Date of Award
1992
Degree Type
Dissertation
Degree Name
Doctor of Philosophy
Abstract
Cycloseychellene, a tetracyclic sesquiterpene, has been a synthetic target of our group for some time and earlier work had ended with the preparation of a methyl enol ether intermediate. A possible pathway for the completion of this total synthesis had, as its key step, an intramolecular Prins (ene) reaction. Studies were conducted in order to examine possible methods for the formation of the enolate which this approach required. The possible use of a silyl enol ether, as the enolate precursor, was examined in a model study, but the preparation of the enol ether was not successful. In addition, model studies examined the demethylating ability of lithium dimethylamide for methyl aryl ethers and a methyl enol ether. It was thought that lithium dimethylamide might serve to demethylate the methyl enol ether intermediate prepared earlier, provide the necessary enolate, and so set the stage for the intramolecular Prins (ene) reaction. Although lithium dimethylamide was found to be a reasonably useful demethylating agent for aryl methyl ethers, no demethylation of the enol ether was observed.;Buckminsterfullerene possesses an equatorial belt of five benzene rings joined at the para positions. Although the cyclic oligoparaphenylenes (COPs) have yet to be synthesized, the knowledge gained from their preparation and the physical and electronic properties they possess, should provide further insight into the understanding of aromaticity. Central to our synthetic approach to (O{dollar}\sb6{dollar}) paracyclophane, or sexiphenylene as we refer to it, is the reductive dimerization of a dicarbonyl compound via McMurry reactions. The preparation of this diketone was successful, but attempts to achieve its reductive dimerization were not successful.;Organic chemists have found vinylcyclopropanes to be effective synthetic intermediates. Although these compounds can be prepared by a variety of methods, many of these approaches are of the multi-step variety. In order to add to the current collection of one-pot procedures, we have investigated an approach centred on the vinylcyclopropanation of {dollar}\alpha,\beta{dollar}-unsaturated ketones. At the heart of this strategy was a two step (one pot) operation consisting of a conjugate addition followed by an intramolecular S{dollar}\sb{lcub}\rm N{rcub}\sp\prime{dollar} displacement of a silyloxy group from an allylic position. The conjugative delivery of an appropriately silyloxyated vinyl anion was effected by higher-order organocuprate reagents. Efforts to induce the expulsion of two different silyloxy groups were not successful.
Recommended Citation
Walker, Jeffrey Robert, "Studies In Organic Synthesis: I Demethylation Of Methyl Enol Ethers And Methyl Aryl Ethers Ii Toward Sexiphenylene Iii Toward A New Method For Vinylcyclopropanation" (1992). Digitized Theses. 2149.
https://ir.lib.uwo.ca/digitizedtheses/2149