10.1021/jo050097d.s001 Da-Ming Du Da-Ming Du Shao-Feng Lu Shao-Feng Lu Tao Fang Tao Fang Jiaxi Xu Jiaxi Xu Asymmetric Henry Reaction Catalyzed by <i>C</i><sub>2</sub>-Symmetric Tridentate Bis(oxazoline) and Bis(thiazoline) Complexes:  Metal-Controlled Reversal of Enantioselectivity American Chemical Society 2005 Lewis acid center C 2 Asymmetric Henry Reaction Catalyzed tridentate chiral ligands NH Enantioselectivity C 2 Reversal Bis enantiomer bi Cu Et 2 Zn complexes 2005-04-29 00:00:00 Journal contribution https://acs.figshare.com/articles/journal_contribution/Asymmetric_Henry_Reaction_Catalyzed_by_i_C_i_sub_2_sub_Symmetric_Tridentate_Bis_oxazoline_and_Bis_thiazoline_Complexes_Metal_Controlled_Reversal_of_Enantioselectivity/3288769 <i>C</i><sub>2</sub>-symmetric tridentate bis(oxazoline) and bis(thiazoline) ligands with a diphenylamine backbone have been investigated in the catalytic asymmetric Henry reaction of α-keto esters with different Lewis acids. Their Cu(OTf)<sub>2</sub> complexes furnished <i>S </i>enantiomers, while Et<sub>2</sub>Zn complexes afforded <i>R </i>enantiomers, both of them with higher enantioselectivities (up to 85% ee). Reversal of enantioselectivity in asymmetric Henry reactions was achieved with the same chiral ligand by changing the Lewis acid center from Cu(II) to Zn(II). The results show that the NH group in <i>C</i><sub>2</sub>-symmetric tridentate chiral ligands plays a very important role in controlling both the yields and enantiofacial selectivity of the Henry products.