A method for synthesizing cyclic carbonates

Abstract

The present invention discloses a method for synthesizing cyclic carbonates, belonging to the technical field of organic catalysis. The present invention adopts a novel organic ion pair catalyst to realize the [3+2] cycloaddition reaction of epoxides and carbon dioxide, and obtains cyclic carbonates with high selectivity. The catalytic reaction conditions are mild (atmospheric pressure), the substrate scope is wide (including bicyclic epoxides and internal epoxides), and the obtained cyclic carbonates have no metal residues, showing great potential for commercial applications in fields such as microelectronics and polymer preparation where strict control of metal residue content is required.

Description

Technical Field

[0001] The present invention belongs to the technical field of organic catalysis, and particularly relates to a method for synthesizing five-membered cyclic carbonates and applications thereof. Background Art

[0002] Since the Industrial Revolution, the massive emission of greenhouse gases has led to serious environmental problems, such as rising global temperatures, melting polar glaciers, and frequent abnormal extreme weather. The concentration of carbon dioxide in the lower atmosphere has gradually increased from less than 268 ppm to 420 ppm. Among them, the total carbon dioxide emissions in China in 2022 were more than 34 billion tons. Since the "dual carbon" policy, chemical fixation of carbon dioxide has become a research hotspot. Carbon dioxide is a linear hetero-accumulative olefin with thermodynamic stability and kinetic inertness, with an activation energy of 395.5 kJ / mol and a very high energy barrier. Therefore, selecting high-energy substrates and designing reasonable catalysts are the keys to solving this problem. Epoxides are a large-volume chemical and thus inexpensive. Five-membered cyclic carbonates are a class of five-membered heterocyclic compounds containing oxygen elements. Cyclic carbonates are low-toxic biodegradable liquids, mainly used as aprotic polar solvents (Curr. Opin. Green Sust. Chem. 29, 2021, 100457), electrolytes in secondary batteries, intermediates in fine chemical synthesis, monomers of polycarbonate-based polymers (ACS Sustain. Chem. Eng. 4, 2016, 1032; Polym. Chem. 4, 2013, 4545), and polymerization monomers of non-isocyanate polyurethanes (NIPU). Among them, NIPU is considered to be one of the effective ways to replace traditional petroleum-based polyurethanes in the future and is directly synthesized in one step from bicyclic carbonates and diamines. Compared with polyurethanes prepared from highly toxic raw materials such as traditional phosgene and isocyanates, bio-based NIPU has biodegradability and biocompatibility, is more environmentally friendly, and conforms to the concept of sustainable development. The [3+2] cycloaddition reaction (CCE) of epoxides and CO2 is an industrially implementable strategy for chemically fixing carbon dioxide from large-volume chemicals into high-value-added products.

[0003]

[0004] In the above formula, R represents each aliphatic alkyl group, aromatic alkane, and glycidyl ether, where R 1 and R 2 can be the same group.

[0005] Currently known catalysts designed for this reaction are mainly divided into organic catalysts and metal catalysts. Metal catalysts are generally highly active and can catalyze CCE reactions under mild conditions. However, there are still some defects in metal catalysts that need to be improved, such as the high cost of rare-earth metals (ACS Sustainable Chem. Eng. 2016, 4, 4805-4814), the complex synthesis steps of many metal catalysts (Dalton Trans., 2011, 40, 3885–3902), and often require the addition of co-catalysts (ACS Catal. 2018, 8, 665-672), and metal residues limit the further high-end applications of this product. There is extensive research on organic catalysts, including quaternary ammonium salts, quaternary phosphonium salts or imidazolium salts, but these catalysts are usually not able to effectively catalyze internal epoxides (ChemSusChem 2012, 5, 2032–2038), and require harsh reaction conditions (Green Chem., 2016, 18, 4611–4615) such as high temperature, high CO2 pressure (ACS Catal. 2019, 9, 1895-1906), and anhydrous and oxygen-free (ChemSusChem 2018, 11, 4262–426). These operations increase costs and energy consumption in disguise, fundamentally leading to additional CO2 emissions, and are not suitable for industrial production applications. Summary of the invention

[0006] The object of the present invention is to provide a method for synthesizing a five-membered cyclic carbonate and its application. The catalysts on the market have poor adaptability to di- / poly-epoxides and internal epoxides, which limits the further processing and application of cyclic carbonates. The present invention adopts a brand-new organic ion pair catalyst to realize the [3+2] cycloaddition reaction of epoxides and carbon dioxide, and obtains cyclic carbonates with high selectivity. The catalytic reaction conditions are mild (normal pressure), the substrate has a wide range of application (including di-epoxides and internal epoxides), and the obtained cyclic carbonate has no metal residues, which has great potential for commercial application in fields such as microelectronics and polymer preparation where the content of metal residues is strictly controlled.

[0007] The present invention proposes for the first time that a strong Lewis acid that can be adjusted can be used as a hydrogen bond donor (HBD) and a nucleophilic halogen anion (X – ) is a bifunctional organic catalyst that catalyzes the reaction of epoxides with carbon dioxide to generate cyclic carbonates with high selectivity. The target catalyst can be obtained by simply reacting commercially available pentachlorocyclopropane with readily available secondary amines, and the post-treatment is simple and easy to operate.

[0008] The present invention discovers and solves problems from actual needs, and uses a bifunctional cyclopropenium ion pair as a hydrogen bond donor and a nucleophilic anion to catalytically synthesize epoxides with different substituents, including substrates containing bis-epoxides and internal epoxides. This organic molecular catalytic system is applied to the cycloaddition reaction of epoxides and carbon dioxide for the first time, with mild conditions and high selectivity.

[0009] The technical solution to achieve the above object is as follows:

[0010] A method for synthesizing cyclic carbonates uses a catalyst shown in Formula I to generate cyclic carbonates from an epoxide shown in Formula II and carbon dioxide:

[0011]

[0012] Wherein

[0013] X is selected from Cl, Br, I, CH3COO (OAc);

[0014] Where R 1 is selected from methyl, ethyl, butyl, cyclohexyl, isopropyl. R 2 is selected from hydrogen, methyl, methoxy, nitro, trifluoromethyl, chlorine, bromine, iodine. E is selected from O, S;

[0015] The epoxide is selected from the structure of Formula II:

[0016]

[0017] R 3 、R 4 are selected from hydrogen, a straight-chain or branched alkyl group having 1 to 4 carbon atoms, an alkenyl group having 1 to 4 carbon atoms, phenyl, a halogen or alkyl-substituted aryl group, a halogen-substituted alkyl group, R 5 -O-CH2-, and the R 5 is selected from phenyl, phenyl substituted with an alkyl group having 1 to 3 carbon atoms, allyl or a straight-chain or branched alkyl group having 1 to 4 carbon atoms, allyl glycerol ester and bisphenol A glycerol ether.

[0018] Preferably, R 1 is selected from cyclohexyl, isopropyl, R 2 is selected from hydrogen, methyl, and E is selected from S

[0019] Preferably, R 3 、R 4 are selected from hydrogen, a straight-chain or branched alkyl group having 1 to 4 carbon atoms, 1-butenyl, phenyl, a halogen or alkyl-substituted phenyl group, a chlorine or bromine-substituted alkyl group, R 5 –O–CH2–, and the R 5Selected from phenyl, phenyl substituted by alkyl with 1 to 3 carbon atoms, allyl, allyl glycerol ester and bisphenol A glycerol ether.

[0020] Preferably, the catalyst shown in Formula I is selected from the following structures:

[0021]

[0022] Preferably, the epoxide shown in Formula II is selected from phenyl glycidyl ether, m-phenyl glycidyl ether, styrene oxide, 1,1,1-trifluoro-2,3-epoxypropane, epichlorohydrin, 1,2-epoxy-5-hexene, allyl glycidyl ether, methyl glycidyl ether, methyl acrylate glycidyl ether, tert-butyl glycidyl ether, cyclohexene oxide, 2,3-diphenyloxirane.

[0023] The structures of the epoxides are shown in the following table:

[0024]

[0025] The catalyst shown in Formula I is selected from the following structures:

[0026]

[0027] The epoxide shown in Formula II is selected from the following structures:

[0028]

[0029] Preferably, the reaction temperature of the method for synthesizing cyclic carbonate is 25 - 120 °C, the reaction time is 6 hours to 48 hours, the carbon dioxide pressure is 0.1 to 1 Mpa, and the molar ratio of the catalyst shown in Formula I to the epoxide shown in Formula II is 10:1 to 100:1.

[0030] Preferably, the reaction temperature of the preparation method is 100 °C, the reaction time is 6 hours, the pressure of carbon dioxide is 0.1 Mpa, and the molar ratio of the catalyst shown in Formula I to the epoxide shown in Formula II is 100:1.

[0031] Preferably, the specific steps of the method include:

[0032] (1) Add the catalyst shown in Formula I and the epoxide shown in Formula II to the reaction vessel at a molar ratio of 100:1;

[0033] (2) Charge 0.1 Mpa of carbon dioxide, and place the reaction vessel in a preheated heating reactor;

[0034] (3) React for 6 - 12 hours, cool, add n-hexane to wash the reaction solution to obtain cyclic carbonate.

[0035] Beneficial effects

[0036] (1) Through the above-mentioned catalytic system, the present invention can efficiently synthesize cyclic carbonates with high added value. Compared with the cyclic carbonates synthesized using metal catalysts in the prior art, it has the characteristics of high selectivity, no metal residue, mild conditions, etc., and has a wide range of substrate practicability, and is still applicable to bis / multi-epoxy substrates. It has great potential for commercial applications in the fields of biomedicine, polymer preparation, etc.

[0037] (2) The catalytic system of the present invention uses a strong Lewis acid as a hydrogen bond donor (HBD) and a halide ion (X – ) to bifunctionally catalyze the [3+2] cycloaddition of epoxides and carbon dioxide to synthesize cyclic carbonates. The Lewis acid, as a hydrogen bond donor, activates the epoxide and stabilizes the ionic intermediate. X – Due to the repulsive interaction with the cyclopropenyl cation, its nucleophilicity is enhanced, and it attacks the epoxide to open the ring.

[0038] (3) The present invention can catalyze the CCE reaction under normal pressure and low catalyst loading conditions, with a short reaction time and low temperature, and can obtain cyclic carbonates with extremely high reaction selectivity. Compared with the synthesis of cyclic carbonates under other conditions such as high temperature, high pressure, long reaction time, and high catalyst loading, the reaction conditions of the present invention are very mild. In summary, the present invention has obvious advantages such as mildness, high efficiency, easy preparation, and no metal residue compared with other existing catalytic systems. BRIEF DESCRIPTION OF THE DRAWINGS

[0039] The embodiments of the present invention will be described in detail in conjunction with the accompanying drawings, where

[0040] Figure 1 1H NMR spectrum (400 MHz, chloroform-d) of the product corresponding to epoxide A

[0041] Figure 2 13C NMR spectrum (101 MHz, chloroform-d) of the product corresponding to epoxide A

[0042] Figure 3 1H NMR spectrum (400 MHz, chloroform-d) of the product corresponding to epoxide B

[0043] Figure 4 13C NMR spectrum (101 MHz, chloroform-d) of the product corresponding to epoxide B

[0044] Figure 5 1H NMR spectrum (400 MHz, chloroform-d) of the product corresponding to epoxide C

[0045] Figure 613C NMR spectrum (101 MHz, chloroform-d) of the product corresponding to Epoxide C

[0046] Figure 7 1H NMR spectrum (400 MHz, chloroform-d) of the product corresponding to Epoxide D

[0047] Figure 8 13C NMR spectrum (101 MHz, chloroform-d) of the product corresponding to Epoxide D

[0048] Figure 9 1H NMR spectrum (400 MHz, chloroform-d) of the product corresponding to Epoxide E

[0049] Figure 10 13C NMR spectrum (101 MHz, chloroform-d) of the product corresponding to Epoxide E

[0050] Figure 11 1H NMR spectrum (400 MHz, chloroform-d) of the product corresponding to Epoxide F

[0051] Figure 12 13C NMR spectrum (101 MHz, chloroform-d) of the product corresponding to Epoxide F

[0052] Figure 13 1H NMR spectrum (400 MHz, chloroform-d) of the product corresponding to Epoxide G

[0053] Figure 14 13C NMR spectrum (101 MHz, chloroform-d) of the product corresponding to Epoxide G

[0054] Figure 15 1H NMR spectrum (400 MHz, chloroform-d) of the product corresponding to Epoxide H

[0055] Figure 16 13C NMR spectrum (101 MHz, chloroform-d) of the product corresponding to Epoxide H

[0056] Figure 17 1H NMR spectrum (400 MHz, chloroform-d) of the product corresponding to Epoxide I

[0057] Figure 18 13C NMR spectrum (101 MHz, chloroform-d) of the product corresponding to Epoxide I

[0058] Figure 191H NMR Spectrum of the Product Corresponding to Epoxide J (400 MHz, chloroform-d)

[0059] Figure 20 13C NMR Spectrum of the Product Corresponding to Epoxide J (101 MHz, chloroform-d)

[0060] Figure 21 1H NMR Spectrum of the Product Corresponding to Epoxide K (400 MHz, chloroform-d)

[0061] Figure 22 13C NMR Spectrum of the Product Corresponding to Epoxide K (101 MHz, chloroform-d)

[0062] Figure 23 1H NMR Spectrum of the Product Corresponding to Epoxide L (400 MHz, chloroform-d)

[0063] Figure 24 13C NMR Spectrum of the Product Corresponding to Epoxide L (101 MHz, chloroform-d)

[0064] Figures 25 - 26 1H NMR and 13C NMR Spectra of the Catalyst in Example 1

[0065] Figures 27 - 28 1H NMR and 13C NMR Spectra of the Catalyst in Example 2

[0066] Figures 29 - 30 1H NMR and 13C NMR Spectra of the Catalyst in Example 3

[0067] Figure 31 1H NMR Spectrum of the Non-Isocyanate Polyurethane in Example 17 Detailed Description of the Invention

[0068] The present invention can be further illustrated by the following examples, which are for illustrative purposes only and not intended to limit the invention. Any ordinary person skilled in the art can understand that these examples do not limit the invention in any way and can make appropriate modifications and data transformations without departing from the essence and scope of the invention.

[0069] The 1H NMR and 13C NMR spectra involved in the examples were measured using a Bruker Ascend TM-400 nuclear magnetic resonance analyzer from Bruker Corporation. The deuterated reagents used were deuterated chloroform (CDCl3) and deuterated dimethyl sulfoxide (DMSO-d6).

[0070] The raw materials used in the following examples were all purchased from Sigma-Aldrich Chemical Technology (Shanghai) Co., Ltd.

[0071] The structure of the catalyst system used in the examples is as follows:

[0072]

[0073] The structure of the epoxide used in the examples is as follows:

[0074]

[0075] Example 1:

[0076] Perform standard Schlenk operation on the reaction flask to remove water and oxygen in the reaction system. Add catalyst 1 (2.6 mg, 0.005 mmol, 0.001 equiv) under the condition of passing inert gas. Then add epoxide A (5 mmol, 1.0 equiv) and charge carbon dioxide (0.1 Mpa). React the reactor on a heating stirrer at a stirring rate of 400 revolutions per minute at 100 °C for 6 hours. After the reaction is completed, take out the reaction tube and let it cool naturally. Add 30 equivalents of n-hexane and wash three times to obtain a colorless oily substance. Dry it to constant weight. The conversion rate reaches 32% and the selectivity is 99%. The hydrogen spectrum of the product is as shown in Figure 1 shown, and the carbon spectrum of the product is as shown in Figure 2 shown. The spectral data are: δ7.49–7.40(m,3H),7.40–7.28(m,2H),5.67(t,J = 8.0Hz,1H),4.79(t,J = 8.4Hz,1H),4.33(dd,J = 8.7,7.8Hz,1H).

[0077] The preparation method of catalyst 1 is as follows: Dropwise add pentachlorocyclopropane (1 equiv) to a dichloromethane solution of diisopropylamine (6 equiv) under an ice bath. React at room temperature for 12 hours, and bubble ammonia through under an ice bath for 1 hour. Filter and concentrate to dryness. Wash the solid with 3M NaOH to obtain an off-white solid. Add phenyl isothiocyanate (2 equiv) and react for 1 hour. Wash the reaction solution with 3M HCl and then dry to obtain catalyst 1. The hydrogen spectrum of the product is as shown in Figure 25 shown, and the carbon spectrum of the product is as shown in Figure 26 shown. The spectral data are: 1 δ12.02(s,1H),11.76(s,1H),7.85(d,J = 7.9Hz,2H),7.33(t,J = 7.6Hz,2H),7.15(t,J = 7.4Hz,1H),4.13(hept,J = 6.8Hz,4H),1.40(d,J = 6.8Hz,24H).

[0078] Example 2:

[0079] Perform standard Schlenk operation on the reaction flask to remove water and oxygen from the reaction system. Under the condition of passing inert gas, add catalyst 1 (26 mg, 0.05 mmol, 0.01 equiv). Then add epoxide A (5 mmol, 1.0 equiv) and charge carbon dioxide (0.1 Mpa). React the reactor at 120 °C for 6 hours on a heating stirrer with a stirring rate of 400 revolutions per minute. After the reaction is completed, take out the reaction tube and let it cool naturally. Wash it three times with 30 equivalents of n-hexane to obtain a colorless oily substance, dry it to a constant weight. The conversion rate reaches 54%, and the selectivity is 99%.

[0080] Example 3:

[0081] Perform standard Schlenk operation on the reaction flask to remove water and oxygen from the reaction system. Under the condition of passing inert gas, add catalyst 2 (28 mg, 0.05 mmol, 0.01 equiv). Then add epoxide A (5 mmol, 1.0 equiv) and charge carbon dioxide (0.1 Mpa). React the reactor at 120 °C for 6 hours on a heating stirrer with a stirring rate of 400 revolutions per minute. After the reaction is completed, take out the reaction tube and let it cool naturally. Wash it three times with 30 equivalents of n-hexane to obtain a colorless oily substance, dry it to a constant weight. The conversion rate reaches 68%, and the selectivity is 99%.

[0082] The preparation method of catalyst 2 is as follows: Add 5 mL of HBr (48% aqueous solution, w / w) to the dichloromethane solution of catalyst 1. After reacting for 24 hours, concentrate and dry to obtain catalyst 2. The 1H NMR spectrum of the product is as Figure 27 shown, and the 13C NMR spectrum of the product is as Figure 28 shown. The spectral data are: δ 10.84–10.60 (m, 2H), 7.80 (d, J = 7.9 Hz, 2H), 7.34 (t, J = 7.7 Hz, 2H), 7.17 (t, J = 7.4 Hz, 1H), 4.13–4.08 (m, 4H), 1.39 (d, J = 6.4 Hz, 24H).

[0083] Example 4:

[0084] Perform standard Schlenk operation on the reaction flask to remove water and oxygen from the reaction system. Under the condition of passing inert gas, add catalyst 3 (30 mg, 0.05 mmol, 0.01 equiv). Then add epoxide A (5 mmol, 1.0 equiv) and charge carbon dioxide (0.1 Mpa). React the reactor at 100 °C for 6 hours on a heating stirrer with a stirring rate of 400 revolutions per minute. After the reaction is completed, take out the reaction tube and let it cool naturally. Wash it three times with 30 equivalents of n-hexane to obtain a colorless oily substance, dry it to a constant weight. The conversion rate reaches 99%, and the selectivity is 99%.

[0085] The preparation method of catalyst 3 is as follows: Sodium iodide (1.2 equivalents) is added to the acetone solution of catalyst 1, and after stirring for 2 hours, the solid is filtered. Then 1.2 equivalents of sodium iodide are added to the solution and stirring is continued for 30 minutes. After filtration, the solution is concentrated, dissolved in dichloromethane, and the solid is filtered again. The filtrate is concentrated and dried to obtain catalyst 3. The hydrogen NMR spectrum of the product is as shown in Figure 29 shown, and the carbon NMR spectrum of the product is as shown in Figure 30 shown. The spectral data are: δ11.03 (s, 1H), 10.63 (s, 1H), 7.88 (d, J = 7.9 Hz, 2H), 7.34 (t, J = 7.7 Hz, 2H), 7.17 (t, J = 7.4 Hz, 1H), 4.10 (hept, J = 6.8 Hz, 4H), 1.41 (d, J = 6.8 Hz, 24H).

[0086] Example 5:

[0087] Perform standard Schlenk operation on the reaction flask to remove water and oxygen from the reaction system. Under an inert gas atmosphere, catalyst 3 (30 mg, 0.05 mmol, 0.01 equiv) is added. Then epoxide A (5 mmol, 1.0 equiv) is added and carbon dioxide (0.1 Mpa) is introduced. The reactor is reacted at 25 °C for 48 hours on a heating stirrer with a stirring rate of 400 rpm. After the reaction is completed, the reaction tube is taken out and allowed to cool naturally, washed three times with 30 equivalents of n-hexane to obtain a colorless oil, dried to a constant weight, with a conversion rate of 62% and a selectivity of 99%.

[0088] Example 6:

[0089] Perform standard Schlenk operation on the reaction flask to remove water and oxygen from the reaction system. Under an inert gas atmosphere, catalyst 3 (30 mg, 0.05 mmol, 0.01 equiv) is added. Then epoxide B (5 mmol, 1.0 equiv) is added and carbon dioxide (0.1 Mpa) is introduced. The reactor is reacted at 100 °C for 6 hours on a heating stirrer with a stirring rate of 400 rpm. After the reaction is completed, the reaction tube is taken out and allowed to cool naturally, washed three times with 30 equivalents of n-hexane to obtain a colorless oil, dried to a constant weight, with a conversion rate of 96% and a selectivity of 99%. The hydrogen NMR spectrum of the product is as shown in Figure 3 shown, and the carbon NMR spectrum of the product is as shown in Figure 4 shown. The spectral data are: δ4.98 (dq, J = 9.3, 4.9, 4.5 Hz, 1H), 4.58 (td, J = 8.6, 1.4 Hz, 1H), 4.43–4.35 (m, 1H), 3.79 (ddd, J = 12.3, 5.3, 1.4 Hz, 1H), 3.71 (ddd, J = 12.2, 3.7, 1.2 Hz, 1H).

[0090] Embodiment 7:

[0091] The reaction flask was subjected to a standard Schlenk operation to remove water and oxygen from the reaction system. Catalyst 3 (30 mg, 0.05 mmol, 0.01 equiv) was added under inert gas. Epoxide C (5 mmol, 1.0 equiv) was then added and carbon dioxide (0.1 MPa) was introduced. The reactor was reacted at 100°C for 6 hours on a heated stirrer with a stirring rate of 400 rpm. After the reaction was completed, the reaction tube was taken out and allowed to cool naturally. 30 equivalents of n-hexane were added for washing three times to obtain a colorless oil, which was dried to constant weight. The conversion rate reached 98% and the selectivity was 99%. The hydrogen spectrum of the product is shown in Figure 5 The carbon spectrum of the product is shown in Figure 6 The spectrum data are: δ4.97 (dq, J = 8.2, 5.3 Hz, 1H), 4.62 (dd, J = 8.9, 8.2 Hz, 1H), 4.37 (dd, J = 8.9, 5.9 Hz, 1H), 3.60 (d, J = 5.2 Hz, 2H).

[0092] Embodiment 8:

[0093] The reaction flask was subjected to a standard Schlenk operation to remove water and oxygen from the reaction system. Catalyst 3 (30 mg, 0.05 mmol, 0.01 equiv) was added under inert gas. Epoxide D (5 mmol, 1.0 equiv) was then added and carbon dioxide (0.1 MPa) was introduced. The reactor was reacted at 100°C for 6 hours on a heated stirrer with a stirring rate of 400 rpm. After the reaction was completed, the reaction tube was taken out and allowed to cool naturally. 30 equivalents of n-hexane were added for washing three times to obtain a colorless oil, which was dried to constant weight. The conversion rate reached 97% and the selectivity was 99%. The hydrogen spectrum of the product is shown in Figure 7 The carbon spectrum of the product is shown in Figure 8 The spectral data are: δ5.89–5.73 (m, 1H), 5.24–5.12 (m, 2H), 4.83–4.73 (m, 1H), 4.45 (t, J = 8.4 Hz, 1H), 4.36–4.28 (m, 1H), 4.05–3.92 (m, 2H), 3.64 (dd, J = 11.2, 3.4 Hz, 1H), 3.54 (dd, J = 11.2, 3.7 Hz, 1H).

[0094] Embodiment 9:

[0095] Perform standard Schlenk operation on the reaction flask to remove water and oxygen from the reaction system. Add catalyst 3 (30 mg, 0.05 mmol, 0.01 equiv) under an inert gas atmosphere. Then add epoxide E (5 mmol, 1.0 equiv) and charge carbon dioxide (0.1 Mpa). React the reactor at 100 °C for 12 hours on a heating stirrer with a stirring rate of 400 revolutions per minute. After the reaction is completed, take out the reaction tube and let it cool naturally. Wash it three times with 30 equivalents of n-hexane to obtain a colorless oil. Dry it to constant weight. The conversion rate reaches 99% and the selectivity is 99%. The 1H NMR spectrum of the product is as shown in Figure 9 shown, and the 13C NMR spectrum of the product is as shown in Figure 10 shown. The spectral data are: δ 4.69 (qd, J = 7.5, 5.4 Hz, 1H), 4.55–4.47 (m, 1H), 4.05 (dd, J = 8.4, 7.2 Hz, 1H), 1.78 (dddd, J = 14.0, 10.2, 7.5, 4.8 Hz, 1H), 1.72–1.62 (m, 1H), 1.47–1.27 (m, 4H), 0.99–0.81 (m, 3H).

[0096] Example 10:

[0097] Perform standard Schlenk operation on the reaction flask to remove water and oxygen from the reaction system. Add catalyst 3 (30 mg, 0.05 mmol, 0.01 equiv) under an inert gas atmosphere. Then add epoxide F (5 mmol, 1.0 equiv) and charge carbon dioxide (0.1 Mpa). React the reactor at 100 °C for 6 hours on a heating stirrer with a stirring rate of 400 revolutions per minute. After the reaction is completed, take out the reaction tube and let it cool naturally. Wash it three times with 30 equivalents of n-hexane to obtain a colorless oil. Dry it to constant weight. The conversion rate reaches 84% and the selectivity is 99%. The 1H NMR spectrum of the product is as shown in Figure 11 shown, and the 13C NMR spectrum of the product is as shown in Figure 12 shown. The spectral data are: δ 7.16 (ddd, J = 7.3, 4.1, 2.7 Hz, 2H), 6.93 (td, J = 7.4, 1.0 Hz, 1H), 6.81–6.75 (m, 1H), 5.05 (ddt, J = 8.6, 5.5, 3.3 Hz, 1H), 4.67–4.54 (m, 2H), 4.26 (dd, J = 10.6, 3.6 Hz, 1H), 4.13 (dd, J = 10.6, 3.1 Hz, 1H), 2.22 (s, 3H).

[0098] Example 11:

[0099] Perform standard Schlenk operation on the reaction flask to remove water and oxygen from the reaction system. Under the condition of passing inert gas, add catalyst 3 (30 mg, 0.05 mmol, 0.01 equiv). Then add epoxide G (5 mmol, 1.0 equiv) and charge carbon dioxide (0.1 Mpa). React the reactor at 100 °C for 6 hours on a heating stirrer with a stirring rate of 400 revolutions per minute. After the reaction is completed, take out the reaction tube and let it cool naturally. Wash it three times with 30 equivalents of n-hexane to obtain a colorless oily substance, dry it to a constant weight. The conversion rate reaches 87% and the selectivity is 99%. The 1H NMR spectrum of the product is as shown in Figure 13 shown, and the 13C NMR spectrum of the product is as shown in Figure 14 shown. The spectral data are: δ 7.38–7.26 (m, 2H), 7.05–6.97 (m, 1H), 6.94–6.87 (m, 2H), 5.07–4.97 (m, 1H), 4.60 (t, J = 8.5 Hz, 1H), 4.52 (dd, J = 8.5, 5.9 Hz, 1H), 4.23 (dd, J = 10.6, 4.0 Hz, 1H), 4.13 (dd, J = 10.7, 3.6 Hz, 1H).

[0100] Example 12:

[0101] Perform standard Schlenk operation on the reaction flask to remove water and oxygen from the reaction system. Under the condition of passing inert gas, add catalyst 3 (30 mg, 0.05 mmol, 0.01 equiv). Then add epoxide H (5 mmol, 1.0 equiv) and charge carbon dioxide (0.1 Mpa). React the reactor at 100 °C for 6 hours on a heating stirrer with a stirring rate of 400 revolutions per minute. After the reaction is completed, take out the reaction tube and let it cool naturally. Wash it three times with 30 equivalents of n-hexane to obtain a colorless oily substance, dry it to a constant weight. The conversion rate reaches 87% and the selectivity is 99%. The 1H NMR spectrum of the product is as shown in Figure 15 shown, and the 13C NMR spectrum of the product is as shown in Figure 16 shown. The spectral data are: δ 4.79 (ddt, J = 8.4, 6.0, 3.7 Hz, 1H), 4.47 (t, J = 8.4 Hz, 1H), 4.35 (dd, J = 8.3, 6.0 Hz, 1H), 3.62 (dd, J = 11.1, 3.6 Hz, 1H), 3.53 (dd, J = 11.1, 3.8 Hz, 1H), 3.39 (s, 3H).

[0102] Example 13:

[0103] Perform standard Schlenk operation on the reaction flask to remove water and oxygen from the reaction system. Add catalyst 3 (30 mg, 0.05 mmol, 0.01 equiv) under an inert gas atmosphere. Then add epoxide I (5 mmol, 1.0 equiv) and charge carbon dioxide (0.1 Mpa). React the reactor at 100 °C for 6 hours on a heating stirrer with a stirring rate of 400 revolutions per minute. After the reaction is completed, take out the reaction tube and let it cool naturally. Wash it three times with 30 equivalents of n-hexane to obtain a colorless oily substance, dry it to constant weight, with a conversion rate of 94% and a selectivity of 99%. The 1H NMR spectrum of the product is as shown in Figure 17 shown, and the 13C NMR spectrum of the product is as shown in Figure 18 shown. The spectral data are: δ 4.81–4.71 (m, 1H), 4.47 (t, J = 8.2 Hz, 1H), 4.38 (dd, J = 8.3, 5.8 Hz, 1H), 3.61 (dd, J = 10.3, 4.6 Hz, 1H), 3.57–3.51 (m, 1H), 1.19 (s, 9H).

[0104] Example 14:

[0105] Perform standard Schlenk operation on the reaction flask to remove water and oxygen from the reaction system. Add catalyst 3 (30 mg, 0.05 mmol, 0.01 equiv) under an inert gas atmosphere. Then add epoxide J (5 mmol, 1.0 equiv) and charge carbon dioxide (0.1 Mpa). React the reactor at 100 °C for 6 hours on a heating stirrer with a stirring rate of 400 revolutions per minute. After the reaction is completed, take out the reaction tube and let it cool naturally. Wash it three times with 30 equivalents of n-hexane to obtain a colorless oily substance, dry it to constant weight, with a conversion rate of 88% and a selectivity of 99%. The 1H NMR spectrum of the product is as shown in Figure 19 shown, and the 13C NMR spectrum of the product is as shown in Figure 20 shown. The spectral data are: δ 6.14 (t, J = 1.1 Hz, 1H), 5.64 (p, J = 1.5 Hz, 1H), 4.97 (ddt, J = 8.7, 5.6, 3.4 Hz, 1H), 4.58 (t, J = 8.6 Hz, 1H), 4.42 (dd, J = 12.6, 3.1 Hz, 1H), 4.36–4.28 (m, 1H), 1.94 (t, J = 1.2 Hz, 3H).

[0106] Example 15:

[0107] Perform standard Schlenk operation on the reaction flask to remove water and oxygen from the reaction system. Under an inert gas atmosphere, add catalyst 3 (30 mg, 0.05 mmol, 0.01 equiv). Then add epoxide K (5 mmol, 1.0 equiv) and charge carbon dioxide (0.1 Mpa). React the reactor on a heating stirrer with a stirring rate of 400 rpm at 100 °C for 6 hours. After the reaction is completed, take out the reaction tube and let it cool naturally. Add 30 equivalents of n-hexane and wash three times to obtain a colorless oily substance. Dry it to a constant weight. The conversion rate reaches 92% and the selectivity is 99%. The 1H NMR spectrum of the product is as shown in Figure 21 shown, and the 13C NMR spectrum of the product is as shown in Figure 22 shown. The spectral data are: δ 7.18–7.10 (m, 4H), 6.85–6.76 (m, 4H), 5.01 (ddt, J = 8.1, 5.9, 3.9 Hz, 2H), 4.60 (t, J = 8.4 Hz, 2H), 4.52 (dd, J = 8.5, 5.9 Hz, 2H), 4.21 (dd, J = 10.6, 4.3 Hz, 2H), 4.12 (dd, J = 10.6, 3.5 Hz, 2H), 1.63 (s, 6H).

[0108] Example 16:

[0109] Perform standard Schlenk operation on the reaction flask to remove water and oxygen from the reaction system. Under an inert gas atmosphere, add catalyst 3 (30 mg, 0.05 mmol, 0.01 equiv). Then add epoxide L (5 mmol, 1.0 equiv) and charge carbon dioxide (0.1 Mpa). React the reactor on a heating stirrer with a stirring rate of 400 rpm at 100 °C for 48 hours. After the reaction is completed, take out the reaction tube and let it cool naturally. Add 30 equivalents of n-hexane and wash three times to obtain a colorless oily substance. Dry it to a constant weight. The conversion rate reaches 92% and the selectivity is 99%. The 1H NMR spectrum of the product is as shown in Figure 23 shown, and the 13C NMR spectrum of the product is as shown in Figure 24 shown. The spectral data are: δ 4.65 (t, J = 4.1 Hz, 1H), 1.83 (dq, J = 10.0, 4.9 Hz, 2H), 1.54 (tt, J = 8.1, 4.4 Hz, 1H), 1.38 (qd, J = 8.7, 7.9, 4.5 Hz, 1H).

[0110] Example 17:

[0111] Perform standard Schlenk operation on the reaction flask to remove water and oxygen from the reaction system. Under the condition of passing inert gas, add the product bisphenol A cyclic carbonate of epoxide L (3 mmol, 1 equiv), and add 1 mL of solvent DMF to dissolve. Then add 1,6-hexanediamine (3 mmol, 1.0 equiv) and catalyst tetrabutylammonium bromide (0.03 mmol, 0.01 equiv). React the reactor at 100 °C for 24 hours on a stirrer with a stirring rate of 400 revolutions per minute. After the reaction is completed, take out the reaction tube and let it cool naturally, wash it with water to obtain a white solid, and the conversion rate reaches 99%. The 1H NMR spectrum of the product is as shown in Figure 31 shown (1H NMR, 400 MHz, CDCl3).

Claims

1. A method for synthesizing cyclic carbonates, characterized in that: Using the catalyst shown in Formula I, cyclic carbonates are formed from the epoxide shown in Formula II and carbon dioxide: Wherein X is selected from Cl, Br, I, CH3COO (OAc); wherein R 1 is selected from methyl, ethyl, butyl, isopropyl, and R 2 is selected from hydrogen, and E is selected from S; The epoxide described is selected from the structure of Formula II: R 3 and R 4 are selected from hydrogen, a straight-chain or branched alkyl group having 1 to 4 carbon atoms, an alkenyl group having 1 to 4 carbon atoms, a phenyl group, a halogen-substituted aryl group, R 5 –O–CH2–, and the R 5 is selected from a phenyl group, a phenyl group substituted with an alkyl group having 1 to 3 carbon atoms, an allyl group, or a straight-chain or branched alkyl group having 1 to 4 carbon atoms, allyl glycerol ester, and bisphenol A glycerol ether.

2. The method according to claim 1, wherein where R 1 is selected from isopropyl, R 2 is selected from hydrogen, and E is selected from S.

3. The method according to claim 1, wherein R 3 and R 4 are selected from hydrogen, a linear or branched alkyl group having 1 to 4 carbon atoms, 1-butenyl, phenyl, halogen-substituted phenyl, R 5 –O–CH2–, and the said R 5 is selected from phenyl, phenyl substituted with an alkyl group having 1 to 3 carbon atoms, allyl, allyl glycerol ester, and bisphenol A glycerol ether.

4. The method according to claim 1, wherein The catalyst shown in Formula I is selected from the following structures:

5. The method according to claim 1, wherein The epoxide shown in Formula II is selected from the following structures:

6. The method according to claim 5, characterized in that, The catalyst shown in Formula I described is selected from the following structures: The epoxide shown in Formula II is selected from the following structures:

7. The method according to claim 1, characterized in that, The reaction temperature of the method for synthesizing cyclic carbonates is 25 to 120 °C, the reaction time is 6 hours to 48 hours, the carbon dioxide pressure is 0.1 to 1 Mpa, and the molar ratio of the catalyst shown in Formula I to the epoxide shown in Formula II is 10:1 to 100:

1.

8. The method according to claim 7, wherein The reaction temperature of the method for synthesizing cyclic carbonates is 100 °C, the reaction time is 6 hours, the pressure of carbon dioxide is 0.1 Mpa, and the molar ratio of the catalyst shown in Formula I to the epoxide shown in Formula II is 100:

1.

9. The method according to claim 1, wherein The specific steps of the method described include: (1) Adding the catalyst shown in Formula I and the epoxide shown in Formula II to the reaction vessel in a molar ratio of 100:1; (2) Charging 0.1 Mpa of carbon dioxide and placing the reaction vessel in a pre-heated heating reactor; (3) Reacting for 6 to 12 hours, cooling, adding n-hexane to wash the reaction solution, and obtaining cyclic carbonates.

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