Synthesis of highly hindered polyanionic chelating ligands

Jiménez, Claudio A.; Belmar, J.

doi:10.1016/j.tet.2005.02.064

Cited by 14 publications

(15 citation statements)

References 34 publications

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“…LH (Scheme 1) are readily synthesised in high yield [16] by the condensation of the corresponding amine, HNRR', onto succinimide-activated 3,5-ditert-butyl salicylic acid. The deprotonation of the phenol moiety by using an equimolar amount of OHA C H T U N G T R E N N U N G [NBu 4 ] yields the corresponding phenolate salt,…”

Section: Resultsmentioning

confidence: 99%

Persistent Hydrogen‐Bonded and Non‐Hydrogen‐Bonded Phenoxyl Radicals

Wanke¹,

Bénisvy

Kuznetsov³

et al. 2011

Chemistry A European J

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The production of stable phenoxyl radicals is undoubtedly a synthetic chemical challenge. Yet it is a useful way to gain information on the properties of the biological tyrosyl radicals. Recently, several persistent phenoxyl radicals have been reported, but only limited synthetic variations could be achieved. Herein, we show that the amide-o-substituted phenoxyl radical (i.e. with a salicylamide backbone) can be synthesised in a stable manner, thereby permitting easy synthetic modifications to be made through the amide bond. To study the effect of H-bonding on the properties of the phenolate/phenoxyl radical redox couple, simple H-bonded and non-H-bonded o,p-tBu-protected salicylamidate compounds have been prepared. Their redox properties were examined by cyclic voltammetry and showed a fully reversible one-electron oxidation process to the corresponding phenoxyl radical species. Remarkably, the redox potential appears to be correlated, at least partially, with H-bond strength, as relatively large differences (ca. 300 mV) in the redox potential between H-bonded and non-H-bonded phenolate salts are observed. The corresponding phenoxyl radicals produced electrochemically are persistent at room temperature for at least an hour; their UV/Vis and EPR characterisation is consistent with that of phenoxyl radicals, which makes them excellent models of biological tyrosyl radicals. The analyses of the experimental data coupled with theoretical calculations indicate that both the deviation from planarity of the amide function and intramolecular H-bonding influence the oxidation potential of the phenolate. The latter H-bonding effect appears to be predominantly exerted on the phenolate and not (or only a little) on the phenoxyl radical. Thus, in these systems the H-bonding energy involved in the phenoxyl radical appears to be relatively small.

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Section: Resultsmentioning

confidence: 99%

Persistent Hydrogen‐Bonded and Non‐Hydrogen‐Bonded Phenoxyl Radicals

Wanke¹,

Bénisvy

Kuznetsov³

et al. 2011

Chemistry A European J

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“…Synthesis of NRR′ LH and [ NRR′ L][NBu 4 ] : The phenols NRR′ LH (Scheme ) are readily synthesised in high yield16 by the condensation of the corresponding amine, HNRR′, onto succinimide‐activated 3,5‐di‐ tert ‐butyl salicylic acid. The deprotonation of the phenol moiety by using an equimolar amount of OH[NBu 4 ] yields the corresponding phenolate salt, [ NRR′ L][NBu 4 ].…”

Section: Resultsmentioning

confidence: 99%

Anionic ring‐opening polymerization of adipic anhydride initiated by potassium poly(ethylene glycol)ate

Deng

Yuan

et al. 2003

J of Applied Polymer Sci

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Poly(adipic anhydride) (PAA) was prepared by the ring-opening polymerization of adipic anhydride (AA) initiated by potassium poly(ethylene glycol)ate. The effects of various factors, such as the amount of initiator, concentration of the monomer, reaction time and temperature, and polarity of the solvent on the polymerization were investigated. The crude polymerized product was a mixture of PAA homopolymer and poly(ethylene glycol)-poly(adipic anhydride) block copolymer, as confirmed by 1 H-NMR and gel permeation chromatography. Chain-transfer reactions occurred intensively for the AA polymerization in both the nonpolar solvent toluene and the polar solvents CHCl 3 and tetrahydrofuran, which predominantly determined the molecular weight and the monomer conversion for the polymerized product. The lower monomer conversion in toluene was ascribed to a lower livingness for the initiator in the nonpolar solvent when compared with other two, polar solvents.

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“…A similar type of reaction has been reported by Counsell and co-workers in the synthesis of di-substituted 1-phenol-2-propanones, 56 and by Belmar and Jiménez for preparing hindered polyanionic chelating ligands. 57 Crystals of 3 were grown from hexane by evaporation; the structure elucidated is shown in Figure 3. The benzene rings in each molecule are rotated perpendicular to one another.…”

Section: Pendent Arm Synthesismentioning

confidence: 99%

“…55 Catalytic hydrogenolysis could not be successfully employed as both N-benzylic and Obenzylic moieties are present, even though conditions similar to those reported for cleaving a benzyl group used to protect 2,4-di-tert-butyl phenol linked to an aromatic amine by an amide bond were employed. 57 A light-initiated process was also attempted. The rapid debenzylation of sterically hindered benzyl ethers is reported by Binkley and Hehemann, 63 which has been further developed by Riley and Grindley.…”

Section: Functionalised Azamacrocycle Synthesismentioning

confidence: 99%

Side-bridged cyclam transition metal complexes bearing a phenolic ether or a phenolate pendent arm

Mewis

Archibald

2019

Polyhedron

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Side-bridged cyclam transition metal complexes (M = Ni(II), Cu(II) and Zn(II)) bearing a phenolic ether or phenolate pendent arm have been synthesised. For [NiL 1 ] + and [CuL 1 ] + , evidence for a phenoxyl radical was obtained (quasi reversible peak at +0.74 V and +0.48 V respectively), as well as oxidation of OH, due to protonation of the phenolate, at ~+1.24 V. The phenoxyl radical in [Ni(L 1 )] 2+ is harder to oxidise by 0.26 V compared with the corresponding Cu(II) complex. UV-Vis data for [Ni(L 1 )] 2+ suggests that the Ni(II) ion may be 4 or 6 coordinate whereas the Cu(II) ion in [Cu(L 1 )] 2+ is five coordinate. The Ni(II) ion in the crystal structure of [Ni( L 2 )][( ClO4)2] possesses a distorted squareplanar geometry in which the phenolic ether pendent arm is not involved in the coordination sphere. The cyclam ligand in this complex adopts a trans-II configuration.

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Synthesis of highly hindered polyanionic chelating ligands

Cited by 14 publications

References 34 publications

Persistent Hydrogen‐Bonded and Non‐Hydrogen‐Bonded Phenoxyl Radicals

Persistent Hydrogen‐Bonded and Non‐Hydrogen‐Bonded Phenoxyl Radicals

Anionic ring‐opening polymerization of adipic anhydride initiated by potassium poly(ethylene glycol)ate

Side-bridged cyclam transition metal complexes bearing a phenolic ether or a phenolate pendent arm

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