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Titolo:
Enantioselective epoxidation of (Z)-stilbene using a chiral Mn(III)-salen complex: effect of immobilisation on MCM-41 on product selectivity
Autore:
Piaggio, P; McMorn, P; Murphy, D; Bethell, D; Page, PCB; Hancock, FE; Sly, C; Kerton, OJ; Hutchings, GJ;
Indirizzi:
Cardiff Univ, Dept Chem, Cardiff CF10 3TB, S Glam, Wales Cardiff Univ Cardiff S Glam Wales CF10 3TB ardiff CF10 3TB, S Glam, Wales Univ Liverpool, Dept Chem, Liverpool L69 3BX, Merseyside, England Univ Liverpool Liverpool Merseyside England L69 3BX , Merseyside, England Univ Loughborough, Dept Chem, Loughborough LE11 3TU, Leics, England Univ Loughborough Loughborough Leics England LE11 3TU 3TU, Leics, England Synteix, Billingham TS23 1LB, Cleveland, England Synteix Billingham Cleveland England TS23 1LB S23 1LB, Cleveland, England Robinson Bros Ltd, W Bromwich B70 0AH, W Midlands, England Robinson Bros Ltd W Bromwich W Midlands England B70 0AH Midlands, England
Titolo Testata:
JOURNAL OF THE CHEMICAL SOCIETY-PERKIN TRANSACTIONS 2
fascicolo: 10, , anno: 2000,
pagine: 2008 - 2015
SICI:
1470-1820(2000):10<2008:EEO(UA>2.0.ZU;2-K
Fonte:
ISI
Lingua:
ENG
Soggetto:
ELECTRON-SPIN-ECHO; MOLECULAR-SIEVES; CIS-OLEFINS; (SALEN)MANGANESE(III) COMPLEXES; HETEROGENEOUS AZIRIDINATION; ASYMMETRIC EPOXIDATION; TRANS-EPOXIDES; CATALYST; ZEOLITE; ALKENES;
Tipo documento:
Article
Natura:
Periodico
Settore Disciplinare:
Physical, Chemical & Earth Sciences
Citazioni:
43
Recensione:
Indirizzi per estratti:
Indirizzo: Hutchings, GJ Cardiff Univ, Dept Chem, POB 912, Cardiff CF10 3TB, S Glam, Wales Cardiff Univ POB 912 Cardiff S Glam Wales CF10 3TB am, Wales
Citazione:
P. Piaggio et al., "Enantioselective epoxidation of (Z)-stilbene using a chiral Mn(III)-salen complex: effect of immobilisation on MCM-41 on product selectivity", J CHEM S P2, (10), 2000, pp. 2008-2015

Abstract

Manganese-exchanged Al-MCM-41 modified by the chiral salen ligand [(R,R)-(-)-N,N'-bis(3,5-di-tert-butylsalicylidene)cyclohexane-1,2-diamine] has beeninvestigated as a heterogeneous catalyst for the enantioselective epoxidation of (Z)-stilbene using iodosylbenzene as oxygen donor, with particular interest in the effect of reaction conditions on the cis:trans ratio of the epoxide product. Immobilisation of the chiral Mn-salen complex in Al-MCM-41increases the cis:trans ratio of the epoxide product when compared to the non-immobilised complex under the same conditions. Increasing the level of Mn-exchange in the Al-MCM-41 increases the amount of trans-epoxide, whereasincreasing the iodosylbenzene:substrate ratio increases the amount of cis product formed. Increasing the reaction temperature also increases the amount of trans-epoxide for the homogeneous Mn-complex under the same conditions. A series of experiments is described in which the external ion-exchange sites on Al-MCM-41 are preferentially silanised, which enables the cis/trans selectivity for external and internal sites to be determined. Mn-salen immobilised on the external surface of Al-MCM-41 gives the same cis:trans ratio as that observed with the non-immobilised Mn-salen complex in solution, whereas Mn-salen immobilised within the pores gives the cis-epoxide preferentially. The enantioselection of the immobilised chiral Mn-salen complex is shown to decrease with reaction time at -10 degrees C, but the cis:trans epoxide ratio remains unchanged; whereas for the non-immobilised complex in solutionthe enantioselection is independent of reaction time. Iodobenzene, a decomposition product formed from iodosylbenzene, is found to act as a poison for the immobilised catalyst, leading to a slower reaction and lower enantioselection.

ASDD Area Sistemi Dipartimentali e Documentali, Università di Bologna, Catalogo delle riviste ed altri periodici
Documento generato il 24/09/20 alle ore 05:00:06