- Versatile and Highly Efficient trans-[Pd(NHC)Cl2(DMS/THT)] Precatalysts for C?N and C?C Coupling Reactions in Green Solvents
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A straightforward synthetic procedure to well-defined, air- and moisture- stable trans-[Pd(NHC)Cl2(DMS/THT)] (NHC=IPr, SIPr, IMes, IPrCl, IPr*, IPr#) pre-catalysts is reported. These complexes were obtained by reacting NHC ? HCl imidazolium salts with trans-[PdCl2(DMS/THT)2] precursors with the assistance of the weak base K2CO3 in green acetone at 40 °C. The scalability of this protocol was demonstrated. The catalytic activity of the synthesized complexes was studied in the Buchwald-Hartwig and Suzuki-Miyaura reactions. Remarkably, most of the synthesized complexes exhibit higher catalytic activity with respect to their PEPPSI congeners in the Buchwald-Hartwig amination in 2-MeTHF. In particular, complex trans-[Pd(IPr#)Cl2(DMS)] enabled the coupling of various (hetero)aryl chlorides and primary/secondary amines with a 0.2 mol% catalyst loading. In addition, trans-[Pd(IPr)Cl2(DMS)] showed excellent performance in the room-temperature Suzuki-Miyaura reaction involving various (hetero)aryl chlorides and aryl boronic acids. In summary, the synthesized complexes, especially trans-[Pd(NHC)Cl2(DMS)], can be considered as greener alternatives to classical PEPPSI type catalysts based on the lower toxicity of the throw-away DMS ligand compared to 3-chloropyridine.
- Cazin, Catherine S. J.,Liu, Yaxu,Nolan, Steven P.,Peng, Min,Scattolin, Thomas,Van Hecke, Kristof,Voloshkin, Vladislav A.
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- One-Pot Synthesis of Secondary Amines from Nitroarenes and Aldehydes on Supported Copper Catalysts in a Flow Reactor: The Effect of the Support
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The effect of the support on the properties of copper catalysts supported on γ-Al2O3, SiO2, and TiO2–SiO2 with a ~5 wt % Cu content was studied in the one-pot synthesis of N-heptyl-p-toluidine from p-nitrotoluene and n-heptanal. The catalysts were characterized by elemental analysis, X-ray diffraction analysis, transmission electron microscopy, temperature-programmed reduction, and low-temperature nitrogen adsorption. The reaction was carried out in a flow reactor with the use of molecular hydrogen as a reducing agent. It was established that the nature of the support exerts a profound effect on the yield of the target secondary amine; in this case, 5%Cu/Al2O3 was found the most active catalyst. A combination of high catalyst activity in the hydrogenation of a nitro group to an amino group with the presence of acid sites, which facilitate imine formation as a result of the interaction of n-heptanal with p-toluidine, on the catalyst surface is necessary for reaching the greatest yield of N-heptyl-p-toluidine. The study of reaction mechanism on the 5%Cu/Al2O3 catalyst showed that p-nitrotoluene inhibits the hydrogenation of n-heptanal, and aldehyde hydrogenation into alcohol begins only after the conversion of the major portion of p-nitrotoluene as a result of the selective adsorption of the nitroarene under the conditions of the simultaneous presence of p-nitrotoluene and n-heptanal in the reaction mixture.
- Artyukha,Nuzhdin,Bukhtiyarova,Derevyannikova,Gerasimov, E. Yu.,Gladkii, A. Yu.,Bukhtiyarov
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p. 593 - 600
(2018/10/02)
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- Synthesis of secondary amines by reductive amination of aldehydes with nitroarenes over supported copper catalysts in a flow reactor
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Supported copper catalysts were investigated for the one-pot reductive amination of aldehydes with nitroarenes in a continuous flow reactor. This process is considered advantageous compared to current traditional methods, which present several drawbacks, such as toxicity of reducing or alkylation agent, lack of monoalkylation selectivity and large amounts of waste produced. Various secondary amines were synthesized in good to excellent yields in the reactions of aliphatic aldehydes with nitroarenes using molecular hydrogen as a reducing agent. It was found that the yield of secondary amine depends on the rate of formation of intermediate imine.
- Nuzhdin, Alexey L.,Artiukha, Ekaterina A.,Bukhtiyarova, Galina A.,Derevyannikova, Elizaveta A.,Bukhtiyarov, Valerii I.
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p. 108 - 113
(2017/09/15)
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- Flow synthesis of secondary amines over Ag/Al2O3 catalyst by one-pot reductive amination of aldehydes with nitroarenes
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An alumina-supported silver catalyst was investigated in the one-pot reductive amination of aldehydes with nitroarenes in a continuous flow reactor using molecular hydrogen as a reducing agent. A series of secondary amines containing alkyl, OH, OCH3, Cl, Br and CC groups was synthesized in good to excellent yields. The yield of the secondary amine depends on the rate of formation of an intermediate imine. It was shown that the accumulation of carbonaceous deposits on the catalyst is the main reason of catalyst deactivation. The spent catalyst can be easily regenerated and reused without losing catalytic activity.
- Artiukha, Ekaterina A.,Nuzhdin, Alexey L.,Bukhtiyarova, Galina A.,Bukhtiyarov, Valerii I.
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p. 45856 - 45861
(2017/10/06)
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- One-pot reductive amination of aldehydes with nitroarenes over an Au/Al2O3 catalyst in a continuous flow reactor
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One-pot reductive amination of aromatic and aliphatic aldehydes with nitroarenes over an Au/Al2O3 catalyst in a continuous flow reactor using molecular hydrogen as a reducing agent was performed. Various secondary aromatic amines were obtained in good to excellent yields.
- Artiukha,Nuzhdin,Bukhtiyarova,Zaytsev, S. Yu.,Plyusnin,Shubin, Yu. V.,Bukhtiyarov
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p. 4741 - 4745
(2015/10/05)
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- Reinvestigating Raney nickel mediated selective alkylation of amines with alcohols via hydrogen autotransfer methodology
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An efficient, cost-effective use of Raney nickel (R-Ni) a widely used industrial catalyst for N-alkylation using alcohols is highlighted here. The work describes the scope and capability of R-Ni in hydrogen autotransfer reactions enabling its widespread use in the Chemical and Pharmaceutical industry. R-Ni of W4, T4, and W7 grades were prepared and evaluated for alkylation of amines. The best activity and selectivity for mono alkylation of amines were obtained using W4 R-Ni at 1:4 moles of amine to alcohol in xylene at reflux. T4 R-Ni also showed ability to form stable imines. The prepared R-Ni was also recycled and reused for N-alkylation reaction. The optimized methodology was applied for synthesis of Active Pharmaceutical ingredients Piribedil and Mepyramine. The simplicity and wide substrate scope makes this method a preferred Hydrogen Auto-transfer protocol for the alkylation of amines.
- Mehta, Astha,Thaker,Londhe,Nandan, Santosh R.
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p. 241 - 251
(2014/05/20)
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- Copper-catalyzed amination of aromatic halides with 2-N,N-dimethylaminoethanol as solvent
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A copper-catalyzed amination of aromatic halides under mild conditions using N,N-dimethylaminoethanol as solvent is described. We have studied this reaction in some detail varying the copper source, base, water content and other parameters including the scope of useful amine and aromatic halide structures. A variety of 4-halo-N,N-cycloalkylanilines and 2-N,N-cycloalkylaminothiophenes were synthesized for further elaboration into chromophores for optoelectronic applications.
- Lu, Zhikuan,Twieg, Robert J.,Huang, Songping D.
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p. 6289 - 6292
(2007/10/03)
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