Fe/Cr- and Co/Cr-Mediated Catalytic Asymmetric 2-Haloallylations of Aldehydes
作者:Michio Kurosu、Mei-Huey Lin、Yoshito Kishi
DOI:10.1021/ja045557j
日期:2004.10.1
is reported. The coupling reaction is effected by the use of a chiral sulfonamide-Cr complex (prepared in situ from 1d, CrBr3, Fe(III) or from Co(II), Et3N, and Mn), TMSCl, and 2,6-lutidine. The method reported here is operationally simple and scalable, furnishing 3-halohomoallylic alcohols with a synthetically useful level of enantiomericexcess.
The totalsynthesis of 4-methoxydecanoic acid and 4-methoxyundecanoic acid in racemic and stereoselective [(R) and (S)] forms has been accomplished. For stereoselective synthesis of the compounds (S) and (R)-BINOL complexes have been used to generate the required chiral centres. The antifungal activity of these compounds has been studied against different organisms and the results were found to be impressive
Application of Tridentate Bis(oxazoline) Ligands in Catalytic Asymmetric Nozaki–Hiyama Allylation and Crotylation: An Example of High Enantioselection with a Non-Symmetric Bis(oxazoline) Ligand
作者:Helen A. McManus、Pier Giorgio Cozzi、Patrick J. Guiry
DOI:10.1002/adsc.200505332
日期:2006.3
symmetric and non-symmetric bis(oxazoline) ligands was applied in the Nozaki–Hiyama allylation and crotylation of benzaldehyde. It was found that both the magnitude and sense of the asymmetric induction depended strongly on the nature and combination of the oxazoline substituents. For both reactions, the non-symmetric tert-butyl/benzyl-substituted ligand proved to be the optimal ligand and was applied successfully
to a valuable building block for the total synthesis of phytotoxicnonenolideputaminoxin. The enzymatic approach towards the enantioenriched homoallylic alcohol was compared to classical, nonenzymatic approaches using asymmetric reagent controlled allyl additions and the obtained building block was used for the total synthesis of putaminoxin and its (5S,6E,9S)-diastereomer. After the spectroscopic
Practical and efficient catalytic asymmetric allylic transfer reactions of achiral aldehydes with tin reagents promoted by BINOL-Ti(IV) complex are achieved with high enantioselectivity by the utilization of subjoined Lewis acid, B(OMe)3.