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New methods for the synthesis of nitrogen containing, biologically relevant small molecules

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Howard, JK (2015) New methods for the synthesis of nitrogen containing, biologically relevant small molecules. PhD thesis, University of Tasmania.

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Abstract

The following thesis consists of two independent parts, both linked by a common
theme of developing new methods for the synthesis of small nitrogen containing
molecules. The first part is titled the oxidative dearomatisation of pyrrole, while the
second part is titled the strain driven rearrangement of cyclopropenyl
trichloroacetimidates.
The oxidation of pyrrole typically leads to uncontrolled polymerisation and
decomposition, however it was postulated that under appropriate reaction conditions
the controlled oxidation of pyrrole to 2-pyrrolinone would be possible. Thus, the
controlled oxidation of electron rich pyrroles was achieved in good to excellent
yields with the hypervalent iodine oxidant Dess−Martin periodinane, and also its
synthetic precursor 2-iodoxybenzoic acid (IBX). The sensitized photo-oxidation of
pyrrole was also examined by utilizing the narrow spectrum light emission from
LEDs. This led to an optimised method for the photo-oxidation of a range of pyrroles
to produce 2-pyrrolinones in good to high yields; a result that was only possible due
to limiting the absorbance of light by pyrrole and selectively exciting the dye
sensitizer for the oxidation. The products from the methods of controlled pyrrole
oxidation have been used in an initial study towards the total synthesis of pyrrolidine
alkaloid natural products including preussin, codonopsinine and crispine A.
Nitrogen-substituted benzylidene cyclopropanes were prepared by a strain-driven
Overman rearrangement of cyclopropenyl trichloroacetimidates in good to excellent
yields. This methodology demonstrates the first rearrangement of a cyclopropene to
an alkylidenecyclopropane with a nitrogen atom participant. The product
benzylidene cyclopropanes were used as precursors to biologically relevant
cyclopropyl ureas and saturated cyclopropanes.

Item Type: Thesis (PhD)
Keywords: Pyrrole, Cyclopropene, Oxidation, Rearrangement, Pyrrolinone, Photochemistry
Copyright Holders: The Author
Copyright Information:

Copyright 2015 the author

Date Deposited: 01 Aug 2016 00:38
Last Modified: 04 Jul 2017 17:00
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