Please use this identifier to cite or link to this item:
|Title: ||The chemistry of vinyllead triacetates|
|Authors: ||Stoermer, Martin John|
|Issue Date: ||1990|
|Publisher: ||University of Sydney|
|Abstract: ||This thesis is concerned with the investigations of the reactions of
vinyllead tricarboxylates, derived from vinylstannanes and divinylmercury
compounds, and their applications to organic synthesis.
The work is discussed in three sections:
Section 1: VINYLLEAD TRICARBOXYLATES AS A SOURCE OF VINYL CATIONS
The reaction of a vinylstannane or divinylmercury compound with lead
tetraacetate (or other tetracarboxylates), generally performed in
chloroform solution, gives rise to a vinyllead triacetate. These species
are usually unstable compounds that decompose via either a vinyl cation
mechanism, or a /3-elimination (Reactions A and B). Compelling evidence
for vinyl cation formation was obtained in a number of cases, in which
rearrangement across the double bond occurred (e.g. Reaction A).
By using suitably substituted vinylstannanes, it was possible to
generate primary vinyl cations, species which are thought not to be formed
in solvolysis reactions. In two cases, the vinyl cations formed underwent
intramolecular aromatic electrophilic substitution (e.g. Reaction C).
It was shown in a series of experiments that the mechanism was not of
a carbene nature, as species arising from carbene insertion into
carbon-carbon double bonds were not observed (e.g. Reaction D). Capture
of the cationic intermediate by neighbouring methoxyl groups was also
observed (Reaction E).
SECTION 2: IMPROVEMENTS IN THE a-VINYLATION REACTION OF /3-DICARBONYL
The vinyllead tricarboxylates mentioned above, have been used in the
past* as vinylating reagents for /3-dicarbonyl compounds (Reaction F).
The use of tributylvinylstannanes and divinylmercury compounds as the
precursors of the lead reagent, had serious limitations, both in the ease
of purification of the products and in the production of "wasted" vinylic
residues. The use of trimethylvinylstannanes has now been shown to
produce not only easier workup procedures, but also in general higher
yields of the vinylated products than was previously attainable.
It was also found that lead tetrabenzoate was a superior reagent in
this reaction, producing faster exchange times and better yields. Lead
tetrapivalate was found to be better than lead teraacetate in some cases,
but inferior to lead tetrabenzoate.
* Moloney, M.G., and Pinhey, J.T., J. Chem. Soc. Perkin Trans. 1, 1988,
SECTION 3: JH AND °C NMR STUDIES OF VINYLLEAD TRICARBOXYLATES
By the use of high resolution n.m.r. spectroscopy, it was possible to
characterise a large number of vinyl-lead tricarboxylates by means of the
207Pb satellites about the vinylic protons in the *H n.m.r. spectra of
these compounds. These 207Pb-H coupling costants were very large (690-1660
Hz) and found to decrease in the series:
J 207Pb,Htram > J 207Pb,Hgem > J 207Pb,Hcis
In a few cases it was also possible to observe 207Pb-C coupling
constants in the n.m.r. spectra of these compounds.
It was also found that the lead compounds were identical, whether
derived from the tributylstannanes or trimethylstannanes, or from the
|Type of Work: ||PhD Doctorate|
|Type of Publication: ||Doctor of Philosophy Ph.D.|
|Appears in Collections:||Sydney Digital Theses (Open Access)|
This work is protected by Copyright. All rights reserved. Access to this work is provided for the purposes of personal research and study. Except where permitted under the Copyright Act 1968, this work must not be copied or communicated to others without the express permission of the copyright owner. Use the persistent URI in this record to enable others to access this work.
|0000000600660493-StoermerMartinJohn_1990.pdf||Thesis||8.4 MB||Adobe PDF|
Items in Sydney eScholarship Repository are protected by copyright, with all rights reserved, unless otherwise indicated.