Phosphoramidite ligands, based on a chiral amine and atropoisomerically flexible biphenols, induce high enantioselectivities (ee's up to 98%) in the copper-catalyzed conjugateaddition of dialkyl zinc reagents to a variety of Michael acceptors.
Enantioselective copper catalysed 1,4-conjugate addition reactions using chiral N-heterocyclic carbenes
作者:Caroline L. Winn、Frédéric Guillen、Julien Pytkowicz、Sylvain Roland、Pierre Mangeney、Alexandre Alexakis
DOI:10.1016/j.jorganchem.2005.07.024
日期:2005.12
The preparation of a variety of chiral N-heterocyclic carbene (NHC) precursors is described. The relative merits of imidazolinium salts and silver carbenes as NHC precursors are discussed with respect to their synthesis, stability and performance in the copper catalysed conjugate addition of dialkyl zinc reagents to a variety of Michael acceptors. Enantioselectivities of up to 93% were achieved using
Catalytic Asymmetric Conjugate Addition on Macrocyclic and Acyclic Enones. Synthesis of <i>R</i>-(-)-Muscone
作者:Alexandre Alexakis、Cyril Benhaïm、Xavier Fournioux、Alexandra van den Heuvel、Jean-Marc Levêque、Sebastien March、Stephane Rosset
DOI:10.1055/s-1999-2931
日期:1999.11
The asymmetric conjugate addition of diethyl zinc to acyclic enones is described. With 1% Cu(OTf)2 and 2% of a chiral phosphite ligand, the catalyst allowed ee's up to 92'% to be obtained. The addition of dimethyl zinc to a macrocyclic 15-membered ring enone lead to opticallyactiveR-(-)-muscone, in 53% yield and 79% enantiomeric excess.