- Reversible C-N Bond Formation in the Zirconium-Catalyzed Intermolecular Hydroamination of 2-Vinylpyridine
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The intermolecular hydroamination of alkenes with alkylamines has been a long-standing challenge in catalysis, partially due to the near-thermoneutral nature of this transformation. Consistent with this understanding, we report the direct observation of reversible C-N bond formation in hydroamination. A bis(ureate) zirconium complex catalyzed the intermolecular hydroamination of 2-vinylpyridine. Reversible C-N bond formation was characterized by variable-temperature NMR spectroscopy, and thermodynamic parameters were determined using van't Hoff plots. Isolated intermediates support an aza-Michael-addition mechanism. Sensitivity to steric bulk in the C-N bond forming step provided further evidence for the kinetically accessible but limited thermodynamic driving force for this transformation.
- Griffin, Samuel E.,Pacheco, Javier,Schafer, Laurel L.
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supporting information
p. 1011 - 1016
(2019/03/08)
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- The catalytic effect of anion-exchanged supported ionic liquid on aza-Michael-type addition
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Abstract: An effective synthesis of anion-exchanged supported ionic liquids using diatomaceous earth as solid support and its catalytic effect on the aza-Michael-type addition is described. Anionic polytungstophosphate and bisulfate ion are used in the anion-exchange step in catalyst design. In addition, the aza-Michael-type addition of various amines to 2- and 4-vinyl pyridine was examined in this article. The catalytic system can be separated from the reaction mixture and recycled in subsequent reactions. The structure of anion-exchanged supported ionic liquid on diatomaceous earth was studied by XRD, FT-IR, SEM, TGA and BET techniques. The structure of organic products was determined by 1HNMR, 13CNMR, FTIR, CHN and MASS spectroscopy. Graphical Abstract: [Figure not available: see fulltext.].
- Ghasemi, Mohammad Hadi,Kowsari, Elaheh
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p. 3691 - 3709
(2017/06/20)
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- Aza-Michael-type addition reaction catalysed by a supported ionic liquid phase incorporating an anionic heteropoly acid
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In this work, we have obtained substituted amines under mild conditions in good yields using the Aza-Michael-type addition of various amines to vinyl compounds catalysed by a supported ionic liquid incorporating an anionic heteropoly acid. Different catalysts, including Lewis acids, Br?nsted acids and heteropoly acids were investigated in which heteropoly acids having dual Br?nsted and Lewis acid characteristics were excellent catalysts. The ionic liquid incorporating a polytungstate anion supported on magnetic diatomaceous earth as a magnetically separable heterogeneous catalyst offered the best results in terms of yield. The solid nanocatalyst was easily removed with a magnet.
- Ghasemi, Mohammad Hadi,Kowsari, Elaheh,Shafiee, Abbas
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supporting information
p. 1150 - 1153
(2016/03/09)
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- Rhodium-catalyzed anti-Markovnikov hydroamination of vinylarenes
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The transition metal-catalyzed anti-Markovnikov hydroamination of unactivated vinylarenes with a rhodium complex of DPEphos is reported. The reaction of electron-neutral or electron-rich vinylarenes with a variety of secondary amines in the presence of catalyst forms the products from anti-Markovnikov hydroamination in high yields. Reactions of morpholine, N-phenylpiperazine, N-Boc-piperazine, piperidine, 2,5-dimethylmorpholine, and perhydroisoquinoline reacted with styrene to form the amine product in 51-71% yield. Reactions of a variety of vinylarenes with morpholine generated amine as the major product. Reactions of morpholine with electron-poor vinylarenes gave lower amine:enamine ratios than reactions of electron-rich vinylarenes at the same concentration of vinylarene, but conditions were developed with lower concentrations of electron-poor vinylarene to maintain formation of the amine as the major product. Reactions of dimethylamine with vinylarenes were fast and formed amine as the major product. Mechanistic studies on the hydroamination process showed that the amine:enamine ratio was lower for reactions conducted with higher concentrations of vinylarene and that one vinylarene influences the selectivity for reaction of another. A mechanism proceeding through a metallacyclic intermediate that opens in the presence of a second vinylarene accounts for these and other mechanistic observations. Copyright
- Utsunomiya, Masaru,Kuwano, Ryoichi,Kawatsura, Motoi,Hartwig, John F.
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p. 5608 - 5609
(2007/10/03)
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- Photocatalyzed [2 + 2 + 2]-cycloaddition of nitriles with acetylene: An effective method for the synthesis of 2-pyridines under mild conditions
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The photocatalyzed [2 + 2 + 2]-cycloaddition of nitriles with 2 equiv of acetylene to 2-pyridines can be carried out under mild conditions and represents a valuable extension to common synthetical methods. For the ideal wavelength range (350-500 nm), lamps as well as sunlight can be used. Working at room temperature and in organic solvents such as toluene or hexane as well as in water gives satisfying results in many cases. However, it is also possible to vary the solvent and the reaction temperature of the photocatalyzed synthesis and to choose, with respect to the specific substrate, specific requirements for this particular reaction and general requirements of the method. This simple and selective method derives its potential mainly from the large variety of applicable nitriles. Suitable substrates include (functionalized) aliphatic and aromatic nitriles as well as cyanamides derived from secondary amines.
- Heller, Barbara,Sundermann, Bernd,Buschmann, Helmut,Drexler, Hans-Joachim,You, Jingsong,Holzgrabe, Ulrike,Heller, Eberhard,Oehme, Guenther
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p. 4414 - 4422
(2007/10/03)
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- Fine-tuning of copper(I)-dioxygen reactivity by 2-(2-pyridyl)ethylamine bidentate ligands
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Copper(I)-dioxygen reactivity has been examined using a series of 2-(2-pyridyl)ethylamine bidentate ligands R1Py1R2,R3. The bidentate ligand with the methyl substituent on the pyridine nucleus MePy1Et,Bz (N-benzyl-N-ethyl-2-(6-methylpyridin-2-yl)ethylamine) predominantly provided a (μ-η2:η2-peroxo)dicopper(II) complex, while the bidentate ligand without the 6-methyl group HPy1Et,Bz (N-benzyl-N-ethyl-2-(2-pyridyl)ethylamine) afforded a bis(μ-oxo)dicopper(III) complex under the same experimental conditions. Both Cu2O2 complexes gradually decompose, leading to oxidative N-dealkylation reaction of the benzyl group. Detailed kinetic analysis has revealed that the bis (μ-oxo)dicopper(III) complex is the common reactive intermediate in both cases and that O-O bond homolysis of the peroxo complex is the rate-determining step in the former case with MePy1Et,Bz. On the other hand, the copper(I) complex supported by the bidentate ligand with the smallest N-alkyl group (HPy1Me,Me, N,N-dimethyl-2-(2-pyridyl)ethylamine) reacts with molecular oxygen in a 3:1 ratio in acetone at a low temperature to give a mixed-valence trinuclear copper(II, II, III) complex with two μ3-oxo bridges, the UV-vis spectrum of which is very close to that of an active oxygen intermediate of lacase. Detailed spectroscopic analysis on the oxygenation reaction at different concentrations has indicated that a bis(μ-oxo)dicopper(III) complex is the precursor for the formation of trinuclear copper complex. In the reaction with 2,4-di-tert-butylphenol (DBP), the trinuclear copper(II, II, III) complex acts as a two-electron oxidant to produce an equimolar amount of the C-C coupling dimer of DBP (3,5,3′,5′tetra-tert-butyl-biphenyl-2,2′-diol) and a bis(μ-hydroxo)dicopper(II) complex. Kinetic analysis has shown that the reaction consists of two distinct steps, where the first step involves a binding of DBP to the trinuclear complex to give a certain intermediate that further reacts with the second molecule of DBP to give another intermediate, from which the final products are released. Steric and/or electronic effects of the 6-methyl group and the N-alkyl substituents of the bidentate ligands on the copper(I)-dioxygen reactivity have been discussed.
- Taki, Masayasu,Teramae, Shinichi,Nagatomo, Shigenori,Tachi, Yoshimitsu,Kitagawa, Teizo,Itoh, Shinobu,Fukuzumi, Shunichi
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p. 6367 - 6377
(2007/10/03)
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- Aminomethylation of picolines
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Under various conditions aminomethylation of 2-methylpyridine proceeds in amounts to be isolated only with paraformaldehyde/secondary amine-hydrochloride or better using iminium salts. 4-Methylpyridine is - in contrary to literature - also aminomethylated at the methyl group giving mono- and disubstituted products. 3-Methylpyridine does not react even under drastic conditions. The benzylpyridines show a higher reactivity but a similar behaviour. 4-Benzylpyridine yields the monoalkylated product as hydrochloride or a mixture of the dihydrochloride and the quaternary derivative. The reaction mechanism explained with enamine intermediates is substantiated by MNDO calculations.
- Moehrle,Pycior,Lessel
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p. 569 - 575
(2007/10/03)
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- Chemical Behaviour of Trimethylammonium N-Methylides Substituted with Nitrogen-containing Heteroaromatic Rings. Rearrangement of N,N-Dimethyl(pyridylmethyl)ammonium, N,N-Dimethyl-(1-methylpyrrolylmethyl)ammonium and N,N-Dimethyl-(1-methylindolylmethyl)ammonium N-Methylides
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N,N-Dimethyl(pyridylmethyl)ammonium N-methylides 2, 6 11, N,N-dimethyl(1-methylpyrrolylmethyl)ammonium N-methylides 15, 20, and N,N-dimethyl(1-methylindolylmethyl)ammonium N-methylides 23, 28 were generated by fluoride ion-induced desilylation of the corresponding (trimethylsilyl)methylammonium salts 1, 5, 10, 14, 19, 22 and 27, and the isomerisation products of the ylides were investigated.
- Maeda, Yasuhiro,Shirai, Naohiro,Sato, Yoshiro
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p. 393 - 398
(2007/10/02)
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- Reductive Amination of Ethynylpyridines with Sodium Cyanoborohydride
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In order to investigate the structure-activity relationship of betahistine derivatives, a general synthesis of methylated 2-(2-methylaminoethyl)pyridines was developed based on the addition of methylamine hydrochloride to methylated 2-ethynylpyridines under reductive conditions.In addition, the scope and limitations of the reductive addition were briefly examined.For example, the reaction proceeded smoothly with p-nitrophenylacetylene, whereas phenylacetylene itself did not react with methylamine.Keywords - ethynylpyridine; sodium cyanoborohydride; reductive amination; betahistine; palladium-catalyzed reaction; ethyl pyridineacetate; 2-(2-pyridyl)ethylamine
- Sakamoto, Takao,Nagata, Hideo,Kondo, Yoshinori,Sato, Kaori,Yamanaka, Hiroshi
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p. 4866 - 4872
(2007/10/02)
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- Process for the catalytic production of 2-substituted pyridines
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A process for the catalytic production of a 2-substituted pyridine which comprises reacting a corresponding cyano compound and acetylene in the presence of cobaltocene. Favorable conversion speed, conversion of at least 90 percent, good yield and high selectivity are obtained.
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