Copper-catalyzed enantioselective conjugate addition of dialkylzinc reagents to (2-pyridyl)sulfonyl imines of chalcones.
J Org Chem
; 70(18): 7451-4, 2005 Sep 02.
Article
en En
| MEDLINE
| ID: mdl-16122276
ABSTRACT
[reaction see text] The enantioselective catalytic 1,4-addition to alpha,beta-unsaturated ketimines is an unprecedented process. Herein, we document the copper-catalyzed addition of dialkylzinc reagents to (2-pyridylsulfonyl)imines of chalcones. This process occurs rapidly in the presence of a chiral phosphoramidite ligand to afford exclusively the 1,4-addition product. In the case of addition of dimethylzinc, enantioselectivities in the range 70-80% ee are obtained. The presence of the metal-coordinating 2-pyridylsulfonyl group proved to be essential for this reaction to proceed.