A pyridyl fluorohydrin functional ionic liquid, its preparation method and use

Abstract

The application provides a pyridyl fluorol functional ionic liquid, which is a single-ion or double-ion ionic liquid containing a pyridyl fluorol functional group and has a structure as shown in formula 1a or 1b. The application also provides a preparation method and application of the pyridyl fluorol functional ionic liquid. The single-ion ionic liquid is synthesized through multiple steps such as Zincke reaction and anion exchange, and the double-ion ionic liquid is prepared by protonation reaction of the single-ion ionic liquid and a superbase. The pyridyl fluorol functional ionic liquid is used for catalyzing resource conversion of CO2, and exhibits excellent catalytic performance in the process of preparing cyclic carbonate, carbamate and quinazoline-2,4(1H,3H)-dione from CO2.

Description

Technical Field

[0001] This invention relates to a pyridyl fluorohydrin functional ionic liquid, its preparation method, and its application as a catalyst in the high-value conversion of CO2, belonging to the field of synthetic and catalytic chemistry. Background Technology

[0002] Carbon dioxide (CO2) is a major greenhouse gas and also an abundant, non-toxic, inexpensive, and non-flammable renewable C1 resource. Using CO2 as a raw material to produce chemicals can reduce greenhouse gas emissions and achieve the resource utilization of CO2. Currently, CO2 conversion and utilization mainly involves chemical reactions to produce cyclic carbonates, dimethyl carbonate (DMC), carbamates, methanol, urea, and other liquid fuels and chemicals. These intermediate products can be further synthesized into alcohol ethers, methane fuels, ethylene / ethylene glycol / carbonates / polycarbonates / isocyanates, and other bulk or important chemicals. However, due to the thermodynamic stability and chemical inertness of CO2, effective catalytic systems are usually required to activate it. Many catalysts have been developed, such as bases, metal salts, metal oxides, metal-organic frameworks (MOFs), covalent organic compounds (COFs), and their functional ionic liquids. These catalysts typically require the use of metals, co-catalysts, volatile organic solvents, or harsh conditions such as high temperature (above 100°C) and high pressure to achieve good catalytic performance in the CO2 conversion process. Against the backdrop of a time when we are strongly advocating the development of new technologies / processes that are energy-saving, emission-reducing, efficient, and sustainable, it is particularly important to design metal-free, green organic catalysts that can achieve efficient CO2 conversion under mild conditions.

[0003] Ionic liquids (ILs) are a class of ionic compounds composed of organic cations and organic or inorganic anions. They possess excellent properties such as stability, easily tunable structure, and ionic synergy, and are widely used in separation catalysis, new energy, and new materials. Numerous academic studies utilizing ionic liquids for CO2 capture / catalytic activation have been reported. Furthermore, green technologies based on ionic liquids for CO2 capture, separation, and conversion (such as the co-production of dimethyl carbonate and ethylene glycol from CO2 and ethylene oxide, and the preparation of corresponding carbamates (isocyanate intermediates) from CO2 and amine compounds) have been developed. A review of related academic research and industrial technology development reveals that, for ionic liquids, especially metal-free ionic liquids, the key to improving their CO2 catalytic performance lies in designing basic active sites to increase the ability to capture CO2, thereby enhancing concentration and efficiency. Low-melting-point proton-containing ionic liquids can be synthesized through neutralization reactions using superbases and weak proton donors (such as fluorinated alcohols, imidazoles, pyrrolidones, or phenols). These liquids can reversibly and rapidly capture CO2 with extremely high capacity (more than 1 mol per mol IL) (Angew. Chem. Int. Ed. 2010, 49, 5978–5981). These superbase-derived proton-containing ionic liquids, especially those with strong proton acceptor properties, also exhibit excellent catalytic activation of CO2 under mild conditions. A protic ionic liquid (DBUH][TFE]) prepared in one step from superbase 1,8-diazabicyclo-[5.4.0]-7-undecene (DBU) and trifluoroethanol can catalyze the reaction of CO2 with 2-aminobenzonitrile to prepare quinazoline-2,4(1H,3H)-diketones at ambient pressure and room temperature, exhibiting excellent selectivity and yield (Angew. Chem. Int. Ed. 2014, 53, 5922–5925). The protic ionic liquid 1,8-diazabicyclo-[5.4.0]-7-undecene-2-methylimidazoline ([DBUH][MIm]) also demonstrates excellent catalytic performance in the synthesis of α-alkylene cyclic carbonates from the reaction of CO2 with propargyl alcohol. In ionic liquids, both cations and anions are crucial in catalytic reactions. Ionic liquids (ILs) promote the deprotonation of hydroxyl groups, CO2 electrophilic attack, and intramolecular cyclization steps by capturing and donating hydrogen protons (ChemSusChem 2017, 10, 1120–1127). On the other hand, introducing hydrogen bond donor groups allows for the modulation of the number of hydrogen bond donors and acidity, thereby controlling their ability to activate reaction substrates and / or stabilize reaction intermediates. Hydrogen bonds play a vital role in maintaining the structure and function of proteins and nucleic acids in biological systems. Similar to natural ecosystems, organocatalysis utilizing hydrogen bonds to accelerate and control chemical reactions has received particular attention in recent years. Many compounds containing hydrogen bond donor groups, such as phenolic derivatives, diols, carboxylic acids, guanidines, silanols, and fluoroalcohols, are often used as co-catalysts in synergistic studies with ionic liquids for the catalytic utilization of CO2 resources.For example, fluorinated alcohols, used as hydrogen bond donors in combination with quaternary ammonium salts, enabled the rapid coupling of CO2 and epoxides to cyclic carbonates under solvent-free and mild experimental conditions. Compared to catalytic systems without hydrogen bond donor promoters, hydrogen bond donors with hexafluorool functional groups significantly promoted the chemofixation of CO2 to epoxides, with phenyl difluorool promoters showing the best activity; when combined with Bu4NI, the reaction rate was increased by 20,800% (ChemSusChem 2015, 8, 1845-1849). Recently, the Institute of Process Engineering prepared a series of bifunctional single-component catalysts, consisting of fluorinated alcohol-functionalized quaternary ammonium compounds and imidazole ionic liquids as hydrogen bond donors for fluorinated alcohols and nucleophiles, via amine-aldehyde condensation / quaternization reactions, demonstrating excellent catalytic performance in the cycloaddition reactions of CO2 and epoxides (CN202010188049.X).

[0004] Furthermore, fluorinated alcohols, compared to non-fluorinated alcohols, possess unique properties such as strong hydrogen bonding ability, strong carbocation stabilization ability, high polarity, weak nucleophilicity, and strong oxidative stability. As solvents, co-solvents, catalysts, and auxiliaries, they are widely used in biochemistry, polymer science, materials synthesis, organic chemistry, and electrochemistry, demonstrating their unique advantages and roles. In organic chemistry, fluorinated alcohols have been shown to have special accelerating and promoting effects on various organic reactions. For example, in HFIP solvent, hydrogen peroxide increases the epoxidation rate of olefins by five orders of magnitude; HFIP can effectively activate N-halosuccinimide reagents, thereby promoting the halonamidation and halolactoneation of unactivated olefins; HFIP can act as a hydrogen bond donor, improving the catalytic efficiency of simple protic acid catalysts in carbonyl-olefin metathesis reactions by stabilizing all transition states and intermediates in the reaction pathway. In biochemistry, trifluoroethanol (TFE) and hexafluoroisopropanol (HFIP) are used to modify protein conformations; 3-Bis-HFAB is used for controlled peptide synthesis. In polymer chemistry, the use of HFIP solvents can improve the control over the relative molecular mass and stereoregularity of the resulting polymers.

[0005] Therefore, in this invention, it is necessary to develop a single-ion pyridyl fluoro alcohol functional ionic liquid that combines the dual properties of fluorinated alcohols and ionic liquids, as well as a dual-ion protonated ionic liquid prepared by protonation neutralization reaction with a superbase, thereby broadening the types and functions of fluorinated alcohol derivatives and providing a new idea and method for the development of novel and efficient catalysts for CO2 resource conversion. Summary of the Invention

[0006] The purpose of this invention is to provide a pyridyl fluorool functional ionic liquid, its preparation method, and its uses. The pyridyl fluorool functional ionic liquid has the structure shown in formula 1a or 1b:

[0007]

[0008] Wherein, R1 is a hydrocarbon group; preferably, R1 is any one of -(CH2)n- and phenyl, where n is a positive integer not less than 0;

[0009] Among them, R2, R3, R4, R5, and R6 are each independently selected from H and -(CH2). n CH3, -(CH2) n OH, -(CH2) n Any one of COOH, where n is 0, 1, 2, 3, 4, 5, 6.

[0010] Y - Selected from Cl - ,Br - I - HCO3 - OAc - OH - NTf2 - CF3SO3 - BF4 - PF6 - Any one of them;

[0011] M + Selected from One or more of the following.

[0012] As a further optimization of the present invention, the anion Y - For Cl - , Br - Or I - The preparation method of 1a ionic liquid includes the following steps:

[0013] (1) 2,4-Dinitrohalobenzene (X = Cl, Br, I) and Synthetic Zincke salt

[0014] (2) The Zincke salt and aminofluorool compounds were synthesized in step (1). A fluorinated alcohol-based functionalized ionic liquid containing a halide anion was prepared via the Zincke reaction. Where Y = X = Cl, Br, I.

[0015] For example:

[0016] The reaction that generates Zincke salt in step (1) (with) For example, the condition is: to Dissolve in an appropriate amount of acetone, add The mixed suspension was refluxed at 55°C for 30 h. Solvent was removed by rotary evaporation, solid residue was removed by filtration, and the product was washed repeatedly with hexane to obtain a pale yellow powder.

[0017] The Zincke reaction described in step (2) (with) For example, the condition is: to It was uniformly dispersed in a binary solvent of ethanol:H2O (4:1) and stirred at room temperature for 30 min, then added... Triethylamine. The mixed suspension was placed in a round-bottom flask and stirred under reflux at 120°C for 30 h. The binary solvent was removed by rotary evaporation, and the sample was washed several times with diethyl ether. The product was then vacuum dried at 55°C to obtain the final product.

[0018] As a further optimization of the present invention, the anion Y - HCO3 - OAc - OH - NTf2 - CF3SO3 - BF4 - or PF6 - The preparation method of 1a ionic liquid includes the following steps:

[0019] (1) 2,4-Dinitrohalobenzene (X = Cl, Br, I) and Synthetic Zincke salt

[0020] (2) The Zincke salt and aminofluorool compounds were synthesized in step (1). A fluorinated alcohol-based functionalized ionic liquid containing a halide anion was prepared via the Zincke reaction.

[0021] (3) The halogen-containing anion-based fluorohydrin functionalized ionic liquid synthesized in step (2) is reacted with an inorganic salt containing the target anion via a metathesis reaction, resulting in anion displacement, to obtain the fluorohydrin functionalized ionic liquid containing the target anion.

[0022] Preferably, the salt containing the target anion comprises any one or at least two combinations of KHCO3, HOAc, KOH, Li(NTf2)2, NaBF4, NaCF3SO3, and NaPF6.

[0023] For example:

[0024] The reaction that generates Zincke salt in step (1) (with) (For example) the reaction conditions refer to The difference in the synthesis steps lies in... Replace with

[0025] The Zincke reaction described in step (2) (with) (For example) the condition is to refer to The difference in the synthesis steps lies in... Replace with Will Replace with

[0026] The metathesis reaction described in step (3) (with) For example, the condition is: 1 mmol of the synthesized... The mixture of lithium bromide and 1.1 mmol of Li(NTf2)2 alcohol was stirred at 60 °C for 16 h. The solid lithium bromide was then removed by filtration, the solvent was removed by rotation, and the product was dried under vacuum at 80 °C to obtain the final product.

[0027] As a further optimization of the present invention, the 1b ionic liquid is obtained by neutralization reaction of the fluorohydrin functional ionic liquid 1a with an organic nitrogen-containing heterocyclic superbase, resulting in a dual-ionic strongly basic fluorohydrin functional ionic liquid 1b.

[0028] For example:

[0029] The neutralization reaction (with) For example, the condition is: to Dissolve in an appropriate amount of methanol, add excess Heat to 70°C and stir for 3 hours. Evaporate the solvent using a rotary evaporator, and wash with carbon tetrachloride to remove impurities. The crude product was obtained. It was then dried in a vacuum oven at 60°C to obtain the target product.

[0030] The pyridyl fluorohydrin functional ionic liquid described in this invention is used as a catalyst for CO2 resource recovery and high-value utilization reactions. Preferably, the CO2 resource recovery and high-value utilization includes reactions to prepare cyclic carbonates, carbamates, and quinazoline-2,4(1H,3H)-diones from CO2.

[0031] Compared with existing technologies, this invention has the following advantages: This invention is the first to design and synthesize a single-ion pyridyl fluorohydrin functional ionic liquid possessing both fluorohydrin and ionic liquid properties, as well as a dual-ion protonated ionic liquid prepared by protonation neutralization with a superbase, thus broadening the types, functions, and application fields of fluorohydrin derivatives. It also enriches the types of ionic liquids and provides a new idea and method for the development of novel and efficient catalysts for CO2 resource conversion. The synthesis method is simple, with good thermal stability. It exhibits excellent catalytic performance in the catalytic preparation of cyclic carbonates, carbamates, and quinazolin-2,4(1H,3H)-diketones from CO2, thanks to the synergistic effect of CO anion absorption and concentration, strong hydrogen bonding promotion by NH groups, and nucleophilic ring-opening multi-site action of halide anions. High selectivity and high product yield are also achieved under mild conditions (normal pressure). Therefore, this invention provides an excellent, easily prepared, thermally stable, and sustainable single-component high-value catalyst for CO2 resource conversion, with potential industrial applications. Attached Figure Description

[0032] Figure 1 This is the ESI spectrum of 4-(1,1,1,3,3,3-hexafluoro-2-hydroxyisopropyl)phenylpyridine bromide, a single-ionic pyridyl fluorohydrin functional ionic liquid prepared in Example 1 of this invention.

[0033] Figure 2 The 1H and 1C NMR spectra of the monoionic pyridyl fluorohydrin functional ionic liquid 4-(1,1,1,3,3,3-hexafluoro-2-hydroxyisopropyl)phenylpyridine bromide prepared in Example 1 of this invention are shown below. Detailed Implementation

[0034] The technical solution of the present invention will be further illustrated below through specific embodiments.

[0035] Those skilled in the art will understand that the embodiments described are merely illustrative of the invention and should not be construed as limiting the invention.

[0036] Example 1: Preparation of 4-(1,1,1,3,3,3-hexafluoro-2-hydroxyisopropyl)phenylpyridine bromide

[0037] The synthetic route is as follows:

[0038]

[0039] The specific steps are as follows:

[0040] (1) Synthesis of N-(2,4-dinitrophenyl)pyridine bromide: 2.15 mL of pyridine was dissolved in 25.50 mL of acetone, and 6.48 g of 2,4-dinitrobromobenzene was added. The mixture was stirred at 55 °C and refluxed for 30 h. The solvent was removed by rotary evaporation, the solid residue was removed by filtration, and the reaction mixture was washed with hexane to obtain a pale yellow powder product.

[0041] (2) Synthesis of 4-(1,1,1,3,3,3-hexafluoro-2-hydroxyisopropyl)phenylpyridine bromide: 4.02 mmol of N-(2,4-dinitrophenyl)pyridine bromide was dissolved in 40 mL of a binary solvent of ethanol and H2O (n(ethanol):n(H2O) = 4:1). The mixture was stirred at room temperature for 30 min, and then 4 mmol of 2-(4-aminophenyl)-hexafluoro-2-propanol and 4 mmol of triethylamine were added. The mixed suspension was then transferred to a 250 mL round-bottom flask and refluxed at 120 °C for 30 h. The binary solvent was removed by rotary evaporation, and the sample was washed several times with diethyl ether. The sample was then dried under vacuum at 55 °C to obtain a brown solid product.

[0042] Example 2: [DBUH] + ][( - OCF3 CF3)CPhPy + ][Br - Preparation of ]

[0043] The synthetic route is as follows:

[0044]

[0045] The specific steps are as follows:

[0046] 3 mmol of 4-(1,1,1,3,3,3-hexafluoro-2-hydroxyisopropyl)phenylpyridine bromide was dissolved in an appropriate amount of methanol, and 3.5 mmol of DBU was added. The mixture was stirred and heated to 70 °C and reacted for 3 h. The solvent was evaporated by rotary evaporator, and DBU was removed by washing with carbon tetrachloride to obtain the crude product. The crude product was dried in a vacuum oven at 60 °C to obtain the target product.

[0047] Example 3: Preparation of 1-(1,1,1,3,3,3-hexafluoro-2-hydroxypropyl)-4-carboxypyridine bis(trifluoromethanesulfonyl)imide salt

[0048] The synthetic route is as follows:

[0049]

[0050] The specific steps are as follows:

[0051] (1) Synthesis of (2,4-dinitrophenyl)-4-carboxypyridine bromide: The synthesis method is the same as step (1) in Example 1, except that pyridine is replaced with 4-carboxypyridine, and the target product is obtained after reaction.

[0052] (2) Synthesis of 1-(1,1,1,3,3-hexafluoro-2-hydroxypropyl)-4-carboxypyridine bromide: The method is the same as step (2) in Example 1, except that N-(2,4-dinitrophenyl)pyridine bromide is replaced with (2,4-dinitrophenyl)-4-carboxypyridine bromide, and 2-(4-aminophenyl)-hexafluoro-2-propanol is replaced with 2-aminohexafluoroisopropanol. The target product is obtained after the reaction.

[0053] (3) Synthesis of 1-(1,1,1,3,3-hexafluoro-2-hydroxypropyl)-4-carboxypyridine bis(trifluoromethanesulfonyl)imide salt: The synthesized 1-(1,1,1,3,3-hexafluoro-2-hydroxypropyl)-4-carboxypyridine bromide salt and Li(NTf2)2 were mixed in a methanol solution at a ratio of 1:1.1 and stirred at 60 °C for 16 h. Then, the lithium bromide solid was removed by filtration, the solvent was removed by rotary evaporation, and the product was dried under vacuum at 80 °C to obtain the final product.

[0054] Example 4: [TMGH] + ]2[( - OOC)( - OCF3 CF3)CPy + ][NTf2 - Preparation of ]

[0055] The synthetic route is as follows:

[0056]

[0057] The specific steps are as follows:

[0058] 3 mmol of 1-(1,1,1,3,3-hexafluoro-2-hydroxypropyl)-4-carboxypyridine bis(trifluoromethanesulfonyl)imide salt and tetramethylguanidine were dissolved in an appropriate amount of methanol at a ratio of 1:5. The mixture was stirred and heated to 70 °C and reacted for 3 h. The solvent was evaporated by rotary evaporator, and the tetramethylguanidine was removed by washing with carbon tetrachloride to obtain the crude product. The crude product was then dried in a vacuum oven at 60 °C to obtain the target product.

[0059] Application Example 1:

[0060] The monoionic pyridyl fluorohydrin functional ionic liquid prepared in Example 1 was used as a catalyst for the addition reaction of CO2 and propylene oxide to prepare propylene carbonate. The specific steps were as follows: 0.4 mmol of the ionic liquid and 20.0 mmol of propylene oxide were added to a 50 mL high-pressure reactor. CO2 at 2.5 MPa was added, and the mixture was heated to 80 °C and stirred continuously for 6 h. The product was diluted with ethyl acetate, and gas chromatography analysis showed that the yield of propylene carbonate was 98%, with a selectivity ≥99%.

[0061] Application Example 2:

[0062] The monoionic pyridyl fluorohydrin functional ionic liquid prepared in Example 1 was used as a catalyst for the addition reaction of CO2 and epoxidized styrene to prepare styrene cyclic carbonates. The specific steps were as follows: 0.4 mmol of the ionic liquid and 20.0 mmol of epoxidized styrene were added to a 50 mL high-pressure reactor. 2.5 MPa CO2 was added, and the mixture was heated to 90 °C and stirred continuously for 12 h. The product was diluted with ethyl acetate, and gas chromatography analysis showed that the yield of propylene carbonate was 91%, with a selectivity ≥99%.

[0063] Application Example 3:

[0064] The biionic pyridyl fluorohydrin functional ionic liquid prepared in Example 2 was used as a catalyst for the preparation of quinazoline-2,4(1H,3H)-dione. The specific steps were as follows: 10.0 mmol of the ionic liquid and 10.0 mmol of 2-aminobenzonitrile were added to a 50 mL high-pressure reactor. 0.1 MPa CO2 was added, and the mixture was heated to 40 °C with continuous stirring for 10 h. The product was diluted with methyl tert-butyl ether, and gas chromatography analysis showed that the yield of quinazoline-2,4(1H,3H)-dione was 94%, with a selectivity ≥99%.

[0065] Application Example 4:

[0066] The monoionic pyridyl fluorohydrin functional ionic liquid prepared in Example 3 was used as a catalyst for the addition reaction of CO2 with p-chlorostyrene epoxide to prepare p-chlorostyrene cyclic carbonates. The specific steps were as follows: 0.4 mmol of the ionic liquid and 20.0 mmol of epoxide were added to a 50 mL high-pressure reactor. 2.5 MPa CO2 was added, and the mixture was heated to 100 °C and stirred continuously for 12 h. The product was diluted with ethyl acetate, and gas chromatography analysis showed that the yield of p-chlorostyrene cyclic carbonates was 93%, with a selectivity ≥99%.

[0067] Application Example 5:

[0068] The biionic pyridyl fluorohydrin functional ionic liquid prepared in Example 4 was used as a catalyst for the preparation of carbamates. The specific steps were as follows: 2.0 mmol of the ionic liquid, 2.0 mmol of aniline, 2.0 mol of methanol, and 2.5 mL of dibromomethane were added to a 50 mL high-pressure reactor. 1.0 MPa of CO2 was added, and the mixture was heated to 60 °C and stirred continuously for 7 h. A small amount of the mixture was filtered and analyzed by gas chromatography, yielding a carbamate yield of 92% and a selectivity ≥99%.

Claims

1. A pyridyl fluorohydrin functional ionic liquid, characterized in that, The ionic liquid has a structure of formula 1a or 1b: or Wherein, R1 is a hydrocarbon group, which is -(CH2)n- or phenylene, n=0; R2, R3, R4, R5, and R6 are each independently selected from H and -(CH2)nCOOH, n=0; Y - Selected from Br - NTf2 - One of them; M + Selected from , One of them.

2. The method for preparing ionic liquid according to claim 1, characterized in that, The Y - For Br - The preparation method of 1a ionic liquid includes the following steps: (1) 2,4-Dinitrohalobenzene (X=Br) and Synthetic Zincke salt (2) The Zincke salt and aminofluorool compounds were synthesized in step (1). A fluorinated alcohol-based functionalized ionic liquid containing a halide anion was prepared via the Zincke reaction. , where X = Br.

3. The method for preparing ionic liquid according to claim 1, characterized in that, The Y - For NTf2 - The preparation method of 1a ionic liquid includes the following steps: (1) 2,4-Dinitrohalobenzene (X=Br) and Synthetic Zincke salt (2) The Zincke salt and aminofluorool compounds were synthesized in step (1). A fluorinated alcohol-based functionalized ionic liquid containing a halide anion was prepared via the Zincke reaction. (3) The halogen-containing anion-functionalized ionic liquid of fluorinated alcohol synthesized in step (2) is reacted with an inorganic salt containing the target anion in a metathesis reaction, and the anion is replaced to obtain the fluorinated alcohol-functionalized ionic liquid containing the target anion. ; The salt containing the target anion is LiNTf. 2。 4. The method for preparing ionic liquid according to claim 1, characterized in that, The 1b ionic liquid is obtained by neutralizing the fluorohydrin functional ionic liquid 1a with an organic nitrogen-containing heterocyclic superbase, resulting in a dual-ionic strongly basic fluorohydrin functional ionic liquid 1b. .

5. The application of the ionic liquid according to any one of claims 1 to 4, characterized in that, The ionic liquid is used as a catalyst in the CO2 resource recovery and high-value utilization reaction. The aforementioned CO2 resource utilization and high-value-added processes include reactions that prepare cyclic carbonates, carbamates, and quinazoline-2,4(1H,3H)-diones from CO2.

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