Hydroxylamines, reaction with

Reactions with Amines and Amides. Hydroxybenzaldehydes undergo the normal reactions with aUphatic and aromatic primary amines to form imines and Schiff bases reaction with hydroxylamine gives an oxime, reaction with hydrazines gives hydrazones, and reactions with semicarbazide give semicarbazones. The reaction of 4-hydroxybenzaldehyde with hydroxylamine hydrochloride is a convenient method for the preparation of 4-cyanophenol (52,53). 

In addition to their reactions with amines, Zincke salts also combine with other nitrogen nucleophiles, providing various A -substituted pyridine derivatives. Pyridine A -oxides result from the reaction with hydroxylamine, as exemplified for the conversion of Zincke salt 38 to the A -oxide 39 Reactions of Zincke salts with hydrazine, meanwhile, lead... 

The overall conversion of a 2-furyl ketal to a 6-substitutod l-hydroxy-2-pyridone (79) can be effected by electrolysis in methanol followed by reaction with hydroxylamine. A Grignard reagent can... 

The well-known reaction of a-alkyl-/3-ketoaldehydes and hydroxyl-amine has been applied to the elucidation of the structure of formyl-ation products of ketones the conclusions are, however, open to question. Some workers attempted to overcome the ambiguity of the reaction of j8-ketoaldehydes and hydroxylamine, which results in a mixture of 3- and 5-monosubstituted isoxazoles and thus considerably lowers the preparative value of the method, by using various derivatives of yS-ketoaldehydes, especially those of their enolic forms (jS-substituted vinylketones) investigated by Kochetkov et al. The use of readily available /3-chlorovinylketones (12) in the reaction with hydroxylamine represents a rather useful preparative method to synthesize monoalkylisoxazoles but again gives rise to a mixture of 3- (13) and 5-alkylisoxazoles (14). This is due to the attack... 

This presumably forms oxime, 120, on reaction with hydroxylamine that intermediate is not isolated as it cyclizes spontaneously to the isoxazole, 121. Acylation of the isoxazole with the sulfonyl chloride, 88, affords sulfisoxazole (98) after removal of the acetyl group. 

In much the same vein, acetylation of optically active cf-norgestrel by means of acetic anhydride and tosic acid gives the 17-acetate (72). Reaction with hydroxylamine hydrochloride in pyridine affords the orally active progestin dexnorgestrel acetime (73). ... 

It is much more common not to be able to isolate any intermediates at all, but this does not necessarily mean that none are formed, merely that they may be too labile or transient to permit of their isolation. Their occurrence may then often be inferred from physical, particularly spectroscopic, measurements made on the system. Thus in the formation of oximes from a number of carbonyl compounds by reaction with hydroxylamine (p. 219),... 

The intermediate acylamidine 244 functions as the three-atom component in reaction with hydroxylamine to give the [l,2,4-oxadiazol-5-yl]pyrazole 245, where the intermediate acylamidine 244 was obtained in good yield from reaction of the corresponding amide 243 with dimethylacetamide-dimethyl acetal (Scheme 37) <1999JME2218>. 

The activation of the hydrazines 397 (Scheme 68) with l,l -carbonyldiimidazole (CDI) and reaction with hydroxylamines gave the hydroxy semicarbazides 398, which could be treated with methyl chloroformate in the presence of TEA to give the first examples of 4-amino-substituted l,2,4-oxadiazolidin-3,5-diones 399 <2000HC055>. 

On reaction with hydroxylamine in the presence of appropriate bases, such derivatives of D-glucofuranurono-6,3-lactones as 25, 26, and 33 form114 N-hydroxyamides. On the other hand, when treated with hydroxylamine without base catalysis, compound 4 yields115 aWeJjt/do-D-glucurono-6,3-lactone oxime. 

Moustafa and Ahmed reported the synthesis of isoxazoles [92,93]. These compounds are related to pyrazoles except that an oxygen replaces the amine nitrogen. Scheme 49 shows the synthesis of 182 from the corresponding chal-cone 183 by reaction with hydroxylamine. Although these compounds were not tested for cytotoxicity as tubulin binders, they were found to possess antibacterial and anti-fungal activity. 

Diphenyl- -triazole is aminated by reaction with hydroxylamine-0-sulfonic acid. The I - and 2-aminotriazoles are formed in approximately equal amounts. Intramolecular amination of 1- and 2-aryltriazoles is achieved by generating a nitrene intermediate in the ortho position of the aryl substituent for example, in the thermolysis (Scheme 42) of the azide (17). ... 

Direct formation of 5,5-dihydro-5-iminothianthrene by reaction with hydroxylamine mesitylsulfonate presumably involves, first, electrophilic amination at sulfur (74TL1973). Electrophilic S-bromination (see also Section III, A, 3, b) must be presumed to initiate the conversion of thianth-rene into the sulfurane 25 by reaction with bromine in the presence of the alcohol (RfOH = l,l,l,3,3,3-hexafluoro-2-phenyl-2-propanol) (77JOC3222). 

Nowadays, the most economical way of preparing hydroxamic acid derivatives is the reaction of hydroxylamine with acid chlorides or esters . Unfortunately, the preparation of acid chlorides is often tedious. In addition, it is very difficult to avoid further acylation during the reaction with hydroxylamine. 

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