O-Acylhydroxylamines

Acyl derivatives, RCO—NH—OH and HjN—O—CO—R, are named as A-hydroxy derivatives of amides and as O-acylhydroxylamines, respectively. The former may also be named as hydroxamic acids. Examples are A-hydroxyacetamide for CH3CO—NH—OH and O-acetylhydrox-ylamine for HjN—O—CO—CH3. Further substituents are denoted by prefixes with O- and/or A-locants. For example, C5H5NH—O—C2H5 would be O-ethyl-A-phenylhydroxylamine or A-ethox-ylaniline. 

N -I henylmorpholine (Amination of an Arylzinc Derivative with an O-Acylhydroxylamine). This procedure is found in Organic Syntheses.111... 

A high reactivity of HAS with diacylperoxides was observed in low-temperature oxidation of PO and yields O-acylhydroxylamines [206] ... 

N-Acylhydroxylamines s. Hydroxamic acids O-Acylhydroxylamines s. Acoxylamines Acylimines... 

Sodium cyanoborohydride-acetic acid and triethylsilane-trifluoroacetic acid have been found to be excellent reducing systems for oxime benzoates, providing a new general synthesis of O-acylhydroxylamines (Scheme 38). ... 

The anti-fungal and anti-bacterial properties of l,2-benzisothiazol-3(2ff)-ones has caused much synthetic activity to be focused upon them and two new routes have been published this year, from the O-acylhydroxylamines (297) and the sulphinylbenzamides (298). As one would expect, spirocyclic benzo-thiazolines are readily prepared from o-aminothiophenols and cyclic... 

Boche, G., F. Bosold and S. Schroder. 1988. N-Aryl-O-acylhydroxylamines preparation by O-acylation or N->0 transacylation and reaction with amines model reactions for key steps connected with the carcinogenicity of aromatic amines. Angew. Chem. Int. Ed. Engl. 27 973-974. 

Methylhydroxyurea (28, Fig. 7.5) oxidizes oxyHb to metHb and reduces metHb to deoxyHb but neither of these reactions produces HbNO, further supporting the mechanism depicted in Scheme 7.16 for the formation of NO and HbNO from the reactions of hydroxyurea and hemoglobin [115]. The O-methyl group of 27 prevents the association and further reaction of 27 with the heme iron [115]. Scheme 7.16 predicts the redox chemistry observed during the reaction of 28 with hemoglobin and the failure to detect HbNO shows the inability of 28 or any derivative radicals to transfer NO during these reactions [115]. These results indicate that nitric oxide transfer in these reactions of hydroxyurea requires an unsubstituted acylhydroxylamine (-NHOH) group. 

An analogous method was used by Endo and colleagues in a-amination of unreactive carboxylic acids. Treatment of iV-acylhydroxylamine O-carbamates 92 by KHMDS or LDA followed by [3,3]-sigmatropic rearrangement and decarboxylation provided a-amino acid analogues 93 (equation 29). 

Formation of 1,2,4-oxadiazines occurs by acid-catalyzed ring expansion of a-aziridino oximes and dioximes, and by 1,3-dipolar cycloaddition of arylcarbonitrile oxides and 2-acyl-2//-azirines (Section 6.14.10). Preparation of l,2,4-oxadiazin-5-ones can be achieved by ring closure of A-carboxymethyl and A-alkoxycarbonylmethyl amidoximes (Section 6.14.9.1.1), by the acid-catalyzed condensation of arylaldehydes with O-alkyl-A-acylhydroxylamines (Section 6.14.9.2.3.1), and by reaction of A-hydroxyureas or amidoximes with a two-carbon fragment such as an a-halo ester or an acyl halide (Section 6.14.9.2.2.1). 

The synthesis of a series of hexahydro derivatives (44 R = Ph, OPh, CH2OC6H4—Cl-p, CH2C6H4—CN-p, OCsH —SMe-o), as well as the iV-tosyl analogue, through the electrochemical reduction/dialkylation of various -acylhydroxylamines with 1,6-dibromohexane (or l-bromo-6-chlorohexane) has been reported (Equation (10)) <89JAP01221371, 89Japoi221372, 90Japo2229175>. 

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