In the last decades, the furazan fused ring compounds have attracted more attention owing to their high density, high specific volume and high nitrogen content^[1-5]. A novel energetic compound based on furazan and piperazine fused ring, 6-dinitroethylene-4, 5, 8-trinitro-5, 6, 7, 8-tetrahydro-4H-imidazo [4, 5-e] furazano[3, 4-b]piperazine (PNEIFP), was firstly designed and its physico-chemical performances were calculatedby Gaussian 09 program^[6] and VLW method^[7](density 2.02 g·cm^-3, enthalpy of formation +724.1 kJ·mol^-1(298 K) and detonation velocity 9681.0 m·s^-1). Using glyoxal and 1, 1-diamino-2, 2-dinitroethylene(FOX-7) as starting materials, PNEIFP was synthesized for the first time via the reactions of two cyclizations and nitration with a total yield of 5.2% (Scheme 1), PNEIFP and its intermediates were characterized by NMR, IR, MS and EA etc. However, it is found that PNEIFP shows a bad stability, easily decomposes at room temperature.

Scheme 1(Scheme1)

Scheme1 Synthetic route of PNEIFP

Glyoxal (40% in water, 7.5 g, 0.05 mol), 10 mL water were mixed and stirred at room temperature. To this mixture, Na₂CO₃ (0.15 g, 1.4 mmol) was added, and then FOX-7 (7.4 g, 0.05 mol) was added in batches after Na₂CO₃ dissolved, the mixture was stirred for another 4 h. The yellow precipitate was filtered to obtain 8.3 g solid with a yield of 80.6% and a purity of 99.0% (HPLC). IR(KBr, ν/cm^-1): 3483, 3429(—OH), 3307(—NH), 1602(—C＝N), 1562, 1352(—NO₂), 1048(—C—O); ¹H NMR (DMSO-d₆, 500 MHz), δ: 4.978 (s, 2H, OH), 6.729(s, 2H, CH), 9.660(s, 2H, NH); ¹³C NMR (DMSO-d₆, 500 MHz), δ: 85.95 (CH), 129.27(C(NO₂)₂), 152.92(C＝C); Anal.calcd for C₄H₆O₆N₄:C 23.31, H 2.93, N 27.18; found C 22.79, H 2.91, N 26.91.

1 (2.06 g, 0.01 mol), 10 mL distilled water were transferred into a three-necked round-bottomed flask with a mechanical stirrer, then 37% hydrochloric acid (7 mL, 0.08 mol) was added dropwise. After being warmed to 70 ℃ and 1 dissolved completely, 3, 4-diaminofurazan (1.0 g, 0.01 mol) was added in batches and the mixture was stirred for another 2 h at this temperature. The solution was cooled to 10 ℃, then, the deep red precipitate was filtered to obtain 1.0 g solid with a yield of 37.0% and a purity of 98.5% (HPLC). IR (KBr, ν/cm^-1): 3323 (—NH), 1543, 1320(—NO₂), 1615, 1520, 1098 (furazan); ¹H NMR(DMSO-d₆, 500 Hz)δ: 5.631(2H, s, CH), 7.738(2H, s, NH-piperazine), 9.489(2H, s, NH-imidazolidin); ¹³C NMR (DMSO-d₆, 125 Hz) δ: 64.578 (CH), 129.306 (C(NO₂)₂), 145.645 (C-furazan), 152.356(C＝C); Anal.calcd for C₆H₆O₅N₈: C 26.67, H 2.22, N 41.48;found C 26.68, H 2.52, N 40.26.

2 (0.38 g, 1.4 mmol) and 5 mL 100% nitric acid were added in a three-necked round-bottomed flask with a stirrer. The reaction mixture was cooled to -5 ℃, and then acetic anhydride was added dropwise. After acetic anhydride was added completely, it was stirred for another 5 h at 0~5℃. The final mixture was put into ice water, and then the yellow precipitate was filtered to obtain 0.1 g solid with a yield of 17.5% and purity of 98.7%. IR (KBr, ν/cm^-1) : 3381(—NH), 1619, 1384(—NO₂), 1756, 1471, 1033(furazan); ¹H NMR(Acetone, 500 Hz)δ: 6.868 (s, CH), 8.375 (s, CH), 9.593(s, NH-imidazolidin); ¹³C NMR(DMSO-d₆, 125 Hz)δ: 64.763(CH), 70.572(CH), 140.959(C(NO₂)₂), 142.844 (2C, C-furazan), 148.256 (C＝C); Anal. calcd for C₆H₃O₁₁N₁₁: C 17.86, H 0.741, N 38.02;found C 17.78, H 1.28, N 34.48.

Physico-chemical properties, such as density and enthalpy of formation were calculated by Gaussian 09 program^[6], its detonation velocity and detonation pressure were calculated by VLW method^[7]. The data of performances for PNEIFP were showed in the Table 1.

表 1(Tab. 1)

Tab. 1 Performances of PNEIFP properties appearance dissolubility decomposition temperature/℃ density/g·cm-3 detonation velocity/m·s-1 detonation pressure/GPa enthalpy of formation/kJ·mol-1 explosion heat/J·g-1 results yellow solid soluble in acetone and DMSO 20 2.02 9681.0 44.45 724.10 7303.0 condition Eyeballing(tested) experimental method(tested) TLC analysis(tested) Gaussian 09 program(caculated) VLW method(caculated) VLW method(caculated) Gaussian 09 program(caculated) K-J formula(caculated) Note: DMSO is dimethyl sulfoxide.

Tab.1 Performances of PNEIFP

A new furazan fused ring energetic compound, 6-dinitroethylene-4, 5, 8-trinitro -5, 6, 7, 8-tetrahydro -4H-imidazo [4, 5-e] furazano [3, 4-b]piperazine (PNEIFP), was synthesized for the first. In addition, some properties of PNEIFP were obtained by calculation or test. The calculated results show that the density, enthalpy of formation, detonation velocity, and detonation pressure of PNEIFP are 2.02 g·cm^-3, 724.1 kJ·mol^-1, 9681.0 m·s^-1 and 44.45 GPa, respectively. The above fact showed that PNEIFP exhibits good explosive performance. It is a pity that PNEIFP easily decomposes at room temperature.