Method for synthesizing 3, 3 ', 5, 5'-tetramethyl-4, 4 '-dihydroxybiphenyl and derivatives thereof

Abstract

The invention discloses a method for synthesizing 3, 3 '-difluorobenzene. The invention discloses a method for preparing 3, 3 ', 5, 5'-tetramethyl-4, 4 '-dihydroxybiphenyl and derivatives thereof, which comprises the following steps of: adding 1.0 mmol of 4-halogenated aryl phenol compound, 0.05 mmol of photocatalyst and a solvent into a reaction container in a nitrogen atmosphere, stirring until the materials are dissolved, adding 0.05 mmol of metal catalyst and 0.06 mmol of ligand which are prepared in advance, turning on a light source, stirring for 24 hours at room temperature, performing thin layer chromatography detection reaction, filtering, washing and drying to obtain the 3, 3', 5, 5 '-tetramethyl-4, 4'-dihydroxybiphenyl and derivatives thereof. And after the reaction is finished, filtering the reaction liquid, removing the solvent through rotary evaporation, and carrying out recrystallization or column chromatography by using a mixed solvent to obtain the target product 3, 3 ', 5, 5'-tetramethyl-4, 4 '-dihydroxybiphenyl and the derivative thereof. According to the method, the 4-halogenated aryl phenol compound is used as a raw material, the required compound is obtained in one step through'nickel + light 'catalysis, and waste and related pollution caused by the use of high-explosive gas or a reducing agent are not needed; and a recyclable photocatalyst is used, so that the method is more environment-friendly and has a good industrial application prospect.

Description

Technical Field

[0001] The present invention belongs to the field of organic synthesis, and particularly relates to a method for synthesizing 3,3',5,5'-tetramethyl-4,4'-dihydroxybiphenyl and its derivatives. Background Art

[0002] 3,3',5,5'-Tetramethyl-4,4'-dihydroxybiphenyl is a very important organic synthesis intermediate. Its CAS number is 2417-04-1, and its melting point is 222-225 °C. It is often a grayish-white or slightly yellow solid, and the reason for the yellow color is often the presence of a certain content of p-benzoquinone. With the development of China's chemical industry and electronics industry, researchers have found that 3,3',5,5'-tetramethyl-4,4'-dihydroxybiphenyl has good applications in liquid crystal polymers, electron transport materials, organic material stabilizers, metal catalytic ligands, organic solar cells, flame retardants, etc. In the case of epoxy resins used in the electronics industry, the resins synthesized from 3,3',5,5'-tetramethyl-4,4'-dihydroxybiphenyl have good physical and chemical properties, such as high toughness, good heat resistance, insulation, etc. Currently, the market share of epoxy resin-based plastic encapsulants is about 80% of the entire electronic packaging materials. Therefore, studying the method for synthesizing 3,3',5,5'-tetramethyl-4,4'-dihydroxybiphenyl is of great significance to the electronics industry.

[0003] Currently, the mainstream method for synthesizing 3,3',5,5'-tetramethyl-4,4'-dihydroxybiphenyl is the oxidative coupling method, that is, 2,6-dimethylphenol is carried out under the catalysis of transition metals (usually catalysts such as copper, rhodium, ruthenium, etc.) with oxygen as the oxidation source. Such reactions often produce a large amount of 3,3',5,5'-tetramethyl-4,4'-biphenyldione by-products. In order to reduce the quinone compounds, a reducing agent needs to be added. This is the currently common "two-step method" for preparing 3,3',5,5'-tetramethyl-4,4'-dihydroxybiphenyl. Related literatures using this method include CN 106831350 A, CN 110105176 A, CN 106928031 A, CN 115677455 A, etc.

[0004] In 2020, Professor D.C. MacMillan, the Nobel laureate, found that under the catalysis of nickel, relevant photocatalysts can enable coupling reactions between reagents such as haloalkanes. Inspired by this, the present invention explored the possibility of photocatalysis in the synthesis of 3,3',5,5'-tetramethyl-4,4'-dihydroxybiphenyl and achieved corresponding research results. This method has the characteristics of recyclable reagents, recyclable catalysts, and high yield. Importantly, this method can synthesize 3,3',5,5'-tetramethyl-4,4'-dihydroxybiphenyl in one step without using reducing agents such as sodium dithionite or hydrogen. Summary of the Invention

[0005] The object of the present invention is to provide a method for synthesizing 3,3',5,5'-tetramethyl-4,4'-dihydroxybiphenyl and its derivatives. This method can give a new solution to the problems existing in the synthesis of such compounds at present; to achieve the above object of the invention, the present invention proposes the following technical solutions: A method for synthesizing 3,3',5,5'-tetramethyl-4,4'-dihydroxybiphenyl and its derivatives, comprising the following steps: under a nitrogen atmosphere, add 1.0 mmol of 4-haloaryl phenol compounds to a reaction vessel, add 0.05 mmol of a photocatalyst, add a solvent, stir until the materials are dissolved, then add 0.05 mmol of a pre-prepared metal catalyst and 0.06 mmol of a ligand and turn on the light source, stir at room temperature for 24 h, detect the reaction by thin layer chromatography, after the reaction is completed, filter the reaction solution, remove the solvent by rotary evaporation, and perform recrystallization or column chromatography on it with a mixed solvent to obtain the target product 3,3',5,5'-tetramethyl-4,4'-dihydroxybiphenyl and its derivatives; The 4-haloaryl phenol compounds are one or more of 4-chlorophenol, 4-bromophenol, 4-iodophenol, 4-chloro-2-methylphenol, 4-bromo-2-methylphenol, 4-iodo-2-methylphenol, 4-chloro-2,6-dimethylphenol, 4-bromo-2,6-dimethylphenol, 4-iodo-2,6-dimethylphenol, 4-trifluoromethanesulfonyl-2,6-dimethylphenol, 4-p-toluenesulfonyl-2,6-dimethylphenol, 4-chloro-2,3,6-trimethylphenol, 4-bromo-2,3,6-trimethylphenol, 4-iodo-2,3,6-trimethylphenol, 4-trifluoromethanesulfonyl-2,3,6-trimethylphenol, 4-p-toluenesulfonyl-2,3,6-trimethylphenol, 4-chloro-2,3,5,6-tetramethylphenol, 4-bromo-2,3,5,6-tetramethylphenol, 4-trifluoromethanesulfonyl-2,3,5,6-tetramethylphenol, 4-chloro-2-methoxyphenol, 4-bromo-2-methoxyphenol, 4-iodo-2-methoxyphenol, 4-chloro-2,6-dimethoxyphenol, 4-bromo-2,6-dimethoxyphenol, 4-iodo-2,6-dimethoxyphenol, 4-chloro-2,3,6-trimethoxyphenol, 4-bromo-2,3,6-trimethoxyphenol, 4-iodo-2,3,6-trimethoxyphenol, 4-chloro-2,3,5,6-tetramethoxyphenol, 4-bromo-2,3,5,6-tetramethoxyphenol; The metal catalyst is one or more of nickel chloride, nickel bromide, nickel iodide, nickel sulfate, palladium acetate; The ligand is one or more of pyridine, imidazole, 4-dimethylaminopyridine, bipyridine, 2,9-dimethyl-1,10-phenanthroline (CAS: 484-11-7), 3,4,7,8-tetramethyl-1,10-phenanthroline (CAS: 1660-93-1), 4,7-diphenyl-1,10-phenanthroline (CAS: 1662-01-7), 5,6-dimethyl-1,10-phenanthroline (CAS: 3002-81-1), 4,7-dimethyl-1,10-phenanthroline (CAS: 3248-05-3), 4,4'-dimethyl-2,2'-bipyridine, 4,4'-dimethoxy-2,2'-bipyridine, 4,4'-di-tert-butyl-2,2'-bipyridine, 5,5'-dimethyl-2,2'-bipyridine, 6,6'-dimethyl-2,2'-bipyridine; The photocatalyst is one or more of 9-thioxanthone, 10-phenylphenothiazine, iridium(III) tris(2-(4-fluorophenyl)pyridine), fac-tris(2-phenylpyridine)iridium (CAS: 94928-86-6), 5,10-bis(2-naphthyl)-5,10-dihydrophenazine, 5,10-dimethyl-5,10-dihydrophenazine; The solvent is one or more of acetonitrile, 1,4-dioxane, dimethyl sulfoxide, N,N-dimethylformamide, N,N-dimethylacetamide, N-methylpyrrolidone, n-pentane, n-hexane, cyclohexane; The mixed solvent is one or more of n-pentane, n-hexane, cyclohexane, petroleum ether, methanol, ethanol, n-propanol, isopropanol, n-butanol, isobutanol, tert-butanol, chloroform, toluene, ethyl acetate, acetonitrile, tetrahydrofuran, 1,4-dioxane.

[0006] 1. Its beneficial effects are as follows: Considering from the perspective of economic cost, 9-xanthone has significant economic applicability advantages compared with various photosensitive reducing agents. It is stable at room temperature and is convenient for long-term storage, thus further reducing the cost input in the actual application process.

[0007] 2. This method uses 4-haloaryl phenolic compounds as raw materials and obtains the required compounds in one step through the "nickel + light" catalysis scheme. The photocatalysis scheme avoids the problems of insufficient atom economy and the use of explosive products in the existing preparation processes. This method has mild conditions, simple operation, stable yield and high purity of the target product. There is no need to use high-explosive gases or reducing agents commonly used in the preparation of this compound during the reaction process, thus avoiding waste and related pollution; The entire reaction process does not involve oxidation reactions, thus effectively inhibiting the generation of quinones. In addition, a recyclable photocatalyst is used during the reaction process, which is more environmentally friendly and has good industrial application prospects. Description of the Drawings

[0008] Figure 1 1H NMR spectrum of the product of Preparation Example 2 1 1H NMR Detailed implementation mode

[0009] The following examples are intended to further illustrate the content of the present invention, rather than limiting the protection scope of the present invention.

[0010] In order to ensure the accuracy of the condition optimization experiment, the product separation method in the condition optimization experiment adopts the silica gel chromatography column method.

[0011] 1H nuclear magnetic resonance 1 1H NMR (400 MHz), 13C nuclear magnetic resonance 13 13C NMR (101 MHz) detection is carried out using a Bruker spectrometer.

[0012] Condition optimization experiment Using 4-chloro-2,6-dimethylphenol as the reaction raw material, the target 3,3',5,5'-tetramethyl-4,4'-dihydroxybiphenyl is synthesized, and various aspects of the reaction ligand, solvent, and reducing agent are investigated to obtain the best reaction conditions.

[0013]

[0014] Ligand screening scheme 1: Add 0.110 g (0.6 mmol) of 4,4'-dimethyl-2,2'-bipyridine, 0.119 g (0.5 mmol) of nickel chloride hexahydrate, and 0.106 g (0.5 mmol) of 9-thioxanthone to a 50 mL round-bottom flask. The flask is evacuated and filled with nitrogen three times, and then 1.56 g (10 mmol) of 2,3-dimethyl-4-chlorophenol and 10 mL of the solvent N,N-dimethylformamide are added to the flask. The reaction solution is irradiated with a CFL (integrated fluorescent lamp) and stirred for 24 h. The progress of the reaction is detected by thin-layer chromatography. When the reaction is completed, it is extracted with 50 mL of ethyl acetate and separated. After drying the organic phase, the organic phase is rotary evaporated to obtain a crude product. The crude product is subjected to column chromatography with a mixed solvent of petroleum ether:ethyl acetate = 5:1 to obtain the product in a yield of 32%.

[0015] Ligand screening scheme 2: Add 0.129 g (0.6 mmol) of 4,4'-dimethoxy-2,2'-bipyridine, 0.119 g (0.5 mmol) of nickel(II) chloride hexahydrate, and 0.106 g (0.5 mmol) of 9-thioxanthone to a 50 mL round-bottom flask. Evacuate and refill the flask with nitrogen three times. Then add 1.56 g (10 mmol) of 2,3-dimethyl-4-chlorophenol and 10 mL of the solvent N,N-dimethylformamide to the flask. Irradiate the reaction solution with a CFL (compact fluorescent lamp) and stir it for 24 h. Monitor the progress of the reaction by thin-layer chromatography. It is found that there is only a small amount of product. After the reaction is completed, extract with 50 mL of ethyl acetate and separate the layers. Dry the organic phase and then evaporate the solvent to obtain the crude product. Column chromatograph the crude product using a mixed solvent of petroleum ether:ethyl acetate = 5:1 to obtain the product in a yield of 2%.

[0016] Ligand screening protocol three: Add 0.160 g (0.6 mmol) of 4,4'-di-tert-butyl-2,2'-bipyridine, 0.119 g (0.5 mmol) of nickel(II) chloride hexahydrate, and 0.106 g (0.5 mmol) of 9-thioxanthone to a 50 mL round-bottom flask. Evacuate and refill the flask with nitrogen three times. Then add 1.56 g (10 mmol) of 2,3-dimethyl-4-chlorophenol and 10 mL of the solvent N,N-dimethylformamide to the flask. Irradiate the reaction solution with a CFL (compact fluorescent lamp) and stir it for 24 h. Monitor the progress of the reaction by thin-layer chromatography. After the reaction is completed, extract with 50 mL of ethyl acetate and separate the layers. Dry the organic phase and then evaporate the solvent to obtain the crude product. Column chromatograph the crude product using a mixed solvent of petroleum ether:ethyl acetate = 5:1 to obtain the product in a yield of 89%.

[0017] Ligand screening protocol four: Add 0.110 g (0.6 mmol) of 5,5'-dimethyl-2,2'-bipyridine, 0.119 g (0.5 mmol) of nickel(II) chloride hexahydrate, and 0.106 g (0.5 mmol) of 9-thioxanthone to a 50 mL round-bottom flask. Evacuate and refill the flask with nitrogen three times. Then add 1.56 g (10 mmol) of 2,3-dimethyl-4-chlorophenol and 10 mL of the solvent N,N-dimethylformamide. Irradiate the reaction solution with a CFL (integrated fluorescent lamp) and stir for 24 h. Monitor the progress of the reaction by thin-layer chromatography. Only a small amount of product is found. After the reaction is complete, extract with 50 mL of ethyl acetate and separate the layers. Dry the organic phase and then evaporate the solvent to obtain the crude product. Purify the crude product by column chromatography using a mixed solvent of petroleum ether:ethyl acetate = 5:1 to obtain the product in a yield of 11%.

[0018] Ligand screening protocol five: Add 0.110 g (0.6 mmol) of 6,6'-dimethyl-2,2'-bipyridine, 0.119 g (0.5 mmol) of nickel(II) chloride hexahydrate, and 0.106 g (0.5 mmol) of 9-thioxanthone to a 50 mL round-bottom flask. Evacuate and refill the flask with nitrogen three times. Then add 1.56 g (10 mmol) of 2,3-dimethyl-4-chlorophenol and 10 mL of the solvent N,N-dimethylformamide. Irradiate the reaction solution with a CFL (integrated fluorescent lamp) and stir for 24 h. Monitor the progress of the reaction by thin-layer chromatography. Only a small amount of product is found. After the reaction is complete, extract with 50 mL of ethyl acetate and separate the layers. Dry the organic phase and then evaporate the solvent to obtain the crude product. Purify the crude product by column chromatography using a mixed solvent of petroleum ether:ethyl acetate = 5:1 to obtain the product in a yield of 7%.

[0019] Ligand screening protocol six: Add 0.108 g (0.6 mmol) of 1,10-phenanthroline, 0.119 g (0.5 mmol) of nickel(II) chloride hexahydrate, and 0.106 g (0.5 mmol) of 9-thioxanthone to a 50 mL round-bottom flask. Evacuate and refill the flask with nitrogen three times. Then add 1.56 g (10 mmol) of 2,3-dimethyl-4-chlorophenol and 10 mL of the solvent N,N-dimethylformamide. Irradiate the reaction solution with a CFL (integrated fluorescent lamp) and stir for 24 h. Monitor the progress of the reaction by thin-layer chromatography. No product is found.

[0020]

[0021] Solvent screening protocol one: Add 0.160 g (0.6 mmol) of 4,4'-di-tert-butyl-2,2'-bipyridine, 0.119 g (0.5 mmol) of nickel(II) chloride hexahydrate, and 0.106 g (0.5 mmol) of 9-thioxanthone to a 50 mL round-bottom flask. Evacuate and refill the flask with nitrogen three times. Then add 1.56 g (10 mmol) of 2,3-dimethyl-4-chlorophenol and 10 mL of the solvent N,N-dimethylformamide to the flask. Irradiate the reaction solution with a CFL (integrated fluorescent lamp) and stir it for 24 h. Monitor the progress of the reaction by thin-layer chromatography. After the reaction is complete, extract with 50 mL of ethyl acetate and separate the layers. Dry the organic phase and then evaporate the solvent to obtain the crude product. Column chromatograph the crude product using a mixed solvent of petroleum ether:ethyl acetate = 5:1 to obtain the product in a yield of 89%.

[0022] Solvent screening protocol two: Add 0.160 g (0.6 mmol) of 4,4'-di-tert-butyl-2,2'-bipyridine, 0.119 g (0.5 mmol) of nickel(II) chloride hexahydrate, and 0.106 g (0.5 mmol) of 9-thioxanthone to a 50 mL round-bottom flask. Evacuate and refill the flask with nitrogen three times. Then add 1.56 g (10 mmol) of 2,3-dimethyl-4-chlorophenol and 10 mL of the solvent N,N-dimethylacetamide to the flask. Irradiate the reaction solution with a CFL (integrated fluorescent lamp) and stir it for 24 h. Monitor the progress of the reaction by thin-layer chromatography. After the reaction is complete, extract with 50 mL of ethyl acetate and separate the layers. Dry the organic phase and then evaporate the solvent to obtain the crude product. Column chromatograph the crude product using a mixed solvent of petroleum ether:ethyl acetate = 5:1 to obtain the product in a yield of 93%.

[0023] Solvent screening protocol three: Add 0.160 g (0.6 mmol) of 4,4'-di-tert-butyl-2,2'-bipyridine, 0.119 g (0.5 mmol) of nickel(II) chloride hexahydrate, and 0.106 g (0.5 mmol) of 9-thioxanthone to a 50 mL round-bottom flask. Evacuate and refill the flask with nitrogen three times. Then add 1.56 g (10 mmol) of 2,3-dimethyl-4-chlorophenol and 10 mL of the solvent dimethyl sulfoxide to the flask. React for 24 h. Monitor the progress of the reaction by thin-layer chromatography. After the reaction is complete, extract with 50 mL of ethyl acetate and separate the layers. Dry the organic phase and then evaporate the solvent to obtain the crude product. Column chromatograph the crude product using a mixed solvent of petroleum ether:ethyl acetate = 5:1 to obtain the product in a yield of 72%.

[0024] Solvent Screening Scheme Four: Add 0.160 g (0.6 mmol) of 4,4'-di-tert-butyl-2,2'-bipyridine, 0.119 g (0.5 mmol) of nickel(II) chloride hexahydrate, and 0.106 g (0.5 mmol) of 9-thioxanthone into a 50 mL round-bottom flask. Evacuate and refill the flask with nitrogen three times. Then add 1.56 g (10 mmol) of 2,3-dimethyl-4-chlorophenol and 10 mL of dichloromethane as the solvent. Irradiate the reaction solution with a CFL (integrated fluorescent lamp) and stir for 24 h. Monitor the reaction progress by thin-layer chromatography. It is found that no product can be obtained with this scheme.

[0025] Solvent Screening Scheme Five: Add 0.160 g (0.6 mmol) of 4,4'-di-tert-butyl-2,2'-bipyridine, 0.119 g (0.5 mmol) of nickel(II) chloride hexahydrate, and 0.106 g (0.5 mmol) of 9-thioxanthone into a 50 mL round-bottom flask. Evacuate and refill the flask with nitrogen three times. Then add 1.56 g (10 mmol) of 2,3-dimethyl-4-chlorophenol and 10 mL of tetrahydrofuran as the solvent. Irradiate the reaction solution with a CFL (integrated fluorescent lamp) and stir for 24 h. Monitor the reaction progress by thin-layer chromatography. It is found that no product can be obtained with this scheme.

[0026]

[0027] Reducing Agent Screening Scheme One: Add 0.160 g (0.6 mmol) of 4,4'-di-tert-butyl-2,2'-bipyridine, 0.119 g (0.5 mmol) of nickel(II) chloride hexahydrate, and 0.56 g (10 mmol) of manganese powder into a 50 mL round-bottom flask. Evacuate and refill the flask with nitrogen three times. Then add 1.56 g (10 mmol) of 2,3-dimethyl-4-chlorophenol and 10 mL of N,N-dimethylformamide as the solvent. Stir for 24 h. Monitor the reaction progress by thin-layer chromatography. After the reaction is completed, extract with 50 mL of ethyl acetate and separate the layers. Dry the organic phase and then rotary evaporate the organic phase to obtain the crude product. The crude product is subjected to column chromatography using a mixed solvent of petroleum ether:ethyl acetate = 5:1, and the product is obtained in a yield of 21%.

[0028] Reducing Agent Screening Scheme Two: Add 0.160 g (0.6 mmol) of 4,4'-di-tert-butyl-2,2'-bipyridine, 0.119 g (0.5 mmol) of nickel(II) chloride hexahydrate, and 0.65 g (10 mmol) of zinc powder to a 50 mL round-bottom flask. Evacuate and refill the flask with nitrogen three times. Then add 1.56 g (10 mmol) of 2,3-dimethyl-4-chlorophenol and 10 mL of the solvent N,N-dimethylformamide to the flask. Stir for 24 h and monitor the reaction progress by thin-layer chromatography. It was found that the product could not be obtained by this method.

[0029] Reductant screening protocol three: The test method of reductant screening protocol three is the same as that of solvent screening protocol one.

[0030] The present invention will be further described below in conjunction with specific preparation examples: Preparation example 1:

[0031] Wherein R1 is one kind of alkyl group.

[0032] Under a nitrogen atmosphere, add 1 mmol of 4-haloaryl phenolic compound and 1.0 mmol to the reaction vessel. After adding 0.05 mmol of photocatalyst and 0.05 mmol, add the solvent. After stirring until the materials are dissolved, add 0.05 mmol of the pre-prepared metal catalyst and 0.05 mmol, and 0.06 mmol of ligand and 0.06 mmol, and then turn on the light source. Stir at room temperature for 24 h and monitor the reaction by thin-layer chromatography. After the reaction is completed, filter the reaction solution, remove the solvent by rotary evaporation, and recrystallize it with a mixed solvent to obtain the target product 3,3',5,5'-tetramethyl-4,4'-dihydroxybiphenyl and its derivatives.

[0033] Preparation example 2:

[0034] Add 1.87 g (12 mmol) of 4,4'-di-tert-butyl-2,2'-bipyridine, 1.10 g (10 mmol) of nickel chloride, and 2.12 g (10 mmol) of 9-xanthone to a 500 mL round-bottom flask. Evacuate and refill the flask with nitrogen three times, and then add 350 mL of the solvent N,N-dimethylformamide to the flask. Add 31.32 g (200 mmol) of 2,3-dimethyl-4-chlorophenol to the above mixed solution. Irradiate the reaction solution with a CFL (integrated fluorescent lamp) and stir it for 24 h. Monitor the progress of the reaction by thin layer chromatography. After the reaction is completed, filter the reaction solution through a sintered funnel filled with silica gel (100 mesh) as a packing material and wash it with ethyl acetate. Rotate the organic phase of the obtained filtrate to dryness using a rotary evaporator to obtain a crude product. Recrystallize the crude product with 50 mL of a mixed solvent of n-hexane:ethyl acetate = 2:1 to obtain the product in a yield of 83%.

[0035] Nuclear magnetic resonance data: 1 H NMR (400 MHz, Chloroform- d ) δ 7.15 (s, 4H), 4.62 (s, 2H), 2.32 (s,12H) ppm.; 13 C NMR (101 MHz, Chloroform- d ) δ 151.3, 133.3, 127.0, 123.1, 16.1ppm..

[0036] 1H NMR spectrum of the product of Preparation Example 2 1 1HNMR is as Figure 1 shown.

[0037] From the perspective of economic cost, 9-xanthone has significant economic applicability advantages compared with a variety of photosensitive reducing agents. It has stable properties at room temperature and is convenient for long-term storage, thus further reducing the cost input in the actual application process.

[0038] This method uses 4-haloaryl phenol compounds as raw materials and obtains the required compounds in one step through a "nickel + light" catalyzed scheme. The photocatalytic scheme is adopted to avoid the problems of insufficient atom economy and the use of explosive products in the existing preparation processes. This method has mild conditions, simple operation, stable yield and high purity of the target product. There is no need to use high-explosive gases or reducing agents commonly used in the preparation of this compound during the reaction process, thus avoiding waste and related pollution. The entire reaction process does not involve oxidation reactions, thus effectively inhibiting the generation of quinones. In addition, a recyclable photocatalyst is used during the reaction process, which is more environmentally friendly and has good industrial application prospects.

[0039] The above are only some embodiments of the present invention. For those of ordinary skill in the art, without departing from the creative concept of the present invention, several modifications and improvements can still be made, and these all belong to the protection scope of the present invention.

Claims

1. A method for synthesizing 3,3',5,5'-tetramethyl-4,4'-dihydroxybiphenyl and its derivatives, characterized in that: Under a nitrogen atmosphere, 1.0 mmol of a 4-halogenated aromatic phenol compound, 0.05 mmol of a photocatalyst, and a solvent are added to a reaction container. After stirring until the material is dissolved, 0.05 mmol of a pre-prepared metal catalyst and 0.06 mmol of a ligand are added, and the light source is turned on. The mixture is stirred at room temperature for 24 h, and the reaction is detected by thin layer chromatography. After the reaction is completed, the reaction solution is filtered, the solvent is removed by rotary evaporation, and a mixed solvent is used for recrystallization or column chromatography to obtain the target product 3,3',5,5'-tetramethyl-4,4'-dihydroxybiphenyl and its derivatives. The 4-halogenated aromatic phenol compounds are 4-chlorophenol, 4-bromophenol, 4-iodophenol, 4-chloro-2-methylphenol, 4-bromo-2-methylphenol, 4-iodo-2-methylphenol, 4-chloro-2,6-dimethylphenol, 4-bromo-2,6-dimethylphenol, 4-iodo-2,6-dimethylphenol, 4-trifluoromethanesulfonyl-2,6-dimethylphenol, 4-p-toluenesulfonyl-2,6-dimethylphenol, 4-chloro-2,3,6-trimethylphenol, 4-bromo-2,3,6-trimethylphenol, 4-iodo-2,3,6-trimethylphenol, 4-trifluoromethanesulfonyl-2,3,6-trimethylphenol, 4-p-toluenesulfonyl-2,3,6-trimethylphenol, One or more of 4-chloro-2,3,5,6-tetramethylphenol, 4-bromo-2,3,5,6-tetramethylphenol, 4-trifluoromethanesulfonate-2,3,5,6-tetramethylphenol, 4-chloro-2-methoxyphenol, 4-bromo-2-methoxyphenol, 4-iodo-2-methoxyphenol, 4-chloro-2,6-dimethoxyphenol, 4-bromo-2,6-dimethoxyphenol, 4-iodo-2,6-dimethoxyphenol, 4-chloro-2,3,6-trimethoxyphenol, 4-bromo-2,3,6-trimethoxyphenol, 4-iodo-2,3,6-trimethoxyphenol, 4-chloro-2,3,5,6-tetramethoxyphenol, 4-bromo-2,3,5,6-tetramethoxyphenol; The metal catalyst is one or more of nickel chloride, nickel bromide, nickel iodide, nickel sulfate, and palladium acetate; The ligands are pyridine, imidazole, 4-dimethylaminopyridine, bipyridine, 2,9-dimethyl-1,10-phenanthroline (CAS: 484-11-7), 3,4,7,8-tetramethyl-1,10-phenanthroline (CAS: 1660-93-1), 4,7-diphenyl-1,10-phenanthroline (CAS: 1662-01-7), 5,6-dimethyl-1,10-phenanthroline (CAS: 3002-81-1), 4,7-dimethyl-1,10-phenanthroline (CAS: 3248-05-3), one or more of 4,4'-dimethyl-2,2'-bipyridine, 4,4'-dimethoxy-2,2'-bipyridine, 4,4'-di-tert-butyl-2,2'-bipyridine, 5,5'-dimethyl-2,2'-bipyridine, and 6,6'-dimethyl-2,2'-bipyridine; The photocatalyst is one or more of 9-thioxanthone, 10-phenylphenothiazine, tris(2-(4-fluorophenyl)pyridine)iridium(III), fac-tris(2-phenylpyridine)iridium (CAS: 94928-86-6), 5,10-di(2-naphthyl)-5,10-dihydrophenazine, and 5,10-dimethyl-5,10-dihydrophenazine; The solvent is one or more of acetonitrile, 1,4-dioxane, dimethyl sulfoxide, N,N-dimethylformamide, N,N-dimethylacetamide, N-methylpyrrolidone, n-pentane, n-hexane, and cyclohexane; The mixed solvent is one or more of n-pentane, n-hexane, cyclohexane, petroleum ether, methanol, ethanol, n-propanol, isopropanol, n-butanol, isobutanol, tert-butanol, chloroform, toluene, ethyl acetate, acetonitrile, tetrahydrofuran, and 1,4-dioxane.

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