Highly optically active 3-phenylalkanals were obtained by the reaction of alkyl halides and a chiral homoenolate equivalent derived from the cinnamyl ether 3 and potassium diisopropylamide, followed by acidic hydrolysis.
Catalytic Enantioselective β-Alkylation of α,β-Unsaturated Aldehydes by Combination of Transition-Metal- and Aminocatalysis: Total Synthesis of Bisabolane Sesquiterpenes
aldehydes by combination of simple chiral amine and copper catalysts provides β‐branched aldehydes in a one‐pot protocol (see scheme). The methodology was applied to the short total syntheses of bisabolanesesquiterpenes (S)‐(+)‐curcumene, (E)‐(S)‐(+)‐3‐dehydrocurcumene and (S)‐(+)‐tumerone.
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 Enantioselective 1,4-Addition to α,β-Unsaturated Aldehydes
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