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Several new derivatives of 2,2′‐bipyridines with a spacer group separated from the 2,2‐bipyridine fragment, namely, an ethynyl fragment, were obtained using the Sonagashira cross‐coupling reaction. The resulting derivatives were physically adsorbed on platinum electrode and were then used as activators of the catalytic activity of a platinum electrode in the reaction of cholesterol electrooxidation in an acetonitrile medium. Sensitivity, limit of detection and detectable concentration range were calculated, and the best results was established as 6.2±0.6 μA/mM, 0.08 mM and 0–0.3 mM, respectively. These results show that the prepared compounds adsorbed on platinum electrode are perspective systems for developing of new enzymeless cholesterol sensor based on them. [ABSTRACT FROM AUTHOR]

A solvent‐free reaction between C6‐unsubstituted 5‐aryl‐1,2,4‐triazines and 2‐amino‐4‐aryloxazoles at high temperature was studied. The reaction proceeds via inverse electron demand aza‐Diels‐Alder reaction between the oxazole moiety as dienophile and the 1,2,4‐triazine moiety as diene with the highly regioselective formation of 3,6‐diarylpyridines in up to 60 % isolated yield. The structure of one of the key‐products was proven by the X‐ray diffraction analysis, and the mechanism of the transformation was proposed. The reaction proceeds well for both 6‐aryl and 6‐hetaryl‐1,2,4‐triazines in the presence of the electron acceptor substituent at the position 3. In the case of the donor substituent in position 3, the pyridine yields are significantly reduced. In the case of 5,6‐nonsubstituted 1,2,4‐triazines, the triazine cycle is degraded without product formation. The high regioselectivity of the reaction as well as solvent‐free conditions are valuable advantages of the present synthetic approach. [ABSTRACT FROM AUTHOR]

Abstract: An efficient approach for the synthesis of 5,5' - or 5,6,5' -aryl substituted 2,2':6',2' -terpyridines, bearing an anneleted cyclopentene unit in one of the side-chain pyridine rings for the [...]

New Tb(III) and Eu(III) complexes based on aryl-2,2′-bipyridine ligands with a cyclic DO3A chelating unit appended in the alpha position of the bipyridine core were synthesized. The photophysical properties of these complexes were compared with those of complexes of ligands with identical aryl-2,2′-bipyridine chromophores, but with an acyclic DTTA residue as an additional chelating site in the alpha position of the bipyridine core. The nature of the polyaminocarboxylic acid fragments was found to have a significant influence on the luminescence. For some of the Eu(III) complexes, upon the transition from acyclic DTTA- to the cyclic DO3A-appended ligands, a noticeable increase in the intensity of Eu(III) luminescence was observed, with an increase in the quantum yield of up to 2.55 times. In contrast, for most of the Tb(III) complexes, a similar transition resulted in a noticeable decrease in the luminescence intensity of the Tb(III) cation. [ABSTRACT FROM AUTHOR]

Linked to Alzheimer's disease (AD), amyloids and tau-protein are known to contain a large number of cysteine (Cys) residues. In addition, certain levels of some common biogenic thiols (cysteine (Cys), homocysteine (Hcy), glutathione (GSH), etc.) in biological fluids are closely related to AD as well as other diseases. Therefore, probes with a selective interaction with the above-mentioned thiols can be used for the monitoring and visualizing changes of (bio)thiols in the biological fluids as well as in the brain of animal models of Alzheimer's disease. In this study, new Eu(III), Tb(III), Gd(III) and Sm(III) complexes of 2,2′-bipyridine ligands containing TEMPO fragments as receptor units for (bio)thiols are reported. The presence of free radical fragments of the ligand in the complexes was proved by using the electronic paramagnetic resonance (EPR) method. Among all the complexes, the Eu(III) complex turned out to be the most promising one as luminescence- and spin-probe for the detection of biogenic thiols. The EPR and fluorescent titration methods showed the interaction of the resulting complex with free Cys and GSH in solution. To study the practical applicability of the probes for the monitoring of AD in-vivo, by using the above-mentioned Eu(III)-based probe, the staining of the brain of mice with amyloidosis and Vero cell cultures supplemented with the cysteine-enriched medium was studied as well as the fluorescence titration of Bovine Serum Albumin, BSA (as the model for the thiol moieties containing protein), was carried out. Based on the results of fluorescence titration, the formation of a non-covalent inclusion complex between the above-mentioned Eu(III) complex and BSA was suggested. [ABSTRACT FROM AUTHOR]

Interaction of 3-(α- or γ-R-pyridin-2-yl)-1,2,4-triazines (R = Me, CO2Me) with arynes affords either the domino-transformation products, pyrido[1,2-a]indoles, or Diels-Alder reaction ones, isoquinolines. The influence of the nature and/or position of the substituent on the reaction pathway is discussed. [ABSTRACT FROM AUTHOR]

An operationally facile and high yielding one‐pot protocol has been developed for the preparation of pyridines appended with pyrazole via NH linker. This protocol includes SNipso/aza‐Diels‐Alder reactions in up to 54 % yields starting from 1,2,4‐triazine precursors. All the synthesized compounds have been evaluated for their in silico activity against JAK1, SYK, and FAK1 kinases. The most promising compound was tested in vitro using A‐172, Hs578T, and HepG2 cancer cell lines and exhibited considerable cytotoxicity with IC50 values <50 μM in A‐172 and HepG2 cell lines. Anticancer in vitro activity correlates well with the predicted in silico data. [ABSTRACT FROM AUTHOR]

Interactions of 5,6-diaryl-3-(quinolin-2-yl)-1,2,4-triazines with arynes are studied. 2-(3,4-Diarylisoqunolin-1-yl)quinolines are obtained in up to 65% yield via the inverse-demand Diels-Alder reaction between 5,6-diaryl-3-(quinolone-2-yl)-1,2,4-triazines and benzyne, generated in situ. [ABSTRACT FROM AUTHOR]

Azapyrenes are the nitrogen isosteres of pyrene. Based on theoretical and experimental studies, electron–acceptor azapyrene domains may be considered as convenient scaffolds for constructing a large variety of "push–pull" π-conjugated chromophores with pronounced ICT properties. Over the past decade, due to the unrelenting interest in functional materials and modern methodologies such as cross-coupling, peri-annulation, direct C–H-functionalization, etc., methods for the synthesis of aryl(alkyl) K-functionalized azapyrenes and other derivatives have been developed, and their photophysical and electrochemical properties have been studied. This short review aims at critical analysis of the best known/modern methods for the preparation of functionalized azapyrene derivatives, as well as an assessment of their photophysical/electrochemical properties in comparison with the structural and electronic properties of the parent pyrene. [ABSTRACT FROM AUTHOR]

[Display omitted] One-pot synthesis of cyclopentane-fused 5 ' -aryl-4- cycloalkylamino-2,2 ' -bipyridines based on the neat (200 °C) reaction of 3-(4-bromopyridin-2-yl)-1,2,4-triazines with enamines is reported. In the course of the transformation, consecutive aza -Diels–Alder reaction and nucleophilic substitution of bromine atom under the action of the liberating amine occur. The possibility of the solvent- and catalyst-free replacement of 4-positioned bromine atom in 2,2 '- bipyridines by amino moieties was demonstrated. [ABSTRACT FROM AUTHOR]

The present study describes a facile and solvent free synthesis of 1,2,4-triazine antipyrine derivatives (2a–f) in prominent yields (70–85%) over nucleophilic substitution of 5-carbonitrile triazines. Further, we strained to convert them into pyridine analogues (3a–f) over aza-Diels-Alder reaction with norbornadiene as dienophile but it was an unsuccessful attempt. It is an assumption we made that the antipyrine substituent primes the triazine electronically unfavorable at 1,2-aza position. All the synthesized compounds were confirmed by using 1H NMR, 19F NMR, 13C NMR and Mass spectral studies. Furthermore, this stated synthetic approach is ecofriendly as there are no toxic intermediates and also, the antipyrine derivatives can be aiding as promising templates for the development of new pharmaceutical scaffolds. [ABSTRACT FROM AUTHOR]

5‐(4‐(Het)arylphenyl)‐2,2′‐bipyridine‐6‐carboxylic acids were synthesized as ligands for the neutral lanthanide complexes by using the "1,2,4‐triazine" approach and Suzuki or Stille cross‐coupling reaction with intermediate 5‐(4‐bromophenyl)‐2,2′‐bipyridine‐6‐carbonitrile. The neutral europium complexes of these ligands were obtained with 3 : 1 stoichiometric amount. The photophysical properties of the synthesized complexes were studied, and the influence of the nature of the aryl substituent was estimated. In some cases the improvement of the photophysical characteristics has been demonstrated for the complexes in case of addition of extra phenyl ring in the structure of the ligand. [ABSTRACT FROM AUTHOR]

A convenient synthetic method has been developed for the synthesis of 3‐aryl‐6‐(quinolin‐2‐yl)picolinic acids having a cyclopentene fragment condensed to the pyridine ring. In addition, based on these new ligands neutral lanthanide complexes were obtained, and their photophysical properties were studied. It was observed that newly obtained quinoline‐based chelates exhibited a significant bathochromic shift of their absorption maxima compared to the previously described chelates based on 5‐aryl‐2,2′‐bipyridines. [ABSTRACT FROM AUTHOR]

[Display omitted] High temperature coupling of 6-aryl-5-cyano-3-(pyridin-2-yl)-1,2,4-triazines with 2-amino-4-aryloxazoles proceeds as the inverse demand Diels–Alder reaction between the oxazole moiety as dienophile and the 1,2,4-triazine moiety as diene to construct new 4,5-diaryl-6-cyano-3-hydroxypyridin-2-yl fragment. A reaction mechanism is proposed, and the structure of the key-product is proved by the X-ray diffraction analysis. [ABSTRACT FROM AUTHOR]

New series of highly luminescent DTTA (DTTA=diethylenetriaminetetraacetic acid) ‐ appended water‐soluble lanthanide complexes of 4‐(het)aryl‐2,2′‐bipyridines were prepared. By using the Kröhnke method and the alkylation reaction sequence, the corresponding 4‐(het)aryl‐2,2′‐bipyridines were synthesized in good yields, and their Eu(III), Tb(III), Dy(III) and Sm(III) complexes were prepared. Photophysical properties were studied for all the obtained complexes and the influence of the nature of the (het)aromatic substituent of 2,2′‐bipyridine moiety on the photoluminescence of the resulted lanthanide complexes was investigated. An efficient sensitization of lanthanide luminescence by halogen‐ and methoxyphenyl‐substituted 2,2′‐bipyridine ligands were observed to result in up to 56% and up to 25% quantum yields for Tb(III) and Eu(III) luminescence accordingly. [ABSTRACT FROM AUTHOR]