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Spillane, WJ,Thea, S,Cevasco, G,Hynes, MJ,McCaw, CJA,Maguire, NP
2011
January
Organic & Biomolecular Chemistry
Mechanisms of hydrolysis of phenyl- and benzyl 4-nitrophenyl-sulfamate esters
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Optional Fields
CARBONIC-ANHYDRASE INHIBITORS STEROID SULFATASE INHIBITORS TRANSITION-STATE STRUCTURES BASE-CATALYZED-HYDROLYSIS SULFAMATE ESTERS WATER ACID AMINOLYSIS AMINES DERIVATIVES
9
523
530
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 S(N)2(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 >= similar to 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=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-=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.
DOI 10.1039/c0ob00362j
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