George, Rosemary (1994) Synthesis and conformational studies of indolizines. Masters thesis, Rhodes University.
The present investigation has involved a kinetic and mechanistic study of the thermal cyclization of 3-acetoxy-3-(2-pyridyl)-2-methylenepropanoate esters and related compounds to 2-substituted indolizines. Substrates for the kinetic study were prepared via the Baylis-Hillmann reaction of pyridine-2-carboxaldehydes with acrylate esters, acrylonitrile and methyl vinyl ketone. The resulting hydroxy compounds were then acetylated to afford the acetoxy derivatives, thermal cyclization of which gave the corresponding 2-substituted indolizines. The cyclization reactions was followed using 'H NMR spectroscopy and were shown to follow firstorder kinetics. The influence of the various substituents on the observed first-order rate constants has been examined and variable temperature studies have permitted evaluation of activation parameters for the formation of methyl indolizine-2-carboxylate and ethyl indolizine-2-carboxylate. An alternative route to 2-substituted indolizines via halogenated derivatives was explored and several halogenated 2-pyridyl derivatives were synthesised and their thermal cyclization to indolizines was attempted. Novel 5-methylindolizine-2-carboxamides were prepared as part of this investigation and dynamic NMR spectroscopy was used to study internal rotation about the amide N-CO bond in these compounds.
|Item Type:||Thesis (Masters)|
|Uncontrolled Keywords:||Kinetic study, Mechanistic study, Esters, Indolizines, Baylis-Hillmann reaction, Acrylate esters, Acrylonitrile, Methyl vinyl, Hydroxy compounds, Cyclization reactions, Spectroscopy, Halogenated derivatives, Internal rotation, Ketone|
|Subjects:||Q Science > QD Chemistry > QD241 Organic chemistry|
|Divisions:||Faculty > Faculty of Science > Chemistry|
|Deposited By:||Philip Clarke|
|Deposited On:||22 Oct 2012 06:19|
|Last Modified:||22 Oct 2012 06:19|
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