Nitroso compounds carbonylation

Oxaziranes are rapidly decomposed by the further action of peracids. As shpwn by Emmons and Krimm the oxazirane is converted into a carbonyl compound and a nitroso compound dimer. The reaction can be formulated via an oxazirane A -oxide intermediate [Eq. (30)]. 

Reductive alkylations have been carried out successfully with compounds that are not carbonyls or amines, but which are transformed during the hydrogenation to suitable functions. Azides, azo, hydrazo, nitro and nitroso compounds, oximes, pyridines, and hydroxylamines serve as amines phenols, acetals, ketals, or hydrazones serve as carbonyls 6,7,8,9,12,17,24,41,42,58). Alkylations using masked functions have been successful at times when use of unmasked functions have failed (2). In a synthesis leading to methoxatin, a key... 

Acyl nitroso compounds (3, Scheme 7.2) contain a nitroso group (-N=0) directly attached to a carbonyl carbon. Oxidation of an N-acyl hydroxylamine derivative provides the most direct method for the preparation of acyl C-nitroso compounds [10]. Treatment of hydroxamic acids, N-hydroxy carbamates or N-hydroxyureas with sodium periodate or tetra-alkyl ammonium periodate salts results in the formation of the corresponding acyl nitroso species (Scheme 7.2) [11-14]. Other oxidants including the Dess-Martin periodinane and both ruthenium (II) and iridium (I) based species efficiently convert N-acyl hydroxylamines to the corresponding acyl nitroso compounds [15-18]. The Swern oxidation also provides a useful alternative procedure for the oxidative preparation of acyl nitroso species [19]. Horseradish peroxidase (HRP) catalyzed oxidation of N-hydroxyurea with hydrogen peroxide forms an acyl nitroso species, which can be trapped with 1, 3-cyclohexanone, giving evidence of the formation of these species with enzymatic oxidants [20]. 

Primary and secondary nitroso compounds tautomerize to isonitroso compounds - oximes of aldehydes and ketones, respectively. Their reductions are dealt with in the sections on derivatives of carbonyl compounds (pp. 106,132). 

Types of compounds are arranged according to the following system hydrocarbons and basic heterocycles hydroxy compounds and their ethers mercapto compounds, sulfides, disulfides, sulfoxides and sulfones, sulfenic, sulfinic and sulfonic acids and their derivatives amines, hydroxylamines, hydrazines, hydrazo and azo compounds carbonyl compounds and their functional derivatives carboxylic acids and their functional derivatives and organometallics. In each chapter, halogen, nitroso, nitro, diazo and azido compounds follow the parent compounds as their substitution derivatives. More detail is indicated in the table of contents. In polyfunctional derivatives reduction of a particular function is mentioned in the place of the highest functionality. Reduction of acrylic acid, for example, is described in the chapter on acids rather than functionalized ethylene, and reduction of ethyl acetoacetate is discussed in the chapter on esters rather than in the chapter on ketones. 

Archer, M. C. Tannenbaum, S. R. Wishnok, J. S. Nitro-samine formation in the presence of carbonyl compounds. In Walker, E. A. Bogovski, P. Griciute, L., Eds. "Environmental N-Nitroso Compounds. Analysis and Formation" lARC Scientific Publication No. 14 International Agency for Research on Cancer Lyon, France, 1976 pp. 141-145. 

The versatility of these [4+2] heterocyclization reactions is a consequence of the wide range of ene and diene components which can be used. In addition to alkenes and alkynes functioning as ene components, a variety of heterodienophiles is available such as electron-deficient imines (e.g. equation 89), nitriles e.g. equation 90), electrophilic carbonyl compounds (e.g. equation 91), thiocarbonyl compounds (e.g. equation 92), singlet oxygen (e.g. equation 93), nitroso compounds (e.g. equation 94), sulfenylsulfonamides (e.g. equation 95) and azo compounds (e.g. equation 96). Many of these reactions proceed with excellent regioselectivity and stereoselectivity, probably because in many instances they involve... 

Various polycyclic aromatic hydrocarbons, carbonyl arenas, polycyclic nitro-aromatics, aza arenes, N-nitroso compounds, and other carcinogens have been detected in ambient air (Hughes et al, 1980 Kneip et al, 1983 Spiegelhalder and Preussman, 1983). Diesel exhaust particles... 

The nitrosation of aliphatic carbon atoms, particularly of carbon atoms activated by adjacent carbonyl, carboxyl, nitrile, or nitro groups, has been reviewed in great detail [2]. Judging from this review, with few exceptions, nitrosation of active methylene compounds leads to the formation of oximes (unfortunately termed isonitroso compounds in the older literature). The few exceptional cases cited in which true nitroso compounds (or their dimers) were formed involved tertiary carbon atoms in which no hydrogen atoms were available to permit tautomerism to the oxime or involved a reaction which was carried out under neither acidic nor basic conditions. 

Insertion by nitrenes 2-55 Carbonylation of amines or nitro or nitroso compounds... 

In a reaction related to azide carbonylation, aromatic nitroso compounds also give isocyanates (equation 94). [Rh2Cl2(CO)4] (96), [RhCl(CO)2py], [RhCl(CO)(PPh3)2] (71) and [RhCl(CO)-(P(OPh)3 2] all catalyzed the reaction. Deoxygenation of the nitrosobenzene derivative was the rate determining step.448 Nitrosomethane can be similarly carbonylated.449-451... 

The complexes [IrCl(CO)L2] (L = PPh3, P(OPh), both catalyze the carbonylation of aryl nitroso compounds to give isocyanates (equation 94).448... 

Chromium-based reagent systems, for pinacol coupling, 11, 63 Chromium carbenes, in ene-yne metathesis, 11, 272 Chromium carbonyl compounds with bridging hydrides, 5, 206 computational studies and spectroscopy, 5, 203 experimentally determined structures, 5, 204 nitro and nitroso compounds, 5, 205 silatropic migrations, 5, 249 with very weakly bonded ligands, 5, 205 Chromium carbonyl hydrides, preparation and characteristics,... 

The nitroso compound could be directly observed in the reduction of t-nitro-butane at potentials less negative than -1.0 V (SCE) for primary and secondary nitroalkanes, the isolation of carbonyl compounds from the reduction constitutes indirect evidence ... 

In 1965, Neumann and Kuhlein1213 1366 reduced aliphatic halogens, and carbonyl, nitro and nitroso compounds, and Et3SnCl as well, by tributylplumbane at 0°C and 20 °C. A higher temperature was found unacceptable due to the decomposition of Bu3PbH. 

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... 

The nitroso compound is unstable because it can tautomerize with the transfer of a proton from carbon to the oxygen of the nitroso group. This process is exactly like enolization but uses an N=0 instead of a C-O group. It gives a more familiar functional group from Chapter 14, the oxime, as the stable enol . The second structure shows how the oxime s O-H can form an intramolecular hydrogen bond with the ketone carbonyl group. Hydrolysis of the oxime reveals the second ketone. 

A nitroso compound is analogous to a carbonyl compound. If there are hydrogens a to the nitroso group, enolization similar to that observed for carbonyl compounds can occur, leading to formation of an oxime. If no hydrogens are adjacent to the nitroso group, enolization to the oxime can t occur, and the nitroso compound is stable. 

Photohomolysis of the weak N-0 bond of a nitrite ester A forms a pair of radicals B and NO. The oxy radical B abstracts a hydrogen atom from a nearby carbon and the resulting radical C and NO couples to give a nitroso compound D. Tautomerism of the nitroso product D followed by treatment with nitrous acid converts this to the carbonyl group (Scheme 2.41). 

The methylene carbon atom in a condensed 4-thiazolidinone flanked by a sulfur atom and a carbonyl group possesses enhanced nucleophilic activity and attacks an electrophilic center with ease. If the structure permits, the reaction product loses a molecule of water, and an unsaturated derivative is formed. The reaction is carried out in the presence of a base which abstracts a methylene proton. It is the anion thus formed that attacks the electrophilic center. Generally, the anion condenses with aromatic aldehydes, nitroso compounds, aryidiazonium salts, and ethyl orthoformate, as well as undergoing Vilsmeier-Haack and Mannich reactions. 

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