Synthesis and conformational studies of indolizines

George, Rosemary (1994) Synthesis and conformational studies of indolizines. Masters thesis, Rhodes University.

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Abstract

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
Supervisors:Kaye, Perry
ID Code:3702
Deposited By: Philip Clarke
Deposited On:22 Oct 2012 06:19
Last Modified:22 Oct 2012 06:19
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