Hydroxamic Acids and Oximes

Hydroxamic acids and oximes have relatively low p.fifa-values, and the nucleophilicity is enhanced due to the cr-effect. It is thus anticipated that micellization of these functions should produce highly nucleophilic systems. The typical nucleophilic rate constants for the reaction with PNPA are summarized in Table 3. It is seen that the rate constants in the micellar and Table 3... 

The metallacrown analogy is a powerful synthetic methodology for the design and preparation of moderate-valence multinuclear complexes from hydroxamic acid and oxime ligands in straightforward high-yield syntheses. ... 

The general approach to 0-arylation of hydroxylamines involves N-protection followed by O-arylation. Activated aryl halides and heteroaryl halides easily alkylate oxime salts (equation 25), N-aUcyl hydroxamic acids and N-hydroxysuccinimide . N-Hydroxyph-thalimide can be also 0-phenylated through a reaction with diphenyliodonium salt, although in lower yield . ... 

Use of oximes, hydroxamic acids and reiated species as reagents in inorganic anaiyticai chemistry ... 

V. A VERY BRIEF REVIEW OF OXIMES, HYDROXAMIC ACIDS AND... 

Oximes, hydroxamic acids and related species are often used as reagents in inorganic analytical chemistry for precipitation, gravimetric and volumetric determinations as well as for preconcentration, extraction, derivatizations and subsequent determination of analyte using instrumental techniques. A brief review of analytical chemistry in general and of these species in particular follows. 

It is in the realm of detoxification that the hydroxylamines/oximes/hydroxamic acids and their conjugate bases are of direct use, since a number of these compounds have been found to be especially reactive in the destruction of toxins. The fundamental reasons underlying such enhanced reactivity is an important part of this chapter. 

Seifier, S., P. M. Gallup, S. Michaels and E. Meilman Analysis of hydroxamic acids and hydrazides preparation and properties of dinitrophenyl derivatives of hydroxamic acids, oximes, hydrazides and hydrazones. J. Biol. Chem. 235, 2613 (1960). 

Various reduced forms of nitrogen, including amines, amides, N-alkylhydroxylamines, oximes, hydroxamic acids and aromatic nitro compounds, serve as substrates for nitrite, but not for nitrate, formation by various individual organisms (Doxtader and Alexander, 1966). Nitrite yields varied from a few to 190 p.p.m. Cell extracts of a Fusarium were able to convert an oxime into nitrite. 

A positive reaction is obtained, however, with a series of nonphenolic compounds aromatic amines, ends or hydroxymethylene compounds, tautomeric jS-diketones, j -ketoesters, derivatives of malonic acid esters or of cyanoacetate with a negative substituent at the -- CH2 group, some isonitrites, hydroxylamine derivatives, oximes, hydroxamic acids, and certain derivatives of sulfur. 

U-Alkylation. Dimethyl sulfate is a powerful alkylating agent and has been used for the methylation of almost every imaginable nucleophile over the years. The variety of oxygen nucleophiles include carboxylic acids, alcohols, phenols, lactams, oximes, pyridine A-oxides, hydroxylamines, hydroxamic acids, and hydroperoxides. ... 

Hydroxylamine can act as either a N-nucleophile or O-nucleophile, depending on which of the reactive centers is protected. For all reactions Ph-Pybox has been used as ligand, and moderate to high levels of selectivity have been achieved. Hydroxamic acid derivatives and oximes have also been probed as O-nucleophiles [63]. 

Some intrinsic features of hydroxyiamines, oximes and hydroxamic acids ... 

The structural link between hydroxylamines (1), oximes (2) and hydroxamic acids (3) is the N—OH group ... 

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