Nitrosonium compounds

Other nitrosonium compounds and combinations with water or Lewis acids showed a significant influence on the product distribution (Table 16).84... 

A number of hexahalogenotellurates(IV) have been investigated. A few rather unstable hexafluoro complexes are known, for example the nitrosonium compounds of composition (NO)2XF6 have been obtained40 from the reaction of nitrosulfuryl fluoride, NOS02F, with selenium or tellurium tetrachloride. The selenium compound loses nitrosyl fluoride at room temperature to leave the pentafluoroselenate(lV), whereas the tellurium analogue remains... 

Though stable in non-hydroxylic solvents, nitrosonium compounds react with hydroxyhc solvents ... 

Nitrous acid or nitrite salts may be used to catalyze the nitration of easily nitratable aromatic hydrocarbons, eg, phenol or phenoHc ethers. It has been suggested that a nitrosonium ion (NO + ) attacks the aromatic, resulting initially in the formation of a nitro so aromatic compound (13). Oxidation of the nitro so aromatic then occurs ... 

Arsenic trifluoride (arsenic(III) fluoride), AsF, can be prepared by reaction of arsenic trioxide with a mixture of sulfuric acid and calcium fluoride or even better with fluorosulfonic acid. Chlorine reacts with ice-cold arsenic trifluoride to produce a hygroscopic soHd compound, arsenic dichloride trifluoride [14933-43-8] ASCI2F35 consisting of AsQ. and AsF ions (21). Arsenic trifluoride forms a stable adduct, 2AsF2 SSO, with sulfur trioxide and reacts with nitrosyl fluoride to give nitrosonium hexafluoroarsenate(V) [18535-07-4] [NO][AsFg]. 

Milner (1992) recently described a novel and versatile modification of the Balz-Schiemann reaction. The amine is diazotized with solid nitrosonium tetrafluoro-borate in CH2C12 and, without isolation, the diazonium salt is heated and yields the fluoroarene in good yield. The method is also applicable to aniline derivatives bearing carboxy and hydroxy substituents, compounds which give poor yields in the classical procedure. 

For nitrosyl chloride (Entry 8) and nitrosyl formate (Entry 9), the electrophile is the nitrosonium ion NO+. The initially formed nitroso compounds can dimerize or isomerize to the more stable oximes. 

The synthetic utility of the mercuration reaction derives from subsequent transformations of the arylmercury compounds. As indicated in Section 7.3.3, these compounds are only weakly nucleophilic, but the carbon-mercury bond is reactive to various electrophiles. They are particularly useful for synthesis of nitroso compounds. The nitroso group can be introduced by reaction with nitrosyl chloride73 or nitrosonium tetrafluoroborate74 as the electrophile. Arylmercury compounds are also useful in certain palladium-catalyzed reactions, as discussed in Section 8.2. 

A N—N bond pre-exists in RNOx compound, which then decomposes, leading to N2. Over zeolite-supported Ag and Cu catalysts, the formation of nitrosonium and A-nitroso-A-alkylhydroxylamate intermediates have been assumed by Martens et al. [6], Brosius and Martens [8] and Kharas [7], respectively, to explain the N—N bonding before the release of molecular N2. 

A further point of preparative significance still requires explanation, however. Highly reactive aromatic compounds, such as phenol, are found to undergo ready nitration even in dilute nitric acid, and at a far more rapid rate than can be explained on the basis of the concentration of N02 that is present in the mixture. This has been shown to be due to the presence of nitrous acid in the system which nitrosates the reactive nucleus via the nitrosonium ion, NO (or other species capable of effecting nitrosation, cf. p. 120) ... 

A facile method for the oxidation of alcohols to carbonyl compounds has been reported by Varma et al. using montmorillonite K 10 clay-supported iron(III) nitrate (clayfen) under solvent-free conditions [100], This MW-expedited reaction presumably proceeds via the intermediacy of nitrosonium ions. Interestingly, no carboxylic acids are formed in the oxidation of primary alcohols. The simple solvent-free experimental procedure involves mixing of neat substrates with clayfen and a brief exposure of the reaction mixture to irradiation in a MW oven for 15-60 s. This rapid, ma-nipulatively simple, inexpensive and selective procedure avoids the use of excess solvents and toxic oxidants (Scheme 6.30) [100]. Solid state use of clayfen has afforded higher yields and the amounts used are half of that used by Laszlo et al. [17,19]. 

Musker29 carried out a systematic study of the oxidation of several cyclic 22 and acyclic 23 bis-sulfides using nitrosonium salts. Several unstable dications were characterized as sulfoxides 24. These oxidations proceed through stepwise transfer of two electrons from a bis-sulfide to the nitrosonium cation and the intermediate formation of the corresponding radical cation. Radical cations of 1,5-dithiacyclooctane 11 and 1,5-dithiacyclononane are sufficiently stable to be isolated as individual compounds (Scheme 8).50... 

Nitrosonium tetrafluorobprate was used later as oxidant for convertion of dithiolanthione 150 to dication 151.151 This technique was found to be general for oxidation of number of thiocarbonyl compounds (Scheme 56).146... 

The most important physiological nitrogen substrate of peroxidases is undoubtedly nitric oxide. In 1996, Ishiropoulos et al. [252] suggested that nitric oxide is able to interact with HRP Compounds I and II. Glover et al. [253] measured the rate constants for the reactions of NO with HRP Compounds I and II (Table 22.2) and proposed that these reactions may occur in in vivo inflammatory processes. The interaction of NO with peroxidases may proceed by two ways through the NO one-electron oxidation or the formation of peroxidase NO complexes. One-electron oxidation of nitric oxide will yield nitrosonium cation NO+ [253,254], which is extremely unstable and rapidly hydrolyzed to nitrite. On the other hand, in the presence of high concentrations of nitric oxide and the competitor ligand Cl, the formation of peroxidase NO complexes becomes more favorable. It has been shown [255]... 

Among complexes of organic compounds with N-centered electrophiles, a special position is occupied by the nitrosonium complexes. Interest in these complexes has not diminished over the years as they are intermediates in several important organic reactions, such as nitrosation of aromatic compounds (35),... 

Nitrosonium complexes 20a-d of l-R-2-methylacenaphthylenes 21a-d (Scheme 15) can be considered as complexes with two-electron ligands, as unlike complexes of other polycyclic aromatic compounds (8, 52), nitrosonium... 

To date the structure and reactivity of numerous complexes derived from aromatic compounds and nitrosonium cation have been studied (5, 56-63). However, relatively few studies are available on the nitrosonium complexes of cyclophanes (5, 57, 59, 61, 62), cf ref. (63). The interaction of [2.2]paracyclophane with nitrosonium tetrachloroaluminate was studied by H and 13C NMR spectroscopy using deuterium isotope perturbation technique (64). It was found that the resulting nitrosonium complexes containing one (25) or two NO groups (26) are involved in fast interconversion (on the NMR time scale) (Scheme 17). 

Data pertaining to affinity of organic N-bases towards nitrosonium cation are numerous 74-80), however, those for N-heteroaromatic compounds are limited 77-80). 

The nitrosonium cation can serve effectively either as an oxidant or as an electrophile towards different aromatic substrates. Thus the electron-rich polynuclear arenes suffer electron transfer with NO+BF to afford stable arene cation radicals (Bandlish and Shine, 1977 Musker et al., 1978). Other activated aromatic compounds such as phenols, anilines and indoles undergo nuclear substitution with nitrosonium species that are usually generated in situ from the treatment of nitrites with acid. It is less well known, but nonetheless experimentally established (Hunziker et al., 1971 Brownstein et al., 1984), that NO+ forms intensely coloured charge-transfer complexes with a wide variety of common arenes (30). For example, benzene, toluene,... 

Nitrous acid catalysis also takes place in the nitration of such compounds (naphthalene) that are unable to undergo nitrosation on the given conditions or whose nitrosation proceeds slower than nitration. As accepted, the nitrosonium ion is formed from HNOj in acid media. The nitrosonium ion oxidizes an aromatic substrate into a cation-radical and transforms into nitric oxide. The latter reduces nitronium cation to nitrogen dioxide that gives a a-complex with the aromatic cation-radical ... 

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