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Title:An investigation of phase transfer catalysis employing quantitative structure-activity relationships
Author(s):Duncan-Gould, Nathan W.
Director of Research:Denmark, Scott E.
Doctoral Committee Chair(s):Denmark, Scott E.
Doctoral Committee Member(s):Burke, Martin D.; Hergenrother, Paul J.; Gerlt, John A.
Department / Program:Chemistry
Degree Granting Institution:University of Illinois at Urbana-Champaign
Subject(s):phase transfer catalysis
quantitative structure-activity relationship
Abstract:The application of quantitative structure activity relationships to phase transfer catalysis (PTC) has been explored. The primary focus was on hydroxide-initiated PTC reactions, such as enolate alkylations. The tandem [4+2]/[3+2] cycloaddition of nitroalkenes was applied as the key transformation in the preparation of enantioenriched, tricyclic 1-hydroxy-cyclopentapyrrolizidine ring systems. A three-step parallel synthesis procedure was developed to prepare libraries of quaternary ammonium ions sharing a common core scaffold. In total, 80 quaternary ammonium bromides were prepared in this way. A kinetic method for the analysis of liquid-liquid PTC reactions was refined. The kinetic profile for an enolate alkylation reaction was determined for 102 different quaternary ammonium bromides catalysts under a standard set of conditions. The data ranges over three orders of magnitude in catalyst activity. QSAR models were developed to describe the activity of the catalysts. Three types of models were considered: (1) linear combinations (2) parabolic combinations, and (3) bilinear combinations. The models that best account fit the catalyst activity data and retain the smallest number of descriptors included parabolic or binlinear contributions from logP and XSA (XSA = cross-sectional area). Analysis of the model in the context of an interfacial mechanism led the hypothesis that the largest differences in catalyst activities were due to the sum of the interfacial adsorption and desorption rate constants. This hypothesis was tested by comparing the rate constants for the stoichiometric alkylation of quaternary ammonium phenoxides to the catalytic rate constants for a series of Td symmetric homologous. It is suggested that the hypothesis could be tested further by measuring the surface activity of the catalysts at the interface of a water-organic biphasic mixture.
Issue Date:2011-08-26
Rights Information:Copyright 2011 Nathan W. Duncan-Gould
Date Available in IDEALS:2013-08-27
Date Deposited:2011-08

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