A method for photosynthesis of ortho-dihalogenated compounds based on non-corrosive inorganic halide salts

Abstract

This invention discloses a method for the photosynthesis of vicinal dihalogenated compounds using non-corrosive inorganic halide salts under photoactive conditions. The method comprises: directly converting aromatic olefin compounds into vicinal dihalogenated compounds R-X2 using metal halide salts under light irradiation, where R is an aromatic olefin compound and X is any one of F, Cl, Br, and I. This invention uses inexpensive and safe inorganic halide salts as the halogen source and reacts at room temperature and pressure, eliminating the need for additional photocatalysts, halogen elements, and oxidants. It exhibits high selectivity, is environmentally friendly, and can replace existing vicinal dihalogenated compound synthesis reaction systems, making it suitable for large-scale production.

Description

Technical Field

[0001] This invention relates to a method for synthesizing ortho-dihalogenated compounds, and more particularly to a method for photosynthesizing halogenated compounds using non-corrosive inorganic halide salts. It also relates to a method for photosynthesizing halogenated compounds using non-corrosive inorganic halide salts as a substitute for organic halogen sources under conditions without a photocatalyst, belonging to the field of organic synthesis technology. Background Technology

[0002] Photo-driven processes refer to chemical reactions directly induced by light, enabling the conversion of primary energy sources into end-use energy for humans. The energy conversion process is simple and highly efficient. Its advantages of low energy consumption and cleanliness align with the concepts of green production and green synthesis, and have garnered widespread attention in the field of organic synthesis.

[0003] Ortho-dihalogenated compounds are important intermediates in drug synthesis. Currently, their preparation often relies on toxic and highly corrosive halogen elements (Cl₂, Br₂) or organic halogen sources (N-bromosuccinimide, NBS), and requires the introduction of strong oxidants into the system. This makes the production of ortho-dihalogenated compounds quite dangerous and prone to environmental pollution. Furthermore, the need to prepare and screen suitable catalysts makes subsequent purification and impurity removal more difficult, further increasing production costs. Using inexpensive and abundant inorganic metal halide salts as halogen sources to achieve photo-driven synthesis of ortho-dihalogenated compounds can not only solve the environmental pollution problem but also further reduce production costs.

[0004] Existing technologies use hydrogen chloride gas as a chlorine source to prepare dichloro compounds, but the chlorine source used in the reaction is toxic and harmful hydrogen chloride gas, requiring reflux circulation under high temperature conditions, which is complex, hazardous, and time-consuming. Existing technologies use inorganic metals as halogen sources to prepare chloro compounds, but the reaction can only produce monohalogenated compounds, failing to yield ortho-dihalogenated compounds, and this method requires photoactive reagents.

[0005] In summary, current methods for synthesizing vicinal dihalogenated compounds still suffer from problems such as strong corrosiveness of the halogen source, complex operation, and unstable halogen source, which are unfavorable for large-scale industrial production. Therefore, research on new methods for the efficient, green, and economical synthesis of vicinal dihalogenated compounds is of great value. Using inexpensive and readily available inorganic metal halide salts to synthesize vicinal dihalogenated compounds is beneficial for the application of this method in practical production. Summary of the Invention

[0006] To address the aforementioned technical problems, the present invention aims to provide a green, environmentally friendly, and efficient method for synthesizing ortho-dihalogenated compounds in air without a photocatalyst, based on the substitution of halogen elements with inorganic metal halide salts.

[0007] The present invention adopts the following technical solution:

[0008] A method for photosynthesizing vicinal dihalogenated compounds based on non-corrosive inorganic halide salts includes the following steps: in the presence of acid, using metal halide salts and aromatic olefin compounds as raw materials, a photochemical reaction is carried out to synthesize vicinal dihalogenated compounds; wherein the aromatic olefin compounds contain terminal alkenyl groups.

[0009] A method for continuous photosynthesis of ortho-dihalogenated compounds based on non-corrosive inorganic halide salts includes the following steps:

[0010] (1) In the presence of acid, metal halide salts and aromatic olefin compounds are used as raw materials for photoreaction;

[0011] (2) Then add a metal halide and react under light;

[0012] (3) Repeat step (2) to synthesize the ortho-dihalogenated compound;

[0013] The aromatic olefin compound contains a terminal alkenyl group.

[0014] In this invention, the structure of the aromatic olefin compound is shown in the following formula:

[0015]

[0016] The structure of the ortho-dihalogenated compound is shown in the following formula:

[0017]

[0018] In the above chemical structural formula, R represents 1, 2, 3, 4 or 5 substituents attached to the benzene ring, each of which is independently hydrogen, halogen, C1-C10 alkyl or alkenyl or alkynyl, C6-C20 aryl, -CF3, -C(=O)OH and -C(=O); R1 and R2 are halogens, preferably R1 and R2 are the same halogen, such as any one of F, Cl, Br and I.

[0019] In this invention, the metal halide is a non-corrosive inorganic halide with the chemical formula MXn, where M is a metal and X is a halogen. Preferably, M is any one or a mixture of group III-VIII transition metals, such as manganese, copper, nickel, iron, and cobalt; X is any one of F, Cl, Br, and I; and n is a non-zero integer. Preferably, the metal halide is a non-corrosive transition metal halide, and a combination of one or more of manganese chloride, copper chloride, nickel chloride, ferrous chloride, cobalt chloride, manganese bromide, copper bromide, nickel bromide, ferrous bromide, and cobalt bromide.

[0020] In this invention, the acid is one or a combination of several of the following: H2SO4, HNO3, HCl, HClO4, CF3COOH, CH3COOH, H2C2O4, and HCOOH.

[0021] In this invention, the illumination is provided by a xenon lamp, LED, halogen lamp, or mercury lamp with a power of 0.01 to 100 W, and the wavelength of the illumination is 300 to 1100 nm; the temperature of the photo-irradiation reaction is -50°C to 100°C, preferably 20 to 50°C, such as room temperature; the time is 1 h to 24 h, preferably 1 h to 15 h, even more preferably 1 h to 10 h, further preferably 1 h to 5 h, and even more preferably 1 h to 3 h.

[0022] Preferably, the present invention enables continuous photosynthesis of ortho-dihalogenated compounds based on non-corrosive inorganic halide salts using only light irradiation without the need for heating.

[0023] In this invention, the photoreaction is carried out in the presence of a solvent; the solvent includes... N , N - One or more of dimethylformamide, dimethyl sulfoxide, acetonitrile, n-hexane, 1,4-dioxane, cyclohexane, and ethyl acetate.

[0024] In this invention, during the photo-irradiation reaction, the concentration of the acid is 0–30 μL / mL, the concentration of the metal halide is 50–150 mg / mL, and the concentration of the aromatic olefin compound is 5–50 mM.

[0025] This invention discloses a method for photosynthesizing vicinal dihalogenated compounds based on the substitution of organic halogen sources with non-corrosive inorganic halide salts. The method includes the following steps: under light irradiation, using metal halide salts, acids, and organic solvents, aromatic olefin compounds are converted into vicinal dihalogenated compounds R`-X2, wherein R` is the structure of the aromatic olefin compound after the terminal double bond is opened, and X is any one of halogens F, Cl, Br, and I.

[0026] In the above technical solution, the wavelength of the illumination is 300–1100 nm; visible light is preferred.

[0027] In the above technical solution, the solvent is N , N - One or a combination of several of the following: dimethylformamide, dimethyl sulfoxide, acetonitrile, n-hexane, 1,4-dioxane, cyclohexane, and ethyl acetate.

[0028] In the above technical solution, in the method of continuous photosynthesis of ortho-dihalogenated compounds based on non-corrosive inorganic halide salts, after step (2) is completed, the metal halide salt is separated, and then acid and aromatic olefin compounds are added as raw materials to carry out step (3) to continuously synthesize ortho-dihalogenated compounds.

[0029] Specifically, the method for photosynthesizing ortho-dihalogenated compounds based on non-corrosive inorganic halide salts includes the following steps:

[0030] (1) A mixed solution is obtained by ultrasonic dispersion of metal halide salt, acid and aromatic olefin compound in solvent;

[0031] (2) The mixed solution is irradiated with 1 to 10 W light and reacted at -50 to 100 °C for 1 to 24 h;

[0032] (3) After centrifugation, the separated organic phase is dried and concentrated to obtain the ortho-dihalogenated compound.

[0033] In the mixed solution, the concentration of acid is 5–30 μL / mL, the concentration of metal halide is 70–120 mg / mL, and the concentration of aromatic olefin compound is 15–30 mM.

[0034] This can be achieved using xenon lamps, LEDs, halogen lamps, or mercury lamps with a light source power of 0.01-100 W.

[0035] The reaction temperature is controlled by an ice bath, water bath, or oil bath.

[0036] The method for photosynthesizing ortho-dihalogenated compounds based on non-corrosive inorganic halide salts according to this invention is illustrated below:

[0037]

[0038] The method for photosynthesizing tho-dihalogen compounds based on non-corrosive inorganic halide salts described in this invention is a method for photo-driven continuous synthesis of tho-dihalogen compounds. Importantly, this method does not contain organic halogen sources or photocatalysts. In particular, the method of this invention does not require the addition of additional photoactive agents (also known as photocatalysts) and can photo-driven continuous synthesis of tho-dihalogen compounds in air.

[0039] In this invention, the method for continuous synthesis of vicinal dihalogenated compounds via light-driven synthesis includes the step of continuously adding metal halide salts to synthesize vicinal dihalogenated compounds. Specifically, after step (2) is completed, inorganic halide salts are added continuously, and step (2) is repeated to continuously synthesize vicinal dihalogenated compounds without the need for the addition of new metal halide salts; the inorganic halide salts used are inexpensive halide salts, such as one or a combination of several of MnCl2, CuCl2, NiCl2, FeCl2, CoCl2, MnBr2, CuBr2, NiBr2, FeBr2, and CoBr2.

[0040] The method of continuous photo-driven synthesis of halogenated compounds based on inorganic halide salts replacing halogen elements in this invention can achieve dihalogenation of hydrocarbon compounds to obtain the corresponding halogenated compounds. It has high selectivity, low photo-driven cost, and is green and pollution-free. It is beneficial to use this reaction system stably and efficiently in industrial organic synthesis to release its high economic value. Attached Figure Description

[0041] Figure 1 This is a time-kinetic curve of the chlorination reaction of styrene.

[0042] Figure 2 This is a gas chromatogram of the product obtained from the chlorination reaction of styrene.

[0043] Figure 3 The mass spectrum of the product obtained from the chlorination reaction of styrene is compared with the standard NIST mass spectrum.

[0044] Figure 4 The NMR spectrum of dichlorostyrene is 1H NMR.

[0045] Figure 5 This is the carbon NMR spectrum of dichlorostyrene.

[0046] Figure 6 Time-kinetic curve of styrene bromination reaction.

[0047] Figure 7 This is a gas chromatogram of the product obtained from the bromination of styrene.

[0048] Figure 8 The mass spectrum of the product obtained from the bromination of styrene is compared with the standard NIST mass spectrum.

[0049] Figure 9 To determine the yield and selectivity of continuous production of styrene dichloride. Detailed Implementation

[0050] This invention relates to a method for the photo-induced continuous synthesis of ortho-dihalogenated compounds based on the substitution of organic halogen sources with inorganic metal halide salts under photocatalyst-free conditions. In the presence of light, aromatic olefin compounds can be continuously converted into ortho-dihalogenated compounds in air, with halogens being F, Cl, Br, and I.

[0051] In this invention, vicinal dihalogenated compounds are synthesized by reacting metal halide salts and aromatic olefin compounds with light in the presence of acid and solvent, using them as raw materials; no other reagents or photocatalysts are required, and the reaction conditions are simple.

[0052] In a specific embodiment of the present invention, in the inorganic metal halide MXn, M is any one or more metals from Groups I-III and I-VIII, preferably M is any one of Mn, Cu, Ni, Fe, and Co, and n is a non-zero integer, preferably 1 to 3. X is any one of F, Cl, Br, and I. Preferably, the inorganic metal halide is selected from one or more combinations of MnCl2, CuCl2, NiCl2, FeCl2, CoCl2, MnBr2, CuBr2, NiBr2, FeBr2, and CoBr2.

[0053] The above-mentioned method for the photocatalytic continuous synthesis of vicinal dihalogenated compounds based on the substitution of halogen elements with inorganic metal halide salts under photocatalyst-free conditions includes the following steps: (a) adding a metal halide salt, an acid, and an aromatic olefin compound to a solvent and ultrasonically dispersing them to obtain a mixed solution; (b) stirring the mixture under 0.01-100 W light irradiation and controlling the reaction temperature at -50-100 ℃, preferably room temperature; (c) centrifuging the mixed phase, drying and concentrating the separated organic phase to obtain the halogenated compound. Further, after step (b), an inorganic metal halide salt is added again and this step is repeated. After the final reaction is completed, step (c) is performed to achieve the photocatalytic continuous synthesis of vicinal dihalogenated compounds.

[0054] In one specific embodiment of the present invention, the intensity of the illumination is achieved by a xenon lamp, LED, halogen lamp or mercury lamp with a wavelength of 300-1100 nm and a light source power of 0.01-100 W.

[0055] In one specific embodiment of the present invention, the acid is one or a combination of several of H2SO4, HNO3, HCl, HClO4, CF3COOH, CH3COOH, H2C2O4, and HCOOH, with a concentration of 5–25 μL / mL.

[0056] In one specific embodiment of the present invention, the reaction temperature is controlled by an ice bath, a water bath, or an oil bath.

[0057] The following specific experiments illustrate the technological advancements of this invention. The raw materials involved are all existing products, and the specific preparation operations and performance tests are all conventional techniques. Unless otherwise specified, the reaction is carried out in air under light without the need for additional heating. The yield of the target product is determined by gas chromatography during the experiment. Example 1

[0058] This example provides a method for the photocatalytic synthesis of halo compounds based on the substitution of halogen elements with inorganic halide salts under photocatalyst-free conditions, including the following steps:

[0059] (1) Mix 1.5 mmol FeCl2, 2 mL acetonitrile, 20 mM styrene and 15 μL concentrated hydrochloric acid (37%) evenly and then disperse by ultrasonication to obtain a suspension.

[0060] (2) The well-dispersed suspension was placed in a 0.35 W (0.07 W / cm) atmosphere. 2 The mixture was stirred and reacted for 2 hours under simulated sunlight LED light irradiation at room temperature and air conditions; then the resulting organic phase was dried and concentrated to obtain styrene dichloride.

[0061]

[0062] (3) After the reaction was completed, the liquid was separated from the inorganic halide salt in the reaction system by centrifugation. The supernatant was then used to analyze the conversion rate of the reactants and the yield of the target product using a gas chromatograph. The final experimental results showed that the yield of styrene dichloride was 85% and the selectivity was 95%.

[0063] Figure 1 The time-kinetic curve for the chlorination reaction of styrene to produce styrene dichloride is shown. The reaction was completed in 120 min, and the yield of styrene dichloride was 85%, with a selectivity of 95%. Figure 2 This is a gas chromatogram of the product obtained from the chlorination reaction of styrene. Figure 3 The mass spectrum of the product obtained from the chlorination reaction of styrene is compared with the standard NIST mass spectrum. Figure 4 as well as Figure 5 The carbon and hydrogen spectra of the products obtained from the chlorination reaction of styrene are shown.

[0064] Existing technologies use FeCl3 as an inorganic metal chlorine source to prepare styrene dichloride. However, FeCl3 is highly corrosive and environmentally unfriendly, and the reaction requires an argon atmosphere and takes up to 10 hours. This invention solves these problems by using inorganic metal halide salts instead of elemental halogens for the light-driven synthesis of ortho-dihalogen compounds. Irradiation in air for 2 hours achieves a styrene dichloride yield of 85% and a selectivity of 95%.

[0065] Comparative Example 1

[0066] This comparative example uses FeCl3 as an inorganic metal chlorine source to prepare styrene dichloride. It is the same as Example 1, except that in step (1), 1.5 mmol of FeCl2 is replaced with 1.5 mmol of FeCl3·6H2O, and 15 μL of concentrated hydrochloric acid is omitted. The rest is the same. Finally, the styrene dichloride yield was 61% and the selectivity was 62% when tested and analyzed by gas chromatography. Example 2

[0067] This example provides a method for the photocatalytic synthesis of ortho-dihalogenated compounds based on inorganic halide salts replacing halogen elements under photocatalyst-free conditions. It is similar to Example 1, but with the following differences:

[0068] In step (1), 1.5 mmol of FeCl2 was replaced with 1 mmol of FeBr2, and 15 μL of concentrated hydrochloric acid was replaced with 30 μL of hydrobromic acid (48 wt.%). The rest remained the same. Finally, the styrene dibromide yield was 78% and the selectivity was 98% when tested and analyzed by gas chromatography.

[0069]

[0070] Figure 6 The time-kinetic curve for the bromination of styrene to form styrene dibromide is shown. The reaction was completed in 120 min, and the yield of styrene dibromide was 78%, with a selectivity of 98%.

[0071] Figure 7 This is a gas chromatogram of the product obtained from the bromination of styrene. Figure 8 The mass spectrum of the product obtained from the bromination of styrene is compared with the standard NIST mass spectrum. Example 3

[0072] This example provides a method for the photocatalytic synthesis of ortho-dihalogenated compounds based on the substitution of halogen elements with inorganic halide salts under photocatalytic conditions. Referring to Example 1, the difference is that in step (1), 1.5 mmol of FeCl2 is replaced with 1 mmol of FeBr2 and 15 μL of concentrated hydrochloric acid is replaced with 50 μL of hydrobromic acid. Finally, the styrene dibromide yield was 85% and the selectivity was 93% as determined by gas chromatography. Example 4

[0073] This example provides a method for the light-driven synthesis of ortho-dihalogenated compounds based on the substitution of halogen elements with inorganic halide salts. Referring to Example 1, the difference is that styrene in step (1) is replaced with 4-chlorostyrene, while the rest is the same. Finally, the 4-chlorodichlorostyrene was generated by gas chromatography with a yield of 90% and a selectivity of 91%.

[0074]

[0075] Comparative Example 2

[0076] This comparative example uses FeCl3 as an inorganic metal chlorine source to prepare 4-chlorodichlorostyrene. It is the same as Example 4, except that in step (1), 1.5 mmol of FeCl2 is replaced with 1.5 mmol of FeCl3·6H2O, and 15 μL of concentrated hydrochloric acid is omitted. The rest is the same. Finally, the 4-chlorodichlorostyrene was generated by gas chromatography and the yield was 48% with a selectivity of 60%. Example 5

[0077] This example provides a method for the continuous photocatalytic synthesis of tho-dihalogenated compounds based on inorganic halide salts replacing halogen elements under photocatalyst-free conditions. Referring to Example 1, the difference is that in step (3), after separating the liquid from the inorganic halide salt after the reaction, a 20 mM styrene acetonitrile solution and 15 μL concentrated hydrochloric acid (37%) are added to the inorganic halide salt to achieve continuous production of tho-dihalogenated compounds. The rest remains the same. This system can achieve continuous production of tho-dihalogenated compounds multiple times. Gas chromatography analysis shows the yield and selectivity of styrene dichloride as follows: Figure 9 As shown, the yield and conversion rate were maintained even after five consecutive synthesis attempts, which was beyond the expectations of those skilled in the art.

[0078] Previously, our research group used metal halide salts and photoactive agents to convert hydrocarbon or nitrile compounds into halogenated compounds RX. However, without the photoactive agent, continuous synthesis could not be achieved. This invention solves this technical problem by using inorganic metal halide salts for photodriven continuous synthesis of ortho-dihalogenated compounds. After 2 hours of light irradiation in air, a yield of 85% and a selectivity of 95% for styrene dichloride can be achieved. Moreover, the yield and conversion rate can be maintained even after multiple consecutive synthesis, which is beyond the expectations of those skilled in the art. Example 6

[0079] This example provides a method for the photocatalytic synthesis of ortho-dihalogenated compounds based on inorganic halide salts replacing halogen elements under photocatalyst-free conditions. Referring to Example 1, the difference is that in step (1), 15 μL of concentrated hydrochloric acid (37%) is replaced with 30 μL of concentrated sulfuric acid (98%), while the rest is the same. Finally, the gas chromatograph test and analysis showed that the yield of styrene dichloride was 89% and the selectivity was 75%. Example 7

[0080] This example provides a method for the photocatalytic synthesis of ortho-dihalogenated compounds based on inorganic halide salts replacing halogen elements under photocatalyst-free conditions. Referring to Example 1, the difference is that in step (1), 15 μL of concentrated hydrochloric acid (37%) is replaced with 15 μL of concentrated nitric acid (98%), while the rest is the same. Finally, the gas chromatograph test and analysis showed that the yield of styrene dichloride was 19% and the selectivity was 20%. Example 8

[0081] This example provides a method for the photo-driven synthesis of ortho-dihalogenated compounds based on the substitution of halogen elements with inorganic halide salts under photocatalyst-free conditions. Referring to Example 1, the difference is that FeCl2 is replaced with CuCl2 in step (1), while the rest is the same. Finally, the gas chromatograph test and analysis showed that the yield of styrene dichloride was 43% and the selectivity was 61%. Example 9

[0082] This example provides a method for the photo-driven synthesis of ortho-dihalogenated compounds based on the substitution of halogen elements with inorganic halide salts under photocatalyst-free conditions. Referring to Example 1, the difference is that FeCl2 is replaced with CoCl2 in step (1), while the rest is the same. Finally, the gas chromatograph test and analysis showed that the yield of styrene dichloride was 30% and the selectivity was 49%. Example 10

[0083] This example provides a method for the photo-driven synthesis of ortho-dihalogenated compounds based on the substitution of halogen elements with inorganic halide salts under photocatalyst-free conditions. Referring to Example 1, the difference is that FeCl2 is replaced with NiCl2 in step (1), while the rest is the same. Finally, the gas chromatograph test and analysis showed that the yield of styrene dichloride was 25% and the selectivity was 34%.

[0084] Comparative Example 3

[0085] This comparative example is based on Example 1, except that no light was applied, so the ortho-dihalo compound could not be obtained.

[0086] Comparative Example 4

[0087] This comparative example is based on Example 1, except that no inorganic halide salts were added, so tho-dihalogenated compounds could not be obtained.

[0088] Comparative Example 5

[0089] This comparative example is similar to Example 1, except that no acid was added. Based on the one-time synthesis of the ortho-dihalogenated compound, the yield of styrene dichloride was 64% and the selectivity was 90%; however, continuous synthesis could not be achieved.

[0090] The above embodiments are only for illustrating the technical concept and features of the present invention, and are intended to enable those skilled in the art to understand the content of the present invention and implement it accordingly. They should not be construed as limiting the scope of protection of the present invention. All equivalent changes or modifications made in accordance with the spirit and essence of the present invention should be covered within the scope of protection of the present invention.

Claims

1. A method for photosynthesizing ortho-dihalogenated compounds based on non-corrosive inorganic halide salts, characterized in that, The method includes the following steps: in the presence of an acid, using metal halide salts and aromatic olefin compounds as raw materials, a photocatalytic reaction is carried out to synthesize vicinal dihalogenated compounds; the aromatic olefin compounds contain terminal alkenyl groups; the metal halide salt is one or a combination of several selected from copper chloride, nickel chloride, ferrous chloride, cobalt chloride, copper bromide, nickel bromide, ferrous bromide, and cobalt bromide; the acid is one or a combination of several selected from H2SO4, HNO3, HCl, HClO4, CF3COOH, CH3COOH, H2C2O4, and HCOOH; the method does not contain organic halogen sources or photocatalysts. The structure of the aromatic olefin compound is shown in the following formula: ； The structure of the ortho-dihalogenated compound is shown in the following formula: ； In the above chemical structural formula, R represents 1, 2, 3, 4 or 5 substituents attached to the benzene ring, and each substituent is independently any one of hydrogen, halogen, or C1-C10 alkyl; R1 and R2 are halogens.

2. A method for continuous photosynthesis of ortho-dihalogenated compounds based on non-corrosive inorganic halide salts, characterized in that, Includes the following steps: (1) In the presence of acid, a metal halide salt or an aromatic olefin compound is used as a raw material and the reaction is carried out under light irradiation; the metal halide salt is one or a combination of copper chloride, nickel chloride, ferrous chloride, cobalt chloride, copper bromide, nickel bromide, ferrous bromide, and cobalt bromide; the acid is one or a combination of H2SO4, HNO3, HCl, HClO4, CF3COOH, CH3COOH, H2C2O4, and HCOOH. (2) Then add a metal halide and react under light; (3) Repeat step (2) to synthesize the ortho-dihalogenated compound; the aromatic olefin compound contains a terminal alkenyl group; The method does not contain organic halogen sources or photocatalysts; The structure of the aromatic olefin compound is shown in the following formula: ； The structure of the ortho-dihalogenated compound is shown in the following formula: ； In the above chemical structural formula, R represents 1, 2, 3, 4 or 5 substituents attached to the benzene ring, and each substituent is independently any one of hydrogen, halogen, or C1-C10 alkyl; R1 and R2 are halogens.

3. The method according to claim 1 or 2, characterized in that, The wavelength of the light is 300–1100 nm; the temperature of the light reaction is -50℃–100℃, and the time is 1 h–24 h; the light reaction is carried out in the presence of a solvent and in air.

4. The method according to claim 3, characterized in that, The solvent includes one or more of N,N-dimethylformamide, dimethyl sulfoxide, acetonitrile, n-hexane, 1,4-dioxane, cyclohexane, and ethyl acetate.

5. The method according to claim 1 or 2, characterized in that, During the photo-induced reaction, the concentration of acid is 5–30 μL / mL, the concentration of metal halide is 50–150 mg / mL, and the concentration of aromatic olefin compound is 5–50 mM.

6. The method according to claim 1 or 2, characterized in that, Irradiation is provided by xenon lamps (0.01–100 W), LEDs (0.01–100 W), halogen lamps (0.01–100 W), or mercury lamps (0.01–100 W).

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