An Efficient One-Step Reaction for the Preparation of Advanced Fused Bistetrazole-Based Primary Explosives

The first example of [5,6,5]-tricyclic bistetrazole-fused energetic materials has been obtained through a one-step reaction from commercial and inexpensive 4,6-dichloro-5-nitropyrimidine. This one-step reaction including nucleophilic substitution, nucleophilic addition, cyclization, and electron transfer is rarely reported, and the reaction mechanism and scope is well investigated. Among target compounds, organic salts exhibit higher detonation velocities (D: 8898–9077 m s–1) and lower sensitivities (IS: 16–20 J) than traditional high energy explosive RDX (D = 8795 m s–1; IS = 7.5 J). In addition, the potassium salt of 5-azido-10-nitro-bis(tetrazolo)[1,5-c:5′,1′-f]pyrimidin (DTAT-K) possesses excellent priming ability, comparable to traditional primary explosive Pb(N3)2, and ultralow minimum primary charge (MPC = 10 mg), which is the lowest MPC among the reported potassium-based primary explosives. The simple synthesis route, free of heavy metal and expensive raw materials, makes it promising to quickly realize this material in large-scale industrial production as a green primary explosive. This work accelerates the upgrade of green primary explosives and enriches future prospects for the design of energetic materials.


Safety Precaution
Although we experienced no difficulties in handling these energetic materials, small scale and best safety practices (leather gloves, face shield) are strongly encouraged. All chemical reagents, solvents were obtained by purchase and were used as supplied without further purification. 4,6-dichloro-5-nitropyrimidine can be obtained commercially.
The solubility of DTAT-Ag is very poor, so there is no NMR spectrum; Elemental analysis for C 4 HN 12 O 2 Ag (357.00): calcd.

Synthesis of DTAT-K
A solution of 0.45 mmol chloride salt in distilled water (10 mL) was added dropwise to the suspension of DTAT-Ag (0.16 mg, 0.45 mmol) in distilled water (15 mL). The mixture was stirred at 25 °C for 0.5 h, then the precipitate was filtered off and the filtrate was concentrated under reduced pressure to give the desired product.

Theoretical Study
Theoretical calculations were performed by using the Gaussian 09 (Revision E01) suite of programs. 1 The elementary geometric optimization and the frequency analysis were performed at the level of the Becke three parameter, Lee-Yan-Parr (B3LYP) functional with the 6-311+G** basis set. 2 All of the optimized structures were characterized to be local energy minima on the potential surface without any imaginary frequencies. Atomization energies were calculated by the G2. All the optimized structures were characterized to be true local energy minima on the potential-energy surface without imaginary frequencies.
The predictions of heat of formation (HOF) adopt the hybrid DFT-B3LYP methods with 6-311+G** basis set via designed isodesmic reactions. The isodesmic reaction processes, i.e., the number of each kind of formal bond is conserved, are used with application of the bond separation reaction (BSR) rules. The molecule is broken down into a set of two heavyatom molecules containing the same component bonds. The isodesmic reactions used to derive the HOF of the title compounds are in Scheme S1. The change of enthalpy for the reactions at 298 K can be expressed as Where ∑Δ f H P and ∑Δ f H R are the HOF of reactants and products at 298 K, respectively, and ΔH 298 can be calculated using the following expression: Where ΔE 0 is the change in total energy between the products and the reactants at 0 K; ΔZPE is the difference between the zero-point energies (ZPE) of the products and the reactants at 0 K; ΔH T is thermal correction from 0 to 298 K. The Δ(PV) value in eq (2)