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Synfacts 2011(1): 0068-0068  
DOI: 10.1055/s-0030-1258990
Metal-Catalyzed Asymmetric Synthesis and Stereoselective Reactions
© Georg Thieme Verlag Stuttgart ˙ New York

Lewis Acid Assisted Brønsted Acid Catalyzed Asymmetric Protonation Reaction

Contributor(s): Hisashi Yamamoto, Kimberly Griffin
C. H. Cheon, T. Imahori, H. Yamamoto*
The University of Chicago, USA; Kumamoto University, Japan
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Publication History

Publication Date:
21 December 2010 (online)

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Significance

Despite the increasing use of ­Brønsted acids in catalysis, application of these catalysts is often restricted due to lower reactivities compared to Lewis acid catalysts. The authors here use a Lewis acid assisted Brønsted acid (LBA) system to increase the reactivity of the Brønsted acid, and apply the catalyst nicely to the asymmetric protonation of silyl enol ethers of 2-substituted cyclic ketones. The Lewis base ­tolerance allows for a catalytic reaction, which was previously unattainable with LBA systems.