The base-catalysed cyclisation of phenyl N-(2-hydroxybenzyl)-N-methylcarbamates is concerted

Sterba, V. and Hrabik, O. and Kavalek, J. and Mindl, J. and Williams, A. (2003) The base-catalysed cyclisation of phenyl N-(2-hydroxybenzyl)-N-methylcarbamates is concerted. Organic & Biomolecular Chemistry, 1 (2). pp. 415-421. ISSN 1477-0520. (The full text of this publication is not available from this repository)

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Abstract

The kinetics of the cyclisation in aqueous solution of phenyl-(2-hydroxybenzyl)-N-methylcarbamates to 3-methyl-3,4-dihydrobenzo[e][1,3]oxazin-2-ones and phenolate ions fit the rate law: k(obs) = k(c)/(1 + [H3O+]/K-a) The values of k(c) and pK(a) fit Bronsted equations against the pK(a)'s of the corresponding free phenols but the system does not conform to the reactivity selectivity hypothesis. The values of the Bronsted parameters beta(Y) and beta(X) vary as a function of Y and X according to the equations: beta(X) = -0.179pK(a)(HY) + 0.87 beta(Y) = -0.179pK(a)(HX) + 2.30 The magnitude and sign of the Cordes-Thornton cross-interaction coefficient p(XY) (-0.179) rule out a stepwise mechanism involving a tetrahedral intermediate and is consistent with a concerted displacement mechanism. A similar concerted mechanism is proposed for the base-catalysed cyclisation of phenyl-N-(2-hydroxyphenyl)-N-methylcarbamate esters to benzoxazol-2-ones.

Item Type: Article
Additional information: 35 ROYAL SOC CHEMISTRY 655MU
Uncontrolled keywords: ACYL GROUP TRANSFER; TRANSITION-STATE STRUCTURES; PHENOLATE ION NUCLEOPHILES; CYCLIC ANHYDRIDE FORMATION; ACETYL GROUP TRANSFER; ENZYMATIC-REACTIONS; NONPERFECT SYNCHRONIZATION; INTRAMOLECULAR REACTIONS; REACTIVITY; PRINCIPLE
Subjects: Q Science
Divisions: Faculties > Science Technology and Medical Studies > School of Physical Sciences
Depositing User: Maggie Francis
Date Deposited: 12 Sep 2008 12:00
Last Modified: 14 Jan 2010 14:42
Resource URI: http://kar.kent.ac.uk/id/eprint/11016 (The current URI for this page, for reference purposes)
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