Enantiomerically pure rhodium complexes bearing 1,5-diphenyl-1,5-cyclooctadiene as a chiral diene ligand. Their use as catalysts for asymmetric 1,4-addition of phenylzinc chloride.
[reaction and structures: see text] A rhodium complex coordinated with 1,5-diphenyl-1,5-cyclooctadiene (Ph-cod), [RhCl((R)-Ph-cod)]2, was obtained enantiomerically pure through optical resolution of diastereomeric isomers [Rh(Ph-cod)((R)-1,1'-binaphthyl-2,2'-diamine)]BF4. The enantiomerically pure rhodium complexes showed high catalytic activity and enantioselectivity (up to 98% ee) in the asymmetric 1,4-addition of phenylzinc chloride to alpha,beta-unsaturated ketones and esters in the presence of chlorotrimethylsilane.
Kina
Asato
A
Department of Chemistry, Graduate School of Science, Kyoto University, Sakyo, Kyoto 606-8502, Japan.
Ueyama
Kazuhito
K
Hayashi
Tamio
T