A process for the preparation of 1,4-dioxane-2-one

Abstract

The application discloses a preparation method of 1,4-dioxane-2-one. The preparation method of 1,4-dioxane-2-one comprises the following steps: taking diethylene glycol as raw material, and reacting in a solvent in the presence of a nitrogen-oxygen free radical catalyst, a chlorine source oxidant and an alkaline substance to obtain 1,4-dioxane-2-one. The preparation method of 1,4-dioxane-2-one does not need to add any acidic substance auxiliary agent, the reaction system is mild, the process is simple, the chlorine source oxidant can be recycled and used, and the yield is high, the cost is low, the method is green and environment-friendly, and the method provides a new method and a path for large-scale industrial production of 1,4-dioxane-2-one.

Description

Technical Field

[0001] This application relates to the field of 1,4-dioxane-2-one preparation technology, and in particular to a method for preparing 1,4-dioxane-2-one. Background Technology

[0002] Poly(p-dioxanone) (PPDO) is an important aliphatic polyester material. PPDO's unique alternating polyester-polyether structure endows it with excellent biocompatibility, complete biodegradability, good mechanical properties, and high hydrophilicity. This polymer is widely used in absorbable surgical sutures, implantable medical devices, tissue engineering scaffolds, drug delivery systems, fully biodegradable plastics, environmentally friendly agricultural films, pharmaceutical intermediates, and high-performance biodegradable polymer modification, making it a core raw material for the biopharmaceutical, green materials, and high-end fine chemical industries.

[0003] The preparation of high-quality, high-molecular-weight PPDO relies on high-purity 1,4-dioxane-2-one (also known as p-dioxane-2-one, PDO) monomer. Traditional organic synthesis methods for PDO suffer from drawbacks such as complex processes, demanding conditions, and low yields, making industrial-scale production difficult. In recent years, methods for preparing PDO from diethylene glycol (DEG) have received considerable attention. Patents US2807629 and US2900395 disclose methods for synthesizing PDO through copper and chromium-catalyzed dehydrogenation of diethylene glycol, but these methods require high-temperature conditions of 240–360 °C and yield only 25% pure PDO. Patent document CN112724122A discloses a method for preparing PDO from diethylene glycol using metals such as ruthenium, palladium, iridium, chromium, and copper supported on an apatite-based carrier. This reaction requires harsh conditions, including high temperatures of 150–250 °C and high pressures of 0.1–2 MPa, and the use of some precious metals as catalysts significantly increases the reaction cost. Patent document CN119684253A discloses a method for preparing PDO from diethylene glycol using copper-silicon catalysts. While this method yields high-yield and high-purity PDO, the catalyst preparation is cumbersome.

[0004] Patent document CN119684253A discloses a method for preparing p-dioxanone from diethylene glycol. This method uses 2,2,6,6-tetramethylpiperidine (TEMPO) as a catalyst and trichloroisocyanuric acid (TCCA) as an oxidant. The reaction must be carried out under acidic conditions and inert gas protection, relying on acidic auxiliaries such as nitromethane, hexafluoroisopropanol, and benzoic acid to improve the reaction yield. This process has significant drawbacks: the acidic system is highly corrosive, the acidic auxiliaries are costly, the reaction time is long (16-28 hours), and post-treatment requires quenching with sodium thiosulfate. The process is complex and difficult to scale up for low-cost industrial production.

[0005] In summary, how to achieve the preparation of 1,4-dioxane-2-one with mild reaction conditions, high yield, low cost, and environmental friendliness remains a key research focus and challenge in this field. Summary of the Invention

[0006] The purpose of this application is to provide an improved method for preparing 1,4-dioxane-2-one.

[0007] To achieve the above objectives, this application adopts the following technical solution:

[0008] This application discloses a method for preparing 1,4-dioxane-2-one, comprising reacting diethylene glycol as a raw material in a solvent in the presence of a nitric oxide free radical catalyst, a chlorine source oxidant and an alkaline substance to obtain 1,4-dioxane-2-one; wherein no acidic substances are added to the reaction.

[0009] It should be noted that this application's inventive research has discovered that using diethylene glycol as a raw material, along with a nitric oxide radical catalyst and a chlorine source oxidant, enables more efficient synthesis of 1,4-dioxane-2-one in an alkaline reaction system. In some implementations, the yield of this application's preparation method can reach up to 95%, with a minimum yield greater than or equal to 82%, and a maximum purity greater than 99%. Compared to reactions under acidic conditions, this application's preparation method requires no addition of any acidic auxiliaries, features mild reaction conditions, and simplifies post-processing, offering advantages such as high yield, low cost, and environmental friendliness. Furthermore, in this application's preparation method, the chlorine source oxidant can be recycled through alkali dissolution and chlorination, significantly reducing raw material costs and waste emissions, making it suitable for industrial production.

[0010] It should also be noted that existing reactions conducted under acidic conditions often result in numerous impurities after the addition of sodium thiosulfate, leading to low purity and extremely low recycling rates of the chlorine source oxidant, thus lacking industrial value. The preparation method described in this application involves alkali dissolution and chlorination regeneration of the chlorine source oxidant after the reaction. In some implementations, the single-cycle recycling rate of the chlorine source oxidant is ≥80%. The regeneration and recycling method is simple and easy to operate, possessing industrial value.

[0011] In some implementations, the chlorine source oxidant is selected from at least one of sodium dichloroisocyanurate (DCCNa), trichloroisocyanuric acid (TCCA), potassium dichloroisocyanurate (DCCK), N-chlorosuccinimide (NCS), dichlorohydantoin (DCDMH), chlorobromohydantoin, sodium hypochlorite, calcium hypochlorite, and tert-butyl hypochlorite.

[0012] In some implementations, the nitroxide radical catalyst is selected from at least one of 2,2,6,6-tetramethylpiperidine (TEMPO), 4-hydroxy-TEMPO, 4-acetamido-TEMPO, 4-methoxy-TEMPO, 4-oxo-TEMPO, and salts, derivatives, or supported catalysts of these compounds.

[0013] In some implementations, the alkaline substance is selected from at least one of sodium bicarbonate, potassium bicarbonate, sodium carbonate, potassium carbonate, cesium carbonate, sodium formate, sodium acetate, potassium acetate, sodium phosphate, potassium phosphate, sodium hydroxide, potassium hydroxide, triethylamine, diisopropylethylamine, pyridine, 1,6-dimethylpyridine, N-methylmorpholine, 1,8-diazabicyclo[5.4.0]undec-7-ene (DBU), and 1,5-diazabicyclo[4.3.0]non-5-ene (DBN).

[0014] In some implementations, the solvent is selected from at least one of ethyl acetate, methyl acetate, n-propyl acetate, butyl acetate, isopropyl acetate, 1,2-dichloroethane, dichloromethane, chloroform, carbon tetrachloride, tetrahydrofuran, 2-methyltetrahydrofuran, 1,4-dioxane, diethyl ether, methyl tert-butyl ether, ethylene glycol dimethyl ether, phenyl ether, acetonitrile, acetone, water, benzene, xylene, trimethylbenzene, ethylbenzene, chlorobenzene, fluorobenzene, diethylbenzene, dichlorobenzene, n-hexane, n-pentane, and heptane.

[0015] It should be noted that in the preparation method of this application, the solvent is only used to dissolve the raw materials and does not participate in the reaction. Therefore, conventional solvents are applicable to this application, including but not limited to the solvents listed above.

[0016] In some implementations, the molar ratio of diethylene glycol to chlorine source oxidant is (1:0.5) to (1:3).

[0017] In some implementations, the amount of nitroxide radical catalyst used is 0.01% to 10% of the molar amount of diethylene glycol.

[0018] In some implementations, the molar ratio of diethylene glycol to the alkaline substance is (1:0.05) to (1:4), that is, the amount of alkali used is 0.05 to 4.0 equivalents of the molar amount of diethylene glycol.

[0019] In some implementations, the reaction temperature is -30℃ to 80℃, and the reaction time is 0.5 to 24 hours. For example, the reaction temperature is 10 to 30℃, and the reaction time is 0.5 to 2 hours.

[0020] In some implementations, the preparation method of this application specifically includes mixing diethylene glycol, a nitrile radical catalyst, an alkaline substance and a solvent, slowly adding a chlorine source oxidant in batches, and reacting under an air or inert gas atmosphere to obtain the 1,4-dioxane-2-one of this application.

[0021] In some implementations, the inert gas is at least one of nitrogen, argon, and helium.

[0022] It should be noted that the preparation method of this application can be carried out in air or in an inert gas; for example, in some implementations of this application, the 1,4-dioxane-2-one of this application can be prepared by reacting at room temperature and in air for 2 hours, without the need for high temperature, high pressure, or special atmosphere, which greatly reduces the production cost and is especially suitable for large-scale industrial production.

[0023] In some implementations, the preparation method of this application further includes filtering to remove salt residue after the reaction, concentrating the filtrate, and distilling or column chromatography the concentrate to obtain the 1,4-dioxane-2-one of this application.

[0024] In some implementations, the preparation method of this application further includes washing the filtered salt residue, adding an alkaline solution to adjust the pH to 9-12, and then chlorinating it with chlorine gas or hypochlorite to re-precipitate the chlorine source oxidant, which can then be recycled. The washing method for the salt residue includes, but is not limited to, water washing.

[0025] Due to the adoption of the above technical solutions, the beneficial effects of this application are as follows:

[0026] The method for preparing 1,4-dioxane-2-one presented in this application requires no acidic additives, has a mild reaction system, a simple process, and allows for the recycling of the chlorine source oxidant. Furthermore, it boasts high yield, low cost, and is environmentally friendly, providing a new method and approach for the large-scale industrial production of 1,4-dioxane-2-one. Attached Figure Description

[0027] Figure 1 The PDO NMR spectrum obtained in Example 1 of this application;

[0028] Figure 2 This is the NMR spectrum after reaction filtration and concentration in Example 1 of this application;

[0029] Figure 3 This is the NMR spectrum after reaction filtration and concentration in Example 2 of this application;

[0030] Figure 4 This is the NMR spectrum after reaction filtration and concentration in Example 3 of this application;

[0031] Figure 5 This is the NMR spectrum after reaction filtration and concentration in Example 4 of this application;

[0032] Figure 6 This is the NMR spectrum after reaction filtration and concentration in Example 5 of this application;

[0033] Figure 7 This is the NMR spectrum after reaction filtration and concentration in Example 6 of this application;

[0034] Figure 8 This is the NMR spectrum after reaction filtration and concentration in Example 7 of this application. Detailed Implementation

[0035] The existing publicly available method for preparing 1,4-dioxane-2-one using diethylene glycol as a raw material, 2,2,6,6-tetramethylpiperidine oxide as a catalyst, and trichloroisocyanuric acid as an oxidant requires the reaction to be carried out under acidic conditions and inert gas protection. Furthermore, it relies on acidic auxiliaries such as nitromethane, hexafluoroisopropanol, and benzoic acid to improve the reaction yield. This method suffers from drawbacks such as the strong corrosiveness of the acidic system, high cost of acidic auxiliaries, long reaction time, low oxidant recycling rate, and the need for quenching with sodium thiosulfate in post-treatment. The process is complex and difficult to scale up for low-cost industrial production.

[0036] In response to the above defects and shortcomings, this application has made an inventive discovery that by using nitric oxide radical catalysts and chlorine oxidants as raw materials, 1,4-dioxane-2-one can be synthesized more efficiently in a reaction system containing alkaline substances.

[0037] Based on the above research and findings, this application provides an improved method for preparing 1,4-dioxane-2-one, comprising reacting diethylene glycol as a raw material in a solvent in the presence of a nitric oxide free radical catalyst, a chlorine source oxidant and an alkaline substance to obtain 1,4-dioxane-2-one, without adding acidic substances to the reaction.

[0038] The chemical equation for the preparation of 1,4-dioxane-2-one from diethylene glycol in this application is as follows:

[0039]

[0040] The preparation method of this application has at least the following advantages compared with the prior art:

[0041] (1) This application uses low-cost bulk chemical diethylene glycol as raw material and obtains the target product PDO through oxidative cyclization in an alkaline system without adding any acidic substances, which is fundamentally different from the existing technology that relies on acidic additives to improve the reaction yield.

[0042] (2) The product yield of the preparation method of this application is ≥82% and the purity is ≥99%, which can meet the requirements for use in medical biodegradable materials and high-end polyester monomers.

[0043] (3) The preparation method of this application has a wide range of chlorine source oxidants that can be regenerated and recycled after the reaction, with a single regeneration recovery rate of ≥80%, which greatly reduces the cost of raw materials.

[0044] (4) The preparation method of this application has mild reaction conditions, does not require long reaction time, and does not require strict inert gas protection. The post-processing is simple, without the need for quenching, extraction and other steps, and the solvent can be directly recycled and reused, resulting in low emissions of waste. The process is simple and easy to operate, has low equipment requirements, is green and environmentally friendly, and is suitable for large-scale industrial production.

[0045] The present application will be further described in detail below through specific embodiments. These embodiments are merely illustrative and should not be construed as limiting the present application. In the following embodiments, many details are described to facilitate a better understanding of the present application. However, those skilled in the art will readily recognize that some features may be omitted in different situations, or may be replaced by other devices, materials, or methods. In some cases, certain operations related to the present application are not shown or described in the specification to avoid obscuring the core parts of the present application with excessive description. For those skilled in the art, detailed description of these related operations is not necessary; a complete understanding of the related operations can be obtained from the description in the specification and general technical knowledge in the art.

[0046] Unless otherwise specified, all experimental materials and reagents used in the following examples are commercially available. In the examples, any techniques or conditions not specifically described should be performed in accordance with the techniques or conditions described in the literature or the product instructions.

[0047] Example 1

[0048] The synthesis method of 1,4-dioxane-2-one is as follows:

[0049] Diethylene glycol (4 mmol, 424 mg), TEMPO (0.04 mmol, 6.2 mg), pyridine (0.4 mmol, 31.6 mg), and acetonitrile (10 mL) were added to a round-bottom flask and stirred to disperse. Sodium dichloroisocyanurate (4.8 mmol, 1.06 g) was added in portions, and the reaction temperature was controlled at 10–30 °C for 2 hours. After the reaction was completed, the salt residue was removed by filtration, the filtrate was concentrated, and the crude product was subjected to silica gel column chromatography (Yantai Huayang New Materials, catalog number: A-200300-P, specification: 200-300M) to obtain the product 1,4-dioxane-2-one, with a separation yield of 82% and an NMR yield of 84%.

[0050] Figure 1 The target product purified by silica gel column chromatography in this embodiment. 1 The 1H NMR spectrum showed that all hydrogen signals corresponded one-to-one with the structure of 1,4-dioxane-2-one, confirming the correct structure of the product.

[0051] Figure 2 For the quantitative 1H NMR spectrum obtained after filtration and concentration in this embodiment, 0.29 mmol of p-xylene was added as an internal standard. After acquiring the 1H NMR spectrum, the characteristic hydrogen signals of the product and the internal standard were integrated separately. Combined with the molar hydrogen atom number correction conversion, the yield of the reaction product was calculated to be 84%. The product δ 4.51-4.48 ppm (2 H); the internal standard p-xylene δ 7.11 ppm (4 H). The characteristic peaks of the product and the internal standard peaks did not overlap, and there was no interference from by-products.

[0052] Example 2

[0053] The synthesis method of 1,4-dioxane-2-one is as follows:

[0054] Diethylene glycol (4 mmol, 424 mg), TEMPO (0.04 mmol, 6.2 mg), sodium bicarbonate (0.4 mmol, 33.6 mg), and acetonitrile (10 mL) were added to a round-bottom flask and stirred to disperse. Sodium dichloroisocyanurate (4.8 mmol, 1.06 g) was added in portions, and the reaction temperature was controlled at 10–30 °C for 2 hours. After the reaction was completed, the salt residue was removed by filtration, the filtrate was concentrated, and the crude product was subjected to silica gel column chromatography to obtain the product 1,4-dioxane-2-one, with a separation yield of 85% and an NMR yield of 87%.

[0055] Figure 3 For the quantitative 1H NMR spectrum after filtration and concentration in this embodiment, 0.30 mmol of p-xylene was added as an internal standard. The NMR yield was calculated using the same integration correction method as in Example 1, with no overlap between the product characteristic peak and the internal standard peak, and no interference from byproducts.

[0056] Example 3

[0057] The synthesis method of 1,4-dioxane-2-one is as follows:

[0058] Diethylene glycol (4 mmol, 424 mg), TEMPO (0.04 mmol, 6.2 mg), sodium bicarbonate (4.4 mmol, 369.6 mg), and acetonitrile (10 mL) were added to a round-bottom flask and stirred to disperse. Sodium dichloroisocyanurate (4.8 mmol, 1.06 g) was added in portions, and the reaction temperature was controlled at 10–30 °C for 2 hours. After the reaction was completed, the salt residue was removed by filtration, the filtrate was concentrated, and the crude product was subjected to silica gel column chromatography to obtain the product 1,4-dioxane-2-one, with a separation yield of 95% and an NMR yield of 98%.

[0059] Figure 4For the quantitative 1H NMR spectrum obtained after filtration and concentration in this embodiment, 0.30 mmol of trimethoxybenzene was added as an internal standard. The NMR yield was calculated using the same integration and correction method as in Example 1, with a yield of 98%. The product δ was 4.51-4.48 ppm (2H), and the internal standard trimethoxybenzene δ was 6.09 ppm (3H). The characteristic peaks of the product and the internal standard peaks did not overlap, and there was no interference from byproducts.

[0060] Example 4

[0061] The synthesis method of 1,4-dioxane-2-one is as follows:

[0062] Diethylene glycol (4 mmol, 424 mg), TEMPO (0.04 mmol, 6.2 mg), sodium bicarbonate (4.4 mmol, 369.6 mg), and acetonitrile (10 mL) were added to a round-bottom flask and stirred to disperse. Trichloroisocyanuric acid (4 mmol, 0.93 g) was added in portions, and the reaction temperature was controlled at 10–30 °C for 2 hours. After the reaction was completed, the salt residue was removed by filtration, and the filtrate was concentrated. The NMR yield was 97%.

[0063] Figure 5 For the quantitative 1H NMR spectrum obtained after filtration and concentration in this embodiment, 0.30 mmol of p-xylene was added as an internal standard. The NMR yield was calculated using the same integration correction method as in Example 1, with no overlap between the product characteristic peak and the internal standard peak, and no interference from byproducts.

[0064] Example 5

[0065] The synthesis method of 1,4-dioxane-2-one is as follows:

[0066] Diethylene glycol (4 mmol, 424 mg), 4-hydroxy-TEMPO (0.04 mmol, 6.9 mg), sodium bicarbonate (4.4 mmol, 369.6 mg), and acetonitrile (10 mL) were added to a round-bottom flask and stirred to disperse. Sodium dichloroisocyanurate (4.8 mmol, 1.06 g) was added in portions, and the reaction temperature was controlled at 10–30 °C for 2 hours. After the reaction was completed, the salt residue was removed by filtration, and the filtrate was concentrated. The NMR yield was 97%.

[0067] Figure 6 For the quantitative 1H NMR spectrum obtained after filtration and concentration in this embodiment, 0.30 mmol of p-xylene was added as an internal standard. The NMR yield was calculated using the same integration correction method as in Example 1, with no overlap between the product characteristic peak and the internal standard peak, and no interference from byproducts.

[0068] Example 6

[0069] The synthesis method of 1,4-dioxane-2-one is as follows:

[0070] Diethylene glycol (4 mmol, 424 mg), TEMPO (0.04 mmol, 6.2 mg), sodium carbonate (2.2 mmol, 233 mg), and acetonitrile (10 mL) were added to a round-bottom flask and stirred to disperse. Sodium dichloroisocyanurate (4.8 mmol, 1.06 g) was added in portions, and the reaction temperature was controlled at 10–30 °C for 2 hours. After the reaction was completed, the salt residue was removed by filtration, and the filtrate was concentrated. The NMR yield was 83%.

[0071] Figure 7 For the quantitative 1H NMR spectrum obtained after filtration and concentration in this embodiment, 0.30 mmol of p-xylene was added as an internal standard. The NMR yield was calculated using the same integration correction method as in Example 1, with no overlap between the product characteristic peak and the internal standard peak, and no interference from byproducts.

[0072] Example 7

[0073] The synthesis method of 1,4-dioxane-2-one is as follows:

[0074] Diethylene glycol (4 mmol, 424 mg), TEMPO (0.04 mmol, 6.2 mg), sodium bicarbonate (4.4 mmol, 33.6 mg), and 1,2-dichloroethane (10 mL) were added to a round-bottom flask and stirred to disperse. Sodium dichloroisocyanurate (4.8 mmol, 1.06 g) was added in portions, and the reaction temperature was controlled at 10–30 °C for 2 hours. After the reaction was completed, the salt residue was removed by filtration, and the filtrate was concentrated. The NMR yield was 95%.

[0075] Figure 8 For the quantitative 1H NMR spectrum after filtration and concentration in this embodiment, 0.30 mmol of p-xylene was added as an internal standard. The NMR yield was calculated using the same integration correction method as in Example 1, with no overlap between the product characteristic peak and the internal standard peak, and no interference from byproducts.

[0076] Example 8

[0077] The synthesis method of 1,4-dioxane-2-one is as follows:

[0078] Diethylene glycol (400 mmol, 42.4 g), TEMPO (4 mmol, 62 mg), sodium bicarbonate (440 mmol, 36.9 g), and 1,2-dichloroethane (300 mL) were added to a round-bottom flask and stirred to disperse. Sodium dichloroisocyanurate (480 mmol, 106 g) was added in portions, and the reaction temperature was controlled at 10–30 °C for 2 hours. After the reaction was completed, the salt residue was removed by filtration, the filtrate was concentrated, and the crude product was distilled under reduced pressure to obtain 37.9 g of 1,4-dioxane-2-one, with a yield of 93%.

[0079] This embodiment scales up the feed scale by 100 times, and the product yield still reaches 93%, indicating that this process has the potential for industrial-scale expansion.

[0080] Example 9

[0081] The regeneration and recycling of the chlorine source oxidant involves the following steps:

[0082] The salt residue obtained from the filtration in Example 8 was slurried and washed with water. The filter cake was adjusted to pH 10.5 with sodium hydroxide solution and cooled to 10 °C. Chlorine gas was slowly introduced until the pH reached 4.8-5.2. The filter cake was then filtered, washed with water, and dried to obtain regenerated DCCNa. The single regeneration recovery rate was 82%.

[0083] The regenerated DCCNa was recycled for the synthesis of 1,4-dioxane-2-one as in Example 8. The yield of the final product, 1,4-dioxane-2-one, was 94%, which was basically the same as that of fresh DCCNa oxidant, indicating that the regenerated DCCNa in this example can be recycled.

[0084] Comparative Example 10

[0085] The synthesis of 1,4-dioxane-2-one is illustrated in this example, which compares reactions that do not use basic substances. The specific steps are as follows:

[0086] Diethylene glycol (4 mmol, 424 mg), TEMPO (0.04 mmol, 6.2 mg), and acetonitrile (10 mL) were added to a round-bottom flask and stirred to disperse. Sodium dichloroisocyanurate (4.8 mmol, 1.06 g) was added in portions, and the reaction temperature was controlled at 10–30 °C for 2 hours. After the reaction was completed, the salt residue was removed by filtration, and the filtrate was concentrated. The yield was 29% as determined by quantitative 1H NMR using p-xylene internal standard.

[0087] The above examples show that, in this application, TEMPO and 4-hydroxy-TEMPO were used as nitrile radical catalysts, DCCNa and TCCA were used as chlorine source oxidants, pyridine, sodium bicarbonate, and sodium carbonate were used as basic substances, and acetonitrile and 1,2-dichloroethane were used as solvents to conduct control experiments. All groups achieved high yields of the target product. The catalysts mentioned above are all tetramethylpiperidine nitrile radicals, the oxidants are all isocyanuric acid chlorinating agents, and all kinds of basic substances can neutralize the hydrogen chloride generated in the reaction. The solvents only play a role in dissolving and dispersing, and the mechanism of action is consistent, indicating that homologues are all suitable for the reaction system of this application. Specifically, regarding the catalyst, the catalytic core of this application is the ammonium oxygenate active species generated by the oxidation of piperidine nitric oxide radicals. The substituent at the 4-position does not determine whether the catalytic cycle can proceed. Therefore, in addition to TEMPO and 4-hydroxy-TEMPO, 4-methoxy-TEMPO, AZADO, 4-acetamido-TEMPO, 4-oxo-TEMPO, and their salts, derivatives, and supported catalysts can all be used in this method, resulting in a wide range of applicable catalysts. Similarly, isocyanuric acid chlorinating agents with the same working principle, such as sodium dichloroisocyanurate (DCCNa), trichloroisocyanuric acid (TCCA), potassium dichloroisocyanurate (DCCK), N-chlorosuccinimide (NCS), dichlorohydantoin (DCDMH), chlorobromohydantoin, sodium hypochlorite, calcium hypochlorite, and tert-butyl hypochlorite, are all suitable for this application. As for alkaline substances, they only play an auxiliary role in neutralizing hydrogen chloride and do not participate in the core oxidation ring-closing reaction. Any base that can neutralize HCl and does not initiate side reactions is applicable to this application, including but not limited to sodium bicarbonate, potassium bicarbonate, sodium carbonate, potassium carbonate, cesium carbonate, sodium formate, sodium acetate, potassium acetate, sodium phosphate, potassium phosphate, sodium hydroxide, potassium hydroxide, triethylamine, diisopropylethylamine, pyridine, 1,6-dimethylpyridine, N-methylmorpholine, 1,8-diazabicyclo[5.4.0]undec-7-ene (DBU), 1,5-diazabicyclo[4.3.0]non-5-ene (DBN), etc.

[0088] The above description, in conjunction with specific embodiments, provides a further detailed explanation of this application and should not be construed as limiting the specific implementation of this application to these descriptions. Those skilled in the art to which this application pertains can make several simple deductions or substitutions without departing from the concept of this application.

Claims

1. A method for preparing 1,4-dioxane-2-one, characterized in that: This includes reacting diethylene glycol as a raw material in a solvent in the presence of a nitric oxide free radical catalyst, a chlorine source oxidant, and a basic substance to obtain 1,4-dioxane-2-one.

2. The preparation method according to claim 1, characterized in that: The chlorine source oxidant is selected from at least one of sodium dichloroisocyanurate, trichloroisocyanuric acid, potassium dichloroisocyanurate, N-chlorosuccinimide, dichlorohydantoin, chlorobromohydantoin, sodium hypochlorite, calcium hypochlorite, and tert-butyl hypochlorite.

3. The preparation method according to claim 1, characterized in that: The nitroxide radical catalyst is selected from at least one of 2,2,6,6-tetramethylpiperidine, 4-hydroxy-TEMPO, 4-acetamido-TEMPO, 4-methoxy-TEMPO, 4-oxo-TEMPO, and salts, derivatives, and supported catalysts of these compounds.

4. The preparation method according to claim 1, characterized in that: The alkaline substance is selected from at least one of sodium bicarbonate, potassium bicarbonate, sodium carbonate, potassium carbonate, cesium carbonate, sodium formate, sodium acetate, potassium acetate, sodium phosphate, potassium phosphate, sodium hydroxide, potassium hydroxide, triethylamine, diisopropylethylamine, pyridine, 1,6-dimethylpyridine, N-methylmorpholine, 1,8-diazabicyclo[5.4.0]undec-7-ene, and 1,5-diazabicyclo[4.3.0]non-5-ene.

5. The preparation method according to claim 1, characterized in that: The solvent is selected from at least one of ethyl acetate, methyl acetate, n-propyl acetate, butyl acetate, isopropyl acetate, 1,2-dichloroethane, dichloromethane, chloroform, carbon tetrachloride, tetrahydrofuran, 2-methyltetrahydrofuran, 1,4-dioxane, diethyl ether, methyl tert-butyl ether, ethylene glycol dimethyl ether, phenyl ether, acetonitrile, acetone, water, benzene, xylene, trimethylbenzene, ethylbenzene, chlorobenzene, fluorobenzene, diethylbenzene, dichlorobenzene, n-hexane, n-pentane, and heptane.

6. The preparation method according to claim 1, characterized in that: The molar ratio of diethylene glycol to chlorine source oxidant is (1:0.5) to (1:3). Optionally, the amount of the nitrile radical catalyst is 0.01% to 10% of the molar amount of diethylene glycol; Optionally, the molar ratio of diethylene glycol to the alkaline substance is (1:0.05) to (1:4).

7. The preparation method according to claim 1, characterized in that: The reaction temperature is -30℃ to 80℃, and the reaction time is 0.5 to 24 hours.

8. The preparation method according to any one of claims 1-7, characterized in that: The method involves mixing diethylene glycol, a nitrile radical catalyst, an alkaline substance and a solvent, adding a chlorine-based oxidant, and reacting the mixture in air or an inert gas atmosphere to obtain the 1,4-dioxane-2-one. Optionally, the inert gas is at least one of nitrogen, argon, and helium.

9. The preparation method according to claim 8, characterized in that: The process also includes filtering to remove salt residue after the reaction, concentrating the filtrate, and distilling or column chromatography to obtain the 1,4-dioxane-2-one.

10. The preparation method according to claim 9, characterized in that: It also includes washing the salt residue, adding it to an alkaline solution, adjusting the pH to 9-12, and then chlorinating it with chlorine gas or hypochlorite to re-precipitate the chlorine source oxidant, which can then be recycled.

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