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Ruthenium‐Catalyzed Asymmetric Epoxidation of Olefins Using H 2 O 2 , Part I: Synthesis of New Chiral N , N , N ‐Tridentate Pybox and Pyboxazine Ligands and Their Ruthenium Complexes
Author(s) -
Tse Man Kin,
Bhor Santosh,
Klawonn Markus,
Anilkumar Gopinathan,
Jiao Haijun,
Döbler Christian,
Spannenberg Anke,
Mägerlein Wolfgang,
Hugl Herbert,
Beller Matthias
Publication year - 2006
Publication title -
chemistry – a european journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.687
H-Index - 242
eISSN - 1521-3765
pISSN - 0947-6539
DOI - 10.1002/chem.200501261
Subject(s) - ruthenium , pyridine , catalysis , chemistry , yield (engineering) , enantioselective synthesis , medicinal chemistry , stereochemistry , organic chemistry , materials science , metallurgy
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 α‐ or β‐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‐4 H ‐[1,3]oxazinyl]pyridine}(pyridine‐2,6‐dicarboxylate)ruthenium ( S) ‐ 2 aa , is presented.