Return to search

Synthesis and rearrangements of vinylcyclopropanes in a [2+3] cyclopentene and oxycyclopentene annulation methodology approach to (-)- specionin

The addition of lithium dienolate 130, formed from ethyl 2-bromocrotonate, to enones and aldehydes yielding vinylcyclopropanes and vinyloxiranes was optimized. Various methods, pyrolytic and nonpyrolytic, were examined for the rearrangement of the resulting vinylcyclopropanes to cyclopentenes in an overall [2+3] annulation sequence. During the course of these studies, a new rearrangement pathway of these vinylcyclopropanes to bridged [3.2.n] bicyclic systems was discovered thus establishing a new [3+4] annulation technology.

The extension of the [2+3] annulation technology to oxygenated cyclopentanoids was addressed. Several ethyl 2-bromo-4-oxycrotonates were synthesized, and the reaction of their lithium dienolates (217) with enones was investigated. The rearrangement of the resulting enol ether terminated vinylcyclopropanes to oxygenated cyclopentenes was also examined.

[see document for diagram of chemical reaction]

The application of this methodology was expressed in a synthetic approach to (-)-specionin (109). The key steps in this synthesis involved the cyclopropanation of optically pure enone 147 with Iithium dienolate 155 to give vinylcyclopropanes 169-exo/endo and the rearrangement of 169 to the oxygenated cyclopentanoid 187-exo which possesses the correct stereochemistry for further elaboration to epoxy acetate 216, an intermediate in a reported synthesis of specionin.

[see document for diagrams of chemical reactions] / Ph. D.

Identiferoai:union.ndltd.org:VTETD/oai:vtechworks.lib.vt.edu:10919/54358
Date January 1989
CreatorsFleming, Alison A.
ContributorsChemistry, Hudlicky, Tomas, Wolfe, James F., Mason, John G., Tanko, James M., White, Robert H.
PublisherVirginia Polytechnic Institute and State University
Source SetsVirginia Tech Theses and Dissertation
Languageen_US
Detected LanguageEnglish
TypeDissertation, Text
Formatvi, 171 leaves, application/pdf, application/pdf
RightsIn Copyright, http://rightsstatements.org/vocab/InC/1.0/
RelationOCLC# 21063568

Page generated in 0.002 seconds