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Ruthenium‐Catalyzed Asymmetric Epoxidation of Olefins Using H 2 O 2 , Part II: Catalytic Activities and Mechanism
Author(s) -
Tse Man Kin,
Bhor Santosh,
Klawonn Markus,
Anilkumar Gopinathan,
Jiao Haijun,
Spannenberg Anke,
Döbler Christian,
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.200501262
Subject(s) - ruthenium , catalysis , chemistry , pyridine , reactivity (psychology) , steric effects , solvent , density functional theory , medicinal chemistry , reaction mechanism , organic chemistry , computational chemistry , medicine , alternative medicine , pathology
Asymmetric epoxidation of olefins with 30 % H 2 O 2 in the presence of [Ru(pybox)(pydic)] 1 and [Ru(pyboxazine)(pydic)] 2 has been studied in detail (pybox=pyridine‐2,6‐bisoxazoline, pyboxazine=pyridine‐2,6‐bisoxazine, pydic=2,6‐pyridinedicarboxylate). 35 Ruthenium complexes with sterically and electronically different substituents have been tested in environmentally benign epoxidation reactions. Mono‐, 1,1‐di‐, cis ‐ and trans ‐1,2‐di‐, tri‐, and tetra‐substituted aromatic olefins with versatile functional groups can be epoxidized with this type of catalyst in good to excellent yields (up to 100 %) with moderate to good enantioselectivies (up to 84 % ee ). Additive and solvent effects as well as the relative rate of reaction with different catalysts have been established. It is shown that the presence of weak organic acids or an electron‐withdrawing group on the catalyst increases the reactivity. New insights on the reaction intermediates and reaction pathway of the ruthenium‐catalyzed epoxidation are proposed on the basis of density functional theory calculation and experiments.