A pyrrolidinyl bifunctional catalyst with photosensitizer linkage, its preparation method and application

Abstract

This invention relates to a pyrrolidinyl bifunctional catalyst linked to a photosensitizer, its preparation method, and its application. The catalyst possesses a nitrogen-tetradentate chiral center and a thioxanthone photosensitizing structural unit. In the preparation method, a chiral tetradentate ligand is chemically linked to a photosensitizer, followed by complexation with a metal salt to obtain a metal complex catalyst with both a chiral catalytic center and a photocatalytic center. This catalyst is applied to the asymmetric epoxidation reaction of chalcone, developing an asymmetric epoxidation process using oxygen as the oxidant. This invention is environmentally friendly and exhibits high stereoselectivity.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of catalyst preparation, in particular to a pyrrolidinyl bifunctional catalyst linked with a photosensitizer and a preparation method thereof, and application of the catalyst to catalyze the asymmetric epoxidation of chalcone. BACKGROUND

[0002] Metalloenzymes existing in the natural world, such as cytochrome P450 enzymes, use molecular oxygen as an oxidant in maintaining human life activities. Inspired by this, researchers have developed a series of biomimetic non-hormonal metal complex catalysts by simulating the local environment of enzymes to achieve catalytic conversion of specific substrates. Such catalysts are mostly complexes formed by some chiral bidentate or polydentate nitrogen ligands and non-noble metal ions such as iron and manganese ions. Compared with traditional catalytic systems (such as salen catalysts), biomimetic non-hormonal metal catalysts have the advantage of wide substrate applicability, and under their catalysis, both functionalized olefins and non-functionalized olefins can undergo high enantioselective chiral epoxidation reactions. In addition, the iron and manganese ions used as central metal ions in such catalysts have the characteristics of wide source, non-toxic or low toxicity, and environmental friendliness compared with noble metal ions.

[0003] However, under current conditions, there are still some problems in the use of such biomimetic catalytic systems. For example, in the process of catalyzing oxidation reactions, peroxides, hypochlorite, high-valent iodine reagents, etc. are often used as oxidants. For example, Xiaohua Liu's group used high-valent iodine reagents as oxidants to achieve the enantioselective epoxidation of cyclic and acyclic trisubstituted olefins (J. Am. Chem. Soc., 2023, 145, 15611-15618.), but the oxidants used are not only expensive, but also cause environmental pollution. Therefore, from the perspectives of environmental protection and economy, molecular oxygen is the most ideal oxidant. For example, Pan Xie's group (Synlett, 2024, dio:10.1055 / a-2435-6142) used molecular oxygen as an oxidant to achieve the epoxidation of chalcone, but the epoxidation product was not stereoselective.

[0004] Therefore, it is of great significance to combine the photosensitizer with the asymmetric catalytic center through a chemical bond to obtain a non-noble metal bifunctional catalyst. SUMMARY

[0005] The purpose of this invention is to address the problem of inefficient coordination between photocatalytic centers and asymmetric catalytic centers due to excessive spatial distance, and to provide a pyrrolidinyl bifunctional catalyst linked to a photosensitizer, its preparation method, and its application. This catalyst has a nitrogen-tetradentate chiral center and a thioxanthone photosensitizing structural unit. In the preparation method, a chiral tetradentate ligand is chemically linked to a photosensitizer, followed by complexation with a metal salt to obtain a metal complex catalyst with both a chiral catalytic center and a photocatalytic center. This catalyst is applied to the asymmetric epoxidation reaction of chalcone, developing an asymmetric epoxidation process using oxygen as the oxidant. This invention is environmentally friendly and exhibits high stereoselectivity.

[0006] To achieve the above objectives, the present invention adopts the following technical solution:

[0007] A pyrrolidinyl bifunctional catalyst linked to a photosensitizer, the structural formula of which is as follows:

[0008]

[0009] Where R = methyl, methoxy, or -Cl; M = Mn or Fe; OTf = trifluoromethanesulfonate.

[0010] The preparation method of the pyrrolidinyl bifunctional catalyst with the bonded photosensitizer includes the following steps:

[0011] Step 1: Pyrrolidine diamine with a nitrogen-protecting group, 2-formaldehyde pyridine, or their derivatives are added to the first solvent and reacted at 30-90℃ for 6-20h to generate an intermediate with a Schiff base structure. After cooling to room temperature, the first reducing agent is added to the system and reacted at 0-60℃ for 4-20h. After the solvent is removed by vacuum evaporation, the solid residue is extracted, dried, and concentrated to obtain an N,N'-bis(pyridin-2-methylene)pyrrolidine-3,4-diamine derivative with a nitrogen-protecting group, namely compound 2.

[0012] The molar ratio of pyrrolidine diamine with nitrogen protecting group to 2-formaldehyde pyridine is 1:1.8-4.0; the molar ratio of pyrrolidine diamine with nitrogen protecting group to the first reducing agent is 1:2-10.

[0013] The nitrogen protecting group in the pyrrolidine diamine with a nitrogen protecting group in step one includes tert-butoxycarbonyl, benzyloxycarbonyl, p-toluenesulfonyl, methoxybenzyl or benzyl.

[0014] The first solvent is methanol, ethanol or isopropanol; the first reducing agent is sodium borohydride, sodium cyanoborohydride, sodium acetylborohydride, potassium borohydride, lithium aluminum hydride or hydrogen.

[0015] Step 2: Compound 2 is dissolved in a second solvent, and glacial acetic acid and formaldehyde aqueous solution are added to react and condense. The reaction is carried out at 15-50℃ for 2-9 hours. After the reaction is completed, a second reducing agent is added to the system for reduction for 8-20 hours. After the solvent is removed by vacuum evaporation, the solid residue is extracted, dried and concentrated to obtain N,N'-dimethyl-N,N'-bis(pyridin-2-methylene)pyrrolidine-3,4-diamine with nitrogen protecting group, i.e., compound 3.

[0016] The molar ratio of compound 2 to formaldehyde is 1:2-20, and the molar ratio of compound 2 to the second reducing agent is 1:2-10.

[0017] The second solvent used in step (two) is acetonitrile, tetrahydrofuran, methanol, ethanol, isopropanol or dichloromethane, and the second reducing agent is sodium borohydride, sodium cyanoborohydride, sodium acetylborohydride, potassium borohydride, lithium aluminum hydride or hydrogen.

[0018] Step 3: Compound 3 is dissolved in a third solvent, acid is added dropwise to the system, and the mixture is heated to reflux for 1-10 hours to remove the nitrogen protecting group. Then, it is cooled to room temperature and the solvent is removed under reduced pressure. The solid residue is extracted, dried, and concentrated to obtain an unprotected N,N'-dimethyl-N,N'-bis(pyridin-2-methylene)pyrrolidine-3,4-diamine derivative. Then, it is reacted with 3-acylchlorothiazolone in a fourth solvent at room temperature and in the presence of an acid-binding agent. After separation and purification, the tetradentate ligand of the photosensitizer is obtained, namely compound 4.

[0019] Among them, the molar ratio of compound 3 to acid is 1:0.1-4.0; the molar ratio of compound 3 to 3-acylchlorothiazolone is 1:0.6-2.0; and the molar ratio of acid binder to compound 3 is 1:2-8.

[0020] The acid in step (three) is trifluoroacetic acid, methanesulfonic acid, p-toluenesulfonic acid, hydrobromic acid, hydrochloric acid, or sulfuric acid;

[0021] The third solvent is one of dichloromethane, trichloromethane, and dichloroethane; the acid-binding agent is one of organic bases such as triethylamine, pyridine, N,N-diisopropylethylamine, and 4-dimethylaminopyridine, or inorganic bases such as sodium carbonate, potassium carbonate, and sodium acetate; and the fourth solvent is one of acetonitrile, tetrahydrofuran, methanol, ethanol, dichloromethane, and dichloroethane.

[0022] Step four: Dissolve compound four in the fifth solvent, add a metal salt suspension dropwise to it under inert gas protection, and react at 15-50°C in the dark for 4-18 hours. After the reaction is completed, recrystallize to obtain the bifunctional catalyst complex.

[0023] In this case, the molar ratio of compound four to the metal salt is 1:0.8-4;

[0024] In step four, the metal salt is one of Mn(OSO2CF3)2 or Fe(OSO2CF3)2·2CH3CN, and the fifth solvent is one of acetonitrile, tetrahydrofuran, methanol, ethanol, dichloromethane, and dichloroethane.

[0025] The application of the pyrrolidinyl bifunctional catalyst of the aforementioned photosensitizer is used to prepare optically pure epoxides in the asymmetric epoxidation reaction of chalcone and its derivatives.

[0026] The process includes the following steps: adding a catalyst, chalcone or chalcone derivative, co-catalyst, sacrificial reducing agent and solvent sequentially to a reaction tube, then replacing the tube with oxygen at 1-3 atmospheres, stirring the reaction at -50℃ to 0℃ and under visible light for 2-20 hours to obtain epoxides;

[0027] The solution consists of 10-15 mg of catalyst, 41.6 mg of chalcone or chalcone derivative, 20-40 μL of co-catalyst, and 60-100 mg of sacrificial reducing agent added to 1-4 mL of solvent.

[0028] The co-catalyst is specifically 2-ethylhexanoic acid, acetic acid, or pivalic acid;

[0029] The sacrificial reducing agent is specifically 2-ethylhexanal, acetaldehyde, or pivalanal; the solvent is acetonitrile.

[0030] The chalcone or chalcone derivatives mentioned are: 1,3-diphenyl-2-propenone, 3-phenyl-1-(m-tolyl)prop-2-en-1-one or 3-phenyl-1-(o-tolyl)prop-2-en-1-one;

[0031] The corresponding epoxy compounds are 1,3-diphenyl-2,3-epoxy-1-propanone, 3-phenyl-1-(m-tolyl)prop-2,3-epoxy-1-one or 3-phenyl-1-(o-tolyl)prop-2,3-epoxy-1-one.

[0032] The essential features of this invention are:

[0033] Currently, most biomimetic non-hormonal metal complex catalysts are complexes formed by multidentate nitrogen ligands and non-precious metals; and in the process of selecting oxidants, peroxides, hypochlorites, high-valent iodine reagents, etc. are mostly used as oxidants for oxidation reactions. These oxidants are not only expensive, but also pollute the environment.

[0034] This invention uses molecular oxygen instead of traditional oxidants and links chiral tetradentate ligands to photosensitizers through chemical bonds, followed by complexation with metal salts to obtain metal complex catalysts with chiral catalytic centers and photocatalytic centers, thereby greatly improving catalytic efficiency.

[0035] The beneficial effects of this invention are as follows:

[0036] This invention proposes and synthesizes for the first time a novel catalyst with a chiral asymmetric bonded photosensitizer. By bringing the chiral catalytic center and the photosensitizing center closer together and fixing their relative spatial positions, oxygen molecules can efficiently migrate to the asymmetric catalytic reaction center after activation of the photosensitizer unit, avoiding the quenching of active substrates that may result from long-distance migration. This catalyst was applied to the asymmetric epoxidation reaction of chalcones, utilizing green and inexpensive oxygen instead of traditional peroxides, hypochlorites, and high-valent iodine reagents as the oxidant in the epoxidation reaction. This avoids pollution and reduces reaction costs, achieving an epoxidation product yield of up to 88% and an enantiomeric excess of 75%. Detailed Implementation

[0037] The technical solutions of the present invention will be clearly and completely described below with reference to specific embodiments. It should be understood that the described embodiments are only some embodiments of the present invention, and not all embodiments. Other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative effort are all within the scope of protection of the present invention.

[0038] The reaction formula of the catalyst of the present invention is as follows:

[0039]

[0040] Synthesis of Boc-protected N,N'-bis(pyridin-2-methylene)pyrrolidine-3,4-diamine:

[0041]

[0042] As shown in the formula above, 2.8 mmol of chiral pyrrolidine diamine protected by Boc (tert-butylcarbonyl) was dissolved in 50.0 mL of methanol in a container equipped with a stirrer, heater, temperature control, and reflux device. Then, 5.6 mmol of 2-formaldehyde pyridine was added dropwise. After the addition was complete, the mixture was heated to 65 °C and refluxed for 12 h. After the reaction was complete, the mixture was cooled to room temperature, and 22.4 mmol of solid NaBH4 was slowly added in portions. Bubbles were observed during the addition. After the addition was complete, the mixture was stirred at room temperature for another 12 h. After the reaction was complete, the solvent was evaporated under reduced pressure, and 200 mL of dichloromethane was added to the residue to dissolve it. The organic phase was washed with 50 mL of saturated brine and dried over anhydrous sodium sulfate. The anhydrous sodium sulfate was then removed by filtration, and the filtrate was concentrated under vacuum to obtain compound two, namely, Boc-protected N,N'-bis(pyridin-2-methylene)pyrrolidine-3,4-diamine.

[0043] Example 2:

[0044] Synthesis of Boc-protected N,N'-dimethyl-N,N'-bis(pyridin-2-methylene)pyrrolidine-3,4-diamine:

[0045]

[0046] As shown in the formula above, 2.8 mmol of compound 2 was dissolved in 20.0 mL of acetonitrile in a container equipped with a stirrer, heater, temperature control, and reflux device. Then, 2.0 mL of glacial acetic acid and 28 mmol of 37% formaldehyde aqueous solution (containing 10.36 mmol of formaldehyde) were added sequentially. The resulting mixture was stirred at room temperature for two hours, and then 14 mmol of NaBH4 solid was slowly added. During the addition, attention should be paid to the vigorous exothermic reaction and the generation of a large number of bubbles. After the addition was complete, the mixture was stirred at room temperature for another 12 hours, and then 50.0 mL of deionized water was added to quench the reaction. The mixture was extracted three times with 50.0 mL of dichloromethane, the organic phases were combined, dried over anhydrous sodium sulfate, filtered, and the solvent was removed under vacuum. The residue was separated by silica gel column chromatography to obtain compound three, namely Boc-protected N,N'-dimethyl-N,N'-bis(pyridin-2-methylene)pyrrolidine-3,4-diamine. The eluent ratio used was v:v ethyl acetate:petroleum ether = 1:1, and 5% triethylamine was added by volume.

[0047] Example 3: Synthesis of pyrrolidinyl bifunctional catalyst ligands for photosensitizers:

[0048]

[0049] As shown in the formula above, 2.8 mmol of the methylated product was dissolved in 10.0 mL of dichloromethane in a container equipped with a stirring, heating, temperature control, and reflux device. Then, 39.2 mmol of trifluoroacetic acid was added dropwise under stirring. After the addition was complete, the reaction system was heated to 40 °C and refluxed for 5 h. The mixture was then cooled to room temperature, and the solvent was removed under vacuum. The pH of the residue was adjusted to 11 using 2N KOH aqueous solution. The resulting mixture was extracted three times with 30.0 mL of dichloromethane. The organic phases were combined, dried over anhydrous sodium sulfate, and concentrated under vacuum to obtain 2.8 mmol of crude product. The crude product was dissolved in 10 mL of dichloromethane, and then 2.8 mmol of 3-acylchlorothiazolone and 22.4 mmol of triethylamine were added. The mixture was stirred at room temperature for 24 h. After the reaction was completed, the solvent was removed under vacuum. The remaining residue was separated by silica gel column chromatography to obtain compound four, which is the pyrrolidinyl bifunctional catalyst ligand for the synthesis of photosensitizers. The eluent ratio used was v:v ethyl acetate:petroleum ether = 1:1. Triethylamine was added at a volume fraction of 5%.

[0050] Example 4: Pyrroleyl bifunctional catalyst for synthesizing iron-centered photosensitizers

[0051] 0.5 mmol of compound IV obtained in Example 3 was dissolved in 1.0 mL of anhydrous THF in a container equipped with a stirrer. Then, 0.5 mmol of anhydrous THF (1 mL) suspension of Fe(CF3SO3)2(CH3CN)2 was added dropwise to the above system under an argon atmosphere. After the addition was complete, the reaction was stirred at room temperature for 48 h. After the reaction was completed, the solvent was removed under reduced pressure. The residue was recrystallized using an acetonitrile / n-hexane system to obtain the catalyst.

[0052] Example 5: Synthesis of a pyrrolidinyl bifunctional catalyst with a manganese-centered photosensitizer

[0053] The ligand obtained in Example 3 was dissolved in 1.0 mL of anhydrous THF in a container equipped with a stirrer. Then, under an argon atmosphere, a suspension of 0.5 mmol of anhydrous THF (1 mL) in Mn(CF3SO3)2(CH3CN)2 was added dropwise to the above system. After the addition was complete, the reaction was stirred at room temperature for 48 h. After the reaction was completed, the solvent was removed under reduced pressure. The residue was recrystallized using an acetonitrile / n-hexane system to obtain the catalyst.

[0054] Example 6: Synthesis of pyrrolidinyl bifunctional ligands for photosensitizers with chlorine atom substitution

[0055] Following the steps of Examples 1-3, 2-formaldehyde pyridine in Example 1 was replaced with 4-chloropyridine-2-carboxaldehyde to obtain the target product compound seven, namely a pyrrolidinyl bifunctional ligand of a chlorine-substituted photosensitizer, the structure of which is shown below.

[0056]

[0057] Example 7: 12.5 mg of catalyst, 41.6 mg of chalcone, and 0.5 mL of anhydrous acetonitrile were added sequentially to a dry 20 mL micro-volume reaction tube. 30 μL of 2-ethylhexanoic acid was then added, replacing the acetonitrile with oxygen at 1 atmosphere. The tube was then cooled to -40 °C in a cold trap and irradiated with a xenon lamp (wavelength range 420 nm to 1000 nm) at a distance of 10 cm. 80 mg of 2-ethylhexanal was dissolved in 1.5 mL of acetonitrile, and the aldehyde solution was injected into the reaction system over 3 hours using a micro-pump. After injection, the reaction mixture was stirred for another 2 hours. After the reaction, the reaction solution was analyzed by silica gel column chromatography using ethyl acetate:petroleum ether = 1:50 as the eluent. The epoxidized product was obtained with a yield of 88% and an ee value as high as 75%.

[0058] Compound tetranuclear magnetic resonance data:

[0059] 1H NMR (400MHz, CDCl3) δ8.64 (t, J=8.9Hz, 2H), 8.56-8.48 (m, 2H), 7.71 (s, 1H) ,7.67-7.59(m,4H),7.54-7.50(m,2H),7.46(d,J=7.7Hz,1H),7.36(d,J=7. 6Hz,1H).7.18-7.12(m,2H),3.99-3.19(m,2H),3.88-3.82(m,2H),3.77-3. 73(m,2H),3.62-3.59(m,2H),3.53-3.43(m,2H).2.36(s,3H),2.27(s,3H).

[0060] 13 C NMR (101MHz, CDCl3) δ179.42,168.05,159.08,158.86,149.10,139.67,137.75,137.09,136.65,132.59,130.12,129. 93,129.16,126.65,126.08,124.95,124.50,122.85,122.20,64.52,63.24,60.98,60.82,48.77,45.48,38.25,38.20.

[0061] Compound 7 NMR data

[0062] 1 H NMR (400MHz, CDCl3), δ8.68-8.62(m,2H),8.46-8.38(m,2H),7.73(s,1H),7.71-7.59(m,2H),7.57-7.51(m,3H),7.42(s,1H),7.21-7. 16(m,2H),4.00-3.96(m,2H),3.91-3.83(m,2H),3.78-3.74,(m,2H),3.65-3.62,(m,2H),3.60-3.53(m,2H),2.40(s,3H),2.30(s,3H).

[0063] 13C NMR (101MHz, CDCl3) δ179.40,168.09,160.93,160.74,150.09,144.91,139.52,137.81,137.07,132.63,130.18,130.00,1 29.94,129.17,126.69,126.09,124.99,124.47,123.00,122.71,64.62,63.29,60.47,60.34,48.62,45.24,38.48,38.42.

[0064] 1,3-Diphenyl-2,3-epoxy-1-propanone NMR data

[0065] 1 H NMR (400MHz, CDCl3) δ8.07-8.05(m,2H),7.69-7.65(m,1H),7.56-7.52(m,2H),7.48-7.41(m,5H),4.35(d,J=1.3Hz,1H),4.13(d,J=1.3Hz,1H).

[0066] Matters not covered in this invention are common knowledge.

Claims

1. A pyrrolidinyl bifunctional catalyst linked with photosensitizer, characterized in that the structural formula of the catalyst is as follows: R = methyl, methoxy or -Cl; M = Mn or Fe. wherein Comprising the following steps:

2. The method of claim 1, wherein the method is characterized by, Step one, adding pyrrolidine diamine with nitrogen protection group, 2-formaldehyde pyridine or its derivatives into the first solvent, reacting at 30-90℃ for 6-20h to generate intermediate with Schiff base structure; after cooling to room temperature, adding the first reducing agent into the system, reacting at 0-60℃ for 4-20h, evaporating the solvent under reduced pressure, and then extracting, drying and concentrating the solid residue to obtain N,N'-bis(pyridine-2-methylene)pyrrolidine-3,4-diamine derivative with nitrogen protection group, i.e. compound two; Wherein, the molar ratio of pyrrolidine diamine with nitrogen protection group to 2-formaldehyde pyridine is 1:1.8-4.0; the molar ratio of pyrrolidine diamine with nitrogen protection group to the first reducing agent is 1:2-10; The nitrogen protection group in pyrrolidine diamine with nitrogen protection group includes tert-butyloxycarbonyl, benzyloxycarbonyl, p-toluenesulfonyl, methoxybenzyl or benzyl; The first reducing agent is sodium borohydride, sodium cyanoborohydride, sodium acetyl borohydride, potassium borohydride, lithium aluminum hydride or hydrogen; Step two, dissolving compound two in the second solvent, adding glacial acetic acid and formaldehyde aqueous solution to react and condense, reacting at 15-50℃ for 2-9h; after the reaction is completed, adding the second reducing agent into the system to reduce for 8-20h, evaporating the solvent under reduced pressure, and then extracting, drying and concentrating the solid residue to obtain N,N'-dimethyl-N,N'-bis(pyridine-2-methylene)pyrrolidine-3,4-diamine with nitrogen protection group, i.e. compound three; Wherein, the molar ratio of compound two to formaldehyde is 1:2-20, and the molar ratio of compound two to the second reducing agent is 1:2-10; The second reducing agent is sodium borohydride, sodium cyanoborohydride, sodium acetyl borohydride, potassium borohydride, lithium aluminum hydride or hydrogen; Step three, dissolving compound three in the third solvent, adding acid dropwise into the system, heating to reflux for 1-10h to remove the nitrogen protection group, then cooling to room temperature and removing the solvent under reduced pressure, and then extracting, drying and concentrating the solid residue to obtain N,N'-dimethyl-N,N'-bis(pyridine-2-methylene)pyrrolidine-3,4-diamine derivative without protection group, and then reacting with 3-acyl chlorothioxanthone in the presence of acid binding agent in the fourth solvent at room temperature to obtain the tetradentate ligand linked with photosensitizer, i.e. compound four, after separation and purification; Wherein, the molar ratio of compound three to acid is 1:0.1-4.0; the molar ratio of compound three to 3-acyl chlorothioxanthone is 1:0.6-2.0, and the molar ratio of acid binding agent to compound three is 1:2-8; The acid binding agent is an organic base or an inorganic base; Step four, dissolving compound four in the fifth solvent, adding metal salt suspension liquid dropwise into the system under the protection of inert gas, reacting at 15-50℃ for 4-18h in the dark, and then recrystallizing after the reaction is completed to obtain the bifunctional catalyst complex; Wherein, the molar ratio of compound four to metal salt is 1:0.8-4. ​ The metal salt is Mn(OSO2CF3)2 or Fe(OSO2CF3)2·2CH3CN.

3. The method for preparing the pyrrolidinyl bifunctional catalyst with a photosensitizer linked to the catalyst as described in claim 2, characterized in that, In the step one, the first solvent is methanol, ethanol or isopropanol; In the step two, the second solvent used is acetonitrile, tetrahydrofuran, methanol, ethanol, isopropanol or dichloromethane, In the step three, the third solvent is dichloromethane, trichloromethane or dichloroethane; The fourth solvent is acetonitrile, tetrahydrofuran, methanol, ethanol, dichloromethane or dichloroethane; In the step four, the fifth solvent is acetonitrile, tetrahydrofuran, methanol, ethanol, dichloromethane or dichloroethane.

4. The method for preparing the pyrrolidinyl bifunctional catalyst with a photosensitizer linked to the catalyst as described in claim 2, characterized in that, In the step three, the acid is trifluoroacetic acid, methane sulfonic acid, p-toluene sulfonic acid, hydrobromic acid, hydrochloric acid or sulfuric acid; The acid binding agent is triethylamine, pyridine, N,N-diisopropyl ethylamine, 4-dimethylamino pyridine, sodium carbonate, potassium carbonate or sodium acetate.

5. The use of a pyrrolidyl bifunctional chelating agent linked to a photosensitizer as claimed in claim 1, characterized in that, The application relates to a method for preparing an optically pure epoxide by asymmetrically epoxidizing a chalcone and derivatives thereof.

6. The use of a pyrrolidyl bifunctional catalyst linked to a photosensitizer according to claim 5, characterized in that, The method comprises the following steps: The catalyst, the chalcone or the chalcone derivative, the cocatalyst, the sacrificial reductant and the solvent are sequentially added into a reaction tube, then 1-3 atmospheres of oxygen are filled, and the reaction is stirred at -50 DEG C to 0 DEG C and under visible light for 2-20 hours to obtain the epoxide; 1-4 mL of the solvent is added to 10-15 mg of the catalyst, 41.6 mg of the chalcone or the chalcone derivative, 20-40 microliters of the cocatalyst and 60-100 mg of the sacrificial reductant; The cocatalyst is 2-ethylhexanoic acid or acetic acid or tert-pentanoic acid; The sacrificial reductant is 2-ethylhexanal or acetaldehyde or tert-pentanal; The solvent is acetonitrile; The chalcone or the chalcone derivative is 1,3-diphenyl-2-propenone, 3-phenyl-1-(m-tolyl)prop-2-en-1-one or 3-phenyl-1-(o-tolyl)prop-2-en-1-one; The corresponding obtained epoxide is 1,3-diphenyl-2,3-epoxy-1-propanone, 3-phenyl-1-(m-tolyl)prop-2,3-epoxy-1-one or 3-phenyl-1-(o-tolyl)prop-2,3-epoxy-1-one.

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