Reactions with diazoazoles. Part VI. Unequivocal synthesis of 3-methyl-3h-azolotetrazoles. Correction of the formerly described 3-methylazolotetrazoles in favour of mesoionic 2-methylazolotetrazoles

3-Methyl-3H-pyrazolo[1,5-d]tetrazoles 2 and 3-methyl-6-phenyl-3H-1,2,4-triazolo[1,5-d]tetrazole (4) have been unequivocally synthesized by annulation of the tetrazole moiety to the pyrazole resp. 1,2,4-triazole system. The constitution of some N-methyl substituted azolotetrazoles, formerly described as 3-methyl-3H-pyrazolo[1,5-d]tetrazoles 2, 3-methyl-6-phenyl-3H-1,2,4-triazolo[1,5-d]tetrazole (4) and 1-methyl-6-phenyl-1H-1,2,4-triazolo[4,3-d]tetrazole (5), has to be revised in favour of the corresponding mesoionic 2-methyl derivatives 2′, 4′, 5′. The structures of 3-methyl-3H- as well as of 2-methyl-2H-pyrazolo[1,5-d]tetrazole derivatives 2a, 2c, 2′a have been determined by X-ray analyses. The azapentalenic system is aromatic in all three measured compounds and mesoionic in the case of the 2-methyl-2H- substitution pattern. The phenyl and ester substituents are coplanar with the azapentalene system. 3-, 2-, and 1-Methylpyrazolo[1,5-d]tetrazoles exhibit different behaviour when allowed to react with stannous chloride or sodium ethoxide. Azolotetrazoles with a methyl substituent at N-1, N-2 or N-3 of the tetrazole moiety can be distinguished by a combination of ¹H and ¹³C nmr with respect to the chemical shifts of the N-methyl group and the bridgehead carbon. Results of semiempirical calculations of the pyrazolo[1,5-d]tetrazole anion and of its N-methyl derivatives are discussed.     

Formation of organotinnitrogen bonds : VI. The intermolecular association of 2-(tri-n-butylstannyl)-tetrazoles in solution

The intermolecular association of 2-(tri-n-butylstannyl)tetrazoles in benzene solution has been evaluated by the measurement of the apparent molecular weight. The degree of the association is highly dependent on the steric effect of the 5-substituent of the tetrazoles. Low temperature NMR spectra of CDCl₃ solutions of 2-(tri-n-butylstannyl)-5-phenyltetrazole and -5-(p-nitrophenyl)tetrazole displayed temperature- and concentration-dependencies. As the temperature decreases, the benzene and tetrazole rings become less coplanar. This may be attributed to the closer polymeric association of the 1-nitrogen to tin at low temperature. The intermolecular associated form of 2-(tri-n-butylstannyl)tetrazoles in less polar solvents such as benzene and chloroform is confirmed as a 1,3-structure (A).     

Catalytic Synthesis of 5‐Substituted Tetrazoles: Unexpected Reactions and Products

Tetrazoles are incredibly useful organic molecules with a wide range of applications from medicinal chemistry as carboxylic acid isosteres to high energy density materials in space research. In an effort to develop an easy protocol for the synthesis of tetrazoles from nitriles, we used nano‐Ag‐TiO₂ as an efficient heterogeneous catalyst for the reaction of various nitriles and sodium azide to afford 5‐substituted tetrazoles in excellent yields. By this method, a wide variety of aryl nitriles underwent [3 + 2] cycloaddition to afford tetrazoles in excellent yields. Further reaction of tetrazoles with ethylchloroacetate resulted in the formation of expected products, except for a bis‐tetrazole, which underwent ring opening and subsequent reaction to afford an unusual product. The bis‐tetrazole also formed an unusual polymeric sodium complex in aq. NaOH solution. X‐ray crystallography revealed a distorted octahedral geometry for the complex, which forms a three‐dimensional network of chains interlinked by bis‐tetrazole moieties through a network of H‐bonds.     

1H- und 13C-NMR-Untersuchungen zur Struktur N-substituierter Tetrazole—Die Strukturen des N-Methoxycarbonyl-, N-Acetyl- und N-(Tri-n-butylstannyl)-tetrazols sowie Substituenteneffekte auf δ13C und 1J(CH)

The ¹H and ¹³C NMR spectra of several isomeric N-substituted tetrazoles have been investigated. ¹³C NMR is shown to be more useful for distinguishing between structural isomers of N-substituted tetrazoles except for those carrying electropositive substituents like SnBu₃. Correlations of δC-5 (inverse) and ¹J(C-5,H) with s?₁ found for 1-substituted tetrazole allowed the identification of the N SnBu₃ derivative as 1-(tri-n-butylstannyl)tetrazole. The phenyl carbon chemical shift difference ΔC′ = δC-3′-δC-2′ is insignificant for structure elucidation and conformational studies of N-substituted 5-phenyltetrazoles; ΔH′ from ¹H NMR spectra seems to be more useful.     

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.     

An Environmentally Friendly Method for N‐Methylation of 5‐Substituted 1H‐Tetrazoles with a Green Methylating Reagent: Dimethyl Carbonate

An environmentally friendly method was established for the N‐methylation of the 5‐substituted 1H‐tetrazoles with a green reagent: DMC. DABCO was the optimal catalyst, and hazardous chemicals were avoided in this protocol. A plausible catalytic mechanism is proposed, which consists of a DABCO‐activated process and a thermally induced rearrangement of tetrazole carbamates.     

Regioselective and Stereoselective Addition of Tetrazole Derivatives to Electron‐poor Acetylenic Esters in the Presence of Triphenylphosphine

Protonation of the highly reactive 1:1 intermediates produced in the reaction between triphenylphosphine and acetylenic esters by tetrazole derivatives leads to the formation of vinyltriphenylphosphonium salts. The cation of these salts undergoes an addition reaction with the counter anion in CH₂Cl₂ at room temperature to yield the corresponding stabilized phosphorus ylides. Elimination of triphenylphosphine from the stabilized phosphorus ylides leads to the corresponding electron‐poor N‐vinyl tetrazoles in fairly high yields. Structures of N‐vinyl tetrazoles were determined by IR, ¹H NMR, ¹³C NMR and single crystal X‐ray structure analyses. The reaction is fairly regioselective and stereoselective.     

Synthesis of New Functionally Substituted 1-R-tetrazoles and Their 5-Amino Derivatives

It has been shown that amino derivatives of sulfanilamide, and also some functionally substituted primary arylamines and cycloalkylamines, undergo heterocyclization with triethyl orthoformate and sodium azide with the formation of 1-monosubstituted tetrazoles. Primary amines of the azole series, 5-aminotetrazole, 5-amino-1-methyltetrazole, 4-amino-1,2,4-triazole, and also less basic arylamines (4-fluoro-3-nitroaniline, 2,6-dibromo-4-nitroaniline) did not react. An efficient method of introducing an amino group into position C₍₅₎ of the tetrazole ring of 1-aryltetrazoles is proposed, based on alkaline decomposition of the tetrazole ring and heterocyclization of the resulting N-arylcyanamides on interaction with ammonium azide generated in situ. __________ Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 8, pp. 1174–1179, August, 2005.     

Refinement of Copper(II) Azide with 1‐Alkyl‐5H‐tetrazoles: Adaptable Energetic Complexes

A concept for stabilizing highly sensitive and explosive copper(II) azide with 1‐N‐substituted tetrazoles is described. It was possible to stabilize the system by the use of highly endothermic, nitrogen‐rich ligands. The sensitivities of the resulting energetic copper coordination compounds can be tuned further by variation of the alkyl chain of the ligands and by phlegmatization of the complexes with classical additives during the synthesis. It is demonstrated, using the compound based on 1‐methyl‐5H‐tetrazole ([Cu(N₃)₂(MTZ)], 1 ) that this class of complexes can be applied as a potential replacement for both lead azide (LA) and lead styphnate (LS). The complex was extensively investigated according to its chemical (elemental analysis, single‐crystal and powder X‐ray diffraction, IR spectroscopy, scanning electron microscopy) and physico‐chemical properties (differential thermal analysis, sensitivities towards impact, friction, and electrostatic discharge) compared to pure copper(II) azide.     

A DFT study on the structure–property relationship of amino-, nitro- and nitrosotetrazoles, and their N-oxides: new high energy density molecules

We explore herein the structure, stability, heat of explosion, density, and the performance properties of amino, nitro, and nitroso substituted tetrazoles and their N-oxides using the density functional theory calculations at the B3LYP/aug-cc-pVDZ level. N-Nitro compounds have lower densities compared with those of C-nitrotetrazoles. Kamlet-Jacob semi-empirical equations were used to calculate the performance properties of designed compounds. The higher performance of tetrazole-N-oxides is due to their higher densities (2.110–2.287 g/cm³). Heat of explosion, stability, density and performance properties are related to the number and relative positions of NO₂, NH₂, and NO groups of the tetrazole ring. The designed molecules satisfy the criteria of high energy materials.     

The Molecular and Electronic Structure of Nickelatetrazole – A Theoretical Study

Nickelatetrazoles have been proposed as intermediates in the course of the photoreaction of Ni^II complexes of [NiP₂(N₃)₂] constitution (P₂: mono‐ or diphosphane ligands). However, any metallatetrazoles as well as their organic analogue, 5 H‐carbatetrazole, could neither be prepared nor identified up to now. Based on density functional theory (DFT) calculations, predictions are given concerning the molecular and electronic structure of tetrazoles. While 5 H‐tetrazole is indeed a rather unstable species, metallatetrazole moieties in square‐planar d⁸ transition metal complexes should be experimentally accessible.     

Synthesis and characterisation of new copper(II) coordination polymers constructed from pyrazine–tetrazole ligands with the formation of a water cluster

Three novel bis-tetrazole ligands (1–3) containing carboxylate functional groups on the tetrazole rings and a rigid pyrazine linker unit, for the construction of coordination polymers when coordinated to copper(II) ions, were synthesised and structurally characterised. The use of pyrazine as a rigid linker between the two tetrazole units was expected to increase the dimensionality of the solid phase polymeric network of the resulting copper(II)-containing compounds. X-ray structures of the ligands revealed the effect of the substitution position on the tetrazole ring of the ester/carboxylate groups. Higher solid phase dimensionality was successfully achieved as shown by the layered two-dimensional (2-D) coordination structure being formed when the pyrazine bis-tetrazole systems were reacted with copper(II) chloride, although not in the expected manner. There was no interaction between the pyrazine nitrogen atoms and the metal ion. Computational studies showed that this was probably due to the geometry, required by the copper ion, to be involved in the close packing between the layers. The 2-D coordination polymer based on the asymmetric substituted pyrazine bis-tetrazole, [Cu(4)(H₂O)](H₂O)₂, was further connected into a three-dimensional (3-D) coordination network through hydrogen bonding between H₂O molecules. These H₂O molecules were connected as a unique 1-D chain throughout the structure.     

Reaction of 5-Aryloxytetrazoles with Dimethyl Sulfoxide and DMSO-Acetic Anhydride. Structure and Quantum-Chemical Calculations of 1-Methylsulfanylmethyl-5-(4-nitrophenoxy)tetrazole

Decomposition of methyl 5-(4-nitrophenoxy)tetrazole-2-carboxylate in dimethyl sulfoxide at room temperature yields a mixture of 1-methylsulfanylmethyl-5-(4-nitrophenoxy)tetrazole, 1- and 2-methyl-5-(4-nitrophenoxy)tetrazoles, and 5-(4-nitrophenoxy)tetrazole. Methyl 5-aryloxytetrazole-2-carboxylates containing electron-donor substituents in the aryloxy group do not give rise to the corresponding products under analogous conditions. The reactions of 5-aryloxytetrazoles [Ar = 4-O₂NC₆H₄, C₆H₅, 2,6-(MeO)₂C₆H₃] with dimethyl sulfoxide in the presence of acetic anhydride lead to mixtures of 1- and 2-methylsulfanylmethyl-5-aryloxytetrazoles whose yield and ratio depend on the substituent in the aryloxy group. The structure of 1-methylsulfanylmethyl-5-(4-nitrophenoxy)tetrazole was studied by X-ray analysis, two-dimensional NMR spectroscopy (HSQC, HMBC, NOESY), and quantum-chemical methods (ab initio, AM1, PM3). A highly selective procedure was developed for the synthesis of 5-(4-nitrophenoxy)tetrazole.__________From Zhurnal Organicheskoi Khimii, Vol. 41, No. 7, 2005, pp. 1076–1084.Original English Text Copyright © 2005 by Dabbagh, Noroozi Pesyan, Bagheri, Takemo, Hayashi.The original article was submitted in English.     

Stereo- and regioselective synthesis of β-amino-β-tetrazolylvinylphosphonates

Addition of 5-substituted tetrazoles to dimethyl [(N,N-diisopropylamino)ethynyl]phosphonate proceeds regio- and stereoselectively to yield (Z)-[2-diisopropylamino-2-(tetrazolyl)vinyl]phosphonic acid dimethyl esters. The Z-configuration of the products was confirmed by ¹Н NMR spectroscopy and single-crystal X-ray diffraction. The reactions occur via nucleophilic attack of tetrazole involving predominantly the N-1 atom of the tetrazole ring.     

Alkylation of tetrazoles with 3-(2-bromoethyl)-1-methoxy-3-methyltriaz-1-ene 2-oxide

Alkylation of tetrazoles with 3-(2-bromoethyl)-1-methoxy-3-methyltriaz-1-ene 2-oxide proceeded at positions 1 and 2 of the tetrazole ring to give a mixture of two isomers.

     

Synthesis and performance of ansa-metallocene catalysts with substituted heterocyclic and indenyl ligands

Synthesis of new ansa-metallocene catalysts incorporating branched alkyl groups alpha to the bridgehead carbon of indenyl and thiapentalenyl ligands is reported. Me₂Si(2-Me-4-Ph-Indenyl)₂ZrCl₂ and Me₂Si(2,5-Me₂-3-Ph-Thiapentalenyl)₂ZrCl₂ type metallocenes with one and two isopropyl groups substituted for 2-methyl substitutents were prepared and used as procatalysts in propylene polymerizations and E/P copolymerizations. The 2-isopropyl groups influenced catalyst activity, molecular weight, and the relative amounts of microstructure errors. In contrast to procatalysts with only 2-methyl groups, polymer molecular weights increased in E/P copolymerizations with 2-isopropyl substituted complexes. The text was submitted by the authors in English.     

Cationic organotin cluster [t‐Bu2Sn(OH)(H2O)]22+2OTf−‐catalyzed one‐pot three‐component syntheses of 5‐substituted 1H‐tetrazoles and 2,4,6‐triarylpyridines in water

The cationic organotin cluster [t‐Bu₂Sn(OH)(H₂O)]₂²⁺2OTf^? is easy to prepare and stable in air. The catalytic activity of [t‐Bu₂Sn(OH)(H₂O)]₂²⁺2OTf^? as a neutral organotin Lewis acid catalyst is probed through the one‐pot three‐component syntheses of 5‐substituted 1H‐tetrazoles from aldehydes, hydroxylamine hydrochloride and sodium azide, and of 2,4,6‐triarylpyridines from aromatic aldehydes, substituted acetophenones and ammonium acetate. The reactions proceed well in the presence of 1 mol% of [t‐Bu₂Sn(OH)(H₂O)]₂²⁺2OTf^? in water and provide the corresponding 5‐substituted 1H‐tetrazoles and 2,4,6‐triarylpyridines in good to excellent yields. The method reported has several advantages such as the catalyst being neutral, low catalyst loading and use of water as a green solvent.     

Probing microphase separation and proton transport cooperativity in polymer‐tethered 1H‐tetrazoles

To elucidate the driving forces for phase separation and proton conductivity in polystyrenic alkoxy 1H‐tetrazole (PS‐Tet), an analogous polystyrenic alkoxy carboxylic acid (PS‐HA) was synthesized and the conductivity and chain dynamics of both materials measured. Proton and polymer motions illustrate dramatic differences in the nonaqueous behavior of carboxylic acids and 1H‐tetrazoles, belying similarities in their aqueous properties. Exceptional interactions between 1H‐tetrazoles drive phase separation not observed in PS‐HA or reported for other azole‐containing homopolymers. PS‐HA and PS‐Tet exhibit both dry (0% relative humidity) and hydrated proton dissociations proportional to their aqueous pK_as, with residual water acting as the proton acceptor in both polymers. While water is the sole contributor to mobility in PS‐HA, PS‐Tet exhibits dynamic interactions with water allowing 1H‐tetrazole moieties to contribute to proton conduction even in the hydrated state. © 2014 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2014 , 52, 1375–1387     

2-alkyl-5-aryltetrazoles as hydrogen bond acceptors

The dissociation constants of the H-complexes formed by 2-alkyl-5-aryltetrazoles and p-fluorophenol in carbon tetrachloride (pK _HB 0.9–1.3) were determined by Fourier-transform IR spectroscopy. 2-Alkyl-5-aryltetrazoles were found to act as medium-strength hydrogen bond acceptors comparable with diazines. The thermodynamic parameters of the equilibrium formation of H-complex with 2-isopropyl-5-phenyltetrazole were determined. The electronic nature of substituents in the tetrazole ring only slightly affects the pK _HB values of tetrazoles.     

Unanticipated formation of a novel octaazacyclodecane ring upon oxidation of a 1,1‐bis‐urazole

Tetrahydrotetrazoles are a little‐explored class of five‐membered heterocycles with four contiguous singly‐bonded N atoms. Recent work in our labs has demonstrated that urazole radicals are amenable to N—N bond formation via radical combination to form such a chain of four N atoms. Previously described 1,1‐bis‐urazole compounds appeared to be convenient precursors to the target tetrazoles via their oxidation to intermediate urazole diradicals, which upon N—N bond formation would complete the tetrazole framework. While oxidation proceeded smoothly, the novel 10‐membered octaaza heterocycle 7,7,18,18‐tetraacetyl‐4,10,15,21‐tetraphenyl‐1,2,4,6,8,10,12,13,15,17,19,21‐dodecaazapentacyclo[17.3.0.0^2,6.0^8,12.0^13,17]docosan‐3,5,9,11,14,16,20,22‐octone, C₄₂H₃₂N₁₂O₁₂, was obtained (36% yield) instead of the expected tetrazole product, as confirmed by X‐ray crystallography. Calculations at the (U)B3LYP/6‐311G(d,p) level of theory suggest that the desired tetrazoles have weak N—N bonds connecting the two urazole units.