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NHC-Catalyzed Intermolecular Stetter Reaction with Asymmetric Protonation
T. Jousseaume, N. E. Wurz, F. Glorius*
Universität Münster, Germany
18 March 2011 (online)
The Glorius group reports an intermolecular Stetter reaction between different aldehydes and N-acylamido acrylate catalyzed by the NHC derived from 1. The desired products, α-chiral amino acid derivatives, are obtained in high yields and high enantioselectivities for a broad scope of aldehydes. The observed enantioselectivity arises from the stereoselective protonation of the Michael adduct rather than from the prior C-C bond-forming event. The authors propose that the chiral catalyst forces the Michael addition to proceed with a well-defined geometry, setting the stage for the construction of the desired stereocenter by the intramolecular protonation. An alternative concerted mechanism can also not be ruled out as mentioned by the authors.