Stereoselective Lewis Acid-Catalyzed α-Acylvinyl Additions

Troy E. Reynolds, Ashwin R. Bharadwaj, and Karl A. Scheidt*
Department of Chemistry, Northwestern University, 2145 Sheridan Road, Evanston, Illinois 60208
J. Am. Chem. Soc., 2006, 128 (48), pp 15382–15383
DOI: 10.1021/ja0653674
Publication Date (Web): November 10, 2006
Copyright © 2006 American Chemical Society
*

In papers with more than one author, the asterisk indicates the name of the author to whom inquiries about the paper should be addressed.

, scheidt@northwestern.edu

Abstract

Abstract Image

Silyloxyallenes derived from α-hydroxypropargylsilanes undergo efficient addition to aldehydes with catalytic amounts of Lewis acids. The allenes are accessed from the corresponding propargylsilanes in a base-catalyzed 1,2-Brook rearrangement/SE2‘ process. Enantioenriched propargylsilanes are synthesized by a new zinc-promoted addition of alkynes to acylsilanes in up to 74% ee. This work demonstrates that conversion to the silyloxyallenes occurs with minimal erosion in optical activity. The use of a chiral chromium(III) Lewis acid effects the catalytic asymmetric addition of racemic silyloxyallenes to aromatic aldehydes in up to 92% ee. The overall reaction is broad in scope and accommodates a wide variety of aromatic and aliphatic substituents on both the propargylsilane and aldehyde.

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History

  • Published In Issue December 06, 2006
  • Received July 26, 2006

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