Ionic Liquid-Promoted, Highly Regioselective Heck Arylation of Electron-Rich Olefins by Aryl Halides

Jun Mo, Lijin Xu, and Jianliang Xiao*
Contribution from the Department of Chemistry, Liverpool Centre for Materials and Catalysis, University of Liverpool, Liverpool L69 7ZD, U.K.
J. Am. Chem. Soc., 2005, 127 (2), pp 751–760
DOI: 10.1021/ja0450861
Publication Date (Web): December 16, 2004
Copyright © 2005 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.

, j.xiao@liv.ac.uk

Abstract

Abstract Image

Palladium-catalyzed regioselective Heck arylation of the electron-rich olefins, vinyl ethers 1a−d, enamides 1e−g, and allyltrimethylsilane 1h, has been accomplished in imidazolium ionic liquids with a wide range of aryl bromides and iodides instead of the commonly used, but commercially unavailable and expensive, aryl triflates. The reaction proceeded with high efficiency and remarkable regioselectivity without the need for costly or toxic halide scavengers, leading exclusively to substitution by aryl groups of diverse electronic and steric properties at the olefinic carbon α to the heteroatom of 1a−g and β to the heteroatom of 1h. In contrast, the arylation reaction in molecular solvents led to mixtures of regioisomers under similar conditions. Several lines of evidence point to the unique regiocontrol stemming from the ionic environment provided by the ionic liquid that alters the reaction pathway. The chemistry provides a simple, effective method for preparing branched, arylated olefins and contributes to the extension of Heck reaction to a wider range of substrates.

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History

  • Published In Issue January 19, 2005
  • Received August 16, 2004

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