A series of 6-endo-(methylthio)-bicyclo[2.2.1]heptane-2-endo-proline amides was synthesized to study the neighboring proline amide participation in electron transfer from thioethers. The thioether with endo-pyrrolidine amide formed a two-center three-electron SO bond after one electron oxidation and the oxidation potential of the thioether was lowered by 530 mV and 330 mV compared to the corresponding exo-pyrrolidine amide and the primary amide analogues, respectively. The thioether with a proline methyl ester showed the oxidation potential of 410 mV higher than that of the pyrrolidine amide. The basis for this surprising result was revealed by an X-ray crystallographic structure study of the diastereomerically pure proline methyl ester which showed amide carbonyl n → methyl ester π* interaction which removes electron density from the neighboring amide which results in less effective neighboring amide participation in thioether oxidation. This accounts for the electrochemical result. A potent synthetic route for S-tert-butyl m-terphenyl thioethers was developed and a series of such thioethers was synthesized. Electrochemical studies showed through-space S∙∙∙π interaction with lower oxidation potentials for thioethers with more electron rich aromatic groups and higher oxidation potentials with electron withdrawing aromatic groups. Selective Suzuki reactions were discovered in which mono-coupling of the precursor dibromides could be achieved. A second coupling was then possible in which two different aromatic rings are attached to the central aryl thioether ring. This enabled the synthesis of a two-sulfur three-aromatic ring extended m-terphenyl thioether as a potential electron conductor. In support of this possibility this compound showed an oxidation potential of +0.99 V which is less positive than the +1.09 V measured for the mono-sulfur analog.
| Identifer | oai:union.ndltd.org:arizona.edu/oai:arizona.openrepository.com:10150/205471 |
| Date | January 2011 |
| Creators | Yamamoto, Takuhei |
| Contributors | Glass, Richard S., Ghosh, Indraneel, Zheng, Zhiping, Lichtenberger, Dennis L., Glass, Richard S. |
| Publisher | The University of Arizona. |
| Source Sets | University of Arizona |
| Language | English |
| Detected Language | English |
| Type | text, Electronic Dissertation |
| Rights | Copyright © is held by the author. Digital access to this material is made possible by the University Libraries, University of Arizona. Further transmission, reproduction or presentation (such as public display or performance) of protected items is prohibited except with permission of the author. |
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