1,2-Asymmetric Induction in the Conjugate Addition of Organocopper Reagents to γ-Aryl α,β-Unsaturated Carbonyl Derivatives

The diastereoselectivity in the conjugate addition of organocopper reagents to γ-aryl α,β-unsaturated carbonyl derivatives 8–14 was investigated. The syn-diastereoselectivity was obtained irrespective of the reagents type in the addition of 8, while the anti-diastereoselectivity was obtained in the addition of 10–14 with RCu and RCu(CN)Li (R=Me and Bu) and the syn-selectivity was produced in the addition of 10–14 with R2CuLi and R2Cu(CN)Li2. The reagent controlled and substrate dependent diastereoselectivity are explained by two different reaction pathways: either π-complex formation or ordinary nucleophilic addition. Reduction potentials of the Michael acceptors and electron donating ability of organocopper reagents control the reaction pathway.