Preparation method of 1, 3, 4-oxadiazole-1, 2, 4-triazole energetic molecule and derivative thereof

Abstract

The invention belongs to the technical field of organic synthetic chemistry, and particularly relates to a preparation method of a 1, 3, 4-oxadiazole-linked 1, 2, 4-triazole energetic molecule and a derivative thereof, the concept of resonance assisted hydrogen bond (RAHB) is introduced in the preparation method, and a part of covalent bonds are formed through a hydrogen bond donor and a hydrogen bond acceptor which are connected through a pi-conjugated structure, so that the energy-containing molecule can be used for preparing the 1, 3, 4-oxadiazole-linked 1, 2, 4-triazole energetic molecule. The design strategy is novel, the contradiction between high energy and stability in a traditional energetic material is effectively solved, the balance of energy and safety is realized, the finally prepared compound I shows excellent detonation performance, the detonation velocity reaches 9042 m.s <-1 >, the detonation pressure is 35.4 GPa, and the compound I can be used for preparing a high-energy-storage material. Meanwhile, the thermal stability is relatively high, and the decomposition temperature is 183 DEG C, so that the molecular density and the thermal stability of the energetic material are remarkably improved through the construction of RAHB, and the performance of the compound I is superior to that of a plurality of traditional explosives.

Description

Technical Field

[0001] The invention belongs to the technical field of organic synthetic chemistry, and specifically relates to a preparation method of 1,3,4-oxadiazole-1,2,4-triazole energetic molecules and derivatives thereof. Background Art

[0002] Energetic materials can release a large amount of energy instantaneously under external stimulation, and they are the core of many weapon systems. To date, a lot of efforts have been invested in the development of promising energetic compounds. In the past decade, many new energetic molecules have emerged, some of which are comparable to traditional explosives in comprehensive performance. Azoles and their derivatives (pyrazoles, triazoles, oxadiazoles, etc.) are the basis of various functional compounds. In recent years, they have occupied an increasingly preferential position in the field of energetic materials. Due to the high nitrogen content, high formation enthalpy and more chemical reaction sites of azole compounds, they have attracted extensive attention as building blocks of energetic compounds. In addition, bridged or multi-ring fusion compounds can better balance the contradiction between energy and sensitivity, which is the eternal pursuit in the design and synthesis of energetic materials. This property is largely attributed to the larger conjugated structure and complex hydrogen bond network, which are conducive to improving mechanical sensitivity as well as thermal stability. In addition, different transformations and arrangements of explosive groups (such as -N3, -NO2, -NHNO2, etc.) will profoundly regulate the properties of energetic compounds to meet the needs of various conditions as much as possible. However, developing energetic molecules that are both high-energy and stable is a huge challenge. Generally, the higher the energy of energetic molecules, the worse their stability. At present, constructing polycyclic molecular structures such as condensed rings and linked rings has been proven to be an important way to achieve a balance between energy and stability, but how to effectively regulate the energy and stability of molecules through rational modification of functional groups is still unclear, the principle is unclear, and the rules need to be summarized. Therefore, this application proposes to use resonance assisted hydrogen bonding (RAHB) to design high-energy and stable energetic molecules in order to achieve a balance between energy and safety. Summary of the invention

[0003] The purpose of the present invention is to provide a method for preparing 1,3,4-oxadiazole-1,2,4-triazole energetic molecules and their derivatives, and the compound I prepared according to the method exhibits excellent detonation performance and thermal stability. Experimental results show that RAHB can significantly improve the molecular density and thermal stability of energetic materials, achieving a balance between energy and safety.

[0004] The objective of the present invention is achieved through the following technical solutions:

[0005] The present invention provides a 1,3,4-oxadiazole-1,2,4-triazole energetic molecule, wherein the structural formula of the 1,3,4-oxadiazole-1,2,4-triazole energetic molecule is

[0006] The present invention also provides a 1,3,4-oxadiazole-1,2,4-triazole energetic molecular derivative, wherein the structural formula of the 1,3,4-oxadiazole-1,2,4-triazole energetic molecular derivative is

[0007] The present invention also provides a method for preparing the 1,3,4-oxadiazole-1,2,4-triazole energetic molecule or the 1,3,4-oxadiazole-1,2,4-triazole energetic molecule derivative, comprising the steps of adding compound A to concentrated nitric acid and mixing. The structural formula of compound A is

[0008] Furthermore, the preparation method of the 1,3,4-oxadiazole-linked 1,2,4-triazole energetic molecule comprises the following steps: adding compound A to concentrated nitric acid in a low temperature environment to dissolve, then heating and stirring, and then extracting, washing, drying and evaporating to obtain the 1,3,4-oxadiazole-linked 1,2,4-triazole energetic molecule.

[0009] Furthermore, the low temperature environment is -10°C, and the heating is to 0°C.

[0010] Furthermore, the preparation method of the 1,3,4-oxadiazole-1,2,4-triazole energetic molecular derivative comprises the following steps:

[0011] (1) Compound A is added to concentrated nitric acid in a low temperature environment to dissolve, and then stirred at room temperature. The solution is then poured into ice water to allow it to settle, and then filtered to obtain Compound B;

[0012] (2) Compound B is suspended in ethanol at low temperature, and then hydrated hydroxylamine is added dropwise to the mixture, and the mixture is stirred overnight at room temperature. After filtering, washing, and drying, the 1,3,4-oxadiazole-1,2,4-triazole energetic molecular derivative is obtained.

[0013] Furthermore, the low temperature environment is -10°C, and the structural formula of the compound B is

[0014] Furthermore, the preparation method of compound A comprises suspending compound 3 in ethanol and water, then adding acetonitrile solution containing bromocyanide dropwise into the mixture, and obtaining the compound A after stirring, filtering, washing and drying.

[0015] Furthermore, the chemical structural formula of the compound 3 is The syntheses of compounds 1, 2 and 3 were prepared according to the reference "2-(1,2,4-triazole-5-yl)-1,3,4-oxadiazole as a novel buildingblock for energetic materials" 26 August 2022, DOI, 10.3389 / fchem.2022.996812.

[0016] The present invention also provides an application of the 1,3,4-oxadiazole-1,2,4-triazole energetic molecule or the 1,3,4-oxadiazole-1,2,4-triazole energetic molecule derivative in the preparation of energetic materials, wherein the energetic material has excellent detonation performance and thermal stability.

[0017] The beneficial effects of the present invention are:

[0018] The present invention introduces the concept of resonance assisted hydrogen bonding (RAHB), which forms partial covalent bonding properties through hydrogen bond donors and acceptors connected by π-conjugated structures, thereby enhancing the stability and density of the molecule. This design strategy is not only novel, but also effectively solves the contradiction between high energy and stability in traditional energetic materials, and achieves a balance between energy and safety.

[0019] The compound I prepared by the present invention exhibits excellent detonation performance, and its detonation velocity reaches 9042m·s -1 The explosion pressure is 35.4 GPa, and the thermal stability is also high, with a decomposition temperature of 183°C. The above data show that the molecular density and thermal stability of energetic materials are significantly improved through the construction of RAHB, making compound I superior to many traditional explosives in performance.

[0020] The present invention also provides detailed synthetic routes of compounds I and II, including a synthetic method of raw material compound A, and a process for preparing high-energy derivatives by different nitration conditions and selective conversion of diazo groups. These synthetic methods not only have high yields but are also easy to operate and do not require laborious separation, thus providing the possibility for large-scale preparation of energetic materials. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0022] Figure 1The specific synthesis route of the 1,3,4-oxadiazole-1,2,4-triazole energetic molecules and their derivatives in the present invention;

[0023] Figure 2 is the hydrogen nuclear magnetic resonance spectrum of compound A in the present invention;

[0024] Figure 3 is the carbon nuclear magnetic resonance spectrum of compound A in the present invention;

[0025] Figure 4 is the chemical structure diagram of compound I in the present invention;

[0026] Figure 5 FIG. 4 is a chemical structure diagram of compound II in the present invention. DETAILED DESCRIPTION

[0027] The embodiments of the present invention are described in detail below, and the embodiments are intended to explain the present invention and should not be construed as limiting the present invention. If specific techniques or conditions are not specified in the embodiments, they are carried out according to the techniques or conditions described in the literature in this area or according to the product specifications. If the manufacturers of reagents or instruments are not specified, they are all conventional products that can be obtained commercially.

[0028] In order to have a clearer understanding of the technical features, purposes and effects of the present invention, the specific implementation methods of the present invention are now described.

[0029] The reaction flow chart of the preparation process of 1,3,4-oxadiazole-1,2,4-triazole energetic molecules in the present invention is as follows: Figure 1 As shown, the specific reaction formula for preparing compound I and compound II using compound A is as follows:

[0030]

[0031] Among them, the structural formula of the prepared compound I is The structural formula of the obtained compound II is

[0032] Example 1

[0033] In this embodiment, the 1,3,4-oxadiazole-1,2,4-triazole energetic molecules specifically include the following steps:

[0034] (1) Compound 3 (0.5-2.5 g, 3.05-15.2 mmol) was suspended in 15.0 ml of ethanol and 5.0 ml of water. Then, bromocyanide (1.3 g, 12.2 mmol) in 1.0 ml of acetonitrile was added dropwise to the mixture. The reaction system was stirred at 50° C. for 24 hours. The white precipitate was filtered, washed with water and a small amount of ethanol, and then dried in air to obtain Compound 4 (Compound 4 i.e. Compound A) (yield 78%).

[0035] (2) At -10°C, compound A (0.3-1 g, 1.8-6 mmol) was slowly added to 4.5 ml of concentrated nitric acid. The mixture was kept at this temperature until all solids were completely dissolved. Then, the solution was heated to 0°C and stirred for 7 hours. Thereafter, the obtained clear reddish-brown solution was poured into ice water and extracted with ethyl acetate. The organic phase was washed with brine several times, dried over anhydrous magnesium sulfate, and evaporated under vacuum to obtain compound 6 (i.e., compound I) (yield 47%).

[0036] (3) Compound A (0.5-2.5 g, 3.05-15.2 mmol) was slowly added to 4.5 ml of concentrated nitric acid at -10°C. The mixture was kept at this temperature until all solids were completely dissolved. After that, the clear reaction system was stirred at room temperature for 24 hours. The solution was poured into ice water. After standing for a period of time, compound 5 precipitated from the aqueous phase. The white solid was collected by filtration to obtain compound 5 (i.e., compound B) (yield 67%).

[0037] (4) Compound B (0.3-1 g, 1.3-4.4 mmol) was suspended in 5.0 ml of ethanol at -10°C. Hydroxylamine hydrate (0.15 ml, 50%) was added dropwise to the mixture at this temperature. The reaction system was then stirred overnight at room temperature. The white precipitate was filtered, washed with cold ethanol, and dried in air to obtain Compound 7 (i.e., Compound II) (yield 81%).

[0038] The H NMR spectrum of compound A obtained according to the above process is as follows: Figure 2 As shown, the carbon NMR spectrum is as follows Figure 3 As shown, from the above content, it can be known that the 1HNMR (400MHz, DMSO-d6) of compound A: δ = 7.95, 6.87ppm; 13C NMR (100MHz, DMSO-d6): δ = 163.35, 156.12, 150.91, 144.46ppm. The HRMS (ESI+, m / z) calculated value is C4H6N7O+: 168.0628, and the measured value is 168.0631; the HRMS (ESI-, m / z) calculated value is C4H4N7O-: 166.0483, and the measured value is 166.0488.

[0039] The specific structure of compound I obtained according to the above process is as follows Figure 4As shown, its NMR data are 1H (400MHz, DMSO-d6): δ = 8.66, 8.55, 7.44, 7.31ppm; 13C (100MHz, DMSO-d6): δ = 163.60, 163.57, 159.36, 151.03ppm. The specific structure of the obtained compound II is as follows Figure 4 As shown, its NMR data are 1H (400 MHz, DMSO-d6): δ = 8.66, 8.55, 7.44, 7.31 ppm; 13C (100 MHz, DMSO-d6): δ = 163.60, 163.57, 159.36, 151.03 ppm.

[0040] The relevant properties of compound I and compound II obtained based on the above process were investigated, and the final results are shown in Table 1.

[0041] Table 1 Related properties of compound I and compound II

[0042] property Compound I Compound II Density (g / cm3) 1.91 1.82 N+O(%) 80.1 79.0 Decomposition temperature (degrees) 183 148 Explosive speed (m / s) 9042 8703 Explosion pressure(GPa) 35.4 30.6 Impact sensitivity (J) 9 15 Friction sensitivity(N) 80 160

[0043] N+O (%): The content of nitrogen and oxygen in the compound (mass fraction)

[0044] It can be seen from the above table that the density of the compound I finally obtained in this embodiment is 1.91 grams per cubic centimeter, the decomposition temperature is 183 degrees, the detonation velocity is 9042 meters per second, the detonation pressure is 35.4 GPa, the impact sensitivity is 9J, and the friction sensitivity is 80N. The density of compound II is 1.82 grams per cubic centimeter, the decomposition temperature is 148 degrees, the detonation velocity is 8703 meters per second, the detonation pressure is 30.6 GPa, the impact sensitivity is 15J, and the friction sensitivity is 160N.

[0045] In summary, resonance-assisted hydrogen bonding (RAHB) is a special type of hydrogen bonding in which the donor and the acceptor are connected by a π-conjugated structure. Affected by the π electron delocalization effect, RAHB usually exhibits the properties of partial covalent bonding. Quasi-aromatic rings and aromatic rings constructed by RAHB can be further extended to larger conjugated systems, thereby enhancing molecular density and thermal stability. Inspired by this design strategy, the applicant prepared two bicyclic high-energy molecules with RAHB. The precursor 5-(3-amino-1H-1,2,4-triazol-5-yl)-1,3,4-oxadiazole-2-amine was synthesized by a more efficient method. Two high-energy products, compound I and the intermediate product in the preparation of compound II, were obtained under different nitration conditions without laborious separation. In addition, two other high-energy derivatives, compound II and compound 8, were prepared by selective conversion of the diazo group. All four high-energy molecules formed intramolecular RAHB through hydrogen atom transfer. Due to the presence of more RAHB, compound I exhibited the best detonation performance (Dv: 9042m·s-1 and P: 35.4GPa) and thermal stability (Td: 183℃). The experimental results show that RAHB can significantly improve the molecular density and thermal stability of energetic materials, achieving a balance between energy and safety.

[0046] Finally, it should be noted that the above embodiments are only used to illustrate the technical solution of the present invention rather than to limit it. Although the present invention has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that the technical solution of the present invention can be modified or replaced by equivalents without departing from the purpose and scope of the technical solution of the present invention, which should be covered by the scope of the claims of the present invention.

Claims

1. A 1,3,4-oxadiazole-1,2,4-triazole energetic molecule, characterized in that: The structural formula of the 1,3,4-oxadiazole-1,2,4-triazole energetic molecule is 2. A 1,3,4-oxadiazole-1,2,4-triazole energetic molecular derivative, characterized in that: The structural formula of the energetic molecular derivative of 1,3,4-oxadiazole and 1,2,4-triazole is 3. A method for preparing the 1,3,4-oxadiazole-1,2,4-triazole energetic molecule according to claim 1 or the 1,3,4-oxadiazole-1,2,4-triazole energetic molecule derivative according to claim 2, characterized in that: The method comprises the steps of adding compound A to concentrated nitric acid and mixing the compound A, wherein the compound A has the structural formula:

4. The preparation method according to claim 3, characterized in that: The preparation method of the 1,3,4-oxadiazole-1,2,4-triazole energetic molecule comprises the following steps: adding compound A to concentrated nitric acid in a low temperature environment to dissolve, then heating and stirring, and then extracting, washing, drying and evaporating to obtain the 1,3,4-oxadiazole-1,2,4-triazole energetic molecule.

5. The preparation method according to claim 4, characterized in that: The low temperature environment is -10°C, and the heating is to 0°C.

6. The preparation method according to claim 3, characterized in that: The preparation method of the 1,3,4-oxadiazole-1,2,4-triazole energetic molecular derivative comprises the following steps: (1) Compound A is added to concentrated nitric acid in a low temperature environment to dissolve, and then stirred at room temperature. The solution is then poured into ice water to allow it to settle, and then filtered to obtain Compound B; (2) Compound B is suspended in ethanol at low temperature, and then hydrated hydroxylamine is added dropwise to the mixture, and the mixture is stirred overnight at room temperature. After filtering, washing, and drying, the 1,3,4-oxadiazole-1,2,4-triazole energetic molecular derivative is obtained.

7. The preparation method according to claim 6, characterized in that: The low temperature environment is -10°C, and the structural formula of the compound B is 8. The preparation method according to claim 3, characterized in that: The preparation method of the compound A comprises suspending the compound 3 in ethanol and water, then adding an acetonitrile solution containing bromocyanide dropwise into the mixture, and stirring, filtering, washing, and drying to obtain the compound A.

9. The preparation method according to claim 8, characterized in that: The chemical structural formula of compound 3 is 10. Use of the 1,3,4-oxadiazole-1,2,4-triazole energetic molecule according to claim 1 or the 1,3,4-oxadiazole-1,2,4-triazole energetic molecule derivative according to claim 2 in the preparation of energetic materials, characterized in that: The energetic material has excellent detonation performance and thermal stability.

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