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Influence of the Conformation of Salen Complexes on the Stereochemistry of the Asymmetric Epoxidation of Olefins
Author(s) -
Scheurer Andreas,
Maid Harald,
Hampel Frank,
Saalfrank Rolf W.,
Toupet Loic,
Mosset Paul,
Puchta Ralph,
van Eikema Hommes Nico J. R.
Publication year - 2005
Publication title -
european journal of organic chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.825
H-Index - 155
eISSN - 1099-0690
pISSN - 1434-193X
DOI - 10.1002/ejoc.200500042
Subject(s) - chemistry , diimine , catalysis , nickel , ligand (biochemistry) , manganese , stereochemistry , nmr spectra database , medicinal chemistry , crystallography , polymer chemistry , spectral line , organic chemistry , biochemistry , physics , receptor , astronomy
Compared with Katsuki’s or Jacobsen’s catalysts ( R , R , R , R )‐ 1 or ( R , R )‐ 2 , the phenomenon of reversed asymmetric induction in the course of the epoxidation of unfunctionalised olefins in the presence of (salen) manganese complex ( S , S )‐ 3 is indirectly explained by means of quantumchemical calculations, as well as by 1 H NMR spectra of salen ligand ( S , S )‐ 10 and diamagnetic low‐spin nickel complex ( S , S )‐ 7 and by its X‐ray structure analysis. Whereas in ( R , R , R , R )‐ 1 and ( R , R )‐ 2 the phenyl and cyclohexyl substituents occupy equatorial positions, the origin for the reversed enantioselection caused by manganese catalyst ( S , S )‐ 3 , is based on an axial position of the acyclic heteroalkyl substituents in the diimine backbone of ( S , S )‐ 3 as exemplarily confirmed by model nickel complex ( S , S )‐ 7 . (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2005)
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