Investigation of some tetrazole derivatives of 1,8-naphthyridines

Several tetrazole derivatives have been prepared from 7-amino-2-hydroxy-3-phenyl-1,8-naphthyridine (Id). Evidence is presented to demonstrate that the tetrazole ring structure is the dominant species in the solid state and in alkaline solution while the open-chain azido form dominates in acidic solution. In addition it has been shown that the presence of a phenyl group in a position adjacent to the tetrazole nucleus apparently stabilizes the tetrazole ring.     

Selective N(2) alkylation of tetrazole and 5-substituted tetrazoles by alcohols

Alkylation of tetrazole and its 5-substituted derivatives by 5-tert-butyl, isopropyl, and cyclohexyl alcohols in concentrated H₂SO₄ results in high yields of the corresponding 2-alkyltetrazoles alone, irrespective of electronic properties and size of the substituent at the 5-position of the tetrazole ring. The tert-butylation of tetrazole in phosphoric acid results in the formation of a mixture of isomeric 1- and 2-substituted derivatives, the concentration of the 1-isomer increasing with decrease in the concentration of the acid in the mixture.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 12, pp. 1643–1647, December, 1990.     

Comparative semiempirical calculations of tetrazole derivatives

Heats of formation, protonation energies, charge distributions, dipole moments, and geometrical structures of thirty-two 1-, 2-, 1,5-, and 2,5-substituted tetrazoles have been investigated by different semiempirical SCF MO calculations. MNDO and, in some cases, AM 1 methods are the most acceptable for tetrazole derivatives. A number of linear correlations between available experimental data and the calculated energies and charge characteristics have been established. © 1992 John Wiley & Sons, Inc.     

Theoretical investigation on the impact sensitivity of tetrazole derivatives and their metal salts

The relative orders of impact sensitivity of tetrazole derivatives and their metal salts are investigated by examining the activation energy for forming azide in the process of thermal decomposition based on PM3-SCF-MO calculations. It is found that there is a parallel relationship between the activation energy and the sensitivity and a good linear relationship between the experimental impact sensitivity of metal salts of tetrazole and the reaction activation energy. It is shown that treating the metal salts of the tetrazole derivatives as the metal derivatives of tetrazole is meaningful.     

Computational studies on tetrazole derivatives as potential high energy materials

The tetrazole is an important functionality of the most of energetic materials due to 80% nitrogen content, stability, and high enthalpy of formation. The present structure–property relationship study focuses on the optimized geometries of tetrazole derivatives obtained from density functional theory (DFT) calculations at B3LYP/6-31G* levels. The heat of formation (HOF) of tetrazole derivatives have been calculated by designing the appropriate isodesmic reactions. The increase in nitro groups on azole rings shows the remarkable increase in HOF. Density has been predicted by using CVFF force field. Increase in the nitro group increases the density. Detonation properties of the designed compounds were evaluated by using the Kamlet–Jacobs equation based on predicted densities and HOFs. Designed tetrazole derivatives show detonation velocity (D) over 8 km/s and detonation pressure (P) of about 32 GPa. Thermal stability was evaluated via bond dissociation energies (BDE) of the weakest C–NO₂ bond at B3LYP/6-31G* level. Charge on the nitro group has been used to assess the sensitivity correlation. Overall, the study implies that designed compounds of this series are found to be stable and expected to be the novel candidates of high energy materials (HEMs).     

An efficient and expeditious synthesis of di- and trisubstituted amino-phenyl and -benzyl derivatives of tetrazole and [1,3,4]oxadiazol-2-one

A practical protocol for the parallel synthesis and purification of amino tetrazole and [1,3,4]oxadiazol-2-one derivatives as carboxylic acid bioisosteres is described. Phenyl- and benzyl-amines, substituted with tetrazole or [1,3,4]oxadiazol-2-one, were transformed into functionally diverse and novel compounds, with p K a values ranging from 4.9 to 8.4, by two sequential reductive alkylation reactions. These series of di- and trisubstituted amino-phenyl and -benzyl derivatives were produced in solution using solid-supported reagents and were purified by solid-phase extraction (SPE) techniques.     

Synthesis of new tetrazole and triazole substituted pyroglutamic acid and proline derivatives

Racemic 4-(substituted-1H-1,2,3-triazol-1-yl), 4-aryl and 4-(arylmethyl)tetrazolyl-pyroglutamic and proline derivatives were synthesized from dimethyl-2,4-dibromoglutaryle 1 in good yield using mild reaction conditions. The key step for the preparation of the triazole substituted molecule was the 1,3-dipolar cycloaddition of an acetylenic compound with an azido derivative. The tetrazole derivatives were prepared by the selective N2-alkylation of 5-substituted tetrazoles with 1.     

Impact sensitivity and activation energy of pyrolysis for tetrazole compounds

Calculations with both DFT‐B3LYP and semiempirical quantum chemical PM3 methods are carried out on a series of tetrazole derivatives and their metal salts to investigate the relationship between the relative order of impact sensitivity and activation energy of thermal decomposition. The results show that the relative order of sensitivity for the titled compounds can be predicted by examining the activation energy for breaking down of tetrazole ring. © 2000 John Wiley & Sons, Inc. Int J Quant Chem 79: 350–357, 2000     

Two derivatives of 5‐amino­tetrazole: 5‐amino‐1‐phenyl­tetrazole and 5‐amino‐1‐(1‐naphthyl)­tetrazole

In the mol­ecules of 5‐amino‐1‐phenyl­tetrazole, C₇H₇N₅, (I), and 5‐amino‐1‐(1‐naphthyl)­tetrazole, C₁₁H₉N₅, (II), the tetrazole rings and aryl fragments are not coplanar; corresponding dihedral angles are 50.58 (5) and 45.19 (7)° for the two independent mol­ecules of (I), and 64.14 (5)° for (II). Intermolecular N—H⋯N hydrogen bonds between the amino groups and tetrazole N atoms are primarily responsible for formation of two‐dimensional networks extending parallel to the bc plane in both compounds. The presence of the amino group has a distinct effect on the geometry of the tetrazole rings in each case.     

Thermal studies on tetrazole derivatives using a differential scanning calorimeter. I

The thermal decomposition of arylidene tetrazolyl hydrazones has been studied under dynamic and isothermal conditions using a differential scanning calorimeter. Attempts have been made to evaluate the thermochemical and kinetic parameters of these compounds. It has been observed that the thermal stability of the tetrazole derivatives decreases with increasing substitution of nitro groups in the aromatic ring.     

Rearrangement of azidoximes to tetrazole derivatives

Some new azidoximes and their O-substituted derivatives as well as 5-substituted-1-acyloxy- and 1-hydroxytetrazoles were prepared. O-Substitution of azidoximes followed by protonation were found to be the initial steps in their cyclisation to tetrazole derivatives. The mechanism of the cyclisation reaction was proposed and the structure of 5-substituted-1-hydroxytetrazoles discussed.     

四唑及其衍生物的理论研究Ⅷ: 硝氨四唑衍生物的从头算

运用从头计算法,在HF/6-31G^*水平下,全优化计算了7种硝氨四唑衍生物的分子几何和电子结构。结果表明,标题物的四唑环近似为平面构型;2H式中性分子的芳香性大于相应的1H式异构体。5-硝氨-1H四唑分子内氢键使硝氨基与环共面;其余标题物中硝氨基与环垂直。不同水平下的总能量计算表明,标题物中电子相关效应显著;1H式中性分子较2H式的能量高,5-硝氨四唑负离子在三个负离子中最稳定。根据电荷分布阐明了四唑环质子化位置和标题物与金属的配位方式。此外还计算了各标题物的红外光谱及热力学性质。     

Theoretical studies on tautomerism of tetrazole derivatives by polarisable continuum method (PCM)

Computational calculations at B3LYP/6-31++G(d,p) level were employed in the study of the predominant tautomeric forms of 1-H and 2-H tetrazole derivatives (5-NO₂, 5-CF₃, 5-F, 5-H, 5-NH₂, 5-OH, 5-CH₃) in the gas phase and solution using PCM model. For electron withdrawing derivatives in the gas phase and solution 2-H forms are more stable and dominant form. For electron releasing groups in the gas phase and solution with low dielectric constants the 2-H form is more stable but in solvents with high dielectric constants 1-H isomer is dominant form. In addition variation of dipole moments and charges on atoms in the solvents are studied.     

Molecular design of trinitromethyl-substituted nitrogen-rich heterocycle derivatives with good oxygen balance as high-energy density compounds

Density functional theory method was used to study the heats of formation (HOFs), electronic structure, energetic properties, and pyrolysis mechanism of a series of trinitromethyl-substituted heterocycle (including triazole, tetrazole, furazan, tetrazine, and fused heterocycles) derivatives. It is found that the fused ring, tetrazine, and tetrazole are effective structural units for increasing the HOFs of the derivatives. The substitution of the combination of nitro and trinitromethyl is very useful for improving their HOFs. The calculated energetic properties indicate that the combination of the nitro and trinitromethyl is very helpful for improving their detonation properties and oxygen balances (OB). Most of the title compounds have a good OB over zero. The OB of six compounds are very high and over 22. An analysis of the bond dissociation energies for several relatively weak bonds suggests that the N–O bond in the ring is a trigger bond for BIII-1, CI-3, and CI-4, and the ring–NO₂ and (NO₂)₂C–NO₂ bond cleavage is likely to happen in thermal decomposition for the remaining compounds. Considering the detonation performance and thermal stability, seven compounds could be regarded as potential candidates for high-energy compounds. Four compounds may be used as the novel high-energy oxidizers.     

Efficient synthesis of tetrazole derivatives of cytisine using the azido-Ugi reaction

The azido-Ugi reaction with natural alkaloid cytisine was investigated. It was demonstrated that the reaction could be performed with various carbonyls (both aldehydes and ketones) and isocyanides. The transformation proceeded under mild conditions in methanol using TMSN3 as a source of hydrazoic acid to give target tetrazole derivatives of cytisine in up to 98% yield. The diastereoselectivity of this reaction was studied using both aliphatic and aromatic aldehydes. A family of tetrazole derived cytisine compounds was prepared. Selective deprotection of tetrazoles was elaborated to synthesize the corresponding NH-tetrazoles.     

Studies on adsorption of 5-amino tetrazole on silver nanoparticles by SERS and DFT calculations

The surface-enhanced Raman scattering (SERS) studies of 5-amino tetrazole (5AT), a tetrazole derivative, in aqueous silver sol at pH approximately 9 and on deposited colloidal silver films were carried out and compared with the normal Raman spectrum of the molecule. The experimentally observed Raman bands along with their corresponding infrared bands were assigned based on the results of density functional theory (DFT) calculations. The significant changes evidenced between the SERS and the normal Raman spectra combined with the theoretical data obtained for Ag-5AT system demonstrated that the molecule is adsorbed on colloidal Ag particles through the lone pair of electrons of the nitrogen atom. The contribution of the chemical mechanism for the SERS enhancement was proved by the behavior of the electronic absorption spectrum of the Ag colloid upon addition of 5AT. This is further supported by the theoretical calculations that show that the favorable interaction of the frontier orbitals localized on Ag(+) and the negatively charged nitrogen from the tetrazole ring leads to the formation of the stable (up to 130 kJ mol(-1)) charge-transfer complex. The orientation of the adsorbed species with respect to the metal surface was also predicted by applying the "surface selection rule". In addition, the feasibility of the formation of the polymeric species has also been discussed.     

Facile,efficient and eco-friendly synthesis of 5-sulfenyl tetrazole derivatives of indoles and pyrroles

A concise, two-step eco-friendly approach towards the synthesis of 5-sulfenyl tetrazole derivatives of indoles and pyrroles, is reported. The synthesis comprises the oxone-mediated thiocyanation of the starting heterocycles towards intermediate 3-thiocyanato indoles and 2-thiocyanato pyrroles, and their subsequent treatment with sodium azide in 2-propanol/water under zinc bromide promotion.     

Decomposition Mechanism of 5,5′-Bis(tetrazole)-1,1′-dioIate(TKX-50) Anion Initiated by Intramolecular Oxygen Transfer

Density functional theory calculations at the B3LYP/6-31+G^** and B3LYP/6-311++G ^** levels were perfonned on thermal decomposition of 5,5′-bis(tetrazole)-1 ,r-diolate(TKX-50) anion with an intramolecular oxygen transfer being an initial step. Tlie results show that the intramolecular oxygen transfers are the rate-limiting steps for the decomposition of title anion with activation energies being in the range of 287-328 kJ/mol. Judged by the nucleus- independent chemical shift values, the formation of antiaromatic ring in transition state or the decrease of aromaticity of the tetrazole ring of the reactant makes somewhat contribution to the high potential energies of the rate-limiting transition states. However, the activation energies of the following N2 elimination tlirough various pathways are in a low range of 136-166 kJ/mol. The tetrazole ring acts as an electron donor or acceptor in difierent pathways to assist the bond nipture or group elimination. The rate constants in a temperature range of 500-2000 K for all the intramolecular oxygen transferring reactions were obtained. The corresponding linear relationships between InA and 1/T were established.     

Reactions of 1,4-bis(tetrazole)benzenes: formation of long chain alkyl halides

The reactions of 1,4-bis[2-(tributylstannyl)tetrazol-5-yl]benzene with α,ω-dibromoalkanes were carried out in order to synthesise pendant alkyl halide derivatives of the parent bis-tetrazole. This led to the formation of several alkyl halide derivatives, substituted variously at N1 or N2 on the tetrazole ring. The crystal structures of 1,4-bis[(2-(4-bromobutyl)tetrazol-5-yl)]benzene (2-N,2-N′), 1,4-bis[(2-(4-bromobutyl)tetrazol-5-yl)]benzene (1-N,2-N′) and 1,4-bis[(2-(8-bromooctyl)tetrazol-5-yl)]benzene (2-N,2-N′) are reported. Further discussion involves the structure of 1,4-bis[2-(6-bromohexyl)-2H-tetrazol-5-yl]benzene (2-N,2-N′) previously reported.     

Synthesis and characterisation of tetra-tetrazole macrocycles

The syntheses of tetra-tetrazole macrocycles, containing two bis-tetrazole units linked by a variety of alkyl-chain lengths from four to eight carbons, are described. The crystal structures of three of these derivatives are reported, and the molecular conformation in the solid state is compared to that of the previously reported tetra-tetrazole macrocycle and to other bis- and tris(tetrazole)benzene structures. The macrocycle conformation is influenced by the length of the alkyl-chain linker, the relative orientation of the tetrazole rings on the benzene ring and by intermolecular interactions. In the macrocycles based on 1,2-bis(tetrazole)benzene, the adjacent tetrazole rings on the benzene ring are prevented from becoming co-planar on intramolecular (steric) grounds. In the 1,3- and 1,4-bis(tetrazole)benzene derivatives, there is no such impediment, and a co-planar arrangement is observed where intra- and/or intermolecular stacking interactions exist. Deviations from co-planarity are associated with optimisation of intermolecular interactions between the tetrazole rings and adjacent alkyl chains. In the macrocycle based on 1,4-bis(tetrazole)benzene with four-carbon linkers, an intramolecular stacking interaction exists, which precludes the presence of any cavity. In the macrocycle based on 1,3-bis(tetrazole)benzene with six-carbon linkers, a cavity of 10.8×9.4 Å is observed for each molecule in the solid state, although the packing of adjacent molecules is such that there are no extended channels running through the crystal.