A method for synthesizing 2-aminopyridine

Abstract

The invention discloses a method for synthesizing 2-aminopyridine, comprising using polystyrene resin beads as a carrier, a mixed solvent consisting of 1,2-dichloroethane and anhydrous ethanol as a porogen, adding the polystyrene resin beads and the mixed solvent to a flask for swelling; adding N,N-dimethylaniline to the flask, and performing a stirring reflux reaction; repeatedly washing the mixed solution in the flask with anhydrous ethanol and filtering it with suction, and finally vacuum drying it at room temperature. The method for synthesizing 2-aminopyridine utilizes polymer resin beads as a carrier, grafts a preferred highly active phase transfer catalyst molecule - N,N-dimethylaniline, and synthesizes a solid-supported phase transfer catalyst to achieve efficient recycling and regeneration of the phase transfer catalyst, and ensures the yield of the pyridine amination product by the solid-supported phase transfer catalyst, which is conducive to ensuring the efficient resource utilization of basic nitrogen heterocyclic compounds in coal tar.

Description

Technical Field

[0001] This invention relates to the field of resource utilization technology of medium-alkaline nitrogen heterocyclic compounds, specifically a method for synthesizing 2-aminopyridine. Background Technology

[0002] More than 500 compounds have been identified in coal tar, of which more than 120 are nitrogen-containing compounds. Almost all of them are nitrogen heterocycles containing only one nitrogen atom, mainly pyridine and its derivatives, indole, quinoline and its derivatives. Nitrogen heterocycles have a significant adverse impact on the production process. The traditional process of hydrodenitrification uses sulfide catalysts to remove most neutral nitrogen-containing compounds, but the removal efficiency for basic nitrogen heterocycles (pyridine, quinoline, etc.) is not high. If the traditional method is changed and the compounds are directly converted into energetic molecules without removal treatment, not only can the added value of coal tar be increased, but its resource utilization can also be realized.

[0003] Nitrogen heterocycles (such as pyridine rings) replace benzene rings as the basic structural unit of energetic compounds, which have advantages such as high heat of formation, high density and good thermal stability. For example, the introduction of amino groups, especially ortho-amino groups (i.e. 2-aminopyridine) into the pyridine molecule structure is beneficial to the formation of hydrogen bonds inside and outside the molecule, thereby improving molecular energy, safety performance and crystal density.

[0004] Currently, there are two synthetic methods for generating 2-aminopyridine using pyridine, a nitrogen heterocyclic compound, as a model compound: indirect ammoniation and direct ammoniation. Indirect ammoniation suffers from difficulties in synthesizing reactants and catalysts, leading to low feasibility. Direct ammoniation, on the other hand, results in numerous byproducts and low product yields. Industrially, direct ammoniation involves reacting sodium amide with pyridine using toluene as an organic solvent. However, this method suffers from low product yields and, moreover, pyridine ammoniation is a heterogeneous reaction, presenting challenges in mass transfer. Amino anions rarely react directly with pyridine, resulting in slow reaction rates and low yields and selectivity of the target product. Therefore, current methods often employ the addition of phase transfer catalysts. These catalysts utilize their organophilic properties to transfer ionic reactants insoluble in the organic phase to the organic phase, promoting the reaction and overcoming the mass transfer difficulties inherent in heterogeneous reactions, thereby improving the yield of pyridine ammoniation products.

[0005] However, in the direct ammoniation method, since the reactants (basic nitrogen heterocyclic compounds), organic solvents, and phase transfer catalysts are all liquid substances, there is a problem that the phase transfer catalyst is difficult to recover. Since the organic solvents and phase transfer catalysts are both in the water-insoluble organic layer in the product mixture after the reaction, the two are not easy to separate, which makes it impossible to recover and recycle the phase transfer catalyst, which is not conducive to ensuring the efficient utilization of basic nitrogen heterocyclic compounds in coal tar.

[0006] In view of this, in-depth research was conducted on the above issues, which led to the creation of this case. Summary of the Invention

[0007] The purpose of this invention is to provide a method for synthesizing 2-aminopyridine, in order to solve the problem mentioned in the background art that the existing methods for the efficient utilization of basic nitrogen heterocyclic compounds in coal tar using the direct ammoniation method are inconvenient for the recovery and recycling of phase transfer catalysts, which is not conducive to ensuring the efficient utilization of basic nitrogen heterocyclic compounds in coal tar.

[0008] To achieve the above objectives, the present invention provides the following technical solution: a method for synthesizing 2-aminopyridine, comprising the following steps:

[0009] Step 1: Using polystyrene resin microspheres as a carrier and a mixed solvent of 1,2-dichloroethane and anhydrous ethanol as a pore-forming agent, the polystyrene resin microspheres and the mixed solvent are added to a flask for swelling.

[0010] Step 2: Add N,N-dimethylaniline to the flask and stir under reflux for reaction;

[0011] Step 3: The mixture in the flask is repeatedly washed with anhydrous ethanol and filtered, and finally dried under vacuum at room temperature to obtain a supported phase transfer catalyst grafted with N,N-dimethylaniline onto polystyrene resin.

[0012] Step 4: Mix and stir the crushed sodium amino acid (NaNH2) solid, organic solvent and supported phase transfer catalyst to the reaction temperature, then slowly add pyridine dropwise. After the addition is complete, reflux the reaction, cool down and add water, hydrolyze at a constant temperature, and finally cool and filter to obtain the product 2-aminopyridine.

[0013] Step 5: Use anhydrous ethanol as a solvent to wash away the organic molecules of reactants adsorbed on the surface and inside the supported phase transfer catalyst, use dilute hydrochloric acid to wash away the metal salt ions adsorbed on the surface and inside, then repeatedly wash with ultrapure water until neutral, and finally perform vacuum drying at room temperature to complete the regeneration of the supported phase transfer catalyst.

[0014] As a preferred embodiment of the present invention, the swelling time of the polystyrene resin microspheres and the mixed solvent in step one is 11-13 hours.

[0015] As a preferred embodiment of the present invention, in step two, the stirring temperature is controlled at 50-70℃ and the stirring time is 11-13h.

[0016] As a preferred embodiment of the present invention, the vacuum drying time in step three is 5-7 hours.

[0017] As a preferred embodiment of the present invention, the organic solvent in step four is one of the following: chain hydrocarbons such as dodecane and n-decane; aromatic hydrocarbons such as tetrahydronaphthalene and decahydronaphthalene; and benzene, toluene, xylene, and N,N-dimethylformamide.

[0018] As a preferred technical solution of the present invention, in step four, powdered sodium amide (NaNH2) solid, organic solvent and supported phase transfer catalyst are mixed and stirred and heated to 100-120°C. After adding pyridine dropwise, the mixture is refluxed for 3-7 h. After reflux, the mixture is cooled to 70°C and water is added for constant-temperature hydrolysis for 0.3-0.8 h.

[0019] As a preferred technical solution of the present invention, the vacuum drying time in step five is controlled to be 5-7 hours, while multiple regenerations of the supported phase transfer catalyst are performed simultaneously.

[0020] Compared with the prior art, the beneficial effects of the present invention are as follows: the method for synthesizing 2-aminopyridine uses polymer resin microspheres as a carrier to graft a preferred highly active phase transfer catalyst molecule—N,N-dimethylaniline—to synthesize a supported phase transfer catalyst, thereby achieving efficient recycling and regeneration of the phase transfer catalyst. The supported phase transfer catalyst also ensures the yield of pyridine amination products, which is beneficial to ensuring the efficient resource utilization of basic nitrogen heterocyclic compounds in coal tar. Attached Figure Description

[0021] Figure 1 This is a schematic diagram illustrating the changes in molecular structure during the grafting process of the supported phase transfer catalyst of this invention.

[0022] Figure 2 This is a schematic diagram of the Fourier transform infrared spectrum of the phase transfer catalyst before and after immobilization in this invention.

[0023] Figure 3 This is a schematic diagram of the physical adsorption-desorption isotherms of the phase transfer catalyst before and after immobilization according to the present invention.

[0024] Figure 4 This is a schematic diagram of the pore size distribution of the supported phase transfer catalyst of the present invention;

[0025] Figure 5 This is a graph showing the relevant data on the pore volume and specific surface area of ​​the phase transfer catalyst of this invention;

[0026] Figure 6 This is a diagram showing the results of multiple cycles of the supported phase transfer catalyst of this invention;

[0027] Figure 7 This is a graph showing the relevant data on the pore volume and specific surface area of ​​the phase transfer catalyst before and after the cycle of this invention.

[0028] Figure 8This is a pore size distribution diagram of the supported phase transfer catalyst of the present invention before and after cyclic reaction. Detailed Implementation

[0029] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention. Example

[0030] Please see Figure 1-8 The technical solution of this invention: a method for synthesizing 2-aminopyridine, comprising the following steps:

[0031] Step 1: Using polystyrene resin microspheres as a carrier and a mixed solvent of 1,2-dichloroethane and anhydrous ethanol as a pore-forming agent, the polystyrene resin microspheres and the mixed solvent were added to a flask and swollen for 11 hours.

[0032] Step 2: Add N,N-dimethylaniline to the flask and reflux the mixture at 50°C for 11 hours with stirring.

[0033] Step 3: The mixture in the flask was repeatedly washed with anhydrous ethanol and filtered, and finally dried under vacuum at room temperature for 5 hours to obtain a supported phase transfer catalyst grafted N,N-dimethylaniline onto polystyrene resin.

[0034] Step 4: Mix and stir the crushed sodium amide (NaNH2) solid, organic solvent and supported phase transfer catalyst, heat to 100℃, then slowly add pyridine dropwise. After the addition is complete, reflux for 3 hours, then cool to 70℃ and add water. Hydrolyze at a constant temperature for 0.3 hours, and finally cool and filter to obtain the product 2-aminopyridine. The organic solvent is a chain hydrocarbon such as dodecane or n-decane, an aromatic hydrocarbon such as tetrahydronaphthalene or decahydronaphthalene, and one of benzene, toluene, xylene or N,N-dimethylformamide.

[0035] Step 5: Use anhydrous ethanol as a solvent to wash away the organic molecules of reactants adsorbed on the surface and inside the supported phase transfer catalyst, use dilute hydrochloric acid to wash away the metal salt ions adsorbed on the surface and inside, and then repeatedly wash with ultrapure water until neutral. Finally, vacuum dry at room temperature for 5 hours to complete one regeneration of the supported phase transfer catalyst. Multiple regenerations of the supported phase transfer catalyst can be performed simultaneously. Example

[0036] Please see Figure 1-8 The technical solution of this invention: a method for synthesizing 2-aminopyridine, comprising the following steps:

[0037] Step 1: Using polystyrene resin microspheres as a carrier and a mixed solvent of 1,2-dichloroethane and anhydrous ethanol as a pore-forming agent, the polystyrene resin microspheres and the mixed solvent were added to a flask and swollen for 11 hours.

[0038] Step 2: Add N,N-dimethylaniline to the flask and reflux the mixture at 55°C for 11.5 hours with stirring.

[0039] Step 3: The mixture in the flask was repeatedly washed with anhydrous ethanol and filtered, and finally dried under vacuum at room temperature for 5 hours to obtain a supported phase transfer catalyst grafted N,N-dimethylaniline onto polystyrene resin.

[0040] Step 4: Mix and stir the crushed sodium amino 2 (NaNH2) solid, organic solvent and supported phase transfer catalyst, heat to 100℃, then slowly add pyridine dropwise. After the addition is complete, reflux for 3.5 h, then cool to 70℃ and add water. Hydrolyze at a constant temperature for 0.4 h, and finally cool and filter to obtain the product 2-aminopyridine. The organic solvent is a chain hydrocarbon such as dodecane or n-decane, an aromatic hydrocarbon such as tetrahydronaphthalene or decahydronaphthalene, and one of benzene, toluene, xylene or N,N-dimethylformamide.

[0041] Step 5: Use anhydrous ethanol as a solvent to wash away the organic molecules of reactants adsorbed on the surface and inside the supported phase transfer catalyst, use dilute hydrochloric acid to wash away the metal salt ions adsorbed on the surface and inside, and then repeatedly wash with ultrapure water until neutral. Finally, vacuum dry at room temperature for 5.5 hours to complete one regeneration of the supported phase transfer catalyst. Multiple regenerations of the supported phase transfer catalyst can be performed simultaneously. Example

[0042] Please see Figure 1-8 The technical solution of this invention: a method for synthesizing 2-aminopyridine, comprising the following steps:

[0043] Step 1: Using polystyrene resin microspheres as a carrier and a mixed solvent of 1,2-dichloroethane and anhydrous ethanol as a pore-forming agent, the polystyrene resin microspheres and the mixed solvent were added to a flask and swollen for 12 hours.

[0044] Step 2: Add N,N-dimethylaniline to the flask and reflux the mixture at 55°C for 11.5 hours with stirring.

[0045] Step 3: The mixture in the flask was repeatedly washed with anhydrous ethanol and filtered, and finally dried under vacuum at room temperature for 6 hours to obtain a supported phase transfer catalyst grafted N,N-dimethylaniline onto polystyrene resin.

[0046] Step 4: Mix and stir the crushed sodium amino 2 (NaNH2) solid, organic solvent and supported phase transfer catalyst, heat to 105℃, then slowly add pyridine dropwise. After the addition is complete, reflux for 4 h, then cool to 70℃ and add water. Hydrolyze at constant temperature for 0.4 h, and finally cool and filter to obtain the product 2-aminopyridine. The organic solvent is a chain hydrocarbon such as dodecane or n-decane, an aromatic hydrocarbon such as tetrahydronaphthalene or decahydronaphthalene, and one of benzene, toluene, xylene or N,N-dimethylformamide.

[0047] Step 5: Use anhydrous ethanol as a solvent to wash away the organic molecules of reactants adsorbed on the surface and inside the supported phase transfer catalyst, use dilute hydrochloric acid to wash away the metal salt ions adsorbed on the surface and inside, and then repeatedly wash with ultrapure water until neutral. Finally, vacuum dry at room temperature for 6 hours to complete one regeneration of the supported phase transfer catalyst. Multiple regenerations of the supported phase transfer catalyst can be performed simultaneously. Example

[0048] Please see Figure 1-8 The technical solution of this invention: a method for synthesizing 2-aminopyridine, comprising the following steps:

[0049] Step 1: Using polystyrene resin microspheres as a carrier and a mixed solvent of 1,2-dichloroethane and anhydrous ethanol as a pore-forming agent, the polystyrene resin microspheres and the mixed solvent were added to a flask and swollen for 12 hours.

[0050] Step 2: Add N,N-dimethylaniline to the flask and reflux the mixture at 60°C for 12 hours with stirring.

[0051] Step 3: The mixture in the flask was repeatedly washed with anhydrous ethanol and filtered, and finally dried under vacuum at room temperature for 6 hours to obtain a supported phase transfer catalyst grafted N,N-dimethylaniline onto polystyrene resin.

[0052] Step 4: Mix and stir the crushed sodium amino 2 (NaNH2) solid, organic solvent and supported phase transfer catalyst, heat to 105℃, then slowly add pyridine dropwise. After the addition is complete, reflux for 5 h, then cool to 70℃ and add water. Hydrolyze at constant temperature for 0.5 h, and finally cool and filter to obtain the product 2-aminopyridine. The organic solvent is a chain hydrocarbon such as dodecane or n-decane, an aromatic hydrocarbon such as tetrahydronaphthalene or decahydronaphthalene, and one of benzene, toluene, xylene or N,N-dimethylformamide.

[0053] Step 5: Use anhydrous ethanol as a solvent to wash away the organic molecules of reactants adsorbed on the surface and inside the supported phase transfer catalyst, use dilute hydrochloric acid to wash away the metal salt ions adsorbed on the surface and inside, and then repeatedly wash with ultrapure water until neutral. Finally, vacuum dry at room temperature for 6 hours to complete one regeneration of the supported phase transfer catalyst. Multiple regenerations of the supported phase transfer catalyst can be performed simultaneously. Example

[0054] Please see Figure 1-8 The technical solution of this invention: a method for synthesizing 2-aminopyridine, comprising the following steps:

[0055] Step 1: Using polystyrene resin microspheres as a carrier and a mixed solvent of 1,2-dichloroethane and anhydrous ethanol as a pore-forming agent, the polystyrene resin microspheres and the mixed solvent were added to a flask and swollen for 12 hours.

[0056] Step 2: Add N,N-dimethylaniline to the flask and reflux the mixture at 65°C for 13 hours with stirring.

[0057] Step 3: The mixture in the flask was repeatedly washed with anhydrous ethanol and filtered, and finally dried under vacuum at room temperature for 6 hours to obtain a supported phase transfer catalyst grafted N,N-dimethylaniline onto polystyrene resin.

[0058] Step 4: Mix and stir the crushed sodium amino 2 (NaNH2) solid, organic solvent and supported phase transfer catalyst, heat to 110℃, then slowly add pyridine dropwise. After the addition is complete, reflux for 5 h, then cool to 70℃ and add water. Hydrolyze at constant temperature for 0.6 h, and finally cool and filter to obtain the product 2-aminopyridine. The organic solvent is a chain hydrocarbon such as dodecane or n-decane, an aromatic hydrocarbon such as tetrahydronaphthalene or decahydronaphthalene, and one of benzene, toluene, xylene or N,N-dimethylformamide.

[0059] Step 5: Use anhydrous ethanol as a solvent to wash away the organic molecules of reactants adsorbed on the surface and inside the supported phase transfer catalyst, use dilute hydrochloric acid to wash away the metal salt ions adsorbed on the surface and inside, and then repeatedly wash with ultrapure water until neutral. Finally, vacuum dry at room temperature for 6 hours to complete one regeneration of the supported phase transfer catalyst. Multiple regenerations of the supported phase transfer catalyst can be performed simultaneously. Example

[0060] Please see Figure 1-8 The technical solution of this invention: a method for synthesizing 2-aminopyridine, comprising the following steps:

[0061] Step 1: Using polystyrene resin microspheres as a carrier and a mixed solvent of 1,2-dichloroethane and anhydrous ethanol as a pore-forming agent, the polystyrene resin microspheres and the mixed solvent were added to a flask and swollen for 13 hours.

[0062] Step 2: Add N,N-dimethylaniline to the flask and reflux the mixture at 70°C for 13 hours with stirring.

[0063] Step 3: The mixture in the flask was repeatedly washed with anhydrous ethanol and filtered, and finally dried under vacuum at room temperature for 7 hours to obtain a supported phase transfer catalyst grafted N,N-dimethylaniline onto polystyrene resin.

[0064] Step 4: Mix and stir the crushed sodium amide (NaNH2) solid, organic solvent and supported phase transfer catalyst, heat to 120℃, then slowly add pyridine dropwise. After the addition is complete, reflux for 7 h, then cool to 70℃ and add water. Hydrolyze at constant temperature for 0.8 h, and finally cool and filter to obtain the product 2-aminopyridine. The organic solvent is a chain hydrocarbon such as dodecane or n-decane, an aromatic hydrocarbon such as tetrahydronaphthalene or decahydronaphthalene, and one of benzene, toluene, xylene or N,N-dimethylformamide.

[0065] Step 5: Use anhydrous ethanol as a solvent to wash away the organic molecules of reactants adsorbed on the surface and inside the supported phase transfer catalyst, use dilute hydrochloric acid to wash away the metal salt ions adsorbed on the surface and inside, and then repeatedly wash with ultrapure water until neutral. Finally, vacuum dry at room temperature for 7 hours to complete one regeneration of the supported phase transfer catalyst. Multiple regenerations of the supported phase transfer catalyst can be performed simultaneously.

[0066] The composition and structure of the prepared supported phase transfer catalyst were analyzed. First, infrared spectroscopy was used to compare the resin microspheres before and after grafting. Figure 2 As can be seen, new peaks appear at 3203 cm⁻¹ and 1371 cm⁻¹, which are characteristic absorptions of methyl-CH₃ (from N,N-dimethylaniline reagent). The characteristic absorptions of methyl chloride-CH₂Cl on the side chain of the polymer resin molecule at 1423 cm⁻¹ and 685 cm⁻¹ are significantly weakened. These changes indicate that the chloromethyl group on the side chain of the resin macromolecule has undergone quaternization reaction with N,N-dimethylaniline, and the desired supported phase transfer catalyst has been synthesized.

[0067] Next, physical adsorption and scanning electron microscopy were used to characterize the resin microspheres before and after grafting the phase transfer catalyst, respectively. The analysis revealed that the spherical particles of the supported phase transfer catalyst have larger mesopores within their internal structure. Figure 3 As shown, this is more conducive to mass transfer in the reaction, accelerates the reaction rate, and is due to Figure 4It can be seen that the distribution of pore size before and after fixation is close to the number of pores;

[0068] The prepared supported phase transfer catalyst was analyzed for parameters such as pore volume and specific surface area. Figure 5 As shown, before and after the fixation, the pore volume and specific surface area increased slightly, but the changes were not significant.

[0069] The results of multiple regeneration and cyclic reactions of the supported phase transfer catalyst are as follows: Figure 6 As shown, the selectivity can be stabilized at around 96% after 6 cycles of reaction, and the product yield obtained in the first 5 cycles is around 53%, which remains basically unchanged, indicating that the catalyst has relatively stable catalytic activity.

[0070] While utilizing the regenerated supported phase transfer catalyst in cyclic reactions, the structural changes of the catalyst before and after six cycles were investigated. Figure 7 A comparison of the data shows that the pore volume and specific surface area of ​​the supported phase transfer catalyst slightly decrease before and after the cyclic reaction. Figure 8 It can be seen that after multiple cycles, the difference in pore size distribution is not significant, but the number of pores decreases.

[0071] Immobilizing the phase transfer catalyst solves the problem of difficult catalyst recovery. After five cycles of regeneration reaction, the catalytic activity remains relatively stable, and the product yield is about 53%. After six cycles of reaction, the selectivity remains stable at 96%.

[0072] The contents not described in detail in this specification are existing technologies known to those skilled in the art.

[0073] While embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions, and variations may be made to these embodiments without departing from the principles and spirit of the invention, and that the scope of the invention is defined by the appended claims and their equivalents.

Claims

1. A method for synthesizing 2-aminopyridine, characterized in that, Includes the following steps: Step 1: Using polystyrene resin microspheres as a carrier and a mixed solvent of 1,2-dichloroethane and anhydrous ethanol as a pore-forming agent, the polystyrene resin microspheres and the mixed solvent are added to a flask for swelling. Step 2: Add N,N-dimethylaniline to the flask and stir under reflux for reaction; Step 3: The mixture in the flask is repeatedly washed with anhydrous ethanol and filtered, and finally dried under vacuum at room temperature to obtain a supported phase transfer catalyst grafted with N,N-dimethylaniline onto polystyrene resin. Step 4: Mix and stir the crushed sodium amino acid (NaNH2) solid, organic solvent and supported phase transfer catalyst to the reaction temperature, then slowly add pyridine dropwise. After the addition is complete, reflux the reaction, cool down and add water, hydrolyze at a constant temperature, and finally cool and filter to obtain the product 2-aminopyridine. Step 5: Use anhydrous ethanol as a solvent to wash away the organic molecules of reactants adsorbed on the surface and inside the supported phase transfer catalyst, use dilute hydrochloric acid to wash away the metal salt ions adsorbed on the surface and inside, then repeatedly wash with ultrapure water until neutral, and finally perform vacuum drying at room temperature to complete the regeneration of the supported phase transfer catalyst.

2. The method for synthesizing 2-aminopyridine according to claim 1, characterized in that, In step one, the polystyrene resin microspheres swell with the mixed solvent for 11-13 hours.

3. The method for synthesizing 2-aminopyridine according to claim 2, characterized in that, In step two, the stirring temperature is controlled at 50-70℃, and the stirring time is 11-13 hours.

4. The method for synthesizing 2-aminopyridine according to claim 3, characterized in that, The vacuum drying time in step three is 5-7 hours.

5. The method for synthesizing 2-aminopyridine according to claim 4, characterized in that, The organic solvent in step four is one of dodecane, n-decane, tetrahydronaphthalene, decahydronaphthalene, benzene, toluene, xylene, or N,N-dimethylformamide.

6. The method for synthesizing 2-aminopyridine according to claim 5, characterized in that, In step four, powdered sodium amide (NaNH2) solid, organic solvent and supported phase transfer catalyst are mixed and stirred and heated to 100-120℃. After adding pyridine dropwise, the mixture is refluxed for 3-7 h. After reflux, the mixture is cooled to 70℃ and water is added for constant-temperature hydrolysis for 0.3-0.8 h.

7. The method for synthesizing 2-aminopyridine according to claim 6, characterized in that, In step five, the vacuum drying time is controlled to be 5-7 hours, while multiple regenerations of the supported phase transfer catalyst are performed simultaneously.

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