Ferrocene phosphane–carbene ligands in Cu-catalyzed enantioselective 1,4-additions of Grignard reagents to α,β-unsaturated carbonyl compounds
摘要:
Chiral ferrocene phosphane-carbenes are good ligands for the copper-catalyzed 1,4-addition of Grignard reagents to various Michael acceptors. The products were obtained in high enantiomeric purity (up to e.r. = 95:5) and excellent regioselectivity (r.r. = 99:1). These ligands are also useful for domino conjugate addition followed by enolate trapping with imine and aldehyde. (C) 2013 Elsevier B.V. All rights reserved.
Chiral phosphine–phosphite ligands in the enantioselective 1,4-addition of Grignard reagents to α,β-unsaturated carbonyl compounds
作者:Qaseem Naeemi、Tobias Robert、Darius P. Kranz、Janna Velder、Hans-Günther Schmalz
DOI:10.1016/j.tetasy.2011.04.018
日期:2011.4
phosphine–phosphite ligands was evaluated in the Cu-catalyzed asymmetric 1,4-addition of Grignard reagents to cyclopentenone, cycloheptenone and 5,6-dihydro-2H-pyran-2-one. TADDOL-based ligands 1a and 1b with a bulky substituent at the ortho-position to the chiral phosphite moiety gave rise to the 1,4-addition products with high enantioselectivities (up to 93% ee). In addition to ethyl-MgBr (as a standard