Preparation method of heat-resistant energetic material PTO

Abstract

The application discloses a preparation method of a heat-resistant energetic material PTO, which is synthesized from commercial 4-amino pyrazolo[3,4 d ] pyrimidine by one-step reaction in the presence of fuming nitric acid and concentrated sulfuric acid, and the yield is up to 75%. Compared with the prior art, the preparation method shortens the process by 3 steps, greatly reduces the reaction time, has relatively mild reaction conditions, and is simpler in process and easier in engineering amplification.

Description

Technical Field

[0001] The invention relates to a preparation method of a heat-resistant energetic material PTO, belonging to the technical field of energetic materials. Background Art

[0002] PTO (4-amino-5-nitro-7H-pyrazolo[3,4-d][1,2,3]triazine-2-oxide) is a heat-resistant energetic material synthesized by the China Academy of Engineering Physics in 2022 (Chem. Eng. J., 2022, 429, 132172). The density of PTO is 1.82 g·cm -3 , formation enthalpy 343.4 kJ·mol -1 , calculated explosion velocity reaches 8525m·s -1 The calculated detonation pressure is 29.4 GPa, with energy performance close to that of LLM-105 and significantly higher than that of traditional heat-resistant explosives such as TATB, PYX, and HNS. PTO has lower mechanical sensitivity than PYX and HNS, and a higher thermal decomposition temperature (up to 365°C), making it an ultra-high-temperature heat-resistant energetic material with excellent overall performance and broad application prospects.

[0003] Currently, PTO is synthesized using 3-amino-4-cyanopyrazole as the starting material through a four-step reaction process: cyclization with sodium azide, nitration, amination, and acidification. The first step requires reflux for 12 hours; the second step requires 4 hours at 50°C; and the third step requires 8 hours at 60°C. Although each step has high yields (>85%), the overall yield is only 71%. The product of the second step is a highly sensitive high-energy detonating explosive (Nat. Commun. 2019, 10, 1339). Therefore, the existing reaction route is highly risky, and the development of a new, simpler method for the synthesis of PTO is urgently needed. Summary of the Invention

[0004] The present invention overcomes the shortcomings of the prior art and provides a method for preparing a heat-resistant energetic material PTO, which adopts commercial raw materials and a one-step reaction to efficiently prepare PTO.

[0005] Technical solutions to achieve the purpose of the present invention:

[0006] A method for preparing a heat-resistant energetic material PTO, comprising:

[0007] (1) At low temperature, the compound 4-aminopyrazolo[3,4-d]pyrimidine was added in batches to 98 wt% concentrated H2SO4, and the mixture was stirred for a period of time. Then, fuming nitric acid was added dropwise. The reaction solution was gradually heated to a certain temperature and stirred at the same temperature for a certain period of time.

[0008]

[0009] (2) After the reaction is completed, the reaction solution is poured into ice water, the precipitate is collected by filtration, washed with cold water, and dried in air to obtain PTO.

[0010] Preferably, in step (1), the concentration of fuming nitric acid is >95 wt %.

[0011] Preferably, in step (1), the ratio of 4-aminopyrazolo[3,4-d]pyrimidine to 98wt% concentrated sulfuric acid is 1g:0.5~15mL, preferably 1g:1~7mL, more preferably 1g:2~5mL; the ratio of 4-aminopyrazolo[3,4-d]pyrimidine to fuming nitric acid is 1g:0.5~15mL, preferably 1g:4~15mL, more preferably 1g:4~8mL.

[0012] Preferably, in step (1), 4-aminopyrazolo[3,4-d]pyrimidine is added in batches to 98 wt% concentrated H2SO4 at -5 to 5°C, and the mixture is stirred for 0.5 h.

[0013] Preferably, in step (1), fuming nitric acid is added dropwise, and the temperature of the reaction solution is controlled not to exceed 10°C during the addition of fuming nitric acid.

[0014] Preferably, in step (1), the reaction solution is gradually heated to 40-80°C and stirred at this temperature for 2-15 hours. The reaction temperature is preferably 60-70°C, and the reaction time is preferably 5-15 hours.

[0015] Preferably, in step (2), after the reaction is completed, the reaction solution is poured into 3 to 4 times the volume of ice water, and the precipitate is collected by filtration within 15 minutes.

[0016] Compared with the prior art, the present invention has the following beneficial effects:

[0017] (1) The present invention adopts a one-pot method to prepare the PTO. This synthetic route only requires one step, which is three steps shorter than the existing synthetic route, and the reaction time is greatly shortened. The reaction conditions are relatively mild, the process is simpler, and it is easy to scale up by engineering.

[0018] (2) The maximum yield of the new method for preparing PTO of the present invention is close to 75%, which is significantly higher than the total yield of the prior art. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 This is the H NMR spectrum of PTO of the present invention.

[0020] Figure 2 It is the nuclear magnetic carbon spectrum of PTO of the present invention.

[0021] Figure 3 This is the DSC chart of the PTO of the present invention.

[0022] Figure 4 is the mass spectrum of PTO of the present invention.

[0023] Figure 5 It is the infrared spectrum of PTO of the present invention.

[0024] Figure 6 This is a single crystal structure diagram of the PTO of the present invention.

[0025] Figure 7 This is a unit cell stacking diagram of the PTO of the present invention. DETAILED DESCRIPTION

[0026] The following examples may enable those skilled in the art to more fully understand the present invention, but are not intended to limit the present invention in any way.

[0027] The synthesis route of the heat-resistant energetic material PTO of the present invention is as follows:

[0028]

[0029] Example 1:

[0030] 4-Aminopyrazolo[3,4-d]pyrimidine (1 g, 7.4 mmol, CAS: 2380-63-4) was added portionwise to 2 mL of H2SO4 (98 wt%) at -5°C. After stirring for 0.5 h, 5 mL of fuming HNO3 was added dropwise, maintaining the temperature below 5°C. After the addition, the reaction temperature was gradually raised to 60°C and allowed to react for 6 h. After completion of the reaction, the reaction solution was poured into 3-4 volumes of ice water. The precipitate was collected by filtration over 15 min, washed with cold water, and air-dried to yield 1.09 g of a yellow PTO solid with a yield of 74.7%.

[0031] Example 2:

[0032] Other conditions were the same as those in Example 1. Experiments were conducted at different temperatures. The experimental results are shown in Table 1.

[0033] Table 1 Experiments at different temperatures

[0034]

[0035] Example 3:

[0036] Other conditions were the same as those in Example 1. Experiments with different reaction times were conducted. The experimental results are shown in Table 2.

[0037] Table 2 Experiments with different reaction times

[0038]

[0039] Example 4:

[0040] Other conditions were the same as in Example 1, and experiments were conducted to test different amounts of fuming nitric acid. The experimental results are shown in Table 3.

[0041] Table 3 Experiments with different fuming nitric acid dosages

[0042]

[0043]

[0044] Example 5:

[0045] Other conditions were the same as those in Example 1. Experiments were conducted with different amounts of concentrated sulfuric acid (98 wt %). The experimental results are shown in Table 4.

[0046] Table 4 Experiments with different amounts of concentrated sulfuric acid (98 wt%)

[0047]

[0048] The above description is only a preferred embodiment of the present invention and does not constitute any form of limitation to the present invention. Any simple modification, equivalent replacement and improvement made by any technician familiar with the profession to the above embodiment without departing from the scope of the technical solution of the present invention and based on the technical essence of the present invention shall still fall within the scope of protection of the technical solution of the present invention.

[0049] Comparative Example 1:

[0050] 4-Aminopyrazolo[3,4-d]pyrimidine (1 g, 7.4 mmol) was added portionwise to 2 mL of H2SO4 (98 wt%) at -5°C. After stirring for 0.5 h, 5 mL of fuming HNO3 was added dropwise, maintaining the temperature below 5°C. After the addition, the reaction temperature was gradually raised to 20°C and allowed to react for 6 h. After the reaction, the reaction solution was poured into 3-4 times the volume of ice water. No product precipitated, indicating the reaction had failed.

[0051] Comparative Example 2:

[0052] 4-Aminopyrazolo[3,4-d]pyrimidine (1 g, 7.4 mmol) was added portionwise to 2 mL of H2SO4 (98 wt%) at -5°C. After stirring for 0.5 h, 5 mL of fuming HNO3 was added dropwise, maintaining the temperature below 5°C. After the addition, the reaction temperature was gradually raised to 90°C and allowed to react for 6 h. After the reaction, the reaction solution was poured into 3-4 times the volume of ice water. No product precipitated, indicating the reaction had failed.

[0053] Comparative Example 3:

[0054] 4-Aminopyrazolo[3,4-d]pyrimidine (1 g, 7.4 mmol) was added portionwise to 5 mL of fuming HNO₃ at -5°C, maintaining the temperature below 5°C. After the addition, the reaction temperature was gradually raised to 60°C and allowed to react for 6 hours. After completion, the reaction solution was poured into 3-4 volumes of ice water, and the precipitate was collected by filtration within 15 minutes. The yield was <10%. TLC revealed that the product contained unreacted 4-aminopyrazolo[3,4-d]pyrimidine and an unknown impurity in addition to PTO.

[0055] The PTO obtained in Examples 1 to 5 was dissolved in DMF and slowly evaporated at room temperature to obtain yellow block single crystals. The single crystal cultured from the sample described in Example 1 was subjected to X-ray single crystal diffraction test, and its crystal structure was as follows: Figure 6 and Figure 7 Its unit cell parameters are shown below:

[0056] Crystal system: monoclinic;

[0057] Point group: P21 / c;

[0058] Unit cell parameters: α=90°, β=109.622(11)°, γ=90°;

[0059] Unit cell volume:

[0060] Z = 4;

[0061] Density: 1.796 g·cm -3 (296K).

[0062] The PTO obtained in Examples 1 to 5 were characterized, and the spectral data were consistent. The analysis results of the sample described in Example 1 are given below, which are consistent with the characterization data reported in the literature.

[0063] like Figure 1 The H NMR spectrum shown is 1 H NMR (500MHz, DMSO-d6): δ15.10, 9.04, 7.54ppm.

[0064] like Figure 2 The NMR carbon spectrum shown, 13 C NMR (DMSO-d6): δ163.63, 156.66, 149.90, 87.37ppm.

[0065] like Figure 3 The DSC graph shown shows a decomposition temperature of 373.0°C and an exothermic peak temperature of 373.2°C.

[0066] like Figure 4The mass spectrum shown is m / z: 196.02 (MH).

[0067] like Figure 5 The infrared spectrum shown is IR(ATR): 3611,3405,3293,3260,3140,1634,1596,1542,1498,1445,1386,1330,12 99,1157,1060,965,861,831,796,770,741,721,701,646,615,593,552cm -1 .

[0068] Elemental analysis C4N3O7H3 (197.114): Calculated (found) C 24.37 (24.31), H 1.53 (1.55), N 49.74 (49.67).

Claims

1. A method for preparing heat-resistant energetic material PTO, characterized in that: Include: (1) At -5~5 ℃, add the compound 4-aminopyrazolo[3,4-d]pyrimidine in batches to 98 wt% concentrated H2SO4, keep warm and stir for a period of time, then add fuming nitric acid dropwise, gradually raise the reaction solution to 40~80 ℃ and keep warm and stir at this temperature for a certain period of time. ； (2) After the reaction is completed, the reaction solution is poured into ice water, the precipitate is collected by filtration, washed with cold water, and dried in air to obtain PTO.

2. The method according to claim 1, wherein In step (1), the concentration of fuming nitric acid is > 95 wt%.

3. The method according to claim 1, wherein In step (1), the ratio of 4-aminopyrazolo[3,4-d]pyrimidine to 98 wt% concentrated sulfuric acid is 1 g: 0.5-15 mL; the ratio of 4-aminopyrazolo[3,4-d]pyrimidine to fuming nitric acid is 1 g: 0.5-15 mL.

4. The method according to claim 1 or 3, wherein: In step (1), the ratio of 4-aminopyrazolo[3,4-d]pyrimidine to 98 wt% concentrated sulfuric acid is 1 g: 1~7 mL.

5. The method according to claim 1 or 3, wherein: In step (1), the ratio of 4-aminopyrazolo[3,4-d]pyrimidine to 98 wt% concentrated sulfuric acid is 1 g: 2~5 mL.

6. The method according to claim 1 or 3, wherein: In step (1), the ratio of 4-aminopyrazolo[3,4-d]pyrimidine to fuming nitric acid is 1 g: 4-15 mL.

7. The method according to claim 1 or 3, wherein: In step (1), the ratio of 4-aminopyrazolo[3,4-d]pyrimidine to fuming nitric acid is 1 g: 4-8 mL.

8. The method according to claim 1, wherein In step (1), 4-aminopyrazolo[3,4-d]pyrimidine was added in batches to 98 wt% concentrated H2SO4 at -5~5°C and stirred for 0.5h.

9. The method according to claim 1, wherein In step (1), fuming nitric acid is added dropwise, and the temperature of the reaction solution is controlled not to exceed 10°C during the addition of fuming nitric acid.

10. The method according to claim 1, wherein In step (1), the reaction solution is gradually heated to 40-80°C and stirred at this temperature for 2-15 hours.

11. The method according to claim 1 or 10, wherein: In step (1), the reaction solution is gradually heated to 60-70°C and stirred at this temperature for 5-15 hours.

12. The method according to claim 1, wherein In step (2), after the reaction is completed, the reaction solution is poured into 3 to 4 times the volume of ice water, and the precipitate is collected by filtration within 15 minutes.

Images