title: Formation of quaternary stereogenic centers by copper-catalyzed asymmetric conjugate addition reactions of alkenylaluminums to trisubstituted enones.
abstract: Alkenylaluminums undergo asymmetric copper-catalyzed conjugate addition (ACA) to β-substituted enones allowing the formation of stereogenic all-carbon quaternary centers. Phosphinamine-copper complexes proved to be particularly active and selective compared with phosphoramidite ligands. After extensive optimization, high enantioselectivities (up to 96% ee) were obtained for the addition of alkenylalanes to β-substituted enones. Two strategies for the generation of the requisite alkenylaluminums were explored allowing for the introduction of aryl- and alkyl-substituted alkenyl nucleophiles. Moreover, alkyl-substituted phosphinamine (SimplePhos) ligands were identified for the first time as highly efficient ligands for the Cu-catalyzed ACA.
authors.affiliation: Department of Organic Chemistry, University of Geneva, Quai Ernest Ansermet 30, 1211 Genève 4 (Switzerland).
authors.forename: Daniel
authors.initials: D
authors.lastname: Müller
authors.forename: Alexandre
authors.initials: A
authors.lastname: Alexakis
keywords: aluminum; asymmetric synthesis; conjugate addition; copper; phosphorous