A method for preparing 3-(1-ethoxyethyl)oxazolidinone using magnetic nanoparticles supported by an acidic ionic liquid catalyst.

Abstract

This invention belongs to the field of organic monomer synthesis technology, and relates to a method for preparing 3-(1-ethoxyethyl)oxazolidinone using magnetic nanoparticles supported by an acidic ionic liquid catalyst. The invention prepares magnetic nanoparticles via a co-precipitation method, uses 2-methylimidazolium, 3-chloropropyltriethoxysilane, and p-toluenesulfonic acid to prepare an acidic ionic liquid, and then loads the acidic ionic liquid onto the magnetic nanoparticles. Oxazolidinone and acetal are used as raw materials, and the magnetic nanoparticles supporting the acidic ionic liquid serve as the catalyst. After the reaction, the catalyst is magnetically filtered out, and 3-(1-ethoxyethyl)oxazolidinone is obtained by distillation. This invention uses magnetic nanoparticles supported by an acidic ionic liquid as the catalyst, which is easy to separate and can be recycled and reused multiple times. The synthesis reaction conditions of this invention are mild, the operation is simple, the cost is low, and the yield is high.

Description

Technical Field

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

[0002] Oxazolidinones are a class of five-membered heterocyclic compounds with wide applications in organic chemistry, pharmaceuticals, and agriculture. N-vinyloxazolidinones exhibit excellent adhesion properties, particularly to polyethylene and polypropylene substrates, and show high copolymerization reactivity with acrylates. They are suitable for UV-curing printing and coating. They can replace N-vinylcaprolactam or N-vinylpyrrolidone and can be used as a diluent monomer for UV-curing inkjet printing inks, exhibiting high reactivity and low viscosity. As an intermediate in the synthesis of N-vinyloxazolidinones, the mild conditions, conversion rate, and catalytic activity of the catalyst in the synthesis of 3-(1-ethoxyethyl)oxazolidinone are also important considerations.

[0003] The synthesis of 3-(1-ethoxyethyl)oxazolidinone often requires the participation of an acid catalyst. The traditional synthesis method is to use concentrated sulfuric acid as a catalyst. However, this method causes severe corrosion to equipment, produces many byproducts, makes it difficult to separate, recover and reuse the catalyst, and causes serious environmental pollution.

[0004] Ionic liquid (IL) catalysts are widely favored due to their wide solution range, low volatility, high catalytic activity, and good thermal stability. Immobilizing ILs on solid materials to prepare supported ILs can improve the difficulty of separation and recovery from products. The choice of support significantly affects the catalyst's activity, selectivity, and reusability. Magnetic nanoparticles (MNPs) are inexpensive to produce, simple to prepare, and applicable to various fields. Encapsulating MNPs with an organic or inorganic layer to form a core-shell structure prevents aggregation and degradation. SiO2-encapsulated MNPs (MNPs@SiO2) are low in toxicity, inexpensive to produce, simple to prepare, and their surface structure can be modulated through functionalization. They have a large specific surface area, good dispersibility in many solvents, and are a biodegradable, environmentally friendly support. Furthermore, the prepared catalysts can be easily separated using an external magnetic field. Summary of the Invention

[0005] The purpose of this invention is to provide a method for preparing 3-(1-ethoxyethyl)oxazolidinone using magnetic nanoparticles supported by an acidic ionic liquid catalyst, addressing the problems of numerous byproducts, difficulty in separation and recovery, and easy corrosion of pipelines during industrial production caused by liquid acid catalysis. Specifically, it relates to a technical solution for a recyclable and reusable catalyst with good stability, capable of separation from the reaction liquid after the reaction, and characterized by mild reaction conditions, few byproducts, high catalytic activity, and low preparation and production costs.

[0006] The technology used in this invention is as follows:

[0007] A method for preparing 3-(1-ethoxyethyl)oxazolidinone using magnetic nanoparticles supported by an acidic ionic liquid catalyst includes the following steps:

[0008] (1) Magnetic nanoparticles were prepared by coprecipitation method;

[0009] (2) 2-Methylimidazole and sodium methoxide were poured into a three-necked flask with a magnetic stirrer, methanol was added, and the mixture was heated to 60°C and stirred for 6 h. 3-Chloropropyltriethoxysilane was slowly added dropwise to the reaction solution under a nitrogen atmosphere and the mixture was stirred for 16 h. Sodium chloride, a byproduct of the reaction, was removed by filtration. p-Toluenesulfonic acid was added to the filtrate and the mixture was heated to 60°C and stirred for 16 h. The reaction solution was cooled to room temperature and placed in an ice-water bath. 98% concentrated sulfuric acid was added dropwise using a constant pressure dropping funnel and the mixture was sonicated for 8 h. The solution was then washed with ether. The reaction equations are shown in Formula I and Formula II. The solution was then dried in a vacuum drying oven at 45°C for 8 h to obtain an acidic ionic liquid.

[0010]

[0011] Formula I

[0012]

[0013] Formula II

[0014] (3) Place the magnetic nanoparticles and acidic ionic liquid in a three-necked flask, pour in anhydrous toluene, and heat under reflux for 8 h in a nitrogen atmosphere to obtain magnetic nanoparticles loaded with acidic ionic liquid. Wash with ether 3-5 times and dry in a vacuum drying oven at 45°C for 12 h to obtain magnetic nanoparticles loaded with acidic ionic liquid.

[0015] (4) Add oxazolidinone and acetal to a three-necked flask, add magnetic nanoparticle-supported acidic ionic liquid as a catalyst, react at atmospheric pressure and temperature of 25-50℃ for 4-8 h. After the reaction, filter the catalyst by magnetic adsorption, adjust the pH to weakly alkaline (pH=7-8) with sodium bicarbonate, heat the filtrate to 40℃ and distill under reduced pressure to remove excess ethanol and acetal; then heat to 90-110℃ and distill under vacuum of <100pa to obtain 3-(1-ethoxyethyl)oxazolidinone.

[0016] 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.

[0017] 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.

[0018] Preferably, the molar ratio of oxazolidinone to acetal in step (4) is 1:1.5~3; more preferably 1:2.

[0019] Preferably, in step (4), the amount of magnetic nanoparticle-supported acidic ionic liquid catalyst used is 10-20% of the mass of oxazolidinone.

[0020] Preferably, after adding the magnetic nanoparticles loaded with the acidic ionic liquid in step (4), the reaction temperature is 45-50℃.

[0021] Magnetic nanoparticles possess Fe3O4 magnetism, but nano-Fe3O4 exhibits a tendency to aggregate and is acid-corrosive. Encapsulating the magnetic nanoparticles with silica to form a core-shell structure can mitigate this problem. Furthermore, the silica shell provides suitable sites (Si-OH groups) for surface modification, resulting in a large specific surface area, good dispersibility in many solvents, and a biodegradable, environmentally friendly support. The presence of SO3H- functional groups and hydrogen sulfate anions enhances their acidity. These strongly acidic ILs have been used as effective catalysts for many reactions, typically offering higher yields and selectivity compared to conventional acid catalysts. Moreover, due to the combination of MNP support characteristics and flexible imidazole linkages, this catalyst acts as an effective "quasi-homogeneous" catalyst, highly dispersed in the reaction system like a homogeneous system, and easily separated and reused like a heterogeneous catalyst. In the preparation of 3-(1-ethoxyethyl)oxazolidinone, adjusting the pH to weakly alkaline prevents the hydrolysis of acetal under acidic conditions, and the reaction solution is stable under weakly alkaline conditions, facilitating the recovery of acetal.

[0022] Compared with the prior art, the present invention has the following beneficial effects:

[0023] (1) The present invention uses magnetic nanoparticles loaded with acidic ionic liquid as a catalyst, which is easy to separate and can be recycled and reused multiple times.

[0024] (2) The present invention uses magnetic nanoparticles loaded with acidic ionic liquid as a catalyst, which combines the advantages of ionic liquid and magnetic nanoparticle. Compared with liquid acid, it has a high specific surface area and high porosity, which can increase the contact area with the reaction liquid, increase the reaction rate, and has high catalytic activity.

[0025] (3) The synthesis reaction conditions of the present invention are mild, the operation is simple and the cost is low. Detailed Implementation

[0026] The present invention will be further described below with reference to specific embodiments, and the advantages and features of the present invention will become clearer with the description. However, the embodiments are merely exemplary and do not constitute any limitation on the scope of the present invention. Those skilled in the art should understand that modifications or substitutions can be made to the details and form of the technical solutions of the present invention without departing from the spirit and scope of the present invention, but all such modifications and substitutions fall within the protection scope of the present invention.

[0027] Example 1:

[0028] A method for preparing 3-(1-ethoxyethyl)oxazolidinone using magnetic nanoparticles supported by an acidic ionic liquid catalyst.

[0029] (1) Preparation of magnetic nanoparticles by coprecipitation method: 5.4 g FeCl3·6H2O and 200 ml ethylene glycol were poured into a 500 ml three-necked flask equipped with a magnetic stirrer and stirred until dissolved. Then, 14.4 g sodium acetate and 4.0 g polyethylene glycol were added and stirred rapidly for 1 h. The reaction solution was poured into a polytetrafluoroethylene reactor 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 Fe3O4 nanoparticles and 300 ml of a mixture of ethanol and water (ethanol:water = 5:1) were placed in a beaker and ultrasonically vibrated for 30 min to disperse them evenly. Magnetic stirring was then used, and 4 mL of concentrated ammonia was added dropwise to the mixture. After stirring evenly, 2.5 ml of tetraethyl orthosilicate (TEOS) was added and stirred continuously for 8 h. After several magnetic separation-assisted cleanings, the sample Fe3O4 / SiO2 was obtained by drying in an oven at 60℃.

[0030] (2) 16.42 g of 2-methylimidazole and 14.26 g of sodium methoxide were poured into a three-necked flask with a magnetic stirrer containing 200 ml of methanol and heated to 60 °C with stirring for 6 h. Under a nitrogen atmosphere, 57.79 g of 3-chloropropyltriethoxysilane was slowly added dropwise using a constant-pressure dropping funnel, and the reaction was continued with stirring for 16 h. The filtrate was filtered through a Buchner funnel to remove the reaction byproduct sodium chloride. 41.33 g of p-toluenesulfonic acid was added to the filtrate and the mixture was heated to 60 °C for 16 h. The reaction solution was cooled to room temperature and placed in an ice-water bath. 20.00 g of 98% concentrated sulfuric acid was added dropwise using a constant-pressure dropping funnel, and the mixture was sonicated for 8 h. The solution was then washed with ether. The solution was then dried in a vacuum drying oven at 45 °C for 8 h to obtain an acidic ionic liquid.

[0031] (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, heat under nitrogen atmosphere and reflux for 10 h, then wash the magnetic nanoparticles loaded with acidic ionic liquid several times with diethyl ether, and dry in a vacuum drying oven at 45 °C for 12 h to obtain magnetic nanoparticles loaded with acidic ionic liquid.

[0032] (4) 87g of oxazolidinone and 236g of acetal were added to a 500ml three-necked flask equipped with a mechanical stirrer. 10% (w / w) of a magnetic nanoparticle-supported acidic ionic liquid catalyst was added to the reaction solution. The reaction temperature was set at 50℃, and the reaction was carried out for 4 h. The magnetic nanoparticle-supported acidic ionic liquid catalyst was magnetically removed from the reaction solution, and sodium bicarbonate was added to adjust the pH to a slightly alkaline state. The reaction solution was heated to 40℃ and distilled off excess ethanol and acetal under reduced pressure. Then, the solution was heated to 100℃ and distilled to obtain 3-(1-ethoxyethyl)oxazolidinone. The conversion rate was 80%, and the yield was 72%.

[0033] Example 2:

[0034] A method for preparing 3-(1-ethoxyethyl)oxazolidinone using magnetic nanoparticles supported by an acidic ionic liquid catalyst.

[0035] (1) Magnetic nanoparticles were prepared by coprecipitation method, with the same steps as in Example 1.

[0036] (2) 16.42 g of 2-methylimidazole and 14.26 g of sodium methoxide were poured into a three-necked flask with a magnetic stirrer containing 200 ml of methanol and heated to 60 °C with stirring for 6 h. Under a nitrogen atmosphere, 57.79 g of 3-chloropropyltriethoxysilane was slowly added dropwise using a constant-pressure dropping funnel, and the reaction was continued with stirring for 16 h. The filtrate was filtered through a Buchner funnel to remove the reaction byproduct sodium chloride. 41.33 g of p-toluenesulfonic acid was added to the filtrate and the mixture was heated to 60 °C for 16 h. The reaction solution was cooled to room temperature and placed in an ice-water bath. 20.00 g of 98% concentrated sulfuric acid was added dropwise using a constant-pressure dropping funnel, and the mixture was sonicated for 8 h. The solution was then washed with ether. The solution was then dried 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 5.00 g of acidic ionic liquid in a three-necked flask, pour in 200 ml of anhydrous toluene, heat under nitrogen atmosphere and reflux for 10 h, then wash the magnetic nanoparticles loaded with acidic ionic liquid several times with diethyl ether, and dry in a vacuum drying oven at 45 °C for 12 h to obtain magnetic nanoparticles loaded with acidic ionic liquid.

[0038] (4) 87g of oxazolidinone and 236g of acetal were added to a 500ml three-necked flask equipped with a mechanical stirrer. 10% (w / w) of a magnetic nanoparticle-supported acidic ionic liquid catalyst was added to the reaction solution. The reaction temperature was set at 50℃, and the reaction was carried out for 4 h. The magnetic nanoparticle-supported acidic ionic liquid catalyst was magnetically removed from the reaction solution, and sodium bicarbonate was added to adjust the pH to weakly alkaline. The reaction solution was heated to 40℃ and distilled off excess ethanol and acetal under reduced pressure. Then, the solution was heated to 100℃ and distilled to obtain 3-(1-ethoxyethyl)oxazolidinone. The conversion rate was 77%, and the yield was 69%.

[0039] Example 3:

[0040] A method for preparing 3-(1-ethoxyethyl)oxazolidinone using magnetic nanoparticles supported by an acidic ionic liquid catalyst.

[0041] (1) Magnetic nanoparticles were prepared by coprecipitation method, with the same steps as in Example 1.

[0042] (2) 16.42 g of 2-methylimidazole and 14.26 g of sodium methoxide were poured into a three-necked flask with a magnetic stirrer containing 200 ml of methanol and heated to 60 °C with stirring for 6 h. Under a nitrogen atmosphere, 57.79 g of 3-chloropropyltriethoxysilane was slowly added dropwise using a constant-pressure dropping funnel, and the reaction was continued with stirring for 16 h. The filtrate was filtered through a Buchner funnel to remove the reaction byproduct sodium chloride. 41.33 g of p-toluenesulfonic acid was added to the filtrate and the mixture was heated to 60 °C for 16 h. The reaction solution was cooled to room temperature and placed in an ice-water bath. 20.00 g of 98% concentrated sulfuric acid was added dropwise using a constant-pressure dropping funnel, and the mixture was sonicated for 8 h. The solution was then washed with ether. The solution was then dried in a vacuum drying oven at 45 °C for 8 h to obtain an acidic ionic liquid.

[0043] (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, heat under nitrogen atmosphere and reflux for 10 h, then wash the magnetic nanoparticles loaded with acidic ionic liquid several times with diethyl ether, and dry in a vacuum drying oven at 45 °C for 12 h to obtain magnetic nanoparticles loaded with acidic ionic liquid.

[0044] (4) 87g of oxazolidinone and 236g of acetal were added to a 500ml three-necked flask equipped with a mechanical stirrer. 15% (w / w) of a magnetic nanoparticle-supported acidic ionic liquid catalyst was added to the reaction solution. The reaction temperature was set at 50℃, and the reaction was carried out for 4 h. The magnetic nanoparticle-supported acidic ionic liquid catalyst was magnetically removed from the reaction solution, and sodium bicarbonate was added to adjust the pH to weakly alkaline. The reaction solution was heated to 40℃ and distilled off excess ethanol and acetal under reduced pressure. Then, the solution was heated to 100℃ and distilled to obtain 3-(1-ethoxyethyl)oxazolidinone. The conversion rate was 98%, and the yield was 95%.

[0045] Example 4:

[0046] A method for preparing 3-(1-ethoxyethyl)oxazolidinone using magnetic nanoparticles supported by an acidic ionic liquid catalyst.

[0047] (1) Magnetic nanoparticles were prepared by coprecipitation method, with the same steps as in Example 1.

[0048] (2) 16.42 g of 2-methylimidazole and 14.26 g of sodium methoxide were poured into a three-necked flask with a magnetic stirrer containing 200 ml of methanol and heated to 60 °C with stirring for 6 h. Under a nitrogen atmosphere, 57.79 g of 3-chloropropyltriethoxysilane was slowly added dropwise using a constant-pressure dropping funnel, and the reaction was continued with stirring for 16 h. The filtrate was filtered through a Buchner funnel to remove the reaction byproduct sodium chloride. 41.33 g of p-toluenesulfonic acid was added to the filtrate and the mixture was heated to 60 °C for 16 h. The reaction solution was cooled to room temperature and placed in an ice-water bath. 20.00 g of 98% concentrated sulfuric acid was added dropwise using a constant-pressure dropping funnel, and the mixture was sonicated for 8 h. The solution was then washed with ether. The solution was then dried in a vacuum drying oven at 45 °C for 8 h to obtain an acidic ionic liquid.

[0049] (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, heat under nitrogen atmosphere and reflux for 10 h, then wash the magnetic nanoparticles loaded with acidic ionic liquid several times with diethyl ether, and dry in a vacuum drying oven at 45 °C for 12 h to obtain magnetic nanoparticles loaded with acidic ionic liquid.

[0050] (4) 87g of oxazolidinone and 236g of acetal were added to a 500ml three-necked flask equipped with a mechanical stirrer. 20% (w / w) of a magnetic nanoparticle-supported acidic ionic liquid catalyst was added to the reaction solution. The reaction temperature was set at 50℃, and the reaction was carried out for 4 h. The magnetic nanoparticle-supported acidic ionic liquid catalyst was magnetically removed from the reaction solution, and sodium bicarbonate was added to adjust the pH to weakly alkaline. The reaction solution was heated to 40℃ and distilled off excess ethanol and acetal under reduced pressure. Then, the solution was heated to 100℃ and distilled to obtain 3-(1-ethoxyethyl)oxazolidinone. The conversion rate was 98%, and the yield was 92%.

[0051] Example 5:

[0052] A method for preparing 3-(1-ethoxyethyl)oxazolidinone using magnetic nanoparticles supported by an acidic ionic liquid catalyst.

[0053] (1) Magnetic nanoparticles were prepared by coprecipitation method, with the same steps as in Example 1.

[0054] (2) 16.42 g of 2-methylimidazole and 14.26 g of sodium methoxide were poured into a three-necked flask with a magnetic stirrer containing 200 ml of methanol and heated to 60 °C with stirring for 6 h. Under a nitrogen atmosphere, 57.79 g of 3-chloropropyltriethoxysilane was slowly added dropwise using a constant-pressure dropping funnel, and the reaction was continued with stirring for 16 h. The filtrate was filtered through a Buchner funnel to remove the reaction byproduct sodium chloride. 41.33 g of p-toluenesulfonic acid was added to the filtrate and the mixture was heated to 60 °C for 16 h. The reaction solution was cooled to room temperature and placed in an ice-water bath. 20.00 g of 98% concentrated sulfuric acid was added dropwise using a constant-pressure dropping funnel, and the mixture was sonicated for 8 h. The solution was then washed with ether. The solution was then dried in a vacuum drying oven at 45 °C for 8 h to obtain an acidic ionic liquid.

[0055] (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, heat under nitrogen atmosphere and reflux for 10 h, then wash the magnetic nanoparticles loaded with acidic ionic liquid several times with diethyl ether, and dry in a vacuum drying oven at 45 °C for 12 h to obtain magnetic nanoparticles loaded with acidic ionic liquid.

[0056] (4) 87g of oxazolidinone and 236g of acetal were added to a 500ml three-necked flask equipped with a mechanical stirrer. 15% (w / w) of a magnetic nanoparticle-supported acidic ionic liquid catalyst was added to the reaction solution. The reaction temperature was set at 50℃, and the reaction was carried out for 4 h. The magnetic nanoparticle-supported acidic ionic liquid catalyst was magnetically removed from the reaction solution, and sodium bicarbonate was added to adjust the pH to weakly alkaline. The reaction solution was heated to 40℃ and distilled off excess ethanol and acetal under reduced pressure. Then, the solution was heated to 100℃ and distilled to obtain 3-(1-ethoxyethyl)oxazolidinone. The conversion rate was 95%, and the yield was 86%.

[0057] Comparative Example 1:

[0058] Other reaction conditions were the same as in Example 3, with the catalyst being 12% concentrated sulfuric acid by mass of the reaction solution. The conversion rate was 77%, and the yield was 60%.

[0059] Comparative Example 2:

[0060] Other reaction conditions were the same as in Example 3, with a reaction temperature of 20°C for the catalytic synthesis of 3-(1-ethoxyethyl)oxazolidinone. The conversion rate was 60%, and the yield was 55%.

[0061] Comparative Example 3:

[0062] Other reaction conditions were the same as in Example 3, with the catalyst being 15% by mass of a solid acid catalyst, sulfonated carbon. On first use, the conversion rate was 96%, and the yield was 83%.

[0063] The catalysts from Example 3 and Comparative Example 3 were filtered out and recycled multiple times under the same conditions. The results are shown in Table 2.

[0064] Comparative Example 4:

[0065] Preparation of ionic liquid functionalized magnetic nanoparticles

[0066] 5g of Fe3O4 nanoparticles, 100mL of ethanol and 15mL of ammonia (25%) were mixed and stirred at 30℃ for 15min. Then 4mL of tetraethyl silicate was added and the mixture was reacted at 30℃ for 6h under a nitrogen atmosphere. After the reaction was completed, the solid was recovered with a magnet, washed with ethanol and dried at 45℃ for 12h to obtain the magnetic nanoparticle precursor.

[0067] 3g of magnetic nanoparticle precursor, 0.6g of 3-chloropropyltrimethoxysilane and 15g of toluene were mixed and reacted at 50°C for 6h under a nitrogen atmosphere. After the reaction was completed, the mixture was naturally cooled to room temperature, and the solid was recovered using a magnet. The solid was washed twice with toluene and twice with ethanol, and then dried at 60°C for 4h to obtain the magnetic nanoparticle intermediate.

[0068] Other reaction conditions are as in Example 3, the catalyst is 15% by mass of ionic liquid functionalized magnetic nanoparticles in the reaction solution, the reaction conversion rate is 25%, and the yield is 19%.

[0069] The product yields and purities of each embodiment and comparative example are shown in Table 1.

[0070] Table 1. Conversion rates and yields of the examples and comparative products.

[0071]

[0072] Table 2. Conversion and yield of different catalysts in Example 3 and Comparative Example 3 after 3 cycles.

[0073]

[0074] Through comparisons of the ratio of acidic ionic liquid to magnetic nanoparticles and the amount of catalyst added in Examples 1-5, it was found that in Examples 1 and 3, when the ratio of acidic ionic liquid to magnetic nanoparticles was 1:2, the conversion rate was higher when the catalyst addition was 15%. In Examples 1 and 2, it was found that when the ratio of acidic ionic liquid to magnetic nanoparticles decreased under the premise of the same catalyst addition, the conversion rate and yield decreased. In the comparison of Examples 3 and 4, when the ratio of acidic ionic liquid to magnetic nanoparticles was the same, and the amount of catalyst was increased to 20%, the conversion rate and yield were not significantly different. In Example 5, when the ratio of acidic ionic liquid to magnetic nanoparticles was increased and the catalyst addition was 15%, the conversion rate and yield were not significantly different from those in Example 3. Therefore, a suitable ratio of acidic ionic liquid to magnetic nanoparticles and a suitable amount of catalyst can achieve better results.

[0075] In Comparative Example 1, when the catalyst was changed to liquid concentrated sulfuric acid, a significant decrease in yield was observed due to the large amount of byproducts. In Comparative Example 2, the reaction temperature was lowered to 25°C, and the conversion rate decreased significantly within the same reaction time. In Comparative Example 3, the catalyst was different; the conversion rate and yield of the solid acid catalyst were basically consistent with those of the magnetic nanoparticle-supported acidic ionic liquid catalyst. However, after multiple cycles, its catalytic activity decreased, and its conversion rate and yield dropped sharply. In Comparative Example 4, the catalyst was changed to ionic liquid functionalized magnetic nanoparticles, but since the catalyst was non-acidic, both the yield and conversion rate were not high.

[0076] The magnetic nanoparticle-supported acidic ionic liquid catalyst designed in this invention exhibits high catalytic activity, and its catalytic effect remains significant even after multiple cycles.

Claims

1. A method for preparing 3-(1-ethoxyethyl)oxazolidinone using magnetic nanoparticles supported by an acidic ionic liquid catalyst, characterized in that, The method includes the following steps: (1) Magnetic nanoparticles were prepared by coprecipitation method; (2) 2-Methylimidazole and sodium methoxide were poured into a three-necked flask with a magnetic stirrer, methanol was added, and the mixture was heated to 60°C and stirred for 6 h. 3-Chloropropyltriethoxysilane was slowly added dropwise to the reaction solution under a nitrogen atmosphere and the mixture was stirred for 16 h. The mixture was filtered. Toluenesulfonic acid was added to the filtrate and the mixture was heated to 60°C and stirred for 16 h. The reaction solution was cooled to room temperature and placed in an ice-water bath. 98% concentrated sulfuric acid was added dropwise using a constant pressure dropping funnel and the mixture was sonicated for 8 h. The mixture was then washed with ether and dried in a vacuum drying oven at 45°C for 8 h to obtain an acidic ionic liquid. (3) Place the magnetic nanoparticles and acidic ionic liquid in a three-necked flask, pour in anhydrous toluene, heat under nitrogen atmosphere and reflux for 8 h, then wash the magnetic nanoparticles loaded with acidic ionic liquid with ether 3-5 times, and dry in a vacuum drying oven at 45℃ for 12 h to obtain magnetic nanoparticles loaded with acidic ionic liquid. (4) Add oxazolidinone and acetal to a three-necked flask, add magnetic nanoparticle-supported acidic ionic liquid as a catalyst, react at atmospheric pressure and at a reaction temperature of 25-50℃ for 4-8 h. After the reaction is completed, filter the catalyst by magnetic adsorption, adjust the pH to weakly alkaline with sodium bicarbonate, heat the filtrate to 40℃ for vacuum distillation, then heat to 90-110℃ and distill under a vacuum of <100pa to obtain 3-(1-ethoxyethyl)oxazolidinone.

2. The method according to claim 1, characterized in that, 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.

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

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

1.

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

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

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

2.

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

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

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