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Göteborgs universitets publikationer

Memory Effects in Palladium-Catalyzed Allylic Alkylations of 2-Cyclohexen-1-yl Acetate

Författare och institution:
Nina Svensen (-); Peter Fristrup (-); David Tanner (-); Per-Ola Norrby (Institutionen för kemi)
Publicerad i:
Adv.Synth.Catal, 349 s. 2631-2640
Artikel, refereegranskad vetenskaplig
Sammanfattning (abstract):
The objective of this work was to characterize the enantiospecificity of the allylic alkylation of enantioenriched 2-cyclohexen-1-yl acetate with the enolate ion of dimethyl malonate catalyzed by unsymmetrical palladium catalysts. The precatalysts employed were (3-allyl)PdLCl, where L is a monophosphine ligand [PPh3, PCy3, P(2-BiPh)Cy2, or P(t-Bu)3], all of which afforded enantiospecificity to some extent (5-47 %). Quantum mechanical calculations show that, theoretically, the enantiospecificity should be high due to a preference for the trans to P transition state in both formation of the 3-allyl intermediate and nucleophilic attack. However, the observed enantiospecificity is relatively low due to isomerization of the 3-allyl intermediate and/or dynamic equilibria between the catalytically active (3-allyl)PdLCl species and [(3-allyl)PdL2]+ or [(3-allyl)PdCl]2. It was also observed experimentally that increasing the bulk of the phosphine inhibits formation of the [(3-allyl)PdL2]+ complexes, significantly increasing the observed enantiospecificity for some of the ligands.
Ämne (baseras på Högskoleverkets indelning av forskningsämnen):
allylic substitution • chloride effect • enantiospecificity • memory effect • palladium • regiospecificity
Postens nummer:
Posten skapad:
2008-08-15 15:10

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