Novel Chiral (Salen)Mn III Complexes Containing a Calix[4]arene Unit as Catalysts for Enantioselective Epoxidation Reactions of ( Z )‐Aryl Alkenes

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...

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Published in:European journal of organic chemistry 2005-08, Vol.2005 (16), p.3562-3570
Main Authors: Amato, Maria E., Ballistreri, Francesco P., Pappalardo, Andrea, Tomaselli, Gaetano A., Toscano, Rosa M., Williams, David J.
Format: Article
Language:English
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Summary: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)
ISSN:1434-193X
1099-0690
DOI:10.1002/ejoc.200500138