Hydroxamic acid esters halides

Formally, they can all be viewed as derivatives of hydroxylamine, H2N—OH indeed, oximes can be prepared by the addition of hydroxylamine to aldehydes and ketones (equations 1 and 2), and hydroxamic acids by its reactions with acetyl halides and esters (equations 3 and 4). ... 

Hydroxylamines and hydrazines can be acylated on insoluble supports using the same type of acylating agent as is used for the acylation of amines [146-149]. Because of their higher nucleophilicity, hydroxylamines or hydrazines can be acylated more readily than amines, and unreactive acylating agents such as carboxylic esters can sometimes be successfully employed (Table 13.10). Polystyrene-bound O-alkyl hydroxamic acids can be N-alkylated by treatment with reactive alkyl halides and bases such as DBU (Entry 5, Table 13.10). 

The simpler examples are readily hydrolysed in aqueous solution, and therefore react with sodium hydrogen carbonate and also give the ester test they may be confirmed by applying the hydroxamic ester test (Section 9.5.3, p. 1222). Carbonyl adsorption is apparent in the infrared spectrum at about 1820 cm-1 and at about 1760cm-1. It should be noted that aromatic anhydrides and higher aliphatic anhydrides are not readily hydrolysed with water and are therefore effectively neutral (Section 9.5.3, p. 1218). The final characterisation of the acid anhydride is achieved by conversion into a crystalline carboxylic acid derivative as for add halides. 

The common methods for the S5mthesis of p-lactams are cycloaddition reactions such as the Staudinger s ketene-imine cycloadditions, ester enolate-imine cycloadditions, alkyne-nitrone cycloadditions (Kinugasa reaction), alkene-isocyanate cycloadditions, and Torii s cyclocarbonylation of allyl halides with imines. Several cyclizahon reactions of p-amino esters, p-amino acids, p-hydroxamate esters, and a-diazocarbonyls have been developed for the formation of p-lactam ring. N,N-Disubstituted a-haloamides cyclize by C3-C4 bond formation leading to the formation of P-lactam ring. 

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