Chiral C1-symmetric 2,2′:6′,2′′-terpyridine ligands: Synthesis,characterization, complexation with copper(II), rhodium(III) and ruthenium(II) ions and use of the complexes in catalytic cyclopropanation of styrene |
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| Authors: | Chi-Tung Yeung Wing-Sze Lee Chui-Shan Tsang Shek-Man Yiu Wing-Tak Wong Wai-Yeung Wong Hoi-Lun Kwong |
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| Institution: | 1. Department of Biology and Chemistry and Open Laboratory of Chirotechnology of the Institute of Molecular Technology for Drugs Discovery and Synthesis, City University of Hong Kong, Tat Chee Avenue, Kowloon, Hong Kong, China;2. Department of Chemistry, The University of Hong Kong, Pokfulam Road, Hong Kong, China;3. Department of Chemistry, Hong Kong Baptist University, Waterloo Road, Hong Kong, China |
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| Abstract: | Three new optically pure C1-terpyridine ligands (L1–3) were prepared and the copper(II) complexes, of formula Cu(L)Cl2], the rhodium(III) complexes, of formula Rh(L)Cl3], and the ruthenium(II) complexes, of formula cis- or trans-Ru(L)(X)Cl2] (X = DMSO or CO), were synthesized. Structures of a chiral C1-ligand, a copper complex, a rhodium complex and a ruthenium DMSO complex were analysed using X-ray crystal structure analysis. The copper, rhodium and ruthenium complexes were shown to be precursors of catalysts for cyclopropanation. Reaction of Cu(L)Cl2], Rh(L)Cl3] or cis- or trans-Ru(L)(X)Cl2] with AgOTf converted the complex to catalyst, which in the case of trans-Ru(L)(CO)Cl2] gave enantioselectivities of up to 67% ee for the cis-isomers of styrene cyclopropanes with t-butyl diazoacetate. Comparisons with C2-analog of copper, rhodium and ruthenium catalysts were made. |
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| Keywords: | Chiral terpyridine Copper Rhodium Ruthenium Metal-catalyzed cyclopropanation Asymmetric catalysis |
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