Elsevier

Tetrahedron Letters

Volume 45, Issue 31, 26 July 2004, Pages 6041-6044
Tetrahedron Letters

Enantioselective addition of diethylzinc to N-diphenylphosphinoylimines employing cinchonidine and cinchonine as chiral ligands

https://doi.org/10.1016/j.tetlet.2004.06.018Get rights and content

Abstract

The use of the `pseudoenantiomeric pair' of cinchonine and cinchonidine as ligands for the addition of diethylzinc to N-diphenylphosphinoylimines has been investigated. With 1 equiv of cinchonidine as ligand, a series of chiral amines was prepared in good yield and enantiomeric excesses of up to 94%. The use of 2.0 equiv of methanol as an achiral additive was found significantly to improve the selectivity of the addition when using 0.2 equiv of ligand, yielding ee's close to those obtained with a stoichiometric amount of ligand.

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Acknowledgements

The Royal Society of Chemistry for financial Support through the Research Fund.

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