Hemiaminals : a new chemotype for organocatalysis

 

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dc.contributor.advisor Hunter, Roger en_ZA
dc.contributor.author Ramaotsoa, Valerie en_ZA
dc.date.accessioned 2015-12-08T11:49:39Z
dc.date.available 2015-12-08T11:49:39Z
dc.date.issued 2015 en_ZA
dc.identifier.citation Ramaotsoa, V. 2015. Hemiaminals : a new chemotype for organocatalysis. University of Cape Town. en_ZA
dc.identifier.uri http://hdl.handle.net/11427/15706
dc.description.abstract 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. en_ZA
dc.language.iso eng en_ZA
dc.subject.other Chemistry en_ZA
dc.title Hemiaminals : a new chemotype for organocatalysis en_ZA
dc.type Master Thesis
uct.type.publication Research en_ZA
uct.type.resource Thesis en_ZA
dc.publisher.institution University of Cape Town
dc.publisher.faculty Faculty of Science en_ZA
dc.publisher.department Department of Chemistry en_ZA
dc.type.qualificationlevel Masters
dc.type.qualificationname MSc en_ZA
uct.type.filetype Text
uct.type.filetype Image
dc.identifier.apacitation Ramaotsoa, V. (2015). <i>Hemiaminals : a new chemotype for organocatalysis</i>. (Thesis). University of Cape Town ,Faculty of Science ,Department of Chemistry. Retrieved from http://hdl.handle.net/11427/15706 en_ZA
dc.identifier.chicagocitation Ramaotsoa, Valerie. <i>"Hemiaminals : a new chemotype for organocatalysis."</i> Thesis., University of Cape Town ,Faculty of Science ,Department of Chemistry, 2015. http://hdl.handle.net/11427/15706 en_ZA
dc.identifier.vancouvercitation Ramaotsoa V. Hemiaminals : a new chemotype for organocatalysis. [Thesis]. University of Cape Town ,Faculty of Science ,Department of Chemistry, 2015 [cited yyyy month dd]. Available from: http://hdl.handle.net/11427/15706 en_ZA
dc.identifier.ris TY - Thesis / Dissertation AU - Ramaotsoa, Valerie AB - 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. DA - 2015 DB - OpenUCT DP - University of Cape Town LK - https://open.uct.ac.za PB - University of Cape Town PY - 2015 T1 - Hemiaminals : a new chemotype for organocatalysis TI - Hemiaminals : a new chemotype for organocatalysis UR - http://hdl.handle.net/11427/15706 ER - en_ZA


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