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Hemiaminals : a new chemotype for organocatalysis

Authors: Ramaotsoa, Valerie;

Hemiaminals : a new chemotype for organocatalysis

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.

Country
South Africa
Related Organizations
Keywords

Chemistry

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This is an alternative to the "Influence" indicator, which also reflects the overall/total impact of an article in the research community at large, based on the underlying citation network (diachronically).
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popularity
This indicator reflects the "current" impact/attention (the "hype") of an article in the research community at large, based on the underlying citation network.
BIP!Popularity provided by BIP!
influence
This indicator reflects the overall/total impact of an article in the research community at large, based on the underlying citation network (diachronically).
BIP!Influence provided by BIP!
impulse
This indicator reflects the initial momentum of an article directly after its publication, based on the underlying citation network.
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