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Novel Chiral (Salen)Mn III Complexes Containing a Calix[4]arene Unit as Catalysts for Enantioselective Epoxidation Reactions of ( Z )‐Aryl Alkenes
Author(s) -
Amato Maria E.,
Ballistreri Francesco P.,
Pappalardo Andrea,
Tomaselli Gaetano A.,
Toscano Rosa M.,
Williams David J.
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.200500138
Subject(s) - chemistry , selectivity , catalysis , calixarene , enantioselective synthesis , aryl , crystal structure , ligand (biochemistry) , stereochemistry , medicinal chemistry , molecule , crystallography , organic chemistry , biochemistry , alkyl , receptor
New asymmetric (salen)Mn III and UO 2 complexes containing a calix[4]arene unit in the ligand framework were synthesized. The UO 2 complexes were characterized by 1 H‐, 13 C‐, 2D TOCSY and T‐ROESY NMR spectroscopy. Furthermore, the structure of one UO 2 complex was determined by single‐crystal X‐ray analysis. The data showed that UO 2 complexes, which can be considered in first approximation models of the Mn=O oxidant active species, possess a chiral pocket and adopt relevant conformations for the selectivity of the oxygen transfer process. Epoxidation data of model alkenes with the Mn III complexes showed moderate ee values and were not conclusive in indicating that the calix[4]arene unit might be able to influence the selectivity by a molecular recognition mechanism. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2005)