Synthesis of insect lipid using organobismuth remote stereocontrol of acyclic 1,3, 5 - trimethyl compounds

The organometallic chemistry of the main group IV metals has been dominated by the widespread commercial exploitation of tin and lead. The high toxicity problems associated with organotin compounds has lead to the need to limit their use. Organobismuth chemistry is attracting interest. Bismuth metal...

Full description

Saved in:

Bibliographic Details
Main Author:	Basar, Norazah
Format:	Thesis
Language:	English
Published:	2009
Subjects:	QD Chemistry
Online Access:	http://eprints.utm.my/id/eprint/17002/1/NorazahBasarPFSA2009.pdf
Tags:	Add Tag No Tags, Be the first to tag this record!

id	my-utm-ep.17002
record_format	uketd_dc
spelling	my-utm-ep.170022018-06-25T09:00:05Z Synthesis of insect lipid using organobismuth remote stereocontrol of acyclic 1,3, 5 - trimethyl compounds 2009 Basar, Norazah QD Chemistry The organometallic chemistry of the main group IV metals has been dominated by the widespread commercial exploitation of tin and lead. The high toxicity problems associated with organotin compounds has lead to the need to limit their use. Organobismuth chemistry is attracting interest. Bismuth metal is considered to be safe, as it is non-toxic and non-carcinogenic, in spite of its heavy metal status. Embodied in this thesis is a discussion concerning the use of organobismuth as a replacement for organotin compounds in remote stereoselective control by promoting coupling reactions of (2R,3E)-1-(benzyloxy)-5-bromo-2,4- dimethylpent-2-ene with aldehydes. (2R,3E)-1-(Benzyloxy)-5-bromo-2,4- dimethylpent-2-ene was synthesised from methyl (2S)-3-hydroxy-2- methylpropanoate in five steps with an overall yield of 41%. Addition of this bromide and an aldehyde to bismuth(III) iodide and zinc in THF at room temperature gave a �90:10 (1,5-anti:1,5-syn) ratio of homoallylic alcohols in ca. 70% yield. The generality of these bismuth(III) iodide promoted reactions is reported including the successful coupling of several aldehydes with consistently good yields and selectivities. Identification of the relative stereochemistry of the major isomer was achieved by means of 1H NMR. When this was not possible, inversion of the newly formed chiral centre was employed to determine the selectivity of the reaction. The absolute configuration of the hydroxyl group in the major diastereoisomer was confirmed by comparison of the 1H NMR spectra of its (R)- and (S)-Oacetylmandelates. The mechanism of these bismuth reactions has not been investigated, although it is suggested that it is similar to tin-Lewis acid reactions. Acyclic compounds with syn-and anti-disposed 1,3,5-trimethyl substituents were prepared from 1,5-stereocontrol homoallylic alcohol via stereoselective reduction of the trisubstituted alkenes. The application of this methodology to the synthesis of natural products was tested with the preliminary work on the synthesis of the cuticular hydrocarbon, 4,6,8,10,16-pentamethyldocosane isolated from the cane beetle Antitrogus parvulus. 2009 Thesis http://eprints.utm.my/id/eprint/17002/ http://eprints.utm.my/id/eprint/17002/1/NorazahBasarPFSA2009.pdf application/pdf en public phd doctoral Universiti Teknologi Malaysia, Faculty of Science Faculty of Science
institution	Universiti Teknologi Malaysia
collection	UTM Institutional Repository
language	English
topic	QD Chemistry
spellingShingle	QD Chemistry Basar, Norazah Synthesis of insect lipid using organobismuth remote stereocontrol of acyclic 1,3, 5 - trimethyl compounds
description	The organometallic chemistry of the main group IV metals has been dominated by the widespread commercial exploitation of tin and lead. The high toxicity problems associated with organotin compounds has lead to the need to limit their use. Organobismuth chemistry is attracting interest. Bismuth metal is considered to be safe, as it is non-toxic and non-carcinogenic, in spite of its heavy metal status. Embodied in this thesis is a discussion concerning the use of organobismuth as a replacement for organotin compounds in remote stereoselective control by promoting coupling reactions of (2R,3E)-1-(benzyloxy)-5-bromo-2,4- dimethylpent-2-ene with aldehydes. (2R,3E)-1-(Benzyloxy)-5-bromo-2,4- dimethylpent-2-ene was synthesised from methyl (2S)-3-hydroxy-2- methylpropanoate in five steps with an overall yield of 41%. Addition of this bromide and an aldehyde to bismuth(III) iodide and zinc in THF at room temperature gave a �90:10 (1,5-anti:1,5-syn) ratio of homoallylic alcohols in ca. 70% yield. The generality of these bismuth(III) iodide promoted reactions is reported including the successful coupling of several aldehydes with consistently good yields and selectivities. Identification of the relative stereochemistry of the major isomer was achieved by means of 1H NMR. When this was not possible, inversion of the newly formed chiral centre was employed to determine the selectivity of the reaction. The absolute configuration of the hydroxyl group in the major diastereoisomer was confirmed by comparison of the 1H NMR spectra of its (R)- and (S)-Oacetylmandelates. The mechanism of these bismuth reactions has not been investigated, although it is suggested that it is similar to tin-Lewis acid reactions. Acyclic compounds with syn-and anti-disposed 1,3,5-trimethyl substituents were prepared from 1,5-stereocontrol homoallylic alcohol via stereoselective reduction of the trisubstituted alkenes. The application of this methodology to the synthesis of natural products was tested with the preliminary work on the synthesis of the cuticular hydrocarbon, 4,6,8,10,16-pentamethyldocosane isolated from the cane beetle Antitrogus parvulus.
format	Thesis
qualification_name	Doctor of Philosophy (PhD.)
qualification_level	Doctorate
author	Basar, Norazah
author_facet	Basar, Norazah
author_sort	Basar, Norazah
title	Synthesis of insect lipid using organobismuth remote stereocontrol of acyclic 1,3, 5 - trimethyl compounds
title_short	Synthesis of insect lipid using organobismuth remote stereocontrol of acyclic 1,3, 5 - trimethyl compounds
title_full	Synthesis of insect lipid using organobismuth remote stereocontrol of acyclic 1,3, 5 - trimethyl compounds
title_fullStr	Synthesis of insect lipid using organobismuth remote stereocontrol of acyclic 1,3, 5 - trimethyl compounds
title_full_unstemmed	Synthesis of insect lipid using organobismuth remote stereocontrol of acyclic 1,3, 5 - trimethyl compounds
title_sort	synthesis of insect lipid using organobismuth remote stereocontrol of acyclic 1,3, 5 - trimethyl compounds
granting_institution	Universiti Teknologi Malaysia, Faculty of Science
granting_department	Faculty of Science
publishDate	2009
url	http://eprints.utm.my/id/eprint/17002/1/NorazahBasarPFSA2009.pdf
_version_	1747815138139832320

Synthesis of insect lipid using organobismuth remote stereocontrol of acyclic 1,3, 5 - trimethyl compounds

Similar Items