We report herein the enantioselectiveCu-catalyzed conjugate addition of organometallic reagents to sensitive Michael acceptors and their application to the synthesis of relevant target molecules. This is one of the most important methodologies to form a C-C bond in an enantioselective manner. A wide range of alpha,beta-unsaturated aldehydes and beta,gamma-unsaturated-alpha-ketoesters has been successfully
The first asymmetric Cu-catalyzed conjugate addition of dialkylzinc zinc reagents to a large scope of enals in presence of phosphoramidite, SimplePhos, or (R)-BINAP ligands with enantiomeric excesses up to 90% is reported. Moreover, ACA of Grignard reagents afforded moderate to good 1,4-regioselectivities with enantioselectivities up to 90%.
Reactivity and regio- and enantioselectivities were strongly dependent on reaction conditions and substrates. Good to excellent regio- and enantioselectivities were obtained with zinc reagents R2Zn and aluminum reagents R3Al. However, the asymmetric conjugate addition of Grignard reagents afforded only moderate to good regio- and enantioselectivities. β-Substituted aldehydes constitute a very important
<i>Lower Rim</i> Functionalized Chiral Resorc[4]arenes Derived from Citronellal and Carvone
作者:Jochen Mattay、Michael Schiendorfer
DOI:10.1055/s-2005-872108
日期:——
In our work we have provided the lower rim of resorc[4]arenes with stereogenic centers as well as with functional groups. For the synthesis of these lower rim functionalized chiral resorc[4]arenes we have used aldehydes derived from citronellal and carvone. In general, the functional group was introduced into the aldehyde compound prior to the final cyclization step. In the case of substitution of the functional group by chloride ions during the cyclization step under standard conditions (HCl-EtOH, Î), hydrochloric acid was replaced by the conjugated acid of the functional group. Another strategy is the introduction of the iodo group at the lower rim of a resorc[4]arene, which can be easily substituted by good nucleophiles and mild bases without protection of the upper rim.