Fine-Tuning Monophosphine Ligands for Enhanced Enantioselectivity. Influence of Chiral Hemilabile Pendant Groups
作者:Aibin Zhang、T. V. RajanBabu
DOI:10.1021/ol0495063
日期:2004.4.1
[reaction: see text] C(2)-Symmetric P-(2-X-aryl)-2,5-dialkylphospholanes (X = dioxolan-2-yl or dioxan-2-yl), designed on the basis of a working model for asymmetric induction, are effective ligands for the Ni(II)-catalyzed asymmetric hydrovinylation of styrenes. Excellent yields (>99%), selectivities for the desired 3-arylbutenes (>99%), high S/C ratios (>1200), and ee's (up to 91%) have been realized for a
successfully employed for the Ni-catalyzed asymmetric hydrovinylation reaction. Diarylphosphinites, carrying β-acylamino groups prepared from readily available carbohydrates, in conjunction with highly dissociated counteranions [(3,5-(CF3)2C6H3]4B− or SbF6−}, effect the hydrovinylation of vinylarenes under ambient pressure of ethylene with high enantioselectivity. Nitrogen substituents such as –COCF3 and COPh
phosphoramidites are a promising class of ligands for nickel-catalyzed asymmetric hydrovinylation of vinyl arenes. Cooperative effects are operative when ligands with more than one element of chirality are used. Choosing the proper stereochemistry in each part of the modular ligand system leads to high chemoselectivities and excellent enantioselectivities up to 94%. Moreover, the catalysts derived from these
Synthesis of Optically Active β- or γ-Alkyl-Substituted Alcohols through Copper-Catalyzed Asymmetric Allylic Alkylation with Organolithium Reagents
作者:Sureshbabu Guduguntla、Martín Fañanás-Mastral、Ben L. Feringa
DOI:10.1021/jo401536u
日期:2013.9.6
An efficient one-pot synthesis of optically active β-alkyl-substituted alcohols through a tandem copper-catalyzedasymmetricallylicalkylation (AAA) with organolithium reagents and reductive ozonolysis is presented. Furthermore, hydroboration–oxidation following the Cu-catalyzed AAA leads to the corresponding homochiral γ-alkyl-substituted alcohols.
Enantioselective hydrovinylation via asymmetric counteranion-directed ruthenium catalysis
作者:Gaoxi Jiang、Benjamin List
DOI:10.1039/c1cc12499d
日期:——
The first Ru-catalyzed enantioselective hydrovinylation has been realized by using an asymmetriccounteranion-directedcatalysis strategy. Styrene derivatives react with ethylene in excellent yields and promising enantioselectivity using this approach.