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Titolo:
TRANSITION STRUCTURE FOR THE EPOXIDATION MEDIATED BY TITANIUM(IV) PEROXIDE - A DENSITY-FUNCTIONAL STUDY
Autore:
WU YD; LAI DKW;
Indirizzi:
HONG KONG UNIV SCI & TECHNOL,DEPT CHEM KOWLOON HONG KONG
Titolo Testata:
Journal of organic chemistry
fascicolo: 3, volume: 60, anno: 1995,
pagine: 673 - 680
SICI:
0022-3263(1995)60:3<673:TSFTEM>2.0.ZU;2-Y
Fonte:
ISI
Lingua:
ENG
Soggetto:
OXYGEN ATOM TRANSFER; METAL-CATALYZED EPOXIDATIONS; ASYMMETRIC EPOXIDATION; ENANTIOSELECTIVE EPOXIDATION; SHARPLESS EPOXIDATION; ORGANOMETALLIC COMPOUNDS; PRACTICAL TOOL; COMPLEXES; MECHANISM; CHEMISTRY;
Tipo documento:
Article
Natura:
Periodico
Settore Disciplinare:
Science Citation Index Expanded
Citazioni:
71
Recensione:
Indirizzi per estratti:
Citazione:
Y.D. Wu e D.K.W. Lai, "TRANSITION STRUCTURE FOR THE EPOXIDATION MEDIATED BY TITANIUM(IV) PEROXIDE - A DENSITY-FUNCTIONAL STUDY", Journal of organic chemistry, 60(3), 1995, pp. 673-680

Abstract

The epoxidation reaction of ethylene with trihydroxytitanium hydroperoxide has been studied by the nonlocal density functional: method to model titanium catalyzed epoxidation of alkenes. Spiro and planar transition structures were optimized with the constraint of a Ti-O-O-H dihedral angle of 180 degrees. A eta(2) structure is not found in the titanium hydroperoxide reactant, but is found in the transition structure of epoxidation. The approach of ethylene is nearly anti to the breaking O-O bond. The planar structure is quite unsymmetrical and is 3.0 kcal/mol less stable than the spiro structure at the best level of calculation. The spiro preference of the transition structure is discussed based on molecular orbital theory. The monomeric mechanism of Sharplessepoxidation was also modeled. Only spiro transition structures could be located. The two C-O bonds form to similar extent in each transition structure. The allylic C-O bond is in an ''inside'' position with a dihedral angle of about 30-40 degrees with respect to the C=C double bond. Each transition structure is nearly square-planar with the open site anti to the C=C bond. The activation energy is calculated to be about 10.7 kcal/mol with the BLYP/HW3 method.

ASDD Area Sistemi Dipartimentali e Documentali, Università di Bologna, Catalogo delle riviste ed altri periodici
Documento generato il 20/09/20 alle ore 22:37:53