Date of Completion

5-5-2017

Embargo Period

5-17-2017

Keywords

Oxoammonium Salts, Oxidation, Amines, Nitriles, Imines, Hydride Removal, TEMPO, 4-acetamidoTEMPO, The Anomeric Effect, Contrasteric Effects, Electrostatic Interactions, Conformational Analysis, Free-Energy Differences, 1, 3-Dioxanes

Major Advisor

William F. Bailey

Associate Advisor

James M. Bobbitt

Associate Advisor

Mark W. Peczuh

Associate Advisor

Michael B. Smith

Field of Study

Chemistry

Degree

Doctor of Philosophy

Open Access

Open Access

Abstract

Novel oxidation methods utilizing oxoammonium salts have been developed and are discussed in the first portion of this work. By employing a stoichiometric amount of a commercially available oxoammonium salt, known as “Bobbitt’s salt,” a facile and efficient procedure for the oxidation of primary amines to nitriles has been realized. This methodology was further adapted into an efficient, scalable catalytic process. The use of Oxoneâ as an inexpensive, environmentally benign terminal oxidant allows for the in situ production of an oxoammonium salt, the primary oxidant, from a small quantity of 4-acetamido-2,2,6,6-tetramethylpiperidine-N-oxyl (4-acetamidoTEMPO or ACT), a nitroxide catalyst, accomplishing the oxidation of primary amines to nitriles. Mechanistic aspects and scope of the oxidations are fully described. A novel oxoammonium salt oxidant has been developed by the electronic modification of “Bobbitt’s salt” and the kinetics of the oxidation of alcohol substrates by these salts has been studied.

The second portion of this work involves evaluation of the conformational equilibra found within a variety saturated heterocycles and small molecules with an aim to elucidate the origin of contrasteric effects often observed in such systems. Particular attention is drawn to the role of electrostatic interactions in determining the conformational preferences within small molecules. Free-energy differences have been experimentally determined for a series of anancomeric 2,2-diaryl-1,3-dioxanes, 5-phenyl-1,3- dioxanes, 2-substituted-1,3-dioxanes, and substituted cyclohexane systems. Computational modeling, X-ray crystallography, and two-dimensional nuclear magnetic resonance studies were used to evaluate the experimental results. Intramolecular electrostatic interactions have been found to engender fascinating conformational phenomena, and in some cases, to a greater extent than what was previously understood.

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