University of Illinois Urbana-Champaign

Studies in Asymmetric Catalysis: Lewis Base Catalyzed, Enantioselective Addition of Trimethylsilyl Cyanide, Trimethylsilyltrifluoromethane, and Glycolate-Derived Silyl Ketene Acetals to Aldehydes

Chung, Won-Jin

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Description

Title
Studies in Asymmetric Catalysis: Lewis Base Catalyzed, Enantioselective Addition of Trimethylsilyl Cyanide, Trimethylsilyltrifluoromethane, and Glycolate-Derived Silyl Ketene Acetals to Aldehydes
Author(s)
Chung, Won-Jin
Issue Date
2008
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 catalytic system involving silicon tetrachloride and a chiral, Lewis basic bisphosphoramide catalyst is effective for the addition of glycolate-derived silyl ketene acetals to aldehydes. The sense of diastereoselectivty could be modulated by changing the size of the substituents on the silyl ketene acetals. In general, the trimethylsilyl ketene acetals derived from methyl glycolates with a large protecting group on alpha-oxygen provide enantiomerically enriched alpha,beta-dihydroxy esters with high syn-diastereoselectivity, whereas the tert-butyldimethylsilyl ketene acetals derived from bulky esters of alpha-methoxy acetic acid provide enantiomerically enriched alpha,beta-dihydroxy esters with high anti-diastereoselecitvity. The observed diastereoselectivity and reactivity could be rationalized by the analysis of six open transition states with the aid of computational calculation.
Graduation Semester
2008
Type of Resource
text
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http://hdl.handle.net/2142/84290

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