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Toward Asymmetric Aldol-Tishchenko Reactions with Enolizable Aldehydes: Access to Defined Configured Stereotriads, Tetrads, and Stereopentads

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posted on 15.05.2009, 00:00 by Kerstin Rohr, Robert Herre, Rainer Mahrwald
Asymmetric aldol-Tishchenko reactions of enolizable aldehydes and ketones in the presence of chiral BINOLTi(OtBu)2/cinchona alkaloids complexes are described. Different configurative outcomes of these reactions depend on an equilibration through a retro aldol/aldol sequence and can be influenced by the configurative architecture of substrates. The results are explained by means of transition state models and rate constants. These considerations offer a fine-tuning of diastereoselectivity in aldol-Tishchenko reactions. Extensions of this research give access to defined configured stereotriads, stereotetrads, and stereopentads.