improved generation of chiral cationic iridium catalysts for the asymmetricisomerization of primaryallylicalcohols is disclosed. The design of these air‐stable complexes relied on the preliminary mechanistic information available, and on Charton analyses using two preceding generations of iridium catalysts developed for this highly challenging transformation. Sterically unbiased chiral aldehydes
Highly Enantioselective Asymmetric Isomerization of Primary Allylic Alcohols with an Iridium-N,P Complex
作者:Jia-Qi Li、Byron Peters、Pher G. Andersson
DOI:10.1002/chem.201101524
日期:2011.9.26
Access to chiral aldehydes: The asymmetricisomerization of primaryallylicalcohols was studied with a bicyclic phosphine‐oxazoline iridium catalyst. This method displays a broad substrate scope and leads to the desired chiral aldehydes with excellent enantioselectivities (see scheme; R1, R2=Ar or alkyl).
接触手性醛:使用双环膦-恶唑啉铱催化剂研究了伯烯丙基醇的不对称异构化。该方法显示出较宽的底物范围,并得到具有优异对映选择性的所需手性醛(参见方案; R 1,R 2= Ar或烷基)。
Copper-catalyzed Asymmetric Conjugate Addition to Challenging Michael Acceptors and Synthesis of Relevant Target Molecules
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