Issue 37, 2013

Major mechanistic differences between the reactions of hydroxylamine with phosphate di- and tri-esters

Abstract

Hydroxylamine reacts as an oxygen nucleophile, most likely via its ammonia oxide tautomer, towards both phosphate di- and triesters of 2-hydroxypyridine. But the reactions are very different. The product of the two-step reaction with the triester TPP is trapped by the NH2OH present in solution to generate diimide, identified from its expected disproportionation and trapping products. The reaction with H3N+–O shows general base catalysis, which calculations show is involved in the breakdown of the phosphorane addition-intermediate of a two-step reaction. The reactivity of the diester anion DPP is controlled by its more basic pyridyl N. Hydroxylamine reacts preferentially with the substrate zwitterion DPP± to displace first one then a second 2-pyridone, in concerted SN2(P) reactions, forming O-phosphorylated products which are readily hydrolysed to inorganic phosphate. The suggested mechanisms are tested and supported by extensive theoretical calculations.

Graphical abstract: Major mechanistic differences between the reactions of hydroxylamine with phosphate di- and tri-esters

Supplementary files

Article information

Article type
Paper
Submitted
09 5 2013
Accepted
16 7 2013
First published
17 7 2013

Org. Biomol. Chem., 2013,11, 6272-6284

Major mechanistic differences between the reactions of hydroxylamine with phosphate di- and tri-esters

M. Medeiros, E. H. Wanderlind, J. R. Mora, R. Moreira, A. J. Kirby and F. Nome, Org. Biomol. Chem., 2013, 11, 6272 DOI: 10.1039/C3OB40988K

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