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Synfacts 2011(9): 0982-0982  
DOI: 10.1055/s-0030-1260904
Metal-Catalyzed Asymmetric Synthesis and Stereoselective Reactions
© Georg Thieme Verlag Stuttgart ˙ New York

Catalytic Asymmetric Conjugate Addition of Pyrazolin-5-ones

Contributor(s): Hisashi Yamamoto, Patrick Brady
Z. Wang, Z. Yang, D. Chen, X. Liu, L. Lin, X. Feng*
Sichuan University, Chengdu, P. R. of China
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Publikationsdatum:
19. August 2011 (online)

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Significance

This conjugate addition process is catalyzed by a combination of a Lewis acid and a chiral N,N′-dioxide ligand. The highly enantio-­enriched product, which is a pyrazolone derivative, bears contiguous tertiary and quaternary stereocenters. Remarkably, changing the Lewis acid and the solvent results in a switch in enantioselectivity. These inverse effects between Sc and Y may also be observed in other asymmetric reactions.