A method of synthesizing benzocyclobutenedione

Abstract

The application belongs to the technical field of organic synthesis, and discloses a method for synthesizing benzocyclobutene ketone; before reaction, nitrogen replacement is performed on the system to ensure an oxygen-free environment; a 2-bromophenyl acetyl chloride compound is added into a reaction container; a metal salt, a ligand, a photocatalyst and a reaction solvent are sequentially added; after all materials are completely dissolved by stirring, a 23-watt compact fluorescent lamp is started as a reaction light source; the reaction is continuously stirred for 24 hours at room temperature and normal pressure; a thin layer chromatography is used to detect the reaction process in real time; after the raw material is completely reacted, the product is separated and purified from the reaction solution to obtain a refined product meeting the purity requirement. The method does not need to use a noble metal catalyst and a toxic ligand, has mild reaction conditions and does not need high-temperature and high-pressure equipment, the raw materials are all commercially available bulk chemicals, the cost is low, the amount of three wastes is low, the product yield and purity are high, there is no obvious yield attenuation in scale-up production, and the method is suitable for the industrial large-scale production demand of benzocyclobutene ketone.

Description

Technical Field

[0001] This invention belongs to the field of organic synthesis technology, and in particular to a method for synthesizing benzocyclobutenone. Background Technology

[0002] With the rapid development of the AI ​​computing power industry, the market demand for high-frequency copper-clad laminates, as the core substrate for computing hardware, continues to rise. Benzocyclobutenone is a key monomer for preparing high-performance benzocyclobutene resins. Its highly active four-membered ring structure endows the resin with excellent properties such as low dielectric constant, high thermal stability, and low curing volatiles, and has broad application prospects in high-end electronic packaging and 5G / 6G high-frequency communication materials.

[0003] Currently, the mainstream synthetic routes for benzocyclobutenones are mainly divided into three categories. The first category is the [2+2] cycloaddition synthesis method, which involves the cycloaddition of α-amino acid-derived chiral enolates with in-situ generated aromatic acetylenes, followed by intramolecular CH acylation to construct the target skeleton. On a small scale, the chiral selectivity of the target product can reach over 92%, and benzocyclobutenone derivatives containing chiral centers can be prepared. However, the regioselectivity of the reaction is highly dependent on the precise temperature control of the reaction system. Temperature fluctuations exceeding 2°C will lead to an increase in the proportion of byproducts of more than 15%. Moreover, the chiral enolizing reagents used need to be custom-synthesized, with a cost of over 500 yuan per gram. The highest yield in laboratory small-scale trials is only 65%, and the yield drops sharply to below 30% after scaling up to the hundred-gram scale. It is only suitable for the synthesis of pharmaceutical intermediates at the milligram level and cannot meet the needs of industrial-scale mass production.

[0004] The second type is the rapid vacuum pyrolysis method of aromatic acyl chloride, which uses o-toluene chloride as raw material and obtains the target product through high-temperature pyrolysis cyclization. No additional catalyst is added during the reaction process, and the amount of waste generated is low. However, the reaction needs to be carried out in a high-temperature environment above 800℃ and a high-vacuum environment below 10Pa. The investment cost of dedicated high-temperature and high-vacuum reaction equipment is 8-10 times that of normal-temperature and normal-pressure reaction equipment. In addition, during continuous production, pyrolysis by-products are prone to coking and clogging on the inner wall of the pipeline. After each batch of production, the machine needs to be shut down for more than 48 hours for cleaning, resulting in high operation and maintenance costs. The maximum production scale of a single batch does not exceed 10kg, which cannot meet the needs of the electronic materials industry with tens of thousands of tons.

[0005] The third type is palladium-catalyzed intramolecular CH acylation, which uses palladium catalysts to mediate CH bond activation and cyclization. It is compatible with various functional groups such as halogens and ester groups on aromatic rings, and the product structure has good adaptability. However, the reaction requires the addition of more than 5 mol% of the precious metal palladium catalyst. The cost of palladium catalyst per ton of raw material exceeds 200,000 yuan. It also requires the use of equivalent-sized highly toxic phosphine ligands and organic bases. The amount of waste generated after the reaction is more than 15 times the product mass. Environmental treatment costs account for more than 40% of the total production cost. At the same time, the reaction yield is generally less than 60%, and the residual palladium metal impurities in the product need to be removed through multiple purification steps, which further increases the cost of the final product.

[0006] Limited by the aforementioned technological bottlenecks, the current global production capacity of benzocyclobutenone is less than 100 tons per year, and it is mainly concentrated in a few specialty chemical companies in Europe, America, and Japan. The domestic market relies on imports, and the unit price has long remained above 2,000 yuan / kg. This not only raises the production costs of domestic high-frequency copper clad laminate companies, but also poses a risk of supply chain disruption. Developing a low-cost, large-scale production process for benzocyclobutenone has become one of the technologies that urgently need to be broken through in my country's high-end electronic materials field. Summary of the Invention

[0007] To address the shortcomings of existing benzocyclobutenone synthesis processes, such as high raw material costs, harsh reaction conditions, difficulty in large-scale production, and heavy burden of waste treatment, this invention provides a method for synthesizing benzocyclobutenone.

[0008] To achieve the above objectives, the present invention adopts the following technical solution: A method for synthesizing benzocyclobutenone includes the following steps: Under a nitrogen atmosphere, 2-bromophenylacetyl chloride compounds were added to the reaction vessel, followed by metal salts, ligands, photocatalysts, and reaction solvents. After stirring until the materials were completely dissolved, a 23W CFL light source was turned on, and the reaction was stirred at room temperature for 24 hours. The reaction progress was monitored by thin-layer chromatography. After the reaction was completed, the product was purified from the reaction solution to obtain a refined product.

[0009] Furthermore, the 2-bromophenylacetyl chloride compound is any one of 2-bromophenylacetyl chloride, 2,4-dibromophenylacetyl chloride, and 4-chloro-2-bromophenylacetyl chloride.

[0010] Furthermore, the metal salt is any one or a combination of nickel chloride, nickel bromide, nickel iodide, and nickel sulfate, and the metal salt is selected from anhydrous substances or hydrates.

[0011] Furthermore, the ligand is any one or more combinations of pyridine, imidazole, bis(2,6-diisopropylphenyl)ethylenediimide, trans-N-(2-pyridylmethylene)aniline, 1,10-o-phenanthroline-5,6-dione, 4-dimethylaminopyridine, bipyridine and its derivatives, o-phenanthroline, 2,9-dimethyl-1,10-phenanthroline, 5,6-dimethyl-1,10-phenanthroline, and 4,7-dimethyl-1,10-phenanthroline.

[0012] Furthermore, the photocatalyst is any one or more combinations of 9-thioxanone, 10-phenylphenthiazine, fac-tris(2-phenylpyridine)iridium, 5,10-di(2-naphthyl)-5,10-dihydrophenazine, and 5,10-dimethyl-5,10-dihydrophenazine.

[0013] Furthermore, the reaction solvent is any one or more combinations of acetonitrile, tetrahydrofuran, 1,4-dioxane, dimethyl sulfoxide, N,N-dimethylformamide, N,N-dimethylacetamide, and N-methylpyrrolidone.

[0014] Furthermore, the product purification process is as follows: the reaction solution is first filtered, the solvent is removed by rotary evaporation, and then separated by column chromatography or recrystallization. The solvent used for column chromatography separation is any one or more combinations of n-pentane, n-hexane, cyclohexane, petroleum ether, methanol, ethanol, n-propanol, isopropanol, n-butanol, isobutanol, tert-butanol, dichloromethane, chloroform, toluene, ethyl acetate, acetonitrile, tetrahydrofuran, and 1,4-dioxane.

[0015] Furthermore, the molar ratio of each reactant is as follows: 1.0 equivalent of 2-bromophenylacetyl chloride compound, 0.05 equivalent of metal salt, 0.06 equivalent of ligand, and 0.1 equivalent of photocatalyst.

[0016] The present invention has the following beneficial effects: This invention employs a dual-catalytic synergistic system constructed with nickel salts and commercially available organic photocatalysts to replace the precious palladium catalyst, highly toxic phosphine ligand, and custom chiral enolization reagent in the [2+2] cycloaddition process of existing palladium catalysis processes. All catalytic components are commercially available bulk industrial chemicals, with procurement costs lower than 20% of existing palladium catalysis systems. It also avoids the problem of precious palladium residue and eliminates the need to treat highly toxic phosphine-containing waste liquid. The amount of waste generated is only one-sixth of that of existing palladium catalysis processes, reducing environmental treatment costs and effectively solving the defects of existing synthesis processes, such as high raw material costs, heavy waste treatment burden, and excessive heavy metal residues in products.

[0017] This invention employs a visible light-mediated CH activation cyclization reaction pathway. The entire reaction process can be completed under normal temperature and pressure conditions, eliminating the need for specialized reaction equipment requiring temperatures above 800°C and high vacuum below 10Pa as needed for the pyrolysis process of aromatic acyl chlorides, and the stringent temperature control requirements of ±2°C for the [2+2] cycloaddition process. Mass production can be achieved using only a standard atmospheric pressure enamel-lined reactor commonly used in chemical production, coupled with a visible light source. The equipment investment cost is only one-eighth of that of the pyrolysis process. Furthermore, it avoids the problems of byproduct coking and clogging of pipelines, which necessitate frequent shutdowns for cleaning, as seen in the pyrolysis process. Continuous production can be achieved, with single-batch production scales increasing to the ton level or above. The reaction process is free from the risks of high temperature and high pressure, significantly reducing safety management costs. This effectively solves the shortcomings of existing processes, such as harsh reaction conditions, high equipment investment, high maintenance costs, and difficulty in achieving large-scale mass production.

[0018] The dual-catalytic synergistic system of this invention exhibits excellent reaction selectivity, with a high regioselectivity for the target product, low side reaction rate, stable yield in small-scale trials, and no significant yield decline after scaling up to 500 mmol. It is expected to be scaled up to ton-scale, which is far superior to the problem of sharp yield drop after scale-up of the existing [2+2] cycloaddition process at the gram level. At the same time, due to the extremely low proportion of by-products, the product only needs one recrystallization to meet the purity requirements for electronic applications, eliminating the need for multi-step column chromatography purification or removal of precious metal residues. The purification cost is only one-third of that of the existing process. Furthermore, this catalytic system is compatible with various substituents such as halogens, alkyl groups, alkoxy groups, and ester groups on the aromatic ring, and can be adapted to the synthesis of benzocyclobutenone derivatives with different functional modification requirements. It effectively solves the defects of the existing process, such as unstable yield during scale-up, complex purification process, and narrow substrate compatibility.

[0019] This process is highly compatible with existing fine chemical mass production lines, and can be quickly implemented for mass production without large-scale modifications to existing production facilities. The cost of the prepared benzocyclobutene ketone is only about one-quarter of that of imported products, which can effectively reduce the production cost of high-end benzocyclobutene resin in China. Attached Figure Description

[0020] Figure 1 This invention provides a chemical reaction formula for the synthesis of benzocyclobutenone. Figure 2 This is a grouped bar chart comparing the separation yield and product purity of different processes proposed in this invention; Figure 3 This is a horizontal bar chart comparing the relative costs of raw materials and the relative amounts of waste generated in different processes proposed in this invention. Figure 4 A radar chart comparing the core performance indicators proposed in this invention. Detailed Implementation

[0021] The following will refer to the appendices in the embodiments of the present invention. Figure 1-4 The technical solutions in the embodiments of the present invention are clearly and completely described herein. Obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0022] (I) Explanation of the expansion of core technical features Nitrogen atmosphere: The reaction vessel is evacuated and purged with nitrogen three times before the reaction to ensure that the oxygen content of the system is below 100 ppm. This avoids the oxidation and deactivation of the active species of zero-valent nickel catalyst, reduces the occurrence of side reactions, and solves the problems of many by-products and high purification difficulty in the existing process.

[0023] 2-Bromophenylacetyl chloride compounds are used as raw materials: all raw materials are commercially available industrial-grade products, no custom synthesis is required, and the procurement cost is less than 1% of the chiral reagents used in the existing [2+2] cycloaddition process, thus solving the problem of high raw material costs in the existing process.

[0024] Catalytic system feed: A synergistic catalytic system of nickel salt and organic photocatalyst is adopted to replace the precious metal palladium catalyst and highly toxic phosphine ligand in the existing process. All components are commercially available and readily available bulk chemicals, which are low in cost and have no risk of high toxicity, thus solving the defects of high catalyst cost and heavy waste treatment burden in the existing process.

[0025] 23W CFL light source irradiation: Using ordinary commercially available compact fluorescent lamps as the light source, no special light reaction equipment is required, and the equipment investment cost is only one-eighth of that of the existing pyrolysis process, solving the problem of high equipment investment in the existing process.

[0026] 24-hour room temperature reaction: The reaction does not require heating or precise temperature control and can be carried out at room temperature and pressure. It does not require the 800℃ high temperature and high vacuum or ±2℃ precise temperature control requirements of existing processes, thus solving the defects of harsh reaction conditions and high operation and maintenance costs of existing processes.

[0027] Thin-layer chromatography detection of reactions: simple operation, real-time monitoring of reaction endpoints, avoiding incomplete or excessive reactions, and improving yield stability.

[0028] Product purification: Electronic-grade products can be obtained simply by filtration, rotary evaporation, column chromatography, or recrystallization, without the need for multi-step purification or removal of precious metal residues. The purification cost is only one-third of that of existing processes, solving the problem of complex purification processes in existing processes.

[0029] (II) Core Implementation Examples and Comparative Examples Example 1 (10 mmol small-scale test) Under a nitrogen atmosphere, 0.110 g (0.6 mmol) of 4,4'-dimethyl-2,2'-bipyridine, 0.119 g (0.5 mmol) of nickel chloride hexahydrate, and 0.212 g (1.0 mmol) of 9-thioxanthone were added to a 50 mL round-bottom flask. The flask was evacuated three times under nitrogen atmosphere. Then, 10 mL of DMF solvent was added to the flask, and the mixture was stirred at room temperature for 1 h. 2.32 g (10 mmol) of 2-bromophenylacetyl chloride was dissolved in 30 mL of DMF and added to the above mixture. The reaction solution was irradiated with a 23 W CFL light source and stirred for 24 h. The reaction progress was monitored by TLC. After the reaction was completed, the reaction solution was separated by column chromatography (n-hexane:ethyl acetate = 5:1) to obtain 1.092 g of benzocyclobutenone, with a separation yield of 91%. The purity of the product was 99.8% as determined by gas chromatography. Example 2

[0030] Under a nitrogen atmosphere, 2.21 g (12 mmol) of 4,4'-dimethyl-2,2'-bipyridine, 2.38 g (10 mmol) of nickel chloride, and 4.24 g (20 mmol) of 9-thioxanthone were added to a 500 mL round-bottom flask. The flask was evacuated three times under nitrogen atmosphere. Then, 50 mL of DMF solvent was added to the flask, and the mixture was stirred at room temperature for 1 h. 46.39 g (200 mmol) of 2-bromophenylacetyl chloride was dissolved in 300 mL of DMF and added to the above mixture.

[0031] The reaction solution was irradiated with a 23W CFL light source and stirred for 24 h. The reaction was monitored by TLC. After the reaction was complete, the reaction solution was quenched with 1 M hydrochloric acid, followed by extraction with 200 mL ethyl acetate and separation. The organic phase was dried and then evaporated to dryness to obtain the crude product. The crude product was recrystallized from a mixed solvent of n-hexane and ethyl acetate (5:1), yielding 21.32 g of benzocyclobutenone in 90% yield. The purity of the product was 99.8% as determined by gas chromatography. The NMR characterization data were as follows: 1 H NMR: (400 MHz, DMSO) δ 7.64 - 7.51 (m, 2H), 7.41 (t, J = 7.1 Hz, 1H), 7.35 (d, J = 7.6 Hz, 1H), 3.93 (s, 2H); 13 C NMR: (101 MHz, DMSO) δ 188.98, 151.77, 147.77, 135.96, 129.34, 124.40, 120.85, 52.55, 39.37. Example 3

[0032] Under a nitrogen atmosphere, 2.21 g (12 mmol) of 4,4'-dimethyl-2,2'-bipyridine, 2.19 g (10 mmol) of nickel bromide, and 5.47 g (20 mmol) of 10-phenylphenthiazide were added to a 500 mL round-bottom flask. The flask was evacuated three times under nitrogen atmosphere. Then, 50 mL of DMA solvent was added to the flask, and the mixture was stirred at room temperature for 1 h. 61.97 g (200 mmol) of 2,4-dibromophenylacetyl chloride was dissolved in 300 mL of DMA and added to the above mixture.

[0033] The reaction solution was irradiated with a 23W CFL light source and stirred for 24 h. The reaction progress was monitored by TLC. After the reaction was complete, the reaction solution was quenched with 1 M hydrochloric acid, followed by extraction with 200 mL ethyl acetate and separation. The organic phase was dried and then evaporated to dryness to obtain the crude product. The crude product was recrystallized from a mixed solvent of n-hexane and ethyl acetate (5:1), yielding 31.62 g of 4-bromobenzocyclobutenone in 81% yield. The purity of the product was 99.7% as determined by gas chromatography. The NMR characterization data were as follows: 1 H NMR: (400 MHz, DMSO) δ = 7.72 (s, 1H), 7.58 (d, J = 8.1 Hz, 1H), 7.22 (d, J = 8.1 Hz, 1H), 4.00 (s, 2H); 13 C NMR: (101 MHz, DMSO) δ = 186.9, 152.4, 146.5, 132.6, 130.1, 127.4, 122.0, 52.4. Example 4

[0034] Under a nitrogen atmosphere, 5.50 g (30 mmol) of 4,4'-dimethyl-2,2'-bipyridine, 5.95 g (25 mmol) of nickel chloride hexahydrate, and 10.61 g (50 mmol) of 9-thioxanthone were added to a 5000 mL reactor. The reactor was evacuated three times with nitrogen. Then, 250 mL of DMF solvent was added to the reactor, and the mixture was stirred at room temperature for 1 h. 116.0 g (500 mmol) of 2-bromophenylacetyl chloride was dissolved in 750 mL of DMF and added to the above mixture.

[0035] The reaction solution was irradiated with a 23W CFL light source array and stirred for 24 hours. The reaction progress was monitored by TLC. After the reaction was completed, the reaction solution was quenched with 1 M hydrochloric acid, then extracted with ethyl acetate, dried the organic phase, filtered, and most of the solvent was removed by rotary evaporation. Recrystallization was then performed with a mixed solvent of n-hexane:ethyl acetate = 5:1 to obtain 53.2 g of purified product benzocyclobutenone, with a separation yield of 90%. The purity of the product was 99.8% as determined by gas chromatography. Example 5

[0036] Under a nitrogen atmosphere, 2.67 g (10 mmol) of 4-chloro-2-bromophenylacetyl chloride (1.0 equivalent) was added to a 50 mL round-bottom flask. Then, a mixture of 0.060 g nickel chloride and 0.156 g nickel iodide (0.05 equivalent), a mixture of 0.047 g bipyridine and 0.073 g 4-dimethylaminopyridine (0.06 equivalent), and 0.208 g 5,10-dimethyl-5,10-dihydrophenazine (0.1 equivalent) were added sequentially. 10 mL of N,N-dimethylformamide was added as the reaction solvent. The mixture was stirred until completely dissolved, and a 23 W CFL light source was turned on. The reaction was stirred at room temperature for 24 h. The reaction progress was monitored using thin-layer chromatography, and the reaction was stopped when the starting material spot completely disappeared. After the reaction was completed, the reaction solution was filtered, most of the solvent was removed by rotary evaporation, and then column chromatography was performed using a mixed solvent of petroleum ether and ethyl acetate in a ratio of 5:1 to obtain 1.29 g of purified product 4-chlorobenzocyclobutenone, with a separation yield of 84%. The purity of the product was 99.7% as determined by gas chromatography.

[0037] Comparative Example This comparative example employed palladium-catalyzed intramolecular CH acylation. Under a nitrogen atmosphere, 1.0 equivalent of 2.32 g (10 mmol) of 2-bromophenylacetyl chloride was added to a 50 mL round-bottom flask, followed by 0.05 equivalent of 0.578 g of tetrakis(triphenylphosphine)palladium, 0.2 equivalent of 0.525 g of triphenylphosphine, and 2 equivalent of 6.52 g of cesium carbonate. 10 mL of toluene was added as the reaction solvent. After stirring until the materials were completely dissolved, the mixture was heated to 120 °C and refluxed for 12 h. The reaction progress was monitored by thin-layer chromatography, and the reaction was stopped when the starting material spot completely disappeared. After the reaction was completed, the reaction solution was filtered, and most of the solvent was removed by rotary evaporation. Then, column chromatography was performed using a mixed solvent of petroleum ether and ethyl acetate in a ratio of 5:1. Palladium residue was removed by recrystallization three times (the palladium residue was found to be less than 5 ppm by ICP-MS) to obtain 0.685 g of purified product benzocyclobutenone, with a separation yield of 58%. The purity of the product was 99.2% as determined by gas chromatography.

[0038] Experimental data tables and explanations Table 1 Comparison of Process Parameters This table summarizes the core process parameters of each embodiment and comparative example. The parameters of all embodiments fall within the technical requirements. The reactions are all carried out under normal temperature and pressure conditions, without the need for precious metal palladium catalysts and high-temperature reaction equipment. The catalytic components are all commercially available bulk chemicals. The comparative examples use existing palladium catalysis processes, which require precious metal catalysts and high-temperature reaction conditions of 120°C. The equipment requirements are high, the ligands are highly toxic, and the treatment of waste is difficult.

[0039] Table 2 Performance Comparison Table This table summarizes the core performance data of each embodiment and comparative example. The separation yield of the embodiments is higher than that of the comparative examples, the product purity meets the requirements of electronic-grade applications, the raw material cost is less than 17% of that of the comparative examples, the amount of waste generated is less than 17% of that of the comparative examples, and the yield decay rate after scaling up to 500 mmol is less than 3%. The comparative examples have low yield, high raw material cost, large amount of waste, and the yield decay exceeds 40% after scaling up, which verifies the effectiveness of the process of the present invention in solving the defects of the prior art.

[0040] refer to Figure 2 This figure visually illustrates the performance differences of the core products of the various embodiments of the present invention compared with existing palladium catalytic processes. The separation yield of all embodiments is higher than that of the comparative example, exceeding it by up to 33 percentage points, thus solving the defects of low yield in existing palladium catalysis and [2+2] cycloaddition processes. Simultaneously, the purity of the products in all embodiments reaches over 99.7%, meeting the purity requirements of resin monomers for electronic-grade high-frequency copper-clad laminates. No additional precious metal residue removal process is required, overcoming the defects of high heavy metal residue and complex purification processes in existing palladium catalytic processes. This verifies the reaction selectivity advantage of the catalytic system of the present invention and provides data support for performance benchmarking of subsequent mass production processes.

[0041] refer to Figure 3 This figure uses the raw material cost and waste generation as a baseline of 100 to visually demonstrate the cost and environmental advantages of the process of this invention. The relative raw material cost of all embodiments does not exceed 17, which is less than 17% of that of existing palladium catalytic processes. It eliminates the need for precious metal palladium catalysts, customized chiral reagents, and highly toxic phosphine ligands, thus solving the problem of high raw material costs in existing processes. At the same time, the relative waste generation of all embodiments does not exceed 17, which is less than 17% of that of existing palladium catalytic processes. It eliminates the need to treat highly toxic waste liquids containing palladium and phosphine, reducing environmental treatment costs and solving the problem of heavy waste treatment burden in existing processes. It can provide intuitive data support for the economic accounting of the process.

[0042] refer to Figure 4 This radar chart comprehensively compares the overall performance of the present invention's process with existing palladium catalytic processes across five core dimensions. The present invention outperforms existing processes in four dimensions: separation yield, raw material cost advantage, waste reduction advantage, and scale-up stability. Only the product purity dimension is similar to existing processes, yet still meets higher requirements for electronic-grade applications. The present invention addresses the core shortcomings of existing processes, including low yield, high cost, excessive waste, and poor scale-up stability, systematically demonstrating its comprehensive competitiveness. This radar chart visually presents the extent of the improvements made by the present invention compared to existing technologies, providing a clear performance reference for downstream customers in process selection.

[0043] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A method for synthesizing benzocyclobutenone, characterized in that, The process includes the following steps: Under a nitrogen atmosphere, 2-bromophenylacetyl chloride compounds are added to a reaction vessel, followed by metal salts, ligands, photocatalysts, and reaction solvents. After stirring until the materials are completely dissolved, a 23W CFL light source is turned on, and the reaction is stirred at room temperature for 24 hours. The reaction progress is monitored by thin-layer chromatography. After the reaction is completed, the product is purified from the reaction solution to obtain a refined product.

2. The method for synthesizing benzocyclobutenone according to claim 1, characterized in that, The 2-bromophenylacetyl chloride compound is any one of 2-bromophenylacetyl chloride, 2,4-dibromophenylacetyl chloride, and 4-chloro-2-bromophenylacetyl chloride.

3. The method for synthesizing benzocyclobutenone according to claim 1, characterized in that, The metal salt is any one or a combination of nickel chloride, nickel bromide, nickel iodide, and nickel sulfate, and the metal salt is selected from anhydrous substances or hydrates.

4. The method for synthesizing benzocyclobutenone according to claim 1, characterized in that, The ligand is any one or a combination of pyridine, imidazole, bis(2,6-diisopropylphenyl)ethylenediimide, trans-N-(2-pyridylmethylene)aniline, 1,10-o-phenanthroline-5,6-dione, 4-dimethylaminopyridine, bipyridine and its derivatives, o-phenanthroline, 2,9-dimethyl-1,10-phenanthroline, 5,6-dimethyl-1,10-phenanthroline, and 4,7-dimethyl-1,10-phenanthroline.

5. The method for synthesizing benzocyclobutenone according to claim 1, characterized in that, The photocatalyst is any one or a combination of 9-thioxanone, 10-phenylphenthiazine, fac-tris(2-phenylpyridine)iridium, 5,10-di(2-naphthyl)-5,10-dihydrophenazine, and 5,10-dimethyl-5,10-dihydrophenazine.

6. The method for synthesizing benzocyclobutenone according to claim 1, characterized in that, The reaction solvent is any one or a combination of acetonitrile, tetrahydrofuran, 1,4-dioxane, dimethyl sulfoxide, N,N-dimethylformamide, N,N-dimethylacetamide, and N-methylpyrrolidone.

7. The method for synthesizing benzocyclobutenone according to claim 1, characterized in that, The process for purifying the product is as follows: The reaction solution is first filtered, and the solvent is removed by rotary evaporation. Then, column chromatography or recrystallization is used for separation. The solvent used for column chromatography separation is any one or more combinations of n-pentane, n-hexane, cyclohexane, petroleum ether, methanol, ethanol, n-propanol, isopropanol, n-butanol, isobutanol, tert-butanol, dichloromethane, chloroform, toluene, ethyl acetate, acetonitrile, tetrahydrofuran, and 1,4-dioxane.

8. The method for synthesizing benzocyclobutenone according to claim 1, characterized in that, The molar ratio of each reactant is as follows: 1.0 equivalent of 2-bromophenylacetyl chloride compound, 0.05 equivalent of metal salt, 0.06 equivalent of ligand, and 0.1 equivalent of photocatalyst.

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