A method for preparing a cyclic carbonate

Abstract

The present invention discloses a preparation method of cyclic carbonates, belonging to the technical field of organic catalysis. A binary ionic catalyst formed by β-diketone and an organic strong base is adopted. The binary β-diketone anion and organic strong base cation catalyst prepared by the present invention can efficiently catalyze epoxides, and the obtained carbonate has a high yield. The catalytic process is simple to operate and has a good catalytic effect on most epoxides. The catalyst of the present invention has the advantages of being metal-free, halogen-free, cheap and easily available, having good chemical stability, high catalytic efficiency, etc. The reaction can be completed within 12 h, and the one-pot method is adopted, which is simple to operate and has wide industrial application value.

Description

Technical Field

[0001] The present invention belongs to the technical field of organic catalysis, and particularly relates to a method for preparing cyclic carbonates. Background Art

[0002] In recent years, cyclic carbonates have been widely used to synthesize polyurethanes. Cyclic carbonates can also be used as aprotic polar solvents and electrolytes for electrolyte batteries. Synthesizing cyclic carbonates from epoxides and CO2 can capture CO2 while converting it into value-added products, providing an alternative C1 resource for chemical industry synthesis. Therefore, this route has great industrial application value.

[0003] There are many types of catalysts for cycloaddition reactions, such as quaternary ammonium salts, alkali metal halides, organophosphonium salts, ionic liquids, transition metal complexes, metal oxides, molecular sieves, supported metal halides, supported metal complexes, etc. Many of these metal catalysts have poor selectivity, are prone to hydrolysis or oxidation, and cause pollution, while most halogen catalysts corrode equipment, and most organic catalysts require high temperatures (>100 °C) and pressures (>10 atm). (Org. Chem. Front. 8 (2021) 613–627. Green Sustainable Chem. 24 (2020) 72–81. Deng Youquan et al., CN1343668; Yang Caihong et al., CN1424147; Lv Xiaobing et al., CN1189246). Therefore, developing a green, efficient, and inexpensive catalyst for cycloaddition reactions is an important research direction. Summary of the Invention

[0004] Aiming at the deficiencies of the prior art, the purpose of the present invention is to provide a catalyst that can efficiently catalyze the reaction of epoxides and CO2 to synthesize cyclic carbonates and their derivatives. The raw material of the catalyst used in this method is an inexpensive and easily available acetylacetone, and the catalyst can be obtained through a simple one-step reaction. The cyclic carbonate can be obtained through one-step reaction, without the need for harsh reaction conditions such as high temperature, high pressure, anhydrous, and anaerobic conditions, without solvents, and without metal residues. Even when the catalyst loading is low (catalyst: raw material ≤ 5 mol%), a yield of 90% or more can be obtained. Moreover, the catalyst used in this method is metal-free, halogen-free, economical, has good chemical stability, and higher catalytic efficiency. The obtained cyclic carbonates have great application potential in the fields of food packaging, biomedicine, and microelectronics.

[0005] To achieve the above purpose, the present invention specifically adopts the following technical solutions:

[0006] The present invention synthesizes a β-diketone catalyst with a simple structure, and uses a strong base to remove the proton on the alcohol hydroxyl group after tautomerization to obtain a β-diketone anion catalyst, which can effectively catalyze the synthesis of cyclic carbonates from epoxides and carbon dioxide.

[0007] The β-diketone anion catalyst shown in formula (I) catalyzes the cycloaddition reaction of epoxides and carbon dioxide to obtain cyclic carbonates

[0008]

[0009] wherein R 1 is a linear or branched alkyl group or hydrogen having 1 to 4 carbon atoms, and R 2 , R 3 are linear or branched alkyl groups, alkoxy groups, phenyl groups or hydrogen having 1 to 4 carbon atoms; B is an organic strong base, + B-H is the cation of the base obtained by an organic strong base removing a hydroxyl hydrogen; the epoxide is selected from the structure of formula (II):

[0010]

[0011] R 4 , R 5 are selected from hydrogen, linear or branched alkyl groups having 1 to 4 carbon atoms, allyl groups, phenyl groups, halogen or alkyl-substituted phenyl groups, chlorine or bromine-substituted alkyl groups, R 6 -O-CH2-, and the said R 6 is selected from phenyl groups, phenyl groups substituted with alkyl groups having 1 to 3 carbon atoms, allyl groups or linear or branched alkyl groups having 1 to 4 carbon atoms.

[0012] Preferably, the said R 1 is selected from linear or branched alkyl groups or hydrogen having 1 to 4 carbon atoms, and the substituents of R 2 , R 3 can be selected from linear or branched alkyl groups having 1 to 4 carbon atoms, alkoxy groups having 1 to 4 carbon atoms, phenyl groups or hydrogen.

[0013] More preferably, the said R 1 is selected from hydrogen, methyl, isopropyl, n-butyl, and R 2 or R 3 is selected from hydrogen, phenyl groups, linear or branched alkyl groups having 1 to 4 carbon atoms, alkoxy groups having 1 to 4 carbon atoms.

[0014] Preferably, the β-diketone anion catalyst shown in formula (I) is an ionic catalyst formed by a β-diketone shown in formula (III) and an organic strong base;

[0015]

[0016] wherein R 1 is hydrogen, methyl, isopropyl, or n-butyl, and R 2 , R 3 are methyl, isopropyl, butyl, tert-butyl, methoxy, ethoxy, tert-butoxy, phenyl, or hydrogen;

[0017] The organic strong base is selected from 4-methylpyridine (4-MP), 4-dimethylaminopyridine (DMAP), 4-pyrrolidinopyridine (4-PPY), 2-methyl-4-dimethylaminopyridine, 2,6-dimethyl-4-dimethylaminopyridine, 2-phenyl-4-dimethylaminopyridine, 2,6-diphenyl-4-dimethylaminopyridine, 2-tert-butyl-4-dimethylaminopyridine, 2,6-di-tert-butyl-4-dimethylaminopyridine, 1,8-diazabicycloundec-7-ene (DBU), 1,4-diazabicyclo[2.2.2]octane (DABCO), 7-methyl-1,5,7-triazabicyclo[4.4.0]dec-5-ene (MTBD).

[0018] The structural formulas of DBU, MTBD, DABCO, DMAP, 4-MP, and 4-PPY are as follows:

[0019]

[0020] Preferably, the reaction temperature of the preparation method is 60-120°C, the initial pressure of carbon dioxide is 0.1-2 MPa, the molar ratio of the β-diketone shown in formula (III) to the organic strong base is 1:1-3:1, and the molar ratio of the epoxide to the β-diketone anion catalyst is 100:10-100:1.

[0021] Preferably, the reaction temperature of the preparation method is 100°C or 120°C, the initial pressure of carbon dioxide is 0.1 MPa, the molar ratio of the β-diketone to the organic strong base is 1:1, and the molar ratio of the epoxide to the β-diketone anion catalyst is 100:5-100:1.

[0022] Preferably, the preparation method of the β-diketone anion catalyst shown in formula (I) uses the epoxide shown in formula (II) as a solvent, adds the β-diketone shown in formula (III) and the organic strong base, and the molar ratio of the β-diketone to the organic strong base is 1:1-1:3 to obtain the β-diketone anion catalyst.

[0023] Preferably, the β-diketone described in formula (III) is selected from the following structures:

[0024]

[0025] Preferably, the organic strong base is DBU, DABCO, MTBD, DMAP, 4-MP, 4-PPY;

[0026]

[0027] Preferably, the epoxide described in formula (II) is selected from 3-chloro-1,2-epoxypropane, 3-bromo-1,2-epoxypropane, 1,2-epoxyhexane, 1,2-epoxy-5-hexene, 4-chlorostyrene epoxide, 2-phenyloxirane, 2-(methoxymethyl)oxirane, 2-(tert-butoxymethyl)oxirane, 1-allyloxy-2,3-epoxypropane, 1,2-epoxy-3-phenoxypropane or 2-[(2-methylphenoxy)methyl]oxirane.

[0028] The structure of the epoxide is shown as follows:

[0029]

[0030] Preferably, the reaction temperature of the preparation method is 20-120 °C, the initial pressure of carbon dioxide is 0.1-2 MPa, the ratio of β-diketone to organic base is 1:1-3:1, and the dosage of the catalyst is 1 mol%-10 mol%;

[0031] Particularly preferably, the reaction temperature of the preparation method is 100 °C and 120 °C, the initial pressure of carbon dioxide is 0.1 MPa, the ratio of β-diketone to organic base is 1:1, and the dosage of the catalyst is 1 mol%-5 mol%.

[0032] Preferably, the specific steps of the preparation method include:

[0033] (1) Add β-diketone, strong base and epoxide to a Schlenk tube, stir at room temperature for 5-10 min, and then displace the air in the reaction vessel with carbon dioxide for more than 3 times;

[0034] (2) Charge CO2 into the reaction vessel to an initial pressure of 0.1 MPa and heat to 100 °C or 120 °C;

[0035] (3) React for 1-24 h, cool, and obtain the cyclic carbonate by column chromatography of the reaction solution.

[0036] Preferably, the preparation method of the catalyst includes the following steps:

[0037] A. At 0 °C, add β-diketone to acetone and stir, then add potassium carbonate in sequence. After stirring for 15 min, add an acetone solution of potassium iodide and continue stirring;

[0038] B. Stir the mixed solution at the reflux temperature for 24 h and let it stand;

[0039] C. Adsorb the potassium salt with diatomaceous earth and concentrate the filtrate;

[0040] D. The filtrate is allowed to stand for 5 - 6 h to obtain the catalyst.

[0041] E. At room temperature, with the epoxide as the solvent medium, the β - diketone obtained in step D reacts with an organic strong base to obtain the β - diketone anion catalyst.

[0042] In the present invention, the keto form of the β - diketone undergoes tautomerization to the enol form, and the strong base acts on the active hydrogen on the phenolic hydroxyl group to obtain the binary catalyst of β - diketone anion and the cation of the base. The hydrogen on the base has a hydrogen bond interaction with the oxygen on the epoxide, reducing the electron cloud density of the oxygen on the epoxide; the oxygen anion of the ketone carbonyl nucleophilically attacks the methylene carbon of the epoxide, breaking the C - O bond, and the formed carbanion activates carbon dioxide to generate cyclic carbonate.

[0043] Beneficial effects

[0044] Adopting the technical solution of the present invention has the following beneficial effects:

[0045] (1) The synthesis method of the catalyst used in the present invention is simple, and the raw materials are cheap and easily available.

[0046] (2) The present invention provides a method for synthesizing cyclic carbonate from carbon dioxide and epoxide under relatively mild conditions.

[0047] (3) The catalyst used in the present invention is metal - free, and the obtained product has no metal residue, showing great application prospects in the fields of biomedicine, etc.; the catalytic system used in the present invention is halogen - free and has no corrosion to general aluminum metal containers, which is conducive to further industrial application research.

[0048] (4) The reaction process does not require the use of solvents, avoiding the toxicity of organic solvents; the catalyst loading used in the present invention is small, which is beneficial to cost saving.

[0049] (5) The catalytic system used in the present invention consists of two parts (β - diketone and organic base), with relatively wide tunability and a flexible and variable system.

[0050] In summary, the present invention has obvious advantages such as simplicity, mildness, high efficiency, metal - free, halogen - free, and solvent - free compared with the existing catalytic systems. Brief description of the drawings

[0051] The embodiments of the present invention will be described in detail in conjunction with the accompanying drawings, where

[0052] Figure 1 : 1H NMR spectrum of the catalyst obtained in Example 1

[0053] Figure 2 : 13C NMR spectrum of the catalyst obtained in Example 1

[0054] Figure 3 : 1H NMR spectrum of the cyclic carbonate product obtained in Example 2

[0055] Figure 4 : 13C NMR spectrum of the cyclic carbonate product obtained in Example 2

[0056] Figure 5 : 1H NMR spectrum of the cyclic carbonate product obtained in Example 19

[0057] Figure 6 : 13C NMR spectrum of the cyclic carbonate product obtained in Example 19

[0058] Figure 7 : 1H NMR spectrum of the cyclic carbonate product obtained in Example 22

[0059] Figure 8 : 13C NMR spectrum of the cyclic carbonate product obtained in Example 22

[0060] Figure 9 : 1H NMR spectrum of the cyclic carbonate product obtained in Example 24

[0061] Figure 10 : 13C NMR spectrum of the cyclic carbonate product obtained in Example 24

[0062] Figure 11 : 1H NMR spectrum of the cyclic carbonate product obtained in Example 25

[0063] Figure 12 : 13C NMR spectrum of the cyclic carbonate product obtained in Example 25

[0064] Figure 13 : 1H NMR spectrum of the cyclic carbonate product obtained in Example 27

[0065] Figure 14 : 13C NMR spectrum of the cyclic carbonate product obtained in Example 27

[0066] Figure 15 : 1H NMR spectrum of the cyclic carbonate product obtained in Example 28

[0067] Figure 16 : 13C NMR spectrum of the cyclic carbonate product obtained in Example 28 Detailed Description of the Invention

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

[0069] The 1H NMR spectra involved in the examples were measured using a Bruker Ascend TM-400 nuclear magnetic resonance spectrometer from Bruker Corporation, and the deuterated reagent used was deuterated chloroform (CDCl3).

[0070] The structure of the catalytic system used in the examples is as follows:

[0071]

[0072] The structure of the organic base used in the examples is as follows:

[0073]

[0074] The structure of the epoxide used in the examples is as follows:

[0075]

[0076] Example 1:

[0077] Preparation of β-diketone 4: In a reaction flask, 10 mL (48 mmol) of 2,2,6,6-tetramethyl-3,5-pentanedione was dissolved in 25 mL of acetone, stirred until dissolved, and then 8.45 g (60 mmol) of potassium carbonate was added. 3.51 mL (55 mmol) of methyl iodide was dissolved in 5 mL of acetone, and the acetone solution of methyl iodide was added to the reaction flask. The reaction was continuously carried out at the reflux temperature for 4 - 12 h. Then the reaction solution was filtered, and 8 mL of a transparent liquid was obtained by standing. It was found to have impurities through TLC and NMR verification, and then by column chromatography, eluted with a concentration of petroleum ether:ethyl acetate = 2:1 to obtain β-diketone 4. Yield: 84%. The 1H NMR spectrum of β-diketone 4 is as shown in the appendix Figure 1 as follows, 1 H NMR(400MHz,Chloroform-d)δ4.45(q,J=6.9Hz,1H),1.27(dd,J=7.0,1.3Hz,3H),1.15(d,J=1.4Hz,17H). The 13C NMR spectrum is as Figure 2 follows, 13 CNMR(101MHz,Chloroform-d)δ212.16,49.07,44.67,27.50,15.69.

[0078] Example 2:

[0079] After removing water and oxygen from the Schlenk reaction tube, it was transferred into the glove box. β-diketone 1 (0.25 mmol), base compound 11 (0.25 mmol) and epoxide 19 (5 mmol) were successively added into the Schlenk reaction tube, stirred for 5 min, and after sealing the reaction tube, it was transferred out of the glove box. The gas in the tube was replaced by the double-tube technique. A balloon filled with CO2 was tied to the rubber stopper at the tube mouth to provide the CO2 required for the reaction, and it was placed in an oil bath at 120 °C for 24 h. After the reaction was completed, it was cooled, separated by a chromatographic column (petroleum ether: ethyl acetate = 5:1), and then the product was dried to obtain a brown oily liquid. Qualitative and quantitative analysis was carried out by 1H NMR, and the conversion rate was 79% and the selectivity was 41%. The 1H NMR spectrum of the product is shown in Figure 2 as follows, 1 1H NMR (400 MHz, Chloroform-d) δ 7.37–7.25 (m, 3H), 7.25 (dd, J = 7.4, 2.4 Hz, 2H), 5.57 (t, J = 8.0 Hz, 1H), 4.69 (t, J = 8.4 Hz, 1H), 4.22 (t, J = 8.2 Hz, 1H). The 13C NMR spectrum of the product is shown in Figure 3 as follows, 13 13C NMR (101 MHz, Chloroform-d) δ 154.94, 135.83, 129.66, 129.17, 125.92, 78.01, 71.17.

[0080] Example 3:

[0081] After removing water and oxygen from the Schlenk reaction tube, it was transferred into the glove box. β-diketone 2 (0.25 mmol), base compound 11 (0.25 mmol) and epoxide 19 (5 mmol) were successively added into the Schlenk reaction tube, stirred for 5 min, and after sealing the reaction tube, it was transferred out of the glove box. The gas in the tube was replaced by the double-tube technique. A balloon filled with CO2 was tied to the rubber stopper at the tube mouth to provide the CO2 required for the reaction, and it was placed in an oil bath at 120 °C for 24 h. After the reaction was completed, it was cooled, separated by a chromatographic column (petroleum ether: ethyl acetate = 5:1), and then the product was dried to obtain a brown oily liquid. Qualitative and quantitative analysis was carried out by 1H NMR, and the conversion rate was 84% and the selectivity was 40%.

[0082] Example 4:

[0083] After removing water and oxygen from the Schlenk reaction tube, it was transferred into a glove box. Then, β-diketone 3 (0.25 mmol), base compound 11 (0.25 mmol), and epoxide 19 (5 mmol) were successively added into the Schlenk reaction tube. After stirring for 5 min, the reaction tube was sealed and then transferred out of the glove box. The gas in the tube was displaced by the double-tube technique. A balloon filled with CO2 was tied to the rubber stopper at the tube mouth to provide the CO2 required for the reaction. Then, it was placed in an oil bath at 120 °C for 24 h. After the reaction was completed, it was cooled, separated by a chromatographic column (petroleum ether:ethyl acetate = 5:1), and the product was dried to obtain a brown oily liquid. Qualitative and quantitative analysis was carried out by 1H NMR, and the conversion rate was 76% and the selectivity was 43%.

[0084] Example 5:

[0085] After removing water and oxygen from the Schlenk reaction tube, it was transferred into a glove box. Then, β-diketone 4 (0.25 mmol), base compound 11 (0.25 mmol), and epoxide 19 (5 mmol) were successively added into the Schlenk reaction tube. After stirring for 5 min, the reaction tube was sealed and then transferred out of the glove box. The gas in the tube was displaced by the double-tube technique. A balloon filled with CO2 was tied to the rubber stopper at the tube mouth to provide the CO2 required for the reaction. Then, it was placed in an oil bath at 120 °C for 24 h. After the reaction was completed, it was cooled, separated by a chromatographic column (petroleum ether:ethyl acetate = 5:1), and the product was dried to obtain a brown oily liquid. Qualitative and quantitative analysis was carried out by 1H NMR, and the conversion rate was 80% and the selectivity was 40%.

[0086] Example 6:

[0087] After removing water and oxygen from the Schlenk reaction tube, it was transferred into a glove box. Then, β-diketone 5 (0.25 mmol), base compound 11 (0.25 mmol), and epoxide 19 (5 mmol) were successively added into the Schlenk reaction tube. After stirring for 5 min, the reaction tube was sealed and then transferred out of the glove box. The gas in the tube was displaced by the double-tube technique. A balloon filled with CO2 was tied to the rubber stopper at the tube mouth to provide the CO2 required for the reaction. Then, it was placed in an oil bath at 120 °C for 24 h. After the reaction was completed, it was cooled, separated by a chromatographic column (petroleum ether:ethyl acetate = 5:1), and the product was dried to obtain a brown oily liquid. Qualitative and quantitative analysis was carried out by 1H NMR, and the conversion rate was 55%.

[0088] Example 7:

[0089] After the Schlenk reaction tube was dehydrated and deoxygenated, it was transferred into a glove box. Then, β-diketone 6 (0.25 mmol), base compound 11 (0.25 mmol), and epoxide 19 (5 mmol) were successively added into the Schlenk reaction tube. After stirring for 5 min, the reaction tube was sealed and then transferred out of the glove box. The gas in the tube was displaced by the double-tube technique. A balloon filled with CO2 was tied to the rubber stopper at the tube mouth to provide the CO2 required for the reaction. Then, it was placed in an oil bath at 120 °C for 24 h. After the reaction was completed, it was cooled, separated by a chromatographic column (petroleum ether: ethyl acetate = 5:1), and the product was dried to obtain a brown oily liquid. Qualitative and quantitative analysis was carried out by 1H NMR, and the conversion rate was 64%.

[0090] Example 8:

[0091] After the Schlenk reaction tube was dehydrated and deoxygenated, it was transferred into a glove box. Then, β-diketone 7 (0.25 mmol), base compound 11 (0.25 mmol), and epoxide 19 (5 mmol) were successively added into the Schlenk reaction tube. After stirring for 5 min, the reaction tube was sealed and then transferred out of the glove box. The gas in the tube was displaced by the double-tube technique. A balloon filled with CO2 was tied to the rubber stopper at the tube mouth to provide the CO2 required for the reaction. Then, it was placed in an oil bath at 120 °C for 24 h. After the reaction was completed, it was cooled, separated by a chromatographic column (petroleum ether: ethyl acetate = 5:1), and the product was dried to obtain a brown oily liquid. Qualitative and quantitative analysis was carried out by 1H NMR, and the conversion rate was 72%.

[0092] Example 9:

[0093] After the Schlenk reaction tube was dehydrated and deoxygenated, it was transferred into a glove box. Then, β-diketone 8 (0.25 mmol), base compound 11 (0.25 mmol), and epoxide 19 (5 mmol) were successively added into the Schlenk reaction tube. After stirring for 5 min, the reaction tube was sealed and then transferred out of the glove box. The gas in the tube was displaced by the double-tube technique. A balloon filled with CO2 was tied to the rubber stopper at the tube mouth to provide the CO2 required for the reaction. Then, it was placed in an oil bath at 120 °C for 24 h. After the reaction was completed, it was cooled, separated by a chromatographic column (petroleum ether: ethyl acetate = 5:1), and the product was dried to obtain a brown oily liquid. Qualitative and quantitative analysis was carried out by 1H NMR, and the conversion rate was 78%.

[0094] Example 10:

[0095] After dehydrating and deoxygenating the Schlenk reaction tube, it was transferred into a glove box. Then, β-diketone 2 (0.25 mmol), base compound 9 (0.25 mmol), and epoxide 19 (5 mmol) were successively added into the Schlenk reaction tube. After stirring for 5 min, the reaction tube was sealed and then transferred out of the glove box. The gas in the tube was replaced by the double-tube technique. A balloon filled with CO2 was tied to the rubber stopper at the tube mouth to provide the CO2 required for the reaction. Then, it was placed in an oil bath at 120 °C for 24 h. After the reaction was completed, it was cooled, separated by a chromatographic column (petroleum ether:ethyl acetate = 5:1), and then the product was dried to obtain a brown oily liquid. Qualitative and quantitative analysis was carried out by 1H NMR, and the conversion rate was 30%.

[0096] Example 11:

[0097] After dehydrating and deoxygenating the Schlenk reaction tube, it was transferred into a glove box. Then, β-diketone 2 (0.25 mmol), base compound 10 (0.25 mmol), and epoxide 19 (5 mmol) were successively added into the Schlenk reaction tube. After stirring for 5 min, the reaction tube was sealed and then transferred out of the glove box. The gas in the tube was replaced by the double-tube technique. A balloon filled with CO2 was tied to the rubber stopper at the tube mouth to provide the CO2 required for the reaction. Then, it was placed in an oil bath at 120 °C for 24 h. After the reaction was completed, it was cooled, separated by a chromatographic column (petroleum ether:ethyl acetate = 5:1), and then the product was dried to obtain a brown oily liquid. Qualitative and quantitative analysis was carried out by 1H NMR, and the conversion rate was 28%.

[0098] Example 12:

[0099] After dehydrating and deoxygenating the Schlenk reaction tube, it was transferred into a glove box. Then, β-diketone 2 (0.25 mmol), base compound 12 (0.25 mmol), and epoxide 19 (5 mmol) were successively added into the Schlenk reaction tube. After stirring for 5 min, the reaction tube was sealed and then transferred out of the glove box. The gas in the tube was replaced by the double-tube technique. A balloon filled with CO2 was tied to the rubber stopper at the tube mouth to provide the CO2 required for the reaction. Then, it was placed in an oil bath at 120 °C for 24 h. After the reaction was completed, it was cooled, separated by a chromatographic column (petroleum ether:ethyl acetate = 5:1), and then the product was dried to obtain a brown oily liquid. Qualitative and quantitative analysis was carried out by 1H NMR, and the conversion rate was 43%.

[0100] Example 13:

[0101] After dehydrating and deoxygenating the Schlenk reaction tube, it was transferred into a glove box. Then, β-diketone 2 (0.25 mmol), base compound 13 (0.25 mmol), and epoxide 19 (5 mmol) were successively added into the Schlenk reaction tube. After stirring for 5 min, the reaction tube was sealed and then transferred out of the glove box. The gas in the tube was replaced by the double-tube technique. A balloon filled with CO2 was tied to the rubber stopper at the tube mouth to provide the CO2 required for the reaction. Then, it was placed in an oil bath at 120 °C for 24 h. After the reaction was completed, it was cooled, separated by a chromatographic column (petroleum ether:ethyl acetate = 5:1), and the product was dried to obtain a brown oily liquid. Qualitative and quantitative analysis was carried out by 1H NMR, and the conversion rate was 45%.

[0102] Example 14:

[0103] After dehydrating and deoxygenating the Schlenk reaction tube, it was transferred into a glove box. Then, β-diketone 2 (0.25 mmol), base compound 14 (0.25 mmol), and epoxide 19 (5 mmol) were successively added into the Schlenk reaction tube. After stirring for 5 min, the reaction tube was sealed and then transferred out of the glove box. The gas in the tube was replaced by the double-tube technique. A balloon filled with CO2 was tied to the rubber stopper at the tube mouth to provide the CO2 required for the reaction. Then, it was placed in an oil bath at 120 °C for 24 h. After the reaction was completed, it was cooled, separated by a chromatographic column (petroleum ether:ethyl acetate = 5:1), and the product was dried to obtain a brown oily liquid. Qualitative and quantitative analysis was carried out by 1H NMR, and the conversion rate was 53%.

[0104] Example 15:

[0105] β-Diketone 2 (0.25 mmol), base compound 11 (0.25 mmol), and epoxide 19 (10 mmol) were successively added into a stainless-steel pressure reaction tube. The reaction tube was sealed, and the gas in the tube was replaced with CO2 three times. Then, CO2 was filled into the reaction tube at a pressure of 1 MPa and placed in an oil bath at 100 °C for 12 h. After the reaction was completed, it was cooled. It was purified by column chromatography (petroleum ether:ethyl acetate = 5:1), and the product was dried to obtain a light yellow oily liquid. Qualitative and quantitative analysis was carried out by 1H NMR, and the conversion rate was 24%.

[0106] Example 16:

[0107] Add β-diketone 2 (0.25 mmol), base compound 11 (0.25 mmol) and epoxide 19 (10 mmol) into a stainless steel pressure reaction tube in sequence. Seal the reaction tube, displace the gas in the tube with CO2 three times, then charge CO2 into the reaction tube with a pressure of 1 MPa, place it in an oil bath at 120 °C, and react for 12 h. After the reaction is completed, cool it. Purify by column chromatography (petroleum ether: ethyl acetate = 5:1), and then dry the product to obtain a pale yellow oily liquid. Qualitative and quantitative analysis is carried out by 1H NMR, and the conversion rate is 51%.

[0108] Example 17:

[0109] Add β-diketone 2 (0.25 mmol), base compound 13 (0.25 mmol) and epoxide 19 (10 mmol) into a stainless steel pressure reaction tube in sequence. Seal the reaction tube, displace the gas in the tube with CO2 three times, then charge CO2 into the reaction tube with a pressure of 1 MPa, place it in an oil bath at 120 °C, and react for 12 h. After the reaction is completed, cool it. Purify by column chromatography (petroleum ether: ethyl acetate = 5:1), and then dry the product to obtain a pale yellow oily liquid. Qualitative and quantitative analysis is carried out by 1H NMR, and the conversion rate is 67%.

[0110] Example 18:

[0111] Add β-diketone 2 (0.5 mmol), base compound 13 (0.5 mmol) and epoxide 19 (10 mmol) into a stainless steel pressure reaction tube in sequence. Seal the reaction tube, displace the gas in the tube with CO2 three times, then charge CO2 into the reaction tube with a pressure of 1 MPa, place it in an oil bath at 120 °C, and react for 12 h. After the reaction is completed, cool it. Purify by column chromatography (petroleum ether: ethyl acetate = 5:1), and then dry the product to obtain a pale yellow oily liquid. Qualitative and quantitative analysis is carried out by 1H NMR, and the conversion rate is 97%.

[0112] Example 19:

[0113] Add β-diketone 2 (0.25 mmol), base compound 13 (0.25 mmol) and epoxide 15 (10 mmol) into a stainless steel pressure reaction tube in sequence. Seal the reaction tube, displace the air in the tube with CO2 three times, then charge CO2 into the reaction tube with a pressure of 1 MPa, place it in an oil bath at 120 °C, and react for 12 h. After the reaction is completed, cool it. Purify by column chromatography (petroleum ether: ethyl acetate = 5:1), and then dry the product to obtain a pale yellow oily liquid. Qualitative and quantitative analysis is carried out by 1H NMR, and the conversion rate is 98%. The 1H NMR spectrum of the product is as shown in the appendix Figure 5 as shown, and the 13C NMR spectrum is as shown in Figure 6 of the appendix. 11H NMR (400 MHz, Chloroform-d) δ 4.99 (ddt, J = 8.3, 5.7, 3.9 Hz, 1H), 4.55 (t, J = 8.7 Hz, 1H), 4.33 (dd, J = 8.9, 5.7 Hz, 1H), 3.80 (dd, J = 12.5, 4.3 Hz, 1H), 3.69 (dd, J = 12.5, 3.7 Hz, 1H).

[0114] Example 20:

[0115] Add β-diketone 2 (0.25 mmol), base compound 13 (0.25 mmol) and epoxide 16 (10 mmol) into a stainless steel pressure reaction tube in sequence. Seal the reaction tube, displace the air in the tube with CO2 three times, then fill the reaction tube with CO2 at a pressure of 1 MPa, place it in an oil bath at 120 °C, and react for 9 h. After the reaction is completed, cool it. Purify by column chromatography (petroleum ether:ethyl acetate = 5:1), and then dry the product to obtain a pale yellow oily liquid. Qualitative and quantitative analysis is carried out by 1H NMR, and the conversion rate is 99% and the yield is 96%.

[0116] Example 21:

[0117] Add β-diketone 2 (0.25 mmol), base compound 13 (0.25 mmol) and epoxide 17 (10 mmol) into a stainless steel pressure reaction tube in sequence. Seal the reaction tube, displace the air in the tube with CO2 three times. Then fill the reaction tube with CO2 at a pressure of 1 MPa, place it in an oil bath at 120 °C, and react for 12 h. After the reaction is completed, cool it. Purify by column chromatography (petroleum ether:ethyl acetate = 5:1), and then dry the product to obtain a pale yellow oily liquid. Qualitative and quantitative analysis is carried out by 1H NMR, and the conversion rate is 99% and the yield is 92%.

[0118] Example 22:

[0119] Add β-diketone 2 (0.25 mmol), base compound 13 (0.25 mmol) and epoxide 18 (10 mmol) into a stainless steel pressure reaction tube in sequence. Seal the reaction tube, displace the air in the tube with CO2 three times. Then fill the reaction tube with CO2 at a pressure of 1 MPa, place it in an oil bath at 120 °C, and react for 12 h. After the reaction is completed, cool it. Purify by column chromatography (petroleum ether:ethyl acetate = 5:1), and then dry the product to obtain a pale yellow oily liquid. Qualitative and quantitative analysis is carried out by 1H NMR, and the conversion rate is 98% and the yield is 97%. The 1H NMR spectrum of the product is as shown in the appendix Figure 7 as shown, and the 13C NMR spectrum is as shown in Figure 8. 11H NMR (400 MHz, Chloroform-d) δ 5.78 (ddt, J = 16.9, 10.1, 6.6 Hz, 1H), 5.10–5.01 (m, 2H), 4.72 (qd, J = 7.7, 5.1 Hz, 1H), 4.52 (t, J = 8.1 Hz, 1H), 4.09–4.05 (m, 1H), 2.25–2.11 (m, 2H), 1.98–1.86 (m, 1H), 1.80–1.71 (m, 1H).

[0120] Example 23:

[0121] The β-diketone catalyst 2 (0.5 mmol), the base compound 13 (0.5 mmol) and the epoxide 19 (10 mmol) were successively added to a stainless-steel pressure reaction tube. The reaction tube was sealed and the air in the tube was replaced with CO2 three times. Then, CO2 was charged into the reaction tube at a pressure of 1 MPa, and the reaction tube was placed in an oil bath at 120 °C for 12 h. After the reaction was completed, the reaction tube was cooled to 0 °C with an ice-water mixture, and the residual gas was released. The product was purified by column chromatography (petroleum ether:ethyl acetate = 5:1), and then the product was dried to obtain a pale yellow oily liquid. Qualitative and quantitative analysis was carried out by 1H NMR, and the conversion rate was 97% and the yield was 94%.

[0122] Example 24:

[0123] The β-diketone catalyst 2 (0.25 mmol), the base compound 13 (0.25 mmol) and the epoxide 20 (10 mmol) were successively added to a stainless-steel pressure reaction tube. The reaction tube was sealed and the air in the tube was replaced with CO2 three times. Then, CO2 was charged into the reaction tube at a pressure of 1 MPa, and the reaction tube was placed in an oil bath at 120 °C for 12 h. After the reaction was completed, it was cooled. The product was purified by column chromatography (petroleum ether:ethyl acetate = 5:1), and then the product was dried to obtain a pale yellow oily liquid. Qualitative and quantitative analysis was carried out by 1H NMR, and the conversion rate was 99% and the yield was 93%. The 1H NMR spectrum of the product is shown as follows, and the 13C NMR spectrum is shown in Figure 10. Figure 9 as shown, and the 13C NMR spectrum is shown in Figure 10. 1 1H NMR (400 MHz, Chloroform-d) δ 4.79 (ddt, J = 8.3, 6.1, 3.7 Hz, 1H), 4.47 (t, J = 8.4 Hz, 1H), 4.35–4.28 (m, 1H), 3.67–3.48 (m, 2H), 3.39 (s, 3H).

[0124] Example 25:

[0125] β-diketone catalyst 2 (0.25 mmol), base compound 13 (0.25 mmol), and epoxide 21 (10 mmol) were successively added to a stainless-steel pressure reaction tube. The reaction tube was sealed, and the air in the tube was replaced with CO2 three times. Then, CO2 with a pressure of 1 MPa was charged into the reaction tube, and it was placed in an oil bath at 120 °C for 12 h. After the reaction was completed, it was cooled. It was purified by column chromatography (petroleum ether:ethyl acetate = 5:1), and then the product was dried to obtain a pale yellow oily liquid. Qualitative and quantitative analysis was carried out by 1H NMR spectroscopy, and a conversion rate of 79% and a yield of 91% were obtained. The 1H NMR spectrum of the product is shown in the attached Figure 11 as shown, and the 13C NMR spectrum is shown in Figure 12 of the attached drawings. 1 1H NMR (400 MHz, Chloroform-d) δ 4.80–4.74 (m, 1H), 4.47 (t, J = 8.2 Hz, 1H), 4.42–4.37 (m, 1H), 3.61 (dd, J = 10.3, 4.7 Hz, 1H), 3.53 (dd, J = 10.3, 3.6 Hz, 1H), 1.19 (s, 9H).

[0126] Example 26:

[0127] β-diketone catalyst 2 (0.25 mmol), base compound 13 (0.25 mmol), and epoxide 22 (10 mmol) were successively added to a stainless-steel pressure reaction tube. The reaction tube was sealed, and the air in the tube was replaced with CO2 three times. Then, CO2 with a pressure of 1 MPa was charged into the reaction tube, and it was placed in an oil bath at 120 °C for 12 h. After the reaction was completed, it was cooled. It was purified by column chromatography (petroleum ether:ethyl acetate = 5:1), and then the product was dried to obtain a pale yellow oily liquid. Qualitative and quantitative analysis was carried out by 1H NMR spectroscopy, and a conversion rate of 93% and a selectivity of 71% were obtained.

[0128] Example 27:

[0129] β-diketone catalyst 2 (0.25 mmol), base compound 13 (0.25 mmol), and epoxide 23 (10 mmol) were successively added to a stainless-steel pressure reaction tube. The reaction tube was sealed, and the air in the tube was replaced with CO2 three times. Then, CO2 with a pressure of 1 MPa was charged into the reaction tube, and it was placed in an oil bath at 120 °C for 12 h. After the reaction was completed, it was cooled, and the residual gas was released. It was purified by column chromatography (petroleum ether:ethyl acetate = 5:1), and then the product was dried to obtain a pale yellow oily liquid. Qualitative and quantitative analysis was carried out by 1H NMR spectroscopy, and a conversion rate of 99% was obtained. The 1H NMR spectrum of the product is shown in the attached Figure 13 as shown, and the 13C NMR spectrum is shown in Figure 14 of the attached drawings. 1HNMR(400MHz,Chloroform-d)δ7.26–7.17(m,2H),6.95(tt,J=7.5,1.1Hz,1H),6.85–6.76(m,1H),4.96(dddd,J=8.1,5.9,4.4,3.6Hz,1H),4.58–4.45(m,1H),4.23–4.06(m,1H).

[0130] Example 28:

[0131] Add β-diketone catalyst 2 (0.25 mmol), base compound 13 (0.25 mmol) and epoxide 24 (10 mmol) into a stainless steel pressure reaction tube in sequence. Seal the reaction tube and displace the air in the tube with CO2 for 3 times. Then fill the reaction tube with CO2 at a pressure of 1 MPa, place it in an oil bath at 120 °C for 12 h. After the reaction is completed, cool it. Purify by column chromatography (petroleum ether:ethyl acetate = 5:1), and then dry the product to obtain a pale yellow oily liquid. Qualitative and quantitative analysis is carried out by 1H NMR, and the conversion rate is 99%. The 1H NMR spectrum of the product is as shown in the appendix Figure 15 as shown, and the 13C NMR spectrum is as shown in Figure 16. 1 H NMR(400MHz,Chloroform-d)δ7.16(td,J=4.5,2.3Hz,2H),6.93(td,J=7.4,1.0Hz,1H),6.82–6.73(m,1H),5.05(ddt,J=8.6,5.5,3.3Hz,1H),4.65–4.54(m,2H),4.26(dd,J=10.6,3.6Hz,1H),4.13(dd,J=10.6,3.1 Hz,1H).

Claims

1. A method for preparing a cyclic carbonate, characterized in that: The β-diketone anion catalyst shown in formula (I) catalyzes the cycloaddition reaction of epoxides with carbon dioxide to obtain cyclic carbonates. ； wherein R 1 is a straight-chain or branched-chain alkyl group having 1 to 4 carbon atoms or hydrogen, R 2 , R 3 is a straight-chain or branched-chain alkyl group having 1 to 4 carbon atoms, an alkoxy group having 1 to 4 carbon atoms, a phenyl group or hydrogen; B is an organic strong base, + B-H is the cation of the base obtained by an organic strong base taking one hydroxy hydrogen; the epoxide is selected from the structure of formula (II): ； R 4 and R 5 is selected from hydrogen, a linear or branched alkyl group having 1 to 4 carbon atoms, allyl, phenyl, halogen-substituted phenyl, R 6 -O-CH2-, where the R 6 is selected from phenyl, phenyl substituted by an alkyl group having 1 to 3 carbon atoms, allyl or a linear or branched alkyl group having 1 to 4 carbon atoms.

2. The preparation method according to claim 1, characterized in that: The described R 1 is selected from hydrogen, methyl, isopropyl, n-butyl, and R 2 or R 3 is selected from hydrogen, phenyl, a straight-chain or branched alkyl group having 1 to 4 carbon atoms, and an alkoxy group having 1 to 4 carbon atoms.

3. The preparation method according to claim 1, wherein The β-diketone anion catalyst shown in formula (I) is an ionic catalyst formed by the β-diketone shown in formula (III) and an organic strong base; ； wherein R 1 is hydrogen, methyl, isopropyl, n-butyl, R 2 , R 3 is methyl, isopropyl, butyl, tert-butyl, methoxy, ethoxy, tert-butoxy, phenyl or hydrogen; The organic strong bases are selected from 4-methylpyridine, 4-dimethylaminopyridine, 4-pyrrolidinopyridine, 2-methyl-4-dimethylaminopyridine, 2,6-dimethyl-4-dimethylaminopyridine, 2-phenyl-4-dimethylaminopyridine, 2,6-diphenyl-4-dimethylaminopyridine, 2-tert-butyl-4-dimethylaminopyridine, 2,6-di-tert-butyl-4-dimethylaminopyridine, 1,8-diazabicycloundec-7-ene, 1,4-diazabicyclo[2.2.2]octane, 7-methyl-1,5,7-triazabicyclo[4.4.0]dec-5-ene.

4. The preparation method according to claim 3, characterized in that: The reaction temperature of the preparation method is 60-120 °C, the initial pressure of carbon dioxide is 0.1-2 MPa, the molar ratio of the β-diketone shown in formula (III) to the organic strong base is 1:1-3:1, and the molar ratio of the epoxide to the β-diketone anion catalyst is 100:10-100:

1.

5. The preparation method according to claim 3, characterized in that: The reaction temperature of the preparation method is 100 °C or 120 °C, the initial pressure of carbon dioxide is 0.1 MPa, the molar ratio of the β-diketone to the organic strong base is 1:1, and the molar ratio of the epoxide to the β-diketone anion catalyst is 100:5-100:

1.

6. The preparation method according to claim 1, characterized in that: The preparation method of the β-diketone anion catalyst shown in formula (I) uses the epoxide shown in formula (II) as a solvent, adds the β-diketone shown in formula (III) and the organic strong base, and the molar ratio of the β-diketone to the organic strong base is 1:1-1:3 to obtain the β-diketone anion catalyst. ； In the β-diketone represented by the formula (III), R 1 is hydrogen, methyl, isopropyl, or n-butyl, and R 2 , R 3 are methyl, isopropyl, butyl, tert-butyl, methoxy, ethoxy, tert-butoxy, phenyl, or hydrogen.

7. According to the preparation method described in claim 3 or 6, it is characterized in that: The structure of the β-diketone shown in formula (III) is as follows: 。 8. A preparation method of a cyclic carbonate, characterized in that: The β-diketone anion catalyst shown in formula (I) catalyzes the cycloaddition reaction of epoxides with carbon dioxide to obtain cyclic carbonates. ； wherein R 1 is a straight-chain or branched-chain alkyl group having 1 to 4 carbon atoms or hydrogen, R 2 , R 3 is a straight-chain or branched-chain alkyl group having 1 to 4 carbon atoms, a phenyl group or hydrogen; B is an organic strong base, + B-H is a cation of a base obtained by an organic strong base taking one hydroxyl hydrogen; The epoxides are selected from 3-chloro-1,2-epoxypropane, 3-bromo-1,2-epoxypropane, 1,2-epoxyhexane, 1,2-epoxy-5-hexene, 4-chlorostyrene epoxide, 2-phenyloxirane, 2-(methoxymethyl)oxirane, 2-(tert-butoxymethyl)oxirane, 1-allyloxy-2,3-epoxypropane, 1,2-epoxy-3-phenoxypropane or 2-[(2-methylphenoxy)methyl]oxirane.

9. A method for preparing a cyclic carbonate, characterized in that: The specific steps include: ； (1) Add the β-diketone shown in formula (III), the organic strong base and the epoxide shown in formula (II) to a reaction vessel, and discharge the air in the reaction vessel; (2) Under carbon dioxide gas, set the reaction temperature to 100-120 °C; (3) React for 1-24 h, cool, and obtain the cyclic carbonate by column chromatography of the reaction solution; wherein R 1 is hydrogen, methyl, isopropyl, n-butyl, R 2 , R 3 is methyl, isopropyl, butyl, tert-butyl, methoxy, ethoxy, tert-butoxy, phenyl or hydrogen; R 4 、R 5 is selected from hydrogen, a linear or branched alkyl group having 1 to 4 carbon atoms, an allyl group, a phenyl group, a halogen-substituted phenyl group, R 6 -O-CH2-, and the R 6 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 linear or branched alkyl group having 1 to 4 carbon atoms.

10. A method for preparing a cyclic carbonate, characterized in that: The specific steps include: ； (1) Add the β-diketone shown in formula (III), the organic strong base, and the epoxide shown in formula (II) to the reaction vessel, and evacuate the air in the reaction vessel; (2) Under a carbon dioxide gas atmosphere, set the reaction temperature to 100 - 120 °C; (3) React for 1 - 24 h, cool, and obtain the cyclic carbonate from the reaction solution by column chromatography; wherein R 1 is hydrogen, methyl, isopropyl, n-butyl, R 2 , R 3 is methyl, isopropyl, butyl, tert-butyl, methoxy, ethoxy, tert-butoxy, phenyl or hydrogen; The epoxide shown in formula (II) is selected from 3-chloro-1,2-epoxypropane, 3-bromo-1,2-epoxypropane, 1,2-epoxyhexane, 1,2-epoxy-5-hexene, 4-chlorostyrene epoxide, 2-phenyloxirane, 2-(methoxymethyl)oxirane, 2-(tert-butoxymethyl)oxirane, 1-allyloxy-2,3-epoxypropane, 1,2-epoxy-3-phenoxypropane, or 2-[(2-methylphenoxy)methyl]oxirane.

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