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A new C2-symmetric azolium compound for Cu-catalyzed asymmetric conjugate addition of R2Zn to cyclic enone
被引:22
|作者:
Harano, Ayako
Sakaguchi, Satoshi
[1
]
机构:
[1] Kansai Univ, Dept Chem & Mat Engn, Fac Chem Mat & Bioengn, Osaka 5648680, Japan
基金:
日本学术振兴会;
关键词:
Asymmetric catalysis;
N-Heterocyclic carbene;
Conjugate addition;
Polydentate ligand;
Ligand design;
N-HETEROCYCLIC CARBENES;
QUATERNARY STEREOGENIC CENTERS;
TRANSITION-METAL-COMPLEXES;
ALKOXY-NHC LIGANDS;
ENANTIOSELECTIVE SYNTHESIS;
GRIGNARD-REAGENTS;
STEREODIRECTING LIGANDS;
ALLYLIC ALKYLATIONS;
PINCER COMPLEXES;
COORDINATION;
D O I:
10.1016/j.jorganchem.2010.07.038
中图分类号:
O61 [无机化学];
学科分类号:
070301 ;
081704 ;
摘要:
A new chiral N-heterocyclic carbene (NHC) ligand was designed. Thus, an efficient synthetic route to C-2-symmetric bis(hydroxyamide)-functionalized benzimidazolium salts from chiral beta-amino alcohols was developed. The combination of Cu(OTf)(2) and the chiral azolium compound efficiently promoted the conjugate addition reaction of cyclic enone with dialkylzinc to give the corresponding adduct in good yield. Among a series of chiral NHC proligands, the functionalized benzimidazolium chloride possessing a tert-butyl group as a stereodirecting group was found to be the best choice of ligand. Under optimized reaction conditions, an excellent enantioselectivity (96% ee) was realized by allowing 2-cyclohepten-1-one to react with Bu2Zn at room temperature. (C) 2010 Elsevier B.V. All rights reserved.
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页码:61 / 67
页数:7
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