Bipyrazole energetic compound and preparation method thereof

Abstract

The invention discloses 3, 4 '-bipyrazole and an energetic compound thereof, which are characterized in that an energetic group is introduced to a 3, 4'-bipyrazole skeleton to further functionalize the 3, 4 '-bipyrazole skeleton; the invention also discloses a preparation method of the 3, 4 '-bipyrazole and the energetic compound thereof, the synthesis of the novel bipyrazole energetic compound is realized through multi-step reaction from the raw materials easy to prepare, and the compound has great potential to be used as a high-energy material, and provides a new idea for synthesizing the novel high-energy energetic compound in energetic materials.

Description

Technical Field

[0001] The present invention relates to the technical field of energetic materials, and in particular to bipyrazole energetic compounds and preparation methods thereof. Background Art

[0002] High-energy materials play an indispensable role in both military defense and civilian science and technology, especially in promoting aerospace technology innovation, improving mining efficiency and enriching pyrotechnic art performance. With the continuous development of the application demand of high energy density materials (HEDM), the pursuit of excellent performance and the stability of molecular structure have become the two core elements to measure their comprehensive performance. Compared with the traditional energetic compound system, nitrogen-rich heterocyclic molecules stand out with their unique chemical structure. Their nitrogen content is significantly higher than the carbon and hydrogen content in traditional compounds, which gives these molecules a higher formation enthalpy potential. In particular, the bipyrazole molecular skeleton, as a model of high energy density chemical bonds such as NN bonds, CN bonds and C=N bonds, has a widely existing conjugated planar large π bond structure inside, which not only effectively improves the explosion heat and unit specific impulse performance, but also significantly enhances the thermal stability of the molecule, thereby ensuring the superior performance and low mechanical sensitivity of the material in complex application environments. At the same time, the introduction of explosive groups such as nitro groups into the bipyrazole molecular skeleton can further improve the energy performance of the compound. The synthesis of bipyrazole energetic compounds has become one of the research hotspots in the field of energetic materials in recent years. Summary of the invention

[0003] The purpose of the present invention is to provide a tetranitrobipyrazole energetic compound and an amino tetranitrobipyrazole based on a 3,4'-bipyrazole compound. A novel bipyrazole skeleton can be obtained in one step through the ring contraction reaction of bipyrimidine, and then 3,4'-bipyrazole is further functionalized through nitration and amination reactions of the bipyrazole skeleton, which effectively improves the thermal stability and detonation performance of these energetic compounds, making them more advantageous in the application of energetic materials.

[0004] Another object of the present invention is to provide a method for preparing the novel 3,4'-bipyrazole compound, tetranitrobipyrazole energetic compound and aminotetranitrobipyrazole. The method successfully synthesizes tetranitrobipyrazole energetic compound from known available raw materials through multi-step reactions. The synthesized bipyrazole energetic compound has great potential as a high-energy material.

[0005] The 3,4'-bipyrazole compound mentioned in the technical solution of the present invention is: Tetranitrobipyrazole energetic compounds: structural formula Aminotetranitrobipyrazole energetic compounds: Structural formula

[0006] The preparation method of 3',4,5,5'-tetranitro-1'H,2H-[3,4'-bipyrazole]-1',2-diamine energetic material specifically comprises the following steps:

[0007] 1) At room temperature, 4,5'-bipyrimidine is added to toluene, and trifluoromethanesulfonic anhydride is added thereto. After reacting at room temperature for 2 hours, hydrazine hydrate is added, the temperature is raised to 60 degrees, and the reaction is continued for 24 hours to prepare 3,4'-bipyrazole (Compound 1);

[0008]

[0009] 2) a step of reacting 3,4'-bipyrazole with a nitrating agent to generate tetranitro-3,4'-bipyrazole (compound 2);

[0010]

[0011] 3) a step of preparing compound 3 by subjecting compound 2 to an amination reaction with an aminating agent.

[0012]

[0013] Preferably, in step 1), the concentration of hydrazine hydrate used may be 80 wt% or 85 wt%, and the molar ratio of 4,5'-bipyrimidine to trifluoromethanesulfonic anhydride to water to hydrazine is 1:2:4 to 1:10:20.

[0014] Preferably, in step 2), in the potassium nitrate / sulfuric acid nitration system, the sulfuric acid may be concentrated sulfuric acid or any one of 20 wt% oleum, and the mass ratio of compound 1 to potassium nitrate and sulfuric acid is 1:10:30 to 1:10:60.

[0015] Preferably, in step 3), the reaction is carried out in the presence of an alkaline substance, using acetonitrile as the reaction solvent, wherein the alkaline substance can be any one of potassium hydroxide, sodium bicarbonate, and 1,8-diazabicyclopentane-dec-7-ene (DBU).

[0016] Preferably, in step 3), the amination reagent may be any one of hydroxylamine oxysulfonic acid or O-toluenesulfonylhydroxylamine.

[0017] Compared with the prior art, the present invention has the following beneficial effects:

[0018] (1) The present invention adopts a one-step method to synthesize a novel 3,4'-bipyrazole skeleton, which greatly shortens the synthesis steps compared with the traditional pyrazole synthesis method. For example, the synthesis of 3,3'-bipyrazole requires at least 3 steps and also requires the use of highly toxic, high-concentration hydrazine hydrate. The synthesis of 4,4'-bipyrazole requires at least 7 steps, while the present synthesis method only requires 1 step to obtain the target molecule. At the same time, compared with the reported 3,4'-bipyrazole synthesis method, the yield is also greatly improved, which is about three times that of the reported method. It can be seen that the present method greatly improves the synthesis efficiency of bipyrazole and does not require the use of highly toxic substances as synthetic raw materials, further improving the safety of the reaction and laying a foundation for future industrial production.

[0019] (2) The present invention introduces energetic groups through the reactivity of nitrogen-hydrogen bonds in the bipyrazole skeleton to achieve nitrogen-amino functionalization, and further functionalizes the 3,4'-bipyrazole skeleton. The thermal decomposition temperatures of energetic molecules 2 and 3 are both above 250 degrees Celsius. While having good thermal stability, the detonation velocities of the two molecules reach 8173 m·s -1 and 8355m·s -1 , which is much faster than the detonation speed of the classic explosive TNT (7005m·s -1 ). It can be seen that the thermal stability and detonation performance of energetic compounds are effectively improved, making them more advantageous in the application of energetic materials. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 is the carbon NMR spectrum of compound 2 in Example 1 of the present invention;

[0021] Figure 2 is the hydrogen nuclear magnetic resonance spectrum of compound 3 in Example 1 of the present invention;

[0022] Figure 3 is the carbon NMR spectrum of compound 3 in Example 1 of the present invention;

[0023] Figure 4 is a single crystal structure diagram of compound 2 in Example 1 of the present invention;

[0024] Figure 5 This is a single crystal structure diagram of compound 3 in Example 1 of the present invention. DETAILED DESCRIPTION

[0025] In order to make the purpose, technical solution and advantages of the present invention more clear, the following is a further detailed description in conjunction with the accompanying drawings and specific embodiments. It should be understood that the specific embodiments described are only used to explain this patent, but are not used to limit this invention.

[0026] Example 1

[0027] Bipyrazole energetic compound 3, its structural formula is as follows:

[0028]

[0029] The specific synthetic route is as follows:

[0030]

[0031] The specific synthesis steps are as follows:

[0032] Step 1. Synthesis of Compound 1

[0033] 4,5'-Bipyrimidine (0.1mmol) was dissolved in toluene (1.0mL), nitrogen was replaced, trifluoromethanesulfonic anhydride (0.25mmol) was added, and the mixture was reacted at room temperature for 2 hours, 80% mass fraction of hydrazine hydrate (0.6mmol) was added, and the reaction mixture was reacted at 60 degrees for 24 hours, and the reaction was monitored by thin layer chromatography. After the reaction was completed, it was cooled to room temperature, concentrated, and separated and purified by column chromatography to obtain compound 1 (60% yield).

[0034] Step 2: Synthesis of Compound 2

[0035] At 0°C, potassium nitrate (10.0 g) was slowly added to concentrated sulfuric acid (60.0 g) in batches, and then compound 1 (1.0 g) was slowly added to the nitration system in batches. After the addition was completed, the temperature was raised to 100 degrees and the reaction was continued at this temperature for 48 hours. After the reaction was completed, the reaction solution was poured into 100 mL of ice water to quench, and extracted with ether, the organic phases were combined, and the organic solvent was removed by concentration to obtain compound 2 (50% yield)

[0036] Step 3. Synthesis of Compound 3

[0037] At 0°C, 1,8-diazabicycloundec-7-ene (2.0 mmol) was added to a solution of compound 2 (1.0 mmol) in acetonitrile (7.5 mL). The reaction was continued for 30 minutes, and freshly prepared O-toluenesulfonylhydroxylamine (2.4 mmol) was added. The reaction was returned to room temperature and monitored by thin layer chromatography. After the reaction was completed, the solvent was removed and purified by column chromatography to obtain compound 3 (60% yield).

[0038] Example 2

[0039] The physicochemical properties of the energetic compounds 2 and 3 synthesized in the examples of the present invention are shown in Table 1.

[0040] Table 1: Physicochemical properties of compounds 2 and 3

[0041]

[0042] It can be seen from the above table that energetic compounds 2 and 3 have relatively good thermal stability and detonation performance. For energetic materials, formation enthalpy and density jointly determine the detonation velocity and detonation pressure. Detonation velocity and detonation pressure are the key to the performance of energetic materials, and the higher the better; impact sensitivity and friction sensitivity are the key to whether they can be used, and the higher the sensitivity, the duller it is. Insensitive energetic materials have good stability and are safer to use and store. This shows that these two new compounds have great potential to become high-energy materials.

[0043] Although the embodiments of the present invention have been disclosed above, they are not limited to the applications listed in the specification and the embodiments. It can be fully applied to various fields suitable for the present invention. For those familiar with the art, additional modifications can be easily realized. Therefore, without departing from the general concept defined by the claims and equivalent scope, the present invention is not limited to the specific details and the illustrations shown and described here.

Claims

1. A tetranitrobipyrazole energetic compound, characterized in that: The tetranitrobipyrazole energetic compound is a compound based on 3,4'-bipyrazole and has the following structure (II):

2. An aminotetranitrobipyrazole energetic compound, characterized in that: The amino tetranitro bipyrazole energetic compound has the structure of the following formula (III):

3. A method for preparing the bipyrazole energetic compound according to any one of claims 1 or 2, characterized in that: The steps include: Step 1: Synthesis of bipyrazole compound of formula (I) Using 4,5'-bipyrimidine as a raw material, a bipyrazole compound of formula (I) is obtained by ring contraction reaction; Step 2: Synthesis of tetranitrobipyrazole compound of formula (II) The bipyrazole compound of formula (I) obtained in step 1 is used as a raw material, and a tetranitrobipyrazole compound of formula (II) is obtained by nitration reaction; Step 3: Synthesis of amino tetranitrobipyrazole compound of formula (III) The tetranitrobipyrazole compound of formula (II) obtained in step 2 is reacted with an aminating agent to obtain an aminotetranitrobipyrazole compound of formula (III).

4. The method as claimed in claim 3, characterized in that In the step 1, the reaction of synthesizing the bipyrazole compound of formula (I) using 4,5'-bipyrimidine as a raw material specifically includes: In toluene, 4,5'-bipyrimidine reacts with hydrazine hydrate and trifluoromethanesulfonic anhydride to obtain a bipyrazole compound of formula (I).

5. The method as claimed in claim 3, characterized in that In the step 2, the tetranitrobipyrazole compound of formula (II) is synthesized by nitration reaction using the bipyrazole compound of formula (I) as a raw material, which specifically includes: The step of adding the bipyrazole of formula (I) into a nitration system of KNO3 / H2SO4 to prepare a tetranitropyrazole compound of formula (II).

6. The method as claimed in claim 3, characterized in that In the step 3, the reaction of preparing the amino tetranitrobipyrazole of formula (III) using the tetranitropyrazole compound of formula (II) as a raw material specifically includes: At zero degrees, 1,8-diazabicycloundec-7-ene is added dropwise to an acetonitrile solution of a tetranitropyrazole compound of formula (II), and stirring is continued at this temperature for 30 minutes. Then, an amination reagent is added dropwise to the reaction mixture, and the reaction is carried out at room temperature until the starting material disappears, thereby obtaining an amino tetranitrobipyrazole compound of formula (III).

7. The method according to claim 4, characterized in that The reaction temperature is from room temperature to 60 degrees Celsius, and the reaction time is at least 24 hours.

8. The method according to claim 5, characterized in that The reaction temperature is 100 degrees Celsius and the reaction time is at least 48 hours.

9. The method according to claim 6, characterized in that The amination reagent is any one of hydroxylamine oxysulfonic acid or O-toluenesulfonylhydroxylamine.

10. The method as claimed in claim 3, characterized in that The bipyrazole compound of formula (I) has the following structure:

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