Furazan Ring Research Articles

Structure-activity relationships of furazano[3,4-b]pyrazines as mitochondrial uncouplers.

Chemical mitochondrial uncouplers are lipophilic weak acids that transport protons into the mitochondrial matrix via a pathway that is independent of ATP synthase, thereby uncoupling nutrient oxidation from ATP production. These uncouplers have potential for the treatment of diseases such as obesity, Parkinson's disease, and aging. We have previously identified a novel mitochondrial protonophore, named BAM15, which stimulates mitochondrial respiration across a broad dosing range compared to carbonyl cyanide p-trifluoromethoxyphenylhydrazone (FCCP). Herein, we report our investigations on the structure-activity relationship profile of BAM15. Our studies demonstrate the importance of the furazan, pyrazine, and aniline rings as well as pKa in maintaining its effective protonophore activity.

A facile synthesis and microtubule-destabilizing properties of 4-(1H-benzo[d]imidazol-2-yl)-furazan-3-amines

A series of 4-(1H-benzo[d]imidazol-2-yl)-furazan-3-amines (BIFAs) were prepared in good yields (60–90% for each reaction step) via a novel procedure from aminofurazanyl hydroximoyl chlorides and o-diaminobenzenes. The synthetic sequence was run under mild reaction conditions, it was robust and did not require extensive purification of intermediates or final products. Furthermore, there was no need for protection of reactive moieties allowing for the parallel synthesis of diverse BIFA derivatives. Subsequent biological evaluation of the resulting compounds revealed their anti-proliferative effects in the sea urchin embryo model and in cultured human cancer cell lines. The most active compounds showed 0.2–2 μM activities in both assay systems. The unsubstituted benzene ring of the benzoimidazole template as well as the unsubstituted amino group in the furazan ring were essential prerequisites for the antimitotic activity of BIFAs. Compound 57 bearing the 2-chlorophenyl acetamide substituent at the nitrogen atom of the imidazole ring was the most active molecule in the examined set.

Novel Energetic Compounds Based on 5-Methyl-1-Aminotetrazole

Two energetic compounds based on 5-methyl-1-aminotetrazole were prepared. The trinitroethyl moiety and furazan ring were introduced to tetrazole, respectively. The trinitroethyl moiety can increase the oxygen balance, and the furazan ring can improve the detonation properties. The structures of both compounds were confirmed by X-ray crystallography. Their thermal stability and explosive performance were also investigated.

Improved method for prediction of density of energetic compounds using their molecular structure

Accurate prediction of detonation pressure and velocity of an energetic compound through computer codes and empirical methods requires reliable value of its crystal density. This paper introduces a reliable method to estimate crystal density of a wide range of different types of energetic compounds. This method can applied for any energetic compounds containing at least –NO2, –NNO2, –ONO2, and furazan ring. It is based on some specific molecular fragments of energetic compounds. For 172 different energetic compounds, the root mean squares (rms) percent errors of the new correlation and one of the best available new group additivity methods are 2.16 and 11.0, respectively. The present method also provides more reliable predictions for new explosives such as N,N′-bis(1,2,4-triazol-3-yl)-4,4′-diamino-2,2′,3,3′,5,5′,6,6′-octanitroazobenzene and 2,4,6-tris(3′,5′-diamino-2′,4′,6′-trinitrophenylamino)-1,3,5-triazine.

Theoretical studies on energetic materials bearing pentaflurosulphyl (SF 5 ) groups

Heats of formation (HOF) for a series of energetic materials containing SF5 group were studied by density functional theory. Results show that HOFs increase with the augmention of field effects of substituted groups. Addition of furazan or furoxan ring increases HOF of the energetic materials. All the SF5-containing compounds have densities which are ∼0.19 g/cm3 higher than those containing –NH2 group. S–F bond is the trigger bond for the thermolysis process in the title compounds and bond dissociation energies of the weakest bonds range from 351.1 to 388.3 kJ/mol. Detonation velocities (D) and pressures (P) are evaluated by Kamlet–Jacobs equations with the calculated densities and HOFs. Results show that increasing the amount of furazan rings results in a larger D and P. Considering the detonation performance and thermal stability, eight compounds may be considered as potential candidates for high-energy density materials. SF5 group is an important energetic group. Considering the importance of the SF5 group, a series of energetic materials containing SF5 group were investigated to discuss the HOF, BDE and detonation properties in order to search for compounds with better performance.

ChemInform Abstract: Synthesis of [1,2,4]Triazolo[4,3‐b]‐s‐tetrazines with Incorporated Furazan Ring.

AbstractFurazancarboxylic hydrazines (II) can serve as nucleophiles to substitute one pyrazole fragment in bis‐pyrazolyl‐tetrazines (I).

ChemInform Abstract: 4‐R‐7‐Nitrobenzofurazans in [3 + 2] Cycloaddition Reactions with N‐Methylazomethine Ylide.

AbstractA number of novel tetrahydroisoindole derivatives (IV) fused with a furazan ring are stereoselectively synthesized based on the 1,3‐dipolar cycloaddition of in situ generated N‐methylazomethine ylide with substituted 4‐nitrobenzofurazans.

ChemInform Abstract: Synthesis of 3‐Nitramino‐4‐(1H‐1,2,3‐triazol‐1‐yl)‐1,2,5‐oxadiazoles and Their Salts.

AbstractTriazolylfurazans bearing a primary nitramino group attached to the furazan ring, e.g. (II), are prepared for the first time.

Energetic materials containing fluorine. Design, synthesis and testing of furazan-containing energetic materials bearing a pentafluorosulfanyl group

The advantageous impact of a pentafluorosulfanyl substituent on the properties of furazan-containing energetic materials was demonstrated by the synthesis and study of the energetic properties of ten new compounds. The thermal stability of these compounds was evaluated by DSC and TGA, whereas densities, heats of formation, pressures of detonation and speeds of detonation were obtained computationally. On the basis of these data, it was concluded that the combination of the SF5 substituent with the furazan ring led to materials of higher density and predicted detonation properties than other known furazans or SF5-containing materials. In addition, the synthetic studies provided insight regarding the electron-withdrawing nature of the furazan ring, in particular its effect on the basicity and nucleophilic reactivity of amino furazans.

4-R-7-Nitrobenzofurazans in [3+2] cycloaddition reactions with N-methylazomethine ylide

A number of new tetrahydroisoindole derivatives fused with the furazan ring were synthesized based on the 1,3-dipolar cycloaddition of N-methylazomethine ylide with substituted 4-nitrobenzofurazans. Substituents in the benzene ring were found to affect the cycloaddition process.

Synthesis of [1,2,4]triazolo[4,3-b]-s-tetrazines with incorporated furazan ring

Furazancarboxylic hydrazides can serve as nucleophiles to substitute for one dimethylpyrazole fragment in bis(3,5-dimethylpyrazol-1-yl)-s-tetrazine, giving the corresponding N′-[6-(3,5-dimethylpyrazol-1-yl)-s-tetrazin-3-yl]-4-R-furazan-3-carbohydrazides in good yields. Dehydration of the indicated carbohydrazides in polyphosphoric acid for the first time gave rise to [1,2,4]triazolo[4,3-b]-s-tetrazines containing the furazan ring as a substituent at the triazole ring.

Assemblies of energetic 3,3′-diamino-4,4′-azofurazan on single-walled carbon nanotubes

The structure, adsorption energy, and initial dissociation reaction of the energetic 3,3′-diamino-4,4′-azofurazan (DAAzF) assembled inside or outside single-walled carbon nanotubes (i.e. CNT(6,6), CNT(8,8), and CNT(10,10)) were calculated by using an ONIOM approach. It was found that the geometrical changes in the furazan rings were obvious for the DAAZF assembled into CNT(6,6) with respect to that of the isolated DAAzF. As for the other assemblies, the DAAzF showed very similar geometrical parameters of the furazan rings as the isolated DAAzF. Only the furazan rings rotated slightly. It was also found that the DAAZF@CNT(6,6) had a positive adsorption energy. However, the DAAZF/CNT(6,6), DAAZF/CNT(8,8), DAAZF/CNT(10,10), DAAZF@CNT(8,8), DAAZF@CNT(10,10) were found to have the negative adsorption energy, which indicates that these adsorption processes are exothermic and thermodynamically favorable. The total energy of DAAzF@CNT(6,6) was higher than that of DAAZF/CNT(6,6) but the DAAZF@CNT(8,8) and DAAZF@CNT(10,10) had a lower energy than the DAAzF/CNT(8,8) and DAAzF@CNT(10,10), respectively. It is suggested that the DAAzF might spontaneously assemble inside the two CNTs of larger diameters. The calculated potential energy curves showed that that the CN bond thermal decomposition of the DAAzF was not significantly affected when DAAzF was assembled outside the three CNTs or inside the CNT(8,8) and CNT(10,10). However, the thermal decomposition of DAAzF could be promoted when it was assembled within the CNT(6,6). Our theoretical results would be very valuable for the design of the energetic nanocomposites based on CNTs and the azofurazan explosives.

Furazan-containing bromoarenes in the Suzuki-Miyaura reaction

The palladium-catalyzed cross-coupling reactions of 3-[bromo(het)aryl]furazans and bromobenzofurazans with arylboronic acids afford target biaryls in good yields. 3-Bromo-4-phenylfurazan containing a bromine atom in the furazan ring undergoes decomposition under the reaction conditions.

Synthesis of 3-nitramino-4-(1H-1,2,3-triazol-1-yl)-1,2,5-oxadiazoles and their salts

Nitration of 3-amino-4-(1H-1,2,3-triazol-1-yl)-1,2,5-oxadiazoles (3-amino-4-triazolylfurazans) with a mixture of NaNO3 and conc. H2SO4 gave for the first time triazolylfurazans with a primary nitramino group attached to the furazan ring. If the starting amino(triazolyl)-furazan contains an aromatic substituent, the latter also undergoes nitration under the conditions studied. Some of these nitramines were converted into salts (K, Na, and NH4).

ChemInform Abstract: Synthesis of 1‐Hydroxybenzotriazoles Angularly Annulated by Furazan or Furoxan Rings.

AbstractFacile routes for the synthesis of triazolobenzoxadiazole (IX) and related N‐oxides [cf.

Theoretical study on the thermal decomposition mechanism of 3,3′-dinitro-4,4′-azoxyfurazan

The molecular structure and thermal decomposition of 3,3′-dinitro-4,4′-azoxyfurazan (DNOAF) were studied at the B3LYP/6-311++G** level of theory. The geometry optimization showed that trans-DNAOF has a twisting configuration due to the substituted NO 2 on the furazan rings and the oxidation of azo-group. The bond dissociation energies of the two C–N bonds which connect the furazan rings and azo-group were found to be 65.9 and 92 kcal/mol, respectively, suggesting that the C–N bond on the side of O-atom of azoxy-group is relatively weak. For the initial decomposition product B1, the activation energy of N 2O elimination was calculated to be up to 88.1 kcal/mol. The O 1–N 5 bond dissociation is a very energetically favorable pathway for the ring-opening reaction of the intermediate B2 because the activation energy was found to be only 0.3 kcal/mol. The following reaction of B2 included the rearrangement of NO 2 to ONO followed by the direct loss of NO group. The whole reaction process of B2 was exothermic.

ChemInform Abstract: Synthesis of Chlorofurazans from Nitrofurazans.

Furazans bearing one and two chlorine atoms can be easily prepared by nucleophilic displacement of a nitro group at a furazan ring upon treatment with the Vilsmeier reagent.

Synthesis of 1-hydroxybenzotriazoles angularly annulated by furazan or furoxan rings

Synthesis of 6-hydroxy-6H-[1,2,3]triazolo[4,5-e][2,1,3]benzoxadiazole and a mixture of isomeric 6-hydroxy-6H-[1,2,3]triazolo[4,5-e][2,1,3]benzoxadiazole-1(3)-oxides is carried out starting from 2,4-dinitrosoresorcinol. Total assignment of the signals in the 13C NMR spectra of O-methylated products of these compounds is performed.

AB INITIO STUDY OF THE MOLECULAR STRUCTURE AND THERMAL CIS–TRANS ISOMERIZATION OF 3,3′-DIAMINO-4,4′-AZOFURAZAN AND 3,3′-DIAMINO-4,4′-AZOXYFURAZAN

In this work, we carried out the density functional theory (DFT) calculations in order to understand the molecular structures and thermal trans–cis isomerization of 3,3′-diamino-4,4′-azofurazan (DAAzF) and 3,3′-diamino-4,4′-azoxyfurazan (DAAF). We found that the azo group oxidation of DAAzF leading to the formation of DAAF induced evidently the twist of azofurazan molecule and weakened one of CN bonds connecting the furazan rings and azo group. This means that DAAzF is more stable than DAAF. In addition, the oxidation of azo group has a significant influence on the energy difference between trans- and cis-isomer of azofurazan. The energy difference between the isomers of DAAF is only about half of that of DAAzF. Furthermore, the thermal trans–cis isomerization of DAAzF and DAAF was found to follow a different mechanism: an inversion mechanism for DAAzF and a rotation mechanism for DAAF. By analyzing the reversible trans–cis isomerization process, we firstly proposed that a self-desensitization effect could be responsible for the low sensitivity of azofurazan. This new desensitization mechanism may be useful in the design of novel high energetic density material.

Furazan‐Functionalized Tetrazolate‐Based Salts: A New Family of Insensitive Energetic Materials

Insensitive energetic salts: A series of furazan-functionalized tetrazolate-based energetic salts (see figure) were synthesized and characterized. All of the salts exhibit excellent thermal stabilities and high positive heats of formation.Furazan-functionalized tetrazolate-based energetic salts (1-13) were prepared by direct treatment of neutral 4-amino-3-(5-tetrazole)furazan and a Lewis base or by simple metathesis reactions of its barium salt formed in situ with the corresponding sulfate salts in aqueous solution. Key physical properties, such as melting point, thermal stability, density, hypergolicity, and sensitivity to shock, were measured. The relationship between their structures and these properties was determined. Most of salts exhibit better thermal stability than their 5-nitrotetrazolate and 5-nitraminotetrazolate analogues as well as other furazan-based salts. The structures of representative aminoguanidinium (4), carbonic hydrazylhydrazidinium (9), and 1,4-dimethyl-5-aminotetrazolium salts (13) were further confirmed by single-crystal X-ray analysis. Their densities, heats of formation, detonation pressures and velocities, and specific impulses were calculated. All of the salts possess high positive heats of formation. The effect of the furazan ring on these physicochemical properties was examined and discussed.