Enantioselective Friedel-Crafts Alkylations by Strained Chiral Silacycle

S. Shirakawa; R. Berger; J. L. Leighton

doi:10.1055/s-2005-869914

Synfacts, Table of Contents

Synfacts 2005(0): 0048-0048
DOI: 10.1055/s-2005-869914

Metal-Catalyzed Asymmetric Synthesis and Stereoselective Reactions

Enantioselective Friedel-Crafts Alkylations by Strained Chiral Silacycle

Contributor(s): Hisashi Yamamoto, Matthew Boxer

S. Shirakawa, R. Berger, J. L. Leighton*
Columbia University, New York, USA
Enantioselective Friedel-Crafts Alkylations with Benzoylhydrazones Promoted by a Simple Strained Silacycle Reagent
J. Am. Chem. Soc. 2005, 127: 2858-2859

Abstract

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Key words

Friedel-Crafts alkylation - silacycles - Lewis acids

Significance

A chiral silicon Lewis acid has been utilized for the enantioselective Friedel-Crafts alkylation. The strained silacyle is effective at promoting the reaction for electron-rich aromatic systems under mild conditions.

Comment

This is a nice use of a chiral silicon Lewis acid for the important synthesis of heteroarylglycines. This paper provides another example of the proposed ‘strain-release Lewis acidity’ of silicon to promote reactions. The method uses a strain-induced effect of the five-member silacycle to give a significant increase in the acidity of the silicon center. This is proposed as the origin of the observed high reactivity and selectivity for the reaction. The method is not a truly catalytic reaction; however, the chiral amino alcohol is completely recoverable and reusable.

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