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Combined Experimental and Theoretical Study of the Mechanism and Enantioselectivity of Palladium-Catalyzed Intermolecular Heck Coupling
Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Kemiska sektionen, Institutionen för biokemi och organisk kemi, Organisk kemi I.
Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Kemiska sektionen, Institutionen för biokemi och organisk kemi, Organisk kemi I.
2008 (engelsk)Inngår i: Journal of the American Chemical Society, ISSN 0002-7863, E-ISSN 1520-5126, Vol. 130, nr 31, s. 10414-10421Artikkel i tidsskrift (Fagfellevurdert) Published
Abstract [en]

The asymmetric Heck reaction using P,N-ligands has been studied by a combination of theoretical and experimental methods. The reaction follows Halpern-style selectivity, that is, the major isomer is produced from the least favored form of the pre-insertion intermediate. The initially formed Ph-Pd(P,N) species prefers a geometry with the phenyl trans to N. However, the alternative form, with Ph trans to P, is much less stable but much more reactive. In the preferred transition state, the phenyl moiety is trans to P, but significant electron density has been transferred to the alkene carbon trans to N. The steric interactions in this transition state fully account for the enantioselectivity observed with the ligands studied. The calculations also predict relative reactivity and nonlinear mixing effects for the investigated ligands, these predictions are fully validated by experimental testing. Finally, the low conversion observed with some catalysts was found to be caused by inactivation due to weak binding of the ligand to Pd(0). Adding monodentate PPh3 alleviated the precipitation problem without deteriorating the enantioselectivity and led to one of the most effective catalytic systems to date.

sted, utgiver, år, opplag, sider
2008. Vol. 130, nr 31, s. 10414-10421
HSV kategori
Identifikatorer
URN: urn:nbn:se:uu:diva-17847DOI: 10.1021/ja802991yISI: 000258080600064OAI: oai:DiVA.org:uu-17847DiVA, id: diva2:45618
Tilgjengelig fra: 2008-09-05 Laget: 2008-09-05 Sist oppdatert: 2017-12-08bibliografisk kontrollert
Inngår i avhandling
1. Synthesis and Evaluation of N,P-Chelating Ligands in Asymmetric Transition-Metal-Catalyzed Reactions: Ir-Catalyzed Asymmetric Hydrogenation and Pd-Catalyzed Asymmetric Intermolecular Heck Reaction
Åpne denne publikasjonen i ny fane eller vindu >>Synthesis and Evaluation of N,P-Chelating Ligands in Asymmetric Transition-Metal-Catalyzed Reactions: Ir-Catalyzed Asymmetric Hydrogenation and Pd-Catalyzed Asymmetric Intermolecular Heck Reaction
2009 (engelsk)Doktoravhandling, med artikler (Annet vitenskapelig)
Abstract [en]

This thesis describes synthesis of new chiral N,P ligands and their evaluation in two types of asymmetric transition-metal catalyzed reactions.

The first part of the thesis describes studies in iridium-catalyzed asymmetric hydrogenation. A new class of chiral N,P ligands, imidazole-phosphines, was synthesized and evaluated in the Ir-catalyzed asymmetric hydrogenation of olefins (Paper I). The new ligands proved to be highly efficient and enantioselective in the reaction. Because the substrate scope of Ir-catalyzed asymmetric hydrogenation is still limited to certain types of test substrates, new substrate classes with importance in medicinal and materials chemistry were investigated. Vinyl fluorides were efficiently hydrogenated to fluorine-containing chiral centers by the iridium catalysts with imidazole-phosphine ligands (Paper I). To obtain CF3-bearing chiral centers, we hydrogenated CF3-substituted olefins (Paper II). Ir-catalyzed asymmetric  hydrogenation was highly enantioselective for the functionalized CF3-substituted olefins and the resulting chiral products can be valuable in design of materials such as LCD screens. Ir-catalyzed asymmetric hydrogenation was also evaluated as a route to diarylmethine chiral centers (Paper III). A wide range of new chiral compounds possessing a diarylmethine chiral center was obtained.

The second part of the thesis deals with asymmetric intermolecular Heck reaction utilizing N,P ligands. The N,P ligand class of thiazole-phosphines was evaluated in the Heck reaction (Paper IV) and gave high enantioselectivity. Further, the intermolecular Heck reaction was examined using computational and experimental studies (Paper V). This study led to a better understanding of the enantioselectivity in the reaction.

sted, utgiver, år, opplag, sider
Uppsala: Acta Universitatis Upsaliensis, 2009. s. 74
Serie
Digital Comprehensive Summaries of Uppsala Dissertations from the Faculty of Science and Technology, ISSN 1651-6214 ; 681
Emneord
Asymmetric hydrogenation, Heck reaction, N, P ligand, Iridium, Palladium, Asymmetric catalysis, Alkenes, Fluorine, Diarylmethine stereocenters
HSV kategori
Forskningsprogram
organisk kemi
Identifikatorer
urn:nbn:se:uu:diva-108940 (URN)978-91-554-7632-8 (ISBN)
Disputas
2009-11-26, sal B41, BMC, Husargatan 3, Uppsala, 10:15 (engelsk)
Opponent
Veileder
Tilgjengelig fra: 2009-11-05 Laget: 2009-10-05 Sist oppdatert: 2009-11-05bibliografisk kontrollert

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