Nitroso ketone

If the alkoxy group at the C-6 atom in nitroso acetals (475) is absent, silyl derivatives (476) are generated instead of nitroso ketones A, and methanolysis of compounds (476) gives rise to y-hydroxy oximes (479). 

The bimolecular reduction of aliphatic nitroso compounds is complex and somewhat unreliable. With careful control of reaction conditions, a-nitroso ketones (in dimeric form) may be reduced with stannous chloride in an acidic medium at room temperature to the azoxy compounds, while dimeric a-nitroso acid derivatives may be reduced at about 50°C [10, 35, 36]. Nitrosoalkanes, on the other hand, are decomposed at room temperature to alcohols and nitrogen, and are reduced to amines at 50°-60°C. It has been postulated that only the dimeric nitroso compounds can be reduced to azoxy compounds and, in fact, that the dimer has a covalent nitrogen-nitrogen bond. Equations (31)—(34) summarize these data [10]. 

Claisen also obtained nitroso-ketones by the use of amyl nitrite in the presence of sodium ethylate C5H5.CO.CH3 + CjIIn.O.NO = CcH5.CO.CH NOH + C6H OH... 

The role of copper ion seems to be facilitating further nitration of the nitroso compound. As shown by reaction 8.24, the nitro, nitroso ketone gets converted... 

The preparation of the requisite methyl ketone 67 starts from mesityl oxide (62) and hydroxylamine hydrochloride utilizing a known protocol (98BC1808) (Scheme 15). As correctly formulated in the original paper, hydroxylamine hydrochloride does not form the oxime but affords a low yield (11%) of the conjugate adduct, 4-(hydroxyamino)-4-methylpentan-2-one (63), which in solution is predominantly present as the hemiacetal cyclotautomer, 3,3,5-trimethylisoxazolidin-5-ol (64). Oxidation of 64 with mercuric oxide in chloroform furnishes a blue solution of 4-methyl-4-nitrosopentan-2-one (65) and its dimer 66 (ratio 85 15), which was isolated as colorless crystals 67 (54%). Condensation of nitroso ketone 65 with aniline in the presence of acetic acid provides / -phenyldiazenyl-a -methyl ketone 67 as a yellow oil (49%) (Scheme 15). 

In addition, some reactions on a-nitroso ketones and 3-mcrcapto coumarin, as well as the aminoalkylation of benzotriazole with aldehydes and arylamincs, can be interpreted only on the basis of aldehyde attack on the substrate as the first reaction step. 

Cyclopropanoxyl radicals were generated by thermal and photochemical decomposition of cyclopropyl nitrites.The nitrites were prepared from cyclopropanols and nitrosyl chloride in pyridine, and they decomposed at low temperatures often below room temperature. A mixture of -bromo and jS-nitroso ketones was formed from the photolysis of pentamethylcyclo-propyl nitrite (19) in bromotrichloromethane. " ... 

Primary or secondary ) -nitroso ketones formed in this reaction rearranged to give isoxazolines, e.g. 

Unter milden Bedingungen (Aluminium-Amalgam) werden a-Nitroso-ketone zu Azoxy- und Hydrazo-Verbindungen reduziert. Wegen des entstehenden Gemischs ist der Wert dieser Reduktion gcring (Bd. X/l, S. 987 f.). 

To address the problems of slow cleavage kinetics and methionine oxidation associated with the use of photolabile support Ij (Table 1), a linker based o -methyl-6-nitroveratryl alcohol [227,228] was designed. The additional ring alkoxy groups and the a-methyl group of support 5q facilitate cleavage and lead to fewer side products that result from the photoproduct, a resin-bound nitroso ketone, compared with Ij and other conventional photolabile linkers. Support 5q has been used for the synthesis of sultams [229], which were cleaved from the resin by irradiation in 2-propanol at 365 nm. 

A new general method for the synthesis of a-nitroso-ketone acetal dimers involves the reaction of the enol ethers (29) with excess methyl nitrite, the nitrolysis reaction being catalysed by 100% H2SO4 or BF3 Et20 at —20 C... 

One of the final photolysis products, 2-nitrosoacetophenone, reacts with thiols and other groups and can cause damage to the biological systems under investigation. This complication can be avoided by the addition of thiol reagents, for instance dithiothreitol (DTT), which sequester nitroso-ketones. It is in fact possible to determine the rate of formation of photolysis products, in the presence of sufficiently high concentrations of DTT, by observation of the disappearance of the nitroso band at 740 nm (extinction coefficient 50 M cm The second order rate constant for the reaction of 2-nitrosoacetophenone with DTT at pH 7 and 21 C and ionic strength 0.18 M is 3.5 x 10 M" s . 

This synthesis of the pyrrole ring system, due to Knorr, consists in the condensation of an a-aminoketone with a 1,3-diketone or the ester of a p-keto-acid, a-Aminoketones are unstable in the free state, readily undergoing self-condensation consequently they must be prepared, by the reduction of an a-nitroso (or oximino) ketone, in the presence of the 1,3-diketone or p-ketoester, to ensure rapid interaction. 

The imides, primaiy and secondary nitro compounds, oximes and sulphon amides of Solubility Group III are weakly acidic nitrogen compounds they cannot be titrated satisfactorily with a standard alkaU nor do they exhibit the reactions characteristic of phenols. The neutral nitrogen compounds of Solubility Group VII include tertiary nitro compounds amides (simple and substituted) derivatives of aldehydes and ketones (hydrazones, semlcarb-azones, ete.) nitriles nitroso, azo, hydrazo and other Intermediate reduction products of aromatic nitro compounds. All the above nitrogen compounds, and also the sulphonamides of Solubility Group VII, respond, with few exceptions, to the same classification reactions (reduction and hydrolysis) and hence will be considered together. 

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). 

Acid Dyes. These water-soluble anionic dyes ate appHed to nylon, wool, sUk, and modified acryHcs. They ate also used to some extent for paper, leather, food, and cosmetics. The original members of this class aU had one or mote sulfonic or catboxyHc acid groups in thein molecules. This characteristic probably gave the class its name. Chemically, the acid dyes consist of azo (including preformed metal complexes), anthraquiaone, and ttiaryHnethane compounds with a few azHie, xanthene, ketone imine, nitro, nitroso, and quHiophthalone compounds. 

The more important methods of preparation of diazomethane include those from nitrosomethylurea, nitrosomcthylurethane, N-nitroso-/3-methylaminoisobutyl methyl ketone, and 1-methyl-l-nitroso-3-nitroguanidine. ... 

The reactions of A -steroids with nitrosyl fluoride parallel those of their A -isomers. Thus, 17 -acetoxyandrost-4-ene (37) is converted to the nitrimine (38), in 67 % yield and thence to the 4-ketone (39), which can be dehydrofluorinated to the A -4-ketone (40) with lithium bromide in di-methylformamide. In the corresponding 19-nor series the nitroso dimer is also formed. 

Carbons adjacent to a Z group (as defined on p. 548) can be nitrosated with nitrous acid or alkyl nitrites. The initial product is the C-nitroso compound, but these are stable only when there is no tautomerizable hydrogen. When there is, the product is the more stable oxime. The situation is analogous to that with azo compounds and hydrazones (12-7). The mechanism is similar to that in 12-7 R—H —> R + N=0 — R—N=0. The attacking species is either NO or a carrier of it. When the substrate is a simple ketone, the mechanism goes through the enol (as in halogenation 12-4) ... 

As in the Japp-Klingemann reaction, when Z is an acyl or carboxyl group (in the case of R2CH—Z), it can be cleaved. Since oximes and nitroso compounds can be reduced to primary amines, this reaction often provides a route to amino acids. As in the case of 12-4, the silyl enol ether of a ketone can be used instead of the ketone itself. Good yields of a-oximinoketones (20) can be obtained by treating ketones with fert-butyl thionitrate. ... 

Ross and Chiarello (1979) have described a method for denitrosation of nitrosamines, such as dlalkylnitrosamines e.g. N-nitrosodimetl laminer etc., and complex aryl-alkyl nitrosamines, e.g. N-nitroso-N-(l-ethylpropyl)-3,4-dimethyl-2,6-dinitroaniline. The products of nitration and amination containing nitrosamlne as a substantial impurity are treated with an aldehyde or ketone in the presence of strong acids such as hydrochloric or hydrobromic acid. Under pressurized conditions at 105-110% for cme to two hours, the nitrosamlne is destroyed. The desired product can be recovered after neutralization of the excess acid. The equation shows the denitrosation of pendimethalin ... 

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