title: Rational design of cyclopropane-based chiral PHOX ligands for intermolecular asymmetric Heck reaction.
abstract: A novel class of chiral phosphanyl-oxazoline (PHOX) ligands with a conformationally rigid cyclopropyl backbone was synthesized and tested in the intermolecular asymmetric Heck reaction. Mechanistic modelling and crystallographic studies were used to predict the optimal ligand structure and helped to design a very efficient and highly selective catalytic system. Employment of the optimized ligands in the asymmetric arylation of cyclic olefins allowed for achieving high enantioselectivities and significantly suppressing product isomerization. Factors affecting the selectivity and the rate of the isomerization were identified. It was shown that the nature of this isomerization is different from that demonstrated previously using chiral diphosphine ligands.
authors.affiliation: Department of Chemistry, University of Kansas, 1251 Wescoe Hall Drive, Lawrence, KS 66045-7582, USA.
authors.forename: Marina
authors.initials: M
authors.lastname: Rubina
authors.affiliation: Department of Chemistry, University of Kansas, 1251 Wescoe Hall Drive, Lawrence, KS 66045-7582, USA.
authors.forename: William M
authors.initials: WM
authors.lastname: Sherrill
authors.affiliation: Department of Chemistry, Ural Federal University, pr. Lenina 51, 620000 Ekaterinburg, Russian Federation.
authors.forename: Alexey Yu
authors.initials: AY
authors.lastname: Barkov
authors.affiliation: Department of Chemistry, University of Kansas, 1251 Wescoe Hall Drive, Lawrence, KS 66045-7582, USA.
authors.forename: Michael
authors.initials: M
authors.lastname: Rubin
keywords: Heck reaction; asymmetric catalysis; chiral phosphine ligands; cyclopropane; organophosphorus; transition metal catalysis