Nucleophilic addition of hydroxylamine, methoxylamine, and hydrazine to malononitrileoxime

Recent Progress on Nitrogen-Rich Energetic Materials Based on Tetrazole Skeleton

Development of nitrogen-rich energetic materials has gained much attention because of their remarkable properties including large nitrogen content and energy density, good thermal stability, low sensitivity, good energetic performance, environmental friendliness and so on. Tetrazole has the highest nitrogen and highest energy contents among the stable azoles. The incorporation of diverse explosophoric groups or substituents into the tetrazole skeleton is beneficial to obtain high-nitrogen energetic materials having excellent energetic performance and suitable sensitivity. In this review, the development of high-nitrogen energetic materials based on tetrazole skeleton is highlighted. Initially, the property and utilization of nitrogen-rich energetic materials are presented. After showing the advantage of the tetrazole skeleton, the high-nitrogen energetic materials based on tetrazole are classified and introduced in detail. Based on different types of energetic materials (EMs), the synthesis and properties of nitrogen-rich energetic materials based on mono-, di-, tri- and tetra-tetrazole are summarized in detail.

Synthesis, Crystal Structure, and Characterization of Energetic Salts Based on 3,5-Diamino-4H-Pyrazol-4-One Oxime

In order to broaden the study of energetic cations, a cation 3,5-diamino-4H-pyrazol-4-one oxime (DAPO) with good thermal stability was proposed, and its three salts were synthesized by a simple and efficient method. The structures of the three salts were verified by infrared spectroscopy, mass spectrometry, elemental analysis, and single crystal X-ray diffraction. The thermal stabilities of the three salts were verified by differential scanning calorimetry and thermos-gravimetric analysis. DAPO-based energetic salts are analysed using a variety of theoretical techniques, such as 2D fingerprint, Hirshfeld surface, and non-covalent interaction. Among them, the energy properties of perchlorate (DAPOP) and picrate (DAPOT) were determined by EXPLO5 program combined with the measured density and enthalpy of formation. These compounds have high density, acceptable detonation performance, good thermal stability, and satisfactory sensitivity. The intermolecular interactions of the four compounds were studied by Hirshfeld surface and non-covalent interactions, indicating that hydrogen bonds and π-π stacking interactions are the reasons for the extracellular properties of perchlorate (DAPOP) and picrate (DAPOT), indicating that DAPO is an optional nitrogen-rich cation for the design and synthesis of novel energetic materials with excellent properties.

Synthesis and characterization of thermally stable energetic complexes with 3,5-diaminopyrazolone-4-oxime as a nitrogen-rich ligand

Two thermally stable complexes based on DAPO were synthesized. The thermal decomposition temperatures were 287 °C and 344 °C, respectively. The detonation properties of the complexes were excellent with good detonation velocity and detonation pressure superior to that of TNT.

Hydrogen-bonding landscape of the carbamoyl-cyano-nitro-somethanide anion in the crystal structure of its ammonium salt

The structure of the title salt, ammonium carbamoyl-cyano-nitro-somethanide, NH4 +·C3H2N3O2 -, features the co-existence of different hydrogen-bonding patterns, which are specific to each of the three functional groups (nitroso, carbamoyl and cyano) of the methanide anion. The nitroso O-atoms accept as many as three N-H⋯O bonds from the ammonium cations [N⋯O = 2.688 (3)-3.000 (3) Å] to form chains of fused rhombs [(NH4)(O)2]. The most prominent bonds of the carbamoyl groups are mutual and they yield 21 helices [N⋯O = 2.903 (2) Å], whereas the cyano N-atoms accept hydrogen bonds from sterically less accessible carbamoyl H-atoms [N⋯N = 3.004 (3) Å]. Two weaker NH4 +⋯O=C bonds [N⋯O = 3.021 (2), 3.017 (2) Å] complete the hydrogen-bonded environment of the carbamoyl groups. A Hirshfeld surface analysis indicates that the most important inter-actions are overwhelmingly O⋯H/H⋯O and N⋯H/H⋯N, in total accounting for 64.1% of the contacts for the individual anions. The relatively simple scheme of these inter-actions allows the delineation of the supra-molecular synthons, which may be applicable to crystal engineering of hydrogen-bonded solids containing polyfunctional methanide anions.

Novel Human Aminopeptidase N Inhibitors: Discovery and Optimization of Subsite Binding Interactions

Aminopeptidase N (APN/CD13) is a zinc-dependent M1 aminopeptidase that contributes to cancer progression by promoting angiogenesis, metastasis, and tumor invasion. We have previously identified hydroxamic acid-containing analogues that are potent inhibitors of the APN homologue from the malarial parasite Plasmodium falciparum M1 aminopeptidase (PfA-M1). Herein, we describe the rationale that underpins the repurposing of PfA-M1 inhibitors as novel APN inhibitors. A series of novel hydroxamic acid analogues were developed using a structure-based design approach and evaluated their inhibition activities against APN. N-(2-(Hydroxyamino)-2-oxo-1-(3',4',5'-trifluoro-[1,1'-biphenyl]-4-yl)ethyl)-4-(methylsulfonamido)benzamide (6ad) proved to be an extremely potent inhibitor of APN activity in vitro, selective against other zinc-dependent enzymes such as matrix metalloproteases, and possessed limited cytotoxicity against Ad293 cells and favorable physicochemical and metabolic stability properties. The combined results indicate that compound 6ad may be a useful lead for the development of anticancer agents.

Degradation mechanisms of carbamazepine by δ-MnO2: Role of protonation of degradation intermediates

Carbamazepine (CBZ), a widely used antiepileptic drug, is refractory to biological wastewater treatment. Rapid removal of CBZ is possible using synthetic manganese oxide (δ-MnO₂) but the removal mechanisms require further investigation. In this study, CBZ degradation by δ-MnO₂ was carried out at different pH to further explore the degradation mechanisms. Results show that CBZ degradation by δ-MnO₂ was highly pH dependent, and rapid degradation occurred when pH <2.8. Based on the density functional theory calculations, increasing [H⁺] not only increased the reactivity of δ-MnO₂, but also enhanced the secondary reactions of the intermediates. During the degradation process, protonation of CBZ degradation intermediates, instead of CBZ, played an important role. The overall kinetics of CBZ degradation was then described by the retarded first-order model. The initial rate (r_init) in the model between pH 2.0 and 6.2 was determined to be r_init = (2.41 ± 0.51) × 10^-3[CBZ]^1.21[MnO₂]^1.07[H⁺]^1.41. This is the first report revealing that protonation of intermediates from CBZ degradation can improve the CBZ oxidation by δ-MnO2. The pathways of CBZ degradation by δ-MnO₂ were also proposed. The results of this study provide a new insight into the processing mechanism.

A three-component cocrystal: benzoyl(hydroxyimino)acetonitrile–18-crown-6–water (2/1/4)

In the title compound, 2C9H6N2O2·C12H24O6·4H2O, the 18-crown-6 (1,4,7,10,13,16-hexaoxacyclooctadecane) molecule resides across a centre of inversion. The adduct exists as a molecular hydrogen-bonded complex featuring integration of two kinds of synthons,viz.[(18-crown-6)(H2O)4] [O...O = 2.8645 (18)–2.9014 (18) Å] and an oxime/aqua ensemble, PhC(O)C(CN)NOH...OH2[O...O = 2.5930 (18) Å]. The reliability of the oxime/aqua motif, sustained by the highly acidic cyanooxime, is an essential factor in the construction of multicomponent cocrystals and the accommodation of oxime species in macrocyclic hosts. The supramolecular structure is generated by the alternation of hydrophilic [(18-crown-6)(H2O)4] layers and bilayers of benzoyl(hydroxyimino)acetonitrile molecules, resulting in stacking interactions between the phenyl and cyano groups of 3.666 (2) Å.

Linear Trinuclear Copper(II) Complexes Derived from the Nucleophilic Addition Products of Dicyanonitrosomethanide [C(CN)2(NO)]–: Syntheses, Structures, and Magnetic Properties

Two novel trinuclear CuII complexes have been synthesised from the nucleophilic addition derivatives of the small cyano anion, dicyanonitrosomethanide (dcnm). The reaction of CuII with the water adduct ligand, carbamoylcyanonitrosomethanide (ccnm) and teaH3 (triethanolamine) in a basic MeOH/MeCN solution results in the formation of [Cu3(acnm)2(teaH2)2]·2MeOH (1) (acnm = amidocarbonyl(cyano)nitrosomethanide and teaH2– = singly deprotonated triethanolamine). The reaction of CuII with dicyanonitrosomethanide (dcnm) and m-xylenediamine in a basic MeOH/MeCN solution results in the formation of [Cu3(cimm)2(a3acnm)2]·6MeCN (2) (cimm = cyano(imido(methoxy)methyl)nitrosomethanide and a3acnm = {amino(3-aminomethylphenyl)methylimino}methyl(cyanonitrosomethanide)). Both complexes display linear trinuclear CuII metallic cores. Solid state DC magnetic susceptibility studies were performed on 1 and 2. Compound 1 revealed very strong antiferromagnetic interactions between central and terminal Cu atoms, while compound 2 displayed ferromagnetic interactions because of the orthogonal relationship of the terminal and the central ‘magnetic’ orbitals, which contrasts with these orbitals being coplanar in 1 thus providing strong superexchange pathways involving Cu-N-O-Cu moieties.

Approaches towards the synthesis of 5-aminopyrazoles

The biological and medicinal properties of 5-aminopyrazoles have prompted enormous research aimed at developing synthetic routes to these heterocyles. This review focuses on the biological properties associated with this system. Various synthetic methods developed up to 2010 for these compounds are described, particularly those that involve the reactions of β-ketonitriles, malononitrile, alkylidenemalononitriles and their derivatives with hydrazines, as well as some novel miscellaneous methods.

Nitrosation of malononitrile by HONO, ClNO and N₂O₃: a theoretical study

Nitrosation reactions of malononitrile by three nitrosating agents, HONO, ClNO, and N(2)O(3), have been theoretically investigated at the B3LYP/cc-pVTZ and MP2/cc-pVDZ levels. Two possible competitive paths for nitrosation of malononitrile to give 2-nitroso-malononitrile were proposed: (a) direct C-nitrosation and (b) N-nitrosation and subsequent nitroso transfer from N to C atom. The calculations show that at both B3LYP and MP2 levels, path b is kinetically favored over path a for nitrosations by HONO and N(2)O(3). In the case of ClNO, the B3LYP predicts preference of path b, while the MP2 calculations suggest that both paths have similar rate-determining barriers. The data suggest that N(2)O(3) is the preferred nitrosating agent for the nitrosation of malononitrile in aqueous solution. Transformation of 2-nitroso-malononitrile to form malononitrileoxime via intramolecular proton transfer has also been explored, and it is found that inclusion of an assistant water molecule can drastically accelerate the tautomerization.

Multiplicity control in the polygeminal diazeniumdiolation of active hydrogen bearing carbons: chemistry of a new type of trianionic molecular propeller

Over a century ago, Traube reported the reaction of four nitric oxides with acetone and sodium ethoxide to yield sodium methanebis(diazene-N-oxide-N'-hydroxylate) and sodium acetate. However, when this reaction is carried out in the presence of nitric oxide at slightly elevated pressures (35-40 psi), a product corresponding to the addition of six nitric oxides, sodium methanetris(diazene-N-oxide-N'-hydroxylate), forms as the main product in addition to a trace of the previously observed sodium methanebis(diazene-N-oxide-N'-hydroxylate) and sodium acetate. The corresponding potassium salts form when potassium hydroxide is employed as the base, while lithium hydroxide results in the formation of lithium methanebis(diazene-N-oxide-N'-hydroxylate) exclusively. Nitric oxide reacts with 3,3-dimethylbutan-2-one in the presence of sodium and potassium hydroxide in methanol to yield sodium and potassium 3,3-dimethylbutan-2-one-1,1,1-tris(diazene-N-oxide-N'-hydroxylate), respectively. In contrast, the reaction in the presence of lithium hydroxide forms lithium methanebis(diazene-N-oxide-N'-hydroxylate) and lithium pivalate. The differential reactivity of nitric oxide with acetone and 3,3-dimethylbutan-2-one in the presence of the three bases is attributed to competing hydrolytic reactions of the acetyl and trimethylacetyl group-containing intermediates. A mechanism is proposed for the nitric oxide addition to active methyl groups in these reactions, where the product distribution between the di- and trisubstituted methanes is under kinetic control of the competing reactions. The products are characterized by NMR and IR spectroscopy, differential scanning calorimetry, and elemental analysis. Two differentially hydrated forms of potassium methanetris(diazene-N-oxide-N'-hydroxylate) are characterized by single-crystal X-ray diffraction. From the metathesis reaction of the silver salt of methanetris(diazene-N-oxide-N'-hydroxylate) with ammonium iodide, the corresponding ammonium salt is isolated in 59% yield, but only trace amounts of methylated products form in the reaction of the silver salt with methyl iodide. Density functional calculations (B3LYP/6-311++G) are used to evaluate the bonding, ground-state structures, and energy landscape for the different conformers of methanetris(diazene-N-oxide-N'-hydroxylate)(3-) trianion, a new type of a molecular propeller, and its corresponding triprotonated acid.