1,4,2,5-dioxadiazine bridge-based compounds and methods of synthesis thereof

Abstract

This invention discloses bridging compounds based on 1,4,2,5-dioxadiazine and their synthetic methods. The bridging compounds based on 1,4,2,5-dioxadiazine are BNTD and BNPD, synthesized through the following steps: (1) Chlorooximation reaction: 1H-pyrazole-3-aminooxime is diazotized with an acidic solution of sodium nitrite to obtain 1H-pyrazole-3-chlorooxime; (2) Ring-closing reaction: 1H-1,2,4-triazole-3-chlorooxime and 1H-pyrazole-3-chlorooxime are condensed under the action of an organic base to obtain 3,6-bis(1-nitro-1,2,4-dioxadiazine). (3) Nitration reaction: 3,6-bis(1-nitro-1,2,4-triazol-3-yl)-1,4,2,5-dioxadiazine and 3,6-bis(1H-pyrazole-3-yl)-1,4,2,5-dioxadiazine were nitrated in the presence of nitric acid to obtain BNTD and BNPD, respectively. The compounds BNTD and BNPD of the present invention have good stability.

Description

Technical Field

[0001] This invention belongs to the field of energetic materials and relates to a 1,4,2,5-dioxadiazine bridging compound and its synthesis method. Background Technology

[0002] Energetic materials are the power source and damage source for weapons to strike targets, and their energy level directly affects the performance of weapon systems. While increasing the energy of energetic materials, their sensitivity often increases and their thermal stability decreases. Many environmental pollution and safety accidents have also occurred during the transportation, storage, and use of energetic materials. Developing energetic compounds that simultaneously possess high energy, low sensitivity, and good thermal stability has always been a research hotspot in the field of energetic materials, and it is fraught with challenges. To improve the oxygen balance of energetic materials, various oxygen-rich nitrogen heterocycles are often introduced into the structure of energetic compounds, including furans, 1,2,4-oxadiazoles, and 1,3,4-oxadiazoles. The 1,4,2,5-dioxadiazine ring has the highest oxygen content (37.2%) among nitrogen heterocycles. However, due to the complex synthetic process, the 1,4,2,5-dioxadiazine ring is rarely introduced into high-energy molecules.

[0003] Existing energetic compounds based on 1,4,2,5-dioxadiazine bridges all have defects. For example, compound 3,6-bis(4-nitro-1,2,5-oxadiazol-3-yl)-1,4,2,5-dioxadiazine (i, Yu Q, Cheng G, Ju X, et al. An interesting 1,4,2,5-dioxadiazine-furazan system: structural modification by incorporating versatile functionalities[J]. Dalton Trans, 2017, 46(41): 14301-14309.) and compound 3,6-bis(4-nitro-1,2,5-oxadiazol-3-yl)-1,4,2,5-dioxadiazine (ii, Leonard P, Pollard C, Chavez D, et al. 3,6-Bis(4-nitro-1,2,5-oxadiazol-3-yl)-1,4,2,5-dioxadiazene(BNDD): A Powerful Sensitive Explosive[J].Synlett,2011,2011(14):2097-2099.) has high detonation performance (i:D v =9109m·s -1 ;ii:D v =9040m·s -1 However, its thermal stability and sensitivity are poor (i:T).d =106℃, IS=4.5J, FS=100N; ii: T d =148℃, IS=2.2J; FS=116N). Their poor thermal stability and low sensitivity cannot meet the needs of practical applications. Summary of the Invention

[0004] To improve the stability of energetic compounds based on 1,4,2,5-dioxadiazine bridges, construct compound structures with triazole or pyrazole rings based on 1,4,2,5-dioxadiazine bridges, and provide important intermediates for energetic compounds based on this framework, this invention provides two 1,4,2,5-dioxadiazine bridge-based compounds and their synthetic methods.

[0005] The 1,4,2,5-dioxadiazine-based bridging compound described in this invention is 3,6-bis(1-nitro-1,2,4-triazol-3-yl)-1,4,2,5-dioxadiazine (BNTD), with the following structural formula: Or 3,6-bis(1-nitro-1H-pyrazole-3-yl)-1,4,2,5-dioxadiazine (BNPD), with the following structural formula:

[0006] The synthetic route of the 1,4,2,5-dioxadiazine bridging compound described in this invention is as follows:

[0007]

[0008] or

[0009]

[0010] Specifically, the following steps are included:

[0011] (1) Synthesis of 1H-pyrazole-3-chlorooxime (4): 1H-pyrazole-3-aminooxime (3) was diazotized in an acidic solution of sodium nitrite to generate 1H-pyrazole-3-chlorooxime (4);

[0012] (2) Synthesis of 3,6-bis(1,2,4-triazol-3-yl)-1,4,2,5-dioxadiazine (2) or 3,6-bis(1H-pyrazole-3-yl)-1,4,2,5-dioxadiazine (5): Compound 1H-1,2,4-triazol-3-chlorooxime (1) or 1H-pyrazole-3-chlorooxime (4) is condensed in the presence of an organic base to generate 3,6-bis(1,2,4-triazol-3-yl)-1,4,2,5-dioxadiazine (2) or 3,6-bis(1H-pyrazole-3-yl)-1,4,2,5-dioxadiazine (5), wherein the organic base is one or both of triethylamine and pyridine;

[0013] (3) Synthesis of 3,6-bis(1-nitro-1,2,4-triazol-3-yl)-1,4,2,5-dioxadiazine (BNTD) or 3,6-bis(1-nitro-1H-pyrazol-3-yl)-1,4,2,5-dioxadiazine (BNPD): The compound 3,6-bis(1,2,4-triazol-3-yl)-1,4,2,5-dioxadiazine (BNTD) 2) or 3,6-bis(1H-pyrazol-3-yl)-1,4,2,5-dioxadiazine (5) is nitrated in the presence of nitric acid to 3,6-bis(1-nitro-1,2,4-triazol-3-yl)-1,4,2,5-dioxadiazine (BNTD) or 3,6-bis(1-nitro-1H-pyrazol-3-yl)-1,4,2,5-dioxadiazine (BNPD).

[0014] Preferably, in step (1), the molar ratio of compound 1H-pyrazole-3-aminooxime (3) to sodium nitrite is 1:1 to 1:5; the molar ratio of sodium nitrite to acid is 1:1 to 1:10; the reaction temperature is 20 to 50°C; the solvent is water, anhydrous ethanol or methanol; and the acidic solution of sodium nitrite is an aqueous solution of sodium nitrite in hydrochloric acid or an aqueous solution of sodium nitrite in sulfuric acid.

[0015] More preferably, step (1) specifically involves dissolving compound 1H-pyrazole-3-aminooxime (3) in hydrochloric acid aqueous solution or sulfuric acid aqueous solution, cooling it to 5°C in an ice bath, then slowly adding a saturated aqueous solution of sodium nitrite, reacting in an ice bath for a period of time, stirring overnight at room temperature, and filtering to obtain compound 1H-pyrazole-3-chlorooxime (4).

[0016] Preferably, in step (2), the molar ratio of compound 1H-1,2,4-triazol-3-chlorooxime (1) or 1H-pyrazole-3-chlorooxime (4) to the organic base is 1:1 to 1:10; the reaction temperature is 20 to 60°C; and the solvent is ethanol, methanol or acetonitrile.

[0017] More preferably, step (2) specifically involves suspending compound 1H-1,2,4-triazol-3-chlorooxime (1) or 1H-pyrazole-3-chlorooxime (4) in a solvent, controlling the temperature at 0-3°C, then adding one or both of pyridine and triethylamine, stirring at 0-3°C until the mixture is homogeneous, stirring at room temperature for one day, then stirring at 50°C for 3-4 hours and stopping, letting it stand overnight, and evaporating the solvent to obtain compound 3,6-bis(1,2,4-triazol-3-yl)-1,4,2,5-dioxadiazine (2) or 3,6-bis(1H-pyrazole-3-yl)-1,4,2,5-dioxadiazine (5).

[0018] Preferably, in step (3), the molar ratio of compound 3,6-bis(1,2,4-triazol-3-yl)-1,4,2,5-dioxadiazine (2) or 3,6-bis(1H-pyrazol-3-yl)-1,4,2,5-dioxadiazine (5) to nitric acid is 1:1 to 1:10; the reaction temperature is -10 to 30°C; the solvent is acetic anhydride; and the nitrating agent is fuming nitric acid or 100% nitric acid.

[0019] More preferably, step (3) specifically involves dissolving compound 3,6-bis(1,2,4-triazol-3-yl)-1,4,2,5-dioxadiazine (2) or 3,6-bis(1H-pyrazole-3-yl)-1,4,2,5-dioxadiazine (5) in acetic acid, controlling the temperature in an ice bath, then adding a mixture of fuming nitric acid and acetic anhydride, reacting for a period of time in an ice bath, then stirring overnight at room temperature, quenching with ice water after the reaction, and filtering to obtain compound 3,6-bis(1-nitro-1,2,4-triazol-3-yl)-1,4,2,5-dioxadiazine (BNTD) or 3,6-bis(1-nitro-1H-pyrazole-3-yl)-1,4,2,5-dioxadiazine (BNPD).

[0020] Compared with the prior art, the present invention has the following advantages:

[0021] 1. Energetic compound BNTD(T d =163℃) and BNPD(T d =194℃) compared to compound 3,6-bis(4-nitammono-1,2,5-oxadiazol-3-yl)1,4,2,5-dioxadiazine (i; T d =106℃) and 3,6-bis(4-nitro-1,2,5-oxadiazol-3-yl)-1,4,2,5-dioxadiazine (ii; T d =148℃) has a high thermal decomposition temperature;

[0022] 2. Energetic compounds BNTD (IS = 15 J, FS = 288 N) and BNPD (IS = 20 J, FS = 216 N) exhibit better mechanical insensitivity than compounds 3,6-bis(4-nitro-1,2,5-oxadiazol-3-yl)-1,4,2,5-dioxadiazine (i; IS = 4.5 J, FS = 100 N) and 3,6-bis(4-nitro-1,2,5-oxadiazol-3-yl)-1,4,2,5-dioxadiazine (ii; IS = 2.2 J; FS = 116 N). Attached Figure Description

[0023] Figure 1 The single-crystal structure diagram of 3,6-bis(1-nitro-1,2,4-triazol-3-yl)-1,4,2,5-dioxadiazine (BNTD).

[0024] Figure 2 The single crystal structure diagram of 3,6-bis(1-nitro-1H-pyrazole-3-yl)-1,4,2,5-dioxadiazine (BNPD). Detailed Implementation

[0025] To make the objectives, technical solutions, and advantages of this invention clearer, the technical solutions of this invention will be described in detail below. Obviously, the described embodiments are merely some embodiments of this invention, and not all embodiments. Based on the embodiments of this invention, all other implementation methods obtained by those skilled in the art without creative effort are within the scope of protection of this invention.

[0026] Example 1

[0027] Compound 1H-1,2,4-triazol-3-chlorooxime (1, white solid, 1.24 g, 8.4 mmol) was suspended in ethanol (70 mL) at a controlled temperature of 0–3 °C. Then, pyridine (5 mL, 7 eq) and triethylamine (9 mL, 7 eq) were added. After the addition was complete, the mixture was stirred at 0–3 °C for a period of time. It was then stirred at room temperature for one day. Finally, it was stirred at 50 °C for 3–4 h, then stopped, and allowed to stand overnight. After evaporating the solvent, compound 3,6-bis(1,2,4-triazol-3-yl)-1,4,2,5-dioxadiazine (2, pale yellow solid, 0.49 g, yield 53%) was obtained.

[0028] 1 H NMR (500MHz, DMSO-d6): δ = 13.65 (s, 1H), 8.86 (s, 1H) ppm. 13 C NMR (125MHz, DMSO-d6): δ = 156.68, 148.72, 145.75ppm. IR (KBr): ν = 3438, 3191, 1682, 1661, 1502, 1474, 1340, 1337, 1253, 945cm -1 .Elemental analysis calcd(%)for C6H4N8O2(220):C 32.73,H1.83,N 50.90; found:C 32.71,H 1.92,N 50.87.

[0029] Compound 3,6-bis(1,2,4-triazol-3-yl)-1,4,2,5-dioxadiazine (2, pale yellow solid, 1.63 g, 7.4 mmol) was dissolved in acetic acid (10 mL) under ice bath temperature control. Then, a mixture of fuming nitric acid (1.8 mL) and acetic anhydride (5.4 mL) was added. The reaction was carried out at low temperature for a period of time, followed by stirring overnight at room temperature. After the reaction was completed, the mixture was quenched with ice water and filtered to give compound 3,6-bis(1-nitro-1,2,4-triazol-3-yl)-1,4,2,5-dioxadiazine (BNTD, white solid, 0.55 g, 24% yield).

[0030] 1 H NMR (500MHz, DMSO-d6): δ = 10.05 (s) ppm. 13 C NMR (125MHz, DMSO-d6): δ = 156.50, 147.15, 143.00ppm. IR (KBr): ν = 3196, 1824, 1821, 1653, 1319, 1315, 1223, 1122, 1043, 937cm -1 .Elemental analysis calcd(%)for C6H2N 10 O6(310):C 23.24,H 0.65,N45.16; found:C 23.19,H 0.82,N 45.11.

[0031] Example 2

[0032] Compound 1H-pyrazole-3-aminooxime (3, white solid, 1.70 g, 13.5 mmol) was dissolved in an aqueous hydrochloric acid solution (10%, 17.3 mL). The solution was cooled to 5°C in an ice bath, and then a saturated aqueous solution of sodium nitrite (1.40 g, 20.2 mmol) was slowly added. After reacting in an ice bath for a period of time, the mixture was stirred overnight at room temperature. The mixture was then filtered to give compound 1H-pyrazole-3-chlorooxime (4, white solid, 1.75 g, 89% yield).

[0033] 1 H NMR (500MHz, DMSO-d6): δ = 12.20 (s, 1H), 9.83 (s, 1H), 7.78 (s, 1H), 6.56 (s, 1H) ppm. 13 C NMR (125MHz, DMSO-d6): δ = 144.16, 131.55, 104.09ppm. IR (KBr): ν = 3483, 3451, 3215, 3176, 1674, 1258, 424cm -1.Elemental analysis calcd(%)for C4H4N3OCl(146):C33.01,H 2.77,N 28.87; found:C 33.00,H 2.79,N 28.85.

[0034] Compound 1H-pyrazole-3-chlorooxime (4, 1.22 g, 8.4 mmol) was suspended in ethanol (70 mL) at 0–3 °C. Pyridine (5 mL, 7 eq) and triethylamine (9 mL, 7 eq) were then added. After the addition was complete, the mixture was stirred at 0–3 °C for a period of time. The mixture was then stirred at room temperature for one day. Finally, the reaction was carried out overnight at 50 °C. Filtration yielded compound 3,6-bis(1H-pyrazole-3-yl)-1,4,2,5-dioxadiazine (5, white solid, 0.42 g, 46% yield).

[0035] 1 H NMR (500MHz, DMSO-d6): δ = 13.76 (s, 1H), 7.99 (s, 1H), 6.81 (s, 1H) ppm. 13 C NMR (125MHz, DMSO-d6): δ = 156.32, 132.51, 131.76, 104.81ppm. IR (KBr): ν = 3448, 3217, 3178, 1674, 1521, 1464, 1452, 1175, 1122, 945.1cm -1 .Elemental analysis calcd(%)forC8H6N6O2(218):C 44.04,H 2.77,N 38.52; found:C 44.02,H 2.81,N 38.52.

[0036] Compound 3,6-bis(1H-pyrazol-3-yl)-1,4,2,5-dioxadiazine (5, 1.62 g, 7.4 mmol) was suspended in acetic acid (10 mL) and the temperature was controlled in an ice bath. Then, a mixture of fuming nitric acid (1.8 mL) and acetic anhydride (5.4 mL) was added. The reaction was carried out at low temperature for a period of time, followed by stirring overnight at room temperature to give compound 3,6-bis(1-nitro-1H-pyrazol-3-yl)-1,4,2,5-dioxadiazine (BNPD, white solid, 0.82 g, 36% yield).

[0037] 1 H NMR (500MHz, DMSO-d6): δ = 9.05 (s, 1H), 7.20 (s, 1H) ppm. 13C NMR (125MHz, DMSO-d6): δ = 156.75, 138.12, 129.28, 109.39ppm. IR (KBr): ν = 3190, 1797, 1467, 1301, 1249, 1135, 1118, 946, 774cm -1 .Elemental analysis calcd(%)for C8H4N8O6(308):C31.18,H 1.31,N 36.36; found:C 31.12,H 1.35,N 36.31.

[0038] Comparative Example 1

[0039] This comparative example is essentially the same as Example 1, except that pyridine and triethylamine are replaced with the inorganic base sodium carbonate. Under these conditions, the target product cannot be synthesized.

[0040] Comparative Example 2

[0041] This comparative example is essentially the same as Example 2, except that pyridine and triethylamine are replaced with the inorganic base sodium carbonate. Under these conditions, the target product cannot be synthesized.

[0042] Comparative Example 3

[0043] This comparative example is essentially the same as Example 1, except that pyridine and triethylamine are replaced with the organic base aniline. Under these conditions, the target product cannot be synthesized.

[0044] Comparative Example 4

[0045] This comparative example is essentially the same as Example 2, except that pyridine and triethylamine are replaced with the organic base aniline. Under these conditions, the target product cannot be synthesized.

Claims

1. A bridging compound based on 1,4,2,5-dioxadiazine, characterized in that, It is 3,6-bis(1-nitro-1,2,4-triazol-3-yl)-1,4,2,5-dioxadiazine, with the structural formula as follows: ; or 3,6-bis(1-nitro-1 H -pyrazol-3-yl)-1,4,2,5-dioxadiazine, with the following structural formula: .

2. The method for synthesizing compounds based on 1,4,2,5-dioxadiazine bridging compounds according to claim 1, characterized in that, The synthesis route is as follows: ； or ; Specifically, the following steps are included: (1) 1 H Synthesis of pyrazole-3-chlorooxime: Compound 1 H -Pyrazole-3-aminooxime reacts in an aqueous solution of sodium nitrite in hydrochloric acid to produce 1 H -Pyrazole-3-chlorooxime; (2) 3,6-bis(1,2,4-triazol-3-yl)-1,4,2,5-dioxadiazine or 3,6-bis(1 H Synthesis of pyrazol-3-yl)-1,4,2,5-dioxadiazine: Compound 1 H -1,2,4-triazol-3-chlorooxime or 1 H 3-Pyrazole-3-chlorooxime condenses with an organic base to form 3,6-bis(1,2,4-triazol-3-yl)-1,4,2,5-dioxadiazine or 3,6-bis(1-chlorooxime). H -pyrazol-3-yl)-1,4,2,5-dioxadiazine, wherein the organic base is one or both of triethylamine and pyridine; (3) 3,6-bis(1-nitro-1,2,4-triazol-3-yl)-1,4,2,5-dioxadiazine or 3,6-bis(1-nitro-1 H Synthesis of 3,6-bis(1,2,4-triazol-3-yl)-1,4,2,5-dioxadiazine: The compound 3,6-bis(1,2,4-triazol-3-yl)-1,4,2,5-dioxadiazine or 3,6-bis(1 H -pyrazol-3-yl)-1,4,2,5-dioxadiazine is nitrated in the presence of nitric acid to 3,6-bis(1-nitro-1,2,4-triazol-3-yl)-1,4,2,5-dioxadiazine or 3,6-bis(1-nitro-1 H (-pyrazole-3-yl)-1,4,2,5-dioxadiazine.

3. The synthesis method according to claim 2, characterized in that, In step (1), compound 1 H The molar ratio of pyrazole-3-aminooxime to sodium nitrite is 1:1 to 1:5; the molar ratio of sodium nitrite to hydrochloric acid is 1:1 to 1:10; the reaction temperature is 20 to 50°C; and the solvent is water, anhydrous ethanol, or methanol.

4. The synthesis method according to claim 3, characterized in that, Step (1) specifically involves: Compound 1 H 3-Pyrazole-3-aminooxime was dissolved in hydrochloric acid aqueous solution, cooled to 5 °C in an ice bath, and then a saturated aqueous solution of sodium nitrite was slowly added. After reacting in an ice bath for a period of time, the mixture was stirred overnight at room temperature, and filtered to obtain compound 1. H -Pyrazole-3-chlorooxime.

5. The synthesis method according to claim 2, characterized in that, In step (2), compound 1 H -1,2,4-triazol-3-chlorooxime or 1 H The molar ratio of pyrazole-3-chlorooxime to an organic base is 1:1 to 1:10; the reaction temperature is 20 to 60°C; and the solvent is ethanol, methanol, or acetonitrile.

6. The synthesis method according to claim 2, characterized in that, Step (2) specifically involves: adding compound 1 H -1,2,4-triazol-3-chlorooxime or 1 H Pyrazole-3-chlorooxime was suspended in a solvent and the temperature was controlled at 0–3 °C. Then, one or both of pyridine and triethylamine were added. After the addition was complete, the mixture was stirred at 0–3 °C until homogeneous. The mixture was then stirred at room temperature for one day, followed by stirring at 50 °C for 3–4 h. The mixture was then allowed to stand overnight, and the solvent was evaporated to obtain compound 3,6-bis(1,2,4-triazol-3-yl)-1,4,2,5-dioxadiazine or 3,6-bis(1… H (-pyrazole-3-yl)-1,4,2,5-dioxadiazine.

7. The synthesis method according to claim 2, characterized in that, In step (3), the compound 3,6-bis(1,2,4-triazol-3-yl)-1,4,2,5-dioxadiazine or 3,6-bis(1 H The molar ratio of pyrazol-3-yl)-1,4,2,5-dioxadiazine to nitric acid is 1:1 to 1:10; the reaction temperature is -10 to 30 °C; the solvent is acetic anhydride; and the nitrating agent is fuming nitric acid or 100% nitric acid.

8. The synthesis method according to claim 7, characterized in that, Step (3) specifically involves: mixing compound 3,6-bis(1,2,4-triazol-3-yl)-1,4,2,5-dioxadiazine or 3,6-bis(1 H 3,6-bis(1-nitro-1,2,4-triazol-3-yl)-1,4,2,5-dioxadiazine was dissolved in acetic acid and the mixture was kept at an ice bath temperature. Then, a mixture of fuming nitric acid and acetic anhydride was added, and the reaction was continued at an ice bath for a period of time. Afterward, the mixture was stirred overnight at room temperature. The reaction was then quenched with ice water, and the mixture was filtered to give compound 3,6-bis(1-nitro-1,2,4-triazol-3-yl)-1,4,2,5-dioxadiazine or 3,6-bis(1-nitro-1 H (-pyrazole-3-yl)-1,4,2,5-dioxadiazine.

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