Oxidation of hydroxylamines

Because nitroso compounds cannot be prepared by the reduction of nitro compounds, the oxidation of hydroxylamines is often the best way for their preparation. Nitroso compounds are obtained by treatment of hydroxylamines with silver oxide [373], silver carbonate [37S], sodium dichromate [645], potassium dichromate [657], manganese dioxide [ 76], and diethyl azodicarboxylate [978] (equation 487). 

N-disubstituted hydroxylamines are converted into free-radical ni-troxyls by silver oxide in ether in the presence of anhydrous sodium sulfate (equation 488) [374.  

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Oxidation of hydroxylamine A, A -disulfonate with permanganate or Pb02 yields the intriguing... 

In fact the extremely rapid reaction of NOH with hydroperoxides combined with the ready oxidation of hydroxylamines to nitroxides during storage even in the solid state makes unlikely the detection of >N0H from hindered amines in photo-oxidizing polymer. 

In electrochemical oxidation of l-hydroxy-3-imidazoline-3-oxides containing one to four H atoms at a-C, one observes in ESR-spectra not only triplet splitting of the nucleus 14N of the nitroxyl group (a v 15-16 G) but also splitting of the neighboring protons (a// 18-20 G), with multiplets corresponding to their number (from doublet to quintet) (101). Unlike spatially hindered hydroxylamines which show reversibility in electrochemical oxidation, hydroxylamines with H at a-C are oxidized irreversibly. Oxidation of hydroxylamines with nitroxyl radical proceeds easily and with quantitative yields (102). In the oxidation of asymmetric polylluorinated hydroxylamines with Mn02, isomeric polyfluorinated nitrones have been obtained (103). 

Nitro sugars can also be prepared by oxidation of hydroxylamines. This strategy was used in 1999 by Nicolau et al. for the preparation of nitro sugar 9, a component of the natural occurring antibiotic everninomicin,11 that was obtained by ozonolysis of compound 8 followed by sequential treatment of the resulting compound with TFA and triphenylphosphine (Scheme 4). 

An alternative strategy preventing fnrther oxidation of hydroxylamines is based on concomitant O-protection of the hydroxyamino gronp. Reaction of primary amines with benzoyl peroxide affords O-benzoyl hydroxylamines of type 139 (equation 92) that can be deprotected under mildly basic conditions. The oxidation is compatible with a number of functionalities and does not interfere with other functionalities snch as an isolated double bond in the molecule of amine. This reaction is versatile and a number of hydroxylamines has been prepared in this way, although yields are only moderate in most cases . Oxidation of secondary amines with benzoyl peroxide is also possible and usually proceeds in better yields. 

In the oxidation of hydroxylamine by silver salts and mercurous salts, the nature of the reaction product apparently depends upon the extent to which catalysis participates in the total reaction. This is illustrated by some results obtained with mercurous nitrate as oxidizing agent. The reaction is strongly catalyzed by colloidal silver, and is likewise catalyzed by mercury. The reaction of 0.005 M mercurous nitrate with 0.04 M hydroxylamine at pH 4.85 proceeds rapidly without induction period. The mercury formed collects at the bottom of the vessel in the form of globules when no protective colloid is present, so the surface available for catalysis is small. Under these conditions the yield is largely nitrous oxide. Addition of colloidal silver accelerates the reaction and increases the yield of nitrogen. Some data are given in Table III. 

Oxidation of Hydroxylamine by Mercurous Nitrate at 20° 0.07% Carey Lea Dextrine Ag Sol Used Total Volume BOMl. 

A reactive intermediate may be responsible for the copper catalysis of the hydroxylamine reaction. The intermediate formed in the silver-catalyzed reaction, if it has any real existence, is not further oxidized but breaks down into nitrogen and water. Oxidation of hydroxylamine by cupric ion, on the other hand, yields predominately nitrous oxide. The intermediate formed by the removal of a single electron from the hydroxylamine in this reaction must be further oxidized to yield the final product. Such an intermediate may react readily with silver ions in solution. 

SCHEME 155. Oxidation of hydroxylamines to nitrones and a secondary amine to an imine employing Jacobsen s catalyst... 

A very common method of preparing nitroso compounds involves the oxidation of hydroxylamines with one of a large variety of oxidizing agents. The starting hydroxylamines are frequently prepared by reduction of readily... 

Oxidation of hydroxylamines 9-24 Oxidation of primary amines 9-48 Reduction of nitro compounds... 

This enzyme system catalyzes the oxidation of various nitrogen-, sulfur -, and phosphorus-containing compounds, which tend to be nucleophilic, although compounds with an anionic group are not substrates. For example, the N-oxidation of trimethylamine (Fig. 4.19) is catalyzed by this enzyme, but also the hydroxylation of secondary amines, imines, and arylamines and the oxidation of hydroxylamines and hydrazines ... 

E. C. Szarvasky found that the electrolysis of hydroxylamine was accompanied by the spontaneous transformation of hydroxylamine into ammonia. Secondary reactions always occur—the base being reduced to ammonia at the cathode and at the anode oxidized to nitrogen oxides. F. Balia found that with various electrodes the percentage current yield of NaN02 NaN03 in the electrolytic oxidation of hydroxylamine with anodes of different metals was as follows ... 

Raman, S., Ashcraft, R.W., Vial, M., Klasky, M.L. 2005. Oxidation of hydroxylamine by nitrous and nitric acids. Model development from first principle SCRF calculations. J. Phys. Chem. A, Mol. Spectrosc. Kinet. Environ. Gen. Theory 109 (38) 8526-8536. 

Ackermann, M. N. "Alkaline Hydrolysis and Oxidation of Hydroxylamine-N-Sulfonate", Ph.D. Thesis, University of California, Berkeley, 1966. 

The facile oxidation of hydroxylamine and its derivatives with periodate has led to the suggestion that the method be used as a sensitive diagnostic test for the presence of the secondary hydroxamic acid link (43). The amM of the alkane dimers at 2670 A is close to 10, i. e., about ten times the absorbancy of ferric monohydroxamate at 5100 A. It should be noted that other attempts to increase the sensitivity of hy-droxamate determination have taken advantage of the relative alkali... 

Periodate oxidation of hydroxylamine derivatives. Products, scope and... 

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