The chemistry of nitroso oxides

Abstract

Nitroso oxides (RNOO) are the isoelectronic analogs of carbonyl oxides (R 2 COO) and ozone (O 3 ) and, as well as these species, possess a three‐centered 4π‐electron system, which determines their chemical properties and reactivity unusual for a family of peroxides. The review is focused on the chemistry of the parent nitroso oxide (HNOO) and its aromatic analogs (ArNOO). The structure, spectral properties, methods for generation, reactivity and mechanisms of various transformations of these species both in the gas and condensed media are discussed in detail. An aromatic substituent significantly stabilizes the π‐system of nitroso oxide. The typical reactions of nitroso oxides are O‐transfer to an appropriate substrate or [3+2]‐cycloaddition to unsaturated bonds. Special attention was paid to the redox isomerization of arylnitroso oxides with ring cleavage that leads to the formation of diene nitrile oxides.

Conformational Transformations in Aromatic Nitroso Oxides

“…It has been reliably established that the solvent significantly affects the ArNOO reactivity. The rate constants of ArNOO monomolecular decay and the activation parameters obtained in nonpolar ( n -hexane), aromatic (benzene), and polar solvents (acetonitrile) have been collected and analyzed in a recent review . It can be assumed that the conformational features of arylnitroso oxides that affect their absolute reactivity also depend on the properties of the medium where the conformational transformation occurs.…”

“…Nitroso oxides RNOO are 1,3-dipolar compounds containing the −N–O–O monovalent functional group. The simplest representative of these compounds HNOO (X = HN, Scheme ) is an isoelectronic analogue of ozone (X = O) and peroxymethylene H 2 COO (X = H 2 C). − Nitroso oxides are recognized to be highly reactive intermediates in a number of oxidative processes, such as photooxidation of inorganic and organic azides and deoxygenation of aromatic nitroso compounds with phosphorus­(III) compounds . Furthermore, HNOO is generated in ammonia flames .…”

“…Furthermore, HNOO is generated in ammonia flames . In all cases, RNOO compounds are formed in reactions of triplet nitrenes RN: with molecular oxygen. , Many theoretical publications and experimental studies addressed the properties of nitroso oxides. ,− A specific feature of the electronic structure of RNOO is that it has a three-centered 4π-electron orbital system. The electronic structure of nitroso oxides can be represented by a superposition of several resonance structures .…”

“…It is known that nitroso oxides exist as two planar isomeric forms, cis and trans, which differ in the position of the terminal oxygen atom with respect to the R moiety:…”

Ortho-Cyclization in Asymmetrically Substituted Arylnitroso Oxides

“…The product composition of the photochemical oxidation of aromatic azides is determined by transformations of the reaction intermediates, nitroso oxides (ArNOO), which are adducts of triplet nitrenes with molecular oxygen. − There are uni- and bimolecular channels of the consumption of nitroso oxides. Their recombination leads to the corresponding nitrosobenzene and nitrobenzene .…”