Nitroso hydrogenation

Nitroso compounds are formed selectively via the oxidation of a primary aromatic amine with Caro s acid [7722-86-3] (H2SO ) or Oxone (Du Pont trademark) monopersulfate compound (2KHSO KHSO K SO aniline black [13007-86-8] is obtained if the oxidation is carried out with salts of persulfiiric acid (31). Oxidation of aromatic amines to nitro compounds can be carried out with peroxytrifluoroacetic acid (32). Hydrogen peroxide with acetonitrile converts aniline in a methanol solution to azoxybenzene [495-48-7] (33), perborate in glacial acetic acid yields azobenzene [103-33-3] (34). 

In catalytic hydrogenation, a compound is reduced with molecular hydrogen in the presence of a catalyst. This reaction has found appHcations in many areas of chemistry including the preparation of amines. Nitro, nitroso, hydroxylamino, azoxy, azo, and hydrazo compounds can all be reduced to amines by catalytic hydrogenation under the right conditions. Nitriles, amides, thioamides, and oximes can also be hydrogenated to give amines (1). Some examples of these reactions foUow ... 

The N,]S -dialkyl-/)-PDAs are manufactured by reductively alkylating -PDA with ketones. Alternatively, these compounds can be prepared from the ketone and -lutroaruline with catalytic hydrogenation. The /V-alkyl-/V-aryl- -PDAs are made by reductively alkylating -nitro-, -nitroso-, or /)-aminodipheny1 amine with ketones. The AijAT-dialkyl- PDAs are made by condensing various anilines with hydroquinone in the presence of an acid catalyst (see Amines-aromatic,phenylenediamines). 

Nitroso compounds are oxidized to nitro compounds by hydrogen peroxide and dinitragen tetroxide [S2] (equation 74)... 

Nitrated fluoro compounds are synthesized by electrophilic (NOz+), radical (NO2 ), or nucleophilic (NO2-) methods Indirect nitration routes can suppress the side reactions associated with severe reaction conditions and some nitration reagents Novel fluoronitro compounds, unobtainable by direct nitration, can also be pre pared For example, the nitration of (2-fluoro-2,2-dinitroethoxy)acetaldoxime followed by oxidation of the nitroso intermediate with hydrogen peroxide yields 2-fluoro-2,2-dinitioethyl 2,2-dinitroethyl ether [f] (equation 1)... 

Nitrosodimethylaniline.—It is a peculiarity of the tertiary aromatic amines, which distinguish them fiom the corresponding aliphatic compounds, that they arc capable of reacting with nitrous acid. Here the nitroso-group replaces hydrogen in the para-position to the dimethylamino-group. 

This structure rationalizes (a) the formation of mono- and, under more vigorous conditions, tetra-acetyl derivatives, (b) the methyla-tion to a dimethyl derivative still containing two active hydrogens, (c) the pyrolysis back to monomeric indole, (d) the formation of a benzylidene derivative containing the Ph CH=N— Ar ehromophore, (e) the failure to form a simple nitroso derivative, (f) the Zn/AcOH reduction of the dimethyl trimer to base C18H20N2, shown to be identical with the dihydro derivative of (26). 

Upon the irradiation the nitrous acid ester 1 decomposes to give nitrous oxide (NO) and an alkoxy radical species 3. The latter further reacts by an intramolecular hydrogen abstraction via a cyclic, six-membered transition state 4 to give an intermediate carbon radical species 5, which then reacts with the nitrous oxide to yield the 3-nitroso alcohol 2 ... 

Condensation of ethyl acetoacetate with phenyl hydrazine gives the pyrazolone, 58. Methylation by means of methyl iodide affords the prototype of this series, antipyrine (59). Reaction of that compound with nitrous acid gives the product of substitution at the only available position, the nitroso derivative (60) reduction affords another antiinflammatory agent, aminopyrine (61). Reductive alkylation of 61 with acetone in the presence of hydrogen and platinum gives isopyrine (62). Acylation of 61 with the acid chloride from nicotinic acid affords nifenazone (63). Acylation of 61 with 2-chloropropionyl chloride gives the amide, 64 displacement of the halogen with dimethylamine leads to aminopropylon (65). ... 

Finally, a mesoionic sydnone, molsidomine (88), is active as an anti anginal agent. Its synthesis starts by reacting 1-aminomorpholine with formaldehyde and hydrogen cyanide to give 86. Nitrosation gives the N-nitroso analogue (86) which... 

Mojjo 1-4641. It does not form a crystalline hydrochloride or nitroso-chloride. Zelinsky assumes that a-pinene first absorbs hydrogen, with the formation of hydropinene, and that isopinene results from the latter, according to the following formulae —... 

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... 

Aromatic nitro compounds are hydrogenated very easily aliphatic nitro compounds considerably more slowly. Hydrogenations have been carried out successfully under a wide range of conditions including vapor phase (S9). Usually the goal of reduction is the amine, but at times the reduction is arrested at the intermediate hydroxylamine or oxime stage nitroso compounds never accumulate, although their transient presence may appreciably influence the course of reaction. In practice, nitro compounds often contain other reducible functions that are to be either maintained or reduced as well. 

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