- E-selective semi-hydrogenation of alkynes with dinuclear iridium complexes under atmospheric pressure of hydrogen
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Semi-hydrogenation of alkynes was catalyzed by halide-bridged dinuclear iridium complexes, yielding (E)-alkenes with high selectivity. Mechanistic studies conducted with monohydride dinuclear species, dihydride mononuclear species, and trihydride dinuclear species led us to propose a mechanism involving dual cycles.
- Higashida, Kosuke,Mashima, Kazushi
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- N-donor 2-(Sulfonamido)benzamide ligands, their palladium(II) coordination species and C–C coupling catalysis efficiencies
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A series of synthetically accessible ligands based on new 2-(R-sulfonamido)benzamide have been prepared (R = methyl for H3M; R = 4-toly for H3T and T2CN; R = 2,4,6-triisopropylphenyl for H3iP and HiPCN). The R-substituents were selected to vary in sizes. Allowing ligand H3iP and palladium acetate to stand in solvent leads to self-assembly of the well-defined solvent- and stoichiometry-controlled tetranuclear or hexanuclear coordination macromolecules Pd4(iP)2 and (PdHiP)6, which were analysed by X-ray crystallography. It was observed that palladium active species for Suzuki coupling catalysis could be stabilized by these simple and synthetically assessable N-donor ligands as revealed by turnover frequencies reaching 5500 h?1. Electronic features of these N-donors appear to be more important than the steric properties.
- Oloyede, Hammed Olawale,G?rls, Helmar,Orighomisan Woods, Joseph Anthony,Plass, Winfried,Eseola, Abiodun Omokehinde
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- Bis(bipyridine) ruthenium(ii) bis(phosphido) metalloligand: Synthesis of heterometallic complexes and application to catalytic (E)-selective alkyne semi-hydrogenation
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The first phosphido derivative of the bis(bipyridine) ruthenium(ii) fragment, cis-[(bpy)2Ru(PPh2)2] ([RuP2]), has been developed and applied as a P-donor metalloligand to form new Ru-Rh, Ru-Ir and Ru2Cu2 heterometallic complexes. The Ru-Ir hydride complex [([RuP2])IrH(NCMe)3][BF4]2 exhibits significant catalytic activity for (E)-selective semi-hydrogenation of alkynes.
- Takemoto, Shin,Kitamura, Manami,Saruwatari, Shuhei,Isono, Atsutaka,Takada, Yoko,Nishimori, Rie,Tsujiwaki, Mina,Sakaue, Naoki,Matsuzaka, Hiroyuki
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- Layered double hydroxide supported nanopalladium catalyst for Heck-, Suzuki-, Sonogashira-, and Stille-type coupling reactions of chloroarenes
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Layered double hydroxide and Merrifield resin supported nanopalladium(0) catalysts are prepared by an exchange of PdCl42- followed by reduction and well characterized for the first time. The ligand-free heterogeneous layered double hydroxide supported nanopalladium (LDH-Pd0) catalyst using the basic LDH in place of basic ligands indeed exhibits higher activity and selectivity in the Heck olefination of electron-poor and electron-rich chloroarenes in nonaqueous ionic liquids (NAIL) over the homogeneous PdCl2 system. Using microwave irradiation, the rate of the Heck olefination reaction is accelerated, manifold with the highest turnover frequency ever recorded in the case of both electron-poor and electron-rich chloroarenes. The basic LDH-Pd0 shows a superior activity over a range of supported catalysts, from acidic to weakly basic Pd/C, Pd/SiO2, Pd/Al2O3, and resin-PdCl42- in the Heck olefination of deactivated electron-rich 4-chloroanisole. The use of LDH-Pd0 is extended to the Suzuki-, Sonogashira-, and Stille-type coupling reactions of chloroarenes in an effort to understand the scope and utility of the reaction. The catalyst is quantitatively recovered from the reaction by a simple filtration and reused for a number of cycles with almost consistent activity in all the coupling reactions. The heterogeneity studies provide an insight into mechanistic aspects of the Heck olefination reaction and evidence that the reaction proceeds on the surface of the nanopalladium particles of the heterogeneous catalyst. TEM images of the fresh and used catalyst indeed show that the nanostructured palladium supported on LDH remains unchanged at the end of the reaction, while the XPS and evolved gas detection by TGA-MS of the used catalyst identify ArPdX species on the heterogeneous surface. Thus, the ligand-free nanopalladium supported on LDH, synthesized by the simple protocol, displays superior activity over the other heterogeneous catalysts inclusive of nanopalladium in the C-C coupling reactions of chloroarenes.
- Choudary, Boyapati M.,Madhi, Sateesh,Chowdari, Naidu S.,Kantam, Mannepalli L.,Sreedhar, Bojja
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- Activation of CX (=Cl, Br) bond in aryl halides toward the palladium-catalyzed Heck reaction using 2,6-bis(diphenylphosphino)pyridine
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The 2,6-bis(diphenylphosphino)pyridine/palladium catalytic system successfully catalyzes the Heck coupling reaction of less reactive aryl chlorides as well as aryl bromides with styrene to give the corresponding olefins in reasonable yields. TBAB (tetrabu
- Ataei, Ali,Nadri, Shirin,Rafiee, Ezzat,Jamali, Sirous,Joshaghani, Mohammad
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- Electrochemical Proton Reduction over Nickel Foam for Z-Stereoselective Semihydrogenation/deuteration of Functionalized Alkynes
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Selective reduction strategies based on abundant-metal catalysts are very important in the production of chemicals. In this paper, a method for the electrochemical semihydrogenation and semideuteration of alkynes to form Z-alkenes was developed, using a simple nickel foam as catalyst and H3O+ or D3O+ as sources of hydrogen or deuterium. Good yields and excellent stereoselectivities (Z/E up to 20 : 1) were obtained under very mild reaction conditions. The reaction proceeded with terminal and nonterminal alkynes, and also with alkynes containing easily reducible functional groups, such as carbonyl groups, as well as aryl chlorides, bromides, and even iodides. The nickel-foam electrocatalyst could be recycled up to 14 times without any change in its catalytic properties.
- Valiente, Alejandro,Martínez-Pardo, Pablo,Kaur, Gurpreet,Johansson, Magnus J.,Martín-Matute, Belén
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- Controlling Multiple Active Sites on Pd?CeO2 for Sequential C?C Cross-coupling and Alcohol Oxidation in One Reaction System
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Ceria (CeO2)-supported metal catalysts have been widely utilized for various single-step chemical transformations. However, using such catalysts for a multistep organic reaction in one reaction system has rarely been achieved. Here, we investigate multiple active sites on Pd?CeO2 catalysts and optimize them for a multistep reaction of C?C cross-coupling and alcohol oxidation. Atomic-level imaging and spectroscopic studies reveal that metallic Pd0 and Pd?CeO2 interface are active sites on Pd?CeO2 for C?C cross-coupling and oxidation, respectively. These active sites are controlled under the structural evolution of Pd?CeO2 during reductive heat-treatments. Accordingly, we found that optimally reduced Pd?CeO2 catalysts containing ～1.5 nm-sized Pd nanoclusters with both sites in balance are ideal for multistep chemical transformations in one reaction system. Our strategy to design supported metal catalysts leads to one-pot sequential synthetic protocols for pharmaceutical building blocks.
- Ko, Wonjae,Kim, Ju Hee,Yim, Guk Hee,Lee, Seong Chan,Kim, Sumin,Kwak, Minjoon,Choi, Hyunwoo,Kim, Jongchan,Antink, Wytse Hooch,Kim, Jiheon,Lee, Chan Woo,Bok, Jinsol,Jung, Yoon,Lee, Eunwon,Lee, Kug-Seung,Cho, Sung-Pyo,Kim, Do Heui,Kim, Young Gyu,Lee, Byoung-Hoon,Hyeon, Taeghwan,Yoo, Dongwon
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- New Bidentate N-Sulfonyl-Substituted Aromatic Amines as Chelate Ligand Backbones: Pd Catalyst Generation in C-C Coupling via in Situ and Precatalyst Modes
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A series of six new, bidentate ligands based on N-(2-(R-sulfonamido)benzyl)R-sulfonamide have been isolated as dianionic or monoanionic chelators via condensation of 2-(aminomethyl)aniline with sulfonyl chloride reagents; R = methyl (1 and 1′), tolyl (2 and 2′), 2,4,6-Trimethylphenyl (3), or 2,4,6-Triisopropylphenyl (4). Complexes of ligands 2-4 reacted at room temperature with palladium(ii) acetate in the presence of various monodentate N-donor co-ligands to form complexes Pd2(2dmap), Pd2′(OAc.py), Pd3(2acn), Pd3(2py), Pd4(2acn), and Pd4(2py), which were structurally confirmed by three X-ray crystal analyses. Results of catalysis studies in water showed high turnover frequencies and yields of up to 98 % within 10 min and at 0.2 mol-% palladium catalyst loading. Relative to ligand-free catalysis in the presence of only Pd(OAc)2, the ligand-supported palladium species clearly possess positive catalytic advantage. Furthermore, Suzuki coupling efficiencies by 1: 1 'Pd(OAc)2 + ligand' yielded notably better outcomes than for the 1: 2 'Pd(OAc)2 + ligand' in situ catalyst generation, which reveals that coordinative saturation is undesirable. The size of the complementing monodentate co-ligand was observed to influence the catalytic efficiency such that bulkier co-ligands consistently yielded improved turnover frequency values, which leads to the conclusion that steric repulsion between the synthesised ligands and the bulkier co-ligands aided the generation of vacant coordination sites for the more active complexes. Moderate Heck coupling activity was recorded for the complexes and better activities appear to correlate with moderate bulkiness of ligand 3.
- Oloyede, Hammed Olawale,Akong Akong, Raymond,Woods, Joseph Anthony Orighomisan,G?rls, Helmar,Plass, Winfried,Eseola, Abiodun Omokehinde
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p. 101 - 110
(2020/07/28)
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- N-donor-stabilized Pd(II) species supported by sulphonamide-azo ligands: Ligand architecture, solvent co-ligands, C–C coupling
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In this report, a series of synthetically affordable phosphine-free ligands (L1 – L4) of the form RSO2–NH–Ph–N[dbnd]N–Ph–NH–SO2R were prepared and examined as organic ligands for stabilizing palladium active centers; R = methyl, tolyl or triiso-propylphenyl. Palladium complexes, which were obtained in varying coordination environments as well as with varying complementary co-ligands (water, acetonitrile or pyridine), have been subjected to Suzuki and Heck coupling experiments in order to study molecular level ligand effects on preferred catalyst settings. The appreciable coupling activities for Suzuki and Heck coupling with functional group tolerance were recorded for palladium species generated from the chelate ligands. Results show that, despite the tridentate chelation characteristics of these azo-benzene ligands, the introduction of bulky units at the sulfonyl groups enabled generation of active palladium species with high turnover frequencies; e.g. 5040 h?1 (84% yield) within 5 min at 0.2 mol % loading of Pd.L2.py in only water as solvent. A correlation between catalytic efficiencies and the bulkiness of the coordinated co-ligand was obtained. However, while Suzuki coupling activity increased with increase in co-ligand sizes of the preformed complexes (i.e. water acetonitrile pyridine), the pyridyl co-ligand turned out to be very unfavourable for Heck coupling where the acetonitrile-complemented complexes possessed the higher activities. Therefore, it could be concluded that the best catalyst setting for Suzuki coupling may not be the best for Heck reaction.
- Oloyede, Hammed Olawale,Orighomisan Woods, Joseph Anthony,G?rls, Helmar,Plass, Winfried,Eseola, Abiodun Omokehinde
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- General and Phosphine-Free Cobalt-Catalyzed Hydrogenation of Esters to Alcohols
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Catalytic hydrogenation of esters is essential for the sustainable production of alcohols in organic synthesis and chemical industry. Herein, we describe the first non-noble metal catalytic system that enables an efficient hydrogenation of non-activated esters to alcohols in the absence of phosphine ligands (with a maximum turnover number of 2391). The general applicability of this protocol was demonstrated by the high-yielding hydrogenation of 39 ester substrates including aromatic/aliphatic esters, lactones, polyesters and various pharmaceutical molecules.
- Shao, Zhihui,Zhong, Rui,Ferraccioli, Raffaella,Li, Yibiao,Liu, Qiang
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supporting information
p. 1125 - 1130
(2019/10/22)
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- Regio- A nd chemoselective deprotection of primary acetates by zirconium hydrides
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A combination of DIBAL-H and Cp2ZrCl2 is shown to promote the regioselective cleavage of primary acetates on a broad scope of substrates, ranging from carbohydrates to terpene derivatives, with a high tolerance toward protecting groups and numerous functionalities found in natural products and bioactive compounds. Apart from providing highly valuable building blocks in only two steps from biosourced raw materials, this selective de-O-acetylation should also be strongly helpful to solve selectivity issues in organic synthesis.
- Gavel, Marine,Courant, Thibaut,Joosten, Antoine Yvan Philippe,Lecourt, Thomas
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supporting information
p. 1948 - 1952
(2019/04/10)
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- Direct trans-Selective Ruthenium-Catalyzed Reduction of Alkynes in Two-Chamber Reactors and Continuous Flow
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An efficient trans-selective hydrogenation of alkynes under low hydrogen pressure and low reaction temperatures is reported, applying a commercially available ruthenium hydride complex. The developed reaction conditions, which tolerate a variety of functional groups, are carried out in a two-chamber setup with ex situ generated hydrogen. The reaction setup is highly suitable for deuterium labeling. The trans-selective hydrogenation was extrapolated to a transfer hydrogenation protocol, employing a packed bed immobilized ruthenium hydride catalyst in continuous flow with a retention time of only 10 min.
- Neumann, Karoline T.,Klimczyk, Sebastian,Burhardt, Mia N.,Bang-Andersen, Benny,Skrydstrup, Troels,Lindhardt, Anders T.
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p. 4710 - 4714
(2016/07/12)
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- On the Functional Group Tolerance of Ester Hydrogenation and Polyester Depolymerisation Catalysed by Ruthenium Complexes of Tridentate Aminophosphine Ligands
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The synthesis of a range of phosphine-diamine, phosphine-amino-alcohol, and phosphine-amino-amide ligands and their ruthenium(II) complexes are reported. Five of these were characterised by X-ray crystallography. The activities of this collection of catalysts were initially compared for the hydrogenation of two model ester hydrogenations. Catalyst turnover frequencies up to 2400 h-1 were observed at 85 °C. However, turnover is slow at near ambient temperatures. By using a phosphine-diamine RuII complex, identified as the most active catalyst, a range of aromatic esters were reduced in high yield. The hydrogenation of alkene-, diene-, and alkyne-functionalised esters was also studied. Substrates with a remote, but reactive terminal alkene substituent could be reduced chemoselectively in the presence of 4-dimethylaminopyridine (DMAP) co-catalyst. The chemoselective reduction of the ester function in conjugated dienoate ethyl sorbate could deliver (2E,4E)-hexa-2,4-dien-1-ol, a precursor to leaf alcohol. The monounsaturated alcohol (E)-hex-4-en-1-ol was produced with reasonable selectivity, but complete chemoselectivity of C=O over the diene is elusive. High chemoselectivity for the reduction of an ester over an alkyne group was observed in the hydrogenation of an alkynoate for the first time. The catalysts were also active in the depolymerisation reduction of samples of waste poly(ethylene terephthalate) (PET) to produce benzene dimethanol. These depolymerisations were found to be poisoned by the ethylene glycol side product, although good yields could still be achieved. A simple catalyst for difficult reductions: Ruthenium complexes of P,N,N and P,N,O ligands catalyse the reduction of esters with high activities. The Ru complex of a phosphine-diamine ligand (see scheme) has been found to be a good catalyst for reducing alkene-, diene-, and alkyne-functionalised esters, displaying good activity and chemoselectivity. This catalyst was also active in the hydrogenation of waste poly(ethylene terephthalate) (PET).
- Fuentes, José A.,Smith, Samuel M.,Scharbert, M. Theresa,Carpenter, Ian,Cordes, David B.,Slawin, Alexandra M. Z.,Clarke, Matthew L.
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p. 10851 - 10869
(2015/07/20)
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- A mild chemoselective Ru-catalyzed reduction of alkynes, ketones, and nitro compounds
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The chemoselective reduction of alkyne, ketones, or nitro groups using (Ph3P)3RuCl2 as an inexpensive catalyst and Zn/water as a stoichiometric reductant is reported. Depending on the nature of the additive and the temperature, good chemoselectivities were observed allowing, e.g., for the selective reduction of a nitro group in the presence of a ketone or an alkyne.
- Schabel, Tobias,Belger, Christian,Plietker, Bernd
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p. 2858 - 2861
(2013/07/19)
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- Palladium(II)-catalyzed Heck reaction of aryl halides and arylboronic acids with olefins under mild conditions
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A series of general and selective Pd(II)-catalyzed Heck reactions were investigated under mild reaction conditions. The first protocol has been developed employing an imidazole-based secondary phosphine oxide (SPO) ligated palladium complex (6) as a precatalyst. The catalytic coupling of aryl halides and olefins led to the formation of the corresponding coupled products in excellent yields. A variety of substrates, both electron-rich and electron-poor olefins, were converted smoothly to the targeted products in high yields. Compared with the existing approaches employing SPO-Pd complexes in a Heck reaction, the current strategy features mild reaction conditions and broad substrate scope. Furthermore, we described the coupling of arylboronic acids with olefins, which were catalyzed by Pd(OAc)2 and employed N-bromosuccinimide as an additive under ambient conditions. The resulted biaryls have been obtained in moderate to good yields.
- Shaikh, Tanveer Mahamadali,Hong, Fung-E
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supporting information
p. 1578 - 1588
(2013/10/22)
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- Aryl-aryl interactions as directing motifs in the stereodivergent iron-catalyzed hydrosilylation of internal alkynes
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The defined Fe hydride complex FeH(CO)(NO)(Ph3P)2 is highly active as a catalyst for selective hydrosilylation of internal alkynes to vinylsilanes. Depending on the silane employed either E- or Z-selective hydrosilylation products were formed in excellent yields and good to excellent stereoselectivities.
- Belger, Christian,Plietker, Bernd
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supporting information; experimental part
p. 5419 - 5421
(2012/07/03)
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- Mizoroki-Heck reactions catalyzed by dichloro{bis[1- (dicyclohexylphosphanyl)piperidine]}palladium: Palladium nanoparticle formation promoted by (water-induced) ligand degradation
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The palladium-based dichlorobis[1-(dicyclohexylphosphanyl)piperidine] complex - [(P{(NC5H10)(C6H11) 2})2Pd(Cl)2] is readily prepared in quantitative yield from the reaction of [Pd(cod)(Cl)2] (cod=cycloocta-1,5-diene) with two equivalents of 1-(dicyclohexylphosphanyl) piperidine in toluene under N2 within only a few minutes at room temperature. This complex is a highly active Heck catalyst with excellent functional group tolerance, which reliably operates at low catalyst loadings. Various activated, non-activated, deactivated, functionalized, sterically hindered, and heterocyclic aryl bromides, which may contain nitro, chloro or trifluoromethane groups, nitriles, acetales, ketones, aldehydes, ethers, esters, lactones, amides, anilines, phenols, alcohols, carboxylic acids, and heterocyclic aryl bromides, such as pyridines and derivatives, as well as thiophenes and aryl bromides containing methylsulfanyl groups have been successfully coupled with various (also functionalized) alkenes in excellent yields and selectivities (the E-isomers are typically exclusively formed) at 140 °C in the presence of 0.05 mol % of the catalyst in DMF. Even though lower catalyst loadings could be used for many electronically activated, non-activated and some electronically deactivated aryl bromides without noticeable loss of activity, the great advantage of the reaction protocol presented here lies in its reliability and general applicability, which allows its direct adoption to other aryl bromides without the neccessity of its modification. Experimental observations indicated that palladium nanoparticles are the catalytically active form. Consequently, whereas comparable levels of activity were observed for dichloro-bis(aminophosphine) complexes of palladium, a dramatic drop in activity was found for their phosphine-based analogue [(P(C6H 11)3)2Pd(Cl)2]. Copyright
- Oberholzer, Miriam,Gerber, Roman,Frech, Christian M.
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supporting information; experimental part
p. 627 - 641
(2012/04/23)
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- An iterative approach toward the synthesis of discrete oligomeric p-phenylene vinylene organic dyes employing aqueous Wittig chemistry
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Photovoltaic research has become increasingly prominent as the search for alternatives to fossil fuels are actively sought. A novel process for the iterative synthesis of discrete donor/acceptor-flanked oligostilbenes, key constituents in dye-sensitized solar cells, is described. The aqueous Wittig process is high yielding, proceeds with high (E)-stereoselectivity and allows facile product purification.
- McNulty, James,McLeod, David
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p. 5467 - 5470
(2011/11/01)
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- Synthesis, dual fluorescence, and fluoroionophoric behavior of dipyridylaminomethylstilbenes
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The synthesis, dual fluorescence, and fluoroionophoric behavior of two donor-σ spacer-acceptor (D-s-A) compounds, trans-4-(N,N-bis(2-pyridyl) amino)methylstilbene (1H) and trans-4-(N,N-bis(2-pyridyl)amino)methyl-4′- cyanostilbene (1CN), are reported and compared to that of trans-4-(N,N-bis(2- pyridyl)amino)methyl-4′-(N,N-dimethylammo)stilbene (1DPA). To gain insights into the dual fluorescence properties for 1H and 1CN in polar but not in nonpolar solvents, model compounds resulting from a replacement of the stilbene group by alkyl (2R) or xylyl (2X) groups or from a replacement of the dipyridylamino (dpa) group by dianisoleamino (3AA), diethylamino (SEE), methylanilino (3MP), or diphenylamino (3PP) groups also have been investigated. In addition to 1H and 1CN, all four compounds of 3 display dual fluorescence. The locally excited (LE) fluorescence mainly results from the stilbene group and the ICT fluorescence from the through-bond interactions between the amino donor and the stilbene acceptors. In the presence of transition metal ions such as Zn(II), Ni(II), Cu(II), and Cd(II), the ICT processes are switched from dpa → stilbene (A) in 1H and 1CN to stilbene (D) → dpa/metal ion (A) in their complexes. Whereas the ICT states for the complexes are generally nonfluorescent, an exception was found for the case of 1H/Zn(II). As a result, substituent-dependent fluoroionophoric behavior has been demonstrated by 1H, 1CN, and 1DPA in response to Zn(II).
- Yang, Jye-Shane,Lin, Yan-Duo,Chang, Ya-Ho,Wang, Shin-Shin
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p. 6066 - 6073
(2007/10/03)
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- Bacteriorhodopsin Analogs from Diphenylpolyene Chromophores
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Chromophore-modified bacteriorhodopsin (bR) analogs are prepared, to study the nature of chromophore-protein interaction as well as to develop new bR analogs that can find applications as photoactive element in molecular electronic devices. This article describes the preparation and characterization of hitherto unknown bR analogs based on diphenylpolyene chromophores. Diphenylpolyene compounds, namely, 4-[(E)-2-phenylvinyl]benzaldehyde (1), 3-methyl-5-{4-[(E)-2-phenylvinyl]phenyl}penta-2E,4E-dienal (2), 4-[4-phenylbuta-1E,3E-dienyl]benzaldehyde (3) and 3-methyl-5-{4-[4-phenylbuta-1E,3E-dienyl]phenyl}penta-2E,4E-dienal (4), have been synthesized, and their interaction with bacterioopsin (bOP) has been studied. Whereas aldehydes 2 and 4 interact with bOP and yield bR analogs bR-2 and bR-4, aldehydes 1 and 3 do not yield any pigment. Analogs bR-2 and bR-4 have been characterized for their opsin shift, competitive binding, photochemical properties and fluorescence spectral behavior.
- Singh, Anil K.,Manjula
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p. 503 - 510
(2007/10/03)
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