Tetraalkllleads (R4Pb) reacted quite smoothly with aldehydes R′CHO in the presence of TiCl4 to produce the corresponding alcohols (RCHOHR′) in high to good yields. The reagent system, R4Pb/TiCl4, exhibited high chemoselectivity; only aldehydes underwent the alkylation in the presence of ketones. Further, the newreagent exhibited high 1,2- and 1,3-asymmetric induction. The transfer order of alkyl groups
Highly Diastereoselective 1,2-Asymmetric Addition of Dialkylzincs to Chiral 2-Phenylpropanal Catalyzed by Amino Alcohol
作者:Kenso Soai、Seiji Niwa、Toshihiro Hatanaka
DOI:10.1246/bcsj.63.2129
日期:1990.7
Diastereoselective addition of dialkylzinc reagents to 2-phenylpropanal using amino alcohol as catalyst afforded erythro alcohols (Cram-selectivity) in high diastereomeric excess (up to 88% d.e.).
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
Complete Regio- and Stereoselectivity Control in the Halohydroxylation of Non-activated Allenes Mediated by a Remote Sulfinyl Group
作者:José Luis García Ruano、Vanesa Marcos、José Alemán
DOI:10.1002/anie.200900448
日期:2009.4.14
regioselectivity and stereoselectivity of the halohydroxylation of non‐activated allenes are controlled by a remote sulfinyl group through anchimericassistance (see scheme). The resulting halohydrines are excellent chiral targets for the preparation of optically pure propargylic alcohols and Baylis–Hillman‐type products.