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dc.contributor.authorZhang, Yiqunen
dc.date.accessioned2014-03-14T20:08:35Zen
dc.date.available2014-03-14T20:08:35Zen
dc.date.issued2007-03-15en
dc.identifier.otheretd-03282007-221111en
dc.identifier.urihttp://hdl.handle.net/10919/26535en
dc.description.abstractStereochemistry is important aspect of chemistry that customarily includes the study of the relative spatial arrangement of atoms within molecules (static stereochemistry), and the study of the stereochemical requirements and outcomes of chemical reactions (dynamic stereochemistry). These two branches complement each other in modern stereochemistry. Chiral organometallics feature prominently in organic synthesis as reactive intermediates. The possibility of exploring their stereochemistry in synthesis is associated with the configurational stability of the metal-bearing stereogenic center. We were interested in the configurational stability of lithiated and magnesiated nitriles. We developed a new series of lithio-cyclopropylnitriles bearing chelating groups for intramolecular coordination, as a possible strategy to impart configurational stability. Although this strategy has not yet been successful, using density functional theory (DFT) method, we addressed the effect of chelating groups on racemization via the â conducted tourâ mechanism. We then explored metal-bromine exchange on enantiopure bromonitrile as alternative route to metalated nitriles. In this way, we demonstrated that magnesiated 2,2-diphenyl cyclopropylnitrile is configurationally stable on the macroscopic timescale. No other metallated nitrile has ever demonstrated configurational stability on this timescale. In contrast, bromine-lithium exchange of 1-bromo-2,2-diphenyl-cyclopropylnitrile demonstrated fast racemization under the same conditions. Another major project focused on conformational control of acyclic molecules. Using X-ray crystallography and NMR spectroscopy, we found that the 2,6-disubstituted aryl group eclipses its geminal hydrogen, and induces an antiperiplanar relationship of the geminal and vicinal hydrogens. Interestingly, anti-nitrile aldols or syn-ketone aldols bearing 2,6-disubstituted aryl groups demonstrate unanticipated remote effects on acyclic conformation: the 2,6-disubstituted aryl group prefers to be in a gauche position to the largest vicinal group. The minimization of allylic 1,3-strain and syn-pentane-like interaction works together in establishing this conformational preference.en
dc.publisherVirginia Techen
dc.relation.haspartDissertation-final.pdfen
dc.rightsIn Copyrighten
dc.rights.urihttp://rightsstatements.org/vocab/InC/1.0/en
dc.subjectconformational controlen
dc.subjectchiral Grignard reagentsen
dc.subjecthalogen-metal exchangeen
dc.subjectcyclopropylnitrileen
dc.subjectconfigurational stabilityen
dc.subject3-strainen
dc.subjectallylic 1en
dc.subjectsyn-pentane interactionen
dc.subjectnitrile aldolen
dc.titleStereochemistry of small molecules: Configurational and conformational controlen
dc.typeDissertationen
dc.contributor.departmentChemistryen
dc.description.degreePh. D.en
thesis.degree.namePh. D.en
thesis.degree.leveldoctoralen
thesis.degree.grantorVirginia Polytechnic Institute and State Universityen
thesis.degree.disciplineChemistryen
dc.contributor.committeechairCarlier, Paul R.en
dc.contributor.committeememberKingston, David G. I.en
dc.contributor.committeememberHanson, Brian E.en
dc.contributor.committeememberTanko, James M.en
dc.contributor.committeememberEtzkorn, Felicia A.en
dc.identifier.sourceurlhttp://scholar.lib.vt.edu/theses/available/etd-03282007-221111/en
dc.date.sdate2007-03-28en
dc.date.rdate2007-04-09en
dc.date.adate2007-04-09en


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