Ruthenium-catalyzed asymmetric epoxidation of olefins using H 2O2, part I: Synthesis of new chiral N,N,N,-tridentate pybox and pyboxazine ligands and their ruthenium complexes

Man Kin Tse, Santosh Bhor, Markus Klawonn, Gopinathan Anilkumar, Haijun Jiao, Christian Döbler, Anke Spannenberg, Wolfgang Magerlein, Herbert Hugl, Matthias Beller

Research output: Contribution to journalArticlepeer-review

91 Scopus citations

Abstract

The synthesis of chiral tridentate N,N,N-pyridine-2.6-bisoxazolines 3 (pyhox ligands) and N,N,N-pyridine-2.6-bisoxazines 4 (pyboxazine ligands) is described in detail. These novel ligands constitute a useful tool-box for the application in asymmetric catalysis. Compounds 3 and 4 are conveniently prepared by cyclization of enantiomerically pure α- or β-amino al cohols with dimethyl pyridine-2,6-dicarboximidate. The corresponding ruthenium complexes are efficient asymmetric epoxidation catalysts and have been prepared in good yield and fully char acterized 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)-2aa, is presented.

Original languageEnglish
Pages (from-to)1855-1874
Number of pages20
JournalChemistry - A European Journal
Volume12
Issue number7
DOIs
StatePublished - 20 Feb 2006
Externally publishedYes

Keywords

  • Epoxidation
  • Homogeneous catalysis
  • N ligands
  • Olefins
  • Ruthenium

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