Stereocontrol of palladium(ii)-catalysed aza-Claisen rearrangements using a combination of 1,3-allylic strain and a solvent mediated directing effect
作者:Michael D. Swift、Andrew Sutherland
DOI:10.1039/b613271e
日期:——
The use of a non-coordinating solvent for the aza-Claisen rearrangement of delta,epsilon-disubstituted acetimidates switches on a substrate directing effect that gives excellent stereoselectivity.
Substrate-controlled stereoselectivity in the Yamamoto aldol reaction
作者:Nadin Schläger、Andreas Kirschning
DOI:10.1039/c2ob26185e
日期:——
The Yamamoto aldol reaction is a vinylogous aldol reaction that relies on bulky aluminium-based Lewis acids. These activate both the aldehyde as well as become part of the enolate moiety. The report discloses the first detailed study on the substrate-controlled Yamamoto aldol reaction in which 2,3-syn and 2,3-anti disubstituted aldehydes serve as the stereodirecting elements. The “size” of the substituent in the β-position strongly determines the facial selectivity of enolate addition to the aldehyde. Large substituents favour formation of 1,3-syn diols while slim alkynyl groups preferentially lead to 1,3-anti products.