Method for preparing 3-(1-ethoxyethyl) oxazolidinone under catalysis of magnetic nanoparticle-loaded acidic ionic liquid

Abstract

The invention belongs to the technical field of organic monomer synthesis, and relates to a method for preparing 3-(1-ethoxyethyl) oxazolidinone under catalysis of magnetic nanoparticle loaded acidic ionic liquid. Magnetic nano-particles are prepared through a coprecipitation method, acidic ionic liquid is prepared from 2-methylimidazole, 3-chloropropyltriethoxysilane and p-toluene sulfonic acid, and the acidic ionic liquid is loaded on the magnetic nano-particles. Oxazolidinone and acetal are used as raw materials, a magnetic nanoparticle loaded acidic ionic liquid is used as a catalyst, after the reaction is finished, the catalyst is filtered out through magnetic suction, and 3-(1-ethoxyethyl) oxazolidinone is obtained through rectification. The magnetic nano-particle loaded acidic ionic liquid is used as the catalyst, is easy to separate, and can be recycled and used for multiple times. The synthesis reaction is mild in condition, simple to operate, low in cost and high in yield.

Description

Technical Field

[0001] The present invention belongs to the technical field of organic monomer synthesis, and relates to a method for catalytically preparing 3-(1-ethoxyethyl)oxazolidinone by using magnetic nanoparticles loaded with acidic ionic liquid. Background Art

[0002] Oxazolidinone is a class of five-membered heterocyclic compounds and has wide applications in organic chemistry, pharmaceuticals and agriculture. N-vinyl oxazolidinone has excellent adhesion properties, especially good adhesion to polyethylene and polypropylene substrates, and has high copolymerization reactivity with acrylate. It is suitable for photocuring printing and coating. It can replace N-vinylcaprolactam or N-vinylpyrrolidone, etc., and can be used as a diluent monomer for ultraviolet curable inkjet printing inks, with characteristics such as high reactivity and low viscosity. As an intermediate for synthesizing N-vinyl oxazolidinone, the synthesis conditions, conversion rate and catalytic activity of the catalyst for 3-(1-ethoxyethyl)oxazolidinone are also what we need to focus on.

[0003] In the process of synthesizing 3-(1-ethoxyethyl)oxazolidinone, an acid catalyst is often required. The traditional synthesis method uses concentrated sulfuric acid as a catalyst. However, this method seriously corrodes equipment, has many reaction by-products, is difficult to separate, recover and reuse the catalyst, and causes relatively serious environmental pollution.

[0004] Ionic liquid (ILs) catalysts have been widely favored due to their wide solution range, low volatility, high catalytic activity, good thermal stability and other advantages. Immobilizing ILs on solid materials to prepare supported ILs can improve the problem of difficult separation and recovery from products. The choice of carrier has a significant impact on the activity, selectivity, reusability, etc. of the catalyst. Magnetic nanoparticles (MNPs) are inexpensive and easy to prepare, and can be applied to various fields. At the same time, coating MNPs with an organic or inorganic substance to form a core-shell structured material can prevent their agglomeration and prevent their destruction. SiO2-coated MNPs (MNPs@SiO2) have low toxicity, inexpensive raw materials, simple preparation methods, the surface structure can be modulated by functionalization, large specific surface area, and good dispersibility in many solvents, and it is a biodegradable green environmental protection type carrier. And the prepared catalyst can be simply separated by an external magnetic field. Summary of the Invention

[0005] The object of the present invention is to provide a method for preparing 3-(1-ethoxyethyl)oxazolidinone by using magnetic nanoparticle-supported acidic ionic liquid as catalyst, in view of the problems of many by-products, difficult separation and recovery, and easy corrosion of pipelines in industrial production in the case of liquid acid catalysis. Specifically, it relates to a technical solution of a catalyst that can be recycled multiple times and has good stability, can be separated from the reaction solution after the reaction, and has mild reaction conditions, few by-products, high catalytic activity, and low preparation cost and production cost.

[0006] The technology adopted in the present invention is as follows: A method for preparing 3-(1-ethoxyethyl)oxazolidinone by using magnetic nanoparticle-supported acidic ionic liquid as catalyst, comprising the following steps: (1) Preparing magnetic nanoparticles by a co-precipitation method; (2) Pour 2-methylimidazole and sodium methoxide into a three-necked flask equipped with magnetic stirring, add methanol, heat to 60 °C and stir for 6 h; under a nitrogen atmosphere, slowly dropwise add 3-chloropropyltriethoxysilane to the reaction solution, and continue stirring for 16 h; filter to remove the reaction by-product sodium chloride; add p-toluenesulfonic acid to the filtrate, heat to 60 °C and react for 16 h, cool the reaction solution to room temperature, place it in an ice-water bath, slowly dropwise add 98% concentrated sulfuric acid with a constant pressure dropping funnel, ultrasonically vibrate for 8 h, then wash with ether, and the reaction equations are shown in Formula I and Formula II; then place it in a vacuum drying oven at 45 °C and dry for 8 h to obtain an acidic ionic liquid.

[0007] Formula I

[0008] Formula II (3) Place the magnetic nanoparticles and the acidic ionic liquid in a three-necked flask, pour in anhydrous toluene, heat under reflux for 8 h under a nitrogen atmosphere to obtain magnetic nanoparticles loaded with acidic ionic liquid, wash with ether 3-5 times, and dry at 45 °C in a vacuum drying oven for 12 h to obtain magnetic nanoparticle-supported acidic ionic liquid. (4) Put oxazolidinone and acetal into a three-necked flask, add magnetic nanoparticle-supported acidic ionic liquid as catalyst, under normal pressure, react at a reaction temperature of 25-50 °C for 4-8 h, after completion, magnetically filter the catalyst, adjust the pH to weakly alkaline (pH = 7-8) with sodium bicarbonate, heat the filtrate to 40 °C and carry out vacuum distillation to distill out excess ethanol and acetal; then heat to 90-110 °C and rectify at a vacuum degree of <100 Pa to obtain 3-(1-ethoxyethyl)oxazolidinone.

[0009] Preferably, in step (2), the molar ratio of 2-methylimidazole, sodium methoxide, 3-chloropropyltriethoxysilane and p-toluenesulfonic acid is 1:1:1:1; the mass-volume ratio of 2-methylimidazole and methanol is 1:10-15, g / mL.

[0010] Preferably, in step (3), the mass ratio of magnetic nanoparticles to acidic ionic liquid is 4:1~3, more preferably 2:1; the mass-volume ratio of magnetic nanoparticles to anhydrous toluene is 1:10-15, g / mL.

[0011] Preferably, in step (4), the molar ratio of oxazolidinone and acetal is 1:1.5~3; more preferably 1:2.

[0012] Preferably, in step (4), the dosage of the magnetic nanoparticle-supported acidic ionic liquid catalyst is 10-20% of the mass of oxazolidinone.

[0013] Preferably, in step (4), after adding the magnetic nanoparticle-supported acidic ionic liquid, the reaction temperature is 45-50 °C.

[0014] The magnetic nanoparticles have the magnetism of Fe3O4, while nano-Fe3O4 has an aggregation tendency and acid corrosion. Coating the magnetic nanoparticles with silica to form a core-shell structure can improve this problem. In addition, the silica shell also provides suitable sites (Si-OH groups) for surface modification, has a large specific surface area, good dispersibility in many solvents, and is a biodegradable and environmentally friendly carrier. The presence of SO3H-functional groups and hydrogen sulfate anions can enhance their acidity. These strongly acidic ILs have been used as effective catalysts for many reactions and usually can provide higher yields and selectivities compared to traditional acid catalysts. And due to the combination of MNP carrier characteristics and flexible imidazole linkers, this catalyst acts as an effective "quasi-homogeneous" catalyst, which can be highly dispersed in the reaction system like a homogeneous system and is as easy to separate and reuse magnetically as a heterogeneous catalyst. During the preparation of 3-(1-ethoxyethyl)oxazolidinone, adjusting the pH to weakly alkaline is to prevent the hydrolysis of acetal under acidic conditions, and the reaction solution is stable under weakly alkaline conditions, which is convenient for recycling acetal.

[0015] Compared with the prior art, the present invention has the following beneficial effects: (1) The present invention uses magnetic nanoparticles supported with acidic ionic liquid as a catalyst, which is easy to separate, can be recycled and reused multiple times.

[0016] (2) In the present invention, magnetic nanoparticles loaded with acidic ionic liquids are used as catalysts, combining the advantages of ionic liquids and magnetic nanoparticles. Compared with liquid acids, they have a high specific surface area and high porosity, which can increase the contact area with the reaction solution, improve the reaction rate, and have high catalytic activity.

[0017] (3) The synthesis reaction of the present invention has mild conditions, simple operation, and low cost. Specific Embodiments

[0018] The present invention will be further described below in conjunction with specific embodiments, and the advantages and features of the present invention will become clearer as the description progresses. However, the embodiments are only exemplary and do not constitute any limitation to the scope of the present invention. Those skilled in the art should understand that modifications or substitutions can be made to the details and forms of the technical solutions of the present invention without departing from the spirit and scope of the present invention, but such modifications and substitutions all fall within the protection scope of the present invention.

[0019] Example 1: A method for catalytically preparing 3-(1-ethoxyethyl)oxazolidinone using magnetic nanoparticles loaded with acidic ionic liquids (1) Magnetic nanoparticles were prepared by the co-precipitation method: 5.4 g of FeCl3·6H2O and 200 ml of ethylene glycol were poured into a 500 ml three-necked flask equipped with magnetic stirring and stirred until dissolved. Then 14.4 g of sodium acetate and 4.0 g of polyethylene glycol were added respectively, and the mixture was stirred rapidly for 1 h. The reaction solution was poured into a polytetrafluoroethylene reaction kettle and reacted at 200 °C for 20 h. After cooling to room temperature, Fe3O4 nanoparticles were obtained by washing with ethanol and a large amount of deionized water. The Fe3O4 nanoparticles were transferred to a 250 mL volumetric flask containing an appropriate amount of ethanol for dispersion; 0.5 g of Fe3O4 nanoparticles, 300 ml of ethanol and water mixed solution (ethanol: water = 5:1) were placed in a beaker and ultrasonically oscillated for 30 min to disperse them evenly. Then magnetic stirring was used, 4 mL of concentrated ammonia water was added dropwise to the mixed solution, and after stirring evenly, 2.5 ml of tetraethyl orthosilicate (TEOS) was added, and stirring was continued for 8 h. After several times of magnetic separation-assisted cleaning, the sample Fe3O4 / SiO2 was dried in an oven at 60 °C.

[0020] (2) Pour 16.42 g of 2-methylimidazole and 14.26 g of sodium methoxide into a three-necked flask equipped with magnetic stirring and containing 200 ml of methanol, heat to 60 °C and stir for 6 h. Under a nitrogen atmosphere, slowly dropwise add 57.79 g of 3-chloropropyltriethoxysilane to the reaction solution drop by drop using a constant pressure dropping funnel, and continue stirring for 16 h. Filter with a Buchner funnel to remove the reaction by-product sodium chloride. Add 41.33 g of p-toluenesulfonic acid to the filtrate, heat to 60 °C and react for 16 h. Cool the reaction solution to room temperature, place it in an ice-water bath, slowly add 20.00 g of 98% concentrated sulfuric acid drop by drop using a constant pressure dropping funnel, ultrasonically vibrate for 8 h, and then wash with ether. Then place it in a vacuum drying oven and dry at 45 °C for 8 h to obtain an acidic ionic liquid.

[0021] (3) Place 20.00 g of magnetic nanoparticles and 10.00 g of acidic ionic liquid in a three-necked flask, pour in 200 ml of anhydrous toluene, under a nitrogen atmosphere, heat to reflux for 10 h, then wash the magnetic nanoparticles loaded with acidic ionic liquid several times with ether, and dry at 45 °C in a vacuum drying oven for 12 h to obtain magnetic nanoparticles loaded with acidic ionic liquid.

[0022] (4) Put 87 g of oxazolidinone and 236 g of acetal into a 500 ml three-necked flask equipped with mechanical stirring, add 10% of the magnetic nanoparticles loaded with acidic ionic liquid catalyst based on the mass fraction of the reaction solution, set the reaction temperature at 50 °C, and react for 4 h. Magnetically separate the magnetic nanoparticles loaded with acidic ionic liquid catalyst from the reaction solution, stir and add sodium bicarbonate to adjust the pH to weakly alkaline. After heating the reaction solution to 40 °C to distill off the excess ethanol and acetal under reduced pressure, raise the temperature to 100 °C for rectification to obtain 3-(1-ethoxyethyl)oxazolidinone. The reaction conversion rate is 80% and the yield is 72%.

[0023] Example 2: A method for catalytically preparing 3-(1-ethoxyethyl)oxazolidinone using magnetic nanoparticles loaded with acidic ionic liquid (1) Prepare magnetic nanoparticles by the co-precipitation method, and the steps are the same as in Example 1.

[0024] (2) Pour 16.42 g of 2-methylimidazole and 14.26 g of sodium methoxide into a three-necked flask equipped with magnetic stirring and containing 200 ml of methanol, heat to 60 °C and stir for 6 h. Under a nitrogen atmosphere, slowly add 57.79 g of 3-chloropropyltriethoxysilane drop by drop using a constant pressure dropping funnel, and continue stirring for 16 h. Filter with a Buchner funnel to remove the reaction by-product sodium chloride. Add 41.33 g of p-toluenesulfonic acid to the filtrate, heat to 60 °C and react for 16 h. Cool the reaction solution to room temperature, place it in an ice-water bath, slowly add 20.00 g of 98% concentrated sulfuric acid drop by drop using a constant pressure dropping funnel, ultrasonically vibrate for 8 h, and then wash with ether. Then place it in a vacuum drying oven at 45 °C and dry for 8 h to obtain an acidic ionic liquid.

[0025] (3) Place 20.00 g of magnetic nanoparticles and 5.00 g of acidic ionic liquid in a three-necked flask, pour in 200 ml of anhydrous toluene, heat under reflux for 10 h under a nitrogen atmosphere, and then wash the magnetic nanoparticles loaded with acidic ionic liquid several times with ether and dry at 45 °C in a vacuum drying oven for 12 h to obtain magnetic nanoparticles loaded with acidic ionic liquid.

[0026] (4) Put 87 g of oxazolidinone and 236 g of acetal into a 500 ml three-necked flask equipped with mechanical stirring, add a magnetic nanoparticle-loaded acidic ionic liquid catalyst with a mass fraction of 10% of the reaction solution, set the reaction temperature at 50 °C, and react for 4 h. Magnetically extract the magnetic nanoparticle-loaded acidic ionic liquid catalyst from the reaction solution, stir and add sodium bicarbonate to adjust the pH to weakly alkaline. After heating the reaction solution to 40 °C to distill off the excess ethanol and acetal under reduced pressure, raise the temperature to 100 °C for rectification to obtain 3-(1-ethoxyethyl)oxazolidinone. The reaction conversion rate is 77% and the yield is 69%.

[0027] Example 3: A method for catalytically preparing 3-(1-ethoxyethyl)oxazolidinone using magnetic nanoparticles loaded with acidic ionic liquid (1) Prepare magnetic nanoparticles by the co-precipitation method, and the steps are the same as in Example 1.

[0028] (2) Pour 16.42 g of 2-methylimidazole and 14.26 g of sodium methoxide into a three-necked flask equipped with magnetic stirring and containing 200 ml of methanol. Heat to 60 °C and stir for 6 h. Under a nitrogen atmosphere, slowly add 57.79 g of 3-chloropropyltriethoxysilane drop by drop using a constant pressure dropping funnel, and continue stirring for 16 h. Filter with a Buchner funnel to remove the reaction by-product sodium chloride. Add 41.33 g of p-toluenesulfonic acid to the filtrate, and heat to 60 °C for reaction for 16 h. Cool the reaction solution to room temperature, place it in an ice-water bath, and slowly add 20.00 g of 98% concentrated sulfuric acid drop by drop using a constant pressure dropping funnel. Ultrasonically vibrate for 8 h, and then wash with ether. Then place it in a vacuum drying oven and dry at 45 °C for 8 h to obtain an acidic ionic liquid.

[0029] (3) Place 20.00 g of magnetic nanoparticles and 10.00 g of acidic ionic liquid in a three-necked flask, pour in 200 ml of anhydrous toluene, and reflux under a nitrogen atmosphere for 10 h. Then wash the magnetic nanoparticles loaded with acidic ionic liquid several times with ether, and dry at 45 °C in a vacuum drying oven for 12 h to obtain magnetic nanoparticles loaded with acidic ionic liquid.

[0030] (4) Put 87 g of oxazolidinone and 236 g of acetal into a 500 ml three-necked flask equipped with mechanical stirring, add a magnetic nanoparticle-loaded acidic ionic liquid catalyst with a mass fraction of 15% of the reaction solution, set the reaction temperature at 50 °C, and react for 4 h. Magnetically extract the magnetic nanoparticle-loaded acidic ionic liquid catalyst from the reaction solution, stir and add sodium bicarbonate to adjust the pH to weakly alkaline. After distilling off the excess ethanol and acetal under reduced pressure by heating the reaction solution to 40 °C, heat to 100 °C for rectification to obtain 3-(1-ethoxyethyl)oxazolidinone. The reaction conversion rate is 98%, and the yield is 95%.

[0031] Example 4: A method for catalytically preparing 3-(1-ethoxyethyl)oxazolidinone using magnetic nanoparticles loaded with acidic ionic liquid (1) Prepare magnetic nanoparticles by the co-precipitation method, and the steps are the same as in Example 1.

[0032] (2) Pour 16.42 g of 2-methylimidazole and 14.26 g of sodium methoxide into a three-necked flask equipped with magnetic stirring and containing 200 ml of methanol. Heat to 60 °C and stir for 6 h. Under a nitrogen atmosphere, slowly add 57.79 g of 3-chloropropyltriethoxysilane drop by drop using a constant pressure dropping funnel, and continue stirring for 16 h. Filter with a Buchner funnel to remove the reaction by-product sodium chloride. Add 41.33 g of p-toluenesulfonic acid to the filtrate, and heat to 60 °C for 16 h. Cool the reaction solution to room temperature, place it in an ice-water bath, and slowly add 20.00 g of 98% sulfuric acid drop by drop using a constant pressure dropping funnel. Ultrasonically vibrate for 8 h, and then wash with ether. Then place it in a vacuum drying oven and dry at 45 °C for 8 h to obtain an acidic ionic liquid.

[0033] (3) Place 20.00 g of magnetic nanoparticles and 10.00 g of acidic ionic liquid in a three-necked flask, pour in 200 ml of anhydrous toluene, and reflux under a nitrogen atmosphere for 10 h. Then wash the magnetic nanoparticles loaded with acidic ionic liquid several times with ether, and dry at 45 °C in a vacuum drying oven for 12 h to obtain magnetic nanoparticles loaded with acidic ionic liquid.

[0034] (4) Put 87 g of oxazolidinone and 236 g of acetal into a 500 ml three-necked flask equipped with mechanical stirring, add a magnetic nanoparticle-loaded acidic ionic liquid catalyst with a mass fraction of 20% of the reaction solution, set the reaction temperature at 50 °C, and react for 4 h. Magnetically separate the magnetic nanoparticle-loaded acidic ionic liquid catalyst from the reaction solution, stir in sodium bicarbonate to adjust the pH to weakly alkaline. After heating the reaction solution to 40 °C to distill off the excess ethanol and acetal under reduced pressure, raise the temperature to 100 °C for rectification to obtain 3-(1-ethoxyethyl)oxazolidinone. The reaction conversion rate is 98% and the yield is 92%.

[0035] Example 5: A method for catalytically preparing 3-(1-ethoxyethyl)oxazolidinone using magnetic nanoparticles loaded with acidic ionic liquid (1) Prepare magnetic nanoparticles by the co-precipitation method, and the steps are the same as in Example 1.

[0036] (2) Pour 16.42 g of 2-methylimidazole and 14.26 g of sodium methoxide into a three-necked flask equipped with magnetic stirring and containing 200 ml of methanol. Heat to 60 °C and stir for 6 h. Under a nitrogen atmosphere, slowly add 57.79 g of 3-chloropropyltriethoxysilane drop by drop using a constant-pressure dropping funnel, and continue stirring for 16 h. Filter with a Buchner funnel to remove the reaction by-product sodium chloride. Add 41.33 g of p-toluenesulfonic acid to the filtrate, and heat to 60 °C for 16 h. Cool the reaction solution to room temperature, place it in an ice-water bath, and slowly add 20.00 g of 98% concentrated sulfuric acid drop by drop using a constant-pressure dropping funnel. Ultrasonically vibrate for 8 h, and then wash with ether. Then place it in a vacuum drying oven at 45 °C for 8 h to obtain an acidic ionic liquid.

[0037] (3) Place 20.00 g of magnetic nanoparticles and 15.00 g of acidic ionic liquid in a three-necked flask, pour in 200 ml of anhydrous toluene, and reflux under a nitrogen atmosphere for 10 h. Then wash the magnetic nanoparticles loaded with acidic ionic liquid several times with ether, and dry at 45 °C in a vacuum drying oven for 12 h to obtain magnetic nanoparticles loaded with acidic ionic liquid.

[0038] (4) Put 87 g of oxazolidinone and 236 g of acetal into a 500 ml three-necked flask equipped with mechanical stirring, add a magnetic nanoparticle-loaded acidic ionic liquid catalyst at 15% of the mass fraction of the reaction solution, set the reaction temperature at 50 °C, and react for 4 h. Magnetically extract the magnetic nanoparticle-loaded acidic ionic liquid catalyst from the reaction solution, stir and add sodium bicarbonate to adjust the pH to weakly alkaline. After heating the reaction solution to 40 °C to distill off the excess ethanol and acetal under reduced pressure, raise the temperature to 100 °C for rectification to obtain 3-(1-ethoxyethyl)oxazolidinone. The reaction conversion rate is 95%, and the yield is 86%.

[0039] Comparative Example 1: Other reaction conditions are the same as in Example 3, and the catalyst is concentrated sulfuric acid at 12% of the mass fraction of the reaction solution. The reaction conversion rate is 77%, and the yield is 60%.

[0040] Comparative Example 2: Other reaction conditions are the same as in Example 3, and the reaction temperature is 20 °C when catalytically synthesizing 3-(1-ethoxyethyl)oxazolidinone. The reaction conversion rate is 60%, and the yield is 55%.

[0041] Comparative Example 3: Other reaction conditions are the same as in Example 3, and the catalyst is a solid acid catalyst sulfonated carbon at 15% of the mass fraction of the reaction solution. For the first use, the reaction conversion rate is 96%, and the yield is 83%.

[0042] The catalysts in Example 3 and Comparative Example 3 were filtered out and reused in multiple cycles under the same conditions. The results are shown in Table 2.

[0043] Comparative Example 4: Preparation of Ionic Liquid Functionalized Magnetic Nanoparticles Mix 5 g of Fe3O4 nanoparticles, 100 mL of ethanol, and 15 mL of ammonia water (25%), stir at 30 °C for 15 min, then add 4 mL of tetraethyl orthosilicate, and react at 30 °C under a nitrogen atmosphere for 6 h; after the reaction, recover the solid with a magnet, wash it with ethanol, and dry it at 45 °C for 12 h to obtain the magnetic nanoparticle precursor. Mix 3 g of the magnetic nanoparticle precursor, 0.6 g of 3-chloropropyltrimethoxysilane, and 15 g of toluene, react at 50 °C under a nitrogen atmosphere for 6 h, naturally cool to room temperature after the reaction, recover the solid with a magnet, wash it twice with toluene and twice with ethanol, and then dry it at 60 °C for 4 h to obtain the magnetic nanoparticle intermediate.

[0044] Other reaction conditions were the same as in Example 3. The catalyst was ionic liquid functionalized magnetic nanoparticles with a mass fraction of 15% in the reaction solution. The reaction conversion rate was 25% and the yield was 19%.

[0045] The product yields and purities of each example and comparative example are shown in Table 1.

[0046] Table 1 Conversion Rates and Yields of Products in Examples and Comparative Examples

[0047] Table 2 Conversion Rates and Yields of Different Catalysts in Example 3 and Comparative Example 3 after Reusing 3 Times

[0048] In Examples 1 - 5, by comparing the ratio of acidic ionic liquid to magnetic nanoparticles in the catalyst preparation and the addition amount of the catalyst, it can be obtained that in Examples 1 and 3, when the ratio of acidic ionic liquid to magnetic nanoparticles is 1:2, the conversion rate is higher when the addition amount of the catalyst is 15%; in Examples 1 and 2, it can be obtained that on the premise of the same addition amount of the catalyst, when the ratio of acidic ionic liquid to magnetic nanoparticles decreases, the conversion rate and yield decrease; in the comparison between Examples 3 and 4, the ratio of acidic ionic liquid to magnetic nanoparticles is the same, and the amount of the catalyst is increased to 20%, and the difference in the conversion rate and yield is not significant. In Example 5, when the ratio of acidic ionic liquid to magnetic nanoparticles is increased and the amount of the catalyst is 15%, the conversion rate and yield are not significantly different from those in Example 3. Therefore, a suitable ratio of acidic ionic liquid to magnetic nanoparticles and the amount of the catalyst can achieve better results.

[0049] In Comparative Example 1, the catalyst was changed to liquid concentrated sulfuric acid. Due to many by-products, an obvious problem of yield decline could be seen. In Comparative Example 2, the reaction temperature was lowered to 25 °C. It could be seen that at the same reaction time, the conversion rate decreased significantly. In Comparative Example 3, the catalyst was different. The conversion rate and yield of the solid acid catalyst were basically the same as those of the magnetic nanoparticle-supported acidic ionic liquid catalyst. However, after being recycled many times, its catalytic activity decreased, and its conversion rate and yield decreased significantly. In Comparative Example 4, the catalyst was changed to ionic liquid-functionalized magnetic nanoparticles, but the catalyst was non-acidic, so both the yield and the conversion rate were not high.

[0050] The magnetic nanoparticle-supported acidic ionic liquid catalyst designed in the present invention has high catalytic activity, and after being recycled many times, the catalytic effect is still remarkable.

Claims

1. A method for preparing 3-(1-ethoxyethyl)oxazolidinone by catalysis of magnetic nanoparticles supported by acidic ionic liquid, characterized in that: The method comprises the following steps: (1) Preparation of magnetic nanoparticles by co-precipitation method; (2) Pour 2-methylimidazole and sodium methoxide into a three-necked flask with a magnetic stirrer, add methanol, heat to 60°C and stir for 6 h; slowly add 3-chloropropyltriethoxysilane dropwise to the reaction solution under a nitrogen atmosphere, and continue to stir for 16 h; filter; add p-toluenesulfonic acid to the filtrate, heat to 60°C and react for 16 h, cool the reaction solution to room temperature, place it in an ice water bath, add 98% concentrated sulfuric acid dropwise using a constant pressure dropping funnel, ultrasonically shake for 8 h, and then wash with ether; then place it in a vacuum drying oven at 45°C and dry for 8 h to obtain an acidic ionic liquid; (3) Place the magnetic nanoparticles and the acidic ionic liquid in a three-necked flask, pour in anhydrous toluene, heat under reflux for 8 h in a nitrogen atmosphere, then wash the magnetic nanoparticles loaded with the acidic ionic liquid with ether for 3-5 times, and dry in a vacuum drying oven at 45°C for 12 h to obtain the magnetic nanoparticles loaded with the acidic ionic liquid; (4) Oxazolidinone and acetal are placed in a three-necked flask, and magnetic nanoparticles loaded with acidic ionic liquid are added as a catalyst. The reaction is carried out at 25-50°C under normal pressure for 4-8 h. After the reaction, the catalyst is magnetically filtered and the pH is adjusted to a weak alkaline state (pH = 7-8) with sodium bicarbonate. The filtrate is heated to 40°C for vacuum distillation, and then heated to 90-110°C and distilled at a vacuum degree of <100 Pa to obtain 3-(1-ethoxyethyl)oxazolidinone.

2. The method according to claim 1, characterized in that In the step (2), the molar ratio of 2-methylimidazole, sodium methoxide, 3-chloropropyltriethoxysilane and p-toluenesulfonic acid is 1:1:1:1; the mass volume ratio of 2-methylimidazole and methanol is 1:10-15, g / mL.

3. The method according to claim 1, characterized in that: In the step (3), the mass ratio of the magnetic nanoparticles to the acidic ionic liquid is 4:1-3.

4. The method according to claim 3, characterized in that In the step (3), the mass ratio of the magnetic nanoparticles to the acidic ionic liquid is 2:

1.

5. The method according to claim 1, characterized in that In the step (3), the mass volume ratio of the magnetic nanoparticles to anhydrous toluene is 1:10-15, g / mL.

6. The method according to claim 1, characterized in that In the step (4), the molar ratio of oxazolidinone to acetal is 1:1.5-3.

7. The method according to claim 6, characterized in that The molar ratio of oxazolidinone to acetal in step (4) is 1:

2.

8. The method according to claim 1, characterized in that In the step (4), the amount of the magnetic nanoparticle-loaded acidic ionic liquid catalyst is 10-20% of the mass of the oxazolidinone.

9. The method according to claim 1, characterized in that: After adding the magnetic nanoparticles loaded with acidic ionic liquid in step (4), the reaction temperature is 45-50°C.

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