Nitrous oxide as a diazo transfer reagent: the synthesis of triazolopyridines

An Acceptor-Substituted N-Heterocyclic ortho-Quinodimethane: Pushing the Boundaries of Polarization in Donor-Acceptor-Substituted Polyenes

We report the synthesis, isolation, and characterization of a stable donor-acceptor substituted ortho-quinodimethane (oQDM). This system with an imidazolidine scaffold as the donor can also be referred to as acceptor-substituted ortho-N-heterocyclic quinodimethane (oNHQ). We have examined the extent of polarization of the conjugated π-system using single-crystal X-ray diffraction, NMR and UV/vis spectroscopy, cyclic voltammetry, and DFT computations. The bond lengths in the phenyl linker do not exhibit the alternation typical of oQDMs. In addition, the 13C and 15N NMR shifts suggest significant charge separation, an interpretation supported by the diatropic ring current determined by NICSZZ(r) computations, which is characteristic of aromatic compounds. DFT calculations show that polarization is an electronic effect that is amplified by steric influences. More strikingly, the oxidation and reduction potentials of the push-pull substituted oQDM are virtually identical to those of authenticated anionic and cationic derivatives. The results therefore indicate that an aromatic zwitterionic structure represents the electronic structure more accurately than a neutral quinoidal Lewis structure, which indicates that the acceptor-substituted oNHQ is a rare example of an organic zwitterion in which the centers of charge are in conjugation. The ambiphilic reactivity of the acceptor-substituted oNHQ, which is evidenced by the dehydrogenation of ammonia borane and the addition of phenylacetylene via heterolytic C-H bond cleavage, further supports its notation as an organic zwitterion and is reminiscent of frustrated Lewis pairs (FLPs). Thus, the acceptor-substituted oNHQ can be considered to be an intramolecular carbogenic FLP in terms of its reactivity.

Nitrous oxide as diazo transfer reagent

Nitrous oxide, commonly known as "laughing gas", is formed as a by-product in several industrial processes. It is also readily available by thermal decomposition of ammonium nitrate. Traditionally, the chemical valorization of N2O is achieved via oxidation chemistry, where N2O acts as a selective oxygen atom transfer reagent. Recent results have shown that N2O can also function as an efficient diazo transfer reagent. Synthetically useful methods for synthesizing triazenes, N-heterocycles, and azo- or diazo compounds were developed. This review article summarizes significant advancements in this emerging field.

Progress and challenges in nitrous oxide decomposition and valorization

Nitrous oxide (N2O) decomposition is increasingly acknowledged as a viable strategy for mitigating greenhouse gas emissions and addressing ozone depletion, aligning significantly with the UN's sustainable development goals (SDGs) and carbon neutrality objectives. To enhance efficiency in treatment and explore potential valorization, recent developments have introduced novel N2O reduction catalysts and pathways. Despite these advancements, a comprehensive and comparative review is absent. In this review, we undertake a thorough evaluation of N2O treatment technologies from a holistic perspective. First, we summarize and update the recent progress in thermal decomposition, direct catalytic decomposition (deN2O), and selective catalytic reduction of N2O. The scope extends to the catalytic activity of emerging catalysts, including nanostructured materials and single-atom catalysts. Furthermore, we present a detailed account of the mechanisms and applications of room-temperature techniques characterized by low energy consumption and sustainable merits, including photocatalytic and electrocatalytic N2O reduction. This article also underscores the extensive and effective utilization of N2O resources in chemical synthesis scenarios, providing potential avenues for future resource reuse. This review provides an accessible theoretical foundation and a panoramic vision for practical N2O emission controls.

A Predictive Chemistry DFT Study of the N2O Functionalization for the Preparation of Triazolopyridine and Triazoloquinoline Scaffolds

The whole reaction mechanism of the functionalization of N2O for the synthesis of triazolopyridine and triazoloquinoline scaffolds has been unveiled by means of DFT calculations. The rate determining step of...