Graduation Semester and Year

2019

Language

English

Document Type

Dissertation

Degree Name

Doctor of Philosophy in Chemistry

Department

Chemistry and Biochemistry

First Advisor

Junha Jeon

Abstract

In my doctoral studies, the research is mainly focused on developing highly regio- and chemoselective C–C silylation of cyclopropanol derivatives with a hydrosilyl acetal directing group. This approach involves use of a relay of Ir-catalyzed hydrosilylation of inexpensive and readily prepared cyclopropanoacetates and Rh-catalyzed C–C silylation to achieve dioxasilolanes and dioxasilepines. In Chapter 1, we report a redox-neutral, catalytic C–C activation of cyclopropyl acetates to produce silicon-containing five-membered heterocycles in a highly regio- and chemoselective fashion. The umpolung selective silylation leading to dioxasilolanes is opposed to contemporary selective C–C functionalization protocols of cyclopropanols. Lewis base activation of dioxasilolanes as silyl carbinol equivalents undergoes the unconventional [1,2]-Brook rearrangement to form tertiary alcohols. Notably, mechanistic studies indicate that an electrophilic metal-pi interaction harnessing highly fluorinated Tp(CF3)2Rh(nbd) catalyst permitted a low temperature C–C activation. In Chapter 2, we report highly efficient generation of metallo homoenolate-enol ethers (MHEE) through catalytic net oxidative C–C activation of cyclopropyl acetates in regio, stereo-, and chemoselective fashion. MHEE, the ketone dianion equivalents can be converted to a new class of seven-membered silicon-containing heterocycles, dioxasilepines, which uniquely hold interconnected silyl group and Z-vinyl acetal. Scope of the hitherto unexplored reactivity of cyclopropyl acetates toward net oxidative C–C silylation and the versatility of the resulting dioxasilepines were demonstrated. These include late-stage, dehydrogenative C–C silylation of biologically relevant molecules, facile production of a range of difunctionalized ketones and 1,2-diols, and their application to bioconjugation chemistry. Preliminary mechanistic studies suggest that the C–C activation harnessing electron-rich Wilkinson-type catalyst is likely the turnover-determining step and a Rh-pi interaction is key to the efficient metal insertion to a C–C bond.

Keywords

Cyclopropanols, C–C activation, Silylation, Rhodium, Tris(pyrazolyl)borate, Metallo homoenolate- enol ether, Transition metal catalysis

Disciplines

Chemistry | Physical Sciences and Mathematics

Comments

Degree granted by The University of Texas at Arlington

Included in

Chemistry Commons

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