title: Ruthenium-catalyzed asymmetric epoxidation of olefins using H2O2, part I: synthesis of new chiral N,N,N-tridentate pybox and pyboxazine ligands and their ruthenium complexes.
abstract: The synthesis of chiral tridentate N,N,N-pyridine-2,6-bisoxazolines 3 (pybox ligands) and N,N,N-pyridine-2,6-bisoxazines 4 (pyboxazine ligands) is described in detail. These novel ligands constitute a useful toolbox for the application in asymmetric catalysis. Compounds 3 and 4 are conveniently prepared by cyclization of enantiomerically pure alpha- or beta-amino alcohols with dimethyl pyridine-2,6-dicarboximidate. The corresponding ruthenium complexes are efficient asymmetric epoxidation catalysts and have been prepared in good yield and fully characterized by spectroscopic means. Four of these ruthenium complexes have been characterized by X-ray crystallography. For the first time the molecular structure of a pyboxazine complex [2,6-bis-[(4S)-4-phenyl-5,6-dihydro-4H-[1,3]oxazinyl]pyridine](pyridine-2,6-dicarboxylate)ruthenium (S)-2 aa, is presented.
authors.affiliation: Leibniz-Institut für Organische Katalyse an der Universität Rostock e.V. Albert-Einstein-Strasse 29a, 18059 Rostock (Germany).
authors.forename: Man Kin
authors.initials: MK
authors.lastname: Tse
authors.forename: Santosh
authors.initials: S
authors.lastname: Bhor
authors.forename: Markus
authors.initials: M
authors.lastname: Klawonn
authors.forename: Gopinathan
authors.initials: G
authors.lastname: Anilkumar
authors.forename: Haijun
authors.initials: H
authors.lastname: Jiao
authors.forename: Christian
authors.initials: C
authors.lastname: Döbler
authors.forename: Anke
authors.initials: A
authors.lastname: Spannenberg
authors.forename: Wolfgang
authors.initials: W
authors.lastname: Mägerlein
authors.forename: Herbert
authors.initials: H
authors.lastname: Hugl
authors.forename: Matthias
authors.initials: M
authors.lastname: Beller