Pentaerythritol Trinitrate Substituted s-Tetrazine and s-Triazine

Abstract

The synthesis of pentaerythritol trinitrate persubstituted 1,2,4,5-tetrazine and 1,3,5-triazine is reported. These materials were characterized with respect to their chemical and energetic materials properties. X-ray crystallographic analyses were also performed. The UV/Vis, Raman, and cyclic voltammetry data were collected and are reported.Recently, we described the syntheses of nitrate ester substituted derivatives of chloro-1,2,4,5-tetrazines. 1 These materials were synthesized in order to study their electroactive behavior, and we discovered that these materials formed stable radical anions when subjected to cyclic voltammetry experiments. 2 We also found that the corresponding radical anions could be formed reversibly. We have now focused our efforts on placing nitrate ester containing substituents on both the 3-and 6-position of the 1,2,4,5-tetrazine ring system for the following reasons: 1. to increase the energy content of the resultant product and, 2. to compare the electrochemical behavior of the symmetrical and unsymmetrical tetrazine ring systems.At the same time, we were interested in studying similar systems based upon the 1,3,5-triazine heterocycle. While there are numerous examples of electrochemical studies of metal complexes of 1,3,5-triazine derivatives 3 there are fewer studies of neutral 1,3,5-triazine compounds 4 and no studies of energetic 1,3,5 triazine systems. For this heterocyclic system, we chose to attach nitrate ester substituted moieties at the 2-, 4-, and 6-position.We pursued the use of pentaerythritol trinitrate (PETRIN, 1) 5 as the nitrate ester substituent to attach to the heterocyclic ring systems through nucleophilic substitution through the alcohol functional group. In the case of the 1,2,4,5-tetrazine system, 3,6-dichlorotetrazine (2) was chosen as the electrophile. In our initial studies 1 we found that the reaction of one equivalent each of 1 and 2 in the presence of 2,4,6-collidine led to monosubstitution (3). The addition of two equivalents of 1 under the same reaction conditions did not lead to the desired product 4, but only compound 3, even under forcing conditions. In our prior studies we have observed reduction in reactivity of the remaining chloro substituent when a strongly electron-donating substituent is present. We found that the reaction could be performed in neat 2,4,6-collidine, but the yields were very poor. Ultimately, the reaction was found to proceed in a two-step process by first preparing 3, followed by treatment with an additional equivalent of 1 in the presence of 4-dimethylaminopyridine (DMAP, Scheme 1). 6,7 The reaction can be performed with DMAP in a one-step process from 1 and 2, but the yield is very poor.In our studies of the triazine system, we chose cyanuric chloride (5) as the electrophile. In this case, the use of three equivalents of 1 in the presence of neat 2,4,6-collidine also lead to the desired product 6 in reasonable yield. Interestingly, we found that this reaction could not be performed using DMAP as the base and dichloromethane a...

2,4-Dinitrophenyl and Pentaerythrityltrinitrate as Explosophoric Units in the Synthesis of New Energetic Materials

“…A recent example of the use of PETRIN in a S N Ar reaction to produce EMs in a similar fashion was carried out by a team from Los Alamos National Laboratory and the Naval Research Laboratory. 15 An attempt to produce trinitrodinitrate 17 ( Figure 1) directly by nitration of 16 (HNO 3 / H 2 SO 4 ) resulted in extensive decomposition of the starting material. Likewise, when 1-chloro-2,4,6-trinitro benzene was treated with PETRIN under diverse conditions such as using DMF or acetonitrile in the presence of K 2 CO 3 or under microwave irradiation (K 2 CO 3 , 100 °C, 150 W, 30 min, neat), it was not possible to obtain acceptable yields of 17.…”

“…The use of PETRIN as a reagent for the formation of EMs (as exemplified in this article and elsewhere 15,20 ) serves to illustrate the concept of a 'explosophoric unit' (EU), which may be a useful reference to a particular approach for the synthesis of EMs. By this we mean a synthon composed of two or more explosophoric functions that act as a unit to be attached to a molecular framework or fragment through one or more covalent bonds (the concept would not apply to energetic salts and ionic liquids).…”

“…Procedure B (from reaction of PETRIN (15) with DNFB(1)): 2,4-Dinitrofluorobenzene (1; 1.00 g, 5.37 mmol) was dissolved in dimethylformamide (15 mL). To this stirred solution was then added PETRIN (15;…”

Synthesis and Electrochemical Behavior of Electron‐Rich s‐Tetrazine and Triazolo‐tetrazine Nitrate Esters

“…However, comparable triazine explosives containing nitrate ester groups display irreversible electrochemical behaviour. 5 We sought to understand this difference in behaviour between the tetrazine and triazine systems. To investigate whether the reversible electrochemistry of tetrazine-based energetic materials was an inherent property of these materials, or if the electrochemistry would be disrupted at more negative potentials, we targeted tetrazine-based explosives with both electron-rich amine and nitrate ester groups as model compounds.…”

Photoactive High Explosives: Substituents Effects on Tetrazine Photochemistry and Photophysics

“…Synthesis details for DNP are also in the Supporting Information. The effect of symmetric versus asymmetric substitution was measured using DNAZ–Tz–DNAZ versus DNAZ–Tz–Cl and P–Tz–P versus P–Tz–Cl . The effect of extended conjugation was examined using DNAZ–Tz–azo-Tz–DNAZ versus DNAZ–Tz–DNAZ.…”