Hydroxylamine, tris reaction with acid chlorides

Hydroxylamines usually react with acid chlorides to give mixtures of N-, O- and poly-acylated products. In contrast reaction of tris(trimethylsilyl)hydroxylamine (65) with aliphatic acid chlorides leads selectively under /V-monoacylation to the corresponding hydroxamic acids (66 equation 26). While di-phenylphosphinic chloride (68) is attacked by the oxygen of hydroxylamine to yield 0-(diphenylphos-phinyl)hydroxylamine (67 Scheme 13), A -(diphenylphosphinyl)hydroxylamine (69) can be obtained by treatment of diphenylphosphinic chloride with 0-trimethylsilylhydroxylamine followed by removal of the silyl blocking group (Scheme 13). 0-Acylation of arylhydroxylamines can be achieved with acyl cyanides. ... 

Nucleophilic Reactions. M,C)-Bis(trimethylsilyl)hydroxyl-amine is a protected, lipophilic form of hydroxylamine. It reacts with a variety of electrophiles predominantly by attack on the nitrogen nucleophilic center. Reaction with acid chlorides (1 equiv) in the presence of triethylamine gives M<9-bis(trimethylsilyl)-hydroxamic acids by iV-acylation. A related reagent, tris(tri-methylsilyl)hydroxylamine, gives the same product in high yields, also by iV-acylation. Hydrolysis gives the free hydroxamic acids, whereas thermal fragmentation affords isocyanates (eq 1). ... 

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