Synthesis method of 1-methyl-3, 4, 5-trinitropyrazole

Abstract

The invention provides a synthesis method of 1-methyl-3, 4, 5-trinitropyrazole, and belongs to the technical field of energetic materials. The synthesis method of 1-methyl-3, 4, 5-trinitropyrazole comprises the following steps: step S1, reacting a compound IV with an amination reagent to prepare a compound V; s2, directly oxidizing the compound V by a one-pot method to prepare 1-methyl-3, 4, 5-trinitropyrazole, or firstly removing a protecting group from the compound V by a fractional step method to prepare a compound VI, and then oxidizing the compound VI to prepare 1-methyl-3, 4, 5-trinitropyrazole; wherein the chemical structure of the compound IV is # imgabs0 #; the chemical structure of the compound V is # imgabs 1 #; and the chemical structure of the compound VI is # imgabs2. The method has the characteristics of mild reaction conditions, simplicity and convenience in operation, easiness in engineering amplification and the like.

Description

Technical Field

[0001] The present invention relates to the technical field of energetic materials, and particularly relates to a method for synthesizing 1-methyl-3,4,5-trinitropyrazole. Background Art

[0002] Energetic materials are a class of materials with characteristics of high-speed combustion or explosion, and play an irreplaceable role in fields such as aerospace and energy. Nitropyrazole energetic compounds often have characteristics such as high enthalpy of formation, low sensitivity, high density, good thermal stability, and environmental friendliness. Among them, 1-methyl-3,4,5-trinitropyrazole (MTNP) is a castable explosive carrier with excellent comprehensive performance. Compared with TNT, it has unique advantages in terms of energy density and detonation performance. However, the large-scale production of 1-methyl-3,4,5-trinitropyrazole (MTNP) is limited by an inefficient and high-risk synthesis process, and its process scale-up and practical application are restricted.

[0003] Currently, the synthesis methods of 1-methyl-3,4,5-trinitropyrazole (MTNP) mainly focus on paths such as direct nitration method, iodonitration method, catalytic nitration method, trinitropyrazole methylation method, amino oxidation method, etc. The direct nitration method usually uses 1-methylpyrazole as a raw material and fuming nitric acid / fuming sulfuric acid, etc. as nitrating reagents. The reaction conditions are harsh, there are many side reactions, and the safety is poor. The iodonitration method uses 1-methylpyrazole as a raw material, and after iodination and then nitration. Although it can avoid some nitration risks, it relies on high-cost iodinating reagents and has problems such as low iodination efficiency and many impurities. The catalytic nitration method uses 1-methylpyrazole as a raw material and Bi(NO 3 ) 3 / montmorillonite K-10, etc. as nitration catalysts. Although it conforms to the concept of green chemistry, it is difficult to repeat. The trinitropyrazole methylation method uses trinitropyrazole (TNP) as a raw material and synthesizes 1-methyl-3,4,5-trinitropyrazole (MTNP) through N-methylation. However, the synthesis process of TNP is complex and the yield is low. The amino oxidation method uses 4-amino-3,5-dinitropyrazole (LLM-116) or 4-amino-1-methyl-3,5-dinitropyrazole, etc. as raw materials and synthesizes 1-methyl-3,4,5-trinitropyrazole (MTNP) through amino oxidation. However, the reaction conditions in the synthesis of raw materials such as LLM-116 are harsh (high temperature, high pressure). Therefore, exploring a new synthesis method of 1-methyl-3,4,5-trinitropyrazole (MTNP) with low cost and easy process scale-up is of great significance for the engineering scale-up and application of 1-methyl-3,4,5-trinitropyrazole (MTNP), etc. Summary of the Invention

[0004] The present invention aims to provide a method for synthesizing 1-methyl-3,4,5-trinitropyrazole, which has characteristics such as mild reaction conditions, simple operation, and easy engineering scale-up.

[0005] A synthesis method of 1-methyl-3,4,5-trinitropyrazole, comprising the following steps:

[0006] Step S1, reacting compound Ⅳ with an amination reagent to obtain compound Ⅴ;

[0007] Step S2, directly oxidizing compound Ⅴ by one-pot method to obtain 1-methyl-3,4,5-trinitropyrazole, or first removing the protecting group from compound Ⅴ by a stepwise method to obtain compound Ⅵ, and then oxidizing compound Ⅵ to obtain 1-methyl-3,4,5-trinitropyrazole;

[0008] Among them, the chemical structure of compound Ⅳ is:

[0009] ;

[0010] In the formula, X is Br, Cl, F;

[0011] The chemical structure of compound V is:

[0012] ;

[0013] In the formula, R is -CH 2 C 6 H 5 、-CH 2 C 6 H 4 OCH 3 、-C(CH 3 ) 3 、-C(CH 3 ) 2 CH 2 C(CH 3 ) 3 ;

[0014] The chemical structure of compound Ⅵ is:

[0015] .

[0016] Furthermore, in the step S1, the preparation process of compound Ⅳ is: first reacting compound Ⅰ with a nitrating reagent to obtain compound Ⅲ, and then reacting compound Ⅲ with a methylation reagent;

[0017] Among them, the chemical structure of compound Ⅰ is:

[0018] ;

[0019] In the formula, X is Br, Cl, F;

[0020] The chemical structure of compound Ⅲ is:

[0021] ;

[0022] In the formula, X is Br, Cl, or F;

[0023] Alternatively, in the step S1, the preparation process of compound Ⅳ is: obtained by reacting compound Ⅱ with a nitrating reagent;

[0024] Among them, the chemical structure of compound Ⅱ is:

[0025] ;

[0026] In the formula, X is Br, Cl, or F.

[0027] Further, in the step S1, the nitrating reagent is a mixture of concentrated sulfuric acid and fuming nitric acid, and the volume ratio of the two is 2 - 10:1.

[0028] Further, in the step S1, the methylation reagent is dimethyl sulfate, methyl p-toluenesulfonate, methyl trifluoromethanesulfonate, methyl methanesulfonate, dimethyl carbonate, iodomethane, bromomethane, or chloromethane, and the molar ratio of compound Ⅲ to the methylation reagent is 1:1 - 6.

[0029] Further, in the step S1, the molar ratio of compound Ⅳ to the amination reagent is 1:1 - 20.

[0030] Further, in the step S1, when compound Ⅳ reacts with the amination reagent, an acetonitrile - water mixed system, a petroleum ether - water mixed system, 1,4 - dioxane, methanol, ethanol, N,N - dimethylformamide, or the amination reagent is used as the solvent.

[0031] Further, in the step S1, the reaction temperature is 20 - 160 °C.

[0032] Further, in the step S2, when directly oxidizing to obtain 1 - methyl - 3,4,5 - trinitropyrazole by one - pot method, a concentrated sulfuric acid - hydrogen peroxide mixed oxidation system, a trifluoroacetic acid - hydrogen peroxide mixed oxidation system, or a potassium peroxymonosulfate - sulfuric acid - water mixed oxidation system is used;

[0033] Alternatively, in the step S2, when removing the protecting group first to obtain compound Ⅵ by a step - by - step method, concentrated sulfuric acid, trifluoroacetic acid, perchloric acid, nitric acid, methanesulfonic acid, or trifluoromethanesulfonic acid is used, and then when oxidizing to obtain 1 - methyl - 3,4,5 - trinitropyrazole, a concentrated sulfuric acid - hydrogen peroxide mixed oxidation system, a trifluoroacetic acid - hydrogen peroxide mixed oxidation system, a potassium peroxymonosulfate - sulfuric acid - water mixed oxidation system, an acetic acid - hydrogen peroxide mixed oxidation system, an acetic anhydride - hydrogen peroxide mixed oxidation system, a sodium perborate - acetic acid mixed oxidation system, or potassium permanganate is used.

[0034] Further, in the step S2, when directly oxidizing to prepare 1-methyl-3,4,5-trinitropyrazole by the one-pot method, a concentrated sulfuric acid-hydrogen peroxide mixed oxidation system is used, the volume ratio of concentrated sulfuric acid to hydrogen peroxide is 2:1, and the mass concentration of hydrogen peroxide is 50%.

[0035] Further, in the step S2, when oxidizing step by step to prepare 1-methyl-3,4,5-trinitropyrazole, a concentrated sulfuric acid-hydrogen peroxide mixed oxidation system is used, the volume ratio of concentrated sulfuric acid to hydrogen peroxide is 2:1, and the mass concentration of hydrogen peroxide is 50%.

[0036] The beneficial effects of the present invention are as follows:

[0037] The present invention uses 4-halo-1-methyl-3,5-dinitropyrazole (i.e., compound Ⅳ) as a raw material, and directly oxidizes it by the one-pot method after amination to prepare 1-methyl-3,4,5-trinitropyrazole MTNP, or first removes the protecting group step by step to prepare compound Ⅵ, and then oxidizes compound Ⅵ to prepare 1-methyl-3,4,5-trinitropyrazole MTNP. It has the characteristics of mild reaction conditions, simple operation, and easy engineering scale-up. Description of the Drawings

[0038] In order to more clearly illustrate the technical solutions in the embodiments of the present application or the prior art, the following will briefly introduce the drawings required to be used in the description of the embodiments or the prior art. Obviously, the following drawings are only some embodiments of the present application. For those of ordinary skill in the art, other drawings can be obtained based on these drawings without creative efforts.

[0039] Figure 1 It is the overall synthesis route diagram of 1-methyl-3,4,5-trinitropyrazole in the embodiment.

[0040] Figure 2 It is the synthesis route diagram of 1-methyl-3,4,5-trinitropyrazole in Example 1.

[0041] Figure 3 It is the line graph of the influence of the feeding amount of benzylamine on the yield in Example 1.

[0042] Figure 4 It is the line graph of the influence of different reaction temperatures on the yield in Example 1.

[0043] Figure 5 It is the line graph of the influence of the amount of concentrated sulfuric acid used on the yield in Example 1.

[0044] Figure 6 It is the line graph of the influence of the amount of hydrogen peroxide used on the yield in Example 1.

[0045] Figure 7It is the synthetic route diagram of 1-methyl-3,4,5-trinitropyrazole (MNTP) in Example 2.

[0046] Figure 8 It is the synthetic route diagram of 1-methyl-3,4,5-trinitropyrazole (MNTP) in Example 3.

[0047] Figure 9 It is the synthetic route diagram of 1-methyl-3,4,5-trinitropyrazole (MNTP) in Example 4. Detailed implementation manners

[0048] The embodiments of the invention will be described in detail below with reference to the accompanying drawings.

[0049] Figure 1 It is the overall synthetic route diagram of 1-methyl-3,4,5-trinitropyrazole in the examples. As Figure 1 shown, the synthetic method of this 1-methyl-3,4,5-trinitropyrazole (MTNP) includes the following steps:

[0050] Step S1: React compound Ⅳ with an amination reagent to obtain compound Ⅴ;

[0051] Step S2: Directly oxidize compound Ⅴ by one-pot method to obtain 1-methyl-3,4,5-trinitropyrazole (MTNP), or first remove the protecting group from compound Ⅴ by a stepwise method to obtain compound Ⅵ, and then oxidize compound Ⅵ to obtain 1-methyl-3,4,5-trinitropyrazole (MTNP);

[0052] Among them, the chemical structure of compound Ⅳ is:

[0053] ;

[0054] In the formula, X is Br, Cl, F;

[0055] The chemical structure of compound V is:

[0056] ;

[0057] In the formula, R is -CH 2 C 6 H 5 , -CH 2 C 6 H 4 OCH 3 , -C(CH 3 ) 3 , -C(CH 3 ) 2 CH 2 C(CH 3 ) 3 ;

[0058] The chemical structure of Compound VI is as follows:

[0059] .

[0060] Among them, in the step S1, the preparation process of Compound IV is as follows: Compound I first reacts with a nitrating reagent to obtain Compound III, and then Compound III reacts with a methylation reagent to obtain it;

[0061] The chemical structure of Compound I is as follows:

[0062] ;

[0063] In the formula, X is Br, Cl, or F;

[0064] The chemical structure of Compound III is as follows:

[0065] ;

[0066] In the formula, X is Br, Cl, or F;

[0067] Alternatively, in the step S1, the preparation process of Compound IV is as follows: Compound II reacts with a nitrating reagent to obtain it;

[0068] Among them, the chemical structure of Compound II is as follows:

[0069] ;

[0070] In the formula, X is Br, Cl, or F.

[0071] The following is illustrated by more specific examples.

[0072] Example 1

[0073] Using 4-chloropyrazole (1) as a raw material, it is nitrated to obtain 4-chloro-3,5-dinitropyrazole (2), and then methylated to obtain 4-chloro-1-methyl-3,5-dinitropyrazole (3); using 4-bromo-1-methylpyrazole (4) as a raw material, it is nitrated to obtain 4-bromo-1-methyl-3,5-dinitropyrazole (5); 4-chloro-1-methyl-3,5-dinitropyrazole (3) and 4-bromo-1-methyl-3,5-dinitropyrazole (5) react with benzylamine respectively to obtain 4-benzylamino-1-methyl-3,5-dinitropyrazole (6), and after stepwise debenzylation and oxidation or one-pot direct oxidation, 1-methyl-3,4,5-trinitropyrazole MTNP is obtained. The synthetic route is as Figure 2 shown.

[0074] Synthesis and Characterization of 4-Chloro-3,5-dinitropyrazole (2)

[0075] Add 30 mL of concentrated sulfuric acid (98%) to a two-necked flask, and slowly add 4-chloropyrazole (1) (3.06 g, 30.30 mmol). After complete dissolution, slowly add dropwise 4 mL of fuming nitric acid (98%). After the addition is complete, gradually heat up to 100 °C. After the reaction is completed, cool to room temperature, pour the reaction solution into crushed ice, extract with ethyl acetate, wash with water, dry over anhydrous magnesium sulfate, and concentrate under reduced pressure to obtain white solid 4-chloro-3,5-dinitropyrazole (2) with a yield of 80.1% and a melting point of 158.2 - 159.6 °C. IR (KBr, ν / cm -1 ): 3440, 2930, 1635, 1572, 1556, 1532, 1486, 1421, 1337, 1210, 1117, 1003, 839, 818, 762.

[0076] Synthesis and Characterization of 4-Chloro-1-methyl-3,5-dinitropyrazole (3)

[0077] Add 4-chloro-3,5-dinitropyrazole (2) (1.16 g, 6.04 mmol) to a solution of NaHCO 3 (1.02 g, 12.14 mmol) and 10 mL of water, and stir for 10 min. Then add dimethyl sulfate Me 2 SO 4 (1.52 g, 12 mmol), and stir at room temperature for 4 h. Filter the precipitated solid, wash with water, and dry to obtain white solid 4-chloro-1-methyl-3,5-dinitropyrazole (3) with a yield of 95.6% and a melting point of 97.7 - 98.1 °C. IR (KBr, ν / cm -1 ): 3447, 2870, 1560, 1504, 1437, 1376, 1331, 1304, 1046, 880, 760; 1 H NMR (400 MHz, DMSO-d 6 , 25 °C) δ: 4.28 (s, 3H); 13 C NMR (101 MHz, DMSO-d 6 , 25 °C) δ: 148.32 (s), 143.45 (s), 106.09 (s), 43.97 (s).

[0078] Synthesis and Characterization of 4-Bromo-1-methyl-3,5-dinitropyrazole (5)

[0079] At 0~10 °C, 1-methyl-4-bromopyrazole (4) (4.00 g, 25.01 mmol) was added portionwise to 16 mL of concentrated sulfuric acid (98%). After complete dissolution, 8 mL of a mixed acid of concentrated sulfuric acid and fuming nitric acid (volume ratio of concentrated sulfuric acid to fuming nitric acid is 1:1) was slowly added dropwise. After the addition was complete, the temperature was raised to 100 °C. After the reaction was completed, the reaction solution was cooled and poured into crushed ice, filtered, washed, and dried to obtain white solid 4-bromo-1-methyl-3,5-dinitropyrazole (5) with a yield of 78.9% and a melting point of 143.9~144.5 °C. IR (KBr, ν / cm -1 ): 2854, 1568, 1330, 867, 742; 1H NMR (400 MHz, DMSO-d 6 , 25 °C) δ: 4.28 (s, 3H); 13CNMR (101 MHz, DMSO-d 6 , 25 °C) δ: 149.78 (s), 1435.13(s), 91.27 (s), 43.99 (s).

[0080] Synthesis and Characterization of 4-Benzylamino-1-methyl-3,5-dinitropyrazole (6)

[0081] In this example, using 4-chloro-1-methyl-3,5-dinitropyrazole (3) as the raw material and benzylamine as the amination reagent, the influence of different solvents on the yield of 4-benzylamino-1-methyl-3,5-dinitropyrazole (6) was investigated through single-factor experimental design. The solvent influence is shown in Table 1. The results show that when petroleum ether-water is used as the solvent, the side reactions are relatively few and the yield of 4-benzylamino-1-methyl-3,5-dinitropyrazole (6) is relatively high.

[0082] Table 1 Solvent Influence

[0083] Solvent Reaction Temperature t / ℃ Yield / % 1,4-Dioxane 101 55.5 N,N-Dimethylformamide (DMF) rt 62.8 Petroleum Ether-Water (3:1) rt 69.5 Ethanol 78 48.3 Methanol 64 46.5 Acetonitrile-Water Mixture 76 46.3

[0084] Note: n(benzylamine):n(4-chloro-1-methyl-3,5-dinitropyrazole (3)) = 3:1.

[0085] In this example, using 4-chloro-1-methyl-3,5-dinitropyrazole (3) as the raw material and benzylamine as the amination reagent, with petroleum ether-water (volume ratio 3:1) as the reaction solvent, at room temperature, and the reaction duration of 12 h, the influence of the benzylamine feeding amount on the yield of 4-benzylamino-1-methyl-3,5-dinitropyrazole (6) was investigated through single-factor experimental design as Figure 3 shown. The results show that appropriately increasing benzylamine can increase the amination reaction rate and yield and reduce the formation of hydrolysis by-products.

[0086] In this example, 4-chloro-1-methyl-3,5-dinitropyrazole (3) was used as the raw material, benzylamine as the amination reagent (the molar ratio of benzylamine to 4-chloro-1-methyl-3,5-dinitropyrazole (3) was 6:1), petroleum ether-water (3:1) as the reaction solvent, and the effect of different reaction temperatures on the yield of 4-benzylamino-1-methyl-3,5-dinitropyrazole (6) was investigated through single-factor experimental design as Figure 4 shown below. The results showed that as the reaction temperature increased, the yield of 4-benzylamino-1-methyl-3,5-dinitropyrazole (6) first increased and then decreased, reaching a peak at 35 °C, and within the range of 25 - 55 °C, the yield of 4-benzylamino-1-methyl-3,5-dinitropyrazole (6) was higher than 80%. Thus, it can be seen that this amination reaction has good temperature adaptability, which is beneficial to process scale-up.

[0087] Therefore, a more suitable preparation process is as follows:

[0088] 4-chloro-1-methyl-3,5-dinitropyrazole (3) (0.52 g, 2.52 mmol) was dissolved in a mixture of 20 mL of petroleum ether and an appropriate amount of water, and benzylamine (1.64 g, 15.31 mmol) and potassium carbonate (0.14 g, 1.01 mmol) were added. The reaction was carried out at 35 °C until the raw materials disappeared (monitored by TLC), acidified to pH = 1 with 10% HCl, cooled, filtered by suction, washed with water to obtain the first part of the product. The filtrate was extracted with ethyl acetate, washed with water, rotary evaporated, and dried to obtain the second part of the product. After drying, the two parts of the product were combined to obtain a bright yellow solid, 4-benzylamino-1-methyl-3,5-dinitropyrazole (6), with a yield of 89.6% and a melting point of 89.8 - 90.3 °C. IR (KBr, ν / cm -1 ): 3447, 2938, 2846, 1615, 1518, 1478, 1456, 1408, 1387, 1315, 1299, 1069, 896, 784; 1 H NMR (400 MHz, DMSO-d 6 , 25 °C) δ: 7.74 s, 1H), 7.23 (d, 5H), 4.65 (s, 2H), 4.13 (s, 3H); 13 C NMR (101 MHz, DMSO-d 6 , 25 °C) δ: 141.63 (s), 138.88 (s), 134.27 (s), 129.03 (s), 127.66 (s), 48.64 (s), 43.56 (s).

[0089] 4-Bromo-1-methyl-3,5-dinitropyrazole (5) (0.63 g, 2.52 mmol) was dissolved in 10 mL of DMF, and benzylamine (1.62 g, 15.15 mmol), potassium carbonate (0.14 g, 1.01 mmol), and KI (0.042 g, 0.25 mmol) were added thereto. The reaction was carried out at room temperature until the raw materials disappeared (monitored by TLC). An appropriate amount of water was poured into the reaction solution, filtered, washed with water and dried to obtain a bright yellow solid 4-benzylamino-1-methyl-3,5-dinitropyrazole (6) with a yield of 55.8% and a melting point of 89.8 - 90.3 °C. IR (KBr, ν / cm -1 ): 3447, 2938, 2846, 1615, 1518, 1478, 1456, 1408, 1387, 1315, 1299, 1069, 896, 784; 1 1H NMR (400 MHz, DMSO-d 6 , 25 °C) δ: 7.74 (s, 1H), 7.23 (d, J = 36.3 Hz, 5H), 4.65 (s, 2H), 4.13 (s, 3H); 13 13C NMR (101 MHz, DMSO-d 6 , 25 °C) δ: 141.63 (s), 138.88 (s), 134.27 (s), 129.03 (s), 127.66 (s), 48.64 (s), 43.56 (s).

[0090] Stepwise Synthesis and Characterization of 1-Methyl-3,4,5-trinitropyrazole (MTNP)

[0091] In this example, different acids were tried to catalyze the debenzylation. The results showed that due to the weak acidity, acetic acid could not achieve the debenzylation reaction of 4-benzylamino-1-methyl-3,5-dinitropyrazole (6); when strong acid systems such as trifluoroacetic acid, concentrated sulfuric acid (98%), and hexafluoroisopropanol-aluminum chloride mixed system were used, the debenzylation product, that is, 4-amino-1-methyl-3,5-dinitropyrazole (7), could be obtained. The effects of debenzylation reagents on the yield of 4-amino-1-methyl-3,5-dinitropyrazole (7) are shown in Table 2.

[0092] Table 2 Effects of Debenzylation Reagents on the Yield

[0093] Debenzylation Reagent Yield / % Acetic Acid (AcOH) - <![CDATA[Trifluoroacetic acid (CF 3 COOH)]]> 75.6 <![CDATA[Hexafluoroisopropanol-aluminum chloride mixed system (HFIP-AlCl 3 ).]]> 90.7 <![CDATA[Concentrated sulfuric acid (H 2 SO 4 )]]> 95.2

[0094] Note: Reaction conditions: H 2 SO 4 2 mL, CF 32 mL of COOH, 2 mL of AcOH, 5 mL of HFIP, AlCl 3 (0.5 g, 3.75 mmol), 4-benzylamino-1-methyl-3,5-dinitropyrazole (6) (0.28 g, 1.01 mmol), T = 25 °C.

[0095] In this example, a mixed sulfuric acid-hydrogen peroxide oxidation system (50% H 2 O 2 / H 2 SO 4 ), a trifluoroacetic acid-hydrogen peroxide mixed oxidation system (50% H 2 O 2 / CF 3 COOH), a sodium perborate-acetic acid mixed oxidation system (NaBO 3 ·4H 2 O / AcOH), and a potassium peroxymonosulfate-sulfuric acid-water mixed oxidation system (Oxone / water-H 2 SO 4 ) and other oxidation systems were used to study the oxidation of the amino group of 4-amino-1-methyl-3,5-dinitropyrazole (7). The results are shown in Table 3. The results show that the above oxidation systems can all oxidize the amino group to obtain 1-methyl-3,4,5-trinitropyrazole MTNP. Among them, when the mixed sulfuric acid-hydrogen peroxide oxidation system (50% H 2 O 2 / H 2 SO 4 ) is used as the oxidation system, the yield of 1-methyl-3,4,5-trinitropyrazole MTNP is relatively high.

[0096] Table 3 Effect of different oxidation systems on the yield

[0097] Oxidizing Agent Yield / % <![CDATA[Concentrated sulfuric acid - hydrogen peroxide mixed oxidation system (50% H 2 O 2 / H 2 SO 4 ).]]> 48.7 <![CDATA[Trifluoroacetic acid - hydrogen peroxide mixed oxidation system (50% H 2 O 2 / CF 3 COOH)]]> 46.5 <![CDATA[Sodium perborate - acetic acid mixed oxidation system (NaBO 3 ·4H 2 O / AcOH)]]> 44.7 <![CDATA[Potassium peroxymonosulfate-sulfuric acid-water mixed oxidation system (Oxone / water-H 2 SO 4 )]]> 43.6

[0098] Note: Reaction conditions: H 2 SO 4 1.3 mL, 50% H 2 O 2 0.65 mL, CF 3 COOH 1.3 mL, AcOH 4 mL, water 8 mL, NaBO 3 ·4H 2 O (0.41 g, 2.7 mmol), Oxone (0.83 g, 1.36 mmol), 4-amino-1-methyl-3,5-dinitropyrazole (7) (0.10 g, 0.54 mmol).

[0099] Therefore, a more suitable preparation process is as follows:

[0100] At room temperature, 4-benzylamino-1-methyl-3,5-dinitropyrazole (6) (0.61 g, 2.20 mmol) was dissolved in 3 mL of concentrated sulfuric acid (98%), and stirred until the raw materials disappeared. The reaction solution was poured into ice water, and the pH was adjusted to 7-8 with saturated NaHCO 3 aqueous solution, extracted with ethyl acetate, washed with saturated brine, dried over anhydrous magnesium sulfate, and concentrated in vacuo to obtain 4-amino-1-methyl-3,5-dinitropyrazole (7) with a yield of 95.2% and a melting point of 159.7-163.2 °C. IR (KBr, ν / cm -1 ): 3476, 3457, 3361, 3336, 2928, 1644, 1634, 1569, 1478, 1437, 1391, 1352, 1112, 1035, 887, 835, 783, 757, 665, 621; 1 1H NMR (400 MHz, DMSO-d 6 , 25 °C) δ: 7.26 (s, 2H), 4.20 (s, 3H); 13 13C NMR (101 MHz, DMSO-d 6 , 25 °C) δ: 139.64 (s), 132.70 (s), 130.80 (s), 43.41 (s).

[0101] At 0 °C, 4-amino-1-methyl-3,5-dinitropyrazole (7) (0.10 g, 0.52 mmol) was dissolved in 1.3 mL of concentrated sulfuric acid (98%), and 0.65 mL of H 2 O 2 (50%) was slowly added dropwise, and the reaction temperature was controlled at about 10 °C. After the addition was completed, the temperature was raised to 20 °C. After monitoring the reaction by TLC and completion, it was cooled to room temperature. The reaction solution was poured into crushed ice, extracted with ethyl acetate, dried, and rotary evaporated to obtain a pale yellow solid 1-methyl-3,4,5-trinitropyrazole MTNP with a yield of 62.3% and a melting point of 90.4-92.4 °C. IR (KBr, ν / cm -1 ): 2860, 1581, 1338, 1051, 904, 844, 777; 1 1H NMR (400 MHz, DMSO-d 6 , 25 °C) δ: 4.27 (s, 3H); 13 13C NMR (101 MHz, DMSO-d 6, 25 °C) δ: 155.60 (s), 147.29 (s), 108.39 (s), 43.48 (s).

[0102] One-Pot Synthesis and Characterization of 1-Methyl-3,4,5-trinitropyrazole (MTNP)

[0103] Concentrated sulfuric acid - hydrogen peroxide mixed oxidation system (50% H 2 O 2 / H 2 SO 4 ), trifluoroacetic acid - hydrogen peroxide mixed oxidation system (50% H 2 O 2 / CF 3 COOH), potassium peroxymonosulfate - sulfuric acid - water mixed oxidation system (Oxone / water - H 2 SO 4 ), etc. are all strongly acidic systems, and it is expected to simultaneously achieve the debenzylation and oxidation reactions of 4-benzylamino-1-methyl-3,5-dinitropyrazole (6), thereby reducing the operation steps. The experimental results in this example show that using these oxidation systems can directly oxidize to 1-methyl-3,4,5-trinitropyrazole MTNP in one-pot method, and the results are shown in Table 5. When using the potassium peroxymonosulfate - sulfuric acid - water mixed oxidation system (Oxone / water - H 2 SO 4 ), the reaction rate is slow and the yield is low. Comparatively speaking, the more suitable oxidation system is the concentrated sulfuric acid - hydrogen peroxide mixed oxidation system (50% H 2 O 2 / H 2 SO 4 ), and its yield of 1-methyl-3,4,5-trinitropyrazole MTNP is relatively high.

[0104] Table 5 Effects of different oxidation systems on the yield of one-pot synthesis

[0105] Oxidizing Agent Yield / % <![CDATA[Concentrated sulfuric acid - hydrogen peroxide mixed oxidation system (50% H 2 O 2 / H 2 SO 4 ).]]> 51.6 <![CDATA[Trifluoroacetic acid-hydrogen peroxide mixed oxidation system (50% H 2 O 2 / CF 3 COOH)]]> 48.9 <![CDATA[Potassium peroxymonosulfate - sulfuric acid - water mixed oxidation system (Oxone / water-H 2 SO 4 )]]> 40.8

[0106] Note: Reaction conditions: H 2 SO 4 2 mL, CF 3 COOH 2 mL, 50% H 2 O 2 0.65 mL, Oxone (1.53 g, 2.50 mmol), water 10 mL, 4-benzylamino-1-methyl-3,5-dinitropyrazole (6) (0.28 g, 1.01 mmol).

[0107] In this example, the concentrated sulfuric acid - hydrogen peroxide mixed oxidation system (50% H 2 O2 / H 2 SO 4 ), References (He C, Zhang J, Parrish D A, et al. 4-Chloro-3, 5-dinitropyrazole: a precursor for promising insensitive energetic compounds[J]. Journal of Materials Chemistry A, 2013, 1(8): 2863-2868; Qiao R. Synthesis and application of 4-amino-3, 5-dinitropyrazole and its derivatives[D]. Taiyuan: North University of China, 2015.) sets the amount of 4-benzylamino-1-methyl-3,5-dinitropyrazole (6) to 0.06 g and the amount of hydrogen peroxide (50%) to 0.5 mL. The effect of the amount of concentrated sulfuric acid (98%) on the yield of 1-methyl-3,4,5-trinitropyrazole MTNP was investigated in a single-factor experiment as follows Figure 5 shown in the figure. The results show that the target compound can be obtained under all conditions, and with the increase of sulfuric acid amount, the yield of 1-methyl-3,4,5-trinitropyrazole MTNP first increases and then decreases; when the amount of concentrated sulfuric acid is 0.8 mL, the yield of 1-methyl-3,4,5-trinitropyrazole MTNP is relatively high.

[0108] When the amount of 4-benzylamino-1-methyl-3,5-dinitropyrazole (6) is 0.06 g and the amount of concentrated sulfuric acid (98%) is 0.8 mL, the effect of the amount of hydrogen peroxide on the yield of 1-methyl-3,4,5-trinitropyrazole MTNP was investigated in a single-factor experiment in this example as follows Figure 6 shown in the figure. The results show that with the increase of the amount of hydrogen peroxide, the yield of 1-methyl-3,4,5-trinitropyrazole MTNP first increases and then decreases slightly; when the amount of hydrogen peroxide is 0.4 mL, the yield of 1-methyl-3,4,5-trinitropyrazole MTNP reaches the highest of 60.5%. Considering comprehensively, the amount of sulfuric acid is 0.8 mL and the amount of hydrogen peroxide is 0.4 mL are the better debenzylation oxidation conditions for 4-benzylamino-1-methyl-3,5-dinitropyrazole (6).

[0109] Therefore, a more suitable preparation process is as follows:

[0110] At room temperature, dissolve 4-benzylamino-1-methyl-3,5-dinitropyrazole (4) (0.06 g, 0.22 mmol) in 0.8 mL of concentrated sulfuric acid (98%), stir for about 30 min. At this time, TLC shows that the raw materials have reacted completely. Slowly add 0.4 mL of H 2 O 2(50%). The solution was stirred at 0 °C for about 3 h, then transferred to room temperature. During the stirring process, the temperature would rise. As the reaction proceeded, when the solution changed from bright yellow to light yellow until the raw materials disappeared (monitored by TLC), the reaction solution was poured into crushed ice, filtered, washed with water, and dried to obtain a light yellow solid, 1-methyl-3,4,5-trinitropyrazole (MTNP), with a yield of 60.5%.

[0111] Example 2

[0112] Using 4-chloropyrazole (1) as the raw material, it was nitrated to obtain 4-chloro-3,5-dinitropyrazole (2), and then methylated to obtain 4-chloro-1-methyl-3,5-dinitropyrazole (3); 4-chloro-1-methyl-3,5-dinitropyrazole (3) reacted with p-methoxybenzylamine to obtain 4-methoxybenzylamino-1-methyl-3,5-dinitropyrazole (8), and 1-methyl-3,4,5-trinitropyrazole (MTNP) was obtained through a one-pot oxidation process. The synthetic route is as Figure 7 shown below.

[0113] Synthesis and Characterization of 4-Methoxybenzylamino-1-methyl-3,5-dinitropyrazole (8)

[0114] Dissolve 4-chloro-1-methyl-3,5-dinitropyrazole (3) (0.52 g, 2.52 mmol) in a mixture of 20 mL of petroleum ether and an appropriate amount of water, and add p-methoxybenzylamine (2.07 g, 15.15 mmol), potassium carbonate (0.14 g, 1.01 mmol), and KI (0.042 g, 0.25 mmol). React at 35 °C until the raw materials disappear (monitored by TLC), acidify to pH = 1 with 10% HCl, filter by suction, and wash with water to obtain a bright yellow solid, 4-methoxybenzylamino-1-methyl-3,5-dinitropyrazole (8), with a yield of 86.3% and a melting point of 181.5 - 182.1 °C. IR(KBr, ν / cm -1 ): 3359, 3044, 3015, 2953, 1612, 1583, 1432, 1372; 1 H NMR(400 MHz, DMSO-d 6 , 25 °C) δ: 7.64 (s, 1H), 7.08 (s, 2H), 6.83 (s, 2H), 4.54 (s,2H), 4.12 (s, 3H), 3.69 (s, 3H); 13 C NMR (101 MHz, DMSO-d 6, 25 °C) δ: 159.02 (s), 141.49 (s), 134.28 (s), 130.45 (s), 129.39 (s), 128.97 (s), 114.38 - 114.18 (m), 55.45 (s), 48.42 - 48.22 (m).

[0115] One-Pot Synthesis and Characterization of 1-Methyl-3,4,5-trinitropyrazole (MTNP)

[0116] At room temperature, 4 - methoxybenzylamino - 1 - methyl - 3,5 - dinitropyrazole (8) (0.31 g, 1.00 mmol) was dissolved in 2 mL of concentrated sulfuric acid (98%), and the mixture was stirred for about 30 min. At this time, TLC showed that the raw material reaction was completed. Then, 0.8 mL of 50% H 2 O 2 . The solution was stirred at 0 °C for about 3 h and then transferred to room temperature. As the reaction proceeded, the solution changed from bright yellow to light yellow until the raw material disappeared (monitored by TLC). The reaction solution was poured into crushed ice, filtered, washed with water, and dried to obtain light yellow solid 1 - methyl - 3,4,5 - trinitropyrazole MTNP with a yield of 58.7%.

[0117] Example 3

[0118] Using 4 - chloropyrazole (1) as the raw material, 4 - chloro - 3,5 - dinitropyrazole (2) was obtained by nitration, and 4 - chloro - 1 - methyl - 3,5 - dinitropyrazole (3) was obtained by methylation; 4 - chloro - 1 - methyl - 3,5 - dinitropyrazole (3) reacted with tert - butylamine through an amination reaction to obtain 4 - tert - butylamino - 1 - methyl - 3,5 - dinitropyrazole (9), and 1 - methyl - 3,4,5 - trinitropyrazole MTNP was obtained through a one - pot oxidation process. The synthetic route is as Figure 8 shown.

[0119] Synthesis and Characterization of 4-tert-Butylamino-1-methyl-3,5-dinitropyrazole (9)

[0120] 4 - Chloro - 1 - methyl - 3,5 - dinitropyrazole (3) (0.52 g, 2.52 mmol) was added to a flask, and an excess of tert - butylamine was added. The mixture was heated under reflux conditions, and the solution changed from colorless to orange - yellow. The reaction was monitored by thin - layer chromatography (TLC). After completion of the reaction, it was concentrated under reduced pressure, ultrasonicated with acetonitrile to disperse, and insoluble substances were removed. The filtrate was concentrated under reduced pressure to obtain orange - yellow solid 4 - tert - butylamino - 1 - methyl - 3,5 - dinitropyrazole (9) with a yield of 98.8% and a melting point of 48.2 - 49.7 °C. IR(KBr, ν / cm -1): 3443, 3340, 2967, 2932, 1576, 1523, 1495, 1261, 1441, 1385, 1366, 1322, 1223, 1185, 1322, 1223, 1185, 1127, 1064, 1026, 945, 875, 840, 806, 789, 761, 729, 670; 1 H NMR (400 MHz, DMSO-d 6 , 25 °C) δ: 5.51 (s, 1H), 4.18 (s, 3H), 1.21 (s, 9H); 13 C NMR (101 MHz, DMSO-d 6 , 25 °C) δ: 145.15 (s), 138.04 (s), 125.52 (s), 57.75 (s), 43.41 (s), 29.92 (s).

[0121] One-Pot Synthesis and Characterization of 1-Methyl-3,4,5-trinitropyrazole (MTNP)

[0122] At room temperature, 4-tert-butylamino-1-methyl-3,5-dinitropyrazole (9) (0.24 g, 1.00 mmol) was dissolved in 2 mL of concentrated sulfuric acid (98%), and stirred for about 30 min. At this time, TLC showed that the raw material reaction was completed. Then, 0.8 mL of 50% H 2 O 2 . The solution was stirred at 0 °C for about 3 h and then transferred to room temperature. As the reaction proceeded, the solution changed from bright yellow to light yellow until the raw material disappeared (monitored by TLC). The reaction solution was poured into crushed ice, filtered, washed with water, and dried to obtain light yellow solid 1-methyl-3,4,5-trinitropyrazole MTNP with a yield of 69.5%.

[0123] Example 4

[0124] Using 4-chloropyrazole (1) as the raw material, through nitration and methylation, 4-chloro-1-methyl-3,5-dinitropyrazole (3) was obtained; 4-chloro-1-methyl-3,5-dinitropyrazole (3) reacted with tert-octylamine to obtain N-(2,4,4-trimethyl-2-pentylamine)-1-methyl-3,5-dinitropyrazole (10), and then 1-methyl-3,4,5-trinitropyrazole MTNP was obtained through a one-pot oxidation process. The synthetic route is as Figure 9 shown.

[0125] Synthesis and Characterization of N-(2,4,4-Trimethyl-2-pentylamine)-1-methyl-3,5-dinitropyrazole (10)

[0126] 4-Chloro-1-methyl-3,5-dinitropyrazole (3) (0.52 g, 2.52 mmol) was added to a flask, and an excess of tert-octylamine was added. The reaction was heated at 110 °C and monitored by thin-layer chromatography (TLC) until the reaction was complete. The reaction mixture was concentrated under reduced pressure, sonicated with acetonitrile to disperse it, and the insoluble substances were removed. The filtrate was concentrated under reduced pressure to obtain a bright yellow solid, N-(2,4,4-trimethyl-2-pentylamine)-1-methyl-3,5-dinitropyrazole (10), with a yield of 98.8% and a melting point of 94.6 - 95.2 °C. IR (KBr, ν / cm -1 ): 3452, 3337, 3024, 2967, 1663, 1573, 1525, 1493, 1464, 1441, 1406, 1369, 1350, 1325, 1310, 1250, 1141, 1063, 818, 769; 1 1H NMR (400 MHz, DMSO-d 6 , 25 °C) δ: 5.47 (s, 1H), 4.17 (s, 3H), 1.69 (s, 2H), 1.19 (s, 6H), 1.04 (s, 9H); 13 13C NMR (101 MHz, DMSO-d 6 , 25 °C) δ: 145.35 (s), 138.11 (s), 124.92 (s), 61.60 (s), 54.60 (s), 43.35 (s), 31.75 (s), 29.13 (s).

[0127] One-Pot Synthesis and Characterization of 1-Methyl-3,4,5-trinitropyrazole (MTNP)

[0128] At room temperature, N-(2,4,4-trimethyl-2-pentylamine)-1-methyl-3,5-dinitropyrazole (10) (0.24 g, 1.00 mmol) was dissolved in 2 mL of concentrated sulfuric acid (98%), and the mixture was stirred for about 30 min. At this time, TLC showed that the raw material had reacted completely. Then, 0.8 mL of 50% H 2 2 2 O was slowly added. The solution was stirred at 0 °C for about 3 h and then transferred to room temperature. As the reaction proceeded, the solution changed from bright yellow to light yellow until the raw material disappeared (monitored by TLC). The reaction mixture was poured into crushed ice, filtered, washed with water, and dried to obtain a light yellow solid, 1-methyl-3,4,5-trinitropyrazole MTNP, with a yield of 56.1%.

[0129] Combined with the above embodiments, taking 4-halo-1-methyl-3,5-dinitropyrazole (i.e., compound Ⅳ) as the raw material, 1-methyl-3,4,5-trinitropyrazole MTNP is directly prepared by one-pot oxidation after amination, or the protecting group is first removed by a stepwise method to obtain compound Ⅵ, and then 1-methyl-3,4,5-trinitropyrazole MTNP is prepared by oxidizing compound Ⅵ, which has the characteristics of mild reaction conditions, simple operation, and easy engineering scale-up.

Claims

1. A method for synthesizing 1-methyl-3,4,5-trinitropyrazole, characterized in that: The following steps are involved: Step S1, preparing compound V by reacting compound IV with an amination agent; Step S2, directly oxidizing compound V in one pot to obtain 1-methyl-3,4,5-trinitropyrazole, or removing the protecting group of compound V in a stepwise manner to obtain compound VI, and then oxidizing compound VI to obtain 1-methyl-3,4,5-trinitropyrazole; Among them, the chemical structure of compound IV is: ； Wherein, X is Br, Cl, F; The chemical structure of compound V is: ； Wherein, R is -CH2C6H5, -CH2C6H4OCH3, -C(CH3)3, -C(CH3)2CH2C(CH3)3; The chemical structure of compound VI is: 。 2. The method for synthesizing 1-methyl-3,4,5-trinitropyrazole according to claim 1, characterized in that: In step S1, the preparation process of compound IV is as follows: compound I is first reacted with a nitrating agent to obtain compound III, and then compound III is reacted with a methylating agent to obtain compound III; Among them, the chemical structure of compound I is: ； Wherein, X is Br, Cl, F; The chemical structure of compound III is: ； Wherein, X is Br, Cl, F; Alternatively, in step S1, the preparation process of compound IV is: compound II is reacted with a nitrating agent to obtain the compound; Among them, the chemical structure of compound II is: ； Wherein, X is Br, Cl, or F.

3. The method for synthesizing 1-methyl-3,4,5-trinitropyrazole according to claim 2, characterized in that: In step S1, the nitrating agent is a mixture of concentrated sulfuric acid and fuming nitric acid, and the volume ratio of the two is 2-10:

1.

4. The method for synthesizing 1-methyl-3,4,5-trinitropyrazole according to claim 2 or 3, characterized in that: In the step S1, the methylating agent is dimethyl sulfate, methyl p-toluenesulfonate, methyl trifluoromethanesulfonate, methyl methanesulfonate, dimethyl carbonate, methyl iodide, methyl bromide or methyl chloride, and the molar ratio of compound III to the methylating agent is 1:1-6.

5. The method for synthesizing 1-methyl-3,4,5-trinitropyrazole according to claim 1, characterized in that: In the step S1, the molar ratio of compound IV to the amination reagent is 1:1-20.

6. The method for synthesizing 1-methyl-3,4,5-trinitropyrazole according to claim 1 or 5, characterized in that: In the step S1, when compound IV reacts with the amination reagent, an acetonitrile-water mixture system, a petroleum ether-water mixture system, 1,4-dioxane, methanol, ethanol, N,N-dimethylformamide or an amination reagent is used as a solvent.

7. The method for synthesizing 1-methyl-3,4,5-trinitropyrazole according to claim 6, characterized in that: In the step S1, the reaction temperature is 20-160°C.

8. The method for synthesizing 1-methyl-3,4,5-trinitropyrazole according to claim 1, characterized in that: In the step S2, when 1-methyl-3,4,5-trinitropyrazole is prepared by direct oxidation in one pot, a concentrated sulfuric acid-hydrogen peroxide mixed oxidation system, a trifluoroacetic acid-hydrogen peroxide mixed oxidation system or a potassium peroxymonosulfonate-sulfuric acid-water mixed oxidation system is used; Alternatively, in step S2, the protecting group is first removed by a step-by-step method to prepare compound VI using concentrated sulfuric acid, trifluoroacetic acid, perchloric acid, nitric acid, methanesulfonic acid or trifluoromethanesulfonic acid, and then oxidized to prepare 1-methyl-3,4,5-trinitropyrazole using a concentrated sulfuric acid-hydrogen peroxide mixed oxidation system, a trifluoroacetic acid-hydrogen peroxide mixed oxidation system, a potassium peroxymonosulfonate-sulfuric acid-water mixed oxidation system, an acetic acid-hydrogen peroxide mixed oxidation system, an acetic anhydride-hydrogen peroxide mixed oxidation system, a sodium perborate-acetic acid mixed oxidation system or potassium permanganate.

9. The method for synthesizing 1-methyl-3,4,5-trinitropyrazole according to claim 1 or 8, characterized in that: In step S2, a concentrated sulfuric acid-hydrogen peroxide mixed oxidation system is used to directly oxidize 1-methyl-3,4,5-trinitropyrazole in one pot, the volume ratio of concentrated sulfuric acid to hydrogen peroxide is 2:1, and the mass concentration of hydrogen peroxide is 50%.

10. The method for synthesizing 1-methyl-3,4,5-trinitropyrazole according to claim 1 or 8, characterized in that: In step S2, a concentrated sulfuric acid-hydrogen peroxide mixed oxidation system is used to prepare 1-methyl-3,4,5-trinitropyrazole by stepwise oxidation, wherein the volume ratio of concentrated sulfuric acid to hydrogen peroxide is 2:1, and the mass concentration of hydrogen peroxide is 50%.

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