A 3,3-bis(4-azidofurazan-3-oxomethyl)oxetane and its synthetic method

Abstract

This invention provides 3,3-di(4-azidofurazan-3-oxomethyl)oxetane and its synthesis method. The method includes: adding 3-nitro-4-hydroxyfurazan, 3,3-dibromomethyloxetane, a basic donor, and a phase transfer catalyst to a polar aprotic solvent, stirring the reaction at 60–100 °C for 0.5–4 h, then extracting, washing with water, drying, filtering, evaporating the solvent, and recrystallizing to obtain the intermediate 3,3-di(4-nitrofurazan-3-oxomethyl)oxetane; adding 3,3-di(4-nitrofurazan-3-oxomethyl)oxetane and an azide reagent to a polar aprotic solvent, stirring the reaction at room temperature for 0.5–1.5 h, then extracting, washing with water, drying, filtering, evaporating the solvent, and recrystallizing to obtain the final product. The method of this invention can completely convert the intermediate nitro-substituted product into 3,3-di(4-azidofurazan-3-oxomethyl)oxetane by controlling the reaction conditions, with high yield and high purity. The reaction route is efficient and time-saving, and is convenient for continuous industrial production.

Description

Technical Field

[0001] This invention belongs to the field of energetic materials technology, specifically relating to a 3,3-bis(4-azidofurazan-3-oxomethyl)oxetane and its synthesis method. Background Technology

[0002] The effectiveness of advanced munitions in the war on terror is undeniable. However, the existing production capacity of advanced munitions is insufficient to meet the sudden surge in demand. This has led to the development of modular energetic materials, which can be combined with other units through different processing methods to form products. These modular energetic materials possess relatively independent functions, are decomposable and recombinable, and are universally interchangeable. They can be mass-produced and manufactured in series based on standardization. Research on the design, customization, and synthesis of modular energetic materials has recently gained attention.

[0003] Oxycyclobutane, as a saturated four-membered ring ether monomer with dual active sites, can simultaneously load two energetic groups to form a polymer backbone, representing an important branch of energetic polymers with broad application prospects. Furazan compounds differ from traditional energetic compounds. On one hand, their molecular structure contains numerous CN, C=N, and N=N bonds, resulting in a high enthalpy of formation. Furthermore, the aromaticity of the furazan ring enhances the thermal stability of furazan derivatives, and the coplanarity of the furazan ring contributes to their high density. On the other hand, due to the high electronegativity of nitrogen and oxygen atoms, furazan compounds' nitrogen-heteroaromatic ring system can form benzene-like large π bonds, exhibiting insensitive and thermally stable properties. Therefore, many furazan energetic derivatives possess advantages such as high energy density, high standard enthalpy of formation (ΔHf), high nitrogen content, and excellent heat resistance. The excellent mechanical properties of oxycyclobutane polymers and the stable furazan-based energetic groups perfectly match the application requirements of modular energetic materials.

[0004] 3,3-Di(4-azidofurazan-3-oxomethyl)oxetane, an energetic monomer containing a furazan group and an oxetane moiety, possesses high energy density and shows promise as a multifunctional modular energetic material. However, existing synthetic routes using 3-azido-4-hydroxyfurazan as a starting material involve a lengthy four-step process with low yields. Furthermore, the first step, the substitution reaction, requires the sieving and purification of four byproducts, while the second step, the cyclization reaction, involves the corrosive strong acid trifluoromethanesulfonic acid and the corrosive strong base DBU. Experimental reproduction revealed that this route is cumbersome, causes severe environmental pollution, and the presence of the strong organic base DBU makes the nitro group highly susceptible to hydrolysis, ultimately resulting in low product yields and hindering practical applications. Summary of the Invention

[0005] To address the shortcomings of existing technologies, the present invention aims to provide 3,3-bis(4-azidofuzan-3-oxomethyl)oxetane and its synthesis method, thereby solving the technical problems of lengthy preparation steps and low yield of 3,3-bis(4-azidofuzan-3-oxomethyl)oxetane in existing technologies.

[0006] To solve the above-mentioned technical problems, the present invention adopts the following technical solution:

[0007] A method for synthesizing 3,3-bis(4-azidofurazan-3-oxomethyl)oxetane, the method comprising the following steps:

[0008] Step 1: 3-Nitro-4-hydroxyfurazan, 3,3-dibromomethyloxetane, a basic donor and a phase transfer catalyst are added to a polar aprotic solvent and stirred at 60-100°C for 0.5-4 hours. Then, the mixture is extracted, washed with water, dried, filtered, the solvent is evaporated and recrystallized to obtain the intermediate 3,3-di(4-nitrofurazan-3-oxomethyl)oxetane.

[0009] Step 2: The intermediate 3,3-bis(4-nitrofuran-3-oxomethyl)oxetane obtained in Step 1 and the azide reagent are added to a polar aprotic solvent and stirred at room temperature for 0.5-1.5 h. Then, the mixture is extracted, washed with water, dried, filtered, the solvent is evaporated, and recrystallized to obtain the final product.

[0010] The present invention also has the following technical features:

[0011] Specifically, the alkaline donors mentioned in step 1 include anhydrous potassium carbonate, cesium carbonate, and iron hydroxide.

[0012] Furthermore, the phase transfer catalyst described in step 1 includes tetrabutylammonium bromide, benzyltriethylammonium chloride, methyltrialkylammonium chloride, and 18-crown ether-6.

[0013] Furthermore, in step 1, the molar ratio of 3,3-dibromomethyloxetane to 3-nitro-4-hydroxyfurazan is 1:(2-3.5).

[0014] Furthermore, in step 1, the molar ratio of 3-nitro-4-hydroxyfurazan to the basic donor is 1:(1.5-3).

[0015] Furthermore, the azide reagent in step 2 includes sodium azide, trimethyl azidosilane, p-toluenesulfonyl azide, ethyl azide, tetrabutylammonium azide, and tri-n-butyltin azide.

[0016] Furthermore, in step 2, the molar ratio of intermediate 3,3-bis(4-nitrofuran-3-oxomethyl)oxetane to the azide reagent is 1:(2.5-3.5).

[0017] Furthermore, the polar aprotic solvents include DMF, MeCN, Acetone, and DMSO.

[0018] This invention also protects the 3,3-bis(4-azidofurazan-3-oxomethyl)oxetane prepared by the above-described synthetic method.

[0019] Compared with the prior art, the present invention has the following technical effects:

[0020] (I) The synthesis method of this invention uses readily available and inexpensive 3-nitro-4-hydroxyfurazan and commercially available 3,3-dibromomethyloxetane as raw materials. In an alkaline solvent system and in the presence of a catalytically applied phase transfer catalyst, heating yields 3,3-di(4-nitrofurazan-3-oxomethyl)oxetane. Subsequently, reaction with sodium azide in DMF solvent yields the final product, 3,3-di(4-azidofurazan-3-oxomethyl)oxetane. The method of this invention utilizes readily available raw materials, employs simple reaction conditions, and causes minimal environmental pollution.

[0021] (2) The synthesis method of the present invention can completely convert the intermediate nitro-substituted product into the azide-substituted product 3,3-bis(4-azidofurazan-3-oxomethyl)oxetane by controlling the reaction conditions. The final product has high yield and high purity, easy post-processing, and the reaction route is efficient and time-saving, which is convenient for continuous industrial production.

[0022] The specific content of the present invention will be further explained in detail below with reference to the embodiments. Attached Figure Description

[0023] Figure 1 The 1H NMR spectrum of 3,3-bis(4-azidofurazan-3-oxomethyl)oxetane;

[0024] Figure 2 The carbon NMR spectrum of 3,3-bis(4-azidofurazan-3-oxomethyl)oxetane;

[0025] Figure 3 The FTIR spectrum of 3,3-bis(4-azidofurazan-3-oxomethyl)oxetane;

[0026] Figure 4 High-resolution mass spectrum of 3,3-bis(4-azidofurazan-3-oxomethyl)oxetane;

[0027] Figure 5The DSC diagram for 3,3-bis(4-azidofurazan-3-oxomethyl)oxetane.

[0028] The specific content of the present invention will be further explained in detail below with reference to the embodiments. Detailed Implementation

[0029] It should be noted that, unless otherwise specified, all raw materials used in this invention are those known in the prior art.

[0030] The synthetic route for 3,3-bis(4-azidofurazan-3-oxomethyl)oxetane disclosed in the prior art is as follows:

[0031]

[0032] This energetic monomer contains furazan and oxetane groups, exhibiting high energy density and promising applications as a multifunctional modular energetic material. However, the above synthetic route using 3-azido-4-hydroxyfurazan as the starting material involves four lengthy steps and low yields. The second step, cyclization, involves the corrosive strong acid trifluoromethanesulfonic acid and the corrosive strong base DBU. The synthetic route for this energetic oxetane monomer requires the separation of disubstituted products from four products before cyclization, making the process cumbersome, complex, and difficult to apply in practice.

[0033] The concept of this invention is as follows: Through a Williamson etherification reaction under alkaline conditions, and via nucleophilic attack by an oxonium anion, 3-nitro-4-hydroxyfurazan (which is much easier to synthesize than 3-azido-4-hydroxyfurazan) is combined with an oxetane to obtain an intermediate. Then, through a mature azidation reaction, the furazan nitro group is converted to an azide group to prepare 3,3-di(4-azidofurazan-3-oxomethyl)oxetane. This route can successfully synthesize the target compound, but the first step in preparing the intermediate has a long reaction time (3-4 hours) and a low yield (60%). Therefore, the inventors explored using inexpensive and readily available solvents such as N,N-dimethylformamide (DMF), acetonitrile (MeCN), acetone, and dimethyl sulfoxide (DMSO) as catalysts to accelerate the reaction.

[0034] This invention protects a method for synthesizing 3,3-bis(4-azidofurazan-3-oxomethyl)oxetane, the synthetic route of which is as follows:

[0035]

[0036] Includes the following steps:

[0037] Step 1: 3-Nitro-4-hydroxyfurazan, 3,3-dibromomethyloxetane, a basic donor and a phase transfer catalyst are added to a polar aprotic solvent and stirred at 60-100°C for 0.5-4 hours. Then, the mixture is extracted, washed with water, dried, filtered, the solvent is evaporated and recrystallized to obtain the intermediate 3,3-di(4-nitrofurazan-3-oxomethyl)oxetane.

[0038] The alkaline donors include anhydrous potassium carbonate, cesium carbonate, and ferric hydroxide.

[0039] The phase transfer catalysts include tetrabutylammonium bromide, benzyltriethylammonium chloride, methyltrialkylammonium chloride, and 18-crown ether-6.

[0040] Preferably, the molar ratio of 3,3-dibromomethyloxetane to 3-nitro-4-hydroxyfurazan is 1:(2-3.5).

[0041] Preferably, the molar ratio of 3-nitro-4-hydroxyfurazan to the basic donor is 1:(1.5-3).

[0042] Preferred polar aprotic solvents include DMF, MeCN, Acetone, and DMSO.

[0043] The polar aprotic solvents include DMF, MeCN, Acetone, and DMSO.

[0044] Step 2: The intermediate 3,3-bis(4-nitrofuran-3-oxomethyl)oxetane obtained in Step 1 and the azide reagent are added to a polar aprotic solvent, including DMF, MeCN, Acetone and DMSO. The mixture is then stirred at room temperature for 0.5 to 1.5 hours. After extraction, washing with water, drying, filtration, evaporation of the solvent and recrystallization, the product is obtained.

[0045] Furthermore, the azide reagent includes sodium azide, trimethyl azidosilane, p-toluenesulfonyl azide, ethyl azide, tetrabutylammonium azide, and tri-n-butyltin azide.

[0046] Furthermore, the molar ratio of the intermediate 3,3-bis(4-nitrofuran-3-oxomethyl)oxetane to the azide reagent is 1:(2.5-3.5).

[0047] The following are specific embodiments of the present invention. It should be noted that the present invention is not limited to the following specific embodiments. All equivalent modifications made based on the technical solutions of this application fall within the protection scope of the present invention.

[0048] Example 1

[0049] This embodiment provides a method for synthesizing 3,3-bis(4-azidofurazan-3-oxomethyl)oxetane, comprising the following steps:

[0050] Step 1: 3-Nitro-4-hydroxyfurazan (2.62 g, 0.02 mol), 3,3-dibromomethyloxetane (2.44 g, 0.01 mol), anhydrous potassium carbonate (2.76 g, 0.02 mol), and phase transfer catalyst 18-crown ether-6 (0.05 g, 0.0002 mol) were added to dimethylformamide DMF (30 ml) at room temperature and stirred thoroughly. The mixture was reacted at 75 °C for 1.5 h. After the reaction was completed, water and dichloromethane were added for extraction. The mixture was then washed with water, dried over anhydrous magnesium sulfate, filtered, and the solvent was evaporated. The mixture was recrystallized to obtain pale yellow crystals (2.8 g, yield 81%) as the intermediate.

[0051] Step 2: Add the intermediate obtained in Step 1 (1.72 g, 0.005 mol) and sodium azide (0.65 g, 0.01 mol) to 3 ml of DMF, stir and react at room temperature for 0.5 h, then extract with ethyl acetate, wash with water, dry, filter, suspend and evaporate, and recrystallize with ethanol to obtain the target product in white crystals (1.51 g, yield 90%).

[0052] Structural assessment:

[0053] (1) Carbon nuclear magnetic resonance spectroscopy analysis

[0054] like Figure 2 As shown, comparing the obtained spectrum with that of the intermediate 3,3-bis(4-nitrofurazan-3-oxomethyl)oxetane reveals that the characteristic peaks of 3,3-bis(4-nitrofurazan-3-oxomethyl)oxetane at 158.77 ppm and 152.65 ppm have shifted, moving to lower and higher fields to 159.26 ppm and 145.23 ppm, respectively. Furthermore, the peak shape has changed from the high-low peak pattern characteristic of nitrofurazan to an approximately equal peak pattern characteristic of azidofurazan, indicating the disappearance of the furazan nitro group and the formation of azidofurazan. The characteristic peaks of methyloxetane at 73.42 ppm, 73.33 ppm, and 42.68 ppm show little change, indicating that the main body of methyloxetane remains unchanged. The corresponding proton NMR spectrum is shown below. Figure 1 As shown, the area obtained by integrating the corresponding peaks is 1:1, which also confirms the successful synthesis of 3,3-bis(4-azidofurazan-3-oxomethyl)oxetane.

[0055] (2) Infrared spectral analysis

[0056] The obtained spectrum is compared with that of the intermediate 3,3-bis(4-nitrofuran-3-oxomethyl)oxetane, for example Figure 3 As shown, it is located at 835cm. -1The characteristic peak of oxetane is still present, indicating that the oxetane structure still exists in the pure monomer; while the peak at 1624 cm⁻¹ is still present. -1 The disappearance of the nitro infrared absorption peak at 2100 cm⁻¹ indicates that the product no longer contains nitro groups; while the nitro infrared absorption peak at 2100 cm⁻¹... -1 With 2150cm -1 The appearance of the characteristic absorption peak of the azido group indicates the successful synthesis of 3,3-bis(4-azidofurazan-3-oxomethyl)oxetane.

[0057] (3) High-resolution mass spectrometry analysis

[0058] like Figure 4 As shown, the highest peak m / z in the high-resolution mass spectrum is 337.08619, which is in good agreement with the predicted hydrogenation peak of 337.0757, indicating the successful synthesis of 3,3-bis(4-azidofurazan-3-oxomethyl)oxetane.

[0059] (4) Single-crystal X-ray diffraction results

[0060] The obtained single-crystal X-ray diffraction results are shown in the table below:

[0061]

[0062] The 3,3-bis(4-azidofurazan-3-oxomethyl)oxetane prepared in this embodiment, by introducing a furazan group into oxetane, acquires excellent detonation performance and extremely high stability, functioning as both a single-element explosive and an energetic plasticizer. Simultaneously, the introduced oxetane structure endows it with good polymerization ability, greatly expanding its application fields. It can be polymerized as a structural energetic material or energetic adhesive, and can also be used as an energetic initiator / chain extender. It is a highly promising multifunctional insensitive energetic material.

[0063] Example 2

[0064] The synthesis method and steps used in this embodiment are the same as those in Example 1, except that in step 1, the reaction is carried out at 65°C for 1.5 h to obtain pale yellow crystals (1.9 g, yield 55%) as an intermediate; the final product is 1.51 g, yield 90%.

[0065] The structural identification results in this embodiment are the same as those in Embodiment 1.

[0066] Example 3

[0067] The synthesis method and steps used in this embodiment are the same as those in Example 1, except that in step 1, the reaction is carried out at 75°C for 2.5 h to obtain a pale yellow crystal as an intermediate (2.9 g, yield 84%); the final product is 1.51 g, yield 90%.

[0068] The structural identification results in this embodiment are the same as those in Embodiment 1.

[0069] Example 4

[0070] The synthesis method and steps used in this embodiment are the same as those in Example 1, except that: in step 1, the amount of 3-nitro-4-hydroxyfuran added is 3.93 g, 0.03 mol, to obtain pale yellow crystals as an intermediate (3.0 g, yield 58%); the final product obtained is 1.51 g, yield 90%.

[0071] The structural identification results in this embodiment are the same as those in Embodiment 1.

[0072] Example 5

[0073] The synthesis method and steps used in this embodiment are the same as those in Example 1, except that: in step 1, the polar aprotic solvent used is DMSO, and a pale yellow crystal (2.1 g, yield 61%) is obtained as an intermediate; the final product obtained in step 2 is 1.51 g, yield 90%.

[0074] The structural identification results in this embodiment are the same as those in Embodiment 1.

[0075] Example 6

[0076] The synthesis method and steps used in this embodiment are the same as those in Example 1, except that in step 2, the reaction is stirred at room temperature for 1.5 h to obtain the final product as white crystals (1.55 g, yield 92%).

[0077] The structural identification results in this embodiment are the same as those in Embodiment 1.

[0078] Example 7

[0079] The synthesis method and steps used in this embodiment are the same as those in Example 1, except that in step 2, the amount of sodium azide added is 0.975 g, 0.015 mol, and white crystals (1.56 g, yield 93%) are obtained as the final product.

[0080] The structural identification results in this embodiment are the same as those in Embodiment 1.

[0081] Example 9

[0082] The synthesis method and steps used in this embodiment are the same as those in Example 1, except that the phase transfer catalyst is tetrabutylammonium bromide, yielding 0.92g of pale yellow crystals with a yield of 54.8%.

[0083] The structural identification results in this embodiment are the same as those in Embodiment 1.

[0084] Example 10

[0085] The synthesis method and steps used in this embodiment are the same as those in Example 1, except that the phase transfer catalyst is benzyltriethylammonium chloride, and 1.23 g of pale yellow crystals are obtained, with a yield of 73.2%.

[0086] The structural identification results in this embodiment are the same as those in Embodiment 1.

[0087] Comparative Example 1

[0088] The synthesis method used in this comparative example is the same as that in Example 1, except that no phase transfer catalyst was added in step 1; the final yield was 0.69 g of pale yellow crystals, with a yield of 41.3%.

[0089] The structural identification results of this comparative example are the same as those of Example 1.

[0090] As can be seen from Examples 1 to 12, and Comparative Examples 1 to 3:

[0091] First, with the same raw material composition, the addition of a phase transfer catalyst enhances the catalytic ability of this type of reaction. Second, the product yield increases with increasing reaction temperature, but the yield increase becomes less significant after 75°C. Considering safety factors, 75°C is the optimal temperature for this reaction. Polar aprotic solvents, especially DMF, have a significant solvation effect that promotes the reaction. This is because there is a high energy barrier when a monosubstituted product is further substituted into a disubstituted product. Using high-boiling-point polar aprotic solvents not only provides energy through heating to help the reaction overcome the energy barrier, but also the special solvation effect of polar aprotic solvents can greatly improve the reaction rate and yield.

[0092] Compared to existing methods that use pentaerythritol (a potentially explosive hazardous substance) and cumbersome and inefficient 3-azido-4-hydroxyfurazan as raw materials to obtain 3,3-di(4-azidofurazan-3-oxomethyl)oxetane in the presence of a strong corrosive base (DBU) and a corrosive acid (trifluoromethanesulfonic acid), this invention uses readily available and inexpensive 3-nitro-4-hydroxyfurazan and commercially available 3,3-dibromomethyloxetane as raw materials. In an alkaline solvent system, in the presence of a catalytically applied phase transfer catalyst, heating yields 3,3-di(4-nitrofurazan-3-oxomethyl)oxetane. The final product, 3,3-di(4-azidofurazan-3-oxomethyl)oxetane, is then reacted with sodium azide in DMF solvent. This method offers the advantages of readily available reactants and minimal environmental pollution.

[0093] Compared with the existing method that involves a four-step reaction of diaminofurazan followed by cumbersome post-processing to obtain 3-azido-4-hydroxyfurazan, and then the four azidofurazan-substituted pentaerythritols still require a complex separation process and screening to select the di- and tri-substituted pentaerythritols for further cyclization reactions to finally obtain 3,3-di(4-azidofurazan-3-oxomethyl)oxetane, the reaction route of this invention is highly efficient and time-saving, and is convenient for continuous industrial production.

[0094] In summary, the raw materials of the present invention are readily available, the reaction conditions are simple, and the environmental pollution is minimal. By controlling the reaction conditions, the intermediate nitro-substituted product can be completely converted into the azide-substituted product 3,3-bis(4-azidofurazan-3-oxomethyl)oxetane, with high product yield, high purity, short reaction time, and easier post-processing, which is conducive to continuous industrial production.

[0095] The preferred embodiments of this disclosure have been described in detail above with reference to the accompanying drawings. However, this disclosure is not limited to the specific details of the above embodiments. Within the scope of the technical concept of this disclosure, various simple modifications can be made to the technical solutions of this disclosure, and these simple modifications all fall within the protection scope of this disclosure.

[0096] It should also be noted that the various specific technical features described in the above specific embodiments can be combined in any suitable manner without contradiction. In order to avoid unnecessary repetition, this disclosure will not describe the various possible combinations separately.

[0097] Furthermore, various different embodiments of this disclosure can be combined in any way, as long as they do not violate the spirit of this disclosure, they should also be regarded as the content disclosed in this disclosure.

Claims

1. A method for synthesizing 3,3-bis(4-azidofurazan-3-oxomethyl)oxetane, characterized in that, The method includes the following steps: Step 1: 3-nitro-4-hydroxyfurazan, 3,3-dibromomethyloxetane, a basic donor and a phase transfer catalyst are added to a polar aprotic solvent and stirred at 60-100℃ for 0.5-4 h. Then, the mixture is extracted, washed with water, dried, filtered, the solvent is evaporated and recrystallized to obtain the intermediate 3,3-di(4-nitrofurazan-3-oxomethyl)oxetane. Step 2: The intermediate 3,3-bis(4-nitrofuran-3-oxomethyl)oxetane obtained in Step 1 and the azide reagent are added to a polar aprotic solvent and stirred at room temperature for 0.5-1.5 h. Then, the mixture is extracted, washed with water, dried, filtered, the solvent is evaporated, and recrystallized to obtain the final product. The alkaline donor mentioned in step 1 is selected from either anhydrous potassium carbonate or cesium carbonate; The phase transfer catalyst mentioned in step 1 is selected from any one of tetrabutylammonium bromide, benzyltriethylammonium chloride, and 18-crown ether-6; In step 2, the azide reagent is selected from any one of sodium azide, trimethyl azidosilane, p-toluenesulfonyl azide, ethyl azide, tetrabutylammonium azide, and tri-n-butyltin azide. The polar aprotic solvent is selected from any one of DMF, MeCN, acetone and DMSO; In step 1, the molar ratio of 3,3-dibromomethyloxetane to 3-nitro-4-hydroxyfurazan is 1:(2~3.5). In step 1, the molar ratio of 3-nitro-4-hydroxyfuran to the basic donor is 1:(1.5~3).

2. The synthesis method according to claim 1, characterized in that, In step 2, the molar ratio of intermediate 3,3-bis(4-nitrofuran-3-oxomethyl)oxetane to the azide reagent is 1:(2.5~3.5).

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