- Convenient and Multistep Preparation of Oligopyridines Bearing Multiple Dansyl and Nitroxide Radicals
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A series of pyridine and bipyridine molecules combining dual fluorescent (dansyl) and magnetic (free radical) probes has been prepared by a linear multistep protocol from the corresponding monodansylated derivatives. The grafting of the flexible aliphatic radical is realized by the use of a chloromethylnitronyl nitroxide derivative under basic conditions and with KI as a mediator. The synthetic potential of 2-[(5-dimethylamino-1-naphthalenesulfonamide)methyl]-6-formylpyridine is assessed by the construction, in a first step, of an aliphatic nitroxide radical and subsequently of an additional aromatic radical. The synthetic methods reported herein provide a practical approach to the rational design of ligands bearing various kinds of functionalities such as chromogenic and spinlabeled fragments. A significant merit of this method is that it allows the introduction of the fluorescent substituent onto the pyridine or bipyridine framework at the beginning of the synthetic protocol.
- Ziessel, Raymond,Stroh, Christophe
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- Improved synthesis of a C3-symmetrical pyridinophane
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The formation of the C3-symmetrical 2,11,20-triaza[3.3.3](2,6)pyridinophane 1 was undertaken with the aim of improving the synthesis of this highly desirable macrocycle, with the future aim of functionalizing 1 with amide pendent arms for the recognition of lanthanide ions. The synthesis of 1 involves the stepwise transformation of pyridine-2,6-dicarboxylic acid into two key intermediates; N,N-bis[(6-hydroxymethyl)pyridin-2-yl]-p-tosylamide 7 and 6-bis[(amino-p-tosyl)methyl]pyridine 5. The macrocyclization of these two intermediates gave 8, from which 1 was formed upon deprotection of the three tosyl groups.
- Nolan, Claire,Gunnlaugsson, Thorfinnur
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p. 1993 - 1996
(2008/09/19)
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- Syntheses of zinc complexes with multidentate nitrogen ligands: New catalysts for aldol reactions
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The ligands 2,6-bis{[(pyrid-2-ylmethyl)amino]methyl}-pyridine with an N5 pattern and (6-{[(pyrid-2-ylmethyl)amino]methyl}pyrid-2-yl)methanol with an N3O pattern were synthesized. ZnII complexes of the two ligands could be obtained, and the single-crystal X-ray structure of (2,6-bis{[(pyrid-2-ylmethyl)amino]methyl}pyridine)zinc chloride showed Zn coordination to all five nitrogen atoms. The strong complexation of 2,6-bis{[(pyrid-2-ylmethyl)-amino]methyl}pyridine and (6-{[(pyrid-2-ylmethyl)amino]-methyl}pyrid-2-yl)methanol with ZnII were demonstrated by 1H NMR spectroscopic studies and electrospray mass spectrometry. The coupling of 2-hydroxyacetophenone and benzaldehyde was studied in the presence of the prepared Zn complexes, and it was shown that the coupling product was obtained at room temperature in up to 60% yield with 7.5 mol% of the zinc catalyst. The present complexes mimic the active site of the zinc-dependent class II aldolases, where ZnII is coordinated to three nitrogen atoms. Wiley-VCH Verlag GmbH, 69451 Weinheim, Germany, 2002.
- Darbre, Tamis,Dubs, Christian,Rusanov, Eduard,Stoeckli-Evans, Helen
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p. 3284 - 3291
(2007/10/03)
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- Synthesis and Coordinating Properties of Ligands Designed for Modeling of the Active Site Zinc of Liver Alcohol Dehydrogenase
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Some tridentate ligands have been prepared for coordination of zinc(II) ions (or cobalt(II), which acts as a surrogate for Zn(II) ions) in a manner analogous to the coordination found in liver alcohol dehydrogenase.This entails coordination of the metal ion to two thiolates and an imidazole.The ligands must be sufficiently sterically hindered to prevent thiolate from acting as a bridging ligand between two metal ions.For some aspects of this work pyridine was used instead of imidazole.A trisubstituted benzene derivative, 3,5-bis(3-mercaptopropoxy)-N-benzamide (7) was prepared.Zn(II) complexes with 7 could not be characterized but the Co(II) complexes showed excellent spectral correlation with liver alcohol dehydrogenase in which Zn(II) has been replaced by Co(II).Several analogues of 7 have also been synthesized.Another ligand, 2,6-bispyridine (17), does provide a monomeric Zn(II) complex.The synthesis and coordination of various analogues of this system have been examined.The bis-alcohol, 2,6-bis(2-methyl-2-hydroxypropyl)pyridine (24), gives a stable pentacoordinate complex with Zn(NO3)2 and two water molecules.
- Kaptein, Bernard,Barf, G.,Kellogg, Richard M.,Bolhuis, F. Van
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p. 1890 - 1901
(2007/10/02)
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