Reaction with nitroso compounds

Schenk et al. have used the a-chloro nitroso compound 93 for the reaction with cyclopentene 98 in order to solve the problem with the instability of the allyl amine product formed from the reaction with nitroso compounds [56c]. The product formed, 99, rearranges to the stable nitrone hydrochloride salt 100, which is easily hydrolyzed to the hydroxylamine 101 (Eq. (23)). 

The oxidants dimethyl sulfoxide and nitroso compounds react easily with oL-bromo ketones and convert them into a-dicarbonyl compounds. The reaction with nitroso compounds is usually carried out in the presence of pyridine and proceeds through a nitrone stage. Phenacyl bromide (a-bromoacetophenone) is thus transformed first into phenacylpyridinium bromide and further, with nitrosobenzene, into a-ketoaldonitrone, which is subsequently treated with hydroxylamine to give phenylglyoxal monoxime or with phenylhydrazine to give phenylglyoxal osazone [985] (equation 411). 

The reduction of nitroaromatics in anaerobic systems has received considerable attention because of their importance as agrochemicals, munitions, textile dyes, and dye intermediates. The reaction products resulting from the reduction of nitroaromatic compounds are aromatic amines. The formation of aromatic amines occurs through a series of electron transfer reactions with nitroso compounds and hydrox-ylamines as even-electron intermediates (Equation 3.21). Typically, these intermediates are more reactive than the parent nitroaromatic compound, and do not persist to any great extent in reducing environments. 

The possibility of stabilising short-living radicals was shown for the first time using their reactions with nitroso compounds and nitrones [57, 58] ... 

The regio- and stereo-selective synthesis of inosamines and inosadiamines utilizing Diels-Alder reactions with nitroso compounds has been reviewed. 

Stannyl enol ethers undergo the aldol-type reaction with nitroso compounds to give a-aminoxy ketones or a-hydroxylamino ketones (Scheme 3-196). Regioselective and enantioselective synthesis of a-hydroxy ketones and a-amino ketones is of great synthetic significance, as these are readily converted to a variety of heterocycles. -... 

Reactions with Organic Compounds. Tetrafluoroethylene and OF2 react spontaneously to form C2F and COF2. Ethylene and OF2 may react explosively, but under controlled conditions monofluoroethane and 1,2-difluoroethane can be recovered (33). Benzene is oxidized to quinone and hydroquinone by OF2. Methanol and ethanol are oxidized at room temperature (4). Organic amines are extensively degraded by OF2 at room temperature, but primary aHphatic amines in a fluorocarbon solvent at —42°C are smoothly oxidized to the corresponding nitroso compounds (34). 

Reaction of amines with nitroso compounds (Mills)... 

Making use of the same reaction principle, disubstituted ketenes 66 have been reacted with aldehydes 80 to form p-lactones 81 [100], with diazo-compounds 82 to form 1,2-diazetidin-3-ones 83 [101] and with nitroso-compounds 84 to form 1,2-oxazetidin-3-ones 85 as precursors of a-hydroxy carboxylic acids (Fig. 42) [102],... 

Trifluoroethanol has been shown to promote the addition of nitrenes, generated by the reaction of nitroso-compounds with phosphites, to aromatic hydrocarbons, e.g. (57), (58), and (59) are formed from the reaction... 

The nitroso compounds can be formed by reaction with organic compounds present in the atmosphere and include two categories namely N-nitroso and C-nitroso compounds. 

Nitroaromatic Reduction Nitroaromatics constitute an important class of potential environmental contaminants, because of their wide use in agrochemicals, textile dyes, munitions, and other classes of industrial chemicals. Reduction of nitroaromatics produces amines, throngh a series of electron transfer reactions with nitroso and hydroxylamines as intermediates (Fig. 13.1). Compared to the parent nitroaromatic compound, all intermediates typically reduce readily (Larson and Weber 1994). 

While the condensation of amines with nitroso compounds appears to have wide applicability in the benzene series, it seems to lead to complex dye molecules in the naphthalene series. A method has been developed using a somewhat complex reaction between thionylamines and substituted hydroxylamines which does produce azo compounds derived from naphthalenes. This synthesis is of particular interest because it helped to settle the question whether true naphthylazo compounds with hydroxyl groups could exist [36]. 

Further complications of the reduction of aromatic nitro compounds are the possibility of complete reduction to aromatic amines (which may condense with nitroso compounds to give the desired azo compounds), reduction of azo compounds to the corresponding hydrazo compounds, followed by a benzidine (or semidine) rearrangement. It is clear, therefore, that the level of reducing agent used and other reaction conditions are quite critical. 

Reaction of nitroso compounds with active methylene groups to give imines [46a, b]. 

All of these substances can be reduced to benzenamine with tin and hydrochloric acid. As a result, each could be, but not necessarily is, an intermediate in the reduction of nitro compounds to amines. Formation of the bimolecular reduction products is the result of base-induced reactions between nitroso compounds and azanols or amines and possibly further reduction of the initially produced substances (see Exercise 24-18). 

During the nitration of aromatic compounds a certain amount of diazo compounds as by-products can also be formed. This for the first time was described by Weselsky as early as in 1875 [84] in the case of nitration of phenols with nitrogen dioxide and of nitration of aromatic hydrocarbons by Titov and Baryshnikova [85], Titov [39] explained the reaction as the result of reaction of nitroso compounds with NO ... 

The reaction of nitroso compounds with typical metal enolates, the nitroso aldol reaction, occurs in high yields to generate a-hydroxyamino carbonyl compounds. Exclusive iV-selectivity >99 1 is observed to give hydoroxyamino ketone in the reaction with tin enolates (Equation (70)).2... 

Aromatic and aliphatic primary amines can be oxidized to the corresponding nitro compounds by peroxy acids and by a number of other reagents. The peroxy acid oxidations probably go by way of intermediate hydroxylamines and nitroso compounds (Scheme 2). Various side reactions can therefore take place, the nature of which depends upon the structure of the starting amine and the reaction conditions. For example, aromatic amines can give azoxy compounds by reaction of nitroso compounds with hy-droxylamine intermediates aliphatic amines can give nitroso dimers or oximes formed by acid-catalyz rearrangement of the intermediate nitrosoalkanes (Scheme 3). 

Functionalization of rubbers with nitroso compounds (174) involves two reaction steps [233] formation of a hydroxylamine derivative 175 and its... 

Somewhat related are the reactions of the rhenium carbyne complex 263 with nitroso compounds (40,198). Reaction of the tetrachloroborate salt... 

By far the most important reactions of ylides are those of the Wittig type, especially those with carbonyl compounds, and they will be dealt with first other reactions of this sort are those with other C = X functions and with nitroso-compounds. Other carbanionic reactions are then considered and a final section deals with the formation of cyclic compounds from arsonium ylides. Hydrolysis has already been discussion in Section III.B. 

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