阅读说明：本技术 一种使用咪唑鎓盐催化合成恶唑烷酮的方法 (Method for synthesizing oxazolidinone by using imidazolium salt as catalyst ) 是由 郭凯 陈恺 李振江 于 2021-01-13 设计创作，主要内容包括：本发明公开了一种使用咪唑鎓盐催化合成恶唑烷酮的方法,属于有机合成技术领域。本发明采用环氧化物和异氰酸酯为原料,采用本发明所提出的式(I)的催化剂反应得到恶唑烷酮。该方法所用试剂廉价易得,且为一步法即可合成产物,条件温和,高效,且整个反应体系中没有金属残留。(The invention discloses a method for synthesizing oxazolidinone by using imidazolium salt as a catalyst, belonging to the technical field of organic synthesis. The invention adopts epoxide and isocyanate as raw materials, and adopts the catalyst of formula (I) provided by the invention to react to obtain oxazolidinone. The method has the advantages of cheap and easily-obtained reagents, capability of synthesizing the product by a one-step method, mild conditions, high efficiency and no metal residue in the whole reaction system.)

1. A method for synthesizing oxazolidinone by using imidazolium salt catalysis, which is characterized in that: epoxide and isocyanate are taken as raw materials, and the catalyst shown in the formula (I) is adopted for reaction to obtain oxazolidinone and derivatives thereof;

wherein R is₁、R₂Is aryl; x is selected from bromine or iodine;

the preparation route of the oxazolidinone synthesized by the epoxide and the isocyanate is as follows:

wherein R is₃Is monochloromethyl, phenoxymethyl or phenyl; r₄P-methoxyphenyl, 3, 5-bistrifluoromethylphenyl, m-tolyl or p-tolyl.

2. A method for the catalytic synthesis of oxazolidinones using imidazolium salts according to claim 1, characterized in that: x in the formula (I)^-Is composed of

3. A method for the catalytic synthesis of oxazolidinones using imidazolium salts according to claim 1 or 2, characterized in that: the catalyst shown in the formula (I) is selected from the following structures:

4. a method for the catalytic synthesis of oxazolidinones using imidazolium salts according to claim 1, characterized in that: the epoxy substrate is epichlorohydrin, styrene oxide or phenyl glycidyl ether.

5. A method for the catalytic synthesis of oxazolidinones using imidazolium salts according to any of the claims 1 to 4, characterized in that: the molar ratio of the epoxy substrate to the catalyst is 100: 2-5.

6. A method for the catalytic synthesis of oxazolidinones using imidazolium salts according to any of the claims 1 to 4, characterized in that: the synthesis method of the oxazolidinone comprises the following specific steps: epoxide, isocyanate and organic catalyst shown in formula (I) react for 8 hours in solvent at 70-100 ℃, and the product oxazolidinone is obtained by column chromatography of reaction liquid.

7. A method for the catalytic synthesis of oxazolidinones using imidazolium salts according to claim 6, characterized in that: the reaction is carried out at 100 ℃.

Technical Field

The invention belongs to the technical field of organic catalysis, and particularly relates to a method for producing oxazolidinone by using a [3+2] cyclization reaction between epoxide and isocyanate.

Background

Oxazolidinones are five-membered heterocycles containing N and O atoms and can be used as chiral auxiliary in asymmetric syntheses, intermediates and precursors for amino alcohol syntheses and building blocks for polymers, and oxazolidinones themselves have important applications as an emerging pharmacophore in pharmaceutical chemistry. (Eur.J.org.chem.2020, 1881-1895). Among them, N-aryl substituted oxazolidinones are useful as precursors of antibacterial agents against enterococcus Vancomycin (VRE) and methicillin-resistant Staphylococcus aureus (MRSA). (Med. chem. Lett.2008,18, 4868-4871) in addition, oxazolidinones are useful for the synthesis of antipsychotics and antidepressants, and therefore, the development of a simple and efficient method for oxazolidinones has been a major concern. (J.Med.chem.2002,45, 1180-

Up to now, a large number of synthetic oxazolidinones have been reported, such as the cyclization of alpha-amino acids or 1, 2-amino alcohols with carbonyl derivatives, carbamation, Au and Ag catalyzed cyclization of N boropropylalkynylamines and propargyl alcohols, and the [3+2] cyclization of epoxides with isocyanates, the most direct, atom-efficient and economically efficient method being the [3+2] cyclization of epoxides with isocyanates, which can lead to a variety of substituted oxazolidinones by varying the substituents on the epoxides and isocyanates. Oxygen on the epoxide is activated by lewis acid, then lewis base nucleophilically attacks methylene carbon in the epoxide to open the ring, and finally isocyanate is inserted to close the ring to form oxazolidinone. Speranza and Pepple et al, 1958, reported the use of tetrabutylammonium salts to catalyze the synthesis of oxazolidinones from epoxides and isocyanates. (J.org.chem.1958,23,1922). After that, many metal salt catalysts are reported to catalyze the [3+2] cyclization reaction of epoxides with isocyanates, but the reaction conditions are very harsh, high temperature, high loading, excess epoxide, and the isocyanate needs to be added slowly. Recently, the use of metal complex catalysts has been effective in improving the above problems, but when isocyanates are substituted with an electron withdrawing group isocyanate or an alkyl group, the effect is not desirable. (ACS Catal.2013,3,790) and the toxic metal ions remained in the metal ions hinder the application of oxazolidinones in biomedicine.

Recently, organic catalysis has made very important advances in the field of catalysis, which has enabled many reactions to avoid the use of expensive and toxic metal catalysts. Imidazolium salts have been reported as an important organic catalyst in 2018 by Byun et al to use alkyl substituted imidazolium salts to catalyze the fixation of carbon dioxide to form cyclic carbonates. (Chemcathem 2018,10(20),4610-4616) unlike the fixed carbon dioxide mechanism, the difference in the nucleophilic attack sites of the anion leads to the formation of different oxazolidinones (see below) due to the asymmetric hetero-accumulative diene as isocyanate. To date, the use of aryl-substituted imidazolium salts has not been reported.

The invention firstly provides the synthesis of oxazolidinone by catalyzing the cyclization of epoxide and isocyanate by using imidazolium salt. The aryl substituted imidazolium salt catalyst is commercially available, and other preparation methods are reported in a large number (Nature Communications,2018,9, 4251-4261), and the aryl substituted imidazolium salt catalyst is prepared by directly preparing N, N '-substituted diimine from 2, 6-substituted aniline and glyoxal aqueous solution, and then directly preparing the N, N' -substituted diimine, paraformaldehyde and trimethyl halogenated silane, and has the advantages of simple steps and high yield. The product is directly obtained by filtration and washing without column chromatography.

In order to expand the application of oxazolidinones in the field of biomedicine, the invention discovers and solves the problems from the actual requirements, and various substituted oxazolidinones are synthesized by utilizing various imidazolium salts. The catalytic system is firstly proposed and applied to synthesis of oxazolidinone from epoxide and isocyanate.

Disclosure of Invention

The invention aims to provide a method for catalyzing epoxide and isocyanate to generate oxazolidinone based on imidazolium salt. Compared with the existing metal ion or metal complex catalyst, the method can prepare the oxazolidinone by a one-pot method, and has the advantages of no metal residue, high efficiency, mild conditions and the like.

In order to solve the technical problem of the invention, the technical scheme is as follows: a method for synthesizing oxazolidinone by using imidazolium salt as a catalyst comprises the steps of using epoxide and isocyanate as raw materials, and reacting the epoxide and isocyanate by using the catalyst shown in the formula (I) to obtain oxazolidinone and derivatives thereof;

wherein R is₁、R₂Is aryl; x is selected from bromine or iodine;

the preparation route of the oxazolidinone synthesized by the epoxide and the isocyanate is as follows:

wherein R is₃Is monochloromethyl, phenoxymethyl or phenyl; r₄P-methoxyphenyl, 3, 5-bistrifluoromethylphenyl, m-tolyl or p-tolyl.

Preferably, X in said formula (I)^-Is composed ofOr

Preferably, the catalyst represented by the formula (I) is selected from the following structures:

preferably, the epoxy substrate is epichlorohydrin, styrene oxide or phenyl glycidyl ether.

Preferably, the molar ratio of epoxy substrate to catalyst is 100: 2-5.

Preferably, the synthesis method of the oxazolidinone comprises the following specific steps: epoxide, isocyanate and organic catalyst shown in formula (I) react for 8 hours in solvent at 70-100 ℃, and the product oxazolidinone is obtained by column chromatography of reaction liquid.

Preferably, the reaction is carried out at 100 ℃.

Has the advantages that:

(1) the invention can efficiently synthesize oxazolidinones with diversity through the catalytic system, and compared with oxazolidinones synthesized by using a metal catalyst or a metal composite catalyst in the prior art, the invention has the characteristics of high yield, no metal residue, wide application and the like. Has great commercial application potential in biomedicine and fields.

(2) The catalytic system activates epoxide through the action of hydrogen bond at C-2 position in imidazolium salt, and catalyzes the epoxide to cyclize with isocyanate to synthesize oxazolidinone. At present, no report is available on the synthesis of oxazolidinone by catalyzing the cyclization of epoxide and isocyanate by using imidazolium salt. Compared with other methods for synthesizing oxazolidinone by cyclizing epoxide and isocyanate under the conditions of high temperature and high catalyst loading, the method has the advantages of relatively mild reaction conditions and convenience.

(3) The catalysts used in the present invention can be purchased directly or prepared in two simple steps, giving the corresponding oxazolidinones in yields of more than 80% for most epoxides and isocyanates, with reaction times of only 8 hours.

(4) The test is carried out at 70-100 ℃, the yield is increased along with the increase of the reaction temperature, and the high yield of the oxazolidinone can be achieved at 100 ℃. Compared with the high temperature of the metal catalyst, the reaction condition is milder.

Compared with other existing catalytic systems, the catalyst has the obvious advantages of being mild, efficient, easy to prepare, wide in substrate universality, free of metal and the like.

Drawings

Embodiments of the present invention are described in detail below with reference to the attached drawing figures, wherein

FIG. 1: examples 1-7 Hydrogen spectra of oxazolidinones as products

FIG. 2: EXAMPLE 8 Hydrogen spectrum of oxazolidinone product

FIG. 3: EXAMPLE 9 Hydrogen spectrum of oxazolidinone product

FIG. 4: EXAMPLE 10 Hydrogen Spectroscopy of oxazolidinone product

FIG. 5: EXAMPLE 11 Hydrogen spectrum of oxazolidinone product

FIG. 6: example 1 Hydrogen Spectrum of catalyst

FIG. 7: example 2 Hydrogen Spectrum of catalyst

FIG. 8: example 3 Hydrogen Spectrum of catalyst

Detailed Description

The invention is further illustrated by the following examples, which are intended to be illustrative and not limiting. It will be understood by those of ordinary skill in the art that these examples are not intended to limit the present invention in any way and that suitable modifications and data transformations may be made without departing from the spirit of the invention and from the scope of the invention.

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

example 1:

the reaction flask was subjected to three repetitions of drying and oxygen removal, and inert gas was introduced for protection, catalyst (1) (19.22mg, 0.05mmol, 0.05equiv) and phenyl glycidyl ether (0.135mL, 1mmol,1.0 equiv) were added, chlorobenzene solvent (1.0mL) was added, and finally p-methoxyphenyl isocyanate (0.155mL, 1.2mmol, 1.2equiv) was added. The reaction vessel was inserted with a balloon filled with inert gas and placed in an oil bath pan at 100 ℃ for 8 hours. After the reaction was completed, cooling, column chromatography (petroleum ether: ethyl acetate: 5:1) and spin-drying on a rotary evaporator to obtain white powder, which was dried to constant weight with a yield of 57%.¹H NMR(400MHz,Chloroform-d)δ7.51–7.43(m,2H),7.33–7.28(m,2H),7.02–6.98(m,1H),6.94–6.88(m,4H),4.97(dtd,J＝9.0,5.6,4.5Hz,1H),4.24–4.14(m,3H),4.03(dd,J＝8.9,6.0Hz,1H),3.81(s,3H).

Example 2:

the reaction flask was subjected to three repetitions of drying and oxygen removal, and inert gas was introduced for protection, catalyst (2) (21.5mg, 0.05mmol, 0.05equiv) and phenyl glycidyl ether (0.135mL, 1mmol,1.0 equiv) were added, chlorobenzene solvent (1.0mL) was added, and p-methoxyphenyl isocyanate (0.155mL, 1.2 mm) was addedol, 1.2 equiv). The reaction vessel was inserted with a balloon filled with inert gas and placed in an oil bath pan at 100 ℃ for 8 hours. After the reaction was completed, cooling and column chromatography (petroleum ether: dichloromethane ═ 1:1) were performed, followed by spin-drying on a rotary evaporator to obtain a white powder, which was dried to constant weight, with a yield of 86%.¹H NMR(400MHz,Chloroform-d)δ7.51–7.43(m,2H),7.33–7.28(m,2H),7.02–6.98(m,1H),6.94–6.88(m,4H),4.97(dtd,J＝9.0,5.6,4.5Hz,1H),4.24–4.14(m,3H),4.03(dd,J＝8.9,6.0Hz,1H),3.81(s,3H).

Example 3:

the reaction flask was subjected to three repetitions of drying and oxygen removal, and inert gas was introduced for protection, catalyst (3) (27.5mg, 0.05mmol, 0.05equiv) and phenyl glycidyl ether (0.135mL, 1mmol,1.0 equiv) were added, chlorobenzene solvent (1.0mL) was added, and p-methoxyphenyl isocyanate (0.155mL, 1.2mmol, 1.2equiv) was added. The reaction vessel was inserted with a balloon filled with inert gas and placed in an oil bath pan at 100 ℃ for 8 hours. After the reaction was completed, cooling, column chromatography (petroleum ether: ethyl acetate: 5:1) and spin-drying on a rotary evaporator to obtain white powder, which was dried to constant weight with a yield of 53%.¹H NMR(400MHz,Chloroform-d)δ7.51–7.43(m,2H),7.33–7.28(m,2H),7.02–6.98(m,1H),6.94–6.88(m,4H),4.97(dtd,J＝9.0,5.6,4.5Hz,1H),4.24–4.14(m,3H),4.03(dd,J＝8.9,6.0Hz,1H),3.81(s,3H).

Example 4:

the reaction flask was subjected to three repetitions of drying and oxygen removal, and inert gas was introduced for protection, catalyst (2) (21.5mg, 0.05mmol, 0.05equiv) and phenyl glycidyl ether (0.135mL, 1mmol,1.0 equiv) were added, chlorobenzene solvent (1.0mL) was added, and finally p-methoxyphenyl isocyanate (0.155mL, 1.2mmol, 1.2equiv) was added. The reaction vessel was inserted with a balloon filled with inert gas and placed in an oil bath pan at 90 ℃ for 8 hours. After the reaction is finished, cooling, performing column chromatography (petroleum ether: ethyl acetate: 5:1), and performing spin drying on a rotary evaporator to obtain white powder, and drying to constant weight to obtain the yield of 80%.¹H NMR(400MHz,Chloroform-d)δ7.51–7.43(m,2H),7.33–7.28(m,2H),7.02–6.98(m,1H),6.94–6.88(m,4H),4.97(dtd,J＝9.0,5.6,4.5Hz,1H),4.24–4.14(m,3H),4.03(dd,J＝8.9,6.0Hz,1H),3.81(s,3H).

Example 5:

the reaction flask was subjected to three repetitions of drying and oxygen removal, and inert gas was introduced for protection, catalyst (2) (21.5mg, 0.05mmol, 0.05equiv) and phenyl glycidyl ether (0.135mL, 1mmol,1.0 equiv) were added, chlorobenzene solvent (1.0mL) was added, and finally p-methoxyphenyl isocyanate (0.155mL, 1.2mmol, 1.2equiv) was added. The reaction kettle is inserted with a balloon filled with inert gas and put into an oil bath kettle at the temperature of 80 ℃ for reaction for 8 hours. After the reaction was completed, cooling, column chromatography (petroleum ether: ethyl acetate: 5:1) and spin-drying on a rotary evaporator to obtain white powder, which was dried to constant weight, yielding 69%.¹H NMR(400MHz,Chloroform-d)δ7.51–7.43(m,2H),7.33–7.28(m,2H),7.02–6.98(m,1H),6.94–6.88(m,4H),4.97(dtd,J＝9.0,5.6,4.5Hz,1H),4.24–4.14(m,3H),4.03(dd,J＝8.9,6.0Hz,1H),3.81(s,3H).

Example 6:

the reaction flask was subjected to three repetitions of drying and oxygen removal, and inert gas was introduced for protection, catalyst (2) (21.5mg, 0.05mmol, 0.05equiv) and phenyl glycidyl ether (0.135mL, 1mmol,1.0 equiv) were added, chlorobenzene solvent (1.0mL) was added, and finally p-methoxyphenyl isocyanate (0.155mL, 1.2mmol, 1.2equiv) was added. The reaction vessel was inserted with a balloon filled with inert gas and placed in an oil bath pan at 70 ℃ for 8 hours. After the reaction was completed, cooling, column chromatography (petroleum ether: ethyl acetate: 5:1) and spin-drying on a rotary evaporator to obtain white powder, which was dried to constant weight with a yield of 43%.¹H NMR(400MHz,Chloroform-d)δ7.51–7.43(m,2H),7.33–7.28(m,2H),7.02–6.98(m,1H),6.94–6.88(m,4H),4.97(dtd,J＝9.0,5.6,4.5Hz,1H),4.24–4.14(m,3H),4.03(dd,J＝8.9,6.0Hz,1H),3.81(s,3H).

Example 7:

the reaction flask was subjected to three repetitions of drying and oxygen removal, and inert gas was introduced for protection, catalyst (2) (8.6mg, 0.02mmol, 0.02equiv) and phenyl glycidyl ether (0.135mL, 1mmol,1.0 equiv) were added, chlorobenzene solvent (1.0mL) was added, and finally p-methoxyphenyl isocyanate (0.155mL, 1.2mmol, 1.2equiv) was added. Inserting a balloon filled with inert gas, placing at 100 deg.CWas reacted in an oil bath for 8 hours. After the reaction is finished, cooling, performing column chromatography (petroleum ether: ethyl acetate: 5:1), and performing spin drying on a rotary evaporator to obtain white powder which is dried to constant weight, wherein the yield is 40%.¹H NMR(400MHz,Chloroform-d)δ7.51–7.43(m,2H),7.33–7.28(m,2H),7.02–6.98(m,1H),6.94–6.88(m,4H),4.97(dtd,J＝9.0,5.6,4.5Hz,1H),4.24–4.14(m,3H),4.03(dd,J＝8.9,6.0Hz,1H),3.81(s,3H).

Example 8:

the reaction flask was subjected to three repetitions of drying and oxygen removal, and inert gas was purged, and catalyst (2) (21.5mg, 0.05mmol, 0.05equiv) and epichlorohydrin (0.08mL, 1mmol,1.0 equiv) were added, chlorobenzene solvent (1.0mL) was added, and finally m-tolyl isocyanate (0.151mL, 1.2mmol, 1.2equiv) was added. The reaction vessel was inserted with a balloon filled with inert gas and placed in an oil bath pan at 100 ℃ for 8 hours. After the reaction is finished, cooling, performing column chromatography (petroleum ether: ethyl acetate: 5:1), and performing spin drying on a rotary evaporator to obtain white powder, drying to constant weight, wherein the yield is 92%¹H NMR(400MHz,Chloroform-d)δ7.39(d,J＝2.0Hz,1H),7.35–7.26(m,2H),6.98(d,J＝7.3Hz,1H),4.86(dddd,J＝8.7,6.8,5.6,4.1Hz,1H),4.16(t,J＝9.0Hz,1H),3.96(dd,J＝9.2,5.7Hz,1H),3.77(qd,J＝11.6,5.4Hz,2H),2.38(s,3H).

Example 9:

the reaction flask was subjected to three repetitions of drying and oxygen removal, and inert gas was introduced for protection, catalyst (2) (21.5mg, 0.05mmol, 0.05equiv) and phenyl glycidyl ether (0.135mL, 1mmol,1.0 equiv) were added, chlorobenzene solvent (1.0mL) was added, and 3, 5-bistrifluoromethylphenyl isocyanate (0.21mL, 1.2mmol, 1.2equiv) was added last. The reaction vessel was inserted with a balloon filled with inert gas and placed in an oil bath pan at 100 ℃ for 8 hours. After the reaction is finished, cooling, performing column chromatography (petroleum ether: ethyl acetate: 4:1), and performing spin drying on a rotary evaporator to obtain white powder, drying to constant weight, wherein the yield is 80%¹H NMR(400MHz,Chloroform-d)δ8.08(d,J＝1.6Hz,2H),7.70–7.62(m,1H),7.37–7.27(m,2H),7.08–6.96(m,1H),6.95–6.86(m,2H),5.13–4.99(m,1H),4.36–4.21(m,3H),4.17(dd,J＝8.7,5.9Hz,1H).

Example 10:

the reaction flask was subjected to three repetitions of drying and oxygen removal, and inert gas was purged, and catalyst (2) (21.5mg, 0.05mmol, 0.05equiv) and phenyl glycidyl ether (0.135mL, 1mmol,1.0 equiv) were added, chlorobenzene solvent (1.0mL) was added, and finally m-tolyl isocyanate (0.151mL, 1.2mmol, 1.2equiv) was added. The reaction vessel was inserted with a balloon filled with inert gas and placed in an oil bath pan at 100 ℃ for 8 hours. After the reaction is finished, cooling, performing column chromatography (petroleum ether: ethyl acetate: 5:1), and performing spin drying on a rotary evaporator to obtain white powder, drying to constant weight, wherein the yield is 80%¹H NMR(400MHz,Chloroform-d)δ7.42(m,J＝1.5Hz,1H),7.32(d,4H),7.00–6.92(m,4H),4.98(m,1H),4.30–4.22(dd,3H),4.17(dd,J＝8.8,5.9Hz,1H).

Example 11:

the reaction flask was subjected to three repetitions of drying and oxygen removal, under inert gas blanketing, catalyst (2) (21.5mg, 0.05mmol, 0.05equiv) and styrene oxide (0.114mL, 1mmol,1.0 equiv) were added, chlorobenzene solvent (1.0mL) was added, and p-tolyl isocyanate (0.151mL, 1.2mmol, 1.2equiv) was added. The reaction vessel was inserted with a balloon filled with inert gas and placed in an oil bath pan at 100 ℃ for 8 hours. After the reaction was completed, cooling, column chromatography (petroleum ether: ethyl acetate: 5:1) and spin-drying on a rotary evaporator to obtain white powder, which was dried to constant weight with a yield of 81%.¹H NMR(400MHz,Chloroform-d)δ7.57–7.34(m,7H),7.21–7.15(m,2H),5.63(dd,J＝8.7,7.5Hz,1H),4.36(t,J＝8.8Hz,1H),3.94(dd,J＝9.0,7.5Hz,1H),2.33(s,3H).

Example 12

To the commercially available 1, 3- (2, 4, 6-trimethylphenyl) imidazolium chloride (0.340g,1mmol,1.00equiv.) was added 5mL of ethyl acetate to form a suspension, a saturated acetone solution of NaI (0.6g,4mmol,4.00equiv.) was added to the aqueous solution, stirred at room temperature for 12 hours, filtered, and the residue was washed with a small amount of acetone and ethyl acetate to obtain a pure product of the catalyst (2).¹H NMR(400MHz,Chloroform-d)δ10.32(s,1H),7.68(s,76H),7.39(s,1H),7.24(s,2H),2.23(s,12H).

Comparative example 1:

the reaction flask was subjected to three repetitions of drying and oxygen removal, and inert gas was introduced for protection, 1, 3- (2, 4, 6-trimethylphenyl) imidazolium chloride (17.00mg, 0.05mmol, 0.05equiv) and phenyl glycidyl ether (0.135mL, 1mmol,1.0 equiv) were added, chlorobenzene solvent (1.0mL) was added, and p-methoxyphenyl isocyanate (0.155mL, 1.2mmol, 1.2equiv) was added. The reaction vessel was inserted with a balloon filled with inert gas and placed in an oil bath pan at 100 ℃ for 8 hours. After the reaction is finished, cooling, performing column chromatography (petroleum ether: ethyl acetate: 5:1), and performing spin drying on a rotary evaporator to obtain white powder which is dried to constant weight, wherein the yield is 6%. It is proved that in the catalytic system, the effect of the chloride ion is far less than that of the iodide ion and the bromide ion.

Comparative example 2:

the reaction flask was subjected to three repetitions of drying and oxygen removal, and inert gas was introduced for protection, and 1-methyl-3-ethylimidazolium iodide (17.00mg, 0.05mmol, 0.05equiv) and phenyl glycidyl ether (0.135mL, 1mmol,1.0 equiv) were added, chlorobenzene solvent (1.0mL) was added, and finally p-methoxyphenyl isocyanate (0.155mL, 1.2mmol, 1.2equiv) was added. The reaction vessel was inserted with a balloon filled with inert gas and placed in an oil bath pan at 100 ℃ for 8 hours. After the reaction was completed, cooling, column chromatography (petroleum ether: ethyl acetate: 5:1) and spin-drying on a rotary evaporator to obtain white powder, which was dried to constant weight with a yield of 34%. The aryl substituted imidazolium effect is proved to be far higher than that of alkyl substituted imidazolium.

The invention is not limited to the specific technical solutions described in the above embodiments, and all technical solutions formed by equivalent substitutions are within the scope of the invention as claimed.