PMID: 11322558Apr 27, 2001Paper

Facial-selective allylation of methyl ketones for the asymmetric synthesis of alpha-substituted tertiary homoallylic ethers

Chemistry : a European Journal
Lutz F TietzeM Schäfer

Abstract

The asymmetric synthesis of enantiomerically pure a-substituted tertiary homoallylic ethers 4a, 11 and 12a-c by the allylation of ethyl methyl ketone (la) with gamma-substituted allylsilanes 9a-h is described. The allylsilanes were obtained by a nickel-catalysed Grignard cross-coupling reaction of (E)- and (Z)-(3-iodoallyl)trimethylsilane with various Grignard reagents. The reaction of the allylsilanes with la in the presence of the trimethylsilyl ether of N-trifluoroacetylnorpseudoephedrine (3), and catalytic amounts of a mixture of trimethylsilyl triflate and trifluoromethanesulfonic acid led to the homoallylic ethers 4a, 11 and 12a-c with two new stereogenic centres, with a selectivity of 1:9 to >20:1 for the homoallylic and of 1:99 to >60:1 for the allylic centre. The facial selectivity does not depend on the configuration of the allylsilane, and in all reactions the anti product is preferentially formed. Interestingly, a pronounced switch of facial selectivity takes place with increasing length of the alkyl group of the allylsilane.

References

Jun 1, 1987·Natural Product Reports·I Wahlberg, C R Enzell
Aug 6, 1998·Current Opinion in Chemical Biology·L F Tietze, M E Lieb
Feb 20, 2002·Chemical Reviews·James Staunton, Barrie Wilkinson

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Citations

Feb 27, 2004·Organic & Biomolecular Chemistry·Anthony CunninghamSimon Woodward
Feb 19, 2005·Angewandte Chemie·Diego J Ramón, Miguel Yus
May 16, 2009·Chemistry : a European Journal·Lutz F TietzeThomas Wolfram
Jan 22, 2009·Accounts of Chemical Research·Lutz F TietzeC Christian Brazel
Jul 12, 2012·The Journal of Organic Chemistry·Dane J Clausen, Paul E Floreancig

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