Organocatalytic enantio- and diastereoselective 1,3-dipolar cycloaddition between alanine-derived ketonitrones and E-crotonaldehyde: efficiency and full stereochemical studies
作者:Khalid B. Selim、Anne Beauchard、Jérôme Lhoste、Arnaud Martel、Mathieu Y. Laurent、Gilles Dujardin
DOI:10.1016/j.tetasy.2012.11.010
日期:2012.12
Highly enantio- and exo-selective 1,3-dipolar cycloadditions of alanine-derived ketonitrones to E-crotonaldehyde could be realized in a good yield by the use of a chiral imidazolidinone salt without the addition of water. The origin of the stereoselectivity in the reaction was discussed and the absolute configuration of the cycloadduct determined unambiguously. (C) 2012 Elsevier Ltd. All rights reserved.
The asymmetric organocatalytic 1,3-dipolar cycloaddition of alkyl pyruvate-derived nitrones and α,β-unsaturated aldehydes
catalytic asymmetric 1,3-dipolarcycloaddition of pyruvate-derived nitrones to α,β-unsaturatedaldehydes was investigated in the presence of various chiral amines. Highly functionalized isoxazolidines containing a quaternary stereocenter were obtained in moderate yields with up to 92% ee. To the best of our knowledge, this is the first example of an enantioselective1,3-dipolarcycloaddition of ketonitrones