- Olefin isomerization by iridium pincer catalysts. experimental evidence for an η3-allyl pathway and an unconventional mechanism predicted by DFT calculations
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The isomerization of olefins by complexes of the pincer-ligated iridium species (tBuPCP)Ir (tBuPCP = κ3-C 6H3-2,6-(CH2PtBu2) 2) and (tBuPOCOP)Ir (tBuPOCOP = κ3-C6H3-2,6-(OPtBu 2)2) has been investigated by computational and experimental methods. The corresponding dihydrides, (pincer)IrH2, are known to hydrogenate olefins via initial Ir-H addition across the double bond. Such an addition is also the initial step in the mechanism most widely proposed for olefin isomerization (the "hydride addition pathway"); however, the results of kinetics experiments and DFT calculations (using both M06 and PBE functionals) indicate that this is not the operative pathway for isomerization in this case. Instead, (pincer)Ir(η2-olefin) species undergo isomerization via the formation of (pincer)Ir(η3-allyl)(H) intermediates; one example of such a species, (tBuPOCOP) Ir(η3-propenyl)(H), was independently generated, spectroscopically characterized, and observed to convert to ( tBuPOCOP)Ir(η2-propene). Surprisingly, the DFT calculations indicate that the conversion of the η2-olefin complex to the η3-allyl hydride takes place via initial dissociation of the Ir-olefin π-bond to give a σ-complex of the allylic C-H bond; this intermediate then undergoes C-H bond oxidative cleavage to give an iridium η1-allyl hydride which "closes" to give the η3-allyl hydride. Subsequently, the η3-allyl group "opens" in the opposite sense to give a new η1-allyl (thus completing what is formally a 1,3 shift of Ir), which undergoes C-H elimination and π-coordination to give a coordinated olefin that has undergone double-bond migration.
- Biswas, Soumik,Huang, Zheng,Choliy, Yuriy,Wang, David Y.,Brookhart, Maurice,Krogh-Jespersen, Karsten,Goldman, Alan S.
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- Rh(i) complexes supported on a biopolymer as recyclable and selective hydroformylation catalysts
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Chitosan-supported Rh complexes were prepared in a stable form to form new catalysts and have been characterized using elemental analysis, UV-vis, FT-IR, ICP-MS, PXRD, solid state 31P and 13C NMR spectroscopy and TEM. Mononuclear Rh(i) complexes (as models for the heterogenized catalysts) were also prepared via the Schiff-base condensation reaction and the crystal structure of the cyclohexyl iminophosphine Rh(i) complex was elucidated. The chitosan-supported Rh complexes and mononuclear analogues are active catalysts in the hydroformylation of 1-octene with optimal reaction conditions realized at 75 °C and 30 bar syngas pressure. Under these conditions, 1-octene conversion to the desired linear aldehydes was observed and the best selectivity in this regard was shown by the supported iminophosphine-based rhodium catalyst. Overall, the supported catalysts showed similar chemo- and regioselectivities in comparison to their mononuclear counterparts but where more stable, being reused up to four times without loss of activity and selectivity.
- Makhubela, Banothile C. E.,Jardine, Anwar,Smith, Gregory S.
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- Activation of tetrabutylammonium hydrogen difluoride with pyridine: A mild and efficient procedure for nucleophilic fluorination
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The nucleophilic fluorination of alkyl iodides, bromides and tosylates and of α-bromo- or α-chloroketones is smoothly effected by tetrabutylammonium hydrogen difluoride in the presence of pyridine, in dioxane or THF, with good or satisfying substitution-to-elimination ratio.
- Moughamir, Khadija,Atmani, Aziz,Mestdagh, Helene,Rolando, Christian,Francesch, Charlette
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- Impact of Alkali and Alkali-Earth Cations on Ni-Catalyzed Dimerization of Butene
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The presence of alkali (Na+ or Li+) or alkali-earth (Ca2+ or Mg2+) cations adjusting the acid-base properties on amorphous silica-alumina influences markedly the catalytic properties of supported Ni for 1-butene dimerization. The low concentration of Br?nsted acid sites on these catalysts reduces the double bond isomerization of butene and inhibits the formation of dimethylhexene as primary product. While the alkali and alkali-earth cations act as weak Lewis acid sites, only Ni2+ sites are catalytically active for dimerization of 1-butene. n-Octene and methylheptene are formed selectively as primary products; dimethylhexene is a secondary product. The open environment of the Ni2+ sites does not induce different reaction pathways compared to Ni2+ in the pores of zeolites.
- Ehrmaier, Andreas,L?bbert, Laura,Sanchez-Sanchez, Maricruz,Bermejo-Deval, Ricardo,Lercher, Johannes
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- Indenyl- and fluorenyl-functionalized n-heterocyclic carbene complexes ofrhodium and iridium synthetic, structural and catalytic studies
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Rhodium and iridium complexes with N-heterocyclic carb-enes (NHC) functionalized with neutral or anionic indenyland fluorenyl groups are reported. In the complexes the li-gands adopt monodentate, bidentate or bridging bondingmodes with the NHC group ?-bonded and the fluorenyl orindenyl functionalities either dangling or coordinated to themetal with various hapticities (?1, ?3 and ?5). Metallation ofthe C-H bond of the alkylene linker in the ligand has also been observed. Catalytic studies on the bidentate RhIcom-plex 6 show that it is weakly active for the hydroformylationof 1-octene with poor linear selectivity, but it shows slightlylower activity than the standardMonsanto system for the car-bonylation of methanol. Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2009.
- Downing, Stephen P.,Pogorzelec, Peter J.,Danopoulos, Andreas A.,Cole-Hamilton, David J.
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- Synthesis of the deuterated sex pheromone components of the grape borer, xylotrechus pyrrhoderus
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Adult males of the grape borer, Xylotrechus pyrrho- derus, secrete (S)-2-hydroxy-3-octanone [(S)-1] and (2S,3S)-2,3-octanediol [(2S,3S)-2] from their nota of prothoraces as sex pheromone components. Their structural similarity suggests that one of them is the biosynthetic precursor of the other component. In order to confirm the biochemical conversion, deuterated derivatives of both components were synthesized by starting from a Wittig reaction between hexanal and an ylide derived from D5-iodoethane and ending with enantiomeric resolution by chiral HPLC. The molecular ions of 1 and 2 could scarcely be detected by using a GC- MS analysis, and the labeled compounds showed similar mass spectra to the unlabeled pheromone components. However, several fragment ions, including four deuterium atoms, were observed in the mass spectra of their acetate derivatives, indicating that the conversion could be confirmed by examining a compound with the diagnostic ions after acetylation of the volatiles collected from insects treated with the labeled precursors.
- Kiyota, Ryutaro,Yamakawa, Rei,Iwabuchi, Kikuo,Hoshino, Keita,Ando, Tetsu
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- POLYMER-SUPPORTED 2,2'-DIPYRIDYLMETHANE: SYNTHESIS AND FORMATION OF TRANSITION METAL COMPLEXES
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The chelating ligand 2,2'-dipyridylmethane can be anchored to styrene-divinylbenzene polymers by reaction of the anion of 2,2'-dipyridylmethanol with chloromethylated or chloroacetylated resins under mild conditions.A number of transition metal complexes of the polymeric ligand have been prepared.Alkenes and alkynes are readily hydrogenated with the Pd(OAc)2 complex of the polymeric ligand as catalyst.
- Elman, Bjoern,Moberg, Christina
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- Hydroformylation in fluorous solvents
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Triaryl-phosphines and -phosphites bearing fluorous ponytails give high rates, good linear selectivity and good retention of catalyst in the fluorous phase during hydroformylation of alkenes in fluorous solvents.
- Foster, Douglas F.,Adams, Dave J.,Gudmunsen, David,Stuart, Alison M.,Hope, Eric G.,Hamilton, David J.
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- Studies on organolanthanide complexes. XLI. Cata;ytic isomerization of olefins by organolanthanide complex/sodium hydride systems
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Isomerization of several 1-alkenes catalyzed by organolanthanide complex/sodium hydride systems in THF at 45 deg C, affords cis- and trans-2-alkenes in excellent yields.Effects of solvent and ?-ligand of complex on this isomerization are also examined.The catalytic isomerization may occur via organolanthanide hydride intermediate.
- Qian, Changtao,Zhu, Dunming,Li, Dongmei
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- Comparative Dimerization of 1-Butene mith a Variety of Metal Catalysts, and the Investigation of a New Catalyst for C-H Bond Activation
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Catalytic dimerization of 1-butene by a variety of catalysts is carried out, and the products are analyzed by gas chromatography and mass spectrometry. Catalysts based on cobalt and iron can produce highly linear dimers, with the cobalt-based dimers exceeding 97% linearity. Catalysts based on vanadium and aluminum prefer to make branched dimers, which are most often methyl-heptenes in the case of vanadium and almost exclusively 2-ethyl-1-butene in the case of aluminum. The vanadium catalyst also produces substantial amounts of dienes and alkanes, suggesting a competing hydrogenation/dehydrogenation pathway that appears to involve vinyl C-H bond activation. Nickel catalysts are generally less selective than those based on iron or cobalt for making linear dimers, but they can make dimers with 60% linearity. The major by-products for the nickel systems are trisubstituted internal olefins. An important side reaction that must be considered for dimerization reactions is 1-butene isomerization to 2-butene, which makes recycling the butene difficult for a linear dimerization process. Aluminum, iron, and vanadium systems promote very little isomerization, but nickel and cobalt systems tend to isomerize the undimerized substrate heavily.
- Small, Brooke L.,Schmidt, Roland
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- A novel and efficient method for double bond isomerization
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Isomerization of α-alkenes is carried out in the presence of a catalytic amount of palladium (II) chloride and triethylsilane at room temperature. This novel and efficient method affords high yields in the absence of solvent for double bond isomerization of alkenes.
- Mirza-Aghayan, Maryam,Boukherroub, Rabah,Bolourtchian, Mohammad,Hoseini, Maryam,Tabar-Hydar, Kourosh
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- Retaining catalyst performance at high temperature: The use of a tetraphosphine ligand in the highly regioselective hydroformylation of terminal olefins
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A new tetraphosphine ligand has been developed and applied in the highly regioselective hydroformylation of terminal olefins. The ligand retains high performance at high temperature when compared with its bisphosphine analogue.
- Yan, Yongjun,Zhang, Xiaowei,Zhang, Xumu
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- Mesoporous silico-aluminophosphates derived from microporous precursors as promising catalyst for hydroisomerization
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A series of mesoporous silicoaluminophosphates (MESO-SAPOs) with different silica contents were synthesized using the microporous precursors of SAPO-37 (MESO-SAPO-37). Various analytical and spectroscopic techniques revealed the presence of mesoporous and microporous properties of the materials. The resulting materials were applied to vapor-phase hydroisomerization of 1-octene to afford the corresponding branched alkenes in good yields under ambient conditions. The catalytic activity of MESO-SAPO-37 was compared to those of other mesoporous analogs obtained from SAPO-34 and SAPO-5 precursors. Among all the synthesized materials, MESO-SAPO-37 showed the best catalytic activity owing to the presence of faujasite units.
- Yadav, Rekha,Singh, Arvind Kumar,Sakthivel, Ayyamperumal
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- Platinum Catalysis Revisited-Unraveling Principles of Catalytic Olefin Hydrosilylation
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Hydrosilylation of C-C multiple bonds is one of the most important applications of homogeneous catalysis in industry. The reaction is characterized by its atom-efficiency, broad substrate scope, and widespread application. To date, industry still relies on highly active platinum-based systems that were developed over half a century ago. Despite the rapid evolution of vast synthetic applications, the development of a fundamental understanding of the catalytic reaction pathway has been difficult and slow, particularly for the industrially highly relevant Karstedt's catalyst. A detailed mechanistic study unraveling several new aspects of platinum-catalyzed hydrosilylation using Karstedt's catalyst as platinum source is presented in this work. A combination of 2H-labeling experiments, 195Pt NMR studies, and an in-depth kinetic study provides the basis for a further development of the well-established Chalk-Harrod mechanism. It is concluded that the coordination strength of the olefin exerts a decisive effect on the kinetics of the reaction. In addition, it is demonstrated how distinct structural features of the active catalyst species can be derived from kinetic data. A primary kinetic isotope effect as well as a characteristic product distribution in deuterium-labeling experiments lead to the conclusion that the rate-limiting step of platinum-catalyzed hydrosilylation is in fact the insertion of the olefin into the Pt-H bond rather than reductive elimination of the product in the olefin/silane combinations studied.
- Meister, Teresa K.,Riener, Korbinian,Gigler, Peter,Stohrer, Jürgen,Herrmann, Wolfgang A.,Kühn, Fritz E.
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- Et3n .2Hf, a new convenient reagent for nucleophilic fluorine displacement reactions
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Syntheses of fluoro compounds by nucleophilic substitution of bromides or methane sulfonates using Et3N .2HF as the reagent are reported. The formation of undesired elimination side products is limited. The synthesis of this new fluorinating reagent is also reported.
- Giudicelli,Pica,Veyron
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- Aqueous-biphasic hydroformylation of alkenes promoted by "weak" surfactants
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The aqueous-biphasic hydroformylation of higher alkenes catalyzed by Rh/TPPTS has been carried out in the presence of imidazolium, pyridinium and triethylammonium salts. High reaction rates are achieved with imidazolium and triethylammonium salts provided that their alkyl "tail" is ≥C 8. Fast and complete phase separation, and good retention of the metal in the aqueous phase could be achieved with an octyl "tail". Imidazolium salts were found to give the highest rate enhancement. The nature of the anion showed a moderate influence on the reaction. Evidence suggests that the additive can act as weak surfactant allowing emulsions to be formed and broken by simply switching the stirring on and off.
- Desset, Simon L.,Reader, Simon W.,Cole-Hamilton, David J.
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- An insight into copper catalyzed allylation of alkyl zinc halides. Comparison of reactivity profiles for catalytic and stoichiometric alkylzinc-copper reagents
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The γ-selective allylation of catalytic and stoichiometric alkylzinc-cuprates have been kinetically studied. The reactivity profiles generated by allylation reactions of n-butylzinc chloride catalyzed by CuX compounds (X = I, Br, Cl, CN, SCN) and also cat
- Erdik, Ender,Ko?o?lu, Melike
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- Ring opening metathesis polymerization-derived block copolymers bearing chelating ligands: Synthesis, metal immobilization and use in hydroformylation under micellar conditions
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Norborn-5-ene-(N,N-dipyrid-2-yl)carbamide (M1) was copolymerized with exo,exo-[2-(3-ethoxycarbonyl-7-oxabicyclo[2.2.1]hept-5-en-2-carbonyloxy)ethyl] trimethylammonium iodide (M2) using the Schrock catalyst Mo(N-2,6-Me2-C6H3) (CHCMe2Ph)(OCMe(CF3)2)2 [Mo] to yield poly(M1-b-M2). In water, poly(M1-b-M2) forms micelles with a critical micelle-forming concentration (cmc) of 2.8 × 10-6 mol L-1; Reaction of poly(M1-b-M2) with [Rh(COD)Cl]2 (COD = cycloocta-1,5-diene) yields the Rh(I)-loaded block copolymer poly(M1-b-M2)-Rh containing 18 mg of Rh(I)/g of block copolymer with a cmc of 2.2 × 10 -6 mol L-1. The Rh-loaded polymer was used for the hydroformylation of 1-octene under micellar conditions. The data obtained were compared to those obtained with a monomeric analogue, i.e. CH3CON(Py)2RhCl(COD) (C1, Py = 2-pyridyl). Using the polymer-supported catalyst under micellar conditions, a significant increase in selectivity, i.e. an increase in the n:iso ratio was accomplished, which could be further enhanced by the addition of excess ligand, e.g., triphenylphosphite. Special features of the micellar catalytic set up are discussed.
- Pawar, Gajanan M.,Buchmeiser, Michael R.,Weckesser, Jochen,Blechert, Siegfried
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- Mild olefin formationviabio-inspired vitamin B12photocatalysis
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Dehydrohalogenation, or elimination of hydrogen-halide equivalents, remains one of the simplest methods for the installation of the biologically-important olefin functionality. However, this transformation often requires harsh, strongly-basic conditions, rare noble metals, or both, limiting its applicability in the synthesis of complex molecules. Nature has pursued a complementary approach in the novel vitamin B12-dependent photoreceptor CarH, where photolysis of a cobalt-carbon bond leads to selective olefin formation under mild, physiologically-relevant conditions. Herein we report a light-driven B12-based catalytic system that leverages this reactivity to convert alkyl electrophiles to olefins under incredibly mild conditions using only earth abundant elements. Further, this process exhibits a high level of regioselectivity, producing terminal olefins in moderate to excellent yield and exceptional selectivity. Finally, we are able to access a hitherto-unknown transformation, remote elimination, using two cobalt catalysts in tandem to produce subterminal olefins with excellent regioselectivity. Together, we show vitamin B12to be a powerful platform for developing mild olefin-forming reactions.
- Bam, Radha,Pollatos, Alexandros S.,Moser, Austin J.,West, Julian G.
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p. 1736 - 1744
(2021/02/22)
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- Reactions of Sodium Diisopropylamide: Liquid-Phase and Solid-Liquid Phase-Transfer Catalysis by N, N, N′, N″, N″-Pentamethyldiethylenetriamine
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Sodium diisopropylamide (NaDA) in N,N-dimethylethylamine (DMEA) and DMEA-hydrocarbon mixtures with added N,N,N′,N″,N″-pentamethyldiethylenetriamine (PMDTA) reacts with alkyl halides, epoxides, hydrazones, arenes, alkenes, and allyl ethers. Comparisons of PMDTA with N,N,N′,N′-tetramethylethylenediamine (TMEDA) accompanied by detailed rate and computational studies reveal the importance of the trifunctionality and κ2-κ3 hemilability. Rate studies show exclusively monomer-based reactions of 2-bromooctane, cyclooctene oxide, and dimethylresorcinol. Catalysis with 10 mol % PMDTA shows up to >30-fold accelerations (kcat > 300) with no evidence of inhibition over 10 turnovers. Solid-liquid phase-transfer catalysis (SLPTC) is explored as a means to optimize the catalysis as well as explore the merits of heterogeneous reaction conditions.
- Algera, Russell F.,Collum, David B.,Ma, Yun,Woltornist, Ryan A.
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supporting information
p. 13370 - 13381
(2021/09/03)
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- The effect of the position of cross-linkers on the structure and microenvironment of PPh3moiety in porous organic polymers
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Three trivinyl functionalization triphenylphosphine (3vPPh3)-based porous organic ligands (3vPPh3-POLs) with cross-linkers in different positions were obtained through solvothermal polymerization. By simply changing the position of the cross-linkers (vinyl groups) attached to the PPh3monomer, the resulting porous organic polymer (POP) materials acquired diverse hierarchical porous structures, and the microenvironment of POPs was sequently regulated. Among the three 3vPPh3-POLs, the BET surface areas ranged from 168 to 1583 m2g?1, while the proportion of micropores changed from 0.0% to 52.0%. Benefiting from the unique structure, Rh ions could be coordinated and dispersed as a single site inm-3vPPh3-POL to form HRh(CO)2(PPh3-POL)2species, which endowed the Rh/m-3vPPh3-POL catalyst with an activity similar to that in the homogeneous system, anl/bratio (the ratio of the linear aldehyde to the branched aldehyde) approximately as high as 10, and stability for a duration of more than 500 h in the hydroformylation of 1-octene.
- Ji, Guangjun,Li, Cunyao,Xiao, Dong,Wang, Guoqing,Sun, Zhao,Jiang, Miao,Hou, Guangjin,Yan, Li,Ding, Yunjie
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p. 9165 - 9174
(2021/04/16)
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- Photo-Initiated Cobalt-Catalyzed Radical Olefin Hydrogenation
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Outer-sphere radical hydrogenation of olefins proceeds via stepwise hydrogen atom transfer (HAT) from transition metal hydride species to the substrate. Typical catalysts exhibit M?H bonds that are either too weak to efficiently activate H2 or too strong to reduce unactivated olefins. This contribution evaluates an alternative approach, that starts from a square-planar cobalt(II) hydride complex. Photoactivation results in Co?H bond homolysis. The three-coordinate cobalt(I) photoproduct binds H2 to give a dihydrogen complex, which is a strong hydrogen atom donor, enabling the stepwise hydrogenation of both styrenes and unactivated aliphatic olefins with H2 via HAT.
- Sang, Sier,Unruh, Tobias,Demeshko, Serhiy,Domenianni, Luis I.,van Leest, Nicolaas P.,Marquetand, Philipp,Schneck, Felix,Würtele, Christian,de Zwart, Felix J.,de Bruin, Bas,González, Leticia,V?hringer, Peter,Schneider, Sven
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p. 16978 - 16989
(2021/08/09)
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- Amphiphilic polymeric nanoreactors containing Rh(i)-NHC complexes for the aqueous biphasic hydrogenation of alkenes
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A rhodium(i) complex bearing a monodentate N-heterocyclic carbene ligand has been confined into the core of amphiphilic polymeric core-crosslinked micelles (CCMs). The Rh complex was covalently bound to the polymeric chains by incorporation of a polymerizable unit on the NHC ligand. Nanoreactor Rh-NHCmes@CCM5bhas been evaluated as a catalyst for the aqueous biphasic hydrogenation of styrene and other alkenes. It has shown a high activity with styrene at a low catalytic loading (10?000/1 substrate/Rh ratio), greater than that of an analogous molecular Rh(i) complex, and its evolution to Rh0is slower. This is attributed to several factors, among which the confinement effect and the favourable polyoxygenated environment of the nanoreactor core. Finally, the CCMs could be recycled up to four times with almost no loss of activity over 3 h cycles and the loss of rhodium per cycle was on average lower than 0.6 ppm.
- Allandrieu, Audrey,Coppel, Yannick,Daran, Jean-Claude,Gayet, Florence,Hromov, Roman,Labande, Agnès,Manoury, Eric,Poli, Rinaldo,Ruzhylo, Illia,Sabatier, Cassandra,Sambou, Sasaline Salomon,Wang, Hui
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p. 6811 - 6824
(2021/10/25)
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- ALDEHYDE GENERATION VIA ALKENE HYDROFORMYLATION
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Aldehyde generation includes providing a first input stream, a second input, and an alkene substrate to a reactor system. The first input stream includes a catalyst, a ligand, and an organic solvent. The second input stream includes a mixture of carbon monoxide (CO) and hydrogen gas (H2). The alkene substrate is in either gaseous form or liquid form, the liquid form of the alkene substrate being provided with the first input stream, the gaseous form of the alkene substrate being provided with the second input stream. The reactor system includes a first reactor and a second reactor, where the second reactor is gas permeable and positioned within the first reactor.
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Paragraph 0035; 0079-0081
(2021/09/26)
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- METHOD FOR PRODUCING HIGHER LINEAR FATTY ACIDS OR ESTERS
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The present invention relates to a method of producing linear fatty acids comprising 7 to 28 carbon atoms or esters thereof using a combined biotechnological and chemical method. In particular, the present invention relates to a method of producing dodecanoic acid (i.e. lauric acid), via higher alkanones, preferably 6-undecanone.
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Page/Page column 36-37
(2021/11/26)
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- Photocatalytic-controlled olefin isomerization over WO3–x using low-energy photons up to 625 nm
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WO3–x (W-1) was used to achieve controllable photoisomerization of linear olefins without substituents under 625 nm light irradiation. Thermodynamic and kinetic isomers were obtained by regulating the carbon chain length of the olefins. Terminal olefins were converted into isomerized products, and the internal olefin mixtures present in petroleum derivatives were transformed into valuable pure olefin products. Oxygen vacancies (OVs) in W-1 altered the electronic structure of W-1 to improve its light-harvesting ability, which accounted for the high activity of olefin isomerization under light irradiation up to 625 nm. Additionally, OVs on the W-1 surface generated unsaturated W5+ sites that coordinated with olefins for the efficient adsorption and activation of olefins. Mechanistic studies reveal that the in situ formation of surface π-complexes and π-allylic W intermediates originating from the coordination of coordinated unsaturated W5+ sites and olefins ensure high photocatalytic activity and selectivity of W-1 for the photocatalytic isomerization of olefins via a radical mechanism.
- Sun, Xichen,Waclawik, Eric R.,Wang, Yunwei,Zhang, Jin,Zheng, Zhanfeng,Zhu, Pengqi
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p. 1641 - 1647
(2021/06/28)
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- Continuous flow hydrogenation with Pd complexes of pyridine-benzotriazole ligands
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The use of continuous flow systems in chemical synthesis provides great advantages in terms of sustainability, efficiency, and safety. The ability to control reaction parameters such as temperature, pressure, and catalyst exposure in flow system enables rapid optimization of reaction conditions. In the present study, palladium complexes of 1-(piridin-2-il)-1H-benzo[d][1,2,3]triazol, N-((1H-benzo[d][1,2,3]triazol-1-il)metil)piridin-2-amin, and (1H-benzo[d][1,2,3]triazol-1-yl)(pyridin-2-yl)methanone ligands were synthesized and characterized. The catalytic activities of complexes are investigated in the hydrogenation of various alkenes such as styrene, cyclohexene, and 1-octene under continuous flow conditions. The complexes showed very high activity at 10-bar H2 pressure and 50°C for short periods of 5–10?min. The catalysts reused for 10 cycles with no significant loss of catalytic activity.
- Y?lmaz, Filiz,Hür, Deniz
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- Iodine-catalyzed alcohol disproportionation method
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The invention relates to the technical field of catalysis, in particular to an iodine-catalyzed alcohol disproportionation method which comprises the following steps: sequentially adding alcohol, iodine and a solvent into a high-temperature and high-pressure reaction kettle, introducing a certain amount of nitrogen, conducting reacting for a certain time, collecting an organic phase after the reaction is ended, and conducting fractionating to obtain corresponding alkane and aldehyde/ketone. Alcohol disproportionation is efficient and atom-economical conversion without any additional oxidizing agent and reducing agent, and hydrocarbon and aldehyde/ketone molecules which are easy to separate can be formed at the same time. Meanwhile, the method has wide functional group tolerance, various substrate samples including aryl alcohol derivatives, heterocyclic alcohol derivatives, allyl alcohol derivatives and dihydric alcohol are tested, and the result shows that most of the substrate samples show good or extremely good yield.
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Paragraph 0034-0035
(2021/06/13)
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- Rh-catalyzed highly regioselective hydroformylation to linear aldehydes by employing porous organic polymer as a ligand
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In this work, we developed a new structural porous organic polymer containing biphosphoramidite unit, which can be used as a solid bidentate phosphorous ligand for rhodium-catalyzed solvent-free higher olefins hydroformylation. The resultant catalyst demonstrated unprecedently high regioselectivity to linear aldehydes and could be readily recovered for successive reuses with good stability in both catalytic activity and regioselectivity. This journal is
- Wang, Zhaozhan,Yang, Yong
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p. 29263 - 29267
(2020/10/06)
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- Glycerol Boosted Rh-Catalyzed Hydroaminomethylation Reaction: A Mechanistic Insight
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We report a Rh-catalyzed hydroaminomethylation reaction of terminal alkenes in glycerol that proceeds efficiently under mild conditions to produce the corresponding amines in relatively high selectivity towards linear amines, moderate to excellent yields by using a low catalyst loading (1 mol % [Rh], 2 mol % phosphine) and relative low pressure (H2/CO, 1:1, total pressure 10 bar). This work sheds light on the importance of glycerol in enabling enamine reduction via hydrogen transfer. Moreover, evidence for the crucial role of Rh as chemoselective catalyst in the condensation step has been obtained for the first time in the frame of the hydroaminomethylation reaction by precluding deleterious aldol condensation reactions. The hydroaminomethylation proceeds under a molecular regime; the outcome of catalytically active species into metal-based nanoparticles renders the catalytic system inactive.
- Serrano-Maldonado, Alejandro,Dang-Bao, Trung,Favier, Isabelle,Guerrero-Ríos, Itzel,Pla, Daniel,Gómez, Montserrat
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supporting information
p. 12553 - 12559
(2020/09/09)
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- ALCOHOL DEHYDRATION CATALYST, PREPARATION METHOD THE SAME AND METHOD FOR PREPARING ALPHA-OLEFINS USING THE SAME
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The present invention relates to a catalyst for dehydration of a primary alcohol, a method of preparing the same, and a method of producing an alpha-olefin using the same. The catalyst for dehydration of a primary alcohol according to the present invention has an excellent catalyst stability while having an excellent activity with respect to dehydration, and a high turnover frequency, such that a linear alpha-olefin with high purity may be produced with a high selectivity even in a case where a relatively small amount of a cocatalyst is added as compared with a homogeneous catalyst system.
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Paragraph 0030; 0132; 0133
(2020/11/24)
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- Porous organic polymer supported rhodium as a reusable heterogeneous catalyst for hydroformylation of olefins
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A new porous organic polymer has been prepared via copolymerization of divinyl-functionalized phosphoramidite ligand and tris(4-vinylphenyl)phosphine. The porous polymer was loaded with Rh(acac)CO2 to yield a supported Rh catalyst, which demonstrated good regioselectivity (l/b = 6.7-52.8) and high catalytic activity (TON up to 45.3 × 104) in hydroformylation of terminal and internal olefins. Remarkably, the heterogeneous catalyst can be reused at least 10 cycles without losing activity and selectivity in hydroformylation of 1-hexene.
- Jia, Xiaofei,Liang, Zuyu,Chen, Jianbin,Lv, Jinhe,Zhang, Kai,Gao, Mingjie,Zong, Lingbo,Xie, Congxia
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supporting information
p. 2147 - 2150
(2019/03/26)
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- Gem-Dialkyl Effect in Diphosphine Ligands: Synthesis, Coordination Behavior, and Application in Pd-Catalyzed Hydroformylation
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A series of palladium complexes with C3-bridged bidentate bis(diphenylphosphino)propane ligands with substituents of varying steric bulk at the central carbon have been synthesized. The size of the gem-dialkyl substituents affects the C-C-C bond angles within the ligands and consequently the P-M-P ligand bite angles. A combination of solid-state X-ray diffraction (XRD) and density functional theory (DFT) studies has shown that an increase in substituent size results in a distortion of the 6-membered metal-ligand chair conformation toward a boat conformation, to avoid bond angle strain. The influence of the gem-dialkyl effect on the catalytic performance of the complexes in palladium-catalyzed hydroformylation of 1-octene has been investigated. While hydroformylation activity to nonanal decreases with increasing size of the gem-dialkyl substituents, a change in chemoselectivity toward nonanol via reductive hydroformylation is observed.
- Aitipamula, Srinivasulu,Britovsek, George J. P.,Nobbs, James D.,Romain, Charles,Tay, Dillon W. P.,Van Meurs, Martin,White, Andrew J. P.
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p. 663 - 671
(2020/01/02)
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- A new air-stable and reusable tetraphosphine ligand for rhodium-catalyzed hydroformylation of terminal olefins at low temperature
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Tetraphosphine and bisphosphine ligands were synthesized, characterized and employed in Rh-catalyzed hydroformylation of 1-octene and 1-hexene. Conversion of over 97.7% and aldehyde yield of 94.1% were achieved at 60°C, 20?bar. This remarkable performance could also be retained at lower temperature (i.e. 40°C) by prolonging the reaction time. The tetraphosphine ligand-modified Rh catalyst could be reused for at least seven successive runs with catalytic activity and selectivity almost unchanged; the catalyst was separated from the products and recycled directly in homogeneous hydroformylation, indicating that the catalyst might have good stability. 31P NMR and high-resolution mass spectral characterization hinted that the reason for the reusability of the catalyst might be that the tetraphosphine ligand is relatively air-stable and is probably slowly oxidized during the recycling runs. The tetraphosphine ligand has four phosphorus atoms to be partially oxidized and could still coordinate with the Rh center via the unoxidized phosphorus atoms to stabilize the catalyst, based on the multiple chelating modes of the tetraphosphine ligand. Hence, the catalytic activity and selectivity could be retained for a certain number of runs.
- Zhou, Fanding,Zhang, Lin,Wu, Qianhui,Guo, Fuya,Tang, Songbai,Xu, Bin,Yuan, Maolin,Fu, Haiyan,Li, Ruixiang,Zheng, Xueli,Chen, Hua
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- Sodium diisopropylamide-mediated dehydrohalogenations: Influence of primary- A nd secondary-shell solvation
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Eliminations of alkyl halides by sodium diisopropylamide (NaDA) in tetrahydrofuran (THF)/hexane or THF/N,N-dimethylethylamine (DMEA) solutions are facile and complementary to analogous reactions of lithium diisopropylamide in THF. Rate studies show a dominance of monomer-based metalations and prevalent secondary-shell solvation effects overlaid on primary-shell effects. 1-Halooctanes exclusively undergo elimination rather than substitution. Rate and isotopic labeling studies on 1-bromooctane reveal an E2-like elimination pathway via trisolvated NaDA monomer. By contrast, 1-chlorooctane is eliminated via disolvated monomer through a carbenoid mechanism. exo-2-Norbornyl chloride and bromide are also eliminated via disolvated monomer; a syn E2 mechanism is inferred for these substrates. The cis- A nd trans-4-tert-butylcyclohexyl bromides show a preference for the elimination of the cis isomer (kcis/ax/ktrans/eq = 10). Rate and isotopic labeling studies are consistent with a trans-diaxial E2 elimination via trisolvated monomer for the cis isomer and a carbenoid mechanism via disolvated monomer for the trans isomer. Vicinal haloethers show substrate-dependent reactivities, affording alkynes and enol ethers. trans-1-Bromo-2-methoxycyclohexane provides enol ether 1-methoxycyclohexene, while trans-1-bromo-2-methoxycyclooctane provides dimeric products consistent with fleeting cycloocta-1,2-diene (cyclic allene), which was fully characterized as two conformers.
- Ma, Yun,Algera, Russell F.,Woltornist, Ryan A.,Collum, David B.
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supporting information
p. 10860 - 10869
(2019/09/30)
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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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- Air-stable and reusable cobalt ion-doped titanium oxide catalyst for alkene hydrosilylation
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Alkene hydrosilylation is important for the synthesis of organosilicon compounds, for which precious metal complexes have been used as industrial catalysts. Considering environmental and economic concerns, the development of earth-abundant metal catalysts with high stability, easy separability, and high reusability is strongly desired. Herein, we report that a new cobalt ion-doped titanium dioxide (Co/TiO2) catalyst was synthesized by hydrogen treatment method. The Co/TiO2 catalyst acts as a highly efficient heterogeneous catalyst for the anti-Markovnikov hydrosilylation of alkenes under solvent-free conditions. Various alkenes were selectively converted to the corresponding alkylsilanes. This catalyst showed high stability in air and high reusability with maintained activity. The investigation of the relationship between the active site structure and catalytic performance of Co/TiO2 disclosed that the high stability and durability of Co/TiO2 are originated from the strong interaction between Co and TiO2 through the formation of CoTiO3 solid solution species.
- Mitsudome, Takato,Fujita, Shu,Sheng, Min,Yamasaki, Jun,Kobayashi, Keita,Yoshida, Tomoko,Maeno, Zen,Mizugaki, Tomoo,Jitsukawa, Koichiro,Kaneda, Kiyotomi
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supporting information
p. 4566 - 4570
(2019/08/21)
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- Specialized ruthenium olefin metathesis catalysts bearing bulky unsymmetrical NHC Ligands: Computations, synthesis, and application
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Second-generation ruthenium olefin metathesis catalysts were investigated with systematic variation of the unsymmetrical uNHC ligands. Depending on the uNHC steric bulk, the catalysts exhibited different activity and selectivity in metathesis reactions. DFT calculations and X-ray crystallographic data were used to understand the influence of uNHC ligand structure on the catalyst properties. Furthermore, the catalysts were examined in the context of reactions that are problematic for general-purpose Ru catalysts, including industrially important self-cross metathesis of α-olefins and ethenolysis of ethyl oleate.
- Ma?ecki, Pawe?,Gajda, Katarzyna,Gajda, Roman,Wo?niak, Krzysztof,Trzaskowski, Bartosz,Kajetanowicz, Anna,Grela, Karol
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p. 587 - 598
(2019/01/08)
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- POCN Ni(ii) pincer complexes: Synthesis, characterization and evaluation of catalytic hydrosilylation and hydroboration activities
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A series of iminophosphinite POCN pincer Ni(ii) complexes, (POCN)NiMe and (POCN)NiLn(BX4) (L = CH3CN, n = 0, 1; X = F, Ph, C6F5), have been developed and subjected to catalytic hydrosilylation of alkenes, aldehydes and ketones and hydroboration of carbonyl compounds. The stoichiometric reactivity of (POCN)NiMe and (POCN)Ni(BF4) with PhSiH3 and HBPin suggests that catalytic reactions proceed via the hydride intermediate (POCN)NiH. With regard to reactions with HBPin, efficient and mild hydroboration of a variety of carbonyl compounds, including highly chemoselective hydroboration of benzaldehyde in the presence of other common potent reductive functional groups, such as alkenes, alkynes, esters, amides, nitriles, nitro compounds and even ketones, and the first example of base metal catalyzed hydroboration of amides, including mild direct hydroborative reduction of primary and secondary amides to borylated amines were demonstrated for (POCN)NiMe.
- Gudun, Kristina A.,Segizbayev, Medet,Adamov, Assyl,Balanay, Mannix P.,Khalimon, Andrey Y.,Plessow, Philipp N.,Lyssenko, Konstantin A.
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supporting information
p. 1732 - 1746
(2019/03/07)
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- Fe and Co Complexes of Rigidly Planar Phosphino-Quinoline-Pyridine Ligands for Catalytic Hydrosilylation and Dehydrogenative Silylation
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Co and Fe dihalide complexes of a new rigidly planar PNN ligand platform are prepared and examined as precatalysts for hydrosilylation of alkenes. Lithiation of Thummel's 8-bromo-2-(pyrid-2′-yl)quinoline followed by treatment with (i-Pr)2PCl and (C6F5)2PCl afforded the phosphine-quinoline-pyridine ligands, abbreviated RPQpy for R = i-Pr and C6F5, respectively. These ligands form 1:1 adducts with the dichlorides and dibromides of iron and cobalt. Crystallographic characterization of FeBr2(iPrPQpy), FeBr2(ArFPQpy), CoCl2(iPrPQpy), CoBr2(iPrPQpy), and CoCl2(ArFPQpy) confirmed that the M-P-C-C-N-C-C-N portion of these complexes is planar within 0.078 ? unlike previous generations of PNN complexes where deviations from planarity were ～0.35 ?. Bond distances as well as magnetism indicate that the Fe complexes are high spin and the cobalt complexes are high spin or participate in spin equilibria. Also investigated were the NNN analogues of the RPQpy ligands, wherein the phosphine group was replaced by the mesityl ketimine. The complexes FeBr2(MesNQpy) and CoCl2(MesNQpy) were characterized crystallographically. Reduction of MX2(RPQpy) complexes with NaBHEt3 generates catalysts active for anti-Markovnikov silylation of simple and complex 1-alkenes with a variety of hydrosilanes. Catalysts derived from MesNQpy exhibited low activity. Fe-RPQpy derived catalysts favor hydrosilylation, whereas Co-RPQpy based catalysts favor dehydrogenative silylation. Catalysts derived from CoX2(iPrPQpy) convert hydrosilanes and ethylene to vinylsilanes. Related experiments were conducted on propylene to give propenylsilanes.
- Basu, Debashis,Gilbert-Wilson, Ryan,Gray, Danielle L.,Rauchfuss, Thomas B.,Dash, Aswini K.
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p. 2760 - 2768
(2018/09/10)
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- NiH-Catalyzed Reductive Relay Hydroalkylation: A Strategy for the Remote C(sp3)?H Alkylation of Alkenes
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The terminal-selective, remote C(sp3)?H alkylation of alkenes was achieved by a relay process combining NiH-catalyzed hydrometalation, chain walking, and alkylation. This method enables the construction of unfunctionalized C(sp3)?C(sp3) bonds under mild conditions from two simple feedstock chemicals, namely olefins and alkyl halides. The practical value of this transformation is further demonstrated by the large-scale and regioconvergent alkylation of isomeric mixtures of olefins at low catalyst loadings.
- Zhou, Fang,Zhu, Jin,Zhang, Yao,Zhu, Shaolin
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supporting information
p. 4058 - 4062
(2018/03/21)
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- Transition metal triflate catalyzed conversion of alcohols, ethers and esters to olefins
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Herein, we report an efficient transition metal triflate catalyzed approach to convert biomass-based compounds, such as monoterpene alcohols, sugar alcohols, octyl acetate and tea tree oil, to their corresponding olefins in high yields. The reaction proceeds through C-O bond cleavage under solvent-free conditions, where the catalytic activity is determined by the oxophilicity and the Lewis acidity of the metal catalyst. In addition, we demonstrate how the oxygen containing functionality affects the formation of the olefins. Furthermore, the robustness of the used metal triflate catalysts, Fe(OTf)3 and Hf(OTf)4, is highlighted by their ability to convert an over 2400-fold excess of 2-octanol to octenes in high isolated yields.
- Keskiv?li,Parviainen,Lagerblom,Repo
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p. 15111 - 15118
(2018/05/04)
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- Azoliniums, Adducts, NHCs and Azomethine Ylides: Divergence in Wanzlick Equilibrium and Olefin Metathesis Catalyst Formation
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The dimerization of a saturated N-heterocyclic carbene (NHC) to tricyclic piperazine in preference to the commonly observed Wanzlick dimerization is presented. Mechanistic investigations revealed that the N-fluorene substituent of the heterocycle is implicated in both ring opening of corresponding carbene dimer and tautomerization of NHC to an azomethine ylide. This has consequences for the fate of the NHC when generated from either an azolinium salt or a pentafluorophenyl adduct. The insights gained permitted the synthesis of a new indenylidene metathesis precatalyst, which exhibits exceptional selectivity and high TONS in self-metathesis of 1-octene.
- Jolly, Phillip I.,Marczyk, Anna,Ma?ecki, Pawe?,Ablialimov, Osman,Trzybiński, Damian,Wo?niak, Krzysztof,Osella, Silvio,Trzaskowski, Bartosz,Grela, Karol
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supporting information
p. 4785 - 4789
(2018/03/21)
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- Thermal, Catalytic Conversion of Alkanes to Linear Aldehydes and Linear Amines
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Alkanes, the main constituents of petroleum, are attractive feedstocks for producing value-added chemicals. Linear aldehydes and amines are two of the most important building blocks in the chemical industry. To date, there have been no effective methods for directly converting n-alkanes to linear aldehydes and linear amines. Here, we report a molecular dual-catalyst system for production of linear aldehydes via regioselective carbonylation of n-alkanes. The system is comprised of a pincer iridium catalyst for transfer-dehydrogenation of the alkane using t-butylethylene or ethylene as a hydrogen acceptor working sequentially with a rhodium catalyst for olefin isomerization-hydroformylation with syngas. The system exhibits high regioselectivity for linear aldehydes and gives high catalytic turnover numbers when using ethylene as the acceptor. In addition, the direct conversion of light alkanes, n-pentane and n-hexane, to siloxy-terminated alkyl aldehydes through a sequence of Ir/Fe-catalyzed alkane silylation and Ir/Rh-catalyzed alkane carbonylation, is described. Finally, the Ir/Rh dual-catalyst strategy has been successfully applied to regioselective alkane aminomethylation to form linear alkyl amines.
- Tang, Xinxin,Jia, Xiangqing,Huang, Zheng
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supporting information
p. 4157 - 4163
(2018/03/29)
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- Reductive-hydroformylation of 1-octene to nonanol using fibrous Co3O4 catalyst
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This work reports, reductive-hydroformylation of 1-octene to nonanol in the presence of fine fibrous cobalt oxide (Co3O4) nano-catalyst prepared via urea reduction method under phosphine-free and additive free condition. Co3O4 nano-catalyst was prepared by the wet chemical method and was characterized using various instrumental techniques like FEG-SEM, EDS, XRD, TPR and FTIR. The effects of various reaction parameters such as temperature, synthesis gas (CO/H2) pressure/ratio, catalyst loading, solvent and time were studied. The reaction was successfully achieved in tetrahydrofuran (THF) as the solvent medium. This reaction believed to takes place through the generation of HCox(CO)y active catalyst species. The Co3O4 nano-catalyst could be recycled up to three consecutive cycles.
- Bhagade, Sachin S.,Chaurasia, Shivkumar R.,Bhanage, Bhalchandra M.
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p. 147 - 152
(2017/09/06)
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- Engineering active sites on reduced graphene oxide by hydrogen plasma irradiation: Mimicking bifunctional metal/supported catalysts in hydrogenation reactions
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H2 plasma has been used to generate carbon vacancies on reduced graphene oxide to increase its catalytic activity as a hydrogenation catalyst. A relationship between the power of the plasma treatment and the exposure time with the activity of the material was observed for CC double bond hydrogenation. The activity data in the case of 1-octene, showing skeletal isomerization besides hydrogenation, indicate that H2 plasma treatment can introduce hydrogenating and acid sites rendering a bifunctional catalyst that is reminiscent of the activity of noble metals supported on acid supports.
- Primo, Ana,Franconetti, Antonio,Magureanu, Monica,Mandache, Nicolae Bogdan,Bucur, Cristina,Rizescu, Cristina,Cojocaru, Bogdan,Parvulescu, Vasile I.,Garcia, Hermenegildo
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p. 2611 - 2623
(2018/06/18)
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- NCP ligand, [...] complex, synthesis method, intermediate and application
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The invention discloses an NCP ligand, iridium complex, synthetic method, intermediate and application thereof. The invention provides an NCP ligand and an NCP ligand iridium complex, wherein R1, R2, R3, R4, R5, R6 and R7 separately represent hydrogen atom or C1-C30 alkyl, R' and R'' independently represent C1-C30 alkyl. The invention provides the application of the NCP ligand iridium complex to the catalysis of alkane dehydrogenation reaction, olefin isomerization reaction, alcohol dehydrogenation reaction, ester alpha alkylation reaction, and amide alpha alkylation reaction. The NCP ligand provided by the invention contains dialkyl substituted phosphine, which has strong electron donating ability and can form a NCP ligand iridium complex by complexing with iridium. The NCP ligand iridium complex uses pyridine to replace a conventional alkyl phosphate electron donor, and has the advantages of good stability, high selectivity on alkane dehydrogenation reaction, mild reaction conditions, good catalytic effect, and industrial production prospect.
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Paragraph 0103; 0197-0199
(2018/07/30)
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- Alkene Isomerization-Hydroboration Catalyzed by First-Row Transition-Metal (Mn, Fe, Co, and Ni) N-Phosphinoamidinate Complexes: Origin of Reactivity and Selectivity
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We describe the results of our combined experimental and computational investigation of structurally analogous (N-phosphinoamidinate)metal(N(SiMe3)2) precatalysts ((PN)M; M = Mn2+, Fe2+, Co2+, and Ni2+ d5-d8) in the isomerization-hydroboration of 1-octene, cis-4-octene, or trans-4-octene (1a-c) with HBPin. As part of this investigation, the synthesis and crystallographic characterization of diamagnetic (PN)Ni, ((PN)NiH)2, (PN)NiH(L) (L = pyridine or DMAP), and (PN)Ni(NHdipp) (dipp = 2,6-iPr2C6H3) are reported. Divergent catalytic reactivity and selectivity was noted for members of the (PN)M series; (PN)Mn and (PN)Ni afforded poor hydroboration yields, whereas the use of (PN)Fe or (PN)Co afforded high conversion and selectivity for the terminal borylation product, (n-octyl)BPin (2a). DFT calculations involving (PN)M as well as stoichiometric reactivity studies featuring (PN)Ni confirmed that (PN)MH intermediates generated upon reaction of (PN)M with HBPin represent viable catalytic species whereby formation of putative (PN)Ni(H2BPin) is reversible. Conversely, poor catalytic performance was noted for ((PN)NiH)2 and (PN)NiH(L) (L = pyridine or DMAP). Using DFT calculations, the relative reactivity of (PN)M precatalysts was found to be a function of their spin-state energy gaps. For reaction of (PN)MnH with trans-4-octene (1c) there is no viable spin crossover mechanism and migratory insertion is slow, resulting in poor reaction yields. In contrast, (PN)FeH can access a lower barrier through spin crossover, whereas (PN)CoH has a very low migratory insertion barrier from its low spin state. While (PN)NiH has a reasonable migratory insertion barrier, it is plausible that off-catalytic cycle intermediates are responsible for the diminished reaction rate and product yields that are observed experimentally. On the basis of the computed isomerization and borylation energy landscapes, a Curtin-Hammett-type scenario with fast isomerization through β-hydride elimination and migratory insertion steps is proposed, giving rise to a catalytic equilibrium of isomeric (PN)M(octyl) resting states, followed by slow product-forming borylation. The significantly lower barriers calculated for borylation of terminal (PN)M(n-octyl) species versus isomeric internal (PN)M(CHR2) intermediates provides a rationale for the experimentally observed terminal isomerization-hydroboration selectivity.
- Macaulay, Casper M.,Gustafson, Samantha J.,Fuller, Jack T.,Kwon, Doo-Hyun,Ogawa, Takahiko,Ferguson, Michael J.,McDonald, Robert,Lumsden, Michael D.,Bischof, Steven M.,Sydora, Orson L.,Ess, Daniel H.,Stradiotto, Mark,Turculet, Laura
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p. 9907 - 9925
(2018/10/15)
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- Disilaruthena- and Ferracyclic Complexes Containing Isocyanide Ligands as Effective Catalysts for Hydrogenation of Unfunctionalized Sterically Hindered Alkenes
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Disilaferra- and disilaruthenacyclic complexes containing mesityl isocyanide as a ligand, 3′ and 4′, were synthesized and characterized by spectroscopy and crystallography. Both 3′ and 4′ showed excellent catalytic activity for the hydrogenation of alkenes. Compared with iron and ruthenium carbonyl analogues, 1′ and 2′, the isocyanide complexes 3′ and 4′ were more robust under the hydrogenation conditions, and were still active even at higher temperatures (～80 °C) under high hydrogen pressure (～20 atm). The iron complex 3′ exhibited the highest catalytic activity toward hydrogenation of mono-, di-, tri-, and tetrasubstituted alkenes among currently reported iron catalysts. Ruthenium complex 4′ catalyzed hydrogenation under very mild conditions, such as room temperature and 1 atm of H2. The remarkably high catalytic activity of 4′ for hydrogenation of unfunctionalized tetrasubstituted alkenes was especially notable, because it was comparable to the activity of iridium complexes reported by Crabtree and Pfaltz, which are catalysts with the highest activity in the literature. DFT calculations suggested two plausible catalytic cycles, both of which involved activation of H2 assisted by the metal-silicon bond through σ-bond metathesis of late transition metals (oxidative hydrogen migration). The linear structure of M C≡N - C (ipso carbon of the mesityl group) played an essential role in the efficient hydrogenation of sterically hindered tetrasubstituted alkenes.
- Sunada, Yusuke,Ogushi, Hajime,Yamamoto, Taiji,Uto, Shoko,Sawano, Mina,Tahara, Atsushi,Tanaka, Hiromasa,Shiota, Yoshihito,Yoshizawa, Kazunari,Nagashima, Hideo
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supporting information
p. 4119 - 4134
(2018/03/29)
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- Flow chemistry-enabled studies of rhodium-catalyzed hydroformylation reactions
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We present an automated microscale flow chemistry platform for rapid performance evaluation of continuous and discrete reaction parameters in homogeneous hydroformylation reactions. We demonstrate the versatility of the developed microfluidic platform through a systematic study of the effects of a library of phosphine-based ligands on catalytic activity and regioselectivity.
- Zhu, Cheng,Raghuvanshi, Keshav,Coley, Connor W.,Mason, Dawn,Rodgers, Jody,Janka, Mesfin E.,Abolhasani, Milad
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supporting information
p. 8567 - 8570
(2018/08/06)
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- Mononuclear ruthenium complex and organic synthesis reaction using same
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A neutral or cationic mononuclear ruthenium divalent complex represented by formula (1) can actualize exceptional catalytic activity in at least one reaction among a hydrosilylation reaction, hydrogenation reaction, and carbonyl compound reduction reaction. (In the formula, R1-R6 each independently represent a hydrogen atom or an alkyl group, aryl group, aralkyl group, organooxy group, monoorganoamino group, diorganoamino group, monoorganophosphino group, diorganophosphino group, monoorganosilyl group, diorganosilyl group, triorganosilyl group, or organothio group optionally substituted by X; at least one pair comprising any of R1-R3 and any of R4-R6 together represents a crosslinkable substituent; X represents a halogen atom, organooxy group, monoorganoamino group, diorganoamino group, or organothio group; L each independently represent a two-electron ligand other than CO and thiourea ligands; two L may bond to each other; and m represents an integer of 3 or 4.)
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Page/Page column 34; 35; 36; 37
(2018/03/26)
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- Olefin oligomerization via new and efficient Br?nsted acidic ionic liquid catalyst systems
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Olefin oligomerization reaction catalyzed by new catalyst systems (a Br?nsted-acidic ionic liquid as the main catalyst and tricaprylylmethylammonium chloride as the co-catalyst) has been investigated. The synthesized Br?nsted acidic ionic liquids were characterized by Fourier transform infrared spectroscopy (FT-IR), ultraviolet-visible spectroscopy (UV), 1H nuclear magnetic resonance (NMR), and 13C NMR to analyze their structures and acidities. The influence of different ionic liquids, ionic liquid loading, different co-catalysts, catalyst ratios (mole ratio of ionic liquid to co-catalyst), reaction time, pressure, temperature, solvent, source of reactants, and the recycling of catalyst systems was studied. Among the synthesized ionic liquids, 1-(4-sulfonic acid)butyl-3-hexylimidazolium hydrogen sulfate ([HIMBs]HSO4) exhibited the best catalytic activity under the tested reaction conditions. The conversion of isobutene and selectivity of trimers were 83.21% and 35.80%, respectively, at the optimum reaction conditions. Furthermore, the catalyst system can be easily separated and reused; a feasible reaction mechanism is proposed on the basis of the distribution of experimental products.
- Wang, Guoqin,Song, Heyuan,Li, Ruiyun,Li, Zhen,Chen, Jing
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p. 1110 - 1120
(2018/05/28)
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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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- Tuning the Porphyrin Building Block in Self-Assembled Cages for Branched-Selective Hydroformylation of Propene
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Unprecedented regioselectivity to the branched aldehyde product in the hydroformylation of propene was attained on embedding a rhodium complex in supramolecular assembly L2, formed by coordination-driven self-assembly of tris(meta-pyridyl)phosphine and zinc(II) porpholactone. The design of cage L2 is based on the ligand-template approach, in which the ligand acts as a template for cage formation. Previously, first-generation cage L1, in which zinc(II) porphyrin units were utilized instead of porpholactones, was reported. Binding studies demonstrate that the association constant for the formation of second-generation cage L2 is nearly an order of magnitude higher than that of L1. This strengthened binding allows cage L2 to remain intact in polar and industrially relevant solvents. As a consequence, the unprecedented regioselectivity for branched aldehyde products can be maintained in polar and coordinating solvents by using the second-generation assembly.
- Wang, Xiaowu,Nurttila, Sandra S.,Dzik, Wojciech I.,Becker, René,Rodgers, Jody,Reek, Joost N. H.
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supporting information
p. 14769 - 14777
(2017/09/06)
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- New palladium (II) complexes with Thiophene and furan bridged N-Acylbenzotriazole ligands: Synthesis, characterization and hydrogenation activity in ionic liquid
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Palladium complexes of N-acylbenzotriazole derivative ligands were synthesized and characterized. The catalytic activities of complexes of ([PdL1(OAc)2] and [PdL2(OAc)2]) were investigated in relation to hydrogenation reactions of styrene, 1-octene and cyclohexene in [bmim][BF4] as greener reaction media. 100% ethyl benzene conversion was obtained with both complexes in 1?h reaction time. Additionally, 100% 1-octene conversion was reached within the same period of time with [PdL2(OAc)2] complex. In cyclohexene hydrogenation, product formation reached up to 67% at 363?K with [PdL1(OAc)2] complex. Reusability tests were conducted under the highest product conversion conditions, and both catalysts were found to be efficient up to 5?cycles for all substrates. The other reaction parameters such as solvent effect, H2 (g) pressure, ns/nc ratio were also investigated.
- ünver, Hakan,Yilmaz, Filiz
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p. 875 - 880
(2017/06/29)
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- Palladium-Catalyzed Oxidative Borylation of Allylic C-H Bonds in Alkenes
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This communication describes an efficient palladium pincer complex-catalyzed allylic C-H borylation of alkenes. The transformation exhibits high regio- and stereoselectivity with a variety of linear alkenes. A synthetically useful feature of this allylic C-H borylation method is that all allyl-Bpin products can be isolated in usually high yields. Preliminary mechanistic studies indicate that this C-H borylation reaction proceeds via Pd(IV) pincer complex intermediates.
- Mao, Lujia,Bertermann, Rüdiger,Rachor, Simon G.,Szabó, Kálmán J.,Marder, Todd B.
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supporting information
p. 6590 - 6593
(2017/12/26)
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- Phosphoramidite complexes of Pd(II), Pt(II) and Rh(I): An effective hydrosilylation catalyst of 1-hexyne and 1-octene
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The hydrophosphorane HP(OC6H4NMe)2 was used to prepare the diastereotopic complexes [MCl2{P(OC6H4NMe)OC6H4NHMe}] (M?=?Pd, Pt) by reaction with [MCl2(PhCN)2], and [RhCl(PPh3){P(OC6H4NMe)OC6H4NHMe}] by reaction with [RhCl(PPh3)3]. To form these complexes, the phosphorane undergoes ring-opening, whereby it is coordinated as the tautomeric neutral phosphoramidite-amino chelating ligand. The crystal structure of [RhCl(PPh3){P(OC6H4NMe)OC6H4NHMe}] was determined and the geometry about the Rh(I) atom is square-planar with cis-disposed phosphorus-donor ligands. The Rh–P distance is shortened (2.1056(6) ?) due to Rh(d)?→?P π-backbonding. In addition, [RhCl(PPh3){P(OC6H4NMe)OC6H4NHMe}] was shown to be an effective regio- and stereoselective catalyst for the hydrosilylation of 1-octene and 1-hexyne.
- Carroll, Hannah K.,Parlane, Fraser G.L.,Reich, Noah,Jelier, Benson J.,Montgomery, Craig D.
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- Acid-catalysed carboxymethylation, methylation and dehydration of alcohols and phenols with dimethyl carbonate under mild conditions
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Dimethyl carbonate (DMC) chemistry has been extended to include acid-catalysed reactions of different aliphatic alcohols and phenols. For the first time, p-toluenesulfonic acid (PTSA), H2SO4, AlCl3 and FeCl3 have been shown to aid carboxymethylation for primary aliphatic alcohols at catalytic loadings with quantitative conversion and selectivity. For carboxymethylation of secondary alcohols, stoichiometric PTSA and catalytic AlCl3 both gave quantitative conversion and selectivity. Stoichiometric FeCl3 and H2SO4 promoted dehydration of linear aliphatic alcohols. Additionally FeCl3 catalysed methylation of cyclohexanol, whilst AlCl3 resulted in methylation of phenolic compounds. This research expands the range of potential application for DMC in green chemistry.
- Jin, Saimeng,Hunt, Andrew J.,Clark, James H.,McElroy, Con Robert
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supporting information
p. 5839 - 5844
(2016/11/06)
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- PROCESS FOR DEHYDROGENATION OF ALKYL-CONTAINING COMPOUNDS USING MOLYBDENUM AND TUNGSTEN NITROSYL COMPLEXES
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A process for the dehydrogenation of alkyl-containing compounds comprises reacting an alkyl-containing compound and a Group VI nitrosyl complex characterized as a transition metal complex having the composition Cp'M(NO)(R1)(R2), wherein Cp' is selected from certain substituted and unsubstituted η5-cyclopentadienyl groups; M is W or Mo; and R1 and R2 are independently selected from CH2C(CH3)3; CH2Si(CH3)3; CH2(C6H5); CH3; hydrogen; and η3-allyl; provided that if R1 is hydrogen, R2 is η3-allyl; under conditions such that the alkyl-containing compound is converted to an olefin, and in particular embodiments, a terminal olefin. The dehydrogenation can be carried out using a neat and/or undried alkyl-containing compound and/or may be conducted under air, and does not require a sacrificial olefin to drive the reaction, thereby increasing convenience and decreasing cost in comparison with some other dehydrogenation processes.
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Page/Page column 8
(2016/08/10)
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- Synthesis, structure and thermolysis of cis-dialkylplatinum(II) complexes - Experimental and theoretical perceptions
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The formation of new C-C bonds by metal complexes always stimulates great interest because these fundamental reaction types possess numerous potential applications in organic synthesis. These reactions are well documented for a variety of transition metal complexes. Herein we report synthesis and characterization of a series of platinum-dialkyl complexes (1-10) of the type [Pt(L2)R2], (where L2 = dppp (1,3-bis(diphenylphosphino)propane or L = PPh3; R = n-butyl to n-nonyl) with a view to understand the organic product distribution patterns on thermolysis. The single crystal X-ray structures of the complexes [Pt(dppp){CH2(CH2)3CH3}2] (1) and [Pt(dppp){CH2(CH2)6CH3}2] (7) are reported. Thermal decomposition studies of these complexes show interesting behaviour; the longer chain dialkyls i.e. C7-C9 complexes undergo reductive elimination whereas the shorter chain dialkyl complexes and C3-C6 prefer only the β-hydride elimination reaction. Possible mechanistic aspects are discussed. Theoretical calculations reveal the strongest delocalizations in both complexes involve the interaction of Pt-C bond pair electron density with the trans positioned Pt-P antibonding orbital and vice-versa.
- Venkatesh, Sadhana,Sravani, Chinduluri,Janardan, Sannapaneni,Suman, Pothini,Goud, E. Veerashekhara,Pavankumar,Leninkumar, Vardi,Bhat, Haamid R.,Sivaramakrishna, Akella,Vijayakrishna, Kari,Jha, Prakash C.,Smith, Gregory S.
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- Synthesis of phosphorus amidite ligand and investigation of its flexibility impact on rhodium-catalyzed hydroformylation of 1-octene
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A new flexible 2,2′-bis((dipyrrolylphosphinooxy)methyl)-1,1′-(±)-biphenyl ligand (L1) was synthesized, characterized and employed in the hydroformylation of 1-octene. In order to investigate the influence of ligand flexibility on the catalytic performance, its analogue 2,2′-bis (dipyrrolylphosphinooxy)-1,1′-(±)-biphenyl (L3) was also applied in the hydroformylation of 1-octene. With the presence of L1, the aldehyde selectivity was approximately 10% higher than that with the relevant less flexible ligand L3. Theoretical calculation indicated that the olefin-insertion into the Rh-H bond of intermediate III and the CO-insertion into Rh-alkyl bond of intermediate V were favorable in terms of thermodynamics, which were vital to the generation of aldehyde. Meanwhile, the ligand flexibility was indeed improved by adding a methylene between benzene and oxygen atom that connected with P, as the calculation showed the variation of the bite angle ∠P-Rh-P of the intermediates I-VI was 8.7° in L1-system, as for L3-system, the variation was 14.0°. This structural feature might make the olefin-insertion and the CO-insertion occur more easily in the L1-system and resulted in higher aldehyde selectivity.
- Han, Weibiao,Qin, Song,Shu, Xiao,Wu, Qianhui,Xu, Bin,Li, Ruixiang,Zheng, Xueli,Chen, Hua
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p. 53012 - 53016
(2016/06/14)
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- Reactivity of mixed organozinc and mixed organocopper reagents: 14. Phosphine-nickel catalyzed aryl-allyl coupling of (n-butyl)(aryl)zincs. Ligand and substrate control on the group selectivity and regioselectivity
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The group selectivity and regioselectivity in the allylation of mixed (n-butyl)(aryl)zinc reagents in THF depends on the nickel catalyst type and also on nature of the allylic substrate. Allylation of (n-butyl)(phenyl)zinc reagent with alkyl substituted primary allylic chlorides and acetates in the presence of NiCl2(dppf) catalysis affords the phenyl coupling product with γ-selectivity. However, allylation with aryl substituted primary allylic substrates results in both phenyl- and alkyl-coupling products with medium α-selectivity in the presence of NiCl2(dppf) catalysis whereas phenyl coupling product is formed with α-selectivity in the presence of NiCl2(Ph3P)2 catalysis. This new NiCl2(dppf) catalyzed protocol for γ-selective aryl allylation of (n-butyl)(aryl)zinc reagents with alkyl substituted primary allylic chlorides in THF at room temperature provides an atom economic alternative to allylation of (aryl)2Zn reagents. A mechanism for the dependence of group selectivity and regioselectivity of Ni catalyzed allylation of (n-butyl)(aryl)zinc reagents on the catalyst ligand and the substrate was proposed.
- Kalkan, Melike,Erdik, Ender
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- Oligomerization of 1-butene with a homogeneous catalyst system based on allylic nickel complexes
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The oligomerization of 1-butene with a nickel-based catalyst system constitutes an elegant synthesis method for obtaining linear octenes from readily available chemicals. It is well known that the bis-(cyclooctadiene)nickel(0)-complex (Ni(COD)2) can be used in combination with 1,1,1,5,5,5-hexafluoroacetylacetone (hfacac) forming [Ni-1] as a catalyst for the dimerization of 1-butene, which produces a linear octene yield of 75-83% at reaction temperatures between 70-80 °C. We are the first to demonstrate that it is also possible to use allylic nickel complexes in combination with hfacac to produce linear octenes with a selectivity of 70% under very mild reaction conditions and at low catalyst concentrations. Additionally the catalyst can be formed simply by adding the activator hfacac to a solution of the allylic nickel complex. No complicated synthesis or purification is needed.
- Behr,Bayrak,Peitz,Stochniol,Maschmeyer
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p. 41372 - 41376
(2015/05/27)
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- Lewis Acid Enhanced Ethene Dimerization and Alkene Isomerization - ESI-MS Identification of the Catalytically Active Pyridyldimethoxybenzimidazole Nickel(II) Hydride Species
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A cationic methallyl 2-pyridine-4,7-dimethoxybenzimidazole (L1) nickel precatalyst is highly selective in ethene dimerizations to 1-butene. The same catalyst isomerizes 1-butene and 1-octene to internal olefins. Co-catalytic additives of B(C6F5)3 or BF3·OEt2 coordinate to the catalyst and increase the reaction rates of ethene dimerization. ESI-MS was applied identifying a [L1NiH]+ cation as the catalytically active species.
- Escobar, Manuel A.,Trofymchuk, Oleksandra S.,Rodriguez, Barbara E.,Lopez-Lira, Claudia,Tapia, Ricardo,Daniliuc, Constantin,Berke, Heinz,Nachtigall, Fabiane M.,Santos, Leonardo S.,Rojas, Rene S.
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p. 7338 - 7342
(2015/12/11)
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