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Chiral manganese complexes with pinene appended tetradentate ligands as stereoselective epoxidation catalysts

A novel family of chiral manganese complexes Λ-1(CF 3SO3) and Δ-2(CF3SO3), have been stereoselectively prepared, characterized and studied as epoxidation catalysts. The complexes are structurally related to [MnII(CF 3SO3)2(α-MCP)] (MCP = N,N′-dimethyl-N,N′-bis(2-pyridylmethyl)cyclohexane-trans-1, 2-diamine), recently reported as a very efficient epoxidation catalyst in combination with peracetic acid. Pinene rings have been fused to the 4 and 5 positions of the two pyridine groups of the ligand, giving rise to complexes where the two labile binding sites of the manganese ion are confined in a better-defined chiral pocket than in the parent [MnII(CF 3SO3)2(α-MCP)]. Chirality in these complexes arises from the stereochemistry of the trans-diaminocyclohexane ring, from the pinene ring and also from the topological chirality adopted by the ligand upon binding to the manganese ion. While previous studies have demonstrated that small modifications in the structure of the MCP ligand result in a dramatic loss of efficiency, Λ-1(CF3SO3) and Δ-2(CF3SO3) exhibit comparable catalytic activity to [MnII(CF3SO3)2(α-MCP)]. In addition, the complexes exhibit a remarkable stereoselectivity (up to 46% ee) in the epoxidation of selected substrates. The results reported in this work point towards modification of the 4 and 5 positions of the pyridine groups as a new strategy towards the design of stereoselective versions of this family of highly active and environmentally benign epoxidation catalysts

We acknowledge financial support by MCYT of Spain through projects CTQ2006–05367/BQU to MC. LG, IG-B and AC thank MEC for PhD grants

© Dalton Transactions, 2007, vol. 47, 5539-5545

Royal Society of Chemistry (RSC)

Manager: Ministerio de Educación y Ciencia (Espanya)
Author: Gómez Martín, Laura
Garcia Bosch, Isaac
Company Casadevall, Anna
Sala Román, Xavier
Fontrodona, Xavier
Ribas Salamaña, Xavi
Costas Salgueiro, Miquel
Date: 2007 December 4
Abstract: A novel family of chiral manganese complexes Λ-1(CF 3SO3) and Δ-2(CF3SO3), have been stereoselectively prepared, characterized and studied as epoxidation catalysts. The complexes are structurally related to [MnII(CF 3SO3)2(α-MCP)] (MCP = N,N′-dimethyl-N,N′-bis(2-pyridylmethyl)cyclohexane-trans-1, 2-diamine), recently reported as a very efficient epoxidation catalyst in combination with peracetic acid. Pinene rings have been fused to the 4 and 5 positions of the two pyridine groups of the ligand, giving rise to complexes where the two labile binding sites of the manganese ion are confined in a better-defined chiral pocket than in the parent [MnII(CF 3SO3)2(α-MCP)]. Chirality in these complexes arises from the stereochemistry of the trans-diaminocyclohexane ring, from the pinene ring and also from the topological chirality adopted by the ligand upon binding to the manganese ion. While previous studies have demonstrated that small modifications in the structure of the MCP ligand result in a dramatic loss of efficiency, Λ-1(CF3SO3) and Δ-2(CF3SO3) exhibit comparable catalytic activity to [MnII(CF3SO3)2(α-MCP)]. In addition, the complexes exhibit a remarkable stereoselectivity (up to 46% ee) in the epoxidation of selected substrates. The results reported in this work point towards modification of the 4 and 5 positions of the pyridine groups as a new strategy towards the design of stereoselective versions of this family of highly active and environmentally benign epoxidation catalysts
We acknowledge financial support by MCYT of Spain through projects CTQ2006–05367/BQU to MC. LG, IG-B and AC thank MEC for PhD grants
Format: application/pdf
Citation: 008158
ISSN: 1477-9226 (versió paper)
1477-9234 (versió electrònica)
Document access: http://hdl.handle.net/10256/12718
Language: eng
Publisher: Royal Society of Chemistry (RSC)
Collection: MEC/PN 2006-2009/ CTQ2006- 05367/BQU
Reproducció digital del document publicat a: http://dx.doi.org/10.1039/b712754e
Articles publicats (D-Q)
Is part of: © Dalton Transactions, 2007, vol. 47, 5539-5545
Rights: Tots els drets reservats
Subject: Epòxids
Epoxy compounds
Catalitzadors
Catalysts
Manganès -- Compostos -- Oxidació
Manganese compounds -- Oxidation
Title: Chiral manganese complexes with pinene appended tetradentate ligands as stereoselective epoxidation catalysts
Type: info:eu-repo/semantics/article
Repository: DUGiDocs

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