Chiral bipyridine–copper(II) complex. Crystal structure and catalytic activity in asymmetric cyclopropanation
作者:Hoi-Lun Kwong、Wing-Sze Lee、Hung-Foon Ng、Wing-Hong Chiu、Wing-Tak Wong
DOI:10.1039/a706754b
日期:——
A chiral bipyridineâcopper(II) complex has been prepared and its crystal structure determined. The structure involves a CuN2Cl2 compressed tetrahedral stereochemistry. Chiral bipyridine complexes of copper-(I) and -(II) triflate are active catalysts for asymmetric cyclopropanation of alkenes with enantiomeric excesses up to 92%.
The synthesis and characterisation of copper(I) complexes of chiral pyridine-containing macrocyclic ligands (Pc-L*) and their use as catalysts in asymmetriccyclopropanation reactions are reported. All ligands and metal complexes were fully characterised, including crystal structures of some species determined by X-ray diffraction on single crystals. This allowed characterising the very different conformations
Vitamin B<sub>12</sub> Derivatives as Natural Asymmetric Catalysts: Enantioselective Cyclopropanation of Alkenes
作者:Ying Chen、X. Peter Zhang
DOI:10.1021/jo049870f
日期:2004.4.1
Vitamin B12 derivatives were found for the first time to be general and efficient catalysts for asymmetric cyclopropanation of alkenes with ethyl diazoacetate (EDA). Among several common derivatives, aquocobalamin (B12a) was shown to be the most effective catalyst for a variety of alkenes, providing cis-dominant cyclopropanes in excellent yields and moderate enantioselectivity. Reactivity studies under
Chiral double-stranded helicates, formed between Cu(I) ion and C2-symmetric oligopyridines, were used for catalytic asymmetric cyclopropanation of alkenes; low catalyst loadings (0.2 mol%), high TONs (up to 404) and short reaction times (30–60 min) were achieved with [Cu2L2]OTf2 (L = chiral C2-symmetric terpyridine).
The synthesis and characterisation of copper(I) complexes, including two crystal structures of the new chiral pyridine-containing macrocyclic ligands (PC-type), and their use as catalysts in asymmetriccyclopropanation reactions are reported.