- Improved synthesis of symmetrically & asymmetrically: N -substituted pyridinophane derivatives
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The N,N′-di(toluenesulfonyl)-2,11-diaza[3,3](2,6)pyridinophane (TsN4) precursor was sought after as a starting point for the preparation of various symmetric and asymmetric pyridinophane-derived ligands. Various procedures to synthesize TsN4 had been published, but the crucial problem had been the purification of TsN4 from the larger 18- and 24-membered azamacrocycles. Most commonly, column chromatography or other laborious methods have been utilized for this separation, yet we have found an alternate selective dissolution method upon protonation which allows for multi-gram scale output of TsN4·HCl. This optimized synthesis of TsN4 also led to the development of symmetric RN4 derivatives as well as the asymmetric derivative N-(tosyl)-2,11-diaza[3,3](2,6)pyridinophane (TsHN4). Using this TsHN4 precursor, different N-substituents can be added to create a library of asymmetric RR′N4 macrocyclic ligands. These asymmetric RR′N4 derivatives expand the utility of the RN4 framework in coordination chemistry and the ability to study the electronic, steric, and denticity effects of these pyridinophane ligands on the metal center.
- Wessel, Andrew J.,Schultz, Jason W.,Tang, Fengzhi,Duan, Hui,Mirica, Liviu M.
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p. 9923 - 9931
(2017/12/12)
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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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- Reaction of Tosylamide Monosodium Salt with Bis(halomethyl) Compounds: An Easy Entry to Symmetrical N-Tosyl Aza Macrocycles
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A one-step, general procedure for a variety of N-tosyl aza macrocycles (including aza-crown ethers, pyridino- and bipyridino-aza-crown analogues, and azacyclophanes), by reaction of appropriate bis(halomethyl) precursors with tosylamide monosodium salt (TsNHNa) in N,N-dimethylformamide, is described.In polymethyl-substituted 2,11-diazacyclophane systems, the methyl substituents play an important role in inducing stereospecific ring closures.Thus, coupling of 1,4-bis(chloromethyl)-2,5-dimethylbenzene (15b) with TsNHNa produced only one of the two possible diastereomeric dimers, to which chiral structure 16db was assigned by means of the chiral Eu(dcm)3 shift reagent.This stereochemical assignment was confirmed by a single-crystal X-ray study on 16d.Detosylation of N-tosyl aza macrocycles to the free polyamino macrocycles by reductive (Na-NH3) or hydrolytic (90percent H2SO4) methods, followed by N-methylation (CH2O-HCO2H), was also accomplished in excellent yield.The 1H NMR spectra of 2,11-diazacyclophanes and 2,11-diaza(2,6)pyridinophanes are discussed in terms of conformation and conformational mobility.
- Bottino, Francesco,Grazia, Michele Di,Finocchiaro, Paolo,Fronczek, Frank R.,Mamo, Antonino,Pappalardo, Sebastiano
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p. 3521 - 3529
(2007/10/02)
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