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Issue 2, 2011
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Mechanisms of hydrolysis of phenyl- and benzyl 4-nitrophenyl-sulfamate esters

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Abstract

The kinetics of hydrolysis at medium acid strength (pH interval 2–5) of a series of phenylsulfamate esters 1 have been studied and they have been found to react by an associative SN2(S) mechanism with water acting as a nucleophile attacking at sulfur, cleaving the S–O bond with simultaneous formation of a new S–O bond to the oxygen of a water molecule leading to sulfamic acid and phenol as products. In neutral to moderate alkaline solution (pH ≥ ∼ 6–9) a dissociative (E1cB) route is followed that involves i) ionization of the amino group followed by ii) unimolecular expulsion of the leaving group from the ionized ester to give N-sulfonylamine [HN[double bond, length as m-dash]SO2] as an intermediate. In more alkaline solution further ionization of the conjugate base of the ester occurs to give a dianionic species which expels the aryloxide leaving group to yield the novel N-sulfonylamine anion [N[double bond, length as m-dash]SO2]; in a final step, rapid attack of hydroxide ion or a water molecule on it leads again to sulfamic acid. A series of substituted benzyl 4-nitrophenylsulfamate esters 4 were hydrolysed in the pH range 6.4–14, giving rise to a Hammett relationship whose reaction constant is shown to be consistent with the E1cB mechanism.

Graphical abstract: Mechanisms of hydrolysis of phenyl- and benzyl 4-nitrophenyl-sulfamate esters

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Publication details

The article was received on 30 Jun 2010, accepted on 13 Sep 2010 and first published on 25 Oct 2010


Article type: Paper
DOI: 10.1039/C0OB00362J
Citation: Org. Biomol. Chem., 2011,9, 523-530
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    Mechanisms of hydrolysis of phenyl- and benzyl 4-nitrophenyl-sulfamate esters

    W. J. Spillane, S. Thea, G. Cevasco, M. J. Hynes, C. J. A. McCaw and N. P. Maguire, Org. Biomol. Chem., 2011, 9, 523
    DOI: 10.1039/C0OB00362J

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