The invention relates to a method for green and efficient preparation of 3-amino-4apos; method for preparing nitrodiphenyl ether

Abstract

The invention relates to a method for green and efficient preparation of 3-amino-4 '-nitrodiphenyl ether, and belongs to the technical field of organic synthesis. The method for preparing 3-amino-4 '-nitrodiphenyl ether comprises the following steps: S1, reacting a hydrogen bond acceptor and a hydrogen bond donor under a heating condition to prepare DES; and S2, adding parachloronitrobenzene and m-aminophenol into the DES prepared in the step S1, heating to carry out etherification reaction, and carrying out water washing and solid-liquid separation treatment on the reaction liquid to obtain the 3-amino-4 '-nitrodiphenyl ether product. The hydrogen bond receptor is at least one of choline chloride and betaine; the hydrogen bond donor is at least one of polyethylene glycol, urea and thiourea. The method for preparing the 3-amino-4 '-nitrodiphenyl ether has the advantages of mild reaction conditions, environmental friendliness and the like, and the 3-amino-4'-nitrodiphenyl ether product with high yield and high purity can be directly obtained.

Description

Technical Field

[0001] This invention relates to a green and efficient method for preparing 3-amino-4'-nitrodiphenyl ether, belonging to the field of organic synthesis technology. Background Technology

[0002] 3,4'-Diaminodiphenyl ether is a high-value-added fine chemical intermediate, a key monomer in the synthesis of heat-resistant plastics such as polyimide and polymaleimide, and also serves as a curing agent for epoxy resins and an intermediate for coatings. 3-Amino-4'-nitrodiphenyl ether is a crucial intermediate in its synthesis. For example, patent JP4473150B2 discloses a method for producing low-chlorinated 3,4'-diaminodiphenyl ether, which involves condensing m-aminophenol and p-chloronitrobenzene in a solvent to obtain 3-amino-4'-nitrodiphenyl ether, then reducing it using an alkali metal carbonate as a condensing agent to prepare 3,4'-diaminodiphenyl ether. Therefore, to meet the demand for 3,4'-diaminodiphenyl ether preparation, an efficient and convenient method for its synthesis is needed.

[0003] 3-Amino-4'-nitrodiphenyl ether is a yellow solid with a distinctive odor. It is insoluble in water but soluble in organic solvents such as ethanol. It exhibits high stability at room temperature and is not easily affected by light or heat. Traditional processes for preparing 3-amino-4'-nitrodiphenyl ether typically involve the condensation of m-aminophenol or m-nitrophenol with p-chloronitrobenzene. For example, patent application JP1994345703A discloses a method for producing aminodiphenyl ether. The specific method involves the condensation reaction of p-halonitrobenzene and m-aminophenol in the presence of alkali metal carbonates in an aprotic organic polar solvent to generate 3-amino-4'-nitrodiphenyl ether. The aprotic organic polar solvents used include N,N-dimethylformamide (DMF), N,N-dimethylacetamide (DMAc), N-methyl-2-pyrrolidone (NMP), dimethyl sulfoxide (DMSO), sulfolane, etc. However, these traditional processes suffer from problems such as the use of large amounts of organic solvents, environmental unfriendliness, and difficulty in treating the generated waste. Moreover, the reaction temperature is relatively high, generally above 100°C, resulting in high energy consumption. Summary of the Invention

[0004] This invention addresses the shortcomings of existing technologies by providing a green and efficient method for preparing 3-amino-4'-nitrodiphenyl ether. The method for preparing 3-amino-4'-nitrodiphenyl ether has advantages such as mild reaction conditions, environmental friendliness, high product yield, and high purity.

[0005] The technical solution of this invention to solve the above-mentioned technical problems is as follows: A green and efficient method for preparing 3-amino-4'-nitrodiphenyl ether, wherein the method for preparing 3-amino-4'-nitrodiphenyl ether is as follows: S1, hydrogen bond acceptor and hydrogen bond donor react under heating conditions to produce DES; S2. Add p-chloronitrobenzene and m-aminophenol to the DES obtained in step S1, heat to carry out etherification reaction, and wash the reaction solution with water and perform solid-liquid separation treatment to obtain 3-amino-4'-nitrodiphenyl ether product.

[0006] Based on the above technical solution, the present invention can be further improved as follows: Furthermore, the hydrogen bond acceptor is at least one of choline chloride and betaine.

[0007] Furthermore, the hydrogen bond donor is at least one of polyethylene glycol, urea, and thiourea.

[0008] Furthermore, in step S1, the heating conditions for preparing DES are 60~100℃, and the reaction time is 0.5-2h.

[0009] Furthermore, in step S1, the molar ratio of the hydrogen bond acceptor to the hydrogen bond donor is 1:2.

[0010] Furthermore, in step S2, the molar ratio of m-aminophenol to p-chloronitrobenzene is 1.0:(1.0-1.2).

[0011] Furthermore, specifically, in step S2, the total mass of p-chloronitrobenzene and m-aminophenol is 10%-30% of the mass of the DES.

[0012] Furthermore, in step S2, the heating conditions for the etherification reaction are 40~100℃ and the reaction time is 4-10h.

[0013] Furthermore, the heating temperature during the etherification reaction in step S2 is not higher than the heating temperature in step S1.

[0014] Furthermore, in step S2, during the water washing treatment after the etherification reaction, the mass ratio of the material in the reaction system to the mass of added water is 1:(4-10).

[0015] The beneficial effects of this invention are: The method for preparing 3-amino-4'-nitrodiphenyl ether described in this invention first prepares a diethyl ether solvent (DES), and then uses p-chloronitrobenzene and m-aminophenol as raw materials to efficiently and conveniently synthesize 3-amino-4'-nitrodiphenyl ether under the action of DES. This method uses a more environmentally friendly and reusable eutectic solvent (DES), and there is no synthesis of metals and ligands in this process. It also avoids the use of aprotic solvents, resulting in excellent yield, economic efficiency, environmental friendliness, and high feasibility.

[0016] The method for preparing 3-amino-4'-nitrodiphenyl ether described in this invention has the advantages of mild reaction conditions and environmental friendliness, and can directly obtain 3-amino-4'-nitrodiphenyl ether products with high yield and high purity.

[0017] Dextromethorphan Ether (DES), a novel green solvent, is formed by hydrogen bond interactions between a hydrogen bond donor (HBD) and a hydrogen bond acceptor (HBA). This interaction stabilizes the active form of the nucleophile. DES forms hydrogen bonds with the hydroxyl group of m-aminophenol, enhancing nucleophilic reactivity, accelerating the reaction rate, significantly shortening reaction time, and improving reaction rate and selectivity. DES possesses advantages such as low volatility, high stability, and unique solubility, effectively improving reaction solubility. Compared to the preparation process of 3-amino-4'-nitrodiphenyl ether, traditional solvents (such as DMAc and DMF) suffer from toxicity, poor degradation, high volatility (VOC emissions), and high energy consumption for recovery. DES, typically composed of compounds with no significant toxicity, reduces reaction risks while avoiding air pollution caused by the volatilization of traditional solvents. Furthermore, DES simplifies post-reaction processing, reducing the cost of waste treatment. Attached Figure Description

[0018] Figure 1 The gas chromatographic spectrum of 3-amino-4'-nitrodiphenyl ether; Figure 2 is an enlarged view of the gas chromatographic detection spectrum in Figure 1. Detailed Implementation

[0019] To make the above-mentioned objects, features, and advantages of the present invention more apparent and understandable, specific embodiments of the present invention are described in detail below. Many specific details are set forth in the following description to provide a thorough understanding of the present invention. However, the present invention can be practiced in many other ways different from those described herein, and those skilled in the art can make similar modifications without departing from the spirit of the present invention. Therefore, the present invention is not limited to the specific embodiments disclosed below.

[0020] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains. The terminology used herein in the description of the invention is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention.

[0021] A green and efficient method for preparing 3-amino-4'-nitrodiphenyl ether, wherein the method for preparing 3-amino-4'-nitrodiphenyl ether is as follows: S1, hydrogen bond acceptor and hydrogen bond donor react under heating conditions to produce DES; S2. Add p-chloronitrobenzene and m-aminophenol to the DES obtained in step S1, heat to carry out etherification reaction, wash the reaction solution with water, filter and dry to obtain 3-amino-4'-nitrodiphenyl ether product; the specific reaction principle is as follows: .

[0022] Based on the above technical solution, the present invention can be further improved as follows: Specifically, the hydrogen bond acceptor is at least one of choline chloride and betaine.

[0023] Specifically, the hydrogen bond donor is at least one of polyethylene glycol, urea, and thiourea.

[0024] Preferably, the hydrogen bond acceptor is choline chloride, and using choline chloride to prepare DES provides better selectivity.

[0025] Preferably, the hydrogen bond donor is urea, which is low in cost and can form a multi-layered and stable hydrogen bond network with the hydrogen bond acceptor.

[0026] Specifically, in step S1, the heating conditions for preparing DES are 60-100℃, and the reaction time is 0.5-2h. During the preparation of DES, the reaction temperature must be strictly controlled. Too low a temperature will result in a slow dissolution rate of the raw materials, uneven mixing, and insufficient hydrogen bond formation, making it difficult to form uniform DES. Too high a temperature may destroy the already formed hydrogen bond network and even cause some of the raw materials to decompose, thus affecting the yield and purity of the etherification reaction. Therefore, it is crucial to carefully control the preparation temperature of DES during the preparation process.

[0027] Specifically, in step S1, the molar ratio of the hydrogen bond acceptor to the hydrogen bond donor is 1:2.

[0028] Specifically, in step S2, the molar ratio of m-aminophenol to p-chloronitrobenzene is 1.0:(1.0-1.2).

[0029] Specifically, in step S2, the total mass of p-chloronitrobenzene and m-aminophenol is 10%-30% of the mass of DES.

[0030] Specifically, in step S2, the heating conditions for the etherification reaction are 40-100℃ and the reaction time is 4-10h.

[0031] Preferably, in step S2, the heating reaction conditions during the etherification reaction are 80-100°C.

[0032] Specifically, in step S2, the heating temperature during the etherification reaction is not higher than the heating temperature in step S1.

[0033] Specifically, in step S2, during the water washing treatment after the etherification reaction, the mass ratio of DES to added water in the reaction system is 1:(4-10).

[0034] More specifically, the filtrate after solid-liquid separation is distilled to separate water and DES, and the separated DES is then used in the next reaction. DES can be reused at least 4 times while still maintaining high activity.

[0035] Example 1 A green and efficient method for preparing 3-amino-4'-nitrodiphenyl ether is described below: (1) Preparation of DES: Under normal pressure, 55.85g of choline chloride (0.4mol) was added to a round-bottom flask, followed by 48.04g of urea (0.8mol). The mixture was stirred evenly and heated to 80°C in an oil bath. The mixture was then stirred magnetically for 30 minutes to obtain colorless and transparent DES.

[0036] (2) Preparation of 3-amino-4'-nitrodiphenyl ether: Weigh 82.7g of the prepared DES into a round-bottom flask, then add 16.54g (0.105mol) of p-chloronitrobenzene and 10.91g (0.1mol) of m-aminophenol in sequence, mix well, and heat to 80℃ in an oil bath. React under magnetic stirring. Monitor the reaction by thin-layer chromatography (using silica gel plate, with a volume ratio of petroleum ether to ethyl acetate in the developing solvent of 1:2, and clear separation of raw materials and products). The reaction is complete after 4 hours, and then allowed to cool naturally. After the reaction is complete, add 578.9g of water to the system, stir at room temperature for 30min, and 3-amino-4'-nitrodiphenyl ether solid is uniformly precipitated. Filter to obtain a pale yellow solid, dry, weigh, and send the solid for gas chromatography analysis. The yield of this reaction is 98.32%, and the purity is 99.62% (the specific gas chromatography spectrum is shown in Figure 1). Figure 1 (As shown in Figure 2), the gas chromatography detection data are shown in Table 1 below.

[0037] Table 1 Gas Chromatography Detection Data

[0038] The DES-water mixture collected after filtration was poured into a round-bottom flask, a magnetic stir bar was added, and a vacuum distillation apparatus was installed. The magnetic stirrer and vacuum pump were turned on, and the mixture was heated to 60°C. Water began to slowly distill out. Distillation continued until no distillate was obtained (1-2 hours). Heating was then stopped, and the system was allowed to cool to room temperature before the vacuum was released, yielding regenerated DES. The regenerated DES was then used again for the etherification reaction (following the same method as in Example 1). After the reaction was completed, the DES-water mixture was collected again, and the above steps were repeated. Experiments showed that DES could be reused four times while still ensuring a yield of 3-amino-4'-nitrodiphenyl ether of not less than 97% and a purity of not less than 99%.

[0039] Example 2 A green and efficient method for preparing 3-amino-4'-nitrodiphenyl ether is described below: (1) Preparation of DES: Under normal pressure, 41.87 g of choline chloride (0.3 mol) was added to a round-bottom flask, followed by 36.04 g of urea (0.6 mol). The mixture was stirred evenly and heated to 80 °C in an oil bath. The mixture was then stirred magnetically for 30 min to obtain colorless and transparent DES.

[0040] (2) Preparation of 3-amino-4'-nitrodiphenyl ether: Weigh 55.13 g of the prepared DES into a round-bottom flask, then add 16.54 g (0.105 mol) of p-chloronitrobenzene and 10.91 g (0.1 mol) of m-aminophenol in sequence, mix well, and heat to 80 °C in an oil bath. React under magnetic stirring. Monitor the reaction by thin-layer chromatography (using silica gel plate, with a volume ratio of petroleum ether to ethyl acetate in the developing solvent of 1:2, and clear separation of raw materials and products). The reaction is complete after 3 h, and then allowed to cool naturally. After the reaction is complete, add 385.91 g of water to the system, stir at room temperature for 30 min, and 3-amino-4'-nitrodiphenyl ether solid is uniformly precipitated. Filter to obtain a pale yellow solid, dry, weigh, and send the solid for gas chromatography analysis. The yield of this reaction is 97.44%, and the purity is 99.23%.

[0041] Example 3 A green and efficient method for preparing 3-amino-4'-nitrodiphenyl ether is described below: (1) Preparation of DES: Under normal pressure, 41.87g (0.3mol) of choline chloride was added to a round-bottom flask, followed by 120.00g of polyethylene glycol 200 (0.6mol). The mixture was stirred evenly and heated to 100°C in an oil bath. The mixture was then stirred magnetically for 1 hour to obtain colorless and transparent DES.

[0042] (2) Preparation of 3-amino-4'-nitrodiphenyl ether: Weigh 160.7 g of the prepared DES into a round-bottom flask, then add 16.07 g (0.102 mol) of p-chloronitrobenzene and 10.91 g (0.1 mol) of m-aminophenol in sequence, mix well, and heat to 100 °C in an oil bath. React under magnetic stirring. Monitor the reaction by thin-layer chromatography (using silica gel plate, with a volume ratio of petroleum ether to ethyl acetate in the developing solvent of 1:2, and clear separation of raw materials and products). The reaction is complete after 8 h, and then cooled naturally. After the reaction is complete, add 1124.9 g of water to the system, stir at room temperature for 30 min, and 3-amino-4'-nitrodiphenyl ether solid is uniformly precipitated. Filter to obtain a yellow solid, dry, weigh, and send the solid to gas chromatography for analysis. The yield of this reaction is 92.02%, and the purity is 95.11%.

[0043] Example 4 A green and efficient method for preparing 3-amino-4'-nitrodiphenyl ether is described below: (1) Preparation of DES: Under normal pressure, 97.73 g of choline chloride (0.7 mol) was added to a round-bottom flask, followed by 84.08 g of urea (1.4 mol). The mixture was stirred evenly and heated to 80°C in an oil bath. The mixture was then stirred magnetically for 30 min to obtain colorless and transparent DES.

[0044] (2) Preparation of 3-amino-4'-nitrodiphenyl ether: Weigh 82.7g of the prepared DES into a round-bottom flask, then add 16.54g (0.105mol) of p-chloronitrobenzene and 10.91g (0.1mol) of m-aminophenol in sequence, mix well, and heat in an oil bath to 80℃. React under magnetic stirring, and monitor the reaction by thin-layer chromatography (using silica gel plate, with a volume ratio of petroleum ether to ethyl acetate in the developing solvent of 1:2, and clear separation of raw materials and products). The reaction is complete after 4 hours, and then cooled naturally. After the reaction is complete, add 827g of water to the system, stir at room temperature for 30min, and 3-amino-4'-nitrodiphenyl ether solid is uniformly precipitated. Filter to obtain a yellow solid, dry, weigh, and send the solid for gas chromatography analysis. The yield of this reaction is 92.21%, and the purity is 95.65%.

[0045] Example 5 A green and efficient method for preparing 3-amino-4'-nitrodiphenyl ether is described below: (1) Preparation of DES: Under normal pressure, 69.81 g of choline chloride (0.5 mol) was added to a round-bottom flask, followed by 60.06 g of urea (1.0 mol). The mixture was stirred evenly and heated to 80°C in an oil bath. The mixture was then stirred magnetically for 30 min to obtain colorless and transparent DES.

[0046] (2) Preparation of 3-amino-4'-nitrodiphenyl ether: Weigh 110.27 g of the prepared DES into a round-bottom flask, then add 16.54 g (0.105 mol) of p-chloronitrobenzene and 10.91 g (0.1 mol) of m-aminophenol in sequence, mix well, and heat in an oil bath to 80 °C. React under magnetic stirring, and monitor the reaction by thin-layer chromatography (using silica gel plate, with a volume ratio of petroleum ether to ethyl acetate in the developing solvent of 1:2, and clear separation of raw materials and products). The reaction is complete after 6 h, and then cooled naturally. After the reaction is complete, add 771.87 g of water to the system, stir at room temperature for 30 min, and 3-amino-4'-nitrodiphenyl ether solid is uniformly precipitated. Filter to obtain a yellow solid, dry, weigh, and send the solid to gas chromatogram for analysis. The yield of this reaction is 96.38%, and the purity is 98.18%.

[0047] Example 6 A green and efficient method for preparing 3-amino-4'-nitrodiphenyl ether is described below: (1) Preparation of DES: Under normal pressure, 55.85g of choline chloride (0.4mol) was added to a round-bottom flask, followed by 48.04g of urea (0.8mol). The mixture was stirred evenly and heated to 80°C in an oil bath. The mixture was then stirred magnetically for 30 minutes to obtain colorless and transparent DES.

[0048] (2) Preparation of 3-amino-4'-nitrodiphenyl ether: Weigh 82.7g of the prepared DES into a round-bottom flask, then add 16.54g (0.105mol) of p-chloronitrobenzene and 10.91g (0.1mol) of m-aminophenol in sequence, mix well, and heat to 100℃ in an oil bath. React under magnetic stirring, and monitor the reaction by thin-layer chromatography (using silica gel plate, with a volume ratio of petroleum ether to ethyl acetate in the developing solvent of 1:2, and clear separation of raw materials and products). The reaction is complete after 3 hours, and then cooled naturally. After the reaction is complete, add 578.9g of water to the system, stir at room temperature for 30min, and 3-amino-4'-nitrodiphenyl ether solid is uniformly precipitated. Filter to obtain a yellow solid, dry, weigh, and send the solid to gas chromatography for analysis. The yield of this reaction is 98.05%, and the purity is 98.93%.

[0049] The difference between Example 6 and Example 1 is that the heating temperature during the etherification reaction in step S2 of Comparative Example 6 is higher than the heating temperature in step S1. A comparison of the results of Example 6 and Example 1 shows that the higher reaction temperature in step S2 leads to a decrease in the yield and purity of the target product, 3-amino-4'-nitrodiphenyl ether. Therefore, a heating temperature during the etherification reaction in step S2 that is not higher than the heating temperature in step S1 is more conducive to ensuring the activity of DES and guaranteeing a better reaction.

[0050] Example 7 A green and efficient method for preparing 3-amino-4'-nitrodiphenyl ether is described below: (1) Preparation of DES: Under normal pressure, 55.85g of choline chloride (0.4mol) was added to a round-bottom flask, followed by 48.04g of urea (0.8mol). The mixture was stirred evenly and heated to 80°C in an oil bath. The mixture was then stirred magnetically for 30 minutes to obtain colorless and transparent DES.

[0051] (2) Preparation of 3-amino-4'-nitrodiphenyl ether: Weigh 78.8 g of the prepared DES into a round-bottom flask, then add 15.76 g (0.1 mol) of p-chloronitrobenzene and 10.91 g (0.1 mol) of m-aminophenol in sequence, mix well, and heat in an oil bath to 80 °C. React under magnetic stirring, and monitor the reaction by thin-layer chromatography (using silica gel plate, with a volume ratio of petroleum ether to ethyl acetate in the developing solvent of 1:2, and clear separation of raw materials and products). The reaction is complete after 4 h, and then cooled naturally. After the reaction is complete, add 551.6 g of water to the system, stir at room temperature for 30 min, and 3-amino-4'-nitrodiphenyl ether solid is uniformly precipitated. Filter to obtain a pale yellow solid, dry, weigh, and send the solid to gas chromatography for analysis. The yield of this reaction is 93.32%, and the purity is 99.13%.

[0052] Example 8 A green and efficient method for preparing 3-amino-4'-nitrodiphenyl ether is described below: (1) Preparation of DES: Under normal pressure, 55.85g of choline chloride (0.4mol) was added to a round-bottom flask, followed by 48.04g of urea (0.8mol). The mixture was stirred evenly and heated to 80°C in an oil bath. The mixture was then stirred magnetically for 30 minutes to obtain colorless and transparent DES.

[0053] (2) Preparation of 3-amino-4'-nitrodiphenyl ether: Weigh 94.55 g of the prepared DES into a round-bottom flask, then add 18.91 g (0.12 mol) of p-chloronitrobenzene and 10.91 g (0.1 mol) of m-aminophenol in sequence, mix well, and heat in an oil bath to 80 °C. React under magnetic stirring, and monitor the reaction by thin-layer chromatography (using silica gel plate, with a volume ratio of petroleum ether to ethyl acetate in the developing solvent of 1:2, and clear separation of raw materials and products). The reaction is complete after 4 h, and then cooled naturally. After the reaction is complete, add 661.85 g of water to the system, stir at room temperature for 30 min, and 3-amino-4'-nitrodiphenyl ether solid is uniformly precipitated. Filter to obtain a pale yellow solid, dry, weigh, and send the solid to gas chromatogram for analysis. The yield of this reaction is 98.44%, and the purity is 99.48%.

[0054] Comparative Example 1 3-Amino-4'-nitrodiphenyl ether was prepared using the same method as in Example 1, except that the reaction temperature in step (2) of Comparative Example 1 was 120°C (higher than the temperature range specified in this invention), as detailed below: (1) Preparation of DES: Under normal pressure, 55.85g of choline chloride (0.4mol) was added to a round-bottom flask, followed by 48.04g of urea (0.8mol). The mixture was stirred evenly and heated to 80°C in an oil bath. The mixture was then stirred magnetically for 30 minutes to obtain colorless and transparent DES.

[0055] (2) Preparation of 3-amino-4'-nitrodiphenyl ether: Weigh 82.7 g of the prepared DES into a round-bottom flask, then add 16.54 g (0.105 mol) of p-chloronitrobenzene and 10.91 g (0.1 mol) of m-aminophenol in sequence, mix well, and heat in an oil bath to 120 °C. React under magnetic stirring, and monitor the reaction by thin-layer chromatography (using silica gel plate, with a volume ratio of petroleum ether to ethyl acetate in the developing solvent of 1:2, and clear separation of raw materials and products). The reaction is complete after 4 h, and then cooled naturally. After the reaction is complete, add 578.9 g of water to the system, stir at room temperature for 30 min, and 3-amino-4'-nitrodiphenyl ether solid is uniformly precipitated. Filter to obtain a yellow solid, dry, weigh, and send the solid to gas chromatography for analysis. The yield of this reaction is 62.35%, and the purity is 90.14%.

[0056] The data comparison between Comparative Example 1 and Example 1 shows that if the reaction temperature in step (2) is too high, the yield and purity of the 3-amino-4'-nitrodiphenyl ether product will decrease significantly. Increasing the temperature will cause DES to denature and deactivate, ultimately affecting the yield and purity of the target product.

[0057] Comparative Example 2 3-Amino-4'-nitrodiphenyl ether was prepared using the same method as in Example 1, except that in step (2) of Comparative Example 1, the molar ratio of p-chloronitrobenzene to m-aminophenol was 1:1.05 (i.e., the intermediate aminophenol was in excess), as detailed below: A green and efficient method for preparing 3-amino-4'-nitrodiphenyl ether is described below: (1) Preparation of DES: Under normal pressure, 55.85g of choline chloride (0.4mol) was added to a round-bottom flask, followed by 48.04g of urea (0.8mol). The mixture was stirred evenly and heated to 80°C in an oil bath. The mixture was then stirred magnetically for 30 minutes to obtain colorless and transparent DES.

[0058] (2) Preparation of 3-amino-4'-nitrodiphenyl ether: Weigh 78.8 g of the prepared DES into a round-bottom flask, then add 15.76 g (0.1 mol) of p-chloronitrobenzene and 11.46 g (0.105 mol) of m-aminophenol in sequence, mix well, and heat in an oil bath to 80 °C. React under magnetic stirring, and monitor the reaction by thin-layer chromatography (using silica gel plate, with a volume ratio of petroleum ether to ethyl acetate in the developing solvent of 1:2, and clear separation of raw materials and products). The reaction is complete after 4 h, and then cooled naturally. After the reaction is complete, add 551.6 g of water to the system, stir at room temperature for 30 min, and 3-amino-4'-nitrodiphenyl ether solid is uniformly precipitated. Filter to obtain a dark yellow solid, dry, weigh, and send the solid to gas chromatogram for analysis. The yield of this reaction is 92.21%, and the purity is 92.44%.

[0059] Comparison of data from Comparative Example 2 and Example 1 shows that if m-aminophenol is in excess during the etherification reaction in step (2), the target product 3-amino-4'-nitrodiphenyl ether becomes darker in color, and the yield and purity decrease significantly. The reasons are as follows: (1) When m-aminophenol is in excess, it may undergo condensation or intramolecular / intermolecular interactions at the high temperature of the reaction, resulting in a decrease in yield and purity; (2) In this reaction, the reactivity of halogenated aromatic hydrocarbons containing electron-withdrawing groups is enhanced, while they do not react with electron-donating groups. The reaction rate increases as the electron cloud density in the aromatic ring system decreases. The hydrogen bond interaction between DES and halogenated aromatic hydrocarbons and phenols enhances the electrophilicity and nucleophilicity of halogenated hydrocarbons, thereby promoting the attack of m-aminophenol and generating a resonant stable structure, so that the yield and purity of the reaction reach the optimal level. Therefore, an excess of p-chloronitrobenzene is beneficial to the forward reaction.

[0060] Comparative Example 3 Comparative Example 3 uses a conventional polar solvent system to prepare 3-amino-4'-nitrodiphenyl ether. The specific preparation process is as follows: 17.33 g (0.11 mol) of p-chloronitrobenzene, 10.91 g (0.1 mol) of m-aminophenol, 27.64 g (2.0 mol) of potassium carbonate, and 100 g of N,N-dimethylacetamide (DMAc) were added sequentially to a three-necked flask. The mixture was thoroughly combined and heated to 140 °C in an oil bath with magnetic stirring. The reaction was monitored by thin-layer chromatography (using a silica gel plate with a petroleum ether to ethyl acetate volume ratio of 1:2 in the developing solvent, resulting in clear separation of the reactants and products). The reaction was allowed to proceed for 6 hours until complete, followed by natural cooling. After the reaction was complete, 1000 g of water was added to the system, and the mixture was stirred at room temperature for 30 minutes, resulting in the uniform precipitation of 3-amino-4'-nitrodiphenyl ether solid. The solid was filtered to obtain a pale yellow solid, dried, weighed, and analyzed by gas chromatography. The yield of this reaction was 91.52%, and the purity was 94.72%.

[0061] A comparison of the experimental results of Comparative Example 3 and Example 1 above shows that the method for preparing 3-amino-4'-nitrodiphenyl ether described in this invention uses a DES system for reaction. Compared with conventional polar solvent systems, this method can effectively reduce the reaction temperature, shorten the production cycle, and improve the reaction efficiency.

[0062] The technical features of the above embodiments can be combined in any way. For the sake of brevity, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0063] The embodiments described above are merely illustrative of several implementations of the present invention, and while the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the invention patent. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the present invention, and these all fall within the protection scope of the present invention. Therefore, the protection scope of this invention patent should be determined by the appended claims.

Claims

1. A green and efficient method for preparing 3-amino-4'-nitrodiphenyl ether, characterized in that, The method for preparing 3-amino-4'-nitrodiphenyl ether is as follows: S1, hydrogen bond acceptor and hydrogen bond donor are reacted under heating conditions to produce DES; S2. Add p-chloronitrobenzene and m-aminophenol to the DES obtained in step S1, heat to carry out etherification reaction, and wash the reaction solution with water and perform solid-liquid separation treatment to obtain 3-amino-4'-nitrodiphenyl ether product.

2. The method for preparing 3-amino-4'-nitrodiphenyl ether in a green and efficient manner according to claim 1, characterized in that, The hydrogen bond acceptor is at least one of choline chloride and betaine.

3. The method for preparing 3-amino-4'-nitrodiphenyl ether in a green and efficient manner according to claim 1, characterized in that, The hydrogen bond donor is at least one of polyethylene glycol, urea, and thiourea.

4. The method for preparing 3-amino-4'-nitrodiphenyl ether in a green and efficient manner according to claim 1, characterized in that, In step S1, the heating conditions for preparing DES are 60~100℃ and the reaction time is 0.5-2h.

5. The method for preparing 3-amino-4'-nitrodiphenyl ether in a green and efficient manner according to claim 1, characterized in that, In step S1, the molar ratio of the hydrogen bond acceptor to the hydrogen bond donor is 1:

2.

6. The method for preparing 3-amino-4'-nitrodiphenyl ether in a green and efficient manner according to claim 1, characterized in that, In step S2, the molar ratio of m-aminophenol to p-chloronitrobenzene is 1.0:(1.0-1.2).

7. The method for preparing 3-amino-4'-nitrodiphenyl ether in a green and efficient manner according to claim 1, characterized in that, Specifically, in step S2, the total mass of p-chloronitrobenzene and m-aminophenol is 10%-30% of the mass of DES.

8. The method for preparing 3-amino-4'-nitrodiphenyl ether in a green and efficient manner according to claim 1, characterized in that, In step S2, the heating conditions for the etherification reaction are 40~100℃ and the reaction time is 4-10h.

9. The method for preparing 3-amino-4'-nitrodiphenyl ether in a green and efficient manner according to claim 1, characterized in that, The heating temperature during the etherification reaction in step S2 shall not be higher than the heating temperature in step S1.

10. The method for preparing 3-amino-4'-nitrodiphenyl ether in a green and efficient manner according to claim 1, characterized in that, In step S2, during the water washing process after the etherification reaction, the mass ratio of the material in the reaction system to the mass of water added is 1:(4-10).

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