Asymmetric synthesis of alcohols with two chiral centres from a racemic aldehyde by the selective addition of dialkylzinc reagents using (1S,2R)-(–)-N,N-dibutylnorephedrine and (S)-(+)-diphenyl-(1-methylpyrrolidin-2-yl)methanol as chiral catalysts
作者:Kenso Soai、Seiji Niwa、Toshihiro Hatanaka
DOI:10.1039/c39900000709
日期:——
Optically active alcohols with two chiral centres were obtained in up to 93% enantiomeric excess by the selective addition of dialkylzinc reagents to the racemic aldehyde, 2-phenylpropanal, using the title compounds as chiral catalysts.
The [1,2]-Wittig rearrangements of enantio-defined α-benzyloxypropyllithium and its (R)-α-methylbenzyloxy analogs, generated from the enantio-enriched stannanes via Sn / Li exchange, are shown to proceed predominantly with inversion of configuration at the Li-bearing terminus and retention of configuration at the migrating center, and exhibit a significant level of mutual enantiomer recognition in
Kinetic Resolution When the Chiral Auxiliary Is Not Enantiomerically Pure: Normal and Abnormal Behavior
作者:Timo O. Luukas、Christian Girard、David R. Fenwick、Henri B. Kagan
DOI:10.1021/ja990793t
日期:1999.10.1
Kinetic resolutions with enantioimpure chiral auxiliaries (reagents or catalysts) are considered, and a kinetic treatment for various rate laws is described. A useful parameter, the apparent stereoselectivity factor, is defined and correlated to the enantiomeric excess of the chiral auxiliary. Deviations from the regular laws are possible (asymmetric amplification or depletion). These anomalies have
[1,2]-Wittig rearrangement of enantio-defined α- alkoxyalkyllithiums: Stereochemistry at the Li-bearing terminus and mutual recognition of enantiomers during the radical recombination
The [1,2]-Wittig rearrangements of enantio-defined α-benzyloxypropyllithium and its (R)-α-methylbenzyloxy analogs, generated from the enantio-enriched stannanes via Sn / Li exchange, are shown to proceed predominantly with inversion of configuration at the Li-bearing terminus and retention of configuration at the migrating center, and exhibit a significant level of mutual enantiomer recognition in