The effects of solvent on switchable stereoselectivity: copper-catalyzed asymmetric conjugate additions using D2-symmetric biphenyl phosphoramidite ligands
A highly enantioselective copper-catalyzed conjugateaddition of diethylzinc to acyclic aromatic enones was developed with phosphoramidite ligands bearing a D2-symmetric biphenyl backbone. This type of reaction demonstrated that toluene and THF solvents can completely reverse the absolute configuration of the products, thus simplifying the process of accessing either enantiomer (S: 92% ee, 94% yield;
Enantioselective Catalytic Conjugate Addition of Dialkylzinc Reagents using Copper–Phosphoramidite Complexes; Ligand Variation and Non-linear Effects
作者:Leggy A Arnold、Rosalinde Imbos、Alessandro Mandoli、André H.M de Vries、Robert Naasz、Ben L Feringa
DOI:10.1016/s0040-4020(00)00142-3
日期:2000.4
cyclohexenone and chalcone in order to assess the structural features that are important for stereocontrol. A sterically demanding amine moiety is essential to reach high e.e.’s. Enantioselectivities for chalcones up to 89% and for cyclic enones up to 98% were found. Studies on non-linear effects with the best ligands for both cyclohexenone and chalcone showed clear non-linear effects for both cyclic
Switchable Stereoselectivity: The Effects of Substituents on the D2-Symmetric Biphenyl Backbone of Phosphoramidites in Copper-Catalyzed Asymmetric Conjugate Addition Reactions with Triethylaluminium
A highly enantioselective copper‐catalyzed conjugateaddition with triethylaluminium was developed using phosphoramidite ligands bearing a D2‐symmetric biphenylbackbone. For these ligands we demonstrated that the 3,3′,5,5′‐substituents on the biphenylbackbone can completely reverse the absolute configuration of the products.
Asymmetric synthesis of optically active β-substituted ketones by highly enantioselective catalytic conjugate addition of dialkylzinc reagents to enones using a catalyst system of nickel(<scp>II</scp>)-chiral ligand–achiral ligand in acetonitrile/toluene
作者:Kenso Soai、Tomoiki Hayasaka、Shoji Ugajin
DOI:10.1039/c39890000516
日期:——
Highly enantioselective conjugate addition of dialkylzincreagents to aryl substituted enones using Ni(II)-bipyridyl–chiral ligand in acetonitrile (MeCN)/toluene as an in situ prepared catalyst system affords β-substituted ketones in up to 90% enantiomeric excess (e.e.).
Copper-catalyzed enantioselective 1,4-conjugate addition of dialkylzinc reagents to α,β- and α,β,γ,δ-unsaturated ketones
作者:Rukeya Rexiti、Jian Lu、Feng Sha、Xin-Yan Wu
DOI:10.1016/j.tet.2019.05.029
日期:2019.6
An enantioselective Cu(II)-catalyzed conjugate addition of dialkylzinc reagents to α,β- or α,β,γ,δ-unsaturated ketones with chiral cyclohexane-based amidophosphine ligands was developed. With 2 mol% of Cu(OAc)2·H2O/L5, the conjugate addition of diethylzinc to α,β-unsaturated ketones was achieved in good-to-excellent yields (up to 98%) and high enantioselectivities (up to 92% ee). This catalytic system