Metal-Free Reversible Double Cyclization of Cyanuric Diazide to an Asymmetric Bitetrazolate via Cleavage of the Six-Membered Aromatic Ring

Crystallization of the reaction mixture of 2-amino-4,6-diazido-1,3,5-triazine and excess tert-butylamine results in the isolation of tert-butylammonium N,N-[1'H-(1,5'-bitetrazol)-5-yl]cyanamidate, suggesting a complex decyclization/cyclization rearrangement involving breakage of the six-membered aromatic ring and the formation of two new five-membered azole rings mediated by deprotonation of the precursor by the amine. The addition of tert-butylamine to 2-amino-4,6-diazido-1,3,5-triazine gives spectroscopic indication of thermodynamically unfavorable reactivity in low-dielectric solvents, and high-level quantum chemical computations also suggest its formation to be unfavorable. A computed interconversion pathway describes the likely reaction mechanism and supports the general thermodynamic unfavorability of the reaction and the requirement for a high-dielectric environment to template formation of the ionic product and its trapping by crystallization.

Transition-metal-mediated reduction and reversible double-cyclization of cyanuric triazide to an asymmetric bitetrazolate involving cleavage of the six-membered aromatic ring

Cyanuric triazide reacts with several transition metal precursors, extruding one equivalent of N₂ and reducing the putative diazidotriazeneylnitrene species by two electrons, which rearranges to N-(1'H-[1,5'-bitetrazol]-5-yl)methanediiminate (biTzI^2-) dianionic ligand, which ligates the metal and dimerizes, and is isolated from pyridine as [M(biTzI)]₂Py₆ (M = Mn, Fe, Zn, Cu, Ni). Reagent scope, product analysis, and quantum chemical calculations were combined to elucidate the mechanism of formation as a two-electron reduction preceding ligand rearrangement.

Properties and Promise of Catenated Nitrogen Systems As High-Energy-Density Materials

The properties of catenated nitrogen molecules, molecules containing internal chains of bonded nitrogen atoms, is of fundamental scientific interest in chemical structure and bonding, as nitrogen is uniquely situated in the periodic table to form kinetically stable compounds often with chemically stable N-N bonds but which are thermodynamically unstable in that the formation of stable multiply bonded N₂ is usually thermodynamically preferable. This unique placement in the periodic table makes catenated nitrogen compounds of interest for development of high-energy-density materials, including explosives for defense and construction purposes, as well as propellants for missile propulsion and for space exploration. This review, designed for a chemical audience, describes foundational subjects, methods, and metrics relevant to the energetic materials community and provides an overview of important classes of catenated nitrogen compounds ranging from theoretical investigation of hypothetical molecules to the practical application of real-world energetic materials. The review is intended to provide detailed chemical insight into the synthesis and decomposition of such materials as well as foundational knowledge of energetic science new to most chemists.

Facile synthesis of 1,5-disubstituted tetrazoles by reacting a ruthenium acetylide complex with trimethylsilyl azide

Treatment of [Ru]-C[triple bond, length as m-dash]CPh (1, [Ru] = (η⁵-C₅H₅)(dppe)Ru, dppe = Ph₂PCH₂CH₂PPh₂) with trimethylsilyl azide afforded the cationic nitrile complex {[Ru]NCCH₂Ph}[N₃] (2) and the further cycloaddition of 2 with trimethylsilyl azide at 60 °C afforded the N(2)-bound tetrazolato complex [Ru]N₄CCH₂Ph (3). The regiospecific alkylation of 3 gave a series of cationic N(2)-bound N(4)-alkylated-5-benzyl tetrazolato complexes {[Ru]N₄(CH₂R)CCH₂Ph}[Br] (4a, R = C₆F₅; 4b, R = Ph; 4c, R = 4-CN-C₆H₄; 4d, R = 2,6-F₂-C₆H₃; 4e, R = 6-CH₂Br-C₅NH₃) and the subsequent cleavage of the Ru-N bond of 4a-4e gave N(1)-alkylated-5-benzyl tetrazoles N₄(CH₂R)CCH₂Ph (5a-5e) in good to excellent yields and [Ru]-Br, which, on reacting with phenylacetylene, resulted in the formation of 1 thus forming a reaction cycle. The structures of 2, 3, 4a, 4c and 5a were confirmed by single-crystal X-ray diffraction analysis.

Tetrazoles via Multicomponent Reactions

Tetrazole derivatives are a prime class of heterocycles, very important to medicinal chemistry and drug design due to not only their bioisosterism to carboxylic acid and amide moieties but also to their metabolic stability and other beneficial physicochemical properties. Although more than 20 FDA-approved drugs contain 1 H- or 2 H-tetrazole substituents, their exact binding mode, structural biology, 3D conformations, and in general their chemical behavior is not fully understood. Importantly, multicomponent reaction (MCR) chemistry offers convergent access to multiple tetrazole scaffolds providing the three important elements of novelty, diversity, and complexity, yet MCR pathways to tetrazoles are far from completely explored. Here, we review the use of multicomponent reactions for the preparation of substituted tetrazole derivatives. We highlight specific applications and general trends holding therein and discuss synthetic approaches and their value by analyzing scope and limitations, and also enlighten their receptor binding mode. Finally, we estimated the prospects of further research in this field.

Cu(NO3)2-catalysed Direct Synthesis of 5-substituted 1H-tetrazoles from Alcohols or Aldehydes

A simple, convenient and practical protocol to synthesise 5-substituted 1 H-tetrazoles from alcohols or aldehydes is reported. Using ammonia and sodium azide as nitrogen sources and Cu(NO3)2 as catalyst, benzylic alcohols and benzaldehydes were directly converted into 5-substituted 1 H-tetrazoles in a one-pot procedure.

Phenylselanyl-1H-1,2,3-triazole-4-carbonitriles: synthesis, antioxidant properties and use as precursors to highly functionalized tetrazoles

We describe herein our results on the synthesis, antioxidant properties and chemical diversification of phenylselanyl-1H-1,2,3-triazole-4-carbonitriles.

Sulfonic acid-functionalized silica-coated magnetic nanoparticles as an efficient reusable catalyst for the synthesis of 1-substituted 1H-tetrazoles under solvent-free conditions

Regarding green chemistry goals, silica-coated magnetite nanoparticles open up a new avenue to introduce a very useful and efficient system for facilitating catalyst recovery in different organic reactions. Therefore, in this paper the preparation of sulfonic acid-functionalized silica-coated magnetic nanoparticles with core-shell structure (Fe3O4@silica sulfonic acid) is presented by using Fe3O4 spheres as the core and silica sulfonic acid nanoparticles as the shell. The catalyst was characterized by infrared spectroscopy, scanning electron microscopy, X-ray diffraction analysis, dynamic light scattering, thermogravimetric analysis and vibrating sample magnetometry. Nanocatalyst can be recovered using an external magnet and reused for subsequent reactions 6 times without noticeable deterioration in catalytic activity.

SiO2–H3BO3 promoted solvent-free, green and sustainable synthesis of bioactive 1-substituted-1H-tetrazole analogues

Eco-friendly and expeditious synthesis of tetrazole derivatives.

Computationally motivated synthesis and enzyme kinetic evaluation of N-(β-d-glucopyranosyl)-1,2,4-triazolecarboxamides as glycogen phosphorylase inhibitors

N-(β-d-Glucopyranosyl)-1,2,4-triazolecarboxamides discovered as low μM inhibitors of glycogen phosphorylase b.

A rapid metal free synthesis of 5-substituted-1H-tetrazoles using cuttlebone as a natural high effective and low cost heterogeneous catalyst

A convenient, rapid and metal free synthesis of 5-substituted-1H-tetrazoles by [3 + 2] cycloaddition reaction of nitriles with sodium azide. Cuttlebone as a natural low cost heterogeneous catalyst affords 5-substituted-1H-tetrazoles rapidly with high efficiency.

A review of syntheses of 1,5-disubstituted tetrazole derivatives

This report provides a brief overview of the various representative literature procedures for the synthesis of 1,5-disubstituted tetrazoles (1,5-DSTs) and fused 1,5-disubstituted tetrazoles with more than 120 references. Most of the published methods for the synthesis of 1,5-DSTs include the use of nitriles, amides, thioamides, imidoyl chlorides, heterocumulenes, isocyanates, isothiocyanates, carbodiimides, ketenimines, ketones, amines, and alkenes as the starting materials. The transformation of 1- and 5-substituted tetrazoles into 1,5-DSTs is also covered in this report.