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Issue 17, 2013
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Conformational analysis and synthetic approaches to polydentate perhydro-diazepine ligands for the complexation of gallium(III)

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Abstract

Synthetic approaches are reported to polydentate ligands based on 6-phenyl-6-amino-perhydro-1,4-diazepine. The synthetic route devised averts ring-opening reactions, allowing the exocyclic N-substituent to be introduced separately and involves a nitro-Mannich condensation, prior to chemoselective RANEY® nickel reduction. Comparison of the solid-state structures of four synthetic intermediates reveals that the seven-membered ring adopts a preferred twist-chair conformer in the solid state. Solution state NMR experiments highlight a conformational preference for the bulky aryl groups to adopt an equatorial site, pre-disposing the ligand to metal binding, by adoption of a conformation that creates a facial array of the ligand nitrogen atoms. This ligand conformation averts the formation of less stable metal complexes with differing ligation modes, notably in the binding of Ga3+ to related ligands, where a C-methyl substituent replaces the phenyl group at the quaternary centre.

Graphical abstract: Conformational analysis and synthetic approaches to polydentate perhydro-diazepine ligands for the complexation of gallium(iii)

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Publication details

The article was received on 07 Feb 2013, accepted on 06 Mar 2013 and first published on 06 Mar 2013


Article type: Paper
DOI: 10.1039/C3OB40287H
Citation: Org. Biomol. Chem., 2013,11, 2827-2838
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    Conformational analysis and synthetic approaches to polydentate perhydro-diazepine ligands for the complexation of gallium(III)

    D. Parker and B. P. Waldron, Org. Biomol. Chem., 2013, 11, 2827
    DOI: 10.1039/C3OB40287H

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