Synthesis method of pyridine biphenyl derivative

Abstract

The invention discloses a synthesis method of a pyridine biphenyl derivative, which comprises the following steps: in a micro-positive pressure nitrogen environment, carrying out coupling reaction on 3-bromo-5-nitropyridine and 4-hydroxy-4 '-nitrobiphenyl in a dehydration solvent; (4) feeding and catalyzing in stages: firstly adding a multifunctional metal chelating agent and a hydrogen catalyst, then adding a sodium dihydrogen phosphate buffering agent and an EDTMPA chelating agent in two stages, and respectively reacting at 0.3-1.1 MPa / 35-45 DEG C and 1.2-1.9 MPa / 55-65 DEG C; and (5) combining ethanol-normal hexane anti-solvent precipitation with gradient cooling crystallization purification to finally obtain the target product with the purity of greater than or equal to 98.95% and the yield of greater than or equal to 94.55%. The method simplifies the synthesis steps, solves the problems of difficult catalyst recovery, many byproducts and high energy consumption in the traditional process, is suitable for industrial mass production, has a wide application range, and obviously improves the vulcanization speed of insoluble sulfur.

Description

Technical Field

[0001] This invention relates to a method for synthesizing a pyridine biphenyl derivative, belonging to the field of organic synthesis technology. Background Technology

[0002] The information disclosed in this background section is intended only to enhance some understanding of the overall background of the invention and is not necessarily to be construed as an admission or in any way implying that the information constitutes prior art known to those skilled in the art.

[0003] Pyridine-biphenyl derivatives are an important class of heterocyclic aromatic compounds. Their molecular structure consists of a pyridine ring (a nitrogen-containing six-membered heterocycle) and a biphenyl group linked by covalent bonds, exhibiting significant π-π conjugation and a rigid planar structure. The core characteristic of these compounds lies in the coordination ability provided by the nitrogen atom of the pyridine ring, while the biphenyl moiety provides hydrophobicity and steric extension. By modifying the substitution sites of the pyridine ring (such as the 2-, 3-, and 4- positions) or the functional groups on the biphenyl group (such as halogens, alkyl groups, and carboxyl groups), their electron distribution, solubility, and intermolecular interactions can be controlled. In application fields, pyridine biphenyl derivatives are widely used due to their unique properties: 1) Optoelectronic materials, as electron transport or light-emitting layer materials for organic light-emitting diodes (OLEDs), such as 4-(4-pyridyl)biphenyl, which can improve device efficiency; 2) Pharmaceutical chemistry, where their structure can serve as pharmacophores for kinase inhibitors or antibacterial agents, for example, some derivatives exhibit antitumor activity; 3) Coordination chemistry, as ligands for metal-organic frameworks (MOFs) for gas adsorption or catalytic reactions; 4) Analytical detection, using fluorescence properties for sensing heavy metal ions or biomolecules; 5) Pesticide development, where some derivatives have insecticidal or herbicidal efficacy. Furthermore, they also have potential value in liquid crystal materials, corrosion inhibitors, and polymer modification. Current research focuses on balancing their stability and functionality through structural optimization and exploring green synthetic pathways to promote industrial applications. Overall, pyridine biphenyl derivatives represent a multifunctional molecular platform with strong structural designability and broad interdisciplinary application prospects.

[0004] Although pyridine biphenyl derivatives have broad application potential, there are few reports on them, and the following technical drawbacks remain: 1) High synthesis difficulty, with some derivatives requiring multiple reaction steps, resulting in low yields and difficult purification, especially since sterically hindered substituents may reduce reaction efficiency; 2) Limited solubility, due to the polar contradiction between the rigid biphenyl structure and the pyridine ring, resulting in poor dispersibility in some solvents, affecting processing performance; 3) High cost, increasing the cost of industrial production. These drawbacks restrict their large-scale production and application, therefore a novel synthetic method for pyridine biphenyl derivatives is needed to overcome these shortcomings. Summary of the Invention

[0005] To address the shortcomings of existing technologies, the present invention aims to provide a method for synthesizing pyridine biphenyl derivatives. This method features high reaction rate, few byproducts, mild conditions, and the ability to repeatedly recover and reuse catalysts and solvents. It is suitable for large-scale industrial production, has a wide range of applications, and significantly improves the sulfidation rate of insoluble sulfur.

[0006] The technical solution adopted in this invention is as follows: In a first aspect of the present invention, a method for synthesizing a pyridine biphenyl derivative is provided, the method comprising the following steps: 3-Bromo-5-nitropyridine and 4-hydroxy-4'-nitrobiphenyl were added sequentially to a solvent, heated and stirred until dissolved, and then transferred to a reaction vessel. A premixed catalyst was added to the reaction vessel, and the temperature was raised to 80-90°C. A slightly positive nitrogen pressure was maintained throughout the reaction. After 5-7 hours of reaction, a multifunctional metal chelating agent was added and stirred for 5-15 minutes, followed by the addition of a hydrogenation catalyst. Different amounts of hydrogen were introduced in stages one and two (using a hydrogen cylinder as the gas source, with the flow rate precisely controlled via a pressure reducing valve and gas pipe) to carry out the reaction. In both stages one and two, buffers and organophosphonic acid chelating agents were added. After the staged reactions were completed, the reaction solution was drained, filtered, and the catalyst was washed multiple times with HCl / ethanol solution for easy reuse. The mother liquor was dissolved in ethanol at 40-50℃ and added dropwise to ice-cold n-hexane. After filtration, the crude product was dissolved in an ethanol-water solution at 60-70℃, and the temperature was gradually lowered. Finally, it was washed with pre-cooled ethanol-water (0-4℃) under vacuum, desorbed under low temperature vacuum, and dried under vacuum to obtain the final product, namely the pyridine biphenyl derivative, whose chemical structure is as follows: .

[0007] In this invention, the synthesis method involves the following two chemical reaction formulas: ; .

[0008] Preferably, the solvent is a product that has been dehydrated by molecular sieve and baked in a reaction vessel to remove moisture. The solvent is one or more of methanol, IPA (isopropanol), DMF, NMP, DMSO, and 1,3-dimethyl-2-imidazolinone; more preferably, the solvent is a mixed solvent composed of NMP and IPA, with a preferred mass ratio of 3:1 to 4:1.

[0009] Preferably, the mass ratio of 3-bromo-5-nitropyridine to solvent is 1:6.5-11.5; more preferably, the mass ratio of 3-bromo-5-nitropyridine to solvent is 1:8.0-10.0.

[0010] Preferably, the catalyst is a composite catalytic system, which uses CuI as a copper source and L-proline as a co-catalyst; the amount of CuI is 5-7% of the mass of 3-bromo-5-nitropyridine, and the mass ratio of CuI to L-proline is 1:1.21-1.82; more preferably, the mass ratio of CuI to L-proline is 1:1.45-1.70.

[0011] Preferably, the multifunctional metal chelating agent is one of disodium EDTA, DTPA (diethylenetriaminepentaacetic acid), EDDS (ethylenediaminedisuccinic acid), and CDTA (1,2-cyclohexanediaminetetraacetic acid); the amount used is 1.0-3.0% of the mass of 3-bromo-5-nitropyridine; more preferably, the amount used is 2.0-2.9% of the mass of 3-bromo-5-nitropyridine.

[0012] Preferably, the organophosphonic acid chelating agent is one of HEDP (hydroxyethylidene diphosphonic acid), ATMP (aminotrimethylenephosphonic acid), DTPMPA (diethylenetriaminepentamethylenephosphonic acid), and EDTMPA, and its dosage is 1.5-3.5% of the mass of 3-bromo-5-nitropyridine; it is added in stages, with 30-70% of the total amount added in stage one and the remaining amount of organophosphonic acid chelating agent added in stage two; more preferably, its dosage is 2.5-3.5% of the mass of 3-bromo-5-nitropyridine, and it is added in stages, with 40-60% of the total amount added in stage one and 40-55% of the total amount added in stage two.

[0013] Preferably, the buffer is sodium dihydrogen phosphate buffer, adjusted to pH 6.5-7.0, and its amount is 15-35% of the mass of 3-bromo-5-nitropyridine, added in stages, with 30-80% of the total amount added in stage one and the remaining amount added in stage two; preferably, the molar ratio of 3-bromo-5-nitropyridine to 4-hydroxy-4'-nitrobiphenyl is 1:1.02-1.15; more preferably, the molar ratio of 3-bromo-5-nitropyridine to 4-hydroxy-4'-nitrobiphenyl is 1:1.05-1.10.

[0014] Preferably, the hydrogenation catalyst is a supported bimetallic core-shell structure catalyst, which is a Pd-Fe@C magnetic catalyst, and its amount accounts for 0.8-1.7% of the mass of 3-bromo-5-nitropyridine; more preferably, its amount accounts for 1.0-1.5% of the mass of 3-bromo-5-nitropyridine.

[0015] Preferably, the HCl / ethanol solution (HCl (5% v / v) to ethanol volume ratio 1:3) is 2-10 times the mass of the hydrogenation catalyst; the volume ratio of ethanol to mother liquor at 40-50℃ is 2.1-7.7:1; the volume ratio of glacial hexane to mother liquor is 13.4-32.2:1, and the dropping rate is 1-10 ml / min; the mass ratio of ethanol-water solution to product at 60-70℃ is 5.7-10.1:1 (ethanol:water mass ratio is 7:3); pre-cooled ethanol-water (0-4℃) washing (mass ratio of ethanol:water = 8:2) is used in an amount 1-9 times the product volume.

[0016] The HCl / ethanol solution is specifically used for washing and regenerating the hydrogenation catalyst; hydrochloric acid dissolves oxides or adsorbates on the iron surface, restoring the active sites of the metal; ethanol, as a polar solvent, removes non-polar organic impurities while avoiding the introduction of water that could lead to catalyst sintering.

[0017] More preferably, the HCl / ethanol solution (HCl (5% v / v) to ethanol volume ratio 1:3) is 3-7 times the mass of the hydrogenation catalyst; the volume ratio of ethanol to mother liquor at 40-50℃ is 3.5-6.5:1; the volume ratio of glacial hexane to mother liquor is 15.5-25.5:1, and the dropping rate is 2-7 ml / min; the mass ratio of ethanol-water solution to product at 60-70℃ is 7.0-9.5:1 (ethanol:water mass ratio is 7:3); pre-cooled ethanol-water (0-4℃) washing (mass ratio of ethanol:water = 8:2) is used in an amount 1-7 times the product volume.

[0018] Preferably, in the staged reaction, the hydrogen pressure in stage one is 0.3-1.1 MPa, the temperature is 35-45°C, and the time is 0.5-1.5 h, and the hydrogen pressure in stage two is 1.2-1.9 MPa, the temperature is 55-65°C, and the time is 2.5-3.5 h; more preferably, the pressure in stage one is 0.5-0.9 MPa, and the pressure in stage two is 1.3-1.7 MPa.

[0019] Preferably, the gradient cooling first cools to 25°C at a cooling rate of 1.0-6.0°C / min, and then cools to 0-4°C at a cooling rate of 0.1-1.0°C / min; more preferably, it first cools to 25°C at a cooling rate of 1.0-4.0°C / min, and then cools to 0-4°C at a cooling rate of 0.3-0.7°C / min.

[0020] In a second aspect of the invention, the above method is applied in the preparation of rubber vulcanization accelerators.

[0021] Compared with the related technologies known to the inventors, one of the technical solutions of the present invention has the following beneficial effects: 1. This product has a rigid biphenyl skeleton + flexible ether bond + double amino electron-withdrawing group, which makes the compound have high thermal stability, modifiability and functional tunability; the advantages of low volatility, optimized solubility and low surface energy are coordinated and combined, making it suitable for the modification of composite materials and polymer materials.

[0022] 2. The mixed solvent used in this scheme can effectively enhance molecular diffusion and reaction uniformity; the Cu-catalyzed CO coupling product can be directly used as a Pd catalytic substrate, avoiding intermediate separation and shortening the reaction path by 50%; pH and metal ion concentration are linked for regulation, achieving the dual goals of inhibiting side reactions and accelerating the main reaction; through the four-level synergy of solvent-catalyst-additive-purification, high yield, high purity and low cost are achieved.

[0023] 3. This invention uses a one-pot method to prepare pyridine biphenyl derivatives. The coupling reaction and nitro reduction are connected in series in a one-pot process, which solves the technical problems of low yield, insufficient purity and large catalyst loss in the reaction of nitro compounds, and has significant industrial application value.

[0024] 4. The compound contains amino and pyridine groups, which can accelerate the vulcanization reaction and improve vulcanization efficiency, thereby resulting in a higher degree of vulcanization. These active groups play a catalytic role in the vulcanization process, promoting the cross-linking of sulfur and rubber molecular chains, thereby improving the physical properties of rubber. Detailed Implementation

[0025] It should be noted that the following detailed descriptions are exemplary and intended to provide further illustration of the invention. Unless otherwise specified, 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.

[0026] It should be noted that the terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit the exemplary embodiments of the present invention. As used herein, the singular form is intended to include the plural form as well, unless the context clearly indicates otherwise. Furthermore, it should be understood that when the terms "comprising" and / or "including" are used in this specification, they indicate the presence of features, steps, operations, and / or combinations thereof.

[0027] In one or more embodiments of the present invention, premixed and ground CuI / L-proline is used in synergy with a Pd-Fe@C magnetic catalyst. The former catalyzes the CO coupling reaction, while the latter enhances the Pd activity through Fe³⁺ electronic regulation, achieving continuous catalysis of CC coupling and nitro reduction, thus improving the reaction efficiency by 32%. Staged pressure-temperature control, combined with a gradient addition of EDTMPA chelating agent, improves product selectivity to 98.95%. Precipitation using ice-cold hexane as an antisolvent (3 mL / min) further enhances the reaction efficiency. The impurity encapsulation rate was reduced by 67% through a gradient cooling crystallization process (1.5℃ / min → 0.3℃ / min). NMP / IPA was dehydrated by molecular sieve and baked at 120℃ for 2 hours to reduce the moisture content to <50ppm, thus reducing side reactions by 90%. Finally, the efficient synthesis of 3-bromo-5-nitropyridine and 4-hydroxy-4'-nitrobiphenyl was achieved. The catalyst can be recycled multiple times after washing with HCl / ethanol, solving the problems of difficult recovery, numerous by-products, and high energy consumption in traditional processes, and making it suitable for continuous industrial production.

[0028] To enable those skilled in the art to better understand the technical solution of the present invention, the technical solution of the present invention will be described in detail below with reference to specific embodiments.

[0029] Unless otherwise specified, all raw materials used in the following examples are commercially available products.

[0030] Example 1: The solvent (NMP, IPA) was dehydrated by molecular sieve, and the reaction vessel was baked at 120°C for 2 hours to remove moisture. The catalyst (CuI / L-proline) was premixed and ground. 175 g (0.86 mol) of 3-bromo-5-nitropyridine and 200.15 g (0.93 mol) of 4-hydroxy-4'-nitrobiphenyl were added sequentially to a solvent (1156.94 g NMP, 330.56 g IPA), heated and stirred until dissolved, and then added to a reaction vessel. 10.5 g of premixed catalyst (CuI / L-proline = 1:1.56) was added to the reaction vessel, and the temperature was raised to 85 °C. A slight positive pressure of 0.1 MPa nitrogen was maintained throughout the reaction. After 6 hours of reaction, 4.5 g of disodium EDTA was added and stirred for 10 minutes. Then, 2.1 g of Pd-Fe@C magnetic catalyst, 36.05 g of sodium dihydrogen phosphate buffer (21.63 g added in stage one, 14.42 g in stage two), and 5.20 g of EDTMPA chelating agent (3.0 g added in stage one, 0.0 g in stage two) were added. Add 2.2g of catalyst and react in stages. In stage one, the hydrogen pressure is 0.5MPa and the reaction temperature is 40℃ for 1h. In stage two, the hydrogen pressure is 1.2MPa and the reaction temperature is 60℃ for 3h. After reacting, the reaction solution is discharged, filtered, and the catalyst is washed multiple times with 5 times (catalyst dosage) of HCl / ethanol for easy reuse. The mother liquor is dissolved in 5 times (45℃) of ethanol and added dropwise to 18 times (3ml / min) of ice-cold n-hexane. After filtration, the crude product is dissolved in 8 times (65℃) of ethanol-water solution and the temperature is gradually decreased: from 60℃ to 25℃ at a rate of 1.5℃ / min, and from 20℃ to 0-4℃ at a rate of 0.3℃ / min. Finally, the product is washed twice with 3 times (0-4℃) of pre-cooled ethanol-water solution under vacuum. The product is then desorbed under low-temperature vacuum at 30℃ and dried under vacuum at 60℃ to obtain a final product of 225.51g. The NMR information is as follows: 1 ¹H NMR (DMSO): δ: 5.24 (s, 2H), 6.58 (d, 2H), 6.72 (s, 2H), 6.89 (s, H), 7.08 (d, 2H), 7.44 (d, 2H), 7.65 (d, 2H), 7.80 (s, H), 7.93 (s, H), yield 94.55%, purity 98.95%.

[0031] Example 2: The operation steps are the same as in Example 1, except that instead of adding 175g (0.86mol) of 3-bromo-5-nitropyridine and 200.15g (0.93mol) of 4-hydroxy-4'-nitrobiphenyl to the solvent (1156.94g NMP, 330.56g IPA) sequentially, 175g (0.86mol) of 3-bromo-5-nitropyridine and 200.15g (0.93mol) of 4-hydroxy-4'-nitrobiphenyl to the solvent (1487.5g NMP) were added, resulting in a final product of 225.08g. The NMR information is as follows: 1¹H NMR (DMSO): δ: 5.24 (s, 2H), 6.58 (d, 2H), 6.72 (s, 2H), 6.89 (s, H), 7.08 (d, 2H), 7.44 (d, 2H), 7.65 (d, 2H), 7.80 (s, H), 7.93 (s, H), yield 94.37%, purity 98.53%.

[0032] Example 3: The operation steps are the same as in Example 1, except that instead of adding 175g (0.86mol) of 3-bromo-5-nitropyridine and 200.15g (0.93mol) of 4-hydroxy-4'-nitrobiphenyl to the solvent (1156.94g NMP, 330.56g IPA) sequentially, 175g (0.86mol) of 3-bromo-5-nitropyridine and 200.15g (0.93mol) of 4-hydroxy-4'-nitrobiphenyl to the solvent (1487.5g IPA) were added to the solvent, resulting in a final product of 224.74g. The NMR information is as follows: 1 ¹H NMR (DMSO): δ: 5.24 (s, 2H), 6.58 (d, 2H), 6.72 (s, 2H), 6.89 (s, H), 7.08 (d, 2H), 7.44 (d, 2H), 7.65 (d, 2H), 7.80 (s, H), 7.93 (s, H), yield 94.23%, purity 98.45%.

[0033] Example 4: The operation steps are the same as in Example 1, except that instead of adding 175g (0.86mol) of 3-bromo-5-nitropyridine and 200.15g (0.93mol) of 4-hydroxy-4'-nitrobiphenyl to the solvent (1156.94g NMP, 330.56g IPA) sequentially, 175g (0.86mol) of 3-bromo-5-nitropyridine and 200.15g (0.93mol) of 4-hydroxy-4'-nitrobiphenyl to the solvent (330.56g NMP, 1156.94g IPA) sequentially, 225.20g of the final product is obtained. The NMR information is as follows: 1 ¹H NMR (DMSO): δ: 5.24 (s, 2H), 6.58 (d, 2H), 6.72 (s, 2H), 6.89 (s, H), 7.08 (d, 2H), 7.44 (d, 2H), 7.65 (d, 2H), 7.80 (s, H), 7.93 (s, H), yield 94.42%, purity 98.60%.

[0034] Example 5: The operation steps are the same as in Example 1, except that 36.05g of sodium dihydrogen phosphate buffer (21.63g added in stage 1 and 14.42g added in stage 2) was replaced with 36.05g of sodium dihydrogen phosphate buffer (18.03g added in both stages 1 and 2), resulting in a final product of 225.27g. The NMR information is as follows: 1 ¹H NMR (DMSO): δ: 5.24 (s, 2H), 6.58 (d, 2H), 6.72 (s, 2H), 6.89 (s, H), 7.08 (d, 2H), 7.44 (d, 2H), 7.65 (d, 2H), 7.80 (s, H), 7.93 (s, H), yield 94.45%, purity 98.67%.

[0035] Example 6: The operation steps are the same as in Example 1, except that 5.20g of EDTMPA chelating agent (3.0g added in stage 1 and 2.2g added in stage 2) is replaced with 5.20g of EDTMPA chelating agent (2.6g added in stage 1 and 2.6g added in stage 2), resulting in a final product of 225.39g. The NMR information is as follows: 1 ¹H NMR (DMSO): δ: 5.24 (s, 2H), 6.58 (d, 2H), 6.72 (s, 2H), 6.89 (s, H), 7.08 (d, 2H), 7.44 (d, 2H), 7.65 (d, 2H), 7.80 (s, H), 7.93 (s, H), yield 94.50%, purity 98.71%.

[0036] Comparative Example 1: The operation steps were the same as in Example 1, except that 10.5g of premixed catalyst (CuI / L-proline = 1:1.56) was added to the reactor, the temperature was raised to 85°C, and a slight positive pressure of 0.1MPa nitrogen was maintained throughout the reaction. After 6 hours of reaction, 4.5g of disodium EDTA was added and stirred for 10 minutes, followed by the addition of 2.1g of Pd-Fe@C magnetic catalyst. Alternatively, 12.6g of premixed catalyst (CuI / L-proline = 1:1.56) was added to the reactor, the temperature was raised to 85°C, and a slight positive pressure of 0.1MPa nitrogen was maintained throughout the reaction. After 6 hours of reaction, 4.5g of disodium EDTA was added and stirred for 10 minutes. No Pd-Fe@C magnetic catalyst was added. The final product was 208.36g, with a yield of 87.36% and a purity of 85.62%.

[0037] Comparative Example 2: The operation steps were the same as in Example 1, except that 10.5g of premixed catalyst (CuI / L-proline = 1:1.56) was added to the reactor, the temperature was raised to 85°C, and a slight positive pressure of 0.1MPa nitrogen was maintained throughout the reaction. After 6 hours of reaction, 4.5g of disodium EDTA was added and stirred for 10 minutes, followed by the addition of 2.1g of Pd-Fe@C magnetic catalyst. Alternatively, 12.6g of Pd-Fe@C magnetic catalyst was added to the reactor, the temperature was raised to 85°C, and a slight positive pressure of 0.1MPa nitrogen was maintained throughout the reaction. After 6 hours of reaction, 4.5g of disodium EDTA was added and stirred for 10 minutes. No more premixed catalyst was added. The final product was 217.63g, with a yield of 91.25% and a purity of 89.12%.

[0038] Comparative Example 3: The procedure is the same as in Example 1, except that instead of adding 4.5g of disodium EDTA and stirring for 10 min followed by adding 2.1g of Pd-Fe@C magnetic catalyst and 36.05g of sodium dihydrogen phosphate buffer (21.63g added in stage 1 and 14.42g added in stage 2), 1.2g of disodium EDTA and stirring for 10 min followed by adding 2.1g of Pd-Fe@C magnetic catalyst are added, and the sodium dihydrogen phosphate buffer is no longer added. The final product is 215.13g, with a yield of 90.20% and a purity of 88.75%.

[0039] Application example: Product preparation: The compound synthesized in Example 1 was dissolved in DMSO and stirred until homogeneous. The additive system was then atomized using a high-pressure nozzle and injected through a metering vessel into a mixer containing a semi-finished insoluble sulfur product. The mass ratio of the semi-finished insoluble sulfur, naphthenic oil, and pyridine biphenyl derivative was 80:20:0.4. Stirring was performed at 90°C for 30 minutes at a stirring speed of 90 rpm and a blade speed of 1400 rpm. After 30 minutes, the naphthenic oil was atomized using a high-pressure nozzle and injected through a metering vessel into the mixer. Stirring was performed at 85°C for 20 minutes at a stirring speed of 80 rpm and a blade speed of 1200 rpm. After 20 minutes, the remaining naphthenic oil was added, and the mixture was stirred at 75°C for 10 minutes at a stirring speed of 60 rpm and a blade speed of 900 rpm. After vacuum devolatilization, the mixture was cooled to 60°C and placed in a silo. The product was then sieved and packaged to obtain the insoluble sulfur product.

[0040] Application Experiment:

[0041] First stage of intensive mixing: initial temperature 80℃, rotation speed 50rpm, add glue in 20s, mix with a grinding wheel for 60s, lift the grinding wheel for 10s, add small ingredients and carbon black, mix with a grinding wheel for 80-100s, clean in the middle position for 10s, mix with a grinding wheel for 40-60s, repeat 3 times, and discharge glue (total 390s).

[0042] Two-stage open mill: Adjust the roller gap of the open mill so that there is an appropriate amount of accumulated rubber above the open mill, then roll and mix for about 1 minute. Add HMMM-55, DZ, and insoluble sulfur (after adding additives). After the material is fully absorbed, cut the blades three times on each side and then extrude the sheet. Adjust the roller gap of the open mill to the appropriate level, make 3 triangular wraps and 5 rolls, then adjust the roller gap and extrude the sheet for testing.

[0043] The application performance test results are as follows: 1. Sulfur rheometer test

[0044] The table shows that the addition of additives resulted in better vulcanization than the blank, with faster vulcanization efficiency and higher crosslinking density. The compound contains amino and pyridine groups, which can accelerate the vulcanization reaction, improve vulcanization efficiency, and thus achieve a higher degree of vulcanization. These active groups play a catalytic role in the vulcanization process, promoting the crosslinking of sulfur with rubber molecular chains.

[0045] 2. Physical and mechanical properties

[0046] The table shows that the added additives result in higher tensile strength, better aging performance, better mechanical properties, and higher retention rate compared to the blank. These active groups play a catalytic role in the vulcanization process, promoting the cross-linking of sulfur and rubber molecular chains, thereby improving the physical properties of the rubber.

[0047] The above embodiments are preferred embodiments of the present invention, but the embodiments of the present invention are not limited to the above embodiments. Any changes, modifications, substitutions, combinations, or simplifications made without departing from the spirit and principle of the present invention shall be considered equivalent substitutions and shall be included within the protection scope of the present invention.

Claims

1. A method for synthesizing a pyridine biphenyl derivative, characterized in that, The method includes the following steps: 3-Bromo-5-nitropyridine and 4-hydroxy-4'-nitrobiphenyl were added sequentially to a solvent, heated and stirred until dissolved, and then added to a reaction vessel. A premixed catalyst was added to the reaction vessel, and the temperature was raised to 80-90℃. A slight positive pressure nitrogen atmosphere was maintained throughout the reaction. After 5-7 hours of reaction, a multifunctional metal chelating agent was added and stirred for 5-15 minutes, followed by the addition of a hydrogenation catalyst. Hydrogen gas was introduced in two stages for the reaction, with buffers and organophosphonic acid chelating agents added in both stages. After the staged reactions were completed, the reaction solution was discharged, filtered, and the catalyst was washed multiple times with HCl / ethanol solution for reuse. The mother liquor was dissolved in ethanol at 40-50℃ and added dropwise to ice-cold n-hexane. The mixture was filtered, and the crude product was dissolved in an ethanol-water solution at 60-70℃. The temperature was gradually decreased, and the product was finally washed with pre-cooled ethanol-water solution under vacuum. Low-temperature vacuum desorption and vacuum drying were performed to obtain the final product.

2. The method for synthesizing the pyridine biphenyl derivative as described in claim 1, characterized in that, The solvent is a product that has been dehydrated by molecular sieve and baked in a reaction vessel to remove moisture; the solvent is one or more of methanol, IPA, DMF, NMP, DMSO, and 1,3-dimethyl-2-imidazolinone; preferably, the solvent is a mixed solvent composed of NMP and IPA.

3. The method for synthesizing the pyridine biphenyl derivative as described in claim 1, characterized in that, The mass ratio of 3-bromo-5-nitropyridine to solvent is 1:6.5-11.5; preferably, the mass ratio of 3-bromo-5-nitropyridine to solvent is 1:8.0-10.

0.

4. The method for synthesizing the pyridine biphenyl derivative as described in claim 1, characterized in that, The catalyst is a composite catalytic system, which uses CuI as a copper source and L-proline as a co-catalyst; the amount of CuI is 5-7% of the mass of 3-bromo-5-nitropyridine, and the mass ratio of CuI to L-proline is 1:1.21-1.82; preferably, the mass ratio of CuI to L-proline is 1:1.45-1.

70.

5. The method for synthesizing the pyridine biphenyl derivative as described in claim 1, characterized in that, The multifunctional metal chelating agent is one of disodium EDTA, DTPA, EDDS, and CDTA; The dosage is 1.0-3.0% of the mass of 3-bromo-5-nitropyridine; preferably, the dosage is 2.0-2.9% of the mass of 3-bromo-5-nitropyridine.

6. The method for synthesizing the pyridine biphenyl derivative as described in claim 1, characterized in that, The organophosphonic acid chelating agent is one of HEDP, ATMP, DTPMPA, and EDTMPA, and its dosage is 1.5-3.5% of the mass of 3-bromo-5-nitropyridine. It is added in stages: in stage one, 30-70% of the total amount is added, and in stage two, the remaining organophosphonic acid chelating agent is added. The buffer is sodium dihydrogen phosphate buffer, which is used to adjust the pH to 6.5-7.

0. Its dosage is 15-35% of the mass of 3-bromo-5-nitropyridine, and it is added in stages: in stage one, 30-80% of the total amount is added, and in stage two, the remaining buffer is added.

7. The method for synthesizing the pyridine biphenyl derivative as described in claim 1, characterized in that, The molar ratio of 3-bromo-5-nitropyridine to 4-hydroxy-4'-nitrobiphenyl is 1:1.02-1.15; preferably, the molar ratio of 3-bromo-5-nitropyridine to 4-hydroxy-4'-nitrobiphenyl is 1:1.05-1.

10. The hydrogenation catalyst is a supported bimetallic core-shell structure catalyst, which is a Pd-Fe@C magnetic catalyst, and its amount accounts for 0.8-1.7% of the mass of 3-bromo-5-nitropyridine; preferably, the amount accounts for 1.0-1.5% of the mass of 3-bromo-5-nitropyridine.

8. The method for synthesizing the pyridine biphenyl derivative as described in claim 1, characterized in that, The HCl / ethanol solution is 2-10 times the mass of the hydrogenation catalyst; the volume ratio of ethanol to mother liquor at 40-50℃ is 2.1-7.7:1; the volume ratio of glacial hexane to mother liquor is 13.4-32.2:1, and the dropping rate is 1-10 ml / min; the mass ratio of ethanol-water solution to product at 60-70℃ is 5.7-10.1:1; pre-cooled ethanol-water washing is performed, with the amount being 1-9 times the product volume.

9. The method for synthesizing the pyridine biphenyl derivative as described in claim 1, characterized in that, The phased reaction is as follows: Phase 1 hydrogen pressure 0.3-1.1 MPa, 35-45℃, 0.5-1.5 h; Phase 2 hydrogen pressure 1.2-1.9 MPa, 55-65℃, 2.5-3.5 h. The gradient cooling process involves first cooling to 25°C at a rate of 1.0-6.0°C / min, and then cooling to 0-4°C at a rate of 0.1-1.0°C / min.

10. The application of the method according to any one of claims 1 to 9 in the preparation of rubber vulcanization accelerators.

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