A kind of synthetic method of cyclic carbonate

Abstract

The invention discloses a method for synthesizing a cyclic carbonate, belongs to the technical field of organic catalysis, and provides a class of halogen-free catalysts for catalyzing a cyclization reaction with carbon dioxide and an epoxide. The cyclic carbonate synthesized by the method has a high conversion rate and no metal residue, mild reaction conditions, and the catalyst is easy to prepare and has wide applicability.

Description

Technical Field

[0001] The invention belongs to the technical field of organic catalysis, and particularly relates to a method for producing five-membered cyclic carbonate by utilizing cycloaddition reaction of epoxide and carbon dioxide. Background Art

[0002] Carbon dioxide is an abundant and cheap resource, and large-scale emissions of carbon dioxide cause great damage to the environment. Therefore, how to efficiently utilize carbon dioxide is a problem that people are very concerned about. CO2 can be transformed into multiple fields. CO2 can be used to synthesize various chemical products such as fertilizers, fuels, medicines, and plastics. Among them, the cycloaddition reaction of epoxides and CO2 to generate cyclic carbonates is an effective way to transform CO2.

[0003] The product generated by the cycloaddition reaction of epoxy compounds and carbon dioxide, namely five-membered cyclic carbonate, has attracted widespread attention due to its excellent physical and chemical properties such as high solubility, high boiling point, biodegradability and low toxicity. It is widely used in lithium battery electrolytes, printing and dyeing, textile and other industries.

[0004] As for catalyzing this reaction, although the reactivity of carbon dioxide is poor, some metal complex catalysts and organic catalysts have been developed. Although metal catalysts are low-priced and have high catalytic activity, they inevitably have the problem of metal residues. Organic catalysts are widely used in CCE reactions due to their excellent catalytic activity and thermodynamic stability. Among them, the bifunctional catalytic mode of hydrogen bond donor (HBD) coordinated with halide anion (X-) has been widely recognized, but halide anions are corrosive to general metal containers, and their own toxicity and non-green nature have made us interested in studying halogen-free catalytic systems. Summary of the invention

[0005] The object of the present invention is to provide a halogen-free catalyst for catalyzing the cyclization reaction with carbon dioxide and epoxy compounds. The method can accurately prepare five-membered cyclic carbonate.

[0006] A method for synthesizing a five-membered cyclic carbonate ester using a halogen-free catalyst, wherein epoxide and carbon dioxide are used as substrates, and under the catalysis of DMAP and a phenolic substituent, a five-membered cyclic carbonate ester is obtained. The halogen-free catalyst shown in formula (I) is used, and carbon dioxide is introduced into the epoxide and carbon dioxide in the absence of a solvent to obtain a cyclic carbonate ester.

[0007]

[0008] wherein R1 and R5 are selected from the same group, and R1 and R5 are selected from hydrogen, fluorine, and chlorine;

[0009] R2 and R4 are selected from the same group, and R2 and R4 are selected from hydrogen or fluorine;

[0010] R3 is selected from hydrogen, nitro, fluorine or methylsulfonyl;

[0011] R6 is selected from dimethylamino and pyrrolyl;

[0012] The structure of the epoxide is shown in formula (II):

[0013]

[0014] The R7 and R8 are selected from hydrogen, straight-chain alkyl, halogen-substituted alkyl, phenyl, substituted phenyl, the substitution in the "substituted phenyl" is selected from halogen or straight-chain or branched alkyl containing 1-5 carbon atoms, or R9-O-CH2-, the R9 is selected from phenyl, phenyl substituted by alkyl containing 1-3 carbon atoms, allyl or branched or straight-chain alkyl containing 1-4 carbon atoms, and the R7 and R8 have the same or different structures.

[0015] Preferably, when R1 and R4 are selected from the same group, R1 and R4 are selected from fluorine and chlorine, R2, R3 and R5 are selected from hydrogen, and R6 is selected from dimethylamino and pyrrolyl;

[0016] When R1 and R5 are selected from the same group, R1 and R5 are selected from fluorine and chlorine, R2, R3 and R4 are selected from hydrogen, and R6 is selected from dimethylamino and pyrrolyl;

[0017] When R4 and R5 are selected from the same group, R4 and R5 are selected from fluorine and chlorine, R1, R2 and R3 are selected from hydrogen, and R6 is selected from dimethylamino and pyrrolyl;

[0018] When R1, R2, and R3 are selected from the same group, R1, R2, and R3 are selected from fluorine and chlorine, R4 and R5 are selected from hydrogen, and R6 is selected from dimethylamino and pyrrolyl;

[0019] When R1, R2, and R5 are selected from the same group, R1, R2, and R5 are selected from fluorine and chlorine, R3 and R4 are selected from hydrogen, and R6 is selected from dimethylamino and pyrrolyl;

[0020] When R1, R2, R3, R4 are selected from the same group, R1, R2, R3, R4 are selected from fluorine and chlorine, R5 is selected from hydrogen, and R6 is selected from dimethylamino and pyrrolyl;

[0021] When R1, R2, R3, R4, R5 are selected from the same group, R1, R2, R3, R4, R5 are selected from fluorine and chlorine, R6 is selected from dimethylamino and pyrrolyl;

[0022] When R3 is selected from hydrogen, nitro, methylsulfonyl, chlorine or fluorine, R1, R2, R4, R5 are selected from hydrogen, and R6 is selected from dimethylamino and pyrrolyl;

[0023] The R7 and R8 are selected from hydrogen, n-butyl, halogen-substituted alkyl, phenyl, R9-O-CH2-, the R9 is selected from phenyl, phenyl substituted by alkyl of 1 to 3 carbon atoms, halogen-substituted phenyl, allyl or branched or straight-chain alkyl of 1 to 4 carbon atoms, and the R7 and R8 have the same or different structures.

[0024] More preferably, the halogen-free catalyst described in formula (I) is selected from the structure:

[0025]

[0026] Preferably, the epoxide represented by formula (II) is selected from epichlorohydrin, epibromohydrin, allyl glycidyl ether, tert-butyl glycidyl ether, benzyl glycidyl ether, 4-chlorobenzene glycidyl ether, dibromobenzene glycidyl ether, phenyl glycidyl ether, 2-toluene glycidyl ether, styrene oxide, (methoxymethyl)ethylene oxide, 2,2-bis-(4-glycolylaminophenyl)propane, and butylethylene oxide.

[0027] Preferably, the molar ratio of the epoxide represented by formula (II) to the halogen-free catalyst represented by formula (I) is 100:2.5, the reaction temperature is 60-120° C., and the reaction time is 1-24 h.

[0028] The preferred method for synthesizing a five-membered cyclic carbonate by fixing carbon dioxide is as follows: a halogen-free catalyst represented by formula (I) is added to a stainless steel reaction tube, carbon dioxide is then introduced into the reactor, and then the reactor is ventilated three times, and heated to 60-120° C. in a carbon dioxide atmosphere, and the reaction time is 1-24 hours.

[0029] Preferably, the reaction solution is cooled, subjected to column chromatography, and then spin-dried to obtain the product.

[0030] The present invention proposes to use a halogen-free catalyst to catalyze the cycloaddition reaction of epoxide and carbon dioxide. The preparation method of the catalyst is simple, that is, DMAP and a phenolic substituent are reacted in a tetrahydrofuran solvent at 40° C. for four hours to obtain the catalyst, the steps are simple, the yield is close to 100%, and no further purification is required.

[0031] Starting from practical application, the present invention further develops a halogen-free catalyst for DMAP and phenolic substituents based on the experience of the group's previous design of a halogen-free pyridine saccharinate catalyst for catalyzing the CCE of epoxides and carbon dioxide. The catalyst has a high conversion rate for epoxides and is simple and easy to synthesize.

[0032] Beneficial effects:

[0033] (1) The present invention can efficiently synthesize five-membered cyclic carbonates through the above-mentioned catalytic system. Compared with the method using metal catalysts or metal complex catalysts in the prior art, it has the characteristics of high yield, no metal residue, wide application, etc. It has great potential for commercial application in the fields of biomedicine and medicine.

[0034] (2) The catalytic system of the present invention can catalyze the cyclization reaction of epoxy compounds and carbon dioxide. Currently, there are only a few reports of halogen-free catalysts catalyzing the [3+2] cyclization reaction. Most of the reported catalysts have a large catalytic load. When the load is increased to 10 mol%, the reaction time is long. In the present invention, the catalyst load is reduced to 2.5 mol%, and the reaction time is shortened to 12 hours. The catalyst has wide applicability and good catalytic effect.

[0035] (3) The catalytic system used in the present invention is easy to prepare, has high catalytic efficiency, high conversion rate, and is highly efficient.

[0036] In summary, compared with other existing catalytic systems, the present invention has obvious advantages such as mildness, high efficiency, easy preparation, and no metal. BRIEF DESCRIPTION OF THE DRAWINGS

[0037] The embodiments of the present invention are described in detail below with reference to the accompanying drawings, wherein

[0038] Figure 1-16 : Hydrogen-carbon spectrum of the product catalyst 1-5 obtained in Example 1-8

[0039] Figure 17-26 : Hydrogen spectra of the cyclic carbonate products obtained in Examples 9-18 DETAILED DESCRIPTION

[0040] The present invention can be further described by the following examples, which are intended to illustrate but not to limit the present invention. Any person skilled in the art will appreciate that these examples do not limit the present invention in any way and that appropriate modifications and data conversions may be made thereto without violating the spirit of the invention and departing from the scope of the present invention.

[0041] The structure of the catalytic system used in the examples is as follows:

[0042]

[0043] Embodiment 1:

[0044] A 50 mL reaction bottle was fully dried and filled with inert gas. p-Nitrophenol (1.39 g, 10 mmol, 1.0 equiv.) was added, and 10 mL of methyl tert-butyl ether was added to dissolve it, followed by 4-dimethylaminopyridine (1.22 g, 10 mmol, 1.0 equiv.), with obvious solid precipitation. Stirring was continued at room temperature for 1 hour, and after removing the solvent under reduced pressure, the mixture was placed in a vacuum drying oven and dried for 2 hours to obtain catalyst (1) as a light yellow powder with a yield of 98%. 1 H NMR (400MHz, DMSO-d6) δ8.14–8.07(m,4H),6.92–6.86(m,2H),6.63–6.58(m,2H),2.96(s,6H). 13 C NMR (101MHz, DMSO-d6) δ165.38,154.58,149.20,139.46,126.73,116.43,107.18,39.99,39.12. Figure 1 is the hydrogen spectrum of this embodiment, Figure 2 It is the carbon spectrum of this example.

[0045] Embodiment 2:

[0046] A 50 mL reaction bottle was fully dried and filled with inert gas. 4-Methylsulfonylphenol (0.86 g, 5 mmol, 1.0 equiv.) was added, and 8 mL of tetrahydrofuran was added to dissolve it, followed by 4-dimethylaminopyridine (0.61 g, 5 mmol, 1.0 equiv.). After stirring at 40°C for 4 hours, the reaction solution was completely cooled, and the solvent was removed by drying under reduced pressure, and then placed in a vacuum drying oven for 2 hours to obtain catalyst (2) as a white powder with a yield of 99%. 1 H NMR (400MHz, DMSO-d6) δ8.11–8.07(m,2H),7.74–7.70(m,2H),6.96–6.92(m,2H),6.59–6.56(m,2H),3.10(s,3H),2.94(s,6H). 13 CNMR(101MHz,DMSO-d6)δ162.59,154.45,149.66,131.15,129.81,116.22,107.18,39.98,39.07. Figure 3 is the hydrogen spectrum of this embodiment, Figure 4 It is the carbon spectrum of this example.

[0047] Embodiment 3:

[0048] A 50 mL reaction bottle was fully dried and filled with inert gas. 2,6-difluorophenol (0.8 g, 6.15 mmol, 1.0 equiv.) was added, and 10 mL of tetrahydrofuran was added to dissolve it, followed by 4-dimethylaminopyridine (0.91 g, 6.15 mmol, 1.0 equiv.). After stirring at 40°C for 4 hours, the reaction solution was completely cooled, the solvent was removed by decompression, and then placed in a vacuum drying oven for 2 hours to obtain catalyst (3) with a yield of 99% and a white powder. 1H NMR (400 MHz, DMSO-d6) δ8.09 (d, J = 5.8 Hz, 2H), 7.33 (d, J = 8.0 Hz, 2H), 6.81 (t, J = 8.0 Hz, 1H), 6.59 (d, J = 6.2 Hz, 2H), 2.94 (s, 6H). 13 C NMR(101MHz,DMSO-d6)δ154.51,151.94,151.87,149.49,134.79,134.63,134.47,118 .49,118.41,118.32,112.43,112.38,112.31,112.23,112.16,112.11,107.18,39.08. Figure 5 is the hydrogen spectrum of this embodiment, Figure 6 It is the carbon spectrum of this example.

[0049] Embodiment 4:

[0050] A 50 mL reaction bottle was fully dried and filled with inert gas. 2,3,4-trifluorophenol (0.74 g, 5 mmol, 1.0 equiv.) was added, and 10 mL of tetrahydrofuran was added to dissolve it, followed by 4-dimethylaminopyridine (0.61 g, 5 mmol, 1.0 equiv.), and stirred at 40°C for 4 hours. After the reaction liquid was completely cooled, the solvent was removed by decompression, and then placed in a vacuum drying oven for 2 hours to obtain catalyst (4) with a yield of 99% as a white powder. 1 H NMR (400MHz, DMSO-d6) δ8.13–8.05(m,2H),6.66–6.52(m,4H),2.94(s,6H). 13 C NMR(101MHz,DMSO-d6)δ154.01,153.93,153.90,153.80,151.91,151.85,151.80,151.74,149.48,14 9.42,149.38,149.32,149.15,149.13,133.64,131.28,106.72,100.11,100.06,99.94,99.89,38.60. Figure 7is the hydrogen spectrum of this embodiment, Figure 8 It is the carbon spectrum of this example.

[0051] Embodiment 5:

[0052] A 50 mL reaction bottle was fully dried and filled with inert gas. 2,3,4,5-tetrafluorophenol (0.83 g, 5 mmol, 1.0 equiv.) was added, and 10 mL of tetrahydrofuran was added to dissolve it, followed by 4-dimethylaminopyridine (0.61 g, 5 mmol, 1.0 equiv.), and stirred at 40°C for 4 hours. After the reaction liquid was completely cooled, the solvent was removed by decompression, and then placed in a vacuum drying oven for 2 hours to obtain catalyst (5) with a yield of 99% and a white powder. 1 H NMR (400MHz, DMSO-d6) δ8.17–8.11(m,2H),6.79–6.74(m,2H),6.63(tt,J=11.0,7.0Hz,1H),3.05(s,6H). 13 C NMR (101MHz, DMSO-d6) δ155.43,147.43,145.05,144.90,144.24,143.34,140.45,106.83,89.39,89.15,88.91,39.05. Fig. 9 is the hydrogen spectrum of this embodiment, Fig.10 It is the carbon spectrum of this example.

[0053] Embodiment 6:

[0054] A 50 mL reaction bottle was fully dried and filled with inert gas. 2,3,4,5,6-pentafluorophenol (1.84 g, 10 mmol, 1.0 equiv.) was added, and 10 mL of tetrahydrofuran was added to dissolve it, followed by 4-dimethylaminopyridine (1.22 g, 10 mmol, 1.0 equiv.), and stirred at 40°C for 6 hours. After the reaction liquid was completely cooled, the solvent was removed by decompression, and then placed in a vacuum drying oven for 2 hours to obtain catalyst (6) with a yield of 99% and a white powder. 1 H NMR (400MHz, Chloroform-d) δ12.92–12.85 (m, 2H), 11.51–11.44 (m, 2H), 7.78 (s, 6H), 7.26 (q, J = 1.9Hz, 1H). 13 C NMR (101MHz, DMSO-d6) δ146.99,107.24,39.98,39.32. Fig.11 is the hydrogen spectrum of this embodiment, Fig.12 It is the carbon spectrum of this example.

[0055] Embodiment 7:

[0056] A 50 mL reaction bottle was fully dried and filled with inert gas. 2,6-dichlorophenol (0.65 g, 5 mmol, 1.0 equiv.) was added, and 6 mL of tetrahydrofuran was added to dissolve it, followed by 4-dimethylaminopyridine (0.61 g, 5 mmol, 1.0 equiv.), and stirred at 40°C for 4 hours. After the reaction liquid was completely cooled, the solvent was removed by decompression, and then placed in a vacuum drying oven for 2 hours to obtain catalyst (7) with a yield of 99% and a white powder. 1 H NMR (400MHz, DMSO-d6) δ8.09(d,J=5.8Hz,2H),7.33(d,J=8.0Hz,2H),6.81(t,J=8.0Hz,1H),6.59(d,J=6.2Hz,2H),2.94(s,6H). 13 C NMR (101MHz, DMSO-d6) δ154.65,150.78,148.92,128.97,123.02,120.15,107.18,39.98,39.12. Fig.13 is the hydrogen spectrum of this embodiment, Fig.14 It is the carbon spectrum of this example.

[0057] Embodiment 8:

[0058] A 50 mL reaction bottle was fully dried and filled with inert gas, 2,6-dichlorophenol (0.81 g, 5 mmol, 1.0 equiv.) was added, and 10 mL of tetrahydrofuran was added to dissolve it, followed by 4-pyrrolidinylpyridine (0.74 g, 5 mmol, 1.0 equiv.) was added, and stirred at 40°C for 4 hours. After the reaction solution was completely cooled, the solvent was removed by reduced pressure, and the solution was placed in a vacuum drying oven and dried for 2 hours to obtain catalyst (8) with a yield of 99% as a white powder. 1 H NMR (400MHz, DMSO-d6) δ8.14–8.03(m,2H),7.33(d,J=8.1Hz,2H),6.80(t,J=8.0Hz,1H),6.50–6.38(m,2H),3.32–3.19(m,4H),2.01–1.88(m,4H). 13 C NMR (101 MHz, DMSO-d6) 13 C NMR (101MHz, DMSO-d6) δ151.85,150.26,149.07,129.04,122.90,120.60,107.48,47.14,39.98,25.28. Fig.15 is the hydrogen spectrum of this embodiment, Fig.16 It is the carbon spectrum of this example.

[0059] The epoxy substrate structure used in the examples is as follows:

[0060] Structure and numbering

[0061]

[0062] Embodiment 9:

[0063] Epoxide (1) (10 mmol) and catalyst 3 (0.025 mmol) were added to an autoclave equipped with mechanical stirring and temperature control heating. The autoclave was sealed, and the air in the autoclave was replaced with CO2 three times. Then, CO2 was charged into the autoclave to an initial pressure of 1 MPa, and the temperature was raised to 100°C. The reaction time was 12 h. After the reaction was completed, the autoclave was cooled to 0°C with an ice-water mixture to release the residual gas, and a conversion rate of 88% and a selectivity of 94% were obtained. Fig.17 It is the hydrogen spectrum of this example.

[0064] Embodiment 10:

[0065] Epoxide (2) (10 mmol) and catalyst 2 (0.05 mmol) were added to an autoclave equipped with mechanical stirring and temperature control heating. The autoclave was sealed, and the air in the autoclave was replaced with CO2 three times. Then, CO2 was charged into the autoclave to an initial pressure of 1 MPa, and the temperature was raised to 100°C. The reaction time was 12 h. After the reaction was completed, the autoclave was cooled to 0°C with an ice-water mixture to release the residual gas, and a conversion rate of 99% and a selectivity of 99% were obtained. Fig.18 It is the hydrogen spectrum of this example.

[0066] Embodiment 11:

[0067] Epoxide (3) (10 mmol) and catalyst 1 (0.05 mmol) were added to an autoclave equipped with mechanical stirring and temperature control heating. The autoclave was sealed, and the air in the autoclave was replaced with CO2 three times. Then, CO2 was charged into the autoclave to an initial pressure of 1 MPa, and the temperature was raised to 100°C. The reaction time was 12 h. After the reaction was completed, the autoclave was cooled to 0°C with an ice-water mixture to release the residual gas, and a conversion rate of 91% and a selectivity of 91% were obtained. Fig.19 It is the hydrogen spectrum of this example.

[0068] Embodiment 12:

[0069] Epoxide (4) (10 mmol) and catalyst 5 (0.025 mmol) were added to an autoclave equipped with mechanical stirring and temperature control heating. The autoclave was sealed, and the air in the autoclave was replaced with CO2 three times. Then, CO2 was charged into the autoclave to an initial pressure of 1 MPa, and the temperature was raised to 100°C. The reaction time was 12 h. After the reaction was completed, the autoclave was cooled to 0°C with an ice-water mixture to release the residual gas, and a conversion rate of 86% and a selectivity of 98% were obtained. Fig. 20 It is the hydrogen spectrum of this example.

[0070] Embodiment 13:

[0071] Epoxide (5) (10 mmol) and catalyst 4 (0.05 mmol) were added to an autoclave equipped with mechanical stirring and temperature control heating. The autoclave was sealed, and the air in the autoclave was replaced with CO2 three times. Then, CO2 was charged into the autoclave to an initial pressure of 1 MPa, and the temperature was raised to 120°C. The reaction time was 12 h. After the reaction was completed, the autoclave was cooled to 0°C with an ice-water mixture to release the residual gas, and a conversion rate of 80% and a selectivity of 92% were obtained. Fig.21 It is the hydrogen spectrum of this example.

[0072] Embodiment 14:

[0073] Epoxide (6) (10 mmol) and catalyst 4 (0.05 mmol) were added to an autoclave equipped with mechanical stirring and temperature control heating. The autoclave was sealed, and the air in the autoclave was replaced with CO2 three times. Then, CO2 was charged into the autoclave to an initial pressure of 1 MPa, and the temperature was raised to 120°C. The reaction time was 12 h. After the reaction was completed, the autoclave was cooled to 0°C with an ice-water mixture to release the residual gas, and a conversion rate of 75% and a selectivity of 75% were obtained. Fig. 22 It is the hydrogen spectrum of this example.

[0074] Embodiment 15:

[0075] Epoxide (7) (10 mmol) and catalyst 6 (0.05 mmol) were added to an autoclave equipped with mechanical stirring and temperature control heating. The autoclave was sealed, and the air in the autoclave was replaced with CO2 three times. Then, CO2 was charged into the autoclave to an initial pressure of 1 MPa, and the temperature was raised to 120°C. The reaction time was 12 h. After the reaction was completed, the autoclave was cooled to 0°C with an ice-water mixture to release the residual gas, and a conversion rate of 98% and a selectivity of 99% were obtained. Fig.23 It is the hydrogen spectrum of this example.

[0076] Embodiment 16:

[0077] Epoxide (8) (10 mmol) and catalyst 7 (0.025 mmol) were added to an autoclave equipped with mechanical stirring and temperature control heating. The autoclave was sealed, and the air in the autoclave was replaced with CO2 three times. Then, CO2 was charged into the autoclave to an initial pressure of 1 MPa, and the temperature was raised to 120°C. The reaction time was 12 h. After the reaction was completed, the autoclave was cooled to 0°C with an ice-water mixture to release the residual gas, and a conversion rate of 83% and a selectivity of 84% were obtained. Fig.24 It is the hydrogen spectrum of this example.

[0078] Embodiment 17:

[0079] Epoxide (9) (10 mmol) and catalyst 8 (0.05 mmol) were added to an autoclave equipped with mechanical stirring and temperature control heating. The autoclave was sealed, and the air in the autoclave was replaced with CO2 three times. Then, CO2 was charged into the autoclave to an initial pressure of 2 MPa, and the temperature was raised to 100°C. The reaction time was 48 h. After the reaction was completed, the autoclave was cooled to 0°C with an ice-water mixture to release the residual gas, and a conversion rate of 97% and a selectivity of 99% were obtained. Fig.25 It is the hydrogen spectrum of this example.

[0080] Embodiment 18:

[0081] Epoxide (10) (10 mmol) and catalyst 8 (0.025 mmol) were added to an autoclave equipped with mechanical stirring and temperature control heating. The autoclave was sealed, and the air in the autoclave was replaced with CO2 three times. Then, CO2 was charged into the autoclave to an initial pressure of 1 MPa, and the temperature was raised to 100°C. The reaction time was 12 h. After the reaction was completed, the autoclave was cooled to 0°C with an ice-water mixture to release the residual gas, and a conversion rate of 73% and a selectivity of 73% were obtained. Fig.26 It is the hydrogen spectrum of this example.

Claims

1. A method for synthesizing a cyclic carbonate, characterized in that: Using the halogen-free catalyst shown in formula (I), epoxide and carbon dioxide are reacted in the absence of solvent, and carbon dioxide is introduced to obtain a cyclic carbonate. wherein R1 and R5 are selected from the same group, and R1 and R5 are selected from hydrogen, fluorine, and chlorine; R2 and R4 are selected from the same group, and R2 and R4 are selected from hydrogen or fluorine; R3 is selected from hydrogen, nitro, fluorine or methylsulfonyl; R6 is selected from dimethylamino and pyrrolyl; The structure of the epoxide is shown in formula (II): The R7 and R8 are selected from hydrogen, straight-chain alkyl, halogen-substituted alkyl, phenyl, substituted phenyl, the substitution in the "substituted phenyl" is selected from halogen or straight-chain or branched alkyl containing 1 to 5 carbon atoms, or R9-O-CH2-, the R9 is selected from phenyl, phenyl substituted by alkyl containing 1 to 3 carbon atoms, allyl or branched or straight-chain alkyl containing 1 to 4 carbon atoms, and the R7 and R8 are the same or different structures.

2. The synthesis method according to claim 1, characterized in that: When R1 and R4 are selected from the same group, R1 and R4 are selected from fluorine and chlorine, R2, R3 and R5 are selected from hydrogen, and R6 is selected from dimethylamino and pyrrolyl; When R1 and R5 are selected from the same group, R1 and R5 are selected from fluorine and chlorine, R2, R3 and R4 are selected from hydrogen, and R6 is selected from dimethylamino and pyrrolyl; When R4 and R5 are selected from the same group, R4 and R5 are selected from fluorine and chlorine, R1, R2 and R3 are selected from hydrogen, and R6 is selected from dimethylamino and pyrrolyl; When R1, R2, and R3 are selected from the same group, R1, R2, and R3 are selected from fluorine and chlorine, R4 and R5 are selected from hydrogen, and R6 is selected from dimethylamino and pyrrolyl; When R1, R2, and R5 are selected from the same group, R1, R2, and R5 are selected from fluorine and chlorine, R3 and R4 are selected from hydrogen, and R6 is selected from dimethylamino and pyrrolyl; When R1, R2, R3, R4 are selected from the same group, R1, R2, R3, R4 are selected from fluorine and chlorine, R5 is selected from hydrogen, and R6 is selected from dimethylamino and pyrrolyl; When R1, R2, R3, R4, R5 are selected from the same group, R1, R2, R3, R4, R5 are selected from fluorine and chlorine, R6 is selected from dimethylamino and pyrrolyl; When R3 is selected from hydrogen, nitro, methylsulfonyl, chlorine or fluorine, R1, R2, R4, R5 are selected from hydrogen, and R6 is selected from dimethylamino and pyrrolyl; The R7 and R8 are selected from hydrogen, n-butyl, halogen-substituted alkyl, phenyl, R9-O-CH2-, the R9 is selected from phenyl, phenyl substituted by alkyl of 1 to 3 carbon atoms, phenyl substituted by halogen, allyl or branched or straight-chain alkyl of 1 to 4 carbon atoms, and the R7 and R8 have the same or different structures.

3. The synthesis method according to claim 1, characterized in that: The halogen-free catalyst described in formula (I) is selected from the structure: Structure and numbering 4. The synthesis method according to claim 1, characterized in that The epoxide represented by formula (II) is selected from epichlorohydrin, epibromohydrin, allyl glycidyl ether, tert-butyl glycidyl ether, benzyl glycidyl ether, 4-chlorobenzene glycidyl ether, dibromobenzene glycidyl ether, phenyl glycidyl ether, 2-toluene glycidyl ether, styrene oxide, (methoxymethyl)ethylene oxide, 2,2-bis-(4-glycolylaminophenyl)propane, and butylethylene oxide.

5. The synthesis method according to claim 1, characterized in that: The molar ratio of the epoxide represented by formula (II) to the halogen-free catalyst represented by formula (I) is 100:2.5, the reaction temperature is 60-120° C., and the reaction time is 1-24 hours.

6. The synthesis method according to claim 1, characterized in that: The method for synthesizing a five-membered cyclic carbonate by fixing carbon dioxide is as follows: a halogen-free catalyst represented by formula (I) is added into a stainless steel reaction tube, carbon dioxide is then charged into the reactor, and then the reactor is ventilated three times, and heated to 60-120° C. in a carbon dioxide atmosphere, and the reaction time is 1-24 hours.

7. The synthesis method according to claim 1, characterized in that: The reaction solution is cooled, column chromatographed, and then spin-dried to obtain the product.

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