Hydroxylamines compounds

Formation of azo-type products might be troublesome. These by-products, arising from reduction of aromatic nitro compounds, usually are assumed to be derived from the coupling of intermediate nitroso and hydroxylamine compounds. The coupling problem is accentuated in reduction of nitroso compounds because of much higher concentrations. It can be alleviated by dropwise addition of the substrate to the hydrogenation and use of acidic media. 

The most advanced PDF inhibitor to emerge thus far from this collaboration is LBM-415 (12) (also called NVP PDF-713 or VIC-104959), an V-formyl-V-hydroxylamine compound still containing a proline residue at P2. The activity, PK properties, and in vivo efficacy data of (12) were presented at the 14th European Congress of Clinical Microbiology and Infectious Diseases (ECCMID) (2004) and the structure of this... 

To be noted here is that the expected product (p-chlorophenylazoxybenzene) constituted only 18% of the isolated product. We may assume that the exact composition of such product mixtures will vary considerably with the nature and position of the substituents on the aromatic rings of either the nitroso or the hydroxylamine compound. The position of the azoxy oxygen may also be influenced by these substituents. 

Two general methods may be employed in the preparation of hydroxylamine involving either the thermal dissociation of certain hydroxylamine compounds or the interaction of hydroxylamine hydrochloride suspended in an alcohol with the corresponding sodium alcoholate. The first of these methods was used both by Crismer,1 who distilled zinc chloride dihydroxylamate under reduced pressure and by Uhlenhut,2 who decomposed tertiary hydroxylamine phosphate. These procedures are extremely wasteful, owing to the instability of hydroxylamine at the temperatures required to bring about dissociation. Any hydroxylamine that is not isolated is totally lost. 

Methods for preparation of hydroxylamine derivatives have been reviewed in detail recently. Here, mainly new developments concerning the synthesis of hydroxylamines by substitution processes with heterobond formation are presented. Reduction of nitro, nitroso, oxime and nitrone derivatives as well as direct oxidation of amines leading to hydroxylamine compounds will not be considered. 

The 3-alkylamino-l,2-benzisothiazole 2-oxide (198) like pyridine A-oxides is reduced with phosphorus trichloride or thionyl chloride to the deoxy compound (199) ( = 0). The A-oxide (198) rearranges in methanol to the 3-hydroxylamine compound (200) and in formic acid to the sulfoxide... 

In alkaline and neutral solutions condensation reactions between the nitroso and hydroxylamine compounds and between the hydroxylamine and nitro compounds occur. The result is the formation of azoxy compounds which may undergo further reduction to the azo and hydrazo compounds-... 

Caprolactam Technologies Comparison. The ammoximation process simplifies a very complex part of the current CPL technology, namely the requirement of different hydroxylamine compounds for the cyclohexanone oxime synthesis. It is in Aese two steps, preparation of the hydroxylamine derivative and cyclohexanone oxime synthesis, that most of the undesired byproducts (NO SOj and ammonium sulfate) are formed. 

Another related class to sterically hindered amines are sterically hindered amine ethers. These compoimds are equally capable of forming nitroxyl radicals, as shown in Figure 20.4. Moreover, for example, the ethyl ethers decompose thermally into a hydroxylamine compound and ethene. 

ViRTANEN, A. I., and N. Saris Organic hydroxylamine compounds formed from nitrite in Torulopsis utilis. Acta Chem. Scand. 9, 337 (1955)-... 

In studies with chloroperoxidase (CPX), a peroxidative enzyme that is amazingly similar in certain properties to cytochrome P-450, we found the nitrosoarene metabolite to be the terminal product of arylamine oxidation (Fig. 6) (23, 31). CPX has been used to prepare nitrosoarene chemicals on a micro scale (17) because few chemical techniques are available for the direct conversion of arylamines to nitrosoarene compounds (28). It is probable that this enzymatic oxidation produces an intermediary hydroxylamine compound which, under the reaction conditions, is rapidly converted to the nitroso level. An apparent kinetic block in the oxidation of nitrosoarene to nitroaromatic compounds allows for the fairly selective production of the former by mild oxidants, particularly for those arylamines with electron-withdrawing substituents. 

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