A method for synthesizing nitrogen-containing heterocyclic nitroxides
By using potassium persulfate complex salt and alcohol-water mixed solvent, the high cost of traditional synthesis methods has been solved, achieving safe, environmentally friendly and efficient synthesis of nitrogen oxides, which is suitable for large-scale production.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- 衢州市浙工大生态工业创新研究院
- Filing Date
- 2026-02-12
- Publication Date
- 2026-06-05
AI Technical Summary
Traditional methods for synthesizing nitrogen-containing heterocyclic nitrogen oxides suffer from high economic costs, environmental unfriendliness, and poor safety.
Potassium persulfate complex salt was used as the oxidant, and an alcohol-water mixed solvent was used to control the reaction pH between 6 and 9 to carry out the nitrogen oxidation reaction of nitrogen-containing heterocyclic compounds, avoiding the use of flammable and explosive oxidants and heavy metal catalysts.
It achieves the synthesis of nitrogen oxides with high safety, environmental friendliness, and good economy, with high yield and good selectivity, making it suitable for large-scale production.
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Figure CN122145383A_ABST
Abstract
Description
Technical Field
[0001] This invention relates to the field of organic synthesis technology, specifically to a method for synthesizing nitrogen-containing heterocyclic nitrogen oxides. Background Technology
[0002] Nitrogen-containing heterocyclic nitrogen oxides are an important class of organic compounds, characterized by the coordinate bonding of nitrogen and oxygen atoms in the nitrogen heterocycle. This structure significantly alters the physical, chemical, and biological properties of the parent molecule, leading to its wide and significant applications in various fields. In medicinal chemistry and the pharmaceutical industry, many nitrogen-containing heterocyclic nitrogen oxides are active pharmaceutical molecules or key intermediates. Quinoline nitrogen oxides themselves possess antibacterial and antifungal activities and are important building blocks for the synthesis of anti-ulcer drugs (such as omeprazole intermediates) and antitumor drugs. Pyridine nitrogen oxides are the core structure of many pesticides (such as herbicides and insecticides) and drugs. Given the importance of nitrogen-containing heterocyclic nitrogen oxides, their synthesis has been a research hotspot. Traditional and currently commonly used synthetic methods mainly rely on hydrogen peroxide systems, organic peroxyacid oxidants, and metal catalytic systems. For example, CN109776412A discloses a method for synthesizing N oxides, in which hydrogen peroxide is used as the oxidant and glacial acetic acid is used as the catalyst or additive; CN104628636A discloses a method for synthesizing pyridine heterocyclic nitrogen oxides, in which hydrogen peroxide is used as the oxidant and ammonium acetate, ammonium molybdate tetrahydrate, and hydrazine sulfate are used as the catalyst or additive; CN104974088A discloses a highly efficient, heterogeneous catalytic preparation method for pyridine nitrogen oxides, in which hydrogen peroxide is used as the oxidant and tungsten-supported titanium dioxide (WO3 / TiO2) is used as the catalyst or additive; CN110156682A discloses a method for preparing nitrogen heterocyclic N-oxides, in which peracetic acid, m-chloroperoxybenzoic acid, and peroxybenzoic acid are used as the oxidants and sodium tungstate, methylrhenium dioxide, and phosphomolybdic acid are used as the catalyst or additive.
[0003] However, traditional preparation methods have certain limitations. For example, the use of organic peroxyacid oxidants in the synthesis can be environmentally damaging; and the use of metal catalytic systems in the synthesis can increase economic costs. Therefore, this invention provides a method for synthesizing nitrogen-containing heterocyclic nitrogen oxides. Summary of the Invention
[0004] The purpose of this invention is to provide a method for synthesizing nitrogen-containing heterocyclic nitrogen oxides, so as to solve the problem of high economic cost mentioned in the background art.
[0005] To achieve the above objectives, the present invention provides the following technical solution: A method for synthesizing nitrogen-containing heterocyclic nitrogen oxides includes the following steps: S1. Select a nitrogen-containing heterocyclic compound as the reaction substrate, and place the selected nitrogen-containing heterocyclic compound in an alcohol- In a water-mixed solvent, the temperature is increased. S2. After heating, add an oxidant and add NaOH solution dropwise to maintain the pH of the reaction system between 6 and 9. Then carry out the reaction under pH 6-9 conditions. S3. After the reaction is complete, filter to obtain filtrate and filter residue; wash the filter residue with dichloromethane to obtain aqueous phase and organic phase; S4. Collect the filtrate and aqueous phase, extract with dichloromethane multiple times, combine the obtained organic phases and remove the organic solvent by rotary evaporation to obtain the crude product of nitrogen-containing heterocyclic nitrogen oxides.
[0006] Preferably, the nitrogen-containing heterocyclic compound is a pyridine-based nitrogen-containing heterocyclic compound of general formula (I), which reacts to obtain a pyridine-based nitrogen-containing heterocyclic oxynitride of general formula (III); wherein R1 in general formula (I) and general formula (III) are substituents selected from one of -CH3, -OCH3 and -H; .
[0007] Preferably, the nitrogen-containing heterocyclic compound is a quinoline-type nitrogen-containing heterocyclic compound represented by general formula (II), and the reaction yields a quinoline-type nitrogen-containing heterocyclic oxynitride represented by general formula (IV); wherein R2 and R3 in general formula (II) and general formula (IV) are homosubstituents selected from one or more of -CH3, -OCH3 and -H; .
[0008] Preferably, the nitrogen-containing heterocyclic compound is selected from pyridine, quinoline, 2-methylquinoline and 6-methoxyquinoline, with quinoline being the most preferred.
[0009] Preferably, the alcohol-water mixed solvent in step S1 is a solvent that is a mixture of an alcohol solvent and water.
[0010] Preferably, the alcohol solvent is selected from one or more of methanol, ethanol, propanol and isopropanol, with methanol being the most preferred.
[0011] Preferably, the mass ratio of alcohol solvent to water is 1:1-2, more preferably 1:1-1.5.
[0012] Preferably, the oxidant in step S2 is selected from one or more of potassium persulfate complex salt, potassium persulfate and sodium percarbonate, with potassium persulfate complex salt being the preferred choice.
[0013] Preferably, the molar ratio of the nitrogen-containing heterocyclic compound to the oxidant is 1:1-2.
[0014] Preferably, the heating temperature in step S1 is 20-70℃, more preferably 20-60℃; the reaction time in step S2 is 2-10h, more preferably 2-6h; and the dichloromethane extraction is performed 3 times in step S4.
[0015] Compared with the prior art, the beneficial effects of the present invention are: 1. High safety: The selected oxidant is stable and non-flammable and non-explosive, which greatly improves the safety of production and operation.
[0016] 2. Environmentally friendly: The oxidant byproducts are harmless, and the use of alcohol-water as a mixed solvent avoids the use of heavy metal catalysts or highly corrosive acids in traditional methods, which meets the requirements of green chemistry.
[0017] 3. Good economic efficiency: The oxidant used is inexpensive, with a cost far lower than that of reagents such as mCPBA, and the post-processing is simple, making it suitable for large-scale production.
[0018] 4. Mild conditions and good selectivity: The reaction is carried out under mild conditions, and can efficiently and selectively oxidize nitrogen on a variety of nitrogen-containing heterocyclic substrates such as quinoline, 2-methylquinoline, 6-methoxyquinoline, and pyridine, avoiding the destruction of sensitive functional groups (such as methoxy groups) and achieving high yields. Attached Figure Description
[0019] Figure 1 The liquid chromatogram of the quinoline nitrogen oxide product in Example 3; Figure 2 The liquid chromatogram of the 2-methylquinoline nitrogen oxide product in Example 9; Figure 3 The liquid chromatogram of the 6-methoxyquinoline nitrogen oxide product in Example 10; Figure 4 The liquid chromatogram of the pyridine nitrogen oxide product in Example 11; Figure 5 The quinoline nitrogen oxide product in Example 3; Figure 6 The 2-methylquinoline nitride product in Example 9; Figure 7 The product of 6-methoxyquinoline nitrogen oxides in Example 10; Figure 8 This is the pyridine nitride product from Example 11. Detailed Implementation
[0020] Example 1:
[0021] In a 250 mL three-necked flask, quinoline (4 g, 31 mmol), methanol (15 g), and water (15 g) were added sequentially. After heating the solution, potassium persulfate complex salt (19.1 g, 31 mmol) was slowly added, while simultaneously adding NaOH solution dropwise to maintain the pH of the reaction system at approximately 7. The reaction was carried out at 70 °C for 4 hours with magnetic stirring. After the reaction was complete, the resulting solid-liquid mixture was filtered, and the residue was washed with dichloromethane solution. The filtrate and aqueous phase were collected and extracted three times with dichloromethane. The organic phases were combined and the organic solvent was removed by rotary evaporation, yielding 4.4 g of crude quinoline nitrogen oxides. Liquid chromatography with external standard analysis showed a purity of 90.3%, and the yield of quinoline nitrogen oxides was calculated to be 88.3%.
[0022] Example 2:
[0023] In a 250 mL three-necked flask, quinoline (4 g, 31 mmol), methanol (20 g), and water (20 g) were added sequentially. After heating the solution, potassium persulfate complex salt (38.1 g, 62 mmol) was slowly added, while simultaneously adding NaOH solution dropwise to maintain the pH of the reaction system at approximately 7. The reaction was carried out at 20 °C for 10 hours with magnetic stirring. After the reaction was complete, the resulting solid-liquid mixture was filtered, and the residue was washed with dichloromethane solution. The filtrate and aqueous phase were collected and extracted three times with dichloromethane. The organic phases were combined and the organic solvent was removed by rotary evaporation, yielding 4.5 g of crude quinoline nitrogen oxides. Liquid chromatography with external standard analysis showed a purity of 85.3%, and the yield of quinoline nitrogen oxides was calculated to be 85.3%.
[0024] Example 3:
[0025] In a 250 mL three-necked flask, quinoline (4 g, 31 mmol), methanol (10 g), and water (15 g) were added sequentially. After heating the solution, potassium persulfate complex salt (19.1 g, 31 mmol) was slowly added, while simultaneously adding NaOH solution dropwise to maintain the pH of the reaction system at approximately 6. The reaction was carried out at 60 °C for 6 hours with magnetic stirring. After the reaction, the resulting solid-liquid mixture was filtered, and the residue was washed with dichloromethane solution. The filtrate and aqueous phase were collected and extracted three times with dichloromethane. The organic phases were combined and the organic solvent was removed by rotary evaporation, yielding 4.6 g of crude quinoline nitrogen oxides. Analysis by external standard liquid chromatography showed a purity of 93.2%, and the yield of quinoline nitrogen oxides was calculated to be 95.3%. The liquid chromatogram of the quinoline nitrogen oxides product is shown below. Figure 1 As shown, quinoline nitride products are as follows Figure 5 As shown.
[0026] Example 4:
[0027] In a 250 mL three-necked flask, quinoline (4 g, 31 mmol), methanol (10 g), and water (15 g) were added sequentially. The solution was heated, and potassium persulfate (8.4 g, 31 mmol) was slowly added while simultaneously adding NaOH solution dropwise to maintain the pH of the reaction system at approximately 9. The reaction was carried out at 40 °C for 6 hours with magnetic stirring. After the reaction was complete, the resulting solid-liquid mixture was filtered, and the residue was washed with dichloromethane solution. The filtrate and aqueous phase were collected and extracted three times with dichloromethane. The organic phases were combined and the organic solvent was removed by rotary evaporation, yielding 4.3 g of crude quinoline nitrogen oxides. Liquid chromatography with external standard analysis showed a purity of 84.8%, and the yield of quinoline nitrogen oxides was calculated to be 81.0%.
[0028] Example 5:
[0029] Quinoline (4 g, 31 mmol), methanol (15 g), and water (15 g) were added sequentially to a 250 mL three-necked flask. The solution was heated, and sodium percarbonate (9.7 g, 31 mmol) was slowly added while simultaneously adding NaOH solution dropwise to maintain the pH of the reaction system at approximately 9. The reaction was carried out at 40 °C for 6 hours with magnetic stirring. After the reaction was complete, the resulting solid-liquid mixture was filtered, and the residue was washed with dichloromethane solution. The filtrate and aqueous phase were collected and extracted three times with dichloromethane. The organic phases were combined and the organic solvent was removed by rotary evaporation, yielding 4.4 g of crude quinoline nitrogen oxides. Liquid chromatography with external standard analysis showed a purity of 73.6%, and the yield of quinoline nitrogen oxides was calculated to be 72.0%.
[0030] Example 6:
[0031] In a 250 mL three-necked flask, quinoline (4 g, 31 mmol), ethanol (15 g), and water (15 g) were added sequentially. After heating the solution, potassium persulfate complex salt (19.1 g, 31 mmol) was slowly added, while simultaneously adding NaOH solution dropwise to maintain the pH of the reaction system at approximately 7. The reaction was carried out at 40 °C for 6 hours with magnetic stirring. After the reaction was complete, the resulting solid-liquid mixture was filtered, and the residue was washed with dichloromethane solution. The filtrate and aqueous phase were collected and extracted three times with dichloromethane. The organic phases were combined and the organic solvent was removed by rotary evaporation, yielding 4.7 g of crude quinoline nitrogen oxides. Liquid chromatography with external standard analysis showed a purity of 91.1%, and the yield of quinoline nitrogen oxides was calculated to be 95.2%.
[0032] Example 7:
[0033] In a 250 mL three-necked flask, quinoline (4 g, 31 mmol), isopropanol (15 g), and water (15 g) were added sequentially. After heating the solution, potassium persulfate complex salt (19.1 g, 31 mmol) was slowly added, while simultaneously adding NaOH solution dropwise to maintain the pH of the reaction system at approximately 7. The reaction was carried out at 60 °C for 5 hours with magnetic stirring. After the reaction was complete, the resulting solid-liquid mixture was filtered, and the residue was washed with dichloromethane solution. The filtrate and aqueous phase were collected and extracted three times with dichloromethane. The organic phases were combined and the organic solvent was removed by rotary evaporation, yielding 4.4 g of crude quinoline nitrogen oxides. Liquid chromatography with external standard analysis showed a purity of 89.1%, and the yield of quinoline nitrogen oxides was calculated to be 87.1%.
[0034] Example 8:
[0035] In a 250 mL three-necked flask, quinoline (4 g, 31 mmol), methanol (10 g), and water (20 g) were added sequentially. After heating the solution, potassium persulfate complex salt (28.8 g, 47 mmol) was slowly added, while simultaneously adding NaOH solution dropwise to maintain the pH of the reaction system at approximately 9. The reaction was carried out at 70 °C for 10 hours with magnetic stirring. After the reaction was complete, the resulting solid-liquid mixture was filtered, and the residue was washed with dichloromethane solution. The filtrate and aqueous phase were collected and extracted three times with dichloromethane. The organic phases were combined and the organic solvent was removed by rotary evaporation, yielding 4.6 g of crude quinoline nitrogen oxides. Liquid chromatography with external standard analysis showed a purity of 87.1%, and the yield of quinoline nitrogen oxides was calculated to be 82.2%.
[0036] As can be seen from the above examples, when quinoline is selected as the nitrogen-containing heterocyclic compound, Example 3 has the highest purity and yield, and the effect achieved using methanol is optimal. Examples 1, 3, and 6 all have purities exceeding 90%, using methanol and ethanol as different oxidants. Example 7 uses isopropanol as the oxidant, achieving a purity of 89.1%, which is not significantly different from methanol and ethanol, providing a variety of oxidant options; this demonstrates that this combination can achieve efficient and highly selective nitrogen oxidation.
[0037] In Examples 1, 3, 6, and 7, potassium persulfate complex salt was used as an oxidant, and very high purity was obtained. This fully demonstrates the superiority of potassium persulfate complex salt in using quinoline as a reaction substrate, and it can achieve high purity and yield under various reaction conditions.
[0038] Example 9:
[0039] In a 250 mL three-necked flask, 4.4 g (31 mmol) of 2-methylquinoline, 15 g of methanol, and 15 g of water were added sequentially. After heating the solution, 19.1 g (31 mmol) of potassium persulfate complex salt was slowly added, while simultaneously adding NaOH solution dropwise to maintain the pH of the reaction system at approximately 7. The reaction was carried out at 70 °C for 6 hours with magnetic stirring. After the reaction was complete, the resulting solid-liquid mixture was filtered, and the residue was washed with dichloromethane solution. The filtrate and aqueous phase were collected and extracted three times with dichloromethane. The organic phases were combined and the organic solvent was removed by rotary evaporation, yielding 5.0 g of crude 2-methylquinoline nitrogen oxides. Analysis by external standard liquid chromatography showed a purity of 93.0%, and the yield of 2-methylquinoline nitrogen oxides was calculated to be 94.2%. The liquid chromatogram of 2-methylquinoline nitrogen oxides is shown below. Figure 2 As shown, 2-methylquinoline nitrides, such as Figure 6 As shown.
[0040] Example 9-1: Based on Example 9, methanol was replaced with isopropanol, and the purity of the product was 88.3% and the yield was 86.1%.
[0041] Example 9-2: Based on Example 9, methanol was replaced with propanol, and the purity of the product was 90.6% and the yield was 93.2%.
[0042] Example 9-3: Based on Example 9, potassium persulfate complex salt was replaced with potassium persulfate, and the purity of the product was 81.6% and the yield was 78.9%.
[0043] Example 9-4: Based on Example 9, potassium persulfate complex salt was replaced with sodium percarbonate, and the purity of the product was 73.7% and the yield was 74.5%.
[0044] In Examples 9 to 9-4, when 2-methylquinoline was used as the reaction substrate, the combination of methanol and propanol with potassium persulfate as additives could achieve a purity and yield of over 90%, providing more options for the preparation of high purity and yield.
[0045] Example 10: In a 250 mL three-necked flask, 4.9 g (31 mmol) of 6-methoxyquinoline, 15 g of methanol, and 15 g of water were added sequentially. After heating the solution, 19.1 g (31 mmol) of potassium persulfate complex salt was slowly added, while simultaneously adding NaOH solution dropwise to maintain the pH of the reaction system at approximately 7. The reaction was carried out at 70 °C for 2 hours with magnetic stirring. After the reaction, the resulting solid-liquid mixture was filtered, and the residue was washed with dichloromethane solution. The filtrate and aqueous phase were collected and extracted three times with dichloromethane. The organic phases were combined and the organic solvent was removed by rotary evaporation, yielding 5.3 g of crude 6-methoxyquinoline nitrogen oxides. Analysis by external standard liquid chromatography showed a purity of 97.1%, and the yield of 6-methoxyquinoline nitrogen oxides was calculated to be 94.8%. The liquid chromatogram of 6-methoxyquinoline nitrogen oxides is shown below. Figure 3 As shown, 6-methoxyquinoline nitrogen oxides, such as Figure 7 As shown.
[0046] Example 10-1: Based on Example 10, methanol was replaced with isopropanol, and the purity of the product was 96.6% and the yield was 94.0%.
[0047] Example 10-2: Based on Example 10, methanol was replaced with propanol, and the purity of the product was 93.9% and the yield was 92.3%.
[0048] Example 10-3: Based on Example 10, potassium persulfate complex salt was replaced with potassium persulfate, and the purity of the product was 84.5% and the yield was 89.4%.
[0049] Example 10-4: Based on Example 10, potassium persulfate complex salt was replaced with sodium percarbonate, and the purity of the product was 80.8% and the yield was 78.2%.
[0050] In Examples 10 to 10-2, when 6-methoxyquinoline was used as the reaction substrate, the yield and purity of the combined methanol, propanol, isopropanol, and potassium persulfate salt were selected as additives, and the yield and purity could reach more than 93%, even reaching 97%. In combinations of other additives, the yield and purity could basically reach more than 80%, which fully demonstrates the stability of the synthesis method of this application and can achieve high results for different reaction substrates.
[0051] Example 11: In a 250 mL three-necked flask, pyridine (2.5 g, 31 mmol), methanol (15 g), and water (15 g) were added sequentially. After heating the solution, potassium persulfate complex salt (19.1 g, 31 mmol) was slowly added, while simultaneously adding NaOH solution dropwise to maintain the pH of the reaction system at approximately 7. The reaction was carried out at 70 °C for 2 hours with magnetic stirring. After the reaction was complete, the resulting solid-liquid mixture was filtered, and the residue was washed with dichloromethane solution. The filtrate and aqueous phase were collected and extracted three times with dichloromethane. The organic phases were combined and the organic solvent was removed by rotary evaporation, yielding 2.8 g of crude pyridine nitrogen oxides. Analysis by external standard liquid chromatography showed a purity of 87.9%, and the yield of pyridine nitrogen oxides was calculated to be 83.5%. The liquid chromatogram of pyridine nitrogen oxides is shown below. Figure 4 As shown, pyridine oxynitrides are as follows Figure 8 As shown.
[0052] Example 11-1: Based on Example 11, methanol was replaced with isopropanol, and the purity of the product was 81.4% and the yield was 76.1%.
[0053] Example 11-2: Based on Example 11, methanol was replaced with propanol, and the purity of the product was 83.2% and the yield was 81.7%.
[0054] Example 11-3: Based on Example 11, potassium persulfate complex salt was replaced with potassium persulfate, and the purity of the product was 75.0% and the yield was 71.4%.
[0055] Example 11-4: Based on Example 11, potassium persulfate complex salt was replaced with sodium percarbonate, and the purity of the product was 69.8% and the yield was 73.3%.
[0056] In Examples 11 to 11-4, when pyridine is used as the reaction substrate, and methanol and propanol are selected as additives in combination with potassium persulfate, the yield and purity can still reach more than 81%, making the synthesis method of this application more universal.
[0057] As described above, quinoline, 2-methylquinoline, and 6-methoxyquinoline, when used as reaction substrates, have all achieved yields and purities exceeding 90% in various examples when synthesized with a variety of oxidants and alcohol solvents as described in this application. Using pyridine as a reaction substrate also generally achieves purities and yields exceeding 80%, enabling nitrogen-containing heterocyclic substrates to achieve nitrogen oxidation efficiently and selectively.
[0058] The oxidants and alcohol solvents selected in this application are all common and cost-effective types, especially potassium persulfate complex salt and methanol. These achieve very high yields and purity when used with the aforementioned reaction substrates, and are inexpensive, mild, and safe. Furthermore, the synthesis method described in this application is simple; by adjusting the pH and controlling the reaction temperature, the operational threshold is lowered, and it has the potential for large-scale production. All examples were carried out under mild conditions, without the need for metal catalysts or strong acids, reducing the risk of explosion. pH control (6-9) was easily achieved using NaOH solution, avoiding equipment corrosion and ensuring production safety.
[0059] Example 12: Quinoline nitrogen oxides were analyzed using a liquid chromatography system, specifically a Waters ArcHPLC system. The chromatographic column was a C18 column with a particle size of 5 μm, an inner length of 4.6 mm, a column length of 250 mm, a detection wavelength of 245 nm, a column temperature of 35 °C, a flow rate of 1 ml / min, a feed volume of 1 μl, an analysis time of 6 minutes, and a mobile phase ratio of V(methanol):V(water) = 40:60.
[0060] Pyridine nitrogen oxides were analyzed using a Waters ArcHPLC system with a C18 column (5 μm particle size, 4.6 mm inner length, 250 mm column length), a detection wavelength of 245 nm, a column temperature of 35 °C, a flow rate of 1 ml / min, a feed volume of 1 μl, an analysis time of 4 minutes, and a mobile phase ratio of V(methanol):V(water) = 40:60.
[0061] 2-Methylquinoline nitrogen oxides and 6-methoxyquinoline nitrogen oxides were analyzed using a Waters Arc HPLC system. The chromatographic column was C18 with a particle size of 5 μm, an inner length of 4.6 mm, a column length of 250 mm, a detection wavelength of 245 nm, a column temperature of 35 °C, a flow rate of 1 ml / min, a feed volume of 1 μl, an analysis time of 10 minutes, and a mobile phase ratio of V(methanol):V(water) = 40:60.
Claims
1. A method for synthesizing nitrogen-containing heterocyclic nitrogen oxides, characterized in that: Includes the following steps: S1. Mix the nitrogen-containing heterocyclic compound with an alcohol-water mixed solvent and heat the mixture. S2. After heating, add an oxidant and react under pH 6-9 conditions; S3. After the reaction is complete, filter to obtain filtrate and filter residue; wash the filter residue with dichloromethane to obtain aqueous phase and organic phase; S4. Collect the filtrate and aqueous phase, extract with dichloromethane multiple times, combine the obtained organic phases and remove the organic solvent by rotary evaporation to obtain the crude product of nitrogen-containing heterocyclic nitrogen oxides.
2. The method for synthesizing nitrogen-containing heterocyclic nitrogen oxides according to claim 1, characterized in that: The nitrogen-containing heterocyclic compound in step S1 is selected from one or more of pyridine, quinoline, 2-methylquinoline and 6-methoxyquinoline.
3. The method for synthesizing nitrogen-containing heterocyclic nitrogen oxides according to claim 1, characterized in that: The alcohol-water mixed solvent in step S1 is a solvent that is a mixture of alcohol and water.
4. The method for synthesizing nitrogen-containing heterocyclic nitrogen oxides according to claim 3, characterized in that: The alcohol solvent is selected from one or more of methanol, ethanol, propanol and isopropanol.
5. The method for synthesizing nitrogen-containing heterocyclic nitrogen oxides according to claim 3, characterized in that: The mass ratio of alcohol solvent to water is 1:1-2.
6. The method for synthesizing nitrogen-containing heterocyclic nitrogen oxides according to claim 1, characterized in that: The oxidant in step S2 is selected from one or more of potassium persulfate complex salt, potassium persulfate and sodium percarbonate.
7. The method for synthesizing nitrogen-containing heterocyclic nitrogen oxides according to claim 1, characterized in that: The molar ratio of nitrogen-containing heterocyclic compound to oxidant is 1:1-2.
8. The method for synthesizing nitrogen-containing heterocyclic nitrogen oxides according to claim 1, characterized in that: The temperature in step S1 is 20-70℃; the reaction time in step S2 is 2-10h; and the dichloromethane extraction is performed 3 times in step S4.
9. The method for synthesizing nitrogen-containing heterocyclic nitrogen oxides according to claim 1, characterized in that: In step S1, the nitrogen-containing heterocyclic compound is a pyridine-type nitrogen-containing heterocyclic compound represented by general formula (I), wherein R1 in general formula (I) is a substituent selected from one of -CH3, -OCH3 and -H; 。 10. The method for synthesizing nitrogen-containing heterocyclic nitrogen oxides according to claim 1, characterized in that: In step S1, the nitrogen-containing heterocyclic compound is a quinoline-type nitrogen-containing heterocyclic compound represented by general formula (II), wherein R2 and R3 in general formula (II) are substituents selected from one or more of -CH3, -OCH3 and -H; 。