Synthesis of six membered heterocycles containing nitrogen or oxygen
<p>Six-membered heterocycles containing nitrogen and oxygen are prevalent in natural products and pharmaceutical drugs; hence efficient synthesis of these motifs is of great benefit. This thesis describes the successful rearrangements of 5-membered heterocycles containing nitrogen and oxygen t...
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| Format: | Thesis |
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2005
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| _version_ | 1797069951583911936 |
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| author | Turner, P |
| author_facet | Turner, P |
| author_sort | Turner, P |
| collection | OXFORD |
| description | <p>Six-membered heterocycles containing nitrogen and oxygen are prevalent in natural products and pharmaceutical drugs; hence efficient synthesis of these motifs is of great benefit. This thesis describes the successful rearrangements of 5-membered heterocycles containing nitrogen and oxygen through to the corresponding 6-membered compounds.</p> <p><strong>Chapter 1 - Project Conception</strong></p> <p>This section outlined the project conception and aims.</p> <p><strong>Chapter 2 - Radical Ring-Expansions</strong></p> <p>This section contains an introduction to the radical mediated ring-expansions, which firstly focused on carbocylic precedent, before an in depth discussion on work relating to the radical ring-expansion of heterocycles.</p> <p><strong>Chapter 3 - Synthesis of Piperidines and Pyrrolidines</strong></p> <p>An introduction to the rearrangement of nitrogen containing heterocycles was examined, with particular emphasis on the one carbon ring-expansion of pyrrolines, azetines and lactams.</p> <p><strong>Chapter 4 - Rearrangements of Nitrogen Heterocycles</strong></p> <p>This section detailed the one-carbon radical ring-expansion of the pyrrolines obtained from the Birch reduction of electron deficient pyrroles. The scope of the reaction was examined with respect to substitution around the pyrroline ring. A postulated mechanism was presented with experimental evidence in the form of the synthesis fused bicycles. Attempts at inducing either an ionic or cationic ring-expansion were examined and a novel pyrroline ring-opening reaction presented.</p> <p><strong>Chapter 5 - Synthesis of Tetrahydropyrans</strong></p> <p>The literature on the ring-expansion reactions to form tetrahydropyrans was discussed, with particular emphasis paid on the tetrahydrofuran to tetrahydropyran rearrangement, the ringexpansion of epoxides and the ring-expansion of thiiranium ions.</p> <p><strong>Chapter 6 - Rearrangements of Oxygen Heterocycles</strong></p> <p>The development of the ring-expansion of tetrahydrofurans to tetrahydropyrans was described, with focus centred on the stereochemical requirements for efficient ring-expansion. A hydride shift pathway to form open chain ketones was exploited in the enantiopure synthesis of spiroketals.</p> |
| first_indexed | 2024-03-06T22:31:59Z |
| format | Thesis |
| id | oxford-uuid:58979b1b-59ba-4834-8140-1397afd51aff |
| institution | University of Oxford |
| last_indexed | 2024-03-06T22:31:59Z |
| publishDate | 2005 |
| record_format | dspace |
| spelling | oxford-uuid:58979b1b-59ba-4834-8140-1397afd51aff2022-03-26T17:04:22ZSynthesis of six membered heterocycles containing nitrogen or oxygenThesishttp://purl.org/coar/resource_type/c_db06uuid:58979b1b-59ba-4834-8140-1397afd51affPolonsky Theses Digitisation Project2005Turner, P<p>Six-membered heterocycles containing nitrogen and oxygen are prevalent in natural products and pharmaceutical drugs; hence efficient synthesis of these motifs is of great benefit. This thesis describes the successful rearrangements of 5-membered heterocycles containing nitrogen and oxygen through to the corresponding 6-membered compounds.</p> <p><strong>Chapter 1 - Project Conception</strong></p> <p>This section outlined the project conception and aims.</p> <p><strong>Chapter 2 - Radical Ring-Expansions</strong></p> <p>This section contains an introduction to the radical mediated ring-expansions, which firstly focused on carbocylic precedent, before an in depth discussion on work relating to the radical ring-expansion of heterocycles.</p> <p><strong>Chapter 3 - Synthesis of Piperidines and Pyrrolidines</strong></p> <p>An introduction to the rearrangement of nitrogen containing heterocycles was examined, with particular emphasis on the one carbon ring-expansion of pyrrolines, azetines and lactams.</p> <p><strong>Chapter 4 - Rearrangements of Nitrogen Heterocycles</strong></p> <p>This section detailed the one-carbon radical ring-expansion of the pyrrolines obtained from the Birch reduction of electron deficient pyrroles. The scope of the reaction was examined with respect to substitution around the pyrroline ring. A postulated mechanism was presented with experimental evidence in the form of the synthesis fused bicycles. Attempts at inducing either an ionic or cationic ring-expansion were examined and a novel pyrroline ring-opening reaction presented.</p> <p><strong>Chapter 5 - Synthesis of Tetrahydropyrans</strong></p> <p>The literature on the ring-expansion reactions to form tetrahydropyrans was discussed, with particular emphasis paid on the tetrahydrofuran to tetrahydropyran rearrangement, the ringexpansion of epoxides and the ring-expansion of thiiranium ions.</p> <p><strong>Chapter 6 - Rearrangements of Oxygen Heterocycles</strong></p> <p>The development of the ring-expansion of tetrahydrofurans to tetrahydropyrans was described, with focus centred on the stereochemical requirements for efficient ring-expansion. A hydride shift pathway to form open chain ketones was exploited in the enantiopure synthesis of spiroketals.</p> |
| spellingShingle | Turner, P Synthesis of six membered heterocycles containing nitrogen or oxygen |
| title | Synthesis of six membered heterocycles containing nitrogen or oxygen |
| title_full | Synthesis of six membered heterocycles containing nitrogen or oxygen |
| title_fullStr | Synthesis of six membered heterocycles containing nitrogen or oxygen |
| title_full_unstemmed | Synthesis of six membered heterocycles containing nitrogen or oxygen |
| title_short | Synthesis of six membered heterocycles containing nitrogen or oxygen |
| title_sort | synthesis of six membered heterocycles containing nitrogen or oxygen |
| work_keys_str_mv | AT turnerp synthesisofsixmemberedheterocyclescontainingnitrogenoroxygen |