Y. Chounan et al., 1,2-asymmetric induction in the conjugate addition of organocopper reagents to gamma-aryl alpha,beta-unsaturated carbonyl derivatives, TETRAHEDRON, 56(18), 2000, pp. 2821-2831
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.