1,2-asymmetric induction in the conjugate addition of organocopper reagents to gamma-aryl alpha,beta-unsaturated carbonyl derivatives

The diastereoselectivity in the conjugate addition of organocopper reagents to gamma-aryl alpha,beta-unsaturated carbonyl derivatives 8-14 was investi gated. The syn-diastereoselectivity was obtained irrespective of the reagen ts type in the addition of 8, while the anti-diastereoselectivity was obtai ned in the addition of 10-14 with RCu and RCu(CN)Li (R=Me and Bu) and the s yn-selectivity was produced in the addition of 10-14 with R2CuLi and R2Cu(C N)Li-2. The reagent controlled and substrate dependent diastereoselectivity are explained by two different reaction pathways: either pi-complex format ion or ordinary nucleophilic addition. Reduction potentials of the Michael accepters and electron donating ability of organocopper reagents control th e reaction pathway. (C) 2000 Elsevier Science Ltd. All rights reserved.