- Ruthenium complex immobilized on supported ionic-liquid-phase (SILP) for alkoxycarbonylation of olefins with CO2
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In this study, the heterogeneously catalyzed alkoxycarbonylation of olefins with CO2based on a supported ionic-liquid-phase (SILP) strategy is reported for the first time. An [Ru]@SILP catalyst was accessed by immobilization of ruthenium complex on a SILP, wherein imidazolium chloride was chemically integrated at the surface or in the channels of the silica gel support. An active Ru site was generated through reacting Ru3(CO)12with the decorated imidazolium chloride in a proper microenvironment. Different IL films, by varying the functionality of the side chain at the imidazolium cation, were found to strongly affect the porosity, active Ru sites, and CO2adsorption capacity of [Ru]@SILP, thereby considerably influencing its catalytic performance. The optimized [Ru]@SILP-A-2 displayed enhanced catalytic performance and prominent substrate selectivity compared to an independent homogeneous system under identical conditions. These findings provide the basis for a novel design concept for achieving both efficient and stable catalysts in the coupling of CO2with olefins.
- Xia, Shi-Ping,Ding, Guang-Rong,Zhang, Rui,Han, Li-Jun,Xu, Bao-Hua,Zhang, Suo-Jiang
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p. 3073 - 3080
(2021/05/05)
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- Structural studies and applications of water soluble (phenoxy)imine palladium(II) complexes as catalysts in biphasic methoxycarbonylation of 1-hexene
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Reactions of the ligands; sodium 4?hydroxy-3-((phenylimino)methyl)benzenesulfonate (L1), sodium 3-(((2,6-dimethylphenyl)imino)methyl)-4-hydroxybenzenesulfonate (L2) and sodium 3-(2,6-diisopropylphenyl)imino)methyl)-4-hydroxybenzenesulfonate (L3) with Pd(OAc)2 afforded the respective palladium(II) complexes [Pd(L1)2] (PdL1), [Pd(L2)2] (PdL2) and [Pd(L3)2] (PdL3). In addition, treatment of the non-water soluble ligands 2-((phenylimino)methyl)phenol (L4), 2-(((2,6-dimethylphenyl)imino)methyl)phenol (L5) and 2-((2,6-diisopropylphenyl)imino)methyl)phenol (L6) with Pd(OAc)2 gave the corresponding complexes [Pd(L4)2] (PdL4), [Pd(L5)2] (PdL5) and [Pd(L6)2] (PdL6) in good yields. Solid state structures of complexes PdL1 and PdL4 established the formation of bis(chelated) square planar neutral compounds. All the complexes formed active catalysts in the methoxycarbonylation of 1-hexene, affording yields of up to 92% within 20 h and regioselectivity of 73% in favour of linear esters. The catalytic activity and selectivity of the complexes depended on the steric encumbrance around the coordination centre. The water soluble complexes displayed comparable catalytic behaviour to the non-water soluble systems. The complexes could be recycled five times with minimal changes in both the catalytic activities and regio-selectivity.
- Akiri, Saphan O.,Ojwach, Stephen O.
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- Sterically hindered (pyridyl)benzamidine palladium(II) complexes: Syntheses, structural studies, and applications as catalysts in the methoxycarbonylation of olefins
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Reactions of ligands (E)-N′-(2,6-diisopropylphenyl)-N-(4-methylpyridin-2-yl)benzimidamide (L1), (E)-N′-(2,6-diisopropylphenyl)-N-(6-methylpyridin-2-yl)benzimidamide (L2), (E)-N′-(2,6-dimethylphenyl)-N-(6-methylpyridin-2-yl)benzimidamide (L3), (E)-N′-(2,6-dimethylphenyl)-N-(4-methylpyridin-2-yl)benzimidamide (L4), and (E)-N-(6-methylpyridin-2-yl)-N′-phenylbenzimidamide (L5) with [Pd(NCMe)2Cl2] furnished the corresponding palladium(II) precatalysts (Pd1–Pd5), in good yields. Molecular structures of Pd2 and Pd3 revealed that the ligands coordinate in a N^N bidentate mode to afford square planar compounds. Activation of the palladium(II) complexes with para-tolyl sulfonic acid (PTSA) afforded active catalysts in the methoxycarbonylation of a number of alkene. The resultant catalytic activities were controlled by the both the complex structure and alkene substrate. While aliphatic substrates favored the formation of linear esters (>70%), styrene substrate resulted in the formation of predominantly branched esters of up to 91%.
- Akiri, Saphan O.,Ojwach, Stephen O.
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- Palladium(II) complexes of (pyridyl)imine ligands as catalysts for the methoxycarbonylation of olefins
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Reactions of 2-methoxy-N-((pyridin-2-yl)methylene)ethanamine (L1), 2-((pyridin-2-yl)methyleneamino)ethanol (L2) and 3-methoxy-N-((pyridin-2-yl)methylene)propan-1-amine (L3) ligands with either [PdCl2(COD)] or [PdCl(Me)(COD)] produced the corresponding monometallic complexes [PdCl2(L1)] (1), [PdClMe(L1)] (2), [PdCl2(L2)] (3) and [PdCl2(L3)] (4). The solid state structure of complex 1 confirmed the bidentate coordination mode of L1, giving a distorted square planar geometry. All the complexes (1–4) formed active catalysts for the methoxycarbonylation of higher olefins to give linear and branched esters. The catalytic behavior of complexes 1–4 were influenced by both the complex structure and olefin chain length.
- Zulu, Zethu,Nyamato, George S.,Tshabalala, Thandeka A.,Ojwach, Stephen O.
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- Method for preparing organic carboxylic ester through combined catalysis of aryl bidentate phosphine ligand
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The invention discloses a method for preparing organic carboxylic ester by combined catalysis of an aryl bidentate phosphine ligand. The method comprises the following steps: under the action of a palladium compound/aryl bidentate phosphine ligand/acidic additive combined catalyst, carrying out a hydrogen esterification reaction on terminal olefin, carbon monoxide and alcohol so as to generate theorganic carboxylic ester with one more carbon than olefin. According to the invention, by adoption of the palladium compound/aryl bidentate phosphine ligand/acidic additive combined catalyst, good catalytic activity and selectivity for the hydrogen esterification reaction of the olefin are achieved, and olefin carbonylation to synthesize organic carboxylic ester can be efficiently catalyzed. Thearyl bidentate phosphine ligand has a rigid skeleton structure of a rigid ligand and the flexibility of a flexible ligand, so the aryl bidentate phosphine ligand has proper flexibility due to the characteristic that the aryl bidentate phosphine ligand is soft and rigid, and a most favorable coordination mode and a stable active structure in space are favorably formed. In addition, the aryl bidentate phosphine ligand has the advantages of high stability, simple and convenient synthesis method and the like; and a novel industrial technology is provided for production of organic carboxylate compounds.
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Paragraph 0044
(2020/05/29)
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- Methoxycarbonylation of olefins catalysed by homogeneous palladium(II) complexes of (phenoxy)imine ligands bearing alkoxy silane groups
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The Schiff base compounds 2-phenyl-2-((3(triethoxysilyl)propyl)imino)ethanol (HL1) and 4-methyl-2-((3(triethoxysilyl)propyl)imino)methyl)phenol (HL2) were synthesized via condensation reactions of a suitable ketone or aldehyde and (3-aminopropyl) triethoxy silane (APTES). Whereas the reactions of HL1 and HL2 with [Pd(OAc)2] afforded the bis(chelated) palladium compounds [Pd(L1)2] (1) and [Pd(L2)2] (2), treatments of HL1 and HL2 with [Pd(NCMe)2Cl2] gave the mono(chelated) complexes [Pd(HL1)2Cl2] (3) and [Pd(HL2)2Cl2] (4) respectively. Structural characterization of the compounds was achieved using NMR and FT-IR spectroscopies, mass spectrometry and micro-analyses. Complexes 1–4 gave active catalysts in the methoxycarbonylation of higher olefins producing linear esters as the major products. The coordination environment around the palladium center of the complexes dictated the relative catalytic activity, where the bis(chelated) analogues 1 and 2 were more active than the mono(chelated) analogues 3 and 4. The nature of the acid promoter, phosphine groups, solvent system, olefin substrate and reactions conditions influenced the catalytic behaviour of the complexes.
- Akiri, Saphan O.,Ojwach, Stephen O.
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p. 236 - 243
(2019/03/02)
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- Alkoxycarbonylation of olefins with carbon dioxide by a reusable heterobimetallic ruthenium-cobalt catalytic system
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The heterobimetallic ruthenium-cobalt catalytic system exhibited good catalytic performance and reusability in the reductive alkoxycarbonylation of olefins with carbon dioxide. Compared to the previous system only consisting of ruthenium catalyst, the binary catalyst system effectively reduced the usage of noble metal and ionic liquid additives. The respective contribution of ruthenium and cobalt catalysts in this multiple-step catalytic process was investigated by a series of condition-controlled experiments. The evolution of the ruthenium catalyst and the occurrence of alkene hydrogenation during the reaction was explained by theortical calculations.
- Zhang, Xuehua,Shen, Chaoren,Xia, Chungu,Tian, Xinxin,He, Lin
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supporting information
p. 5533 - 5539
(2019/01/03)
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- Palladium(II) complexes bearing mixed N^N^X (X?=?O and S) tridentate ligands as pre-catalysts for the methoxycarbonylation of selected 1-alkenes
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The methoxycarbonylation of selected 1-alkenes catalyzed by various neutral and cationic palladium(II) complexes, containing mixed N^N^X (X = O and S) tridentate ligands 2-[(3,5-dimethyl-1H-pyrazol-1-yl)methyl]-6-(phenoxymethyl)pyridine (L1), 2-[(3,5-di-tert-butyl-1H-pyrazol-1-yl)methyl]-6-(phenoxymethyl)pyridine (L2), 2-[(3,5-dimethyl-1H-pyrazol-1-yl)methyl]-6-(phenylthiomethyl)pyridine (L3), 2-[(3,5-di-tert-butyl-1H-pyrazol-1-yl)methyl]-6-(phenylthiomethyl)pyridine (L4), has been investigated. Neutral complexes, [(?2-L1)Pd(CH3)(Cl)] (1a), [(?2-L2)Pd(CH3)(Cl)] (2a), [(?2-L3)Pd(CH3)(Cl)] (3a), [(?2-L4)Pd(CH3)(Cl)] (4a), and the salts, [(?3-L3)Pd(CH3)][BAr4F] (3c) and [(?3-L4)Pd(CH3)][BAr4F] (4c), underwent complete decomposition during the reaction to palladium black and showed no catalytic activity. However, the addition of PPh3 to the reaction dramatically increased the catalytic activity. On the other hand, the salts, [(?2-L1)Pd(CH3)(PPh3)][BAr4F] (1b), [(?2-L2)Pd(CH3)(PPh3)][BAr4F] (2b), [(?2-L3)Pd(CH3)(PPh3)][BAr4F] (3b) and [(?2-L4)Pd(CH3)(PPh3)][BAr4F] (4b), showed good conversion of the selected olefins to branched and linear esters without PPh3. Addition of PPh3 to reactions with 1b-4b significantly improved catalytic activity. All decomposition of complexes led to the formation of the known palladium complexes, [Pd(PPh3)2(Cl)(CH3)] and [Pd(PPh3)2Cl2]. The decomposition of all palladium complexes could be followed by NMR studies and [Pd(PPh3)2Cl2] could be isolated from the crude methoxycarbonylation reaction.
- Kumar, Kamlesh,Darkwa, James
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p. 249 - 257
(2017/10/27)
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- Palladium-Catalyzed Carbonylation of sec- and tert-Alcohols
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A general palladium-catalyzed synthesis of linear esters directly from sec- and tert-alcohols is described. Compared to the classic Koch–Haaf reaction, which leads to branched products, this new transformation gives the corresponding linear esters in high yields and selectivity. Key for this protocol is the use of an advanced palladium catalyst system with L2 (pytbpx) as the ligand. A variety of aliphatic and benzylic alcohols can be directly used and the catalyst efficiency for the benchmark reaction is outstanding (turnover number up to 89 000).
- Dong, Kaiwu,Sang, Rui,Liu, Jie,Razzaq, Rauf,Franke, Robert,Jackstell, Ralf,Beller, Matthias
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supporting information
p. 6203 - 6207
(2017/05/22)
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- Toward the development of efficient and stable Pd-catalysts for the methoxycarbonylation of medium chain alkenes
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Methoxycarbonylation provides a one-step synthesis to valuable ester products utilised in both the fine and heavy chemical industry. However, in general, reaction rates for longer chain alkenes are poor which renders industrial implementation economical unviable. In cases where suitable rates are achieved, the requisite reagents are costly and in addition, the catalyst complexes readily decompose at elevated temperatures. This paper describes the use of an alternative ligand structural motif for the efficient methoxycarbonylation of terminal and internal medium chain alkenes to their corresponding esters. Promising results were obtained using a catalyst complex generated in situ from an unsymmetrical diphosphine ligand based on a ferrocene backbone, Pd(OAc)2 and methane sulfonic acid.
- Bredenkamp, Tyler,Holzapfel, Cedric
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p. 421 - 427
(2016/01/27)
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- Branched Selectivity in the Pd-Catalysed Methoxycarbonylation of 1-Alkenes
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The methoxycarbonylation of alkenes by palladium(II) complexes with P,O-donor ligands [(2-methoxyphenyl)diphenylphosphine (L-2), bis(2-methoxyphenyl) phenyl phosphine (L-3) and tris(2-methoxyphenyl) phosphine (L-4)] has been investigated. The results show that the Pd complexes derived from these ligands provide high regioselectivity for the branched esters from 1-pentene and 1-hexene (>80 %). Various parameters (including temperature, pressure, acid concentration) were optimized to improve the performance of the catalyst system. Higher temperatures afforded higher regioselectivity; but effected rapid catalyst decomposition. Acceptable turnover frequencies, conversions as well as catalyst stability could be obtained at higher L/Pd ratios. The dramatic change in regioselectivity is rationalised on the basis of the hemi-lability of the o-methoxy moiety, which may lead to ligand dissociation from L2PdX2 (L=ligand, X=Cl) rather than the expected dissociation of X. In support of our hypothesis, direct evidence for the coordination of the o-methoxy to the Pd centre was demonstrated by the crystal structure. To the best of our knowledge, this work provides the first reported route to valuable branched esters through the methoxycarbonylation of alkenes at suitable rates.
- Arderne, Charmaine,Guzei, Llia A.,Holzapfel, Cedric W.,Bredenkamp, Tyler
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p. 1084 - 1093
(2016/04/05)
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- Palladium complexes of (benzoimidazol-2-ylmethyl)amine ligands as catalysts for methoxycarbonylation of olefins
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Reactions of N-(1H-benzoimidazol-2-ylmethyl)-2-methoxy aniline (L1) and N-(1H-benzoimidazol-2-ylmethyl)-2-bromo aniline (L2) with either [PdCl2(COD)] or [PdClMe(COD)] afforded the neutral palladium complexes [PdCl2(L1)] (1), [PdClMe(L1)] (2) and [PdClMe(L2] (3), respectively. Treatment of 2 and 3 with one equivalent of PPh3 in the presence of NaBAr4 (Ar = 3,5-(CF3)2C6H3) produced the corresponding cationic species, [PdMe(L1)]BAr4 (4) and [PdMe(L2)]BAr4 (5). All the palladium complexes formed active catalysts in the methoxycarbonylation of alkenes to produce linear and branched esters. The catalytic behaviour was dependent on the catalyst structure, presence of PPh3, acid promoter and alkene chain length.
- Tshabalala, Thandeka A.,Ojwach, Stephen O.,Akerman, Matthew A.
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p. 178 - 184
(2015/06/25)
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- Kinetics and mechanisms of homogeneous catalytic reactions. Part 12. Hydroalcoxycarbonylation of 1-hexene using palladium/triphenylphosphine systems as catalyst precursors
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Systems prepared in situ by addition of n equivalents of triphenylphosphine to palladium dichloride in the presence of m equivalents of para-toluenesulfonic acid (TSA), PdCl2/nPPh3/mTSA (n and m varying between 2 and 10), were used as precatalysts for the olefin carbonylation (1-hexene, cyclohexene and styrene) with alcohols (MeOH, EtOH, n-PrOH and i-PrOH) to generate the corresponding esters (hydroalcoxycarbonylation), under mild reaction conditions. For 1-hexene carbonylation in presence of methanol (1-hexene hydromethoxycarbonylation), the most active system was PdCl2/6PPh3/5TSA at P(CO) = 50 atm and T = 125°C, which was also active for the hydromethoxycarbonylation of other olefins (1-hexene > styrene > cyclohexene). This system was regioselective towards the linear product for 1-hexene and towards the branched product for styrene. A kinetic study of 1-hexene hydromethoxycarbonylation catalyzed by PdCl2/6PPh3/5TSA showed that the initial reaction rate (ro) was first order on Pd and MeOH concentrations and fractional order with respect to CO concentration; for olefin concentration was found a saturation curve. These kinetic results, together with coordination chemistry and computational DFT studies, allow us to propose a catalytic cycle involving species of the type [Pd(H)(L)(PPh3)2]+n (L = Cl, n = 0; L = CO, MeOH, olefin and PPh3, n = 1) as the catalytically active species and three sequential reactions: (1) olefin insertion into the Pd-H bond to yield Pd-alkyl species, (2) CO insertion into the Pd-C bond to generate Pd-acyl intermediates, and (3) the methanolysis of Pd-acyl species to produce the corresponding methyl esters, regenerate the active species and restart the cycle; the last reaction is considered the rate-determining step (rds) of the mechanism.
- Rosales, Merln,Pacheco, Ins,Medina, Jairo,Fernndez, Juan,Gonzlez, ngel,Izquierdo, Rodolfo,Melean, Luis G.,Baricelli, Pablo J.
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p. 1717 - 1727
(2015/02/19)
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- Methoxycarbonylation of olefins catalyzed by palladium complexes bearing P,N-donor ligands
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The methoxycarbonylation of alkenes catalyzed by palladium(ii) complexes with P,N-donor ligands, 2-(diphenylphosphinoamino)pyridine (Ph 2PNHpy), 2-[(diphenylphosphino)methyl]pyridine (Ph 2PCH2py), and 2-(diphenylphosphino)quinoline (Ph 2Pqn) has been investigated. The results show that the complex [PdCl(PPh3)(Ph2PNHpy)]Cl or an equimolar mixture of [PdCl2(Ph2PNHpy)] and PPh3, in the presence of p-toluensulfonic acid (TsOH), is an efficient catalyst for this reaction. This catalytic system promotes the conversion of styrene into methyl 2-phenylpropanoate and methyl 3-phenylpropanoate with nearly complete chemoselectivity, 98% regioselectivity in the branched isomer, and high turnover frequency, even at alkene/Pd molar ratios of 1000. Best results were obtained in toluene-MeOH (3: 1) solvent. The Pd/Ph2PNHpy catalyst is also efficient in the methoxycarbonylation of cyclohexene and 1-hexene, although with lower rates than with styrene. Related palladium complexes [PdCl(PPh 3)L]Cl (L = Ph2PCH2py and Ph2Pqn) show lower activity in the methoxycarbonylation of styrene than that of the 2-(diphenylphosphinoamino)pyridine ligand. Replacement of the last ligand by (diphenylphosphino)phenylamine (Ph2PNHPh) or 2- (diphenylphosphinoaminomethyl)pyridine (Ph2PNMepy) also reduces significantly the activity of the catalyst, indicating that both the presence of the pyridine fragment as well as the NH group, are required to achieve a high performing catalyst. Isotopic labeling experiments using MeOD are consistent with a hydride mechanism for the [PdCl(PPh3)(Ph2PNHpy)]Cl catalyst. The Royal Society of Chemistry.
- Aguirre, Pedro A.,Lagos, Carolina A.,Moya, Sergio A.,Zuniga, Cesar,Vera-Oyarce, Cristian,Sola, Eduardo,Peris, Gabriel,Bayon, J. Carles
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p. 5419 - 5426
(2008/09/17)
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- Hydroesterification Reactions with Palladium-Complexed PAMAM Dendrimers Immobilized on Silica
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Highly active, recyclable catalytic systems for the hydroesterification reaction of olefins with methanol and carbon monoxide were prepared by complexing various palladium species to generation zero through four PAMAM dendrimers immobilized on silica. The silica-dendrimer-Pd(PPh3) 2 complexes were the most facile recyclable catalysts and could be recycled four to six times by filtration under air. These catalysts show selectivity for the linear reaction product.
- Reynhardt, Jan P. K.,Alper, Howard
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p. 8353 - 8360
(2007/10/03)
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- Dirhodium(II) tetrakis(perfluoroalkylbenzoates) as partially recyclable catalysts for carbene transfer reactions with diazoacetates
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Three highly fluorinated dirhodium(II) tetrakis(benzoates), [Rh2(O2CRF)4, RF=C6H4-4-C6F13 (3) and C6H3-3,5-di(CnF2n+1) (n=6: 4; n=8: 5)], have been prepared and characterized. Only 4 and 5 are suited for applications in fluorous synthesis due to their excellent solubility in fluorous solvents. They were found to catalyze the following carbenoid reactions of diazo compounds in the fluorous solvents 1,1,2-trichloro-1,2,2-trifluoroethane and perfluoro(methylcyclohexane): cyclopropanation of styrenes using methyl diazoacetate, intermolecular carbene C-H insertion into hexane with methyl diazoacetate, and intramolecular aromatic C-H insertion of an α-diazo-β-ketoester. Except for the second reaction type, the catalyst could be recovered to a high extent by a liquid-liquid extraction (fluorous solvent - dichloromethane) due to its preference for the fluorous solvent. For the cyclopropanation reactions, the recovered catalyst was used in four subsequent reaction/workup cycles without significant loss of activity. In contrast, the catalyst could not be recovered from the carbenoid C-H insertion reaction with hexane; apparently, some by-products of this sluggish reaction, such as carbene dimers and oligomers, caused the deactivation or destruction of the catalyst.
- Endres, Andreas,Maas, Gerhard
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p. 3999 - 4005
(2007/10/03)
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- HYDROFORMYLATION OF OLEFINS WITH PARAFORMALDEHYDE CATALYZED BY RHODIUM COMPLEXES
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The addition of formaldehyde to olefins is efficiently catalyzed by RhH2(O2COH)2 and gives the corresponding aldehydes in neutral solution.
- Okano, Tamon,Kobayashi, Teruyuki,Konishi, Hisatoshi,Kiji, Jitsuo
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p. 4967 - 4968
(2007/10/02)
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