Asymmetric Diels-Alder studies involving chiral acetylenic diesters and investigations of an intramolecular Diels-Alder approach to the pentalenolactones
Thesis (Ph.D.)--Memorial University of Newfoundland, 1998. Chemistry Bibliography: leaves 239-247 Asymmetric Diels-Alder reactions of 2-(trimethylsilyloxy)cyclohexa-1,3-diene 17a, 6,6-dimethyl-2-(trimethylsilyloxy)cyclohexa-1,3-diene 17b, and 5,5-dimethyl-2-(trimethylsilyloxy)cyclohexa-1,3-diene 17c...
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ftmemorialunivdc:oai:collections.mun.ca:theses3/86510 2023-05-15T17:23:32+02:00 Asymmetric Diels-Alder studies involving chiral acetylenic diesters and investigations of an intramolecular Diels-Alder approach to the pentalenolactones Buckle, Ronald Neil, 1969- Memorial University of Newfoundland. Dept. of Chemistry 1998 320 leaves : ill. Image/jpeg; Application/pdf http://collections.mun.ca/cdm/ref/collection/theses3/id/86510 eng eng Electronic Theses and Dissertations (30.50 MB) -- http://collections.mun.ca/PDFs/theses/Buckle_RonalNeil.pdf a1273031 http://collections.mun.ca/cdm/ref/collection/theses3/id/86510 The author retains copyright ownership and moral rights in this thesis. Neither the thesis nor substantial extracts from it may be printed or otherwise reproduced without the author's permission. Paper copy kept in the Centre for Newfoundland Studies, Memorial University Libraries Diels-Alder reaction Asymmetric synthesis Diolefins Text Electronic thesis or dissertation 1998 ftmemorialunivdc 2015-08-06T19:18:45Z Thesis (Ph.D.)--Memorial University of Newfoundland, 1998. Chemistry Bibliography: leaves 239-247 Asymmetric Diels-Alder reactions of 2-(trimethylsilyloxy)cyclohexa-1,3-diene 17a, 6,6-dimethyl-2-(trimethylsilyloxy)cyclohexa-1,3-diene 17b, and 5,5-dimethyl-2-(trimethylsilyloxy)cyclohexa-1,3-diene 17c with several chiral acetylenedicarboxylates were conducted. Modest levels of diastereoselectivity were obtained for several examples. -- Semiempirical molecular orbital calculations for the Diels-Alder reactions of 2-hydroxy analogues of these dienes with di-f-butyl acetylenedicarboxylate were carried out to help interpret the experimental results. Four transtion states having very similar relative energies were obtained for each diene-dienophile combination. The calculations also supported an asynchronous transition state with the shorter incipient bond nearest the electron-donating trimethylsiloxy group. It follows that the ester group further from the trimethylsiloxy group most likely adopts a "fixed", parallel-planar conformation to activate the triple bond for attack, whereas the other ester is perpendicular to the incoming diene. -- (3-Phenylsulfonyl-2-propynyl) 2-(5,5-dimethyl-2-oxocyclohex-3-enyl) ethanoate 223 and ((E)-3-phenylsulfonyl-2-propenyl) 2-(5,5-dimethyl-2- (((1,1-dimethylethyl)dimethylsilyl)oxy)cyclohexa-1,3-dienyl)ethanoate 231 could serve as precursors in the synthesis of pentalenolactones. Our synthesis of these compounds was based on alkylation of 4,4-dimethyl-2-cyclohexen-1-one 20c with 2-halo esters similar to compound 146. -- Various 2-bromo esters were prepared and converted to their corresponding 2-iodo equivalents via the Finkelstein reaction. These 2-iodo esters were found to undergo alkylation in good yield with 4,4-dimethyl- 2-cyclohexen-1-one 20c. In this manner, (3-phenylthio-2-propynyl) 2-(5,5-dimethyl-2-oxocyclohex-3-enyl)ethanoate 205 was synthesized from (3-phenylthio-2-propynyl) 2-iodoethanoate 204. Treatment under kinetic conditions gave the desired diene, (3-phenylthio-2-propynyl) 2-(5,5-dimethyl-2- (((1,1 -dimethylethyl)dimethylsilyl)oxy)cyclohexa-1,3-dienyl)ethanoate 220. Activation of the alkyne, by oxidation to the sulfone, gave (3-phenylsulfonyl-2-propynyl) 2-(5,5-dimethyl-2-oxocyclohex-3-enyl)ethanoate 223.-- A similar route involving (E)-3-phenylsulfonyl-2-propen-1-ol 227 as the starting alcohol resulted in (( )-3-phenylsulfonyl-2-propenyl) 2-(5,5-dimethyl-2-oxocyclohex-3-enyl)ethanoate 230. Diene formation under thermodynamic conditions gave ((E)-3-phenylsulfonyl-2-propenyl) 2-(5,5-dimethyl-2- (((1,1 dimethylethyl)dimethylsilyl)oxy)cyclohexa-1,3-dienyl)ethanoate231 Thesis Newfoundland studies University of Newfoundland Memorial University of Newfoundland: Digital Archives Initiative (DAI) |
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Memorial University of Newfoundland: Digital Archives Initiative (DAI) |
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ftmemorialunivdc |
language |
English |
topic |
Diels-Alder reaction Asymmetric synthesis Diolefins |
spellingShingle |
Diels-Alder reaction Asymmetric synthesis Diolefins Buckle, Ronald Neil, 1969- Asymmetric Diels-Alder studies involving chiral acetylenic diesters and investigations of an intramolecular Diels-Alder approach to the pentalenolactones |
topic_facet |
Diels-Alder reaction Asymmetric synthesis Diolefins |
description |
Thesis (Ph.D.)--Memorial University of Newfoundland, 1998. Chemistry Bibliography: leaves 239-247 Asymmetric Diels-Alder reactions of 2-(trimethylsilyloxy)cyclohexa-1,3-diene 17a, 6,6-dimethyl-2-(trimethylsilyloxy)cyclohexa-1,3-diene 17b, and 5,5-dimethyl-2-(trimethylsilyloxy)cyclohexa-1,3-diene 17c with several chiral acetylenedicarboxylates were conducted. Modest levels of diastereoselectivity were obtained for several examples. -- Semiempirical molecular orbital calculations for the Diels-Alder reactions of 2-hydroxy analogues of these dienes with di-f-butyl acetylenedicarboxylate were carried out to help interpret the experimental results. Four transtion states having very similar relative energies were obtained for each diene-dienophile combination. The calculations also supported an asynchronous transition state with the shorter incipient bond nearest the electron-donating trimethylsiloxy group. It follows that the ester group further from the trimethylsiloxy group most likely adopts a "fixed", parallel-planar conformation to activate the triple bond for attack, whereas the other ester is perpendicular to the incoming diene. -- (3-Phenylsulfonyl-2-propynyl) 2-(5,5-dimethyl-2-oxocyclohex-3-enyl) ethanoate 223 and ((E)-3-phenylsulfonyl-2-propenyl) 2-(5,5-dimethyl-2- (((1,1-dimethylethyl)dimethylsilyl)oxy)cyclohexa-1,3-dienyl)ethanoate 231 could serve as precursors in the synthesis of pentalenolactones. Our synthesis of these compounds was based on alkylation of 4,4-dimethyl-2-cyclohexen-1-one 20c with 2-halo esters similar to compound 146. -- Various 2-bromo esters were prepared and converted to their corresponding 2-iodo equivalents via the Finkelstein reaction. These 2-iodo esters were found to undergo alkylation in good yield with 4,4-dimethyl- 2-cyclohexen-1-one 20c. In this manner, (3-phenylthio-2-propynyl) 2-(5,5-dimethyl-2-oxocyclohex-3-enyl)ethanoate 205 was synthesized from (3-phenylthio-2-propynyl) 2-iodoethanoate 204. Treatment under kinetic conditions gave the desired diene, (3-phenylthio-2-propynyl) 2-(5,5-dimethyl-2- (((1,1 -dimethylethyl)dimethylsilyl)oxy)cyclohexa-1,3-dienyl)ethanoate 220. Activation of the alkyne, by oxidation to the sulfone, gave (3-phenylsulfonyl-2-propynyl) 2-(5,5-dimethyl-2-oxocyclohex-3-enyl)ethanoate 223.-- A similar route involving (E)-3-phenylsulfonyl-2-propen-1-ol 227 as the starting alcohol resulted in (( )-3-phenylsulfonyl-2-propenyl) 2-(5,5-dimethyl-2-oxocyclohex-3-enyl)ethanoate 230. Diene formation under thermodynamic conditions gave ((E)-3-phenylsulfonyl-2-propenyl) 2-(5,5-dimethyl-2- (((1,1 dimethylethyl)dimethylsilyl)oxy)cyclohexa-1,3-dienyl)ethanoate231 |
author2 |
Memorial University of Newfoundland. Dept. of Chemistry |
format |
Thesis |
author |
Buckle, Ronald Neil, 1969- |
author_facet |
Buckle, Ronald Neil, 1969- |
author_sort |
Buckle, Ronald Neil, 1969- |
title |
Asymmetric Diels-Alder studies involving chiral acetylenic diesters and investigations of an intramolecular Diels-Alder approach to the pentalenolactones |
title_short |
Asymmetric Diels-Alder studies involving chiral acetylenic diesters and investigations of an intramolecular Diels-Alder approach to the pentalenolactones |
title_full |
Asymmetric Diels-Alder studies involving chiral acetylenic diesters and investigations of an intramolecular Diels-Alder approach to the pentalenolactones |
title_fullStr |
Asymmetric Diels-Alder studies involving chiral acetylenic diesters and investigations of an intramolecular Diels-Alder approach to the pentalenolactones |
title_full_unstemmed |
Asymmetric Diels-Alder studies involving chiral acetylenic diesters and investigations of an intramolecular Diels-Alder approach to the pentalenolactones |
title_sort |
asymmetric diels-alder studies involving chiral acetylenic diesters and investigations of an intramolecular diels-alder approach to the pentalenolactones |
publishDate |
1998 |
url |
http://collections.mun.ca/cdm/ref/collection/theses3/id/86510 |
genre |
Newfoundland studies University of Newfoundland |
genre_facet |
Newfoundland studies University of Newfoundland |
op_source |
Paper copy kept in the Centre for Newfoundland Studies, Memorial University Libraries |
op_relation |
Electronic Theses and Dissertations (30.50 MB) -- http://collections.mun.ca/PDFs/theses/Buckle_RonalNeil.pdf a1273031 http://collections.mun.ca/cdm/ref/collection/theses3/id/86510 |
op_rights |
The author retains copyright ownership and moral rights in this thesis. Neither the thesis nor substantial extracts from it may be printed or otherwise reproduced without the author's permission. |
_version_ |
1766113111816798208 |