Lewis Base-Catalyzed Enantioselective Allylation and Aldol Addition Reactions
Su, Xiping
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https://hdl.handle.net/2142/84439
Description
Title
Lewis Base-Catalyzed Enantioselective Allylation and Aldol Addition Reactions
Author(s)
Su, Xiping
Issue Date
1999
Doctoral Committee Chair(s)
Denmark, Scott E.
Department of Study
Chemistry
Discipline
Chemistry
Degree Granting Institution
University of Illinois at Urbana-Champaign
Degree Name
Ph.D.
Degree Level
Dissertation
Keyword(s)
Chemistry, Organic
Language
eng
Abstract
A dramatic rate acceleration by phosphoramides is observed for the addition of the trichlorosilyl enolate, 1-trichlorosiloxycyclohexene, to aldehydes. Both the enantio- and diastereoselectivities of the reaction vary dramatically with the structure of phosphoramides. It is believed that the reaction proceeds through a six-membered ring closed transition state with the ionization of a chloride from the trichlorosilyl enolate with either one or two phosphoramide molecules binding to the silicon. A nonlinear effect with enantio enriched phosphoramides supports the hypothesis. Studies by X-ray crystallography of phosphoramide-Lewis acid complexes revealed detailed structural information about the binding of chiral phosphoramides to Lewis acids. Transition state models are proposed based on the conformational preference of chiral phosphoramides in binding to Lewis acids.
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