- Regioselective Direct C-H Trifluoromethylation of Pyridine
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A highly efficient and regioselective direct C-H trifluoromethylation of pyridine based on an N-methylpyridine quaternary ammonium activation strategy has been developed. A variety of trifluoromethylpyridines can be obtained in good yield and excellent re
- Yang, Xiao,Sun, Rui,Li, Shun,Zheng, Xueli,Yuan, Maolin,Xu, Bin,Jiang, Weidong,Chen, Hua,Fu, Haiyan,Li, Ruixiang
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supporting information
p. 7108 - 7112
(2020/10/02)
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- Cyclometalated Ir(III) complexes of deprotonated N-methylbipyridinium ligands: Effects of quaternised N centre position on luminescence
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Six new tricationic IrIII complexes of cyclometalating ligands derived from 1-methyl-2-(2′-pyridyl)pyridinium or 1-methyl-4-(2′-pyridyl)pyridinium are described. These complexes of the form [IrIII(C∧N)2(N∧N)]3+ (C∧N = cyclometalating ligand; N∧N = α-diimine) have been isolated and characterised as their PF6- and Cl- salts. Four of the PF6- salts have been studied by X-ray crystallography, and structures have been obtained also for two complex salts containing MeCN and Cl- or two Cl- ligands instead of N∧N. The influence of the position of the quaternised N atom in C∧N and the substituents on N∧N on the electronic/optical properties are compared with those of the analogous complexes where C∧N derives from 1-methyl-3-(2′-pyridyl)pyridinium (B. J. Coe, et al., Dalton Trans., 2015, 44, 15420). Voltammetric studies reveal one irreversible oxidation and multiple reduction processes which are mostly reversible. The new complexes show intramolecular charge-transfer absorptions between 350 and 450 nm, and exhibit bright green luminescence, with λmax values in the range 508-530 nm in both aqueous and acetonitrile solutions. In order to gain insights into the factors that govern the emission properties, density functional theory (DFT) and time-dependent DFT calculations have been carried out. The results confirm that the emission arises largely from triplet excited states of the C∧N ligand (3LC), with some triplet metal-to-ligand charge-transfer (3MLCT) contributions.
- Coe, Benjamin J.,Helliwell, Madeleine,Raftery, James,Sánchez, Sergio,Peers, Martyn K.,Scrutton, Nigel S.
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p. 20392 - 20405
(2015/12/04)
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- Synthesis of new pyrrole-pyridine-based ligands using an in situ Suzuki coupling method
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The compounds 6-(pyrrol-2-yl)-2,2'-bipyridine, 2-(pyrrol-2-yl)-1,10- phenanthroline and 2-(2-(N-methylbenz[d,e]imidazole)-6- (pyrrol-2-yl)-pyridine were synthesized by using an in situ generated boronic acid for the Suzuki coupling. Crystals of the products could be grown and exhibited interesting structures by X-ray analysis, one of them showing a chain-like network with the adjacent molecules linked to each other via intermolecular N-H...N hydrogen bonds.
- Boettger, Matthias,Wiegmann, Bjoern,Schaumburg, Steffen,Jones, Peter G.,Kowalsky, Wolfgang,Johannes, Hans-Hermann
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supporting information; experimental part
p. 1037 - 1047
(2012/08/28)
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- HPLC analysis of aliphatic sulfonate surfactants using ion-pair detection
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A method was developed for the analysis of a number of surfactants which contained no UV-chromophores, using RP-HPLC with Indirect Photometric Detection, IPD. Pyridinium salts such as N-methylpyridinium iodide, N-methyl-2,2′- dipyridinium iodide and N,N′-dimethyl-2,2′-dipyridinium diiodide, were used as the visualization reagents, forming ion-pair complexes with the sulfonate surfactants. This allowed ordinary UV-detection. N-methylpyridinium iodide proved to be a suitable reagent, both with respect to ease of preparation and response. The eluents consisted of mixtures of acetonitrile and water, being 0.1 - 0.25 mM with respect to pyridinium salt. The method was sensitive and exhibited good signal to noise ratios, as well as linear responses over a wide concentration range. All of the analyzed surfactants were separated, including the diastereomeric forms of some of the surfactants.
- Zahrobsky, Marek,Camporese, Davide,Rist, ystein,Carlsen, Per H. J.
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p. 1179 - 1189
(2007/10/03)
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- Synthesis and electrochemical properties of bis(bipyridine)ruthenium(II) complexes bearing pyridinyl- and pyridinylidene ligands induced by cyclometalation of N′-methylated bipyridinium analogs
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Ruthenium complexes with bipyridine-analogous quaternized (N,C) bidentate ligands [RuL(bpy)2](PF6)2 (bpy = 2,2′-bipyridine, (1), L = L1 = N′-methyl-2,4′- bipyridinium; (2), L = L2 = N′-methyl-2,3′-bipyridinium) were synthesized and characterized. The structure of complex 2 was determined by the X-ray structure analysis. The 13C{1H} NMR spectroscopic and cyclic voltammetric studies indicate that the coordination modes of these ligands are quite different, that is, the C-coordinated rings of (N,C)-ligands in 1 and 2 are linked to ruthenium(II) with a pyridinium manner and a pyridinylidene one, respectively. The ligand-localized redox potentials of 1 and 2 also revealed the substantial difference in the electron donating ability of both ligands.
- Koizumi, Take-Aki,Tomon, Takashi,Tanaka, Koji
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p. 1258 - 1264
(2007/10/03)
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- Regioselective functionalization of 2,2′-bipyridine and transformations into unsymmetric ligands for coordination chemistry
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Novel synthetic strategies for a series of unsymmetrically substituted 2,2′-bipyridines have been developed. These bipyridines have found use in some novel homoleptic and heteroleptic ruthenium(II) complexes. Two methods for regiochemical control of nucleophilic addition to bpy have been explored: (i) mono N-oxidation followed by cyanation and subsequent hydrolysis gave 6-carboxy-2,2′-bipyridine (4); (ii) mono N-methylation followed by the conversion into 6-bromo-2,2′-bipyridine (12) and subsequent nucleophilic addition of lithioacetonitrile followed by hydrolysis of 6-cyanomethyl-2,2′-bipyridine (8) gave the homologous 2,2′-bipyridine-6-acetic acid (9). An established method of regioselective mono-ring alkylation of bpy using methyllithium yielded 6-methyl-2,2′-bipyridine (14), and the generation of the anion of 14 and subsequent addition to a chloromethyl oxazoline was applied to synthesize a second homologue, methyl 2,2′-bipyridine-6-propanoate (16). Structural determinations using 1H, 13C and 2D NMR spectroscopy permitted complete assignments of all signals in the 1H NMR spectra. Acta Chemica Scandinavica 1998.
- Norrby, Thomas,Boerje, Anna,Zhang, Lian,Akermark, Bjoern
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- From bipyridines to tobacco alkaloids and related compounds
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Starting from structural considerations which led to the hypothesis that a chemical relationship could exist between two families of natural compounds (mainly pyridinic and pyrrolidinic alkaloids), experiments were carried out in order to establish a correlation route between the two studied classes. Of special interest was the central position of nicotine in these studies, and the main part of this work was devoted to the synthesis of nicotine starting from bipyridines. It was thus necessary to determine the conditions for selective reactions on one aromatic ring of bipyridines (N-methylation, N-oxidation and reduction of the heterocycle). Ring contraction procedure allowed us to obtain nicotine from the parent compound (3,3′-bipyridine). Complementary studies yielded various isomers of piperidinylpyridines (hexahydro derivatives of bipyridines) in a regiochemically controlled manner by means of original methods. Elsevier,.
- Plaquevent, Jean-Christophe,Chichaoui, Ilhame
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p. 369 - 379
(2007/10/03)
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- N-ALKYL-4,4'-BIPYRIDYL. A NEW EFFICIENT ELECTRON CARRIER IN THE PHOTOCHEMICAL HYDROGEN PRODUCING SYSTEM
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Various pyridine derivatives were found to be effective electron carriers in the photochemical hydrogen generating system consisting of ascorbic acid as a reproducible electron donor, zinc meso-tetra (4-hydroxysulphophenyl) porphyrin as a photocatalyst, a
- Tabushi, Iwao,Yazaki, Akira
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p. 4185 - 4188
(2007/10/02)
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