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Mass‐Spectrometric and Kinetic Studies on the Mechanism and Degradation Pathways of Titanium Salalen Catalysts for Asymmetric Epoxidation with Aqueous Hydrogen Peroxide
Author(s) -
Berkessel Albrecht,
Brandenburg Marc,
Schäfer Mathias
Publication year - 2008
Publication title -
advanced synthesis and catalysis
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.541
H-Index - 155
eISSN - 1615-4169
pISSN - 1615-4150
DOI - 10.1002/adsc.200700601
Subject(s) - chemistry , hydrogen peroxide , catalysis , aqueous solution , titanium , enantioselective synthesis , amine gas treating , hydroxylamine , ligand (biochemistry) , peroxide , 1 octene , chiral ligand , inorganic chemistry , photochemistry , organic chemistry , biochemistry , receptor , ethylene
The composition and degradation of a highly active and enantioselective titanium salalen in situ catalyst for the asymmetric epoxidation of olefins with aqueous hydrogen peroxide was investigated. Kinetic data and ESI‐MS studies point to a mononuclear titanium salalen as the catalytically active species. By means of ESI‐MS and selective monodeuteration of the salalen ligand, the oxidative degradation was studied. Upon exposure to aqueous hydrogen peroxide, the amine functionality of the salalen ligand is converted to the hydroxylamine, followed by loss of water and generation of the inactive titanium‐salen complex. This transformation limits the activity of the catalyst in the epoxidation of less electron‐rich olefins, such as 1‐octene.