Mechanistic studies of diastereoselective cyclopropanations of homochiral ene-ketals and synthesis and resolution of diastereomeric alpha-hydroxycycloalkanone ketals.

Persistent Link:
http://hdl.handle.net/10150/184886
Title:
Mechanistic studies of diastereoselective cyclopropanations of homochiral ene-ketals and synthesis and resolution of diastereomeric alpha-hydroxycycloalkanone ketals.
Author:
Hemperly, Susan Barbara.
Issue Date:
1989
Publisher:
The University of Arizona.
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.
Abstract:
A series of homochiral ene ketals were prepared and subjected to the Simmons-Smith cyclopropanation. A mechanistic model was formulated to explain the observed diastereoselectivity seen for the common ring systems. Diastereoselectivity is thought to result from preferential chelation of the Simmons-Smith reagent at the least sterically hindered lone pair of electrons on the dioxolane oxygen proximal to the alkene. The role of dioxolane oxygen was inferred from studies with a hydrocarbon model system. The effect of cyclohexene ring conformation on the diastereoselectivity was examined for conformationally restricted ene ketal systems. Reagent chelation by the pseudoequatorial dioxolane oxygen atom was shown to be favored. This preference can either antagonize or reinforce diastereoselectivity due to steric hindrance of the dioxolane oxygen atoms from dissymmetric placement of the appendages on the dioxolane ring. A general method for the chromatographic resolution of diastereomeric α-hydroxycycloalkanone ketals derived from 1,4-di-O-benzyl-L-threitol is reported. Separability is thought to result from differences in intramolecular hydrogen bonding for the two diastereomeric forms.
Type:
text; Dissertation-Reproduction (electronic)
Keywords:
Stereochemistry; Chemical processes
Degree Name:
Ph.D.
Degree Level:
doctoral
Degree Program:
Chemistry; Graduate College
Degree Grantor:
University of Arizona
Advisor:
Mash, Eugene A.

Full metadata record

DC FieldValue Language
dc.language.isoenen_US
dc.titleMechanistic studies of diastereoselective cyclopropanations of homochiral ene-ketals and synthesis and resolution of diastereomeric alpha-hydroxycycloalkanone ketals.en_US
dc.creatorHemperly, Susan Barbara.en_US
dc.contributor.authorHemperly, Susan Barbara.en_US
dc.date.issued1989en_US
dc.publisherThe University of Arizona.en_US
dc.rightsCopyright © 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.en_US
dc.description.abstractA series of homochiral ene ketals were prepared and subjected to the Simmons-Smith cyclopropanation. A mechanistic model was formulated to explain the observed diastereoselectivity seen for the common ring systems. Diastereoselectivity is thought to result from preferential chelation of the Simmons-Smith reagent at the least sterically hindered lone pair of electrons on the dioxolane oxygen proximal to the alkene. The role of dioxolane oxygen was inferred from studies with a hydrocarbon model system. The effect of cyclohexene ring conformation on the diastereoselectivity was examined for conformationally restricted ene ketal systems. Reagent chelation by the pseudoequatorial dioxolane oxygen atom was shown to be favored. This preference can either antagonize or reinforce diastereoselectivity due to steric hindrance of the dioxolane oxygen atoms from dissymmetric placement of the appendages on the dioxolane ring. A general method for the chromatographic resolution of diastereomeric α-hydroxycycloalkanone ketals derived from 1,4-di-O-benzyl-L-threitol is reported. Separability is thought to result from differences in intramolecular hydrogen bonding for the two diastereomeric forms.en_US
dc.typetexten_US
dc.typeDissertation-Reproduction (electronic)en_US
dc.subjectStereochemistryen_US
dc.subjectChemical processesen_US
thesis.degree.namePh.D.en_US
thesis.degree.leveldoctoralen_US
thesis.degree.disciplineChemistryen_US
thesis.degree.disciplineGraduate Collegeen_US
thesis.degree.grantorUniversity of Arizonaen_US
dc.contributor.advisorMash, Eugene A.en_US
dc.contributor.committeememberBates, Robert B.en_US
dc.contributor.committeememberEnemark, John H.en_US
dc.contributor.committeememberSteelink, Corneliusen_US
dc.contributor.committeememberWigley, David E.en_US
dc.identifier.proquest9013147en_US
dc.identifier.oclc703434054en_US
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