- Straight Access to Indoles from Anilines and Ethylene Glycol by Heterogeneous Acceptorless Dehydrogenative Condensation
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The development of original strategies for the preparation of indole derivatives is a major goal in drug design. Herein, we report the first straight access to indoles from anilines and ethylene glycol by heterogeneous catalysis, based on an acceptorless dehydrogenative condensation, under noninert conditions. In order to achieve high selectivity, a combination of Pt/Al2O3 and ZnO have been found to slowly dehydrogenate ethylene glycol generating, after condensation with the amine and tautomeric equilibrium, the corresponding pyrrole-ring unsubstituted indoles.
- Llabres-Campaner, Pedro Juan,Ballesteros-Garrido, Rafael,Ballesteros, Rafael,Abarca, Belén
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supporting information
p. 521 - 526
(2018/01/01)
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- β-Amino alcohols from anilines and ethylene glycol through heterogeneous Borrowing Hydrogen reaction
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Borrowing Hydrogen (BH), also called Hydrogen Autotransfer (HA), reaction with neat ethylene glycol represents a key step in the preparation of β-amino alcohols. However, due to the stability of ethylene glycol, mono-activation has rarely been achieved. Herein, a combination of Pd/C and ZnO is reported as heterogeneous catalyst for this BH/HA reaction. This system results in an extremely air and moisture stable, and economic catalyst able to mono-functionalize ethylene glycol in water, without further activation of the diol. In this work, different diols and aromatic amines have been explored affording a new approach towards amino alcohols. This study reveals how the combination of two solid species can afford interesting catalytic properties in heterogeneous phase. ZnO activates ethylene glycol while Pd/C is the responsible of the BH/HA cycle. This catalytic system has also been found useful to dehydrogenate indoles affording indolines that undergo in situ BH/HA cycle prior to re-aromatization, representing a tandem heterogeneous process.
- Llabres-Campaner, Pedro J.,Ballesteros-Garrido, Rafael,Ballesteros, Rafael,Abarca, Belén
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supporting information
p. 5552 - 5561
(2017/08/22)
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- Copper-catalyzed C-N bond cross-coupling of aryl halides and amines in water in the presence of ligand derived from oxalyl dihydrazide: Scope and limitation
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An efficient and convenient method has been developed for the copper-catalyzed C-N bond cross-coupling of aryl bromides with electron-donor substituents and aliphatic amines in water. The new ligand system N-phenyloxalyl bishydrazide/hexane-2,5-dione has been shown to be considerably more efficient in the copper-catalyzed C-N bond cross-coupling reaction as compared to the ligands described in the literature and allowed decreasing of the catalyst amount (up to 2 mol %) to achieve acceptable yields of isolated products (46-84%). Acceptor substituted aryl bromides, aryl bromides with substituents in the ortho-position, and some aryl dichlorides can undergo the C-N cross-coupling under the developed conditions, but their reactivity is lower.
- Kurandina,Eliseenkov,Khaibulova,Petrov,Boyarskiy
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p. 7931 - 7937
(2015/09/15)
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- Microwave-promoted mono-N-alkylation of aromatic amines in water: A new efficient and green method for an old and problematic reaction
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A greener improvement to direct mono-N-alkylation of aromatic amines by alkyl halides was achieved using microwave irradiation in water without any catalyst.
- Marzaro, Giovanni,Guiotto, Adriano,Chilin, Adriana
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supporting information; experimental part
p. 774 - 776
(2010/04/23)
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- Palladium-catalyzed aminations of aryl halides with phosphine- functionalized imidazolium ligands
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A series of 1-(2-diphenylphosphinoferrocenyl)ethyl-3-substituted imidazolium iodides [3-substituent = methyl (1a); isopropyl (1b); tert-butyl (1c); 1-adenosyl (1d); cyclohexyl (1e); 2,6-dimethylphenyl (1f); 2,4,6-trimethylphenyl (1g); 2,6-diisopropylphenyl (1h)] have been prepared and evaluated as ligands in the palladium-catalyzed aminations of aryl halides with various amines. The scope of the coupling process was carried out for various aryl bromides and chlorides with the catalysts generated in situ from a mixture of Pd(OAc)2 and 1 in the presence of a base. NaOtBu was found the choice of base in combination with dioxane, toluene, or DME as solvent, although NaOH or Cs2CO3 promoted the coupling of 4-bromotoluene with morpholine in moderate conversion. The steric hindrance from the 3-substituent of imidazolium in the hybrid-bidentate chelating system was found to be only beneficial to the substrates without ortho-substituents. The more sterically hindered 1d or 1h promoted the coupling of bromobenzene with morpholine in nearly quantitative conversion with 0.2 mol% of palladium loading in the presence of NaOtBu at 110°C, and 94% of conversion was afforded with the less sterical demanding 1a for a longer time. However, for the substrates with ortho-substituents, higher conversions were achieved with 1a. The Pd(OAc)2/1d catalytic system was also active for deactivated aryl chloride, and 71% isolated yield for the desired product was realized for coupling of 4-chloroanisole with morpholine at 2 mol% of catalyst loading. The developed catalyst system has been applied successfully to the synthesis of a key building block for a type of functional polymers. The Royal Society of Chemistry.
- Shi, Ji-Cheng,Yang, Pengyu,Tong, Qingsong,Jia, Li
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p. 938 - 945
(2008/09/18)
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- Applicability of a fiber-supported catalyst on a Buchwald-Hartwig amination reaction
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The applicability of four different heterogeneous palladium catalysts has been evaluated for the Buchwald-Hartwig animation reaction between p-bromotoluene and piperazine in the presence of the base NaO-t-Bu. The catalyst that provided the highest selectivity toward the desired animation reaction was found to be a polymer-supported palladium dichloride/triphenylphosphine catalyst. Experimental investigations of the catalyst in a reactor setup showed that the undesired reduction reaction of the aryl halide was dominant when the catalyst was reused and washed in solvent prior to reaction and when additional reactants were added to an already reacted reaction mixture. A significant washout of triphenylphosphine and palladium from the catalyst was also identified during the course of reaction and separation.
- Christensen, Henrik,Kiil, Soren,Dam-Johansen, Kim,Nielsen, Ole
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p. 956 - 965
(2012/12/30)
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- Effect of solvents on the product distribution and reaction rate of a Buchwald-Hartwig amination reaction
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The Buchwald-Hartwig amination reaction between p-bromotoluene and piperazine in the presence of the homogeneous catalytic system Pd(dba) 2/(±)-BINAP and the base NaO-t-Bu was investigated in two different classes of solvents: aprotic, nonpolar and aprotic, polar. The reaction was carried out using microwaves as the heating source, and it was found that the product distribution was strongly dependent on the class of the solvent. Based on the experimental results the selectivity towards the desired monosubstituted aryl piperazine was calculated, and it was found that the most appropriate solvent for the Buchwald-Hartwig amination reaction under the conditions applied was m-xylene.
- Christensen, Henrik,Kiil, Soren,Dam-Johansen, Kim,Nielsen, Ole,Sommer, Michael B.
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p. 762 - 769
(2012/12/22)
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- Nickel-catalysed selective N-arylation or N,N′-diarylation of secondary diamines
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The selective synthesis of N-aryl or N,N′-diaryl piperazines and trimethylene(bis)piperidines from the corresponding diamines and aryl chlorides using a catalyst combination of Ni(0) associated to 2,2′-bipyridine is described. The Ni/2,2′-bipyridine catalyst is also effective for the sequential arylation of piperazine. The preparation of novel and unsymmetrical 1,4-diaryl piperazines is reported.
- Brenner, Eric,Schneider, Rapha?l,Fort, Yves
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p. 6913 - 6924
(2007/10/03)
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- An air-stable palladium/N-heterocyclic carbene complex and its reactivity in aryl amination
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(matrix presented) The synthesis and characterization of [Pd(IPr)Cl2]2 (1), an air- and moisture-stable complex, is reported. The utilization of 1 as a catalyst for amination of aryl chlorides and bromides with a variety of amine coupling partners under mild conditions is described. The amination reactions with 1 show a remarkable insensitivity to oxygen and water, and thus the amination reactions could be performed in air on the benchtop with undried reagent grade solvents and substrates with small effects on reaction times and conversions.
- Viciu, Mihai S.,Kissling, Rebecca M.,Stevens, Edwin D.,Nolan, Steven P.
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p. 2229 - 2231
(2007/10/03)
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- Nickel-mediated amination chemistry. Part 2: Selective N-arylation or N,N'-diarylation of piperazine
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The 2,2'-bipyridine liganded Ni catalyst has revealed a good selectivity in the mono arylation of piperazine starting from aryl chlorides allowing a selective and efficient synthesis of N-arylpiperazines using stoichiometric amounts of reagents. The preparation of N,N'-diaryl substituted piperazines is also described. (C) 2000 Elsevier Science Ltd.
- Brenner, Eric,Schneider, Rapha?l,Fort, Yves
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p. 2881 - 2884
(2007/10/03)
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- USE OF HEXAMETHYLPHOSPHORAMIDE (HMPA) IN THE ALKYLATION OF AROMATIC AMINES: SYNTHESIS OF AZETIDINES, PYRROLIDINES, PIPERIDINES AND HEXAHYDROAZEPINES
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The direct alkylation of p-toluidine, as a model of aromatic amines, with 1,3-, 1,4-, 1,5- and 1,6-ditosylates, -dibromides or -dimesitylates in HMPA as solvent affords the corresponding cyclic amines.The convenience of this reaction and some observed lim
- Juaristi, Eusebio,Madrigal, Domingo
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p. 629 - 636
(2007/10/02)
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- Synthesis and structural characterization of N,N'-diarylpiperazine N,N'-dioxide tetrahydrates (aryl=o-tolyl, p-tolyl, p-chlorophenyl)
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The synthesis and X-ray structure determination of N,N'-di(o-tolyl)piperazine N,N'-dioxide tetrahydrate, I, N,N'-di(p-tolyl)piperazine N,N'-dioxide tetrahydrate, II, and N,N'-di(p-chlorophenyl)piperazine N,N'-doxide tetrahydrate, III, are described.Compound I crystallizes in space group P1 with a=7.778(1), b=7.915(2), c=8.919(2) A, α=106.25(2), β=99.56(1), γ=108.80(2) deg, and Z=1.Compound II crystallizes in space group P1 with a=6.558(1), b=7.134(2), c=11.610(3) A; α=73.23(2), β=78.08(2), γ=72.67(2) deg., and Z=1.Compound III crystallizes in space group P21/c with a=9.159(3), b=12.390(4), c=8.339(4) A, β=97.38(3) deg., and Z=2.The structures of I-III were solved by the direct method and refined to R=0.049 (1749 observed MoKα reflections), 0.055 (2651 observed reflections), and 0.035 (1827 observed reflections), respectively.In each case, the N,N'-dioxide molecule occupies a site of symmetry 1.The piperazine ring takes the chair form, with two N-O bonds oriented axially in a trans configuration.The structures are characterized by strong hydrogen bonding between the water molecules, as well as between the N-oxide groups and water molecules, giving rise to puckered layers composed of various combinations of edge-sharing four-membered, six-membered, ten-membered, and twelve-membered rings.The aryl rings, which protrude on both sides of each puckered layer, constitute hydrophobic regions separating the hydrophylic layers in the crystal packing.
- Kwok, Chun-Kiu,Mak, Thomas C. W.
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p. 1836 - 1847
(2007/10/02)
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