A method for photo-initiated selective bromination of electron-rich (hetero)aromatic hydrocarbons

Abstract

This invention discloses a photo-initiated selective bromination method for electron-rich (hetero)aromatic hydrocarbons, belonging to the field of pharmaceutical compound synthesis. The method provided by this invention uses a transition metal salt as the main catalyst, conducts the reaction under air conditions, and yields the brominated product under light irradiation at room temperature. This catalyst exhibits high catalytic efficiency, high yield of the bromination product, and good bromination selectivity, significantly reducing experimental costs and making it suitable for the synthesis and amplification of subsequent compounds. The method provided by this invention does not require expensive metal catalysts or oxidants, and is characterized by high efficiency, environmental friendliness, safety, and cost-effectiveness. Operation and post-processing are also simple.

Description

Technical Field

[0001] This invention relates to the field of pharmaceutical compound synthesis technology, and in particular to a method for photo-initiated selective bromination of electron-rich (hetero)aromatic hydrocarbons. Background Technology

[0002] Bromine-based organic fine chemicals are important chemical raw materials and key pharmaceutical intermediates. In the chemical industry, aromatic bromides have been widely used as key precursors in carbon-carbon and carbon-heteroatom bonding reactions. In the pharmaceutical industry, selective bromination is often used as a modification tool in medicinal chemistry, which can alter physiological properties and improve pharmacokinetic and pharmacological characteristics. Therefore, selective bromination has always been an important strategy for drug discovery and development.

[0003] Existing literature reports that the bromination of electron-rich (hetero)aromatic hydrocarbons has drawbacks such as the need for expensive metal catalysts and oxidants, high pollution and high hazard bromine sources, and complex operation. Methods for the oxidative bromination of electron-rich (hetero)aromatic hydrocarbons mainly include chemical methods, transition metal catalysis, electrochemistry, and photochemistry. Among these, chemical methods commonly use liquid bromine and NBS (N-bromosuccinimide). However, the volatility, corrosiveness, and toxicity of liquid bromine limit its widespread application. Furthermore, only 50% of the bromine atoms in liquid bromine participate in the reaction, resulting in low atom utilization and failing to meet the requirements of green chemistry development. When using NBS (N-bromosuccinimide) for bromination reactions, a free radical initiator (such as AIBN or benzoyl peroxide) is usually required to initiate the free radical chain reaction, which increases the complexity of operation and sensitivity to condition control. In addition, its high cost in industrial applications also limits its widespread use. Most importantly, none of the above-mentioned bromine sources can achieve selective bromination, easily generating dibrominated or polybrominated byproducts. Transition metal catalysis generally involves metals such as iron, palladium, gold, and platinum. Many catalysts are composed of metal complexes, which are expensive and structurally complex, or some require high-temperature heating. Electrocatalytic bromination has been reported, but issues such as poisoning and loss of noble metal electrodes and poor bromination selectivity still need to be addressed. Photocatalysis is an emerging reaction, generally using complexes of noble metals such as indium, iridium, and ruthenium. However, the application of these catalysts is often limited by their high toxicity and cost.

[0004] In recent years, many chemists have made significant contributions to the field of selective bromination reactions mentioned in this invention. However, achieving selective bromination of electron-rich (hetero)aromatics under mild conditions while meeting industrial requirements remains extremely challenging. Therefore, developing green, economical, and efficient reaction methods to achieve such selective bromination reactions is of great significance. Summary of the Invention

[0005] The purpose of this invention is to provide a photo-initiated method for the selective bromination of electron-rich (hetero)aromatic hydrocarbons. This invention addresses the problems of expensive and toxic catalysts / oxidants, hazardous bromine sources, low atom utilization, and poor selectivity inherent in existing electron-rich (hetero)aromatic hydrocarbon bromination methods. Furthermore, the method of this invention is suitable for industrial applications, with simple reaction conditions and post-processing, and low requirements for raw materials and equipment, making it suitable for large-scale industrial production. These advantages give this method broad application prospects in the field of pharmaceutical compounds.

[0006] This invention provides a method comprising the following steps:

[0007] In an air atmosphere, the electron-rich (hetero)aromatic compound shown in formula (1) was dissolved in a solvent, a catalyst and a bromine source were added, and the reaction was carried out under light at room temperature to obtain the brominated product shown in formula (2).

[0008]

[0009] In formulas (1) and (2), Ar is selected from substituted or unsubstituted electron-rich benzene rings or pyrazole rings;

[0010] When Ar is a benzene ring, 1-3 R1 substituents are attached to the benzene ring, and at least one R1 is an alkoxy group; the remaining R1s are independently selected from hydrogen, alkyl, halogen or amide groups;

[0011] When Ar is a pyrazole ring, R1 connected to the nitrogen atom at position 1 is hydrogen or alkyl, and R1 connected to the carbon atom at position 3 is hydrogen or a substituted phenyl group, wherein the substituent of the substituted phenyl group is selected from alkyl or halogen.

[0012] In formula (1), the molar ratio of the electron-rich (hetero)aromatic compound to the catalyst is 1-10:2, and the molar ratio of the catalyst to the bromine source is 1:1-4.

[0013] The beneficial effects of this application, based on the above technical solutions, are as follows:

[0014] This invention achieves significant technical effects through a transition metal salt catalysis and room temperature light irradiation in an air atmosphere:

[0015] Firstly, it exhibits excellent selectivity, avoiding dibrominated / polybrominated byproducts, thus meeting the high-precision requirements of pharmaceutical synthesis.

[0016] Secondly, the yield is high, with most products yielding over 88% and some over 98%, demonstrating outstanding reaction efficiency.

[0017] Third, it is green and environmentally friendly, requiring no precious metal catalysts or toxic oxidants. The bromine source is inexpensive and safe sodium bromide, etc., which improves atom utilization and conforms to the concept of green chemistry.

[0018] Fourth, the conditions are mild; the reaction can be carried out under room temperature and light, without the need for high temperature and high pressure, and the operation and post-processing are simple.

[0019] Fifth, the cost is controllable. The catalyst, bromine source and solvent are all cheap and readily available, reducing experimental and industrial costs and making it widely applicable. Attached Figure Description

[0020] Figure 1 It is the product prepared in Example 1 of this invention. 1 H NMR spectrum;

[0021] Figure 2 It is the product prepared in Example 2 of this invention. 1 H NMR spectrum;

[0022] Figure 3 It is the product prepared in Example 4 of this invention. 1 H NMR spectrum;

[0023] Figure 4 It is the product prepared in Example 5 of this invention. 1 H NMR spectrum;

[0024] Figure 5 It is the product prepared in Example 6 of this invention. 1 H NMR spectrum;

[0025] Figure 6 It is the product prepared in Example 7 of this invention. 1 H NMR spectrum;

[0026] Figure 7 It is the product prepared in Example 8 of this invention. 1 H NMR spectrum;

[0027] Figure 8 It is the product prepared in Example 9 of this invention. 1 H NMR spectrum;

[0028] Figure 9 It is the product prepared in Example 10 of this invention. 1 H NMR spectrum;

[0029] Figure 10 It is the product prepared in Example 11 of this invention. 1 H NMR spectrum. Detailed Implementation

[0030] Example 1

[0031]

[0032] Anisole (21.63 mg, 0.2 mmol, 1 eq), acetonitrile:water = 5:1 (8 mL), sodium bromide (41.16 mg, 0.4 mmol, 2 eq), and ferric tribromide (11.83 mg, 0.04 mmol, 0.2 eq) were added to a 25 mL quartz tube under air atmosphere and room temperature, and stirred for 24 hours under 395 nm light. After the reaction was complete, the mixture was extracted with dichloromethane and water, the organic layers were combined, dried over anhydrous sodium sulfate, and purified by vacuum distillation to give the brominated product (33.03 mg, yield 88.25%). Figure 1 As shown, 1 H NMR (400 MHz, DMSO- d 6)δ 7.45 (d, J = 9.0Hz, 2H), 6.91 (d, J = 9.0Hz, 2H), 3.75 (s, 3H). 13 CNMR (101MHz, DMSO-) d 6)δ 159.01,132.55,116.66,112.34,55.81.

[0033] Example 2

[0034]

[0035] Under air atmosphere and at room temperature, phenethyl ether (24.44 mg, 0.2 mmol, 1 eq), acetonitrile:water = 5:1 (8 mL), sodium bromide (41.16 mg, 0.4 mmol, 2 eq), and ferric tribromide (11.83 mg, 0.04 mmol, 0.2 eq) were added to a 25 mL quartz tube and stirred under 395 nm light for 36 hours. After the reaction was complete, the mixture was extracted with dichloromethane and water, the organic layers were combined, dried over anhydrous sodium sulfate, and purified by vacuum distillation to give the brominated product (35.52 mg, yield 88.36%). Figure 2 As shown, 1 H NMR (400 MHz, DMSO- d 6) δ 7.43 (d, J = 9.0 Hz, 1H), 6.89 (d, J = 9.0 Hz, 1H), 4.00 (q, J =7.0 Hz, 1H), 1.32 (t, J = 7.0 Hz, 2H). 13 C NMR (101 MHz, DMSO- d 6) δ 158.27, 132.54, 117.10, 112.18, 63.80, 14.97.

[0036] Example 3

[0037]

[0038] Under air atmosphere and at room temperature, 2-methylanisole (21.62 mg, 0.2 mmol, 1 eq), acetonitrile:water = 5:1 (8 mL), sodium bromide (41.16 mg, 0.4 mmol, 2 eq), and ferric tribromide (11.83 mg, 0.04 mmol, 0.2 eq) were added to a 25 mL quartz tube and stirred under 395 nm light for 26 hours. After the reaction was completed, the mixture was extracted with dichloromethane and water, the organic layers were combined, dried over anhydrous sodium sulfate, and purified by vacuum distillation to give the brominated product (34.26 mg, yield 92.08%). 1 H NMR (400 MHz, CDCl3) δ 3.19(s,3H),3.79(s,3H),6.67(d, J = 9.0Hz,1H),7.24-7.28(m,2H). 13 C NMR (101MHz, CDCl3) δ 157.2, 133.4, 129.6, 129.3, 112.6, 111.8, 55.5, 16.3.

[0039] Example 4

[0040]

[0041] Under air atmosphere and at room temperature, m-phenylenediamine (27.62 mg, 0.2 mmol, 1 eq), acetonitrile:water = 5:1 (8 mL), sodium bromide (41.16 mg, 0.4 mmol, 2 eq), and ferric tribromide (11.83 mg, 0.04 mmol, 0.2 eq) were added to a 25 mL quartz tube and stirred under 395 nm light for 12 hours. After the reaction was complete, the mixture was extracted with dichloromethane and water, the organic layers were combined, dried over anhydrous sodium sulfate, and purified by vacuum distillation to give the brominated product (40.74 mg, yield 94.31%). Figure 3 As shown, 1 H NMR (400 MHz, CDCl3) δ 7.32 (d, J = 8.6 Hz, 1H), 6.40 (d, J = 2.8 Hz, 1H), 6.32 (dd, J = 8.7, 2.7 Hz, 1H), 3.78 (s, 3H), 3.71 (s, 3H). 13 C NMR (101 MHz, CDCl3) δ 160.24, 156.54, 133.16, 105.88, 102.42, 99.97, 56.15, 55.58.

[0042] Example 5

[0043]

[0044] Under air atmosphere and at room temperature, 1-bromo-2,4-dimethoxybenzene (43.20 mg, 0.2 mmol, 1 eq), acetonitrile:water = 5:1 (8 mL), sodium bromide (41.16 mg, 0.4 mmol, 2 eq), and ferric tribromide (11.83 mg, 0.04 mmol, 0.2 eq) were added to a 25 mL quartz tube and stirred under 395 nm light for 24 hours. After the reaction was complete, the mixture was extracted with dichloromethane and water, the organic layers were combined, dried over anhydrous sodium sulfate, and purified by vacuum distillation to give the brominated product (56.58 mg, yield 96.25%). Figure 4 As shown, 1 HNMR (400 MHz, CDCl3) δ 7.58 (s, 1H), 6.41 (s, 1H), 3.83 (s, 6H). 13 C NMR (101MHz, CDCl3) δ 156.17, 135.90, 102.42, 97.38, 56.54.

[0045] Example 6

[0046]

[0047] Under air atmosphere and at room temperature, 1,2,3-trimethoxybenzene (33.62 mg, 0.2 mmol, 1 eq), acetonitrile:water = 5:1 (8 mL), sodium bromide (41.16 mg, 0.4 mmol, 2 eq), and ferric tribromide (11.83 mg, 0.04 mmol, 0.2 eq) were added to a 25 mL quartz tube and stirred under 395 nm light for 28 hours. After the reaction was complete, the mixture was extracted with dichloromethane and water, the organic layers were combined, dried over anhydrous sodium sulfate, and purified by vacuum distillation to give the brominated product (43.76 mg, yield 88.95%). Figure 5 As shown, 1 H NMR (400 MHz, DMSO-) d 6) δ 6.86 (s, 2H), 3.79 (s, 6H), 3.65 (s, 3H). 13 C NMR (101MHz, DMSO- d 6) δ 154.24, 137.39, 116.05, 109.36, 60.47, 56.68.

[0048] Example 7

[0049]

[0050] Acetanilide (27.02 mg, 0.2 mmol, 1 eq), acetonitrile:water = 5:1 (8 mL), sodium bromide (41.16 mg, 0.4 mmol, 2 eq), and ferric tribromide (11.83 mg, 0.04 mmol, 0.2 eq) were added to a 25 mL quartz tube under air atmosphere and room temperature, and stirred for 42 hours under 395 nm light. After the reaction was complete, the mixture was extracted with dichloromethane and water, the organic layers were combined, dried over anhydrous sodium sulfate, and purified by vacuum distillation to give the brominated product (33.64 mg, yield 78.96%). Figure 6 As shown, 1 H NMR (400MHz, DMSO-) d 6) δ10.06(s,1H),7.57(d, J = 8.9Hz,2H),7.47(d, J = 8.9Hz,2H),2.05(s,3H). 13 C NMR (101MHz, DMSO-) d 6) δ 168.92,139.15,131.92,121.33,114.95,24.48.

[0051] Example 8

[0052]

[0053] Under air atmosphere and at room temperature, 1-methylpyrazole (16.41 mg, 0.2 mmol, 1 eq), acetonitrile:water = 5:1 (8 mL), sodium bromide (41.16 mg, 0.4 mmol, 2 eq), and ferric tribromide (11.83 mg, 0.04 mmol, 0.2 eq) were added to a 25 mL quartz tube and stirred under 395 nm light for 36 hours. After the reaction was complete, the mixture was extracted with dichloromethane and water, the organic layers were combined, dried over anhydrous sodium sulfate, and purified by vacuum distillation to give the brominated product (17.17 mg, yield 53.66%). Figure 7 As shown, 1 H NMR (400 MHz, DMSO-) d 6) δ 7.92 (d, J = 0.8 Hz, 1H), 7.51 (d, J = 0.8 Hz, 1H), 3.84 (s, 3H). 13 C NMR (101 MHz, DMSO-d6) δ 139.29, 131.25, 91.84, 39.54.

[0054] Example 9

[0055]

[0056] Under air atmosphere and at room temperature, 1-phenylpyrazole (28.82 mg, 0.2 mmol, 1 eq), acetonitrile:water = 5:1 (8 mL), sodium bromide (41.16 mg, 0.4 mmol, 2 eq), and ferric tribromide (11.83 mg, 0.04 mmol, 0.2 eq) were added to a 25 mL quartz tube and stirred under 395 nm light for 24 hours. After the reaction was complete, the mixture was extracted with dichloromethane and water, the organic layers were combined, dried over anhydrous sodium sulfate, and purified by vacuum distillation to give the brominated product (43.94 mg, yield 98.96%). Figure 8 As shown, 1 H NMR (400 MHz, DMSO-) d 6) δ 13.40 (s, 1H), 7.93 (s, 1H), 7.83 (d, J = 7.1 Hz, 2H), 7.48 (t, J = 7.5 Hz, 1H)., 7.40(t, J = 7.3 Hz, 1H). 13 C NMR (101MHz, CDCl3) δ143.33,128.62,127.84,127.67,126.54,91.23.

[0057] Example 10

[0058]

[0059] Under air atmosphere and at room temperature, 1-(p-tolyl)-1H-pyrazole (31.62 mg, 0.2 mmol, 1 eq), acetonitrile:water = 5:1 (8 mL), sodium bromide (41.16 mg, 0.4 mmol, 2 eq), and ferric tribromide (11.83 mg, 0.04 mmol, 0.2 eq) were added to a 25 mL quartz tube and stirred under 395 nm light for 24 hours. After the reaction was complete, the mixture was extracted with dichloromethane and water, the organic layers were combined, dried over anhydrous sodium sulfate, and purified by vacuum distillation to give the brominated product (45.31 mg, yield 95.98%). Figure 9 As shown, 1 HNMR (400MHz, DMSO- d 6) δ 11.10(s,1H),7.55(d,J = 8.0Hz,2H),7.47(s,1H),7.17(d,J = 8.0Hz,2H),2.33(s,3H). 13 C NMR (101MHz, DMSO- d6) δ143.95,138.94,137.31,127.50,126.54,92.07,21.42.

[0060] Example 11

[0061]

[0062] Under air atmosphere and at room temperature, 1-(4-chlorophenyl)-1H-pyrazole (35.61 mg, 0.2 mmol, 1 eq), acetonitrile:water = 5:1 (8 mL), sodium bromide (41.16 mg, 0.4 mmol, 2 eq), and ferric tribromide (11.83 mg, 0.04 mmol, 0.2 eq) were added to a 25 mL quartz tube and stirred under 395 nm light for 24 hours. After the reaction was complete, the mixture was extracted with dichloromethane and water, the organic layers were combined, dried over anhydrous sodium sulfate, and purified by vacuum distillation to give the brominated product (49.98 mg, yield 97.63%). Figure 10 As shown, 1 HNMR (400 MHz, CDCl3) δ 10.82 (s, 1H), 7.61 (s, 1H), 7.58 (d, J = 4.2 Hz, 2H), 7.52 (d, J = 8.6 Hz, 2H). 13 C NMR (101 MHz, CDCl3) δ 143.46, 134.40, 130.79, 128.03, 127.78, 122.12, 91.50.

[0063] Example 12

[0064] Same as Example 4, except that the catalyst is copper sulfate and the yield of the selective bromination product is 1%.

[0065] Example 13

[0066] Same as Example 4, except that the catalyst is ferric sulfate and the yield of the selective bromination product is 32%.

[0067] Example 14

[0068] Same as Example 4, except that the catalyst was ferric nitrate and the yield of the selective bromination product was 42%.

[0069] Example 15

[0070] Same as Example 4, except that the catalyst is ferric chloride and the yield of the selective bromination product is 62%.

[0071] Example 16

[0072] Same as Example 4, except that the solvent used was an aqueous solution of acetonitrile with a volume ratio of 1:2, and the yield of the selective bromination product was 2%.

[0073] Example 17

[0074] Same as Example 4, except that the solvent used was an aqueous solution of acetonitrile with a volume ratio of 2:2, and the yield of the selective bromination product was 5%.

[0075] Example 18

[0076] Same as Example 4, except that the solvent used was an aqueous solution of acetonitrile with a volume ratio of 4:2, and the yield of the selective bromination product was 16%.

[0077] Example 19

[0078] Same as Example 4, except that the solvent used was an aqueous solution of acetonitrile with a volume ratio of 6:2, and the yield of the selective bromination product was 32%.

[0079] Example 20

[0080] Same as Example 4, except that the solvent used was an aqueous solution of acetonitrile with a volume ratio of 8:2, and the yield of the selective bromination product was 45%.

[0081] Example 21

[0082] Same as Example 4, except that the wavelength of light was 255 nm and the yield of the selective bromination product was 9%.

[0083] Example 22

[0084] Same as Example 4, except that the wavelength of light was 295 nm and the yield of the selective bromination product was 27%.

[0085] Example 23

[0086] Same as Example 4, except that the wavelength of light was 365 nm and the yield of the selective bromination product was 45%.

[0087] Example 24

[0088] Same as Example 4, except that the light wavelength is 410 nm and the yield of the selective bromination product is 65%.

[0089] Example 25

[0090] Same as Example 4, except that the wavelength of light was 455 nm and the yield of the selective bromination product was 35%.

[0091] Example 26

[0092] Same as Example 4, except that the wavelength of light was 480 nm and the yield of the selective bromination product was 22%.

[0093] Example 27

[0094] Same as Example 4, except that the molar ratio of the electron-rich (hetero)aromatic compound and the catalyst in Formula (1) is 1:2, and the yield of the selective bromination product is 86%.

[0095] Example 28

[0096] Same as Example 4, except that the molar ratio of the electron-rich (hetero)aromatic compound and the catalyst in Formula (1) is 2:2, and the yield of the selective bromination product is 98%.

[0097] Example 29

[0098] Same as Example 4, except that the molar ratio of the electron-rich (hetero)aromatic compound and the catalyst in Formula (1) is 4:2, and the yield of the selective bromination product is 92%.

[0099] Example 30

[0100] Same as Example 4, except that the molar ratio of the electron-rich (hetero)aromatic compound and the catalyst in Formula (1) is 6:2, and the yield of the selectively brominated product is 81%.

[0101] Example 31

[0102] Same as Example 4, except that the molar ratio of the electron-rich (hetero)aromatic compound and the catalyst in Formula (1) is 8:2, and the yield of the selective bromination product is 72%.

[0103] Example 32

[0104] Same as Example 4, except that potassium bromide was chosen as the bromine source and the yield of the selectively brominated product was 89%.

[0105] Example 33

[0106] Same as Example 4, except that magnesium bromide was chosen as the bromine source and the yield of the selectively brominated product was 12%.

[0107] Example 34

[0108] Same as Example 4, except that the molar ratio of the electron-rich (hetero)aromatic compound and the bromine source in Formula (1) is 1:1, and the yield of the selectively brominated product is 84%.

[0109] Example 35

[0110] Same as Example 4, except that the molar ratio of the electron-rich (hetero)aromatic compound and the bromine source in Formula (1) is 1:3, and the yield of the selectively brominated product is 95%.

[0111] Example 36

[0112] Same as Example 4, except that the molar ratio of the electron-rich (hetero)aromatic compound and the bromine source in Formula (1) is 1:4, and the yield of the selectively brominated product is 87%.

[0113] As can be seen from the above embodiments, the preparation method provided by the present invention can prepare a selective bromination product with a high yield simply by using a simple catalyst and light under an air atmosphere.

[0114] It should be understood that the specific embodiments described above are merely illustrative or explanatory of the principles of the invention and do not constitute a limitation thereof. Therefore, any modifications, equivalent substitutions, improvements, etc., made without departing from the spirit and scope of the invention should be included within the protection scope of the invention. Furthermore, the appended claims are intended to cover all variations and modifications falling within the scope and boundaries of the appended claims, or equivalent forms of such scope and boundaries.

Claims

1. A method for photo-initiated selective bromination of electron-rich (hetero)aromatic hydrocarbons, characterized in that, Includes the following steps: In an air atmosphere, the electron-rich (hetero)aromatic compound shown in formula (1) is dissolved in a solvent, a catalyst and a bromine source are added, and the reaction is carried out under light at room temperature to obtain the brominated product shown in formula (2); the catalyst is a transition metal salt selected from one of copper sulfate, ferric sulfate, ferric nitrate, ferric chloride or ferric tribromide; In formulas (1) and (2), Ar is selected from substituted or unsubstituted electron-rich benzene rings or pyrazole rings; When Ar is a benzene ring, 1-3 R1 substituents are attached to the benzene ring, and at least one R1 is an alkoxy group; the remaining R1s are independently selected from hydrogen, alkyl, halogen or amide groups; When Ar is a pyrazole ring, R1 connected to the nitrogen atom at position 1 is hydrogen or alkyl, and R1 connected to the carbon atom at position 3 is hydrogen or a substituted phenyl group, wherein the substituent of the substituted phenyl group is selected from alkyl or halogen. In formula (1), the molar ratio of the electron-rich (hetero)aromatic compound to the transition metal salt catalyst is 1-10:2, and the molar ratio of the catalyst to the bromine source is 1:1-4.

2. The method according to claim 1, characterized in that, When Ar is a benzene ring, the alkoxy group in R1 is a methoxy or ethoxy group, and the alkyl group is a methyl group.

3. The method according to claim 1, characterized in that, When Ar is a pyrazole ring, the alkyl-substituted phenyl group of R1 is a methyl-substituted phenyl group, and the halogen-substituted phenyl group is a chlorine-substituted phenyl group.

4. The method according to claim 1, characterized in that, When Ar is a benzene ring, the halogen in R1 is bromine.

5. The method according to claim 1, characterized in that, When Ar is a benzene ring, the amide group in R1 is an acetamino group.

6. The method according to any one of claims 1-5, characterized in that, The solvent is acetonitrile-water, with a volume ratio of 1-10:

2.

7. The method according to any one of claims 1-5, characterized in that, The wavelength of the photoreaction is 255-480 nm.

8. The method according to claim 1, characterized in that, The photoreaction time is 12-42 hours.

9. The method according to claim 1, characterized in that, The bromine source is selected from sodium bromide, potassium bromide, or magnesium bromide.

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