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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
1

Palladium-Imidazolium Carbene Catalyzed Heck Coupling Reactions and Synthesis of a Novel Class of Fluoroanthracenylmethyl PTC Catalysts

Zhang, Jiuqing 11 November 2005 (has links)
Palladium catalyzed Heck coupling with aryl and alkenyl halides has become a powerful means of carbon-carbon bond formation. This standard synthetic method has been developed to a high level of utility using various catalysts, conditions and substrates. Yet significant drawbacks remain, including poor reactivity, the need for high temperatures and base, limited substrate generality, and selectivity. Mixed products often suffer from olefin migration following insertion. N-Heterocyclic carbenes (NHC) have proven to be electron-rich donors which provide higher stability and reactivity than phosphines. In a previous paper reported by our research group the imidazolium-palladium carbene has proven to be highly efficient for the Suzuki-Miyaura cross couplings. The most active bis-2,6- diisopropylphenyl dihydroimidazolium chloride ligand 1 in that series together with palladium acetate were employed as the catalyst, to efficiently catalyze the Heck coupling of aryl diazonium ions with olefins with useful yields at room temperature. Added base is not needed either to form the carbene catalyst or for alkene product formation. Phase-Transfer Catalysis (PTC) is a very useful approach and has been widely used in synthetic organic chemistry. A novel class of fluoroanthracenylmethyl PTC catalysts were synthesized and explored for asymmetric glycolate and glycine alkylation. Phosphorous pentoxide was used for the challenging electron-deficient electrophilic aromatic substitution step. These new catalysts proved to have high selectivities for glycine alkylation under mild conditions.

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