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Synfacts 2006(11): 1153-1153  
DOI: 10.1055/s-2006-949441
Metal-Catalyzed Asymmetric Synthesis and Stereoselective Reactions
© Georg Thieme Verlag Stuttgart · New York

Co-Catalyzed Reductive Aldol Cyclizations Using Diethylzinc as Reductant

Contributor(s): Hisashi Yamamoto, Matthew B. Boxer
H. W. Lam*, P. M. Joensuu, G. J. Murray, E. A. F. Fordyce, O. Prieto, T. Luebbers
University of Edinburgh, UK and F. Hoffmann-La Roche Ltd., Basel, Switzerland
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Publication History

Publication Date:
24 October 2006 (online)

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Significance

A highly diastereoselective reductive aldol cyclization to generate 4-hydroxypiperdin-2-one and pyrrolidin-2-ones was developed. Many different catalyst/reductant combinations were tried, including Cu(II) salts and Co(II) salts with NaBH2, TMDS (1,1,3,3-tetramethylhydro­siloxane), PhSiH3, Et3B, and Et2Zn. The best catalysts were determined to be Co(acac)2·H2O and CoCl2 depending on the substrate. The latter required addition of Cy2PPh as an electron-rich ligand to affect the reaction.