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Trans Effect of Different Coordinated Atoms of Planar Chiral Ferrocene Ligands with the Same Backbone in Palladium−Catalyzed Allylic Substitutions

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posted on 15.02.2003, 00:00 authored by Tao Tu, Yong-Gui Zhou, Xue-Long Hou, Li-Xin Dai, Xi-Cheng Dong, Yi-Hua Yu, Jie Sun
A series of planar chiral P,S-, P,(CN)-, and S,(CN)-bidentate ferrocenyl ligands 4, 5, 8, and 9 with the same central and planar chiralities were prepared from the commercially available starting material N,N-dimethyl-(S)-α-ferrocenylethylamine. A Pd-catalyzed asymmetric allylic alkylation reaction was used as a model reaction to study the trans effect of the coordination atoms by these ligands. On the basis of the reaction results and the study of X-ray diffraction as well as 1H and 13C NMR spectra of the complexes (1215), the sequence of the trans effect was established as CN > P > S, which was supported by molecular modeling at the PM3 level.