Copper-catalyzed enantioselective conjugate addition of dialkylzinc reagents to (2-pyridyl)sulfonyl imines of chalcones.

Jorge Esquivias, Ramon Gómez Arrayás, Juan C Carretero

Index: J. Org. Chem. 70 , 7451, (2005)

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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.