- Synthesis of insoluble polystyrene-supported flavins and their catalysis in aerobic reduction of olefins
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2′,4′-p-Vinylbenzylideneriboflavin (2′,4′-PVBRFl) was prepared as a flavin-containing monomer and copolymerized with divinylbenzene and styrene or its p-substituted derivatives such as 4-acetoxystyrene, 4-vinylbenzyl alcohol, and 4-vinylbenzoic acid to give the corresponding non-functionalized and functionalized PS-DVB-supported flavins PS(H)-DVB-Fl, PS(OAc)-DVB-Fl, PS(CH2OH)-DVB-Fl, and PS(COOH)-DVB-Fl, respectively. PS(OH)-DVB-Fl was also prepared by hydrolysis of PS(OAc)-DVB-Fl under basic conditions. These novel flavin-containing insoluble polymers exhibited characteristic fluorescence in solid state, except PS(OH)-DVB-Fl, and different catalytic activities in aerobic reduction of olefins by in situ generated diimide from hydrazine depending on their pendant functional group. For example, PS(H)-DVB-Fl was found to be particularly effective for neutral hydrophobic substrates, which could be readily recovered by a simple filtration and reused more than 10 times without loss in catalytic activity. On the other hand, PS(OH)-DVB-Fl and PS(COOH)-DVB-Fl proved to be highly active for phenolic substrates known to be less reactive in the reaction with conventional non-supported flavin catalysts.
- Arakawa, Yukihiro,Kawachi, Risa,Tezuka, Yoshihiko,Minagawa, Keiji,Imada, Yasushi
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- Improved preparation of secondary zinc iodides by 1,2-migration of sp3 carbenoids
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R2Zn in the presence of NMP or LiBr promotes the intramolecular rearrangement of 1,1-diiodoalkanes via the formation of sp3 secondary zinc carbenoid.
- Shibli,Varghese,Knochel,Marek
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- Alkene Hydrogenations by Soluble Iron Nanocluster Catalysts
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The replacement of noble metal technologies and the realization of new reactivities with earth-abundant metals is at the heart of sustainable synthesis. Alkene hydrogenations have so far been most effectively performed by noble metal catalysts. This study reports an iron-catalyzed hydrogenation protocol for tri- and tetra-substituted alkenes of unprecedented activity and scope under mild conditions (1–4 bar H2, 20 °C). Instructive snapshots at the interface of homogeneous and heterogeneous iron catalysis were recorded by the isolation of novel Fe nanocluster architectures that act as catalyst reservoirs and soluble seeds of particle growth.
- Gieshoff, Tim N.,Chakraborty, Uttam,Villa, Matteo,Jacobi von Wangelin, Axel
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- Efficient and rapid C-Si bond cleavage in supercritical water
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Arylsilanes, alkenylsilanes, allylic silanes, and alkylsilanes were found to undergo extremely facile and rapid C-Si bond cleavage in supercritical water. The rapid C-Si bond cleavage occurred even with robust unactivated tetraalkylsilanes. The control experiments revealed the dramatic difference between supercritical and subcritical conditions and that between supercritical water and supercritical methanol, attesting to a unique reactivity of supercritical water in C-Si bond cleavage. Copyright
- Itami, Kenichiro,Terakawa, Koji,Yoshida, Jun-ichi,Kajimoto, Okitsugu
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- Scope and Limitations of the Palladium-Catalyzed Cross-Coupling Reaction of in Situ Generated Organoboranes with Aryl and Vinyl Halides
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The in situ palladium(0)-catalyzed Suzuki reaction is shown to be an efficient method for the cross-coupling of aryl-, furyl-, primary, and benzylic boranes with aryl or vinyl bromides and iodides without the isolation of the organoboronic acid or the addition of any external base.
- Maddaford, Shawn P.,Keay, Brian A.
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- Alkylation of alkyl aromatic hydrocarbons over metal oxide-alkali metal superbasic catalysts
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The alkylation of toluene, ethylbenzene, cumene, and o-, m-, and p-xylenes with ethylene, propylene, and 1,2-diphenylethylene was studied over superbasic MgO-K and γ-Al2O3-K catalysts and over model systems of the electron donor acceptor complex type. The ethylation and propylation of alkylbenzenes indicated that the donor power and the concentration of the one-electron donor centers were not the only factors, which determined the activity (depicted by the initial reaction rate, turnover number, or alkylbenzene conversion) and selectivity of the catalytic system. In the series of reactions, a higher total conversion of alkyl aromatic hydrocarbons to their ethylation or propylation products was achieved over γ-Al2O3-K systems. The reaction chemoselectivity (mono- or difunctionalization of alkylbenzenes) depended on the nature of the alkyl aromatic reactant and alkylating alkene, on the reaction temperature, and on the used catalyst.
- Kijenski,Radomski,Fedorynska
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- Divergent Reactivity of Stannane and Silane in the Trifluoromethylation of PdII: Cyclic Transition State versus Difluorocarbene Release
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The transmetalation is a key elementary step in cross-coupling reactions. Yet, the precise nature of its mechanism and transition state geometry are frequently elusive. This report discloses our study of the transmetalation of [PdII]-F complexes with the silane- and stannane-based trifluoromethylation agents, R3SiCF3 and R3SnCF3. A divergent reactivity was uncovered, with the stannane showing selective R-group transfer, and the silane selective CF3-group transfer. Using a combined experimental and computational approach, we uncovered a hitherto unrecognized transmetalation mechanism with the widely employed R3SiCF3 reagent, explaining its unique activity in metal-catalyzed trifluoromethylations. While the stannane reacts via a cyclic, 4-membered transition state, the silane undergoes a fundamentally different pathway and releases a difluorocarbene in the transmetalation event. Molecular dynamics studies clearly reinforced the liberation of a free CF2 carbene, which reacts with [PdII]-F to ultimately generate [PdII]-CF3.
- Pu, Maoping,Sanhueza, Italo A.,Senol, Erdem,Schoenebeck, Franziska
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- Cross-coupling in a flow microreactor: Space integration of lithiation and murahashi coupling
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Going with the flow: The use of palladium catalysts bearing a carbene ligand resulted in a faster Murahashi coupling, and enabled its integration with the Br-Li exchange of ArBr with Bu-Li in a microreactor (see picture). This system allows the cross-coupling of two different arylbromides within a minute without necessitating low temperatures (-78°C).
- Nagaki, Aiichiro,Kenmoku, Akira,Moriwaki, Yuya,Hayashi, Atsushi,Yoshida, Jun-Ichi
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- Photoinduced, Copper-Catalyzed Alkylation of Amines: A Mechanistic Study of the Cross-Coupling of Carbazole with Alkyl Bromides
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We have recently reported that a variety of couplings of nitrogen, sulfur, oxygen, and carbon nucleophiles with organic halides can be achieved under mild conditions (-40 to 30 °C) through the use of light and a copper catalyst. Insight into the various mechanisms by which these reactions proceed may enhance our understanding of chemical reactivity and facilitate the development of new methods. In this report, we apply an array of tools (EPR, NMR, transient absorption, and UV-vis spectroscopy; ESI-MS; X-ray crystallography; DFT calculations; reactivity, stereochemical, and product studies) to investigate the photoinduced, copper-catalyzed coupling of carbazole with alkyl bromides. Our observations are consistent with pathways wherein both an excited state of the copper(I) carbazolide complex ([CuI(carb)2]-) and an excited state of the nucleophile (Li(carb)) can serve as photoreductants of the alkyl bromide. The catalytically dominant pathway proceeds from the excited state of Li(carb), generating a carbazyl radical and an alkyl radical. The cross-coupling of these radicals is catalyzed by copper via an out-of-cage mechanism in which [CuI(carb)2]- and [CuII(carb)3]- (carb = carbazolide), both of which have been identified under coupling conditions, are key intermediates, and [CuII(carb)3]- serves as the persistent radical that is responsible for predominant cross-coupling. This study underscores the versatility of copper(II) complexes in engaging with radical intermediates that are generated by disparate pathways, en route to targeted bond constructions.
- Ahn, Jun Myun,Ratani, Tanvi S.,Hannoun, Kareem I.,Fu, Gregory C.,Peters, Jonas C.
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- Solventless Suzuki coupling reactions on palladium-doped potassium fluoride alumina
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A solventless Suzuki coupling reaction has been developed which utilizes a commercially available potassium fluoride alumina mixture and palladium powder. The new reaction is convenient, environmentally friendly, and generates good yields of the coupled products. Aryl iodides react faster than the bromides or chlorides; aryl groups are also more reactive than alkenyl groups, which react faster than alkyl groups. The use of microwave irradiation accelerates the reaction, decreasing reaction times from hours to minutes. The palladium powder catalyst can be recycled using a simple filtration and washing sequence without loss of catalytic activity.
- Kabalka, George W.,Wang, Lei,Pagni, Richard M.,Hair, C. Maxwell,Namboodiri, Vasudevan
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- The Role of LiBr and ZnBr2 on the Cross-Coupling of Aryl Bromides with Bu2Zn or BuZnBr
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The impact of LiBr and ZnBr2 salts on the Negishi coupling of alkylZnBr and dialkylzinc nucleophiles with both electron-rich and -poor aryl electrophiles has been examined. Focusing only on the more difficult coupling of deactivated (electron-rich) oxidative addition partners, LiBr promotes coupling with BuZnBr, but does not have such an effect with Bu2Zn. The presence of exogenous ZnBr2 shuts down the coupling of both BuZnBr and Bu2Zn, which has been shown before with alkyl electrophiles. Strikingly, the addition of LiBr to Bu2Zn reactions containing exogenous ZnBr2 now fully restores coupling to levels seen without any salt present. This suggests that there is a very important interaction between LiBr and ZnBr2. It is proposed that Lewis acid adducts are forming between ZnBr2 and the electron-rich Pd0 centre and the bromide from LiBr forms inorganic zincates that prevent the catalyst from binding to ZnBr2. This idea has been supported by catalyst design as chlorinating the backbone of the NHC ring of Pd-PEPPSI-IPent to produce Pd-PEPPSI-IPentCl catalyst now gives quantitative conversion, up from a ceiling of only 50 % with the former catalyst.
- Eckert, Philip,Organ, Michael G.
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- Nickel- and palladium-catalyzed cross-coupling reaction of polyfluorinated arenes and alkenes with grignard reagents
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The cross-coupling reaction of fluorobenzene with an aryl Grignard reagent has been reinvestigated which revealed that the reaction readily proceeds under ordinary conditions using a catalytic amount of NiCl2(dppp) even at room temperature. The use of nickel catalysts and Grignard reagent is essential for the activation of the carbon-fluorine bond. The palladium catalyst is also effective for the 1,2-difluorobenzene and trifluorobenzenes to selectively produce the corresponding mono-coupled products while the nickel-based catalyst system affords a mixture of the mono-coupled product and di- or tri-coupled product. Georg Thieme Verlag Stuttgart.
- Saeki, Tomoyuki,Takashima, Yohei,Tamao, Kohei
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- Arene-Metal Complexes. 12. Reaction of (η6-Benzene)tricarbonylchromium with n-Butyllithium
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The reaction of (η6-benzene)tricarbonylchromium with n-butyllithium in tetrahydrofuran at -20 deg C results in the formation of an intermediate which may be quenched by the addition of methyl iodide or iodine to yield (toluene)tricarbonylchromium or (iodobenzene)tricarbonylchromium in 50 or 26percent yield,respectively.The chemistry and the 1H NMR spectrum of this intermediate are consistent with its assignment as (η6-phenyllithium)tricarbonylchromium.If this intermediate is allowed to warm to 0 deg C in the presence of an excess of n-butyllithium,n-butylbenzene is obtained in 80percent yield.Mechanistic details are discussed.
- Card, Roger J.,Trahanovsky, Walter S.
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- Side-chain alkylation of toluene with propene on caesium/nanoporous carbon catalysts
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Caesium/nanoporous carbon materials are powerful solid-base catalysts, promoting the side-chain alkylation toluene with propene in a continuous flow reactor conditions as mild as 150°C and 50 psig.
- Stevens, Mark G.,Anderson, Melony R.,Foley, Henry C.
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- Batch to flow deoxygenation using visible light photoredox catalysis
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Herein we report a one-pot deoxygenation protocol for primary and secondary alcohols developed via the combination of the Garegg-Samuelsson reaction, visible light-photoredox catalysis, and flow chemistry. This procedure is characterized by mild reaction conditions, easy-to-handle reactants and reagents, excellent functional group tolerance, and good yields.
- Nguyen, John D.,Reiss, Barbara,Dai, Chunhui,Stephenson, Corey R. J.
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- PHOTOCHEMICAL TRANSFORMATIONS - V ORGANIC IODIDES (Part 4) : SOLUTION PHOTOCHEMISTRY OF 4-PHENYL-1-IODOBUTANE AND 4-PHENYL-1-BROMOBUTANE
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Evidence is presented to show that product development from photolysis of 4-phenyl-1-iodobutane occurs essentially from an ionic species.This conclusion is in accord with our earlier suggestion that in the photocyclization of citronellyl iodide and related compounds, carbocations are involved.
- Subbarao, Kanury V.,Damodaran, N.P.,Dev, Sukh
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- Stille reactions with tetraalkylstannanes and phenyltrialkylstannanes in low melting sugar-urea-salt mixtures
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The transfer of simple alkyl groups in Stille reactions usually requires special solvents (HMPA) or certain organotin reagents (stannatranes, monoorganotin halides) to be efficient. Using low-melting mixtures of sugar, urea and inorganic salt as solvent, a fast and efficient palladium-catalyzed alkyl transfer with tetraalkyltin reagents was observed. The high polarity and nucleophilic character of the solvent melt promotes the reaction. Stille biaryl synthesis using electron-poor and electron-rich aryl bromides proceeds with quantitative yields in the sugar-urea-salt melt. Catalyst loading may be reduced to 0.001 mol% and the catalyst melt mixture remains active in several reaction cycles. Showing the same or improved performance for Stille reactions than organic solvents and allowing a very simple work up, sugar-urea-salt melts are a non-toxic and cheap alternative reaction medium available in bulk quantities for the catalytic process.
- Imperato, Giovanni,Vasold, Rudolf,Koenig, Burkhard
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- A RE-EXAMINATION OF THE PALLADIUM-CATALYZED CROSS COUPLING OF ALKYL IODIDES WITH ALKYL GRIGNARD REAGENTS
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Reaction of primary alkyl halides with Girgnard reagents in the presence of (dppf)Pd(O) or (dppf)PdCl2 leads to the reduction of the halide.
- Yuan, Kaixu,Scott, William J.
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- PREPARATION OF ALKYLBENZENES FROM 1-ALKYLCYCLOHEX-2-ENOLS VIA TRICARBONYLIRON COMPLEXES
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Tertiary cyclohex-2-enols are converted directly to the related tricarbonyl-1,3-cyclohexadieneiron complexes, in good yield.Tricarbonylcyclohexadienyliron salts are conveniently oxidized to the corresponding alkylbenzenes, by cerium(IV) salts.These reactions were incorporated in a procedure of converting the cyclohexenols to aromatics, suitable for the preparation of materials specifically labelled with carbon isotopes.
- Farcasiu, D.,Marino, Gaye
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- A facile synthesis of a solvent-dispersible magnetically recoverable Pd0 catalyst for the C-C coupling reaction
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Solvent-dispersible magnetite particles (Fe3O4) functionalized with dopamine (DA) and N,N-dimethylglycine (DMG) were successfully prepared by a one-pot synthesis method with environment-friendly materials. Then Pd0 nanoparticles were anchored onto the functionalized Fe3O4. The prepared materials were thoroughly characterized by TEM, XRD, XPS, FT-IR and VSM. The resultant magnetically recoverable Pd catalyst exhibited excellent catalytic activity for the C-C coupling reaction. In addition, this catalyst revealed high efficiency and stability during recycling stages. This work should be useful for the development and application of a magnetically recoverable Pd catalyst on the basis of green chemistry principles.
- Wu, Li,Yuan, Bin,Liu, Mengmeng,Huo, Hongfei,Long, Yu,Ma, Jiantai,Lu, Gongxuan
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- Tetramethylammonium phenyltrialkylborates in the photoinduced electron transfer reaction with benzophenone. Generation of alkyl radicals and their addition to activated alkenes
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Photoinduced one electron oxidation of tetramethylammonium phenyltrialkylborates by the excited state of benzophenone in an acetonitrile/benzene solution containing an excess of activated alkene produces substantially more than one equivalent of the alkyl radicals. The corresponding adducts of alkyl radicals to the alkenes are produced in good yields. No phenyl radical adducts are observed.
- Polykarpov, Alexander Y.,Neckers, Douglas C.
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- Catalytic hydrogenation of liquid alkenes with a silica-grafted hydride pincer iridium(III) complex: Support for a heterogeneous mechanism
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The previously reported silica-grafted iridium(III) hydride complex [IrH(O-SBA-15)(POCOP)] (2), prepared by treating [IrH2(POCOP)] (1) (POCOP is 1,3-bis((di-tert-butylphosphino)oxy)benzene) with SBA-15 (mesoporous silica), hydrogenates liquid alkenes (1-decene, trans-5-decene, cyclohexene, styrene, and 4-phenyl-1-butene) at room temperature and under 1 atm H2. Internal alkenes react at a lower rate than the terminal ones. For the sake of comparison, the hydrogenation of the same substrates was studied with the homogeneous catalyst [IrH2(POCOP)] (1). The heterogeneous catalyst 2 hydrogenates 1-decene, cyclohexene, and 4-phenyl-1-butene faster than 1, whereas the opposite is true for styrene and trans-5-decene, which suggests that different active species are involved in the heterogeneous and homogeneous reactions. Catalysis by a truly heterogeneous species is supported by a series of "hot filtration tests". NMR spectroscopic studies showed that 2 does not undergo degrafting upon longer exposure to alkenes compared to ethene under hydrogenation conditions.
- Rimoldi,Fodor,Van Bokhoven,Mezzetti
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- Efficient and facile Ar-Si bond cleavage by montmorillonite KSF: Synthetic and mechanistic aspects of solvent-free protodesilylation studied by solution and solid-state MAS NMR
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(Chemical Equation Presented) A facile and efficient method for the cleavage of the Ar-Si bond of various aryl trimethyl silanes is described. When adsorbed on montmorillonite KSF (mont KSF), these aryl-silanes readily undergo a solvent-free protodesilylation to the corresponding arenes at room temperature in excellent yields. This approach seems to be superior to the traditional mild methods (i.e., desilylation by TFA, TBAF, CsF), in terms of reaction yield, rate, and environmentally benign conditions. Some mechanistic studies using both solution and solid-state magic-angle spinning (SS MAS) 1H NMR are also presented.
- Zafrani, Yossi,Gershonov, Eytan,Columbus, Ishay
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- Deep compositional understanding of TBA: AlCl3 ionic liquid for its applications
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Chloroaluminate ionic liquids (ILs) have been immensely used as homogeneous catalyst in Friedel-Crafts reaction. We have recently synthesized chloroaluminate ILs by reacting aluminium chloride with a hydrophobic neutral ligand i.e. tributylamine (TBA:AlCl3). The current study elaborates on the investigations of the composition of the ionic liquids at various stages of their formation. The ionic liquids were synthesized using various mole ratios of tributyl amine and aluminium chloride in range of 1:1 to 1:2.3, in presence of an aromatic solvent in a one pot reaction. Various characterization techniques like Mass spectrometry, 27Al Nuclear Magnetic Resonance, 31P Nuclear Magnetic Resonance and Fourier Transform Infrared spectroscopy were used to elucidate the formation of various moieties of the TBA:AlCl3 Ionic Liquid. This study also elaborates on the investigations of the cationic and anionic moieties and their structure-property relationship for various applications. Various Friedel-Crafts reaction of industrial importance were performed using the ionic liquid having (Al2Cl7)?moiety to assess its performance and compared with conventional processes. The synthesized products were characterised by sophisticated analytical techniques like 1H NMR, 13C NMR, FTIR, GC–MS, GC-FID, to name a few. This class of ionic liquids also have importance in various electrochemical applications like aluminium deposition and aluminium batteries.
- Bhakthavatsalam, Vishnupriya,Chandra, Sudeshna,Choudhury, Rudra Prosad,Lande, Sharad V.,Pradhan, Jeevan,Sakhalkar, Mangesh
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- Palladium-indium-indium(III) chloride-mediated allyl cross-coupling reactions using allyl acetates
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Allylindiums in situ generated by reductive transmetalation of π-allylpalladium(II) complexes, obtained from allyl acetates and palladium(0) catalyst, with indium and indium(III) chloride are effective nucleophilic cross-coupling partners in Pd-catalyzed allyl cross-coupling reactions with a variety of electrophilic cross-coupling partners.
- Lee, Phil Ho,Seomoon, Dong,Lee, Kooyeon,Kim, Sundae,Kim, Hyunseok,Kim, Hyun,Shim, Eunkyong,Lee, Miae,Lee, Seokju,Kim, Misook,Sridhar, Madabhushi
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- Potassium hydroxide as a promoter for the potassium-metal catalyzed side-chain alkylation of toluene
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Potassium hydroxide acts synergistically with catalyst supports such as alumina, diatomaceous earth, or potassium carbonate to promote the potassium-metal catalyzed side-chain alkylation of toluene with propene.Carrying out the reaction with wet toluene to generate KOH in situ is a particularly effective method for promoting the reaction.The catalyst supports are not inert in the absence of the promoter, because they alter alkylation regiochemistry and increase the formation of methylindan by-products.As a mechanistic probe, the amounts of benzylpotassium that formare compared with propylation reaction rates.This is the first report concerning the amount of benzylpotassium that forms under side-chain alkylation conditions.From this and other data, a previously unrecognized mechanism for the promotion of side-chain alkylation is identified.
- Smith, R. Scott,Ihrman, Kryn G.,LeBlanc, Monica B.
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- Higher-order zincates as transmetalators in alkyl-alkyl Negishi cross-coupling
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Negishi revisited: Higher-order alkyl zincates have been subjected to Negishi coupling with alkyl bromides. For the first time, coupling takes place in straight THF, i.e., without a salt additive and a high dielectric co-solvent. This provides evidence that it is the higher-order zincate that undergoes transmetalation to Pd, and not mono-anionic zincates or any of the other species present in the Schlenk equilibrium. Copyright
- McCann, Lucas C.,Hunter, Howard N.,Clyburne, Jason A. C.,Organ, Michael G.
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- Preparation of flavin-containing mesoporous network polymers and their catalysis
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Riboflavin tetramethacrylate (RFlTMA) was prepared as a flavin monomer and copolymerized with ethylene glycol dimethacrylate (EGDMA) under polymerization-induced phase separation conditions. The resulting flavin-containing mesoporous network polymer, poly(RFlTMA-co-EGDMA), was found to be a more effective catalyst than riboflavin tetraacetate (RFlTA), a soluble analogue, for aerobic hydrogenation of olefins despite its heterogeneity, which allowed for its multiple recovery and reuse through simple filtrations and washings without loss in catalytic activity. In addition, the polymeric flavin was demonstrated to be utilized also as an effective photocatalyst in the oxidation of benzyl alcohols.
- Arakawa, Yukihiro,Sato, Fumiaki,Ariki, Kenta,Minagawa, Keiji,Imada, Yasushi
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- Mononuclear calcium complex as effective catalyst for alkenes hydrogenation
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Hydrogenolysis of the scorpionate-supported calcium benzyl complex [(TpAd,iPr)Ca(p-CH2C6H4-Me)(THP)] (TpAd,iPr= hydrotris(3-adamantyl-5-isopropyl-pyrazolyl)borate, THP = tetrahydropyran) (2-THP) afforded the mononuclear calcium hydrido complex [(TpAd,iPr)Ca(H)(THP)] (3). Under mild conditions (40 °C, 10 atm H2, 5 mol% cat.), complex3effectively catalyzed the hydrogenation of a variety of alkenes, including activated alkenes, semi-activated alkenes, non-activated terminal and internal alkenes. Mononuclear calcium unsubstituted alkyl complex [(TpAd,iPr)Ca{(CH2)4Ph}(THP)] (6), proposed as the catalytic hydrogenation intermediate, was isolated and structurally characterized.
- Shi, Xianghui,Hou, Cuiping,Zhao, Lanxiao,Deng, Peng,Cheng, Jianhua
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- Connecting Organometallic Ni(III) and Ni(IV): Reactions of Carbon-Centered Radicals with High-Valent Organonickel Complexes
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This paper describes the one-electron interconversions of isolable NiIII and NiIV complexes through their reactions with carbon-centered radicals (R?). First, model NiIII complexes are shown to react with alkyl and aryl radicals to afford NiIV products. Preliminary mechanistic studies implicate a pathway involving direct addition of a carbon-centered radical to the NiIII center. This is directly analogous to the known reactivity of NiII complexes with R?, a step that is commonly implicated in catalysis. Second, a NiIV-CH3 complex is shown to react with aryl and alkyl radicals to afford C-C bonds via a proposed SH2-type mechanism. This pathway is leveraged to enable challenging H3C-CF3 bond formation under mild conditions. Overall, these investigations suggest that NiII/III/IV sequences may be viable redox pathways in high-oxidation-state nickel catalysis.
- Bour, James R.,Ferguson, Devin M.,McClain, Edward J.,Kampf, Jeff W.,Sanford, Melanie S.
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- Nickel-catalyzed cross-coupling reaction of Grignard reagents with alkyl halides and tosylates: Remarkable effect of 1,3-butadienes
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A new method for the cross-coupling reaction of Grignard reagents with alkyl chlorides, bromides, and tosylates has been developed by the use of a nickel catalyst in the presence of a diene as an additive. This reaction proceeds efficiently at 0-25 °C in THF using primary and secondary alkyl and aryl Grignard reagents. Nickel complexes bearing no phosphine ligands, such as NiCl2, Ni(acac)2, and Ni(COD)2, afford the coupling products in good yields, whereas NiCl2(PPh3)2 and NiCl2(dppp) were less effective. 1,3-Butadiene shows the highest activity as an additive for the present coupling reaction. A plausible reaction pathway was proposed. Copyright
- Terao, Jun,Watanabe, Hideyuki,Ikumi, Aki,Kuniyasu, Hitoshi,Kambe, Nobuaki
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- Cyanophenylation of aromatic nitriles by terephthalonitrile dianion: Is the charge-transfer complex a key intermediate?
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The interaction of terephthalonitrile (1) dianion (12-) with benzonitrile (2) or m-tolunitrile (3) provides 4,4′-dicyanobiphenyl (4) or 4,4′-dicyano-2-methylbiphenyl (5), respectively. This result shows that dianion 12- serves as a reagent for p-cyanophenylation of aromatic nitriles. Based on experimental data, such as the chemical trapping of the 4,4′-dicyanobiphenyl precursor 4-cyano-1-(p-cyanophenyl)cyclohexa-2,5-dienyl anion (7) and the failure to obtain biphenyl 4 through the interaction of independently generated radical anions (RAs) 1- and 2-, as well as on the results of quantum-chemical calculations, a mechanism is suggested that includes a charge-transfer complex (CTC) between 12- and the aromatic nitrile as the key intermediate. The formation of this CTC is followed either by an intracomplex electron transfer (ET) and recombination of terephthalonitrile and aromatic nitrile RAs within an unequilibrated RA pair, or by synchronous ET and bonding of the ipso-carbon atom of terephthalonitrile with the p-carbon atom of the aromatic nitrile. The synthetic significance of p-cyanophenylation of arenecarbonitriles by dianion 12- is illustrated by the high yield of biphenyl product 4 (approx. 90%) as well as by the possibility of a one-pot synthesis of 4-butyl-4′-cyanobiphenyl and 4-butyl-4′-cyano-2-methylbiphenyl by successive treatment of dianion 12- with nitrile 2 or 3 and butyl bromide. Wiley-VCH Verlag GmbH & Co, KGaA, 69451 Weinheim, Germany, 2005.
- Panteleeva, Elena V.,Shchegoleva, Lyudmila N.,Vysotsky, Viktor P.,Pokrovsky, Leonid M.,Shteingarts, Vitalij D.
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- Palladium-Catalyzed Synthesis of Arylamines from Aryl Halides. Mechanistic Studies Lead to Coupling in the Absence of Tin Reagents
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The reaction of aryl halides with secondary amines in the presence of silylamide base and tri-o-tolyphopshine palladium complexes gives arylamine products.This process provides a convenient method for performing these heterocross coupling reactions without the necessity for forming tin amides and disposing of tin halides.This reaction follows from a mechanistic analysis of the coupling reaction with tin amides and occurs as a result of the cleavage of palladium aryl halide dimers with secondary amines.
- Louie, Janis,Hartwig, John F.
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- Cobalt-catalyzed alkene hydrogenation by reductive turnover
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Earth abundant metal catalysts hold advantages in cost, environmental burden and chemoselectivity over precious metal catalysts. Differences in reactivity for a given metal center result from ligand field strength, which can promote reaction through either open- or closed-shell carbon intermediates. Herein we report a simple protocol for cobalt-catalyzed alkene reduction. Instead of using an oxidative turnover mechanism that requires stoichiometric hydride, we find a reductive turnover mechanism that requires stoichiometric proton. The reaction mechanism appears to involve coordination and hydrocobaltation of terminal alkenes.
- van der Puyl, Vincent,McCourt, Ruairi O.,Shenvi, Ryan A.
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supporting information
(2021/04/19)
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- Room temperature iron catalyzed transfer hydrogenation usingn-butanol and poly(methylhydrosiloxane)
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Reduction of carbon-carbon double bonds is reported using a three-coordinate iron(ii) β-diketiminate pre-catalyst. The reaction is believed to proceedviaa formal transfer hydrogenation using poly(methylhydrosiloxane), PMHS, as the hydride donor and a bio-alcohol as the proton source. The reaction proceeds well usingn-butanol and ethanol, withn-butanol being used for substrate scoping studies. Allyl arene substrates, styrenes and aliphatic substrates all undergo reduction at room temperature. Unfortunately, clean transfer of a deuterium atom usingd-alcohol does not take place, indicating a complex catalytic mechanism. However, changing the deuterium source tod-aniline gives close to complete regioselectivity for mono-deuteration of the terminal position of the double bond. Finally, we demonstrate that efficient dehydrocoupling of alcohol and PMHS can be undertaken using the same pre-catalyst, giving high yields of H2within 30 minutes at room temperature.
- Coles, Nathan T.,Linford-Wood, Thomas G.,Webster, Ruth L.
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supporting information
p. 2703 - 2709
(2021/04/21)
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- Selective upgrading of biomass-derived benzylic ketones by (formic acid)–Pd/HPC–NH2 system with high efficiency under ambient conditions
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Upgrading biomass-derived phenolic compounds provides a valuable approach for the production of higher-value-added fuels and chemicals. However, most established catalytic systems display low hydrodeoxygenation (HDO) activities even under harsh reaction conditions. Here, we found that Pd supported on –NH2-modified hierarchically porous carbon (Pd/HPC–NH2) with formic acid (FA) as hydrogen source exhibits unprecedented performance for the selective HDO of benzylic ketones from crude lignin-derived oxygenates. Designed experiments and theoretical calculations reveal that the H+/H? species generated from FA decomposition accelerates nucleophilic attack on carbonyl carbon in benzylic ketones and the formate species formed via the esterification of intermediate alcohol with FA expedites the cleavage of C–O bonds, achieving a TOF of 152.5 h?1 at 30°C for vanillin upgrading, 15 times higher than that in traditional HDO processes (～10 h?1, 100°C–300°C). This work provides an intriguing green route to produce transportation fuels or valuable chemicals from only biomass under mild conditions.
- Chen, Yuzhuo,Chen, Zhirong,Gong, Yutong,Mao, Shanjun,Ning, Honghui,Wang, Yong,Wang, Zhenzhen
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p. 3069 - 3084
(2021/11/16)
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- Synthesis and catalytic application of new [{IrCl(cod)}2(μ2-diNHC)] and [{Ir(cod)(sulfonated phosphine)}2(μ2-diNHC)] complexes
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Four new dinuclear iridium(I) complexes were synthesized from the di(N-heterocyclic carbene) ligand precursors 1,1′-methylene-bis(3-benzyl-imidazolium)dichloride and 1,1′-methylene-bis(3-(2,4,6-trimethylbenzyl)imidazolium)dichloride. The complexes were fu
- Czégéni, Csilla Enik?,Horváth, Henrietta,Joó, Ferenc,Kathó, ágnes,Marozsán, Natália,Orosz, Krisztina,Papp, Gábor,Udvardy, Antal
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- Amido PNP pincer complexes of palladium(II) and platinum(II): Synthesis, structure, and reactivity
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The synthesis of a series of divalent palladium and platinum complexes containing amido PNP pincer ligands of the type [N(o-C6H4PR2)2]? (R = Ph (1a), iPr (1b)) is reported. Metathetical reactions of [1a–b]PdCl or [1a–b]PtCl with a variety of alkyl Grignard reagents or LiHBEt3 in ethereal or arene solutions generate their corresponding alkyl or hydride complexes [1a]PdR1 (R1 = Me, Et, nBu), [1b]PdR1 (R1 = Me, Et, H), [1a]PtR1 (R1 = Me, Et, nBu, nHexyl, H), and [1b]PtR1 (R1 = Me, H). Although these organometallic complexes are all thermally stable, including those containing β-hydrogen atoms even at elevated temperatures, compounds [1a]PdH and [1b]PtR1 (R1 = Et, nBu, nHexyl) are not isolable due to facile decomposition. The stability and reactivity of these complexes are discussed. The chloro [1a]PdCl is a superior catalyst precursor to [1b]PdCl, [1a]PtCl, and [1b]PtCl in Kumada couplings, affording, for instance, n-butyl arenes nearly quantitatively. The X-ray structures of [1b]PtCl, [1b]PtMe, [1b]PdEt, [1a]PtnBu, [1b]PdH, and [1b]PtH are presented.
- Huang, Mei-Hui,Lee, Wei-Ying,Zou, Xue-Ru,Lee, Chia-Chin,Hong, Sheng-Bo,Liang, Lan-Chang
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- Modular Synthesis of Carbazole-Substituted Phthalimides as Potential Photocatalysts
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The modular synthesis of carbazole functionalized phthalimides (PIs) and their applicability as catalyst in selected photocatalytic transformations are reported. The developed synthetic approach provides high variability of phthalimide considering that the synthesis of the phthalimide core can be easily performed. Starting from fluorophthalic acid anhydrides, the corresponding fluorophthalimides were prepared with various amines, and the fluoro function ensured the introduction of carbazoles into the phthalimide framework through aromatic nucleophilic substitution. Besides the synthetic developments, some of the carbazolyl phthalimides were tested in four different photocatalytic transformations, which showed attractive and comparable activity to the known 4-CzIPN and noble metal complexes.
- F?ldesi, Tamás,Gonda, Zsombor,Nagy, Bálint,Novák, Zoltán
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supporting information
(2021/11/22)
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- Reduction of α,β-unsaturated carbonyl compounds and 1,3-diketones in aqueous media, using a raney ni-al alloy
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The treatment of α,β-unsaturated carbonyl compounds and 1,3-diketones with Raney Ni-Al alloy in aqueous media yielded as major reaction products the corresponding saturated alcohols and/or the corresponding hydrocarbons, in a complete transformation of the starting material.
- Simion, Cristian,Mitoma, Yoshiharu,Katayama, Yumi,Simion, Alina Marieta
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- Photoredox catalysis on unactivated substrates with strongly reducing iridium photosensitizers
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Photoredox catalysis has emerged as a powerful strategy in synthetic organic chemistry, but substrates that are difficult to reduce either require complex reaction conditions or are not amenable at all to photoredox transformations. In this work, we show that strong bis-cyclometalated iridium photoreductants with electron-rich β-diketiminate (NacNac) ancillary ligands enable high-yielding photoredox transformations of challenging substrates with very simple reaction conditions that require only a single sacrificial reagent. Using blue or green visible-light activation we demonstrate a variety of reactions, which include hydrodehalogenation, cyclization, intramolecular radical addition, and prenylationviaradical-mediated pathways, with optimized conditions that only require the photocatalyst and a sacrificial reductant/hydrogen atom donor. Many of these reactions involve organobromide and organochloride substrates which in the past have had limited utility in photoredox catalysis. This work paves the way for the continued expansion of the substrate scope in photoredox catalysis.
- Shon, Jong-Hwa,Kim, Dooyoung,Rathnayake, Manjula D.,Sittel, Steven,Weaver, Jimmie,Teets, Thomas S.
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p. 4069 - 4078
(2021/04/06)
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- Ceramic boron carbonitrides for unlocking organic halides with visible light
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Photochemistry provides a sustainable pathway for organic transformations by inducing radical intermediates from substrates through electron transfer process. However, progress is limited by heterogeneous photocatalysts that are required to be efficient, stable, and inexpensive for long-term operation with easy recyclability and product separation. Here, we report that boron carbonitride (BCN) ceramics are such a system and can reduce organic halides, including (het)aryl and alkyl halides, with visible light irradiation. Cross-coupling of halides to afford new C-H, C-C, and C-S bonds can proceed at ambient reaction conditions. Hydrogen, (het)aryl, and sulfonyl groups were introduced into the arenes and heteroarenes at the designed positions by means of mesolytic C-X (carbon-halogen) bond cleavage in the absence of any metal-based catalysts or ligands. BCN can be used not only for half reactions, like reduction reactions with a sacrificial agent, but also redox reactions through oxidative and reductive interfacial electron transfer. The BCN photocatalyst shows tolerance to different substituents and conserved activity after five recycles. The apparent metal-free system opens new opportunities for a wide range of organic catalysts using light energy and sustainable materials, which are metal-free, inexpensive and stable. This journal is
- Yuan, Tao,Zheng, Meifang,Antonietti, Markus,Wang, Xinchen
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p. 6323 - 6332
(2021/05/19)
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- A Close-to-Aromatize Approach for the Late-Stage Functionalization through Ring Closing Metathesis
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An efficient approach for the synthesis of monosubstituted aromatic compounds relying on a ring-closing metathesis followed by spontaneous 1,2-elimination is presented. The efficiency for late-stage functionalization is highlighted in various solvents (up to 920 TON). This approach is compatible with strained cycles and other multiple bonds in the substrate.
- Lozhkin, Boris,Ward, Thomas R.
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- Site-Specific Alkene Hydromethylation via Protonolysis of Titanacyclobutanes
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Methyl groups are ubiquitous in biologically active molecules. Thus, new tactics to introduce this alkyl fragment into polyfunctional structures are of significant interest. With this goal in mind, a direct method for the Markovnikov hydromethylation of alkenes is reported. This method exploits the degenerate metathesis reaction between the titanium methylidene unveiled from Cp2Ti(μ-Cl)(μ-CH2)AlMe2 (Tebbe's reagent) and unactivated alkenes. Protonolysis of the resulting titanacyclobutanes in situ effects hydromethylation in a chemo-, regio-, and site-selective manner. The broad utility of this method is demonstrated across a series of mono- and di-substituted alkenes containing pendant alcohols, ethers, amides, carbamates, and basic amines.
- Bartfield, Noah M.,Frederich, James H.,Law, James A.
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supporting information
p. 14360 - 14364
(2021/05/27)
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- Direct Deamination of Primary Amines via Isodiazene Intermediates
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We report here a reaction that selectively deaminates primary amines and anilines under mild conditions and with remarkable functional group tolerance including a range of pharmaceutical compounds, amino acids, amino sugars, and natural products. An anomeric amide reagent is uniquely capable of facilitating the reaction through the intermediacy of an unprecedented monosubstituted isodiazene intermediate. In addition to dramatically simplifying deamination compared to existing protocols, our approach enables strategic applications of iminium and amine-directed chemistries as traceless methods. Mechanistic and computational studies support the intermedicacy of a primary isodiazene which exhibits an unexpected divergence from previously studied secondary isodiazenes, leading to cage-escaping, free radical species that engage in a chain, hydrogen-atom transfer process involving aliphatic and diazenyl radical intermediates.
- Berger, Kathleen J.,Driscoll, Julia L.,Yuan, Mingbin,Dherange, Balu D.,Gutierrez, Osvaldo,Levin, Mark D.
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supporting information
p. 17366 - 17373
(2021/11/04)
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- Hydrogenation of alkenes via cooperative hydrogen atom transfer
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Radical hydrogenation via hydrogen atom transfer (HAT) to alkenes is an increasingly important transformation for the formation of thermodynamic alkane isomers. Current single-catalyst methods require stoichiometric oxidant in addition to hydride (H-) source to function. Here we report a new approach to radical hydrogenation: cooperative hydrogen atom transfer (cHAT), where each hydrogen atom donated to the alkene arrives from a different catalyst. Further, these hydrogen atom (H?) equivalents are generated from complementary hydrogen atom precursors, with each alkane requiring one hydride (H-) and one proton (H+) equivalent and no added oxidants. Preliminary mechanistic study supports this reaction manifold and shows the intersection of metal-catalyzed HAT and thiol radical trapping HAT catalytic cycles to be essential for effective catalysis. Together, this unique catalyst system allows us to reduce a variety of unactivated alkene substrates to their respective alkanes in high yields and diastereoselectivities and introduces a new approach to radical hydrogenation.
- Kattamuri, Padmanabha V.,West, Julian G.
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supporting information
p. 19316 - 19326
(2020/11/13)
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- Palladium Nanocatalysts Encapsulated on Porous Silica @ Magnetic Carbon-Coated Cobalt Nanoparticles for Sustainable Hydrogenation of Nitroarenes, Alkenes and Alkynes.
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Palladium nanoparticles were impregnated on porous silica shell carbon-coated cobalt nanoparticles, resulting in a magnetically retrievable material that was evaluated in the catalytic hydrogenation of nitroarenes, alkenes and alkynes. The prepared material was characterized by HR-XRD, HR-TEM, elemental mapping EDX, ICP-OES and XPS analyses, revealing highly dispersed palladium nanoparticles within the porous platform that could account for the high activity observed. Mild reaction conditions, easy retrievability of the catalyst with the aid of an external magnet, recycling in four runs with a total leaching of 19 ppm (1.2 % of the initially employed Pd amount), and high stability makes this material attractive for sustainable and environmentally benign applications.
- Purohit, Gunjan,Rawat, Diwan S.,Reiser, Oliver
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p. 569 - 575
(2019/11/19)
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- Hydrodebromination of Aromatic Bromides Catalyzed by Unsupported Nanoporous Gold: Heterolytic Cleavage of Hydrogen Molecule
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Unsupported nanoporous gold (AuNPore) is a highly efficient, practically applicable, and recyclable catalyst for hydrodebromination of aromatic bromides. The AuNPore-catalyzed hydrodebromination of aromatic bromides proceeded smoothly at relatively low hydrogen pressure and temperature to achieve good to excellent yields of the corresponding non-bromine variants. The selective hydrodebromination reaction occurred exclusively in the coexistence of chlorine atom. For the first time, a mechanistic study revealed that the H?H bond splits in a heterolysis manner on the surface of AuNPore to generate Au?H hydride species.
- Bao, Ming,Feng, Xiujuan,Yamamoto, Yoshinori,Zhang, Sheng,Zhao, Yuhui
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p. 4951 - 4957
(2020/09/09)
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- Ligand assessment for the suzuki-miyaura cross coupling reaction of aryl and heteroaryl bromides with n-butylboronic acid. The advantages of buchwald's s-phos
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An investigation of biarylphosphine ligands for the Suzuki-Miyaura cross coupling reaction of aryl and heteroaryl bromides with n-butylboronic acid is presented. The results obtained on ligand modification and aryl as well as heteroaryl bromides variation represent a significant improvement in the state of the art of alkylboronic acid cross coupling methodology.
- Jagusch, Thomas,Lehnemann, Bernd,Meudt, Andreas,Nerdinger, Sven,Neuner, Sandro,Scherer, Stefan,Schottenberger, Herwig,Snieckus, Victor
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p. 631 - 644
(2020/01/31)
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- Activation of C-C Bonds via σ-Bond Metathesis: Hydroborenium-Catalyzed Hydrogenolysis of Cyclopropanes
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High-valent transition metal or main group complex mediated σ-bond metathesis plays an important role in the activation of covalent H-E bonds. However, its involvement in the activation of C-C bonds has remained elusive. Here we describe direct hydroboration of the C-C bonds of cyclopropanes by a hydroborenium complex. Our mechanism study suggests this reaction operates through a σ-bond metathesis pathway. With this hydroborenium complex as a catalyst, hydrogenolysis of unfunctionalized cyclopropanes was achieved, which is unprecedented for homogeneous catalysts and provides an unconventional approach for C-C bond functionalization in the absence of metals.
- Su, Bo,Li, Yawei,Li, Zhen Hua,Hou, Jun-Li,Wang, Huadong
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supporting information
p. 4159 - 4163
(2020/04/10)
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- Reduction of α,β-Unsaturated carbonyl compounds and 1,3-Diketones in aqueous media, using a raney ni-al alloy
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The treatment of α,β-unsaturated carbonyl compounds and 1,3-diketones with Raney Ni-Al alloy in aqueous media yielded as major reaction products the corresponding saturated alcohols and/or the corresponding hydrocarbons, in a complete transformation of the starting material.
- Katayama, Yumi,Mitoma, Yoshiharu,Simion, Alina Marieta,Simion, Cristian
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- Cobalt-Catalyzed Markovnikov Selective Sequential Hydrogenation/Hydrohydrazidation of Aliphatic Terminal Alkynes
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Here, we reported for the first time a mechanistically distinctive cobalt-catalyzed Markovnikov-type sequential semihydrogenation/hydrohydrazidation of aliphatic terminal alkynes in one pot. A cobalt hydride species was employed as two roles for both a unique metal-catalyzed Markovnikov-type insertion of the aliphatic terminal alkynes and then metal-catalyzed hydrogen atom transfer of alkenes. This operationally simple protocol exhibits excellent functional group tolerance and step economy. The hydrazone products could be easily transferred to various valuable amine derivatives.
- Chen, Jieping,Shen, Xuzhong,Lu, Zhan
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supporting information
p. 14455 - 14460
(2020/10/13)
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- Visible-Light-Induced Ni-Catalyzed Radical Borylation of Chloroarenes
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A highly selective and general photoinduced C-Cl borylation protocol that employs [Ni(IMes)2] (IMes = 1,3-dimesitylimidazoline-2-ylidene) for the radical borylation of chloroarenes is reported. This photoinduced system operates with visible light (400 nm) and achieves borylation of a wide range of chloroarenes with B2pin2 at room temperature in excellent yields and with high selectivity, thereby demonstrating its broad utility and functional group tolerance. Mechanistic investigations suggest that the borylation reactions proceed via a radical process. EPR studies demonstrate that [Ni(IMes)2] undergoes very fast chlorine atom abstraction from aryl chlorides to give [NiI(IMes)2Cl] and aryl radicals. Control experiments indicate that light promotes the reaction of [NiI(IMes)2Cl] with aryl chlorides generating additional aryl radicals and [NiII(IMes)2Cl2]. The aryl radicals react with an anionic sp2-sp3 diborane [B2pin2(OMe)]- formed from B2pin2 and KOMe to yield the corresponding borylation product and the [Bpin(OMe)]?- radical anion, which reduces [NiII(IMes)2Cl2] under irradiation to regenerate [NiI(IMes)2Cl] and [Ni(IMes)2] for the next catalytic cycle.
- Tian, Ya-Ming,Guo, Xiao-Ning,Krummenacher, Ivo,Wu, Zhu,Nitsch, J?rn,Braunschweig, Holger,Radius, Udo,Marder, Todd B.
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supporting information
p. 18231 - 18242
(2020/11/02)
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- Method for constructing carbon-hydrogen bond by catalyzing alcohol dehydroxylation with palladium/platinum
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The invention discloses a method for constructing a carbon-hydrogen (deuterium) bond. The method comprises the following step: in the presence of a palladium/platinum catalyst and aryl halide, an alcohol hydroxyl group of an alcohol and hydrogen (deuterium) gas is replaced by hydrogen (deuterium) to construct the carbon-hydrogen (deuterium) bond. According to the method, the palladium/platinum catalyst is used as a catalyst, the green hydrogen (deuterium) gas is used as a hydrogen (deuterium) source, efficient alcohol dehydroxylation is performed at room temperature to construct the carbon-hydrogen (deuterium) bond, and the method is particularly suitable for constructing the carbon-deuterium bond and can be widely applied to synthesis of deuterated drugs.
- -
-
Paragraph 0104-0110; 0112
(2019/12/25)
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- Iridium-Catalyzed Alkene-Selective Transfer Hydrogenation with 1,4-Dioxane as Hydrogen Donor
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The iridium-catalyzed transfer hydrogenation of alkenes using 1,4-dioxane as a hydrogen donor is described. The use of 1,2-bis(dicyclohexylphosphino)ethane (DCyPE), featuring bulky and highly electron-donating properties, led to high catalytic activity. A polystyrene-cross-linking bisphosphine PS-DPPBz produced a reusable heterogeneous catalyst. These homogeneous and heterogeneous protocols achieved chemoselective transfer hydrogenation of alkenes over other potentially reducible functional groups such as carbonyl, nitro, cyano, and imino groups in the same molecule.
- Zhang, Deliang,Iwai, Tomohiro,Sawamura, Masaya
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supporting information
p. 5867 - 5872
(2019/08/26)
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- Regiodivergent hydrosilylation, hydrogenation, [2π + 2π]-cycloaddition and C-H borylation using counterion activated earth-abundant metal catalysis
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The widespread adoption of earth-abundant metal catalysis lags behind that of the second- and third-row transition metals due to the often challenging practical requirements needed to generate the active low oxidation-state catalysts. Here we report the development of a single endogenous activation protocol across five reaction classes using both iron- and cobalt pre-catalysts. This simple catalytic manifold uses commercially available, bench-stable iron- or cobalt tetrafluoroborate salts to perform regiodivergent alkene and alkyne hydrosilylation, 1,3-diene hydrosilylation, hydrogenation, [2π + 2π]-cycloaddition and C-H borylation. The activation protocol proceeds by fluoride dissociation from the counterion, in situ formation of a hydridic activator and generation of a low oxidation-state catalyst.
- Agahi, Riaz,Challinor, Amy J.,Dunne, Joanne,Docherty, Jamie H.,Carter, Neil B.,Thomas, Stephen P.
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p. 5079 - 5084
(2019/05/24)
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- Aggregation-induced Substrate Specificity in Aerobic Reduction of Olefins with Ultrasound Gel Catalyst of Synthetic Flavin
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A riboflavin derivative bearing octadecanoyl functionalities 1 a gelatinizes a variety of organic solvents upon brief ultrasonication in an organic fluid. The rate of gelation with 1 a can be externally and precisely controlled by tuning the sonication time and type of solvent. The present ultrasound gel exhibits unprecedented substrate specificity for the catalytic aerobic reduction of olefins, which can be performed with hydrazine at ambient temperature and atmospheric pressure in air. The reaction rates of 1-dodecene (2), allylbenzene (3), and o-allylphenol (4) with the ultrasound gel 1 a catalyst is in the order of 2?3>4, the substrate specificity of which is in contrast to the almost non-specificity with the non-gelled catalyst 1 b bearing butanoyl functionalities, and entirely inverse specificity with a flavin-dendrimer association catalyst (234). Based on kinetic studies, the aggregation effects on the substrate specificity have been ascribed to the specific inclusion of aliphatic olefins into the enzyme-like artificial cavities of the gel catalysts.
- Kawamorita, Soichiro,Fujiki, Misa,Li, Zimeng,Kitagawa, Takahiro,Imada, Yasushi,Naota, Takeshi
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p. 878 - 884
(2019/01/14)
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- Water and Sodium Chloride: Essential Ingredients for Robust and Fast Pd-Catalysed Cross-Coupling Reactions between Organolithium Reagents and (Hetero)aryl Halides
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Direct palladium-catalysed cross-couplings between organolithium reagents and (hetero)aryl halides (Br, Cl) proceed fast, cleanly and selectively at room temperature in air, with water as the only reaction medium and in the presence of NaCl as a cheap additive. Under optimised reaction conditions, a water-accelerated catalysis is responsible for furnishing C(sp3)–C(sp2), C(sp2)–C(sp2), and C(sp)–C(sp2) cross-coupled products, in competition with protonolysis, within a reaction time of 20 s, in yields of up to 99 %, and in the absence of undesired dehalogenated/homocoupling side products even when challenging secondary organolithiums serve as the starting material. It is worth noting that the proposed protocol is scalable and the catalyst and water can easily and successfully be recycled up to 10 times, with an E-factor as low as 7.35.
- Dilauro, Giuseppe,Quivelli, Andrea Francesca,Vitale, Paola,Capriati, Vito,Perna, Filippo Maria
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supporting information
p. 1799 - 1802
(2019/01/25)
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- Visible-Light-Promoted Iron-Catalyzed C(sp2)–C(sp3) Kumada Cross-Coupling in Flow
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A continuous-flow, visible-light-promoted method has been developed to overcome the limitations of iron-catalyzed Kumada–Corriu cross-coupling reactions. A variety of strongly electron rich aryl chlorides, previously hardly reactive, could be efficiently coupled with aliphatic Grignard reagents at room temperature in high yields and within a few minutes’ residence time, considerably enhancing the applicability of this iron-catalyzed reaction. The robustness of this protocol was demonstrated on a multigram scale, thus providing the potential for future pharmaceutical application.
- Wei, Xiao-Jing,Abdiaj, Irini,Sambiagio, Carlo,Li, Chenfei,Zysman-Colman, Eli,Alcázar, Jesús,No?l, Timothy
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supporting information
p. 13030 - 13034
(2019/07/18)
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- Hydrodeoxygenation Using Magnetic Induction: High-Temperature Heterogeneous Catalysis in Solution
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Magnetic heating has recently been demonstrated as an efficient way to perform catalytic reactions after deposition of the heating agent and the catalyst on a support. Here we show that in solution, and under mild conditions of mean temperature and pressure, it is possible to use magnetic heating to carry out transformations that are otherwise performed heterogeneously at high pressure and/or high temperature. As a proof of concept, we chose the hydrodeoxygenation of acetophenone derivatives and of biomass-derived molecules, namely furfural and hydroxymethylfurfural. These reactions are difficult, require heterogeneous catalysts and high pressures, and, to the best of our knowledge, have no precedent in standard solution. Here, hydrodeoxygenations are fully selective under mild conditions (3 bar H2, moderate mean temperature of the solvent). The reason for this reactivity is the fast heating of the particles well above the boiling temperature of the solvent and the local creation of hot spots surrounded by a vapor layer, in which high temperature and pressure may be present. This technology may be practicable for many organic transformations.
- Asensio, Juan M.,Miguel, Ana B.,Fazzini, Pier-Francesco,van Leeuwen, Piet W. N. M.,Chaudret, Bruno
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supporting information
p. 11306 - 11310
(2019/07/12)
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- Free Radical Pathway Cleavage of C—O Bonds for the Synthesis of Alkylboron Compounds
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We report a silver-catalyzed borylation of alkyl tosylates, which provides a new method for the synthesis of alkylboron compounds with good functional group compatibility and excellent chemoselectivity. The present work added highly polarized alkyl tosylate C—O bonds to the fairly limited number of C—O bonds able to participate in free radical cleavage pathways. The mechanistic studies suggested that in situ-generated silver(0) catalytic species were the active catalytic species and played a key role in the radical pathway cleavage of C—O bonds.
- Lu, Xi,Zhang, Zhen-Qi,Yu, Lu,Zhang, Ben,Wang, Bing,Gong, Tian-Jun,Tian, Chang-Lin,Xiao, Bin,Fu, Yao
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supporting information
p. 11 - 18
(2018/12/13)
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- Cobalt-Catalyzed Alkylation of Drug-Like Molecules and Pharmaceuticals Using Heterocyclic Phosphonium Salts
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Alkylated pyridines are common in pharmaceuticals, and metal catalysis is frequently used to prepare this motif via Csp2-Csp3 coupling processes. We present a cobalt-catalyzed coupling reaction between pyridine phosphonium salts and alkylzinc reagents that can be applied to complex drug-like fragments and for late-stage functionalization of pharmaceuticals. The reaction generally proceeds at room temperature, and 4-position pyridine C-H bonds are the precursors in this strategy. Given the challenges in selectively installing (pseudo)halides in complex pyridines, this two-step process enables sets of molecules to be alkylated that would be challenging using traditional cross-coupling methods.
- Zhang, Xuan,McNally, Andrew
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p. 4862 - 4866
(2019/05/24)
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- A General One-Pot Methodology for the Preparation of Mono- and Bimetallic Nanoparticles Supported on Carbon Nanotubes: Application in the Semi-hydrogenation of Alkynes and Acetylene
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A facile and straightforward methodology for the preparation of monometallic (copper and palladium) and bimetallic nanocatalysts (NiCu and PdCu) stabilized by a N-heterocyclic carbene ligand is reported. Both colloidal and supported nanoparticles (NPs) on carbon nanotubes (CNTs) were prepared in a one-pot synthesis with outstanding control on their size, morphology and composition. These catalysts were evaluated in the selective hydrogenation of alkynes and alkynols. PdCu/CNTs revealed an efficient catalytic system providing high selectivity in the hydrogenation of terminal and internal alkynes. Moreover, this catalyst was tested in the semi-hydrogenation of acetylene in industrially relevant acetylene/ethylene-rich model gas feeds and showed excellent stability even after 40 h of reaction.
- Lomelí-Rosales, Diego A.,Delgado, Jorge A.,Díaz de los Bernardos, Miriam,Pérez-Rodríguez, Sara,Gual, Aitor,Claver, Carmen,Godard, Cyril
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supporting information
p. 8321 - 8331
(2019/06/04)
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- Homogeneous Palladium-Catalyzed Transfer Hydrogenolysis of Benzylic Alcohols Using Formic Acid as Reductant
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We report the first homogeneous palladium-based transfer hydrogenolysis of benzylic alcohols using an in situ formed palladium-phosphine complex and formic acid as reducing agent. The reaction requires a catalyst loading as low as only 1 mol % of palladium and just a slight excess of reductant to obtain the deoxygenated alkylarenes in good to excellent yields. Besides demonstrating the broad applicability for primary, secondary and tertiary benzylic alcohols, a reaction intermediate could be identified. Additionally, it could be shown that partial oxidation of the applied phosphine ligand was beneficial for the course of the reaction, presumably by stabilizing the active catalyst. Reaction profiles and catalyst poisoning experiments were used to characterize the catalyst, the results of which indicate a homogeneous metal complex as the active species.
- Ciszek, Benjamin,Fleischer, Ivana
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supporting information
p. 12259 - 12263
(2018/08/28)
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- Heterolysis of Dihydrogen by Nucleophilic Calcium Alkyls
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β-Diketiminato (BDI) calcium alkyl derivatives undergo hydrogenolysis with H2 to regenerate [(BDI)CaH]2, allowing the catalytic hydrogenation of a wide range of 1-alkenes and norbornene under very mild conditions (2 bar H2, 298 K). The reactions are deduced to take place with the retention of the dimeric structures of the calcium hydrido-alkyl and alkyl intermediates via a well-defined sequence of Ca?H/C=C insertion and Ca?C hydrogenation events. This latter deduction is strongly supported by DFT calculations (B3PW91) performed on the 1-hexene/H2 system, which also indicates that the hydrogenation transition states display features which discriminate them from a classical σ-bond metathesis mechanism. In particular, NBO analysis identifies a strong second order interaction between the filled α-methylene sp3 orbital of the n-hexyl chain and the σ* orbital of the H2 molecule, signifying that the H?H bond is broken by what is effectively the nucleophilic displacement of hydride by the organic substituent.
- Wilson, Andrew S. S.,Dinoi, Chiara,Hill, Michael S.,Mahon, Mary F.,Maron, Laurent
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supporting information
p. 15500 - 15504
(2018/11/01)
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- Bimetallic Nanoparticles in Supported Ionic Liquid Phases as Multifunctional Catalysts for the Selective Hydrodeoxygenation of Aromatic Substrates
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Bimetallic iron–ruthenium nanoparticles embedded in an acidic supported ionic liquid phase (FeRu@SILP+IL-SO3H) act as multifunctional catalysts for the selective hydrodeoxygenation of carbonyl groups in aromatic substrates. The catalyst material is assembled systematically from molecular components to combine the acid and metal sites that allow hydrogenolysis of the C=O bonds without hydrogenation of the aromatic ring. The resulting materials possess high activity and stability for the catalytic hydrodeoxygenation of C=O groups to CH2 units in a variety of substituted aromatic ketones and, hence, provide an effective and benign alternative to traditional Clemmensen and Wolff–Kishner reductions, which require stoichiometric reagents. The molecular design of the FeRu@SILP+IL-SO3H materials opens a general approach to multifunctional catalytic systems (MM′@SILP+IL-func).
- Offner-Marko, Lisa,Bordet, Alexis,Moos, Gilles,Tricard, Simon,Rengshausen, Simon,Chaudret, Bruno,Luska, Kylie L.,Leitner, Walter
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supporting information
p. 12721 - 12726
(2018/09/12)
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- Room Temperature Chemoselective Deoxygenation of Aromatic Ketones and Aldehydes Promoted by a Tandem Pd/TiO2 + FeCl3 Catalyst
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A rapid and practical protocol for the chemoselective deoxygenation of various aromatic ketones and aldehydes was described, which used a tandem catalyst composed of heterogeneous Pd/TiO2 + homogeneous FeCl3 with the green hydrogen source, polymethylhydrosiloxane (PMHS). The developed catalytic system was robust and scalable, as exemplified by the deoxygenation of acetophenone, which was performed on a gram scale in an atmospheric environment utilizing only 0.4 mol % Pd/TiO2 + 10 mol % FeCl3 catalyst to give the corresponding ethylbenzene in 96% yield within 10 min at room temperature. Furthermore, the Pd/TiO2 catalyst was shown to be recyclable up to three times without an observable decrease in efficiency and it exhibited low metal leaching under the reaction conditions. Insights toward the reaction mechanism of Pd-catalyzed reductive deoxygenation for aromatic ketones and aldehydes were investigated through operando IR, NMR, and GC-MS techniques.
- Dong, Zhenhua,Yuan, Jinwei,Xiao, Yongmei,Mao, Pu,Wang, Wentao
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p. 11067 - 11073
(2018/09/12)
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- Reactivity of the diphosphinodithio ligated nickel(0) complex toward alkyl halides and resultant nickel(i) and nickel(ii)-alkyl complexes
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Diphosphinodithio ligated complexes of nickel(0), nickel(i) and nickel(ii)-alkyl with a reactivity relevant to the C-C bond formation were described. Stoichiometric reactions of the nickel(0) complex, [(P2S2)Ni] ([1]0, P2S2 = (Ph2PC6H4CH2S)2(C2H4)), with alkyl halides (RX) such as C6H5CH2Br, C2H3CH2Br, C2H5I and (CH3)2CHI were investigated, from which the products were found to be highly dependent on the nature of RX used. Oxidative addition of C2H3CH2Br to [1]0 provides the stable Ni(ii)-alkyl complexes [1-allyl]+. The reaction of [1]0 with C6H5CH2Br proceeds through a radical pathway resulting in the formation of the nickel(i) complex [1]+ and an organic homo-coupled product 1,2-diphenylethane. Oxidative addition of C2H5I or (CH3)2CHI to [1]0 can be achieved but it competes with the halogen atom abstraction reaction as found for C6H5CH2Br. [1]0 was shown to be an active catalyst for the coupling reactions of primary halides and alkyl Grignard reagents.
- Zhang, Ailing,Wang, Congxiao,Lai, Xiaoyu,Zhai, Xiaofang,Pang, Maofu,Tung, Chen-Ho,Wang, Wenguang
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supporting information
p. 15757 - 15764
(2018/11/23)
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- Iron-Catalyzed Remote Arylation of Aliphatic C-H Bond via 1,5-Hydrogen Shift
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Catalytic amounts of an iron(III) salt and a N-heterocyclic carbene ligand catalyze the arylation of 2-iodoalkylarenes with diphenylzinc selectively at the C-H bond of the alkyl side chain. Several lines of evidence suggest that the iron catalyst reacts with the aryl iodide moiety of the substrate to generate an aryliron intermediate that behaves in a radical manner and cleaves the aliphatic C-H bond through 1,5-hydrogen transfer; the resulting alkyliron intermediate undergoes reductive elimination to give the arylated product.
- Zhou, Bingwei,Sato, Hiroki,Ilies, Laurean,Nakamura, Eiichi
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- Carbonylative Coupling of Alkyl Zinc Reagents with Benzyl Bromides Catalyzed by a Nickel/NN2 Pincer Ligand Complex
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An efficient catalytic protocol for the three-component assembly of benzyl bromides, carbon monoxide, and alkyl zinc reagents to give benzyl alkyl ketones is described, and represents the first nickel-catalyzed carbonylative coupling of two sp3-carbon fragments. The method, which relies on the application of nickel complexed with an NN2-type pincer ligand and a controlled release of CO gas from a solid precursor, works well with a range of benzylic bromides. Mechanistic studies suggest the intermediacy of carbon-centered radicals.
- Andersen, Thomas L.,Donslund, Aske S.,Neumann, Karoline T.,Skrydstrup, Troels
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supporting information
p. 800 - 804
(2017/12/26)
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- Reductive Denitration of Nitroarenes
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The Pd-catalyzed reductive denitration of nitroarenes has been achieved via a direct cleavage of the C-NO2 bonds. The catalytic conditions reported exhibit a broad substrate scope and good functional-group compatibility. Notably, the use of inexpensive propan-2-ol as a mild reductant suppresses the competitive formation of anilines, which are normally formed by other conventional reductions. Mechanistic studies have revealed that alcohols serve as efficient hydride donors in this reaction, possibly through β-hydride elimination from palladium alkoxides.
- Kashihara, Myuto,Yadav, M. Ramu,Nakao, Yoshiaki
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supporting information
p. 1655 - 1658
(2018/03/23)
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- Synthesis of quinolinyl-based pincer copper(ii) complexes: an efficient catalyst system for Kumada coupling of alkyl chlorides and bromides with alkyl Grignard reagents
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Quinolinamide-based pincer copper(ii) complexes, κN,κN,κN-{C9H6N-(μ-N)-C(O)CH2NEt2}CuX [(QNNNEt2)CuX (X = Cl, 2; X = Br, 3; X = OAc, 4)], were synthesized by the reaction of ligand (QNNNEt2)-H (1) with CuX2 (X = Cl, Br or OAc) in the presence of Et3N. The reaction of (QNNNEt2)-H with CuX (X = Cl, Br or OAc) also afforded the Cu(ii) complexes 2, 3 and 4, respectively, instead of the expected Cu(i) pincer complexes. The formation of Cu(ii) complexes from Cu(i) precursors most likely occurred via the disproportionation reaction of Cu(i) into Cu(0) and Cu(ii). A cationic complex [(QNNNEt2)Cu(CH3CN)]OTf (5) was synthesized by the treatment of neutral complex 2 with AgOTf. On the other hand, the reaction of (QNNNEt2)-H (1) with [Cu(MeCN)4]ClO4 produced cationic Cu(i) complex, [(QNN(H)NEt2)Cu(CH3CN)]ClO4 (6), in good yield. All complexes 2-5 were characterized by elemental analysis and HRMS measurements. Furthermore, the molecular structures of 2, 3 and 4 were elucidated by X-ray crystallography. Complex 4 crystallizes in a dimeric and catemeric pattern. The cationic complex 5 was found to be an efficient catalyst for the Kumada coupling reaction of diverse nonactivated alkyl chlorides and bromides with alkyl magnesium chloride under mild reaction conditions.
- Pandiri, Hanumanprasad,Gonnade, Rajesh G.,Punji, Benudhar
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supporting information
p. 16747 - 16754
(2018/12/05)
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- B(C6F5)3-Catalyzed Chemoselective Defunctionalization of Ether-Containing Primary Alkyl Tosylates with Hydrosilanes
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Catalytic C(sp3)?O bond cleavage promoted by B(C6F5)3 /Et3SiH proceeds preferentially with primary tosylates in the presence of primary and secondary silyl ethers and aryl ethers. This reactivity difference enables the chemoselective defunctionalization of several 1,n-diols, and the efficiency of the new procedure is highlighted by the selective deoxygenation of the hydroxymethyl group of an orthogonally protected carbohydrate. Tosylates with an adjacent phenyl group are cleaved with anchimeric assistance.
- Chatterjee, Indranil,Porwal, Digvijay,Oestreich, Martin
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supporting information
p. 3389 - 3391
(2017/03/17)
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- Activation and discovery of earth-abundant metal catalysts using sodium tert-butoxide
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First-row, earth-abundant metals offer an inexpensive and sustainable alternative to precious-metal catalysts. As such, iron and cobalt catalysts have garnered interest as replacements for alkene and alkyne hydrofunctionalization reactions. However, these have required the use of air- and moisture-sensitive catalysts and reagents, limiting both adoption by the non-expert as well as applicability, particularly in industrial settings. Here, we report a simple method for the use of earth-abundant metal catalysts by general activation with sodium tert-butoxide. Using only robust air- and moisture-stable reagents and pre-catalysts, both known and, significantly, novel catalytic activities have been successfully achieved, covering hydrosilylation, hydroboration, hydrovinylation, hydrogenation and [2π+2π] alkene cycloaddition. This activation method allows for the easy use of earth-abundant metals, including iron, cobalt, nickel and manganese, and represents a generic platform for the discovery and application of non-precious metal catalysis.
- Docherty, Jamie H.,Peng, Jingying,Dominey, Andrew P.,Thomas, Stephen P.
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p. 595 - 600
(2017/05/31)
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- Facile synthesis of NHC-stabilized Ni nanoparticles and their catalytic application in the: Z -selective hydrogenation of alkynes
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Well defined Ni nanoparticles (NiNPs) stabilized with N-heterocyclic carbenes (NHCs) have been synthesized through a new methodology involving the decarboxylation of a zwitterionic CO2 adduct. Their catalytic performance was tested in the partial hydrogenation of alkynes into (Z)-alkenes under very mild reaction conditions (50 °C and 5 bar H2 pressure), providing excellent activities and selectivities.
- De Los Bernardos, Miriam Díaz,Pérez-Rodríguez, Sara,Gual, Aitor,Claver, Carmen,Godard, Cyril
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supporting information
p. 7894 - 7897
(2017/07/17)
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