880000-74-8Relevant academic research and scientific papers
Copper-catalyzed enantioselective 1,4-conjugate addition of dialkylzinc reagents to α,β- and α,β,γ,δ-unsaturated ketones
Rexiti, Rukeya,Lu, Jian,Sha, Feng,Wu, Xin-Yan
, p. 3596 - 3604 (2019/06/04)
An enantioselective Cu(II)-catalyzed conjugate addition of dialkylzinc reagents to α,β- or α,β,γ,δ-unsaturated ketones with chiral cyclohexane-based amidophosphine ligands was developed. With 2 mol% of Cu(OAc)2·H2O/L5, the conjugate
Modulation of multifunctional N,O,P ligands for enantioselective copper-catalyzed conjugate addition of diethylzinc and trapping of the zinc enolate
Ye, Fei,Zheng, Zhan-Jiang,Deng, Wen-Hui,Zheng, Long-Sheng,Deng, Yuan,Xia, Chun-Gu,Xu, Li-Wen
supporting information, p. 2242 - 2253 (2013/09/23)
In this work, we have successfully synthesized a new family of chiral Schiff base-phosphine ligands derived from chiral binaphthol (BINOL) and chiral primary amine. The controllable synthesis of a novel hexadentate and tetradentate N,O,P ligand that contains both axial and sp3-central chirality from axial BINOL and sp3-central primary amine led to the establishment of an efficient multifunctional N,O,P ligand for copper-catalyzed conjugate addition of an organozinc reagent. In the asymmetric conjugate reaction of organozinc reagents to enones, the polymer-like bimetallic multinuclear Cu-Zn complex constructed in situ was found to be substrate-selective and a highly excellent catalyst for diethylzinc reagents in terms of enantioselectivity (up to >99 % ee). More importantly, the chirality matching between different chiral sources, C2-axial binaphthol and sp3-central chiral phosphine, was crucial to the enantioselective induction in this reaction. The experimental results indicated that our chiral ligand (R,S,S)-L1- and (R,S)-L4-based bimetallic complex catalyst system exhibited the highest catalytic performance to date in terms of enantioselectivity and conversion even in the presence of 0.005 mol % of catalyst (S/C=20 000, turnover number (TON)=17 600). We also studied the tandem silylation or acylation of enantiomerically enriched zinc enolates that formed in situ from copper-L4-complex-catalyzed conjugate addition, which resulted in the high-yield synthesis of chiral silyl enol ethers and enoacetates, respectively. Furthermore, the specialized structure of the present multifunctional N,O,P ligand L1 or L4, and the corresponding mechanistic study of the copper catalyst system were investigated by 31P NMR spectroscopy, circular dichroism (CD), and UV/Vis absorption. Match maker: The chiral bimetallic multinuclear Cu-Zn complex that contains a novel phosphine ligand and bears matching axial and sp3-central chirality from binaphthol and chiral amine was found to be a highly efficient catalyst in the enantioselective conjugate addition of an organic zinc reagent. Copyright
Switchable stereoselectivity: The effects of substituents on the D 2-symmetric biphenyl backbone of phosphoramidites in copper-catalyzed asymmetric conjugate addition reactions with triethylaluminium
Yu, Han,Xie, Fang,Ma, Zhenni,Liu, Yangang,Zhang, Wanbin
supporting information; experimental part, p. 1941 - 1947 (2012/09/25)
A highly enantioselective copper-catalyzed conjugate addition with triethylaluminium was developed using phosphoramidite ligands bearing a D 2-symmetric biphenyl backbone. For these ligands we demonstrated that the 3,3',5,5'-substituents on the biphenyl backbone can completely reverse the absolute configuration of the products. Copyright
The effects of solvent on switchable stereoselectivity: Copper-catalyzed asymmetric conjugate additions using D2-symmetric biphenyl phosphoramidite ligands
Yu, Han,Xie, Fang,Ma, Zhenni,Liu, Yangang,Zhang, Wanbin
, p. 5137 - 5142 (2012/08/07)
A highly enantioselective copper-catalyzed conjugate addition of diethylzinc to acyclic aromatic enones was developed with phosphoramidite ligands bearing a D2-symmetric biphenyl backbone. This type of reaction demonstrated that toluene and THF solvents can completely reverse the absolute configuration of the products, thus simplifying the process of accessing either enantiomer (S: 92% ee, 94% yield; R: 99% ee, 96% yield).
Synthesis of novel carbohydrate-based chiral P, N ligands and their applications in Cu-catalyzed enantioselective 1, 4-conjugate additions
Xia, Haijun,Yan, Hua,Shen, Chao,Shen, Fangyi,Zhang, Pengfei
experimental part, p. 155 - 158 (2012/03/08)
A new type of phosphate-pyridine (P, N) ligand derived from d-glucosamine and BINOL was synthesized and successfully applied in Cu-catalyzed enantioselective conjugate addition of diethylzinc to chalcones for the first time, high yields and enantioselectivities were obtained when the ligand 10a which contains (S)-BINOL was used. The results also showed that the configuration of BINOL at the ligand backbone had remarkable effects on the activities and enantioselectivities.
Chiral phosphanylferrocenecarboxamides with amino acid pendant groups as ligands for Cu-mediated asymmetric conjugate additions of diethylzinc to chalcones - Structural characterisation of precursors to the Cu catalyst
Tauchman, Jiri,Cisarova, Ivana,Stepnicka, Petr
experimental part, p. 4276 - 4287 (2010/10/21)
A series of chiral phosphanylferrocenecarboxamides was prepared by treatment of either l'-(diphenylphosphanyl)ferrocene-1-carboxylic acid (Hdpf) or its planar-chiral 1,2isomers with amino acid methyl esters in the presence of peptide coupling agents. The compounds were characterised by spectroscopic methods, and the crystal structure of one representative was determined by X-ray diffraction. Catalytic testing of these donors in Cu-catalysed asymmetric conjugate additions of diethylzinc to chalcones revealed that the reaction outcomes were highly sensitive to the ligand structure and the reaction conditions (copper source and solvent), whereas the chalcone substituents (Me, MeO, or Cl in positions 4 or 4') had a less pronounced influence. Compounds based on Hdpf proved to be better ligands than their planarchiral analogues. Under optimised conditions, the reaction with L-valine-Hdpf conjugate, (S)-Ph2PfcCONHCH(CHMe2)CO2Me (fc = ferrocene-1,1'-diyl) and unsubstituted chalcone gave the alkylation product with complete conversion (20 °C/ 4 h) and in 87 % ee. The catalytic behaviour of the amidophosphane ligands was correlated to the results of a model coordination study and the crystal structure of [Cu(Ph2PfcCONHCH 2CO2Me)2](CF3SO3) ·2CHCl3.
