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Synfacts 2007(3): 0293-0293  
DOI: 10.1055/s-2007-968268
Metal-Catalyzed Asymmetric Synthesis and Stereoselective Reactions
© Georg Thieme Verlag Stuttgart · New York

Stereoselective α-Acylvinyl Additions Using Lewis Acids

Contributor(s): Mark Lautens, Praew Thansandote
T. E. Reynolds, A. R. Bharadwaj, K. A. Scheidt*
Northwestern University, Evanston, USA
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Publication History

Publication Date:
20 February 2007 (online)

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Significance

Silyloxyallenes, synthesized from acylsilanes via a [1,2]-Brook rearrangement, perform stereoselective α -acylvinyl additions to aldehydes when catalyzed by scandium(III). Excellent yields and control over E:Z geometry is seen, with the Z-isomer favored. A variety of alkyl and aryl aldehydes react with siloxyallenes containing diverse β-substituents. Although attempts to control the enantioselectivity of the acyl addition with a chiral allene were unsuccessful, use of a chiral chromium Lewis acid with racemic silyloxyallene resulted in 92% ee.