Copper-catalyzed enantioselective conjugate addition of diethylzinc to acyclic enones in the presence of planar-chiral phosphaferrocene-oxazoline ligands.
[reaction: see text] A new subclass of chiral phosphaferrocene-oxazoline ligands has been applied to the copper-catalyzed asymmetric conjugate addition of diethylzinc to acyclic enones, furnishing good enantioselectivity. The ligand design readily lends itself to modification, thereby facilitating optimization of ee. Although the dominant stereocontrol element in these 1,4-addition processes is the central chirality of the oxazoline subunit of the ligand, not the planar chirality of the phosphaferrocene, altering the phosphaferrocene subunit can provide useful enhancement of enantioselectivity.
Shintani
Ryo
R
Department of Chemistry, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, USA.
Fu
Gregory C
GC