Palladium and a simple chiral amine are used as co‐catalysts for the enantioselective conjugate addition of aryl boronic acids to α,β‐unsaturated aldehydes (see scheme). The synthetic utility of this co‐catalyzed reaction was demonstrated in the short total syntheses of (R)‐(−)‐curcumene and 4‐aryl‐2‐ones.
Intermolecular Enantioselective Heck–Matsuda Arylations of Acyclic Olefins: Application to the Synthesis of β-Aryl-γ-lactones and β-Aryl Aldehydes
作者:Caio C. Oliveira、Ricardo A. Angnes、Carlos Roque D. Correia
DOI:10.1021/jo400378g
日期:2013.5.3
intermolecular Heck–Matsuda arylation of acyclic allylicalcohols. Aryldiazonium tetrafluoroborates were applied as arylating agents in the presence of Pd(TFA)2 and a chiral, commercially available, bisoxazoline ligand. The methodology is straightforward, robust, scalable up to a few grams, and of broad scope allowing the synthesis of a range of β-aryl-carbonyl compounds in good to high enantioselectivities
A Novel Organocatalytic Asymmetric Transfer Hydrogenation of<i>α</i>,<i>β</i>-Unsaturated Aldehydes
作者:Bao-Hua Zhang、Lan-Xiang Shi、Rui-Xia Guo
DOI:10.1002/hlca.201300029
日期:2013.11
α,β‐Unsaturated aldehydes reacted with diimide (diazene) in the presence of optically active ammonium salt 1 as a catalyst to give the corresponding saturated aldehydes in excellent yields and up to 98 : 2 er. Attractive features of the asymmetric transferhydrogenation are its high yields, and chemo‐, and enantioselectivities.
A resin-supported N-terminal prolyl peptide having a beta-turn motif and a polyleucine tether has been developed for the organocatalytic asymmetric transfer hydrogenation under aqueous conditions. Polyleucine accelerated the reaction in a highly enantioselective manner by providing a hydrophobic microenvironment around the prolyl residue. The investigation of catalyst structures indicates that the L-form of polyleucine is essential for both reaction efficiency and enantioselectivity. (c) 2009 Elsevier Ltd. All rights reserved.
Organocatalytic Asymmetric Transfer Hydrogenation in Aqueous Media Using Resin-Supported Peptide Having a Polyleucine Tether
A resin-supported N-terminal prolyl peptide having a beta-turn motif and hydrophobic polyleucine chain effectively catalyzed the asymmetric transfer hydrogenation under aqueous conditions. The polyleucine tether provides a hydrophobic cavity in aqueous media that brought about a remarkable acceleration of the reaction. In addition, the polyleucine chain also turned out to be essential for high enantioselectivity.