Graduation Semester and Year

2015

Language

English

Document Type

Thesis

Degree Name

Master of Science in Chemistry

Department

Chemistry and Biochemistry

First Advisor

Junha Jeon

Abstract

Homologation of esters to α,β-unsaturated esters is a useful transformation in organic synthesis. We have developed a new approach for the Ir-catalyzed reductive Horner-Wadsworth-Emmons olefination of esters; a one-pot method for the transformation of esters to α,β-unsaturated esters utilizing silyl acetals as aldehyde equivalents followed by Horner-Wadsworth-Emmons olefination. Lewis based activation of silyl acetals formed by Ir-catalyzed hydrosilylation of esters initially generates putative penta-coordinate silicate acetals which fragment into aldehydes, silanes and alkoxides in situ. The alkoxides deprotonate phosphonate esters which subsequently react with the aldehydes to furnish α,β-unsaturated esters. This method is operationally simple compared with aluminium hydride-based reductive Horner-Wadsworth-Emmons olefination. Notably, Horner-Wadsworth-Emmons olefination of traditionally challenging substrates such as aryl, alkenyl and alkynl esters furnishes the corresponding α,β-unsaturated esters at room temperature with excellent stereoselectivities (E/Z > 20:1) and moderate to excellent yields (48–91%). This transformation will contribute to enhancing the utility of silyl acetals in synthetic chemistry.

Disciplines

Chemistry | Physical Sciences and Mathematics

Comments

Degree granted by The University of Texas at Arlington

Included in

Chemistry Commons

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