suitable for continuous production.

[0006] A continuous preparation method of amine described in patent applications US4590292A, US5032687A, US5728873A and GB1257097A is to first add hypochlorite at low temperature (<20℃) to form N-chlorocarboxamide intermediate, and then add base to rearrange. The addition method reduces the hydrolysis of carboxamide before chlorination, but this method forms acylurea with low solubility and causes blockage of process pipelines and equipment. Moreover, the amount of hypochlorite used for chlorination directly affects the conversion rate and yield, and a small amount will cause incomplete conversion of carboxamide and low yield. On the contrary, an excess amount will cause excessive chlorination to generate N-chloroamine, which can subsequently decompose into nitrile or further react with amine product to form hydrazine, which cannot be well applied in industrialization.

[0007] Based on the problems in the prior art, it is of great value to find a preparation method of N,N'-dichloro-terephthalamide with high conversion rate, high safety and suitable for industrialization. SUMMARY

[0008] The present application aims at the problems of low chlorine utilization, low mass transfer efficiency and poor safety in the prior art, and provides a preparation method of N,N'-dichloro-terephthalamide, which is efficient, safe and suitable for industrialization.

[0009] The technical scheme for solving the above technical problems is as follows: a preparation method of N,N'-dichloro-terephthalamide, which comprises the following steps: using terephthalamide as starting raw material and tert-butyl hypochlorite as chlorination reagent; Under the protection of inert gas, the chlorination reaction of terephthalamide and tert-butyl hypochlorite is carried out in a solvent at a controlled reaction temperature, and after the reaction is completed, N,N'-dichloro-terephthalamide is obtained through post-treatment.

[0010] Further, the solvent is at least one of water, methanol, ethanol, acetonitrile and DMF.

[0011] Further, the chlorination reaction temperature is 5-30℃, and the chlorination reaction time is 1-5h.

[0012] Further, the molar ratio of the terephthalamide to the tert-butyl hypochlorite is 1: (2-4), and the mass ratio of the terephthalamide to the solvent is 1: (8-20).

[0013] Further, the preparation method comprises the following steps: dispersing the terephthalamide in the solvent to obtain an amide solution, controlling the temperature in the reaction system, slowly adding the tert-butyl hypochlorite into the system, and performing a chlorination reaction under stirring.

[0014] Further, the adding speed of the tert-butyl hypochlorite is 8-15 kg / h.

[0015] Further, the post-treatment operation comprises the following steps: after the reaction is completed, the reaction solution is added into a sodium thiosulfate aqueous solution to quench the reaction, and then the N, N'-dichloro-1, 4-terephthalic diamide is obtained through solid-liquid separation, solvent washing and vacuum drying; finally, the N, N'-dichloro-1, 4-terephthalic diamide is added into anhydrous solvent, and a hindered phenolic antioxidant is added for preservation, the water content in the anhydrous solvent is less than or equal to 50 ppm, and the anhydrous solvent is anhydrous acetonitrile.

[0016] Further, the concentration of the sodium thiosulfate aqueous solution is 0.9-1.2 mol / L, and the volume of the sodium thiosulfate aqueous solution is 1-5 times the volume of the reaction solution.

[0017] Further, the hindered phenolic antioxidant is at least one of dibutylhydroxytoluene and butylhydroxyanisole, and the mass concentration of the hindered phenolic antioxidant in the anhydrous solvent is 0.1%-1.0%.

[0018] Further, the mass concentration of the N, N'-dichloro-1, 4-terephthalic diamide in the anhydrous solvent is 3%-10%.

[0019] The beneficial effects of the present application are as follows: The preparation method of the N, N'-dichloro-1, 4-terephthalic diamide disclosed by the present application is to use terephthalamide and tert-butyl hypochlorite as raw materials to generate a dichloro product through one-step reaction. Compared with the traditional production method of N, N'-dichloro-1, 4-terephthalic diamide, the preparation method of the present application has the advantages of less waste, high product yield, high product purity, safe and convenient operation, and is more suitable for industrial application.

[0020] The preparation method of this invention uses tert-butyl hypochlorite as the chlorinating agent. The steric hindrance of the tert-butyl group in tert-butyl hypochlorite can reduce excessive chlorination or side reactions. Secondly, tert-butyl hypochlorite is a liquid reagent: compared to gaseous Cl2, t-BuOCl is a liquid (boiling point 79-80°C), which facilitates mass transfer. Furthermore, compared to the Cl2 reaction, the tert-butyl hypochlorite used in this invention can slowly release active chlorine, reducing the risk of violent exothermic reactions or explosions, and making the reaction process more controllable. The preparation method of this invention, by using tert-butyl hypochlorite as the chlorinating agent, combined with a suitable reaction temperature and material ratio, results in a high conversion rate and fewer side reactions in the reaction system, which is more conducive to obtaining high-yield, high-purity N,N'-dichloro-1,4-phenylenediamide products.

[0021] More preferably, the present invention achieves better results by using acetonitrile as the reaction solvent because acetonitrile can effectively dissolve terephthalamide (a polar amide) and tert-butyl hypochlorite (an organochlorine source), forming a homogeneous reaction system and avoiding side reactions (such as polychlorination or hydrolysis) caused by excessively high local concentrations. Furthermore, acetonitrile is stable against the strong oxidant tert-butyl hypochlorite, is not easily chlorinated or oxidized, and has fewer side reactions. Compared to alcohols (such as methanol), acetonitrile does not react with tert-butyl hypochlorite to form hypochlorous acid (HOCl), avoiding the risk of amide hydrolysis. Acetonitrile's high dielectric constant (… ε =37.5) helps to polarize tert-butyl hypochlorite, generating active chloride ions (Cl... + This selectively attacks the amide nitrogen (NH) ring rather than the benzene ring, increasing the yield of N-chloro products. Furthermore, compared to nonpolar solvents (such as dichloromethane), the reaction rate is faster in acetonitrile, making it particularly suitable for reactions involving nonpolar and moderately polar organic compounds, and reducing solid residues. Attached Figure Description

[0022] Figure 1 Schematic diagram of a continuous production unit for N,N'-dichloro-1,4-phenylenediamide; Figure 2 The gas phase detection chromatogram of the N,N'-dichloro-1,4-phenylenediamide product prepared in Example 1 is shown. Figure 3 The DTG diagram is shown for the N,N'-dichloro-1,4-phenylenediamide product prepared in Example 1. Figure 4 The NMR spectrometer of the N,N'-dichloro-1,4-phenylenediamide product prepared in Example 1. 1 H-NMR spectrum; Figure 5 The NMR spectrometer of the N,N'-dichloro-1,4-phenylenediamide product prepared in Example 1. 1 C-NMR spectrum; In the diagram, 1 is a phthalamide storage tank; 2 is a tert-butyl hypochlorite storage tank; 3 is a reaction vessel; 4 is a washing tank; 5 is a product collection tank; 6 is a filter; 7 is a condenser; and 8 is a distillation tank. Detailed Implementation

[0023] The specific embodiments of the present invention will be described in detail below. The present invention can be implemented in many other ways different from those described herein, and those skilled in the art can make similar modifications without departing from the spirit of the present invention. Therefore, the present invention is not limited to the specific embodiments disclosed.

[0024] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains. The terminology used is for describing particular embodiments only and is not intended to limit the invention.

[0025] A method for preparing N,N'-dichloro-1,4-phenylenediamide, wherein the preparation method comprises using terephthalamide as a starting material and tert-butyl hypochlorite as a chlorination reagent; Under inert gas protection, in a solvent, and with the reaction temperature controlled, tert-butyl hypochlorite was subjected to a chlorination reaction. After the reaction was completed, N,N-dichloro-1,4-phenylenediamide was obtained through post-treatment.

[0026] Specifically, the solvent is at least one of water, methanol, ethanol, acetonitrile, and DMF.

[0027] Preferably, the solvent is acetonitrile.

[0028] Specifically, the chlorination reaction temperature is 5-30℃, and the chlorination reaction time is 1-5h.

[0029] Preferably, the chlorination reaction temperature is 5-20℃ and the chlorination reaction time is 1.5-3h.

[0030] Specifically, the molar ratio of terephthalamide to tert-butyl hypochlorite is 1:(2-4); the mass ratio of terephthalamide to solvent is 1:(8-20).

[0031] Preferably, the molar ratio of terephthalamide to tert-butyl hypochlorite is 1:(2.5-4); and the mass ratio of terephthalamide to solvent is 1:(10-15).

[0032] Specifically, the preparation method is as follows: the terephthalamide is dispersed in the solvent to obtain an amide solution, the temperature in the reaction system is controlled, the tert-butyl hypochlorite is slowly added to the system, and a chlorination reaction is carried out under stirring conditions.

[0033] Specifically, the addition rate of tert-butyl hypochlorite is 8-15 kg / h.

[0034] Preferably, the addition rate of tert-butyl hypochlorite is 10-15 kg / h.

[0035] More specifically, when dispersing the terephthalamide in the solvent to obtain an amide solution, the stirring speed is 600-1000 rpm, preferably 600-800 rpm; the stirring speed during the chlorination reaction is 600-1000 rpm, preferably 300-500 rpm.

[0036] Specifically, the post-processing operation is as follows: after the reaction is completed, the reaction solution is added to an aqueous sodium thiosulfate solution to quench the reaction, and then the N,N'-dichloro-1,4-phenylenediamide is obtained by solid-liquid separation, solvent washing, and vacuum drying; finally, the N,N'-dichloro-1,4-phenylenediamide is added to an anhydrous solvent and a hindered phenolic antioxidant is added for preservation, wherein the water content in the anhydrous solvent is ≤50ppm.

[0037] More specifically, during the quenching reaction, the reaction solution was slowly added to an ice-bath-cooled sodium thiosulfate aqueous solution. After stirring for 15 minutes, the solution was tested with starch-KI paper; if it did not turn blue, it indicated the absence of free chlorine. The solution was then filtered, washed with acetonitrile, and vacuum dried to obtain the N,N'-dichloro-1,4-phenylenediamide.

[0038] More specifically, during washing, the acetonitrile temperature is 5-25℃, and the amount of acetonitrile used during washing is 10-15 times the theoretical product mass; preferably 5-10 times.

[0039] Specifically, the concentration of the sodium thiosulfate aqueous solution is 0.9-1.2 mol / L, and the volume of the sodium thiosulfate aqueous solution is 1-5 times the volume of the reaction liquid.

[0040] Preferably, the volume of the sodium thiosulfate aqueous solution is 1-3 times the volume of the reaction liquid.

[0041] Specifically, the hindered phenolic antioxidant is at least one of butylated hydroxytoluene and butylated hydroxyanisole, and the mass concentration of the hindered phenolic antioxidant in the anhydrous solvent is 0.1%-1.0%.

[0042] Preferably, the hindered phenolic antioxidant is butylated hydroxytoluene, and the mass concentration of the hindered phenolic antioxidant in the anhydrous solvent is 0.1%-0.5%.

[0043] Specifically, the mass concentration of N,N'-dichloro-1,4-phenylenediamide in the anhydrous solvent is 3%-10%.

[0044] Preferably, the N,N'-dichloro-1,4-phenylenediamide has a mass concentration of 5%-8% in the anhydrous solvent. More specifically, the anhydrous solvent used in the embodiments of the present invention is anhydrous acetonitrile (water content ≤50ppm).

[0045] Specifically, the filtrate obtained from solid-liquid separation in the post-processing can be recycled by distillation to recover the solvent.

[0046] More specifically, when acetonitrile is used as the solvent, the conditions for acetonitrile recovery are as follows: the filtrate is transported to a distillation tank, the temperature of which is maintained at 26-35℃ and the pressure at 50-100 mmHg. The acetonitrile is converted into a gas and distilled out from the gas outlet. It is then condensed into a liquid by a condenser at -10~-5℃ and returned to the acetonitrile storage tank for reuse through the liquid outlet. The acetonitrile recovery rate is 98%, and the remaining components in the distillation tank are inorganic salts.

[0047] The production apparatus used to prepare N,N'-dichloro-1,4-phenylenediamide according to the present invention is as follows: Figure 1 As shown, the production apparatus includes a terephthalamide storage tank 1, a tert-butyl hypochlorite storage tank 2, a reaction vessel 3, a washing tank 4, a product collection tank 5, a filter 6, a condenser 7, and a distillation tank 8. The terephthalamide storage tank 1 and the tert-butyl hypochlorite storage tank 2 are connected to the inlet of the reaction vessel 3 via pumps and pipelines. The reaction vessel 3 is also equipped with a quenching inlet. The outlet of the reaction vessel 3 is connected to the filter 6. The solid obtained by the filter 6 is added to the washing tank 4 for washing. The filtrate enters the distillation tank 8 through a pipeline. The outlet of the washing tank 4 is connected to the filter 6 again. The solid product obtained by the filter 6 enters the product collection tank 5 for storage. The filtrate enters the distillation tank 8. The distillation tank 8 is connected to the condenser 7 to condense and recover the solvent for reuse.

[0048] Example 1 A method for preparing N,N'-dichloro-1,4-phenylenediamide, wherein the preparation method comprises: (1) Premixing of amide solution: At room temperature, terephthalamide and acetonitrile are added to the reaction vessel and stirred to obtain amide solution; wherein the mass ratio of terephthalamide to acetonitrile is 1:10; (2) Chlorination reaction: Under nitrogen protection, tert-butyl hypochlorite was added to the reactor by a pump at a rate of 14.76 kg / h, wherein the molar ratio of terephthalamide to tert-butyl hypochlorite was 1:2.5; the reaction temperature was maintained at 10℃ and the reaction time was 2h.

[0049] (3) Post-processing: After chlorination, the product is white. The reaction solution is quenched in an ice-bath cooled sodium thiosulfate aqueous solution (concentration 1 mol / L), the volume of which is 4 times the volume of the reaction solution. The solution is then pumped to a filter for filtration. The filtered solid is washed with acetonitrile at 25°C, filtered, and vacuum dried to obtain the white product N,N'-dichloro-1,4-phenylenediamide, with a yield of 97% and a purity of 98.7%. The gas phase and DTG chromatograms of the N,N'-dichloro-1,4-phenylenediamide product are shown below. Figure 2 and Figure 3 As shown, the NMR detection spectrum is as follows: Figure 4 and Figure 5 As shown (NMR test conditions: deuterated DMSO as solvent, 400MHz).

[0050] (4) Storage: Dissolve N,N'-dichloro-1,4-phenylenediamide in anhydrous acetonitrile and add butylated hydroxytoluene, wherein the mass concentration of N,N'-dichloro-1,4-phenylenediamide in anhydrous acetonitrile is 6.9% and the mass concentration of butylated hydroxytoluene in anhydrous acetonitrile is 0.5%.

[0051] (5) Acetonitrile recovery: The filtrate after filtration is pumped to the distillation tank. The temperature of the distillation tank is maintained at 30℃ and the pressure is maintained at 100mmHg. Acetonitrile is converted into gas and distilled out from the gas outlet. It is condensed into liquid by the -5℃ condenser and reused through the liquid outlet. The acetonitrile recovery rate is 90%. The remaining components in the distillation tank are inorganic salts.

[0052] Example 2 A method for preparing N,N'-dichloro-1,4-phenylenediamide, wherein the preparation method comprises: (1) Premixing of amide solution: At room temperature, terephthalamide and acetonitrile are added to the reaction vessel and stirred to obtain amide solution; wherein the mass ratio of terephthalamide to acetonitrile is 1:12. (2) Chlorination reaction: Under nitrogen protection, tert-butyl hypochlorite was added to the reactor by a pump at a rate of 14.03 kg / h, wherein the molar ratio of terephthalamide to tert-butyl hypochlorite was 1:3; the reaction temperature was maintained at 5℃ and the reaction time was 1.5h.

[0053] (3) Post-processing: After chlorination, the product is white. The reaction solution is added to an ice bath-cooled sodium thiosulfate aqueous solution (concentration of 1 mol / L) for quenching. The volume of the sodium thiosulfate aqueous solution is 5 times the volume of the reaction solution. The product is then pumped to a filter for filtration. The solid obtained by filtration is washed with acetonitrile at 25°C, filtered, and vacuum dried to obtain the white product N,N'-dichloro-1,4-phenylenediamide. The yield is 99.5% and the product purity is 98.2%.

[0054] (4) Storage: Dissolve N,N'-dichloro-1,4-phenylenediamide in anhydrous acetonitrile and add butylated hydroxytoluene, wherein the mass concentration of N,N'-dichloro-1,4-phenylenediamide in anhydrous acetonitrile is 3% and the mass concentration of butylated hydroxytoluene in anhydrous acetonitrile is 0.5%.

[0055] (5) Acetonitrile recovery: The filtrate after filtration is pumped to the distillation tank. The temperature of the distillation tank is maintained at 35℃ and the pressure is maintained at 100mmHg. Acetonitrile is converted into gas and distilled out from the gas outlet. It is condensed into liquid by the -10℃ condenser and reused through the liquid outlet. The acetonitrile recovery rate is 95%. The remaining components in the distillation tank are inorganic salts.

[0056] Example 3 A method for preparing N,N'-dichloro-1,4-phenylenediamide, wherein the preparation method comprises: (1) Premixing of amide solution: At room temperature, terephthalamide and acetonitrile are added to the reaction vessel and stirred to obtain amide solution; wherein the mass ratio of terephthalamide to acetonitrile is 1:10; (2) Chlorination reaction: Under nitrogen protection, tert-butyl hypochlorite was added to the reactor by a pump at a rate of 12.66 kg / h, wherein the molar ratio of terephthalamide to tert-butyl hypochlorite was 1:4; the reaction temperature was maintained at 20℃ and the reaction time was 3h.

[0057] (3) Post-processing: After chlorination, the product is white. The reaction solution is added to an ice bath-cooled sodium thiosulfate aqueous solution (concentration of 1 mol / L) for quenching. The volume of the sodium thiosulfate aqueous solution is 3 times the volume of the reaction solution. The product is then pumped to a filter for filtration. The solid obtained by filtration is washed with acetonitrile at 25°C, filtered, and vacuum dried to obtain the white product N,N'-dichloro-1,4-phenylenediamide. The yield is 99.0% and the product purity is 98.5%.

[0058] (4) Storage: Dissolve N,N'-dichloro-1,4-phenylenediamide in anhydrous acetonitrile and add butylated hydroxytoluene, wherein the mass concentration of N,N'-dichloro-1,4-phenylenediamide in anhydrous acetonitrile is 10% and the mass concentration of butylated hydroxytoluene in anhydrous acetonitrile is 0.1%.

[0059] (5) Acetonitrile recovery: The filtrate after filtration is pumped to the distillation tank. The temperature of the distillation tank is maintained at 26℃ and the pressure is maintained at 50mmHg. Acetonitrile is converted into gas and distilled out from the gas outlet. It is condensed into liquid by the -10℃ condenser and reused through the liquid outlet. The acetonitrile recovery rate is 98%. The remaining components in the distillation tank are inorganic salts.

[0060] Example 4 A method for preparing N,N'-dichloro-1,4-phenylenediamide, wherein the preparation method comprises: (1) Premixing of amide solution: At room temperature, terephthalamide and acetonitrile are added to the reaction vessel and stirred to obtain amide solution; wherein the mass ratio of terephthalamide to acetonitrile is 1:15; (2) Chlorination reaction: Under nitrogen protection, tert-butyl hypochlorite was added to the reactor by a pump at a rate of 12.66 kg / h, wherein the molar ratio of terephthalamide to tert-butyl hypochlorite was 1:2; the reaction temperature was maintained at 25°C and the reaction time was 3 h.

[0061] (3) Post-processing: After chlorination, the product is white. The reaction solution is added to an ice bath-cooled sodium thiosulfate aqueous solution (concentration of 1 mol / L) for quenching. The volume of the sodium thiosulfate aqueous solution is twice the volume of the reaction solution. The product is then pumped to a filter for filtration. The solid obtained by filtration is washed with acetonitrile at 25°C, filtered, and vacuum dried to obtain the white product N,N'-dichloro-1,4-phenylenediamide. The yield is 94.0% and the purity is 98.3%.

[0062] (4) Storage: Dissolve N,N'-dichloro-1,4-phenylenediamide in anhydrous acetonitrile and add butylated hydroxytoluene, wherein the mass concentration of N,N'-dichloro-1,4-phenylenediamide in anhydrous acetonitrile is 9% and the mass concentration of butylated hydroxytoluene in anhydrous acetonitrile is 0.15%.

[0063] (5) Acetonitrile recovery: The filtrate after filtration is pumped to the distillation tank. The temperature of the distillation tank is maintained at 26℃ and the pressure is maintained at 50mmHg. Acetonitrile is converted into gas and distilled out from the gas outlet. It is condensed into liquid by the -10℃ condenser and reused through the liquid outlet. The acetonitrile recovery rate is 98%. The remaining components in the distillation tank are inorganic salts.

[0064] Example 5 A method for preparing N,N'-dichloro-1,4-phenylenediamide, wherein the preparation method comprises: (1) Premixing of amide solution: At room temperature, terephthalamide and methanol are added to the reaction vessel and stirred to obtain amide solution; wherein the mass ratio of terephthalamide to methanol is 1:20. (2) Chlorination reaction: Under nitrogen protection, tert-butyl hypochlorite was added to the reactor by a pump at a rate of 14.03 kg / h, wherein the molar ratio of terephthalamide to tert-butyl hypochlorite was 1:2.5; the reaction temperature was maintained at 5℃ and the reaction time was 2.0 h.

[0065] (3) Post-processing: After chlorination, the product is white. The reaction solution is added to an ice bath-cooled sodium thiosulfate aqueous solution (concentration of 1 mol / L) for quenching. The volume of the sodium thiosulfate aqueous solution is 1 times the volume of the reaction solution. The product is then pumped to a filter for filtration. The solid obtained by filtration is washed with acetonitrile at 25°C, filtered, and vacuum dried to obtain the white product N,N'-dichloro-1,4-phenylenediamide. The yield is 93.5% and the product purity is 98.0%.

[0066] (4) Storage: Dissolve N,N'-dichloro-1,4-phenylenediamide in anhydrous acetonitrile and add butylated hydroxytoluene, wherein the mass concentration of N,N'-dichloro-1,4-phenylenediamide in anhydrous acetonitrile is 3% and the mass concentration of butylated hydroxytoluene in anhydrous acetonitrile is 0.5%.

[0067] Example 6 A method for preparing N,N'-dichloro-1,4-phenylenediamide, wherein the preparation method comprises: (1) Premixing of amide solution: At room temperature, terephthalamide and DMF are added to the reaction vessel and stirred to obtain amide solution; wherein, the mass ratio of terephthalamide and DMF is 1:20; (2) Chlorination reaction: Under nitrogen protection, tert-butyl hypochlorite was added to the reactor by a pump at a rate of 15 kg / h, wherein the molar ratio of terephthalamide to tert-butyl hypochlorite was 1:2.5; the reaction temperature was maintained at 5℃ and the reaction time was 2.0 h.

[0068] (3) Post-processing: After chlorination, the product is white. The reaction solution is added to an ice bath-cooled sodium thiosulfate aqueous solution (concentration of 1 mol / L) for quenching. The volume of the sodium thiosulfate aqueous solution is 3 times the volume of the reaction solution. The product is then pumped to a filter for filtration. The solid obtained by filtration is washed with acetonitrile at 25°C, filtered, and vacuum dried to obtain the white product N,N'-dichloro-1,4-phenylenediamide. The yield is 93% and the product purity is 98.1%.

[0069] (4) Storage: Dissolve the N,N'-dichloro-1,4-phenylenediamide product in anhydrous acetonitrile and add butylated hydroxytoluene, wherein the mass concentration of N,N'-dichloro-1,4-phenylenediamide in anhydrous acetonitrile is 3.5% and the mass concentration of butylated hydroxytoluene in anhydrous acetonitrile is 0.5%.

[0070] Comparative Example 1 N,N'-dichloro-1,4-phenylenediamide was prepared using the same method as in Example 1, except that the reaction temperature in Comparative Example 1 was 35°C, which is higher than the temperature conditions specified in this invention. The specific preparation process is as follows: (1) Premixing of amide solution: At room temperature, terephthalamide and acetonitrile are added to the reaction vessel and stirred to obtain amide solution; wherein the mass ratio of terephthalamide to acetonitrile is 1:10; (2) Chlorination reaction: Under nitrogen protection, tert-butyl hypochlorite was added to the reactor by a pump at a rate of 14.76 kg / h, wherein the molar ratio of terephthalamide to tert-butyl hypochlorite was 1:2.5; the reaction temperature was maintained at 35℃ and the reaction time was 2h.

[0071] (3) Post-processing: After chlorination, the product is white. The reaction solution is added to an ice bath-cooled sodium thiosulfate aqueous solution (concentration of 1 mol / L) for quenching. The volume of the sodium thiosulfate aqueous solution is 4 times the volume of the reaction solution. The product is then pumped to a filter for filtration. The solid obtained by filtration is washed with acetonitrile at 25°C, filtered, and vacuum dried to obtain the white product N,N'-dichloro-1,4-phenylenediamide. The yield is 87% and the product purity is 95.6%.

[0072] (4) Storage: Dissolve N,N'-dichloro-1,4-phenylenediamide in anhydrous acetonitrile and add butylated hydroxytoluene, wherein the mass concentration of N,N'-dichloro-1,4-phenylenediamide in anhydrous acetonitrile is 6.9% and the mass concentration of butylated hydroxytoluene in anhydrous acetonitrile is 0.5%.

[0073] (5) Acetonitrile recovery: The filtrate after filtration is pumped to the distillation tank. The temperature of the distillation tank is maintained at 30℃ and the pressure is maintained at 100mmHg. Acetonitrile is converted into gas and distilled out from the gas outlet. It is condensed into liquid by the -5℃ condenser and reused through the liquid outlet. The acetonitrile recovery rate is 90%. The remaining components in the distillation tank are inorganic salts.

[0074] A comparison of the experimental results of Comparative Example 1 and Example 1 shows that if the reaction temperature is increased, the yield and purity of N,N'-dichloro-1,4-phenylenediamide products decrease significantly. This is because: (1) The N-Cl bond is a relatively weak bond, and heating provides the energy required for its breakage, resulting in homolytic cleavage and the generation of chlorine radicals (Cl•) and nitrogen-centered radicals. Cl• attacks the benzene ring with a high electron cloud density, resulting in free radical electrophilic substitution and generating chlorinated byproducts at different positions on the benzene ring; (2) Since the two highly reactive N-Cl groups are located at the para position of the benzene ring, under thermal drive, one N-Cl group can act as an electrophile to attack the nitrogen atom of the other amide (although the steric hindrance is large), resulting in intramolecular electrophilic ring closure; (3) Under alkaline or heating conditions, N-chloroamides may undergo rearrangement to generate isocyanate intermediates. The generated isocyanates are very reactive and will react with water in the system to revert to amines (-NH2), resulting in a "dechlorination" effect.

[0075] Comparative Example 2 N,N'-dichloro-1,4-phenylenediamide was prepared using the same method as in Example 1, except that the reaction temperature in Comparative Example 2 was -5°C, which is lower than the temperature conditions specified in this invention. The specific preparation process is as follows: (1) Premixing of amide solution: At room temperature, terephthalamide and acetonitrile are added to the reaction vessel and stirred to obtain amide solution; wherein the mass ratio of terephthalamide to acetonitrile is 1:10; (2) Chlorination reaction: Under nitrogen protection, tert-butyl hypochlorite was added to the reactor by a pump at a rate of 14.76 kg / h, wherein the molar ratio of terephthalamide to tert-butyl hypochlorite was 1:2.5; the reaction temperature was maintained at -5℃ and the reaction time was 2h.

[0076] (3) Post-processing: After chlorination, the product is white. The reaction solution is added to an ice bath-cooled sodium thiosulfate aqueous solution (concentration of 1 mol / L) for quenching. The volume of the sodium thiosulfate aqueous solution is 4 times the volume of the reaction solution. The product is then pumped to a filter for filtration. The solid obtained by filtration is washed with acetonitrile at 25°C, filtered, and vacuum dried to obtain the white product N,N'-dichloro-1,4-phenylenediamide. The yield is 74% and the product purity is 97.6%.

[0077] (4) Storage: Dissolve N,N'-dichloro-1,4-phenylenediamide in anhydrous acetonitrile and add butylated hydroxytoluene, wherein the mass concentration of N,N'-dichloro-1,4-phenylenediamide in anhydrous acetonitrile is 6.9% and the mass concentration of butylated hydroxytoluene in anhydrous acetonitrile is 0.5%.

[0078] (5) Acetonitrile recovery: The filtrate after filtration is pumped to the distillation tank. The temperature of the distillation tank is maintained at 30℃ and the pressure is maintained at 100mmHg. Acetonitrile is converted into gas and distilled out from the gas outlet. It is condensed into liquid by the -5℃ condenser and reused through the liquid outlet. The acetonitrile recovery rate is 90%. The remaining components in the distillation tank are inorganic salts.

[0079] A comparison of the experimental results from Comparative Example 2 and Example 1 shows that lowering the reaction temperature significantly reduces the yield of N,N'-dichloro-1,4-phenylenediamide. This is because lower temperatures indiscriminately reduce the chemical reaction rate, and at certain temperatures, the main reaction becomes kinetically limited and difficult to proceed effectively. Furthermore, even with prolonged reactions, unreacted terephthalamide or monochloro intermediates may still be detected in the reaction solution. The product is a mixture of monochloro and dichloro products, resulting in lower purity and yield. Therefore, the temperature conditions specified in this invention are more conducive to obtaining high-purity, high-yield products.

[0080] Comparative Example 3 N,N'-dichloro-1,4-phenylenediamide was prepared using the same method as in Example 1, except that the proportion of tert-butyl hypochlorite was increased in Comparative Example 3, with a molar ratio of tert-butyl hypochlorite to tert-butyl hypochlorite of 1:6. The specific preparation process is as follows: (1) Premixing of amide solution: At room temperature, terephthalamide and acetonitrile are added to the reaction vessel and stirred to obtain amide solution; wherein the mass ratio of terephthalamide to acetonitrile is 1:10; (2) Chlorination reaction: Under nitrogen protection, tert-butyl hypochlorite was added to the reactor by a pump at a rate of 14.76 kg / h, wherein the molar ratio of terephthalamide to tert-butyl hypochlorite was 1:6; the reaction temperature was maintained at 10℃ and the reaction time was 2h.

[0081] (3) Post-processing: After chlorination, the product is white. The reaction solution is added to an ice bath-cooled sodium thiosulfate aqueous solution (concentration of 1 mol / L) for quenching. The volume of the sodium thiosulfate aqueous solution is 4 times the volume of the reaction solution. The product is then pumped to a filter for filtration. The solid obtained by filtration is washed with acetonitrile at 25°C, filtered, and vacuum dried to obtain the white product N,N'-dichloro-1,4-phenylenediamide. The yield is 90% and the product purity is 95.7%.

[0082] (4) Storage: Dissolve N,N'-dichloro-1,4-phenylenediamide in anhydrous acetonitrile and add butylated hydroxytoluene, wherein the mass concentration of N,N'-dichloro-1,4-phenylenediamide in anhydrous acetonitrile is 6.9% and the mass concentration of butylated hydroxytoluene in anhydrous acetonitrile is 0.5%.

[0083] (5) Acetonitrile recovery: The filtrate after filtration is pumped to the distillation tank. The temperature of the distillation tank is maintained at 30℃ and the pressure is maintained at 100mmHg. Acetonitrile is converted into gas and distilled out from the gas outlet. It is condensed into liquid by the -5℃ condenser and reused through the liquid outlet. The acetonitrile recovery rate is 90%. The remaining components in the distillation tank are inorganic salts.

[0084] A comparison of the experimental results from Comparative Example 3 and Example 1 shows that increasing the amount of tert-butyl hypochlorite significantly reduces the yield of the N,N'-dichloro-1,4-phenylenediamide product. This is because tert-butyl hypochlorite is not only an N-position chlorinating agent but also a strong oxidizing and alkylating agent. Excessive amounts can lead to tert-butylation and over-oxidation of the benzene ring, generating complex byproducts that severely reduce the purity and yield of the target product. Therefore, using the proportions specified in this invention is more conducive to obtaining high-purity, high-yield products.

[0085] Comparative Example 4 The N,N'-dichloro-1,4-phenylenediamide product was prepared using the same method as in Example 1, except that dichloromethane was used as the solvent in Comparative Example 4. The specific preparation process is as follows: (1) Premixing of amide solution: At room temperature, terephthalamide and dichloromethane are added to the reaction vessel and stirred to obtain an amide solution; wherein the mass ratio of terephthalamide to dichloromethane is 1:10; (2) Chlorination reaction: Under nitrogen protection, tert-butyl hypochlorite was added to the reactor by a pump at a rate of 14.76 kg / h, wherein the molar ratio of terephthalamide to tert-butyl hypochlorite was 1:2.5; the reaction temperature was maintained at 10℃ and the reaction time was 2h.

[0086] (3) Post-processing: After chlorination, the product is white. The reaction solution is added to an ice bath-cooled sodium thiosulfate aqueous solution (concentration of 1 mol / L) for quenching. The volume of the sodium thiosulfate aqueous solution is 4 times the volume of the reaction solution. The product is then pumped to a filter for filtration. The solid obtained by filtration is washed with acetonitrile at 25°C, filtered, and vacuum dried to obtain the white product N,N'-dichloro-1,4-phenylenediamide. The yield is 85% and the product purity is 96.9%.

[0087] (4) Storage: Dissolve N,N'-dichloro-1,4-phenylenediamide in anhydrous acetonitrile and add butylated hydroxytoluene, wherein the mass concentration of N,N'-dichloro-1,4-phenylenediamide in anhydrous acetonitrile is 6.9% and the mass concentration of butylated hydroxytoluene in anhydrous acetonitrile is 0.5%.

[0088] (5) Acetonitrile recovery: The filtrate after filtration is pumped to the distillation tank. The temperature of the distillation tank is maintained at 30℃ and the pressure is maintained at 100mmHg. Acetonitrile is converted into gas and distilled out from the gas outlet. It is condensed into liquid by the -5℃ condenser and reused through the liquid outlet. The acetonitrile recovery rate is 90%. The remaining components in the distillation tank are inorganic salts.

[0089] The comparison of the experimental results of Comparative Example 4 and Example 1 shows that the present invention has better results by using acetonitrile as the reaction solvent, because acetonitrile can dissolve terephthalamide (polar amide) and tert-butyl hypochlorite (organochlorine source) well to form a homogeneous reaction system and avoid side reactions (such as polychlorination or hydrolysis) caused by excessively high local concentrations.

[0090] Comparative Example 5 The N,N'-dichloro-1,4-phenylenediamide product was prepared using the conventional chlorine gas method. The specific preparation process is as follows: N,N'-dichloro-1,4-phenylenediamide was prepared using the same method as in Example 1, except that the reaction temperature in Comparative Example 1 was 35°C, which is higher than the temperature conditions specified in this invention. The specific preparation process is as follows: (1) Premixing of amide solution: At room temperature, terephthalamide and acetonitrile are added to the reaction vessel and stirred to obtain amide solution; wherein the mass ratio of terephthalamide to acetonitrile is 1:10; (2) Chlorination reaction: Under nitrogen protection, chlorine gas is introduced into the reactor, wherein the molar ratio of terephthalamide to hypochlorite is 1:6; the reaction temperature is maintained at 35℃ and the reaction time is 2h.

[0091] (3) Post-processing: After chlorination, the product is white. The reaction solution is added to an ice bath-cooled sodium thiosulfate aqueous solution (concentration of 1 mol / L) for quenching. The volume of the sodium thiosulfate aqueous solution is 4 times the volume of the reaction solution. The product is then pumped to a filter for filtration. The solid obtained by filtration is washed with acetonitrile at 25°C, filtered, and vacuum dried to obtain the white product N,N'-dichloro-1,4-phenylenediamide. The yield is 90% and the product purity is 97%.

[0092] (4) Storage: Dissolve N,N'-dichloro-1,4-phenylenediamide in anhydrous acetonitrile and add butylated hydroxytoluene, wherein the mass concentration of N,N'-dichloro-1,4-phenylenediamide in anhydrous acetonitrile is 6.9% and the mass concentration of butylated hydroxytoluene in anhydrous acetonitrile is 0.5%.

[0093] (5) Acetonitrile recovery: The filtrate after filtration is pumped to the distillation tank. The temperature of the distillation tank is maintained at 30℃ and the pressure is maintained at 100mmHg. Acetonitrile is converted into gas and distilled out from the gas outlet. It is condensed into liquid by the -5℃ condenser and reused through the liquid outlet. The acetonitrile recovery rate is 90%. The remaining components in the distillation tank are inorganic salts.

[0094] A comparison of the experimental results from Comparative Example 5 and Examples 1-6 shows that, using chlorine as the chlorination reagent, an excess of over 120% of chlorine is required to achieve a product yield of 90%. Furthermore, the excess chlorine needs to be recovered and reused during production, increasing energy consumption and equipment costs. Therefore, the preparation method described in this invention, using terephthalamide as the starting material and tert-butyl hypochlorite as the chlorination reagent, along with suitable temperature, ratio, and solvent conditions, is more conducive to obtaining a high-yield, high-purity N,N'-dichloro-1,4-phenylenediamide product.

[0095] The technical features of the above embodiments can be combined in any way. For the sake of brevity, not all possible combinations of the technical features in the above embodiments are exhaustively listed. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0096] For those skilled in the art, various modifications and improvements can be made without departing from the concept of the present invention, and these modifications and improvements are all within the scope of protection of the present invention. The scope of protection of the present invention is defined by the appended claims.

Claims

1. A method for preparing N,N'-dichloro-1,4-phenylenediamide, characterized in that, The preparation method is as follows: using terephthalamide as the starting material and tert-butyl hypochlorite as the chlorination reagent; Under inert gas protection, in a solvent, and with the reaction temperature controlled, tert-butyl hypochlorite was subjected to a chlorination reaction. After the reaction was completed, N,N-dichloro-1,4-phenylenediamide was obtained through post-treatment.

2. The method for preparing N,N'-dichloro-1,4-phenylenediamide according to claim 1, characterized in that, The solvent is at least one of water, methanol, ethanol, acetonitrile, and DMF.

3. The method for preparing N,N'-dichloro-1,4-phenylenediamide according to claim 1, characterized in that, The chlorination reaction temperature is 5-30℃, and the chlorination reaction time is 1-5h.

4. The method for preparing N,N'-dichloro-1,4-phenylenediamide according to claim 1, characterized in that, The molar ratio of terephthalamide to tert-butyl hypochlorite is 1:(2-4); the mass ratio of terephthalamide to solvent is 1:(8-20).

5. The method for preparing N,N'-dichloro-1,4-phenylenediamide according to claim 1, characterized in that, The preparation method is as follows: the terephthalamide is dispersed in the solvent to obtain an amide solution, the temperature in the reaction system is controlled, the tert-butyl hypochlorite is slowly added to the system, and the chlorination reaction is carried out under stirring conditions.

6. The method for preparing N,N'-dichloro-1,4-phenylenediamide according to claim 5, characterized in that, The addition rate of tert-butyl hypochlorite is 8-15 kg / h.

7. The method for preparing N,N'-dichloro-1,4-phenylenediamide according to claim 1, characterized in that, The post-processing operation is as follows: after the reaction is completed, the reaction solution is added to an aqueous sodium thiosulfate solution to quench the reaction, and then the N,N'-dichloro-1,4-phenylenediamide is obtained by solid-liquid separation, solvent washing, and vacuum drying; finally, N,N'-dichloro-1,4-phenylenediamide is added to an anhydrous solvent and a hindered phenolic antioxidant is added for preservation. The water content in the anhydrous solvent is ≤50ppm, and the anhydrous solvent is anhydrous acetonitrile.

8. The method for preparing N,N'-dichloro-1,4-phenylenediamide according to claim 7, characterized in that, The concentration of the sodium thiosulfate aqueous solution is 0.9-1.2 mol / L, and the volume of the sodium thiosulfate aqueous solution is 1-5 times the volume of the reaction liquid.

9. The method for preparing N,N'-dichloro-1,4-phenylenediamide according to claim 7, characterized in that, The hindered phenolic antioxidant is at least one of butylated hydroxytoluene and butylated hydroxyanisole, and the mass concentration of the hindered phenolic antioxidant in the anhydrous solvent is 0.1%-1.0%.

10. The method for preparing N,N'-dichloro-1,4-phenylenediamide according to claim 7, characterized in that, The mass concentration of N,N'-dichloro-1,4-phenylenediamide in the anhydrous solvent is 3%-10%.

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