Title page for ETD etd-01052010-184710


Type of Document Master's Thesis
Author Perfetti, Michael Thomas
URN etd-01052010-184710
Title Diastereoselective α-Alkylation of Chiral β-Borylated Esters
Degree Master of Science
Department Chemistry
Advisory Committee
Advisor Name Title
Santos, Webster L. Committee Chair
Carlier, Paul R. Committee Member
Gibson, Harry W. Committee Member
Keywords
  • Diastereoselective α-alkylation
  • syn selective
  • 11B NMR
  • boron-“ate”
  • β-boronic ester
Date of Defense 2009-12-09
Availability unrestricted
Abstract
The use of boron in the synthesis and development of asymmetric methodologies and various biological and medicinal compounds has increased significantly over the last decade. This thesis reports the development of a novel diastereoselective reaction for the α-alkylation of chiral β-borylated esters. We propose that standard deprotonation of chiral β-borylated esters with lithium diisopropylamide (LDA) leads to the formation of a boron-“ate” intermediate that upon treatment with an alkylation reagent collapses to provide chiral α, β-substituted boronic esters with a high degree of diastereoselectivity. This reaction is powerful in that a wide range of chiral β-borylated ester substrates can be employed that possess varying degrees of substitution and steric bulk. Results show that the reaction is syn-selective and provides yields of up to 60%, with diastereomeric ratios as high as (9.7:1). Additionally, alkylation products from bulkier tert-butyl esters provide higher DR values compared to those of methyl esters that possess the same β-functional groups. Several techniques were utilized to elucidate the mechanism of this reaction including variations of reaction temperature and equivalents of base, and also real-time analysis of the reaction by 11B NMR experiments.
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