Synthesis method of fluoro gem-dinitropyrazole inner salt

Abstract

The invention discloses a synthetic method for preparing a fluoro gem-dinitropyrazole inner salt from a guanidine hydrazone derivative substituted by an open-chain trinitromethyl function. The preparation method comprises the following steps: taking 4, 4, 4-trinitro-n-butyraldehyde (I) and aminoguanidine hydrochloride as raw materials, carrying out nucleophilic addition reaction to obtain an intermediate N-(4, 4, 4-trinitro-butyl imino) guanidine hydrochloride (II), and then carrying out intramolecular cyclization on the intermediate II under an alkaline condition to prepare the 2-amidino-3-gem-dinitropyrazole inner salt (III). The inner salt III reacts with nitric acid and sulfuric acid to generate an intermediate 2-(N-nitro) amidinyl-3-gem-dinitropyrazole inner salt (IV), and the inner salt (IV) and xenon difluoride are subjected to a substitution reaction to prepare a product 2-(N-nitro) amidinyl-3-fluorine dinitromethylpyrazole inner salt (V). According to the invention, a strategy of intramolecular cyclization and inner salt-to-inner salt conversion is utilized to prepare the fluoro gem-dinitropyrazole inner salt with high thermal stability, high energy and low sensitivity, and the substance has a good application prospect in the field of high explosives.

Description

Technical Field

[0001] The invention belongs to the field of energetic materials and relates to a method for synthesizing a fluoro gem-dinitropyrazole inner salt. Background Art

[0002] Energetic materials belong to a special branch of materials science. They can undergo violent redox reactions under certain external stimuli and release a large amount of energy. However, there is an essential contradiction between energy and stability in energetic compounds. It is difficult for currently known energetic materials to achieve a perfect balance between high energy and low sensitivity. In recent years, the preparation of energetic ion salts has become an effective method to balance energy release and chemical stability, but it is still limited by inherent defects such as strong hygroscopicity and relatively low density. In this context, energetic inner salt materials have become an emerging research hotspot due to their unique advantage of improving thermal stability through electrostatic interactions. However, due to the current limited design and synthesis strategies, the types of energetic inner salts are still scarce, and there are generally problems of insufficient thermal stability and high mechanical sensitivity, such as reference 1 (Du, Y.; Zhang, J.; Peng, P.; Su, H.; Li, S; Pang, S. Synthesis and Characterization of ThreePyrazolate Inner Diazonium Salts: Green, Powerful and Stable PrimaryExplosives. New . J . Chem .2017, 41 , 9244−9249.) and Reference 2 (Liu, T.; Liao, S.; Song,S.; Wang, K.; Jin, Y.; Zhang, Q. Combination of Gem -DinitromethylFunctionality and a 5-Amino-1,3,4-Oxadiazole Framework for ZwitterionicEnergetic Materials. Chem . Commun .2020, 56 (2), 209−212.) reported two energetic inner salt compounds a and b. In view of this, the present invention uses the intramolecular cyclization and inner salt to inner salt conversion strategy to prepare 2-amidino-3-geminodinitropyrazole inner salt (III) and 2-( N-nitro) amidino-3-fluorodinitromethylpyrazole salt (V), compared with the above a and b, the thermal stability of III and V ( T d ) is increased by >40°C, and the mechanical sensitivity (friction sensitivity IS and impact sensitivity FS) is significantly improved. The present invention can provide a new way to prepare new energetic inner salts with high thermal stability and high safety, and accelerate the application of energetic inner salts in weapon systems. Up to now, research on preparing and regulating the properties of energetic inner salts by intramolecular cyclization and utilizing the conversion of inner salts to inner salts has not been publicly reported. Summary of the invention

[0003] The invention overcomes the shortcomings of the prior art and provides a method for synthesizing a fluoro gem-dinitropyrazole inner salt.

[0004] The technical solution for achieving the purpose of the present invention is as follows: In one aspect, the present invention provides a fluoro-dinitropyrazole inner salt, the structural formula of which is as follows: .

[0005] The X-ray single crystal diffraction data of the crystal showed that the substance was monoclinic. P twenty one / n Space group; unit cell parameters are a=6.1807(3)Å, b=10.8702(5)Å, c=15.2531(10)Å, α=90°, β=100.483(5)°, γ=90°; crystal density at 100K: 1.840 g·cm -3 .

[0006] Another object of the present invention is to provide a method for synthesizing a fluoro gem-dinitropyrazole inner salt, the specific steps of which are as follows: (1) 4,4,4-Trinitrobutyraldehyde (I) reacts with aminoguanidine hydrochloride under hydrochloric acid catalysis to generate N -(4,4,4-Trinitrobutylimido)guanidine hydrochloride (II):

[0007] (2) N -(4,4,4-Trinitrobutylimino)guanidine hydrochloride (II) undergoes a ring-closing reaction under alkaline conditions to generate 2-amidino-3-geminopyrazole salt (III):

[0008] (3) 2-amidino-3-dinitropyrazole salt (III) undergoes nitration reaction in a nitric acid and sulfuric acid mixed system to generate 2-( N -nitro) amidino-3-geminodinitropyrazole salt (IV):

[0009] (4) 2-( N -nitro) amidino-3-gemin-dinitropyrazole salt (IV) reacts with xenon difluoride to generate 2-( N -nitro) amidino-3-fluorodinitromethylpyrazole salt (V):

[0010] Preferably, in step (1), the molar ratio of 4,4,4-trinitrobutyraldehyde (I) to aminoguanidine hydrochloride is 1:(1-1.2), the reaction temperature is 0-10°C, and the catalyst used is hydrochloric acid.

[0011] Preferably, in step (1), the solvent used in the reaction system is anhydrous ethanol, and the reaction time is 8 to 16 hours.

[0012] Preferably, the specific steps of step (1) are: dissolving 4,4,4-trinitrobutyraldehyde (I) and aminoguanidine hydrochloride in ethanol at 0-10°C, and adding a catalytic amount of hydrochloric acid, and then keeping the resulting mixture warm for 8-16 hours, filtering, and concentrating the resulting filtrate with a rotary evaporator to obtain a crude product, and then washing the crude product with ethyl acetate and drying to obtain N -(4,4,4-Trinitrobutylimido)guanidine hydrochloride intermediate (II).

[0013] Preferably, in step (2), N -(4,4,4-trinitrobutylimido)guanidine hydrochloride (II) is pretreated, the specific steps are: N -(4,4,4-trinitrobutylimido)guanidine hydrochloride is dissolved in ethanol with stirring, and a base (such as triethylamine, sodium methoxide, or sodium ethoxide) is added to adjust the pH to neutral.

[0014] Preferably, in step (2), the solvent used in the reaction system is anhydrous ethanol, and the reaction time is 2 to 8 hours.

[0015] Preferably, the specific steps of step (2) are: N -(4,4,4-trinitrobutylimido)guanidine hydrochloride intermediate (II) is dissolved in ethanol, and a base (such as triethylamine, sodium methoxide, sodium ethoxide, etc.) is added until the pH is neutral. Then, the mixture is heated under reflux for 2 to 8 hours under stirring, cooled, and filtered. The filter cake is washed with ethanol and dried under vacuum to obtain 2-amidino-3-gem-dinitropyrazole inner salt (III).

[0016] Preferably, in step (3), the nitration reaction temperature is -15 to 5°C, the volume ratio of concentrated nitric acid to concentrated sulfuric acid is 1:(1.5 to 2.0), and the reaction time is 2 to 6 hours.

[0017] Preferably, the specific steps of step (3) are: adding 2-amidino-3-dinitropyrazole inner salt (III) to 98% H2SO4 under stirring at -15 to 5°C, and then slowly adding concentrated HNO3. After the addition is completed, the reaction is kept warm for 2 to 6 hours. After the reaction is completed, the system is poured into ice water to quench, and extracted with ethyl acetate. The organic phase is washed with brine, and the solvent is evaporated to obtain 2-( N- Nitro) amidino-3-geminodinitropyrazole salt (IV).

[0018] Preferably, in step (4), the solvent used in the reaction system is anhydrous acetonitrile, the reaction temperature is 20 to 40° C., and the reaction time is 12 to 36 hours.

[0019] Preferably, in step (4), 2-( N The molar ratio of the di-nitro) amidino-3-gemin-dinitropyrazole salt (IV) to xenon difluoride is 1:(1-2.5).

[0020] Preferably, the specific steps of step (4) are: 2-( N -nitro) amidino-3- Nitropyrazole salt (IV) was dissolved in anhydrous acetonitrile, and xenon difluoride was added in batches under stirring. The mixture was reacted at 20-40°C for 12-36 hours. The solvent was removed in air, and the remaining solid was recrystallized from ethyl acetate to obtain 2-( N -nitro) amidino-3-fluorodinitromethylpyrazole inner salt (V).

[0022] Compared with the prior art, the present invention has the following obvious advantages: (1) The present invention discloses a method for preparing gem-dinitropyrazole inner salts based on intramolecular cyclization, and realizes the conversion of inner salts to inner salts through a functional group modification strategy, thereby effectively regulating the physicochemical properties of energetic inner salts.

[0023] (2) The safety performance of the 2-amidino-3-gemin-dinitropyrazole inner salt prepared by the present invention is better than that of most energetic inner salts reported so far, with a thermal decomposition temperature of 215°C, a friction sensitivity of more than 360N, and an impact sensitivity of more than 40J, and has application prospects as a non-sensitive energetic material. In addition, the 2-( N The thermal decomposition temperature of dinitro-3-nitro-dinitromethylpyrazole inner salt is 181°C, and the detonation velocity is greater than 8000 m s -1 , the explosion pressure is greater than 29GPa, and it has significant technical effects in the field of high explosives. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the accompanying drawings provide a corresponding introduction to the patent of the present invention: Figure 1 forN Crystal ellipsoid diagram of -(4,4,4-trinitrobutylimido)guanidine hydrochloride (II).

[0025] Figure 2 This is the crystal ellipsoid diagram of 2-amidino-3-dinitropyrazole salt (III).

[0026] Figure 3 is 2-( N Crystal ellipsoid diagram of di-nitro)guanyl-3-gem-dinitropyrazole salt (IV).

[0027] Figure 4 is 2-( N Crystal ellipsoid diagram of 3-fluoro-1-nitro-dinitromethylpyrazole salt (V).

[0028] Figure 5 for N TG-DSC graph of -(4,4,4-trinitrobutylimido)guanidine hydrochloride (II).

[0029] Figure 6 This is the TG-DSC diagram of 2-amidino-3-dinitropyrazole salt (III).

[0030] Figure 7 is 2-( N TG-DSC diagram of 3-nitro-dinitropyrazole (IV).

[0031] Figure 8 is 2-( N TG-DSC graph of 3-fluoro-dinitro-1-nitro)guanyl-3-fluoro-dinitromethyl-pyrazole salt (V).

[0032] Fig. 9 is 2-( N -nitro)amidino-3-fluorodinitromethylpyrazole salt (V) H NMR spectrum.

[0033] Fig.10 is 2-( N -nitro)amidino-3-fluorodinitromethylpyrazole salt (V) carbon NMR spectrum.

[0034] Fig.11 is 2-( N -Nitro)amidino-3-fluorodinitromethylpyrazole salt (V) NMR fluorine spectrum. DETAILED DESCRIPTION

[0035] The present invention will be further described below in conjunction with the embodiments.

[0036] Example 1 2.30 g (11.11 mmol) of 4,4,4-trinitrobanaldehyde and 1.23 g (11.13 mmol) of aminoguanidine hydrochloride were dissolved in 40 mL of ethanol solution at 5 °C, and then a catalytic amount of hydrochloric acid was added and stirred for 12 h. Filtered, the filtrate was concentrated by rotary evaporator to obtain a crude product, which was then washed with ethyl acetate and dried to obtain a light yellow N -(4,4,4-trinitrobutylimido)guanidine hydrochloride solid (II) 3.16 g, yield 95%. Further, the N -(4,4,4-trinitrobutylimido)guanidine hydrochloride crystals were analyzed using a Bruker Apex-II CCD single crystal diffractometer. The single crystal diffraction pattern is shown in Figure 1 As shown, the substance belongs to the monoclinic system. P twenty one / c Space group; unit cell parameters are a=14.9368(11)Å, b=11.0777(8)Å, c=7.7539(6)Å, α=90°, β=104.320(4)°, γ=90°; crystal density at 189.99K: 1.601 g·cm -3 NETZSCH STA 449F5 differential scanning calorimetry-thermogravimetric analysis (TG-DSC) was used to perform thermal analysis. The TG-DSC curve showed that ( Figure 5 ), the thermal decomposition temperature of the substance is 144℃ (heating rate: 5℃·min -1 ), the exothermic peak temperature is 151℃.

[0037] Example 2 Weigh 3.00g (10.00mmol) N -(4,4,4-trinitrobutylamino)guanidine hydrochloride (prepared in Example 1) was placed in a 100 mL three-necked flask, and 50 mL of ethanol was added and stirred. After the solid was completely dissolved, triethylamine was added until the pH of the solution was neutral, and the solution was stirred and refluxed for 6 h under heating. After cooling, it was filtered, and the filter cake was washed with ethanol and vacuum dried to obtain 1.39 g of 2-amidino-3-gem-dinitropyrazole inner salt (III), with a yield of 64%. Further, the 2-amidino-3-gem-dinitropyrazole inner salt crystal was analyzed using a Bruker D8 VENTURE single crystal diffractometer, and its single crystal diffraction pattern was as follows: Figure 2 As shown, the substance belongs to the monoclinic system. P twenty one / n Space group; unit cell parameters are a=8.3579(4) Å, b=12.6021(5) Å, c=8.3886(4) Å, α=90°, β=107.724(2)°, γ=90°; crystal density at 170 K: 1.706 g cm -3The thermal analysis was performed using a NETZSCH STA 449F5 differential scanning calorimeter-thermogravimetric instrument (TG-DSC). The TG-DSC curves showed that ( Figure 6 ), the thermal decomposition temperature of the substance is 215℃ (heating rate: 5℃·min -1 ), the exothermic peak temperature is 243℃. Compared with its ionic salt precursor N -(4,4,4-trinitrobutylamino)guanidine hydrochloride (Ⅱ), the thermal stability of this inner salt has been significantly improved. According to the BAM standard test method (the weight of the falling hammer is 5kg, the test sample amount is 20mg), the mechanical properties of 2-amidino-3-geminopyrazole inner salt (Ⅲ) were tested. The experimental results showed that the impact sensitivity of compound Ⅲ was >40J and the friction sensitivity was >360N, indicating that it has a dull characteristic.

[0038] Example 3 At 0°C, 0.50 g (2.30 mmol) of 2-amidino-3-dinitropyrazole inner salt (prepared in Example 2) was slowly added to 2.5 mL of 98% sulfuric acid. After complete dissolution, 1.25 mL of fuming nitric acid was added dropwise and the mixture was kept warm for 3 h. After the reaction was completed, the reaction solution was poured into 20 mL of ice water to quench, extracted with ethyl acetate (3×10 mL), the organic phase was washed with brine, and the solvent was evaporated to obtain 2-( N -nitro) amidino-3-geminopyrazole salt (IV) 0.27 g, yield 45%. Further, the 2-( N The crystals of 3-nitro-dinitropyrazole-1-yl-3-nitropyrazole inner salt were analyzed by XtaLAB single crystal diffractometer. Figure 3 As shown, the substance belongs to the monoclinic system. P twenty one / c Space group; unit cell parameters are a=14.6387(8)Å, b=10.0334(5)Å, c=6.6510(4)Å, α=90°, β=95.015(5)°, γ=90°; crystal density at 114K is 1.783 g·cm -3 The thermal analysis was performed using a NETZSCHSTA 449F5 differential scanning calorimeter-thermogravimetric instrument (TG-DSC). The TG-DSC curves showed that ( Figure 7 ), the thermal decomposition temperature of the substance is 215℃ (heating rate: 5℃·min -1 ), the exothermic peak temperature is 243℃.

[0039] Example 4 Take 0.26 g (1.00 mmol) of 2-( N-nitro) amidino-3-gem-dinitropyrazole inner salt (prepared in Example 3) was dissolved in 10 mL of anhydrous acetonitrile, and 0.25 g (1.50 mmol) of xenon difluoride was added in batches under stirring. The mixture was reacted at 30° C. for 20 h, and the reaction solvent was evaporated in the air. The remaining solid was recrystallized from ethyl acetate to obtain a light yellow 2-( N -nitro) amidino-3-fluorodinitromethylpyrazole inner salt solid (V) 0.173g, yield 62%. Further, the 2-( N The spectral analysis of 3-fluoro-dinitro-2-nitro-4-pyrazole was performed by Bruker BioSpin GmbH (400 MHz) nuclear magnetic resonance analyzer. 1 H NMR (400 MHz, DMSO- d 6): δ = 8.85, 5.98, 3.66, 3.43 ppm; 13 C NMR (101 MHz, DMSO- d 6): δ = 156.38, 152.24, 120.34, 57.15, 38.75 ppm; 19 F NMR (376 MHz, DMSO- d 6): δ = -115.60 ppm. The crystal structure of V was analyzed using ROD single crystal diffractometer, and its single crystal diffraction pattern is shown in Figure 4 As shown, the substance belongs to the monoclinic system. P twenty one / n Space group; unit cell parameters are a=6.1807(3)Å, b=10.8702(5)Å, c=15.2531(10)Å, α=90°, β=100.483(5)°, γ=90°; crystal density at 100K: 1.840 g·cm -3 The thermal analysis was performed using a NETZSCHSTA 449F5 differential scanning calorimeter-thermogravimetric instrument (TG-DSC). The TG-DSC curves showed that ( Figure 8 ), the thermal decomposition temperature of the substance is 181℃ (heating rate: 5℃·min -1 ), the exothermic peak temperature is 191℃, indicating that the substance has good thermal stability. The formation enthalpy of V was calculated using Gaussian 09 software package, and the detonation velocity and detonation pressure were predicted based on EXPLO5 6.05.02 software. The theoretical calculation results are: detonation velocity: 8329m s -1 , explosion pressure: 29.4GPa. According to the BAM standard test method (the weight of the falling hammer is 5kg, the test sample is 20mg), for 2-( NThe mechanical properties of compound V were tested. The experimental results showed that the friction sensitivity of compound V was 35J and the friction sensitivity was 320N, indicating that it has low sensitivity characteristics.

[0040] The performance of the products obtained in the related prior art and Examples 2 and 4 of the present invention include the following: .

Claims

1. A fluoro-dinitropyrazole inner salt, characterized in that: The structural formula is as follows: 。 2. The fluoro gem-dinitropyrazole inner salt according to claim 1, characterized in that The X-ray single crystal diffraction data of the crystal showed that the substance was monoclinic. P twenty one / n Space group; unit cell parameters are a=6.1807(3)Å, b=10.8702(5)Å, c=15.2531(10)Å, α=90°, β=100.483(5)°, γ=90°; crystal density at 100K: 1.840 g·cm -3 .

3. The method for synthesizing the fluoro gem-dinitropyrazole inner salt according to claim 1, characterized in that: The steps include: (1) 4,4,4-Trinitrobutyraldehyde (I) reacts with aminoguanidine hydrochloride under hydrochloric acid catalysis to generate N -(4,4,4-Trinitrobutylimido)guanidine hydrochloride (II): (2) N -(4,4,4-Trinitrobutylimino)guanidine hydrochloride (II) undergoes a ring-closing reaction under alkaline conditions to generate 2-amidino-3-geminopyrazole salt (III): (3) 2-amidino-3-dinitropyrazole salt (III) undergoes nitration reaction in a nitric acid and sulfuric acid mixed system to generate 2-( N -nitro) amidino-3-geminodinitropyrazole salt (IV): (4) 2-( N -nitro) amidino-3-gemin-dinitropyrazole salt (IV) reacts with xenon difluoride to generate 2-( N -nitro) amidino-3-fluorodinitromethylpyrazole salt (V):

4. The synthesis method according to claim 1, characterized in that In step (1), the molar ratio of 4,4,4-trinitrobanaldehyde (I) to aminoguanidine hydrochloride is 1:(1-1.2), the reaction temperature is 0-10°C, and the catalyst used is hydrochloric acid; The solvent used in the reaction system is anhydrous ethanol, and the reaction time is 8 to 16 hours.

5. The synthesis method according to claim 1, characterized in that In step (2), N -(4,4,4-trinitrobutylimido)guanidine hydrochloride (II) is pretreated, the specific steps are: N -(4,4,4-trinitrobutylimido)guanidine hydrochloride is dissolved in ethanol with stirring, and a base is added to adjust the pH to neutral; the solvent used in the reaction system is anhydrous ethanol, and the reaction time is 2 to 8 hours.

6. The synthesis method according to claim 1, characterized in that In step (3), the nitration reaction temperature is -15 to 5°C, the volume ratio of concentrated nitric acid to concentrated sulfuric acid is 1:(1.5 to 2.0), and the reaction time is 2 to 6 hours.

7. The synthesis method according to claim 1, characterized in that In step (4), the solvent used in the reaction system is anhydrous acetonitrile, the reaction temperature is 20 to 40° C., and the reaction time is 12 to 36 h; 2-( N The molar ratio of the di-nitro) amidino-3-gemin-dinitropyrazole salt (IV) to xenon difluoride is 1:(1-2.5).

8. An energetic material, characterized in that: The invention comprises the fluoro-dinitropyrazole inner salt as claimed in claim 1 or the fluoro-dinitropyrazole inner salt prepared by the method as claimed in any one of claims 3 to 7.

9. A high explosive, characterized in that: The invention comprises the fluoro-dinitropyrazole inner salt as claimed in claim 1 or the fluoro-dinitropyrazole inner salt prepared by the method as claimed in any one of claims 3 to 7.

10. An energetic combustion catalyst ligand, characterized in that: The invention comprises the fluoro-dinitropyrazole inner salt as claimed in claim 1 or the fluoro-dinitropyrazole inner salt prepared by the method as claimed in any one of claims 3 to 7.

Images