An ONIOM study on the enantioselective diels-alder reaction catalyzed by SiO 2 - immobilized chiral oxazaborolidinium cation

Omar, N.Y.M. and Zain, S.M. and Rahman, N.A. (2010) An ONIOM study on the enantioselective diels-alder reaction catalyzed by SiO 2 - immobilized chiral oxazaborolidinium cation. Journal of Molecular Catalysis A: Chemical, 333 (1-2). pp. 145-157. ISSN 13811169

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Abstract

The mechanism and enantioselectivity of the Diels-Alder reaction between 2-methyl-1,3-butadiene and 2,3-dimethyl-1,4-benzoquinone catalyzed by SiO 2-supported chiral cationic oxazaborolidinium catalyst were investigated by the hybrid ONIOM(B3LYP/6-31G(d):UFF) method. The amorphous silica bulk was obtained by classical molecular dynamics using the melt-quench method and the heterogeneous surface was created by cleaving the bulk structure. The resultant amorphous silica surface was found to closely resemble silicas thermally treated at 673 K. The organocatalytic Diels-Alder reaction on the silica surface was observed to proceed via a concerted but highly asynchronous mechanism. The preferred transition state was found to correspond to an endo arrangement of the diene and the catalyst-coordinated benzoquinone, and the enantioselectivity was calculated to be 86.5% at 298 K. The mechanism and enantioselectivity of the studied reaction were generally comparable to those observed for the homogeneous catalyst. © 2010 Elsevier B.V.

Item Type: Article
Additional Information: Department of Chemistry, Faculty of Science Building, University of Malaya, 50603 Kuala Lumpur, MALAYSIA
Uncontrolled Keywords: Asynchronous concerted mechanism, Density functional theory, Enantioselective Diels-Alder reaction, Heterogeneous catalysis, ONIOM, Concerted mechanism, Density functionals, Enantioselective Diels-Alder reactions, Butadiene, Catalysis, Catalysts, Coordination reactions, Enantioselectivity, Molecular dynamics, Olefins, Reaction kinetics, Silica, Surface reactions
Subjects: Q Science > QD Chemistry
Divisions: Faculty of Science > Dept of Chemistry
Depositing User: Miss Malisa Diana
Date Deposited: 08 May 2013 01:43
Last Modified: 08 May 2013 01:43
URI: http://eprints.um.edu.my/id/eprint/6044

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