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Hemiaminals : a new chemotype for organocatalysis
Jorgensen and List introduced enantioselective α-amination of an aldehyde with an azodicarboxylate as the electrophile using L -proline enamine catalysis in 2002. Following borohydride reduction, the α-hydrazino alcohol was obtained in high yield (93-99%) and enantioselectivity (86-97%). Application...
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| Format: | Thesis |
| Language: | English |
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Department of Chemistry
2015
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| _version_ | 1867614205372268544 |
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| access_status_str | Open Access |
| author | Ramaotsoa, Valerie |
| author2 | Hunter, Roger |
| author_browse | Hunter, Roger Ramaotsoa, Valerie |
| author_facet | Hunter, Roger Ramaotsoa, Valerie |
| author_sort | Ramaotsoa, Valerie |
| collection | Thesis |
| description | Jorgensen and List introduced enantioselective α-amination of an aldehyde with an azodicarboxylate as the electrophile using L -proline enamine catalysis in 2002. Following borohydride reduction, the α-hydrazino alcohol was obtained in high yield (93-99%) and enantioselectivity (86-97%). Application of the enantioselective α-amination reaction to an acetal as a masked aldehyde was developed in our group recently, and in part I of this thesis results on extending this chemistry to the α-amination of N-protected hemiaminals from N-heterocycles are reported, in which it was found that the reaction only worked with the carbonyl group exo to the ring. In the case of the hemiaminal derived from N-Boc or N-CBz 2-pyrrolidinone an amination with proline catalyst in acetonitrile over 3 days gave α-aminated products in high ee (77-84%). N-N bond hydrogenolysis using Raney Nickel and hydrogen, followed by oxidation to the lactam afforded the N -protected α-amino lactam in high enantioselectivity (78% and 8 6 %). In part II the development of a mild reduction of the N-N bond of the α-hydrazino amination products of straight-chain aldehydes is reported. The corresponding oxazolidinone- hydrazides are reduced to their oxazolidinones via a modified E1cB elimination using ethyl bromomalonate and potassium carbonate in acetonitrile. The reactions gave high yields (76-96%) and ees (83-95%) with a good chemoselectivity profile. |
| format | Thesis |
| id | oai:open.uct.ac.za:11427/15706 |
| institution | University of Cape Town (South Africa) |
| language | eng |
| last_indexed | 2026-06-10T12:48:20.619Z |
| license_str | Not specified — see source repository |
| provenance_str_mv | Harvested via OAI-PMH from UCTD — University of Cape Town Open Access Repository |
| publishDate | 2015 |
| publishDateRange | 2015 |
| publishDateSort | 2015 |
| publisher | Department of Chemistry |
| publisherStr | Department of Chemistry |
| record_format | dspace |
| source_str | UCTD — University of Cape Town Open Access Repository |
| spelling | oai:open.uct.ac.za:11427/15706 Hemiaminals : a new chemotype for organocatalysis Ramaotsoa, Valerie Hunter, Roger Chemistry Jorgensen and List introduced enantioselective α-amination of an aldehyde with an azodicarboxylate as the electrophile using L -proline enamine catalysis in 2002. Following borohydride reduction, the α-hydrazino alcohol was obtained in high yield (93-99%) and enantioselectivity (86-97%). Application of the enantioselective α-amination reaction to an acetal as a masked aldehyde was developed in our group recently, and in part I of this thesis results on extending this chemistry to the α-amination of N-protected hemiaminals from N-heterocycles are reported, in which it was found that the reaction only worked with the carbonyl group exo to the ring. In the case of the hemiaminal derived from N-Boc or N-CBz 2-pyrrolidinone an amination with proline catalyst in acetonitrile over 3 days gave α-aminated products in high ee (77-84%). N-N bond hydrogenolysis using Raney Nickel and hydrogen, followed by oxidation to the lactam afforded the N -protected α-amino lactam in high enantioselectivity (78% and 8 6 %). In part II the development of a mild reduction of the N-N bond of the α-hydrazino amination products of straight-chain aldehydes is reported. The corresponding oxazolidinone- hydrazides are reduced to their oxazolidinones via a modified E1cB elimination using ethyl bromomalonate and potassium carbonate in acetonitrile. The reactions gave high yields (76-96%) and ees (83-95%) with a good chemoselectivity profile. 2015-12-08T11:49:39Z 2015-12-08T11:49:39Z 2015 Master Thesis Masters MSc http://hdl.handle.net/11427/15706 eng application/pdf Department of Chemistry Faculty of Science University of Cape Town |
| spellingShingle | Chemistry Ramaotsoa, Valerie Hemiaminals : a new chemotype for organocatalysis |
| thesis_degree_str | Master's |
| title | Hemiaminals : a new chemotype for organocatalysis |
| title_full | Hemiaminals : a new chemotype for organocatalysis |
| title_fullStr | Hemiaminals : a new chemotype for organocatalysis |
| title_full_unstemmed | Hemiaminals : a new chemotype for organocatalysis |
| title_short | Hemiaminals : a new chemotype for organocatalysis |
| title_sort | hemiaminals a new chemotype for organocatalysis |
| topic | Chemistry |
| url | http://hdl.handle.net/11427/15706 |
| work_keys_str_mv | AT ramaotsoavalerie hemiaminalsanewchemotypefororganocatalysis |