title: Quinaphos and Dihydro-Quinaphos phosphine-phosphoramidite ligands for asymmetric hydrogenation.
abstract: New derivatives of the Quinaphos ligands and the related Dihydro-Quinaphos ligands based on the more flexible 1,2,3,4-tetrahydroquinoline backbone have been prepared and fully characterised. A general and straightforward separation protocol was devised, which allowed for the gram-scale isolation of the R(a),S(c) and S(a),R(c) diastereomers. These new phosphine-phosphoramidite ligands have been applied in the Rh-catalysed asymmetric hydrogenation of functionalised olefins with the achievement of excellent enantioselectivities (> or = 99%) in most cases and turnover frequency (TOF) values of up to > or = 20,000 h(-1). These results substantiate the practical utility of readily accessible Quinaphos-type ligands, which belong to the most active and selective category of ligands for Rh-catalysed hydrogenation known to date.
authors.affiliation: Institut für Technische und Makromolekulare Chemie, RWTH Aachen University, Worringerweg 1, 520274 Aachen, Germany.
authors.forename: Thomas
authors.initials: T
authors.lastname: Pullmann
authors.forename: Barthel
authors.initials: B
authors.lastname: Engendahl
authors.forename: Ziyun
authors.initials: Z
authors.lastname: Zhang
authors.forename: Markus
authors.initials: M
authors.lastname: Hölscher
authors.forename: Antonio
authors.initials: A
authors.lastname: Zanotti-Gerosa
authors.forename: Alan
authors.initials: A
authors.lastname: Dyke
authors.forename: Giancarlo
authors.initials: G
authors.lastname: Franciò
authors.forename: Walter
authors.initials: W
authors.lastname: Leitner