Enantioselective Conjugate Addition of Diethylzinc to Enones with Chiral Copper-QUIPHOS Catalyst Influence of the Addition of Water on the Enantioselectivity
作者:Guillaume Delapierre、Thierry Constantieux、Jean Michel Brunel、Gérard Buono
The use of a new chiral copper catalyst involving QUIPHOS as ligand in the 1,4-addition of Et2Zn to enones is reported. The dramatic beneficial effect of addition of water or Zn(OH)(2) to this system has been investigated, and led to an improvement of the enantiomeric excess from 7 to 61% ee.
Application of deoxycholic acid-based copper–phosphite complexes as ligands in the enantioselective conjugate addition of diethylzinc to acyclic enones
作者:Anna Iuliano、Patrizia Scafato
DOI:10.1016/s0957-4166(03)00044-2
日期:2003.3
Four phosphites obtained by linking enantiomerically pure binaphthylchlorophosphite to the two different hydroxy groups of deoxycholic acid were synthesized and used as chiral ligands in the enantioselective copper-catalyzed 1,4-addition of diethylzinc to acyclic enones. The ligands were screened for activity and enantioselectivity using chalcone as the substrate to establish the influence of the absolute configuration of the binaphthyl moiety as well as the position on the cholestanic backbone of the phosphite moiety. The ligand affording the best results was eventually used in the copper-catalyzed 1,4-addition to various acyclic enones, affording the alkylation products in good yields and e.e.s up to 78%. (C) 2003 Elsevier Science Ltd. All rights reserved.
Copper-catalyzed enantioselective conjugate addition of diethylzinc to acyclic enones with chiral sulfoxide–phosphine ligands
The copper-catalyzed enantioselectiveconjugateaddition of diethylzinc to acyclic enones was achieved with chiral sulfoxide–phosphine (SOP) ligands. This process showed good functional group tolerance and gave the 1, 4-adducts with excellent enantioselectivities (up to 96% ee).