Me3Al, Et3Al, and vinylalane species undergo enantioselective conjugate addition to a wide range of 2- or 3-substituted enones (cyclopent-2-enones, cyclohex-2-enones, 3-methyl cyclohept-2-enone) in the presence of catalytic amount of copper salt (copper thiophene carboxylate, [Cu(CH3CN)4]BF4 or [CuOTf]2C6H6) and tropos-phosphoramidite-based ligand. Thus, chiral quaternary centers can be built, with up to 98% ee after rigorous optimization of experimental conditions. It was shown that the main important parameter was the order of the introduction of the reagents. Then, the generated enantioenriched aluminium enolates and the chiral conjugate adducts were functionalized and used for subsequent reactions.

The design of chiral ligands is the key to attaining high asymmetric induction in transition-metal-catalyzed reactions. Subtle changes in the conformational, steric, and/or electronic properties of the chiral ligand can often lead to dramatic variation of the reactivity and enantioselectivity. As a result of strong substrate dependence in most cases, tunable and readily synthesized ligands are desirable to obtain high enantioselectivities.Nowadays, asymmetric copper-catalyzed conjugate addition and allylic substitution are well-developed methodologies for creating CÀC bonds. Many efforts have been made in designing efficient systems and identifying new ligands to improve enantioselectivities.

The design of chiral ligands is the key to attaining high asymmetric induction in transition-metal-catalyzed reactions. Subtle changes in the conformational, steric, and/or electronic properties of the chiral ligand can often lead to dramatic variation of the reactivity and enantioselectivity. As a result of strong substrate dependence in most cases, tunable and readily synthesized ligands are desirable to obtain high enantioselectivities.Nowadays, asymmetric copper-catalyzed conjugate addition and allylic substitution are well-developed methodologies for creating CÀC bonds. Many efforts have been made in designing efficient systems and identifying new ligands to improve enantioselectivities.

Keywords: Michael addition / Asymmetric catalysis / Diethylzinc / Copper / Double-bond geometry Focusing on mechanistic aspects, a study of the influence of the (E)/(Z) double-bond geometry of the Michael acceptor on the enantioselectivity of copper-catalyzed asymmetric conjugate addition reactions has been realized. In spite of numerous articles concerning copper-catalyzed asymmetric conjugate addition reactions, the major factors of such a reaction are quite difficult to elucidate. Although our experiments have not allowed us to define strict rules, they have high-

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