- Modular Attachment of Appended Boron Lewis Acids to a Ruthenium Pincer Catalyst: Metal-Ligand Cooperativity Enables Selective Alkyne Hydrogenation
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A new series of bifunctional Ru complexes with pendent Lewis acidic boranes were prepared by late-stage modification of an active hydrogen-transfer catalyst. The appended boranes modulate the reactivity of a metal hydride as well as catalytic hydrogenations. After installing acidic auxiliary groups, the complexes become multifunctional and catalyze the cis-selective hydrogenation of alkynes with higher rates, conversions, and selectivities compared with the unmodified catalyst.
- Tseng, Kuei-Nin T.,Kampf, Jeff W.,Szymczak, Nathaniel K.
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supporting information
p. 10378 - 10381
(2016/09/04)
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- η1-Allylpalladium complexes with a tridentate PNP ligand with different phosphino groups
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The iminodiphosphine 2-(PPh2)C6H4-1- CHNC6H4-2-(PPh2) (P-N-P′) is used for the preparation of the complexes [Pd(η1-CHR1-CHCR 2R3)(P-N-P′)]BF4 [R1 = R 2 = R3 = H: (1); R1 = R2 = Ph, R3 = H: (2); R1 = R3 = H, R2 = Ph: (3); R1 = H, R2 = R3 = Me: (4)]. The P-N-P′ tridentate coordination and the η1-allyl bonding mode in the solid are confirmed by the X-ray structural analysis of 1. In solution, the complexes 1 and 2 undergo an η1-η3- η1 rearrangement at 298 K interconverting the bonding site of the allyl group. A five-coordinate structure with the phosphine ligands in the axial position is proposed for the η3-allyl intermediate. For the dynamic process, a ΔG≠ value of 53.8 kJ mol-1 is obtained from 1H NMR data of 2. In 3 and 4, the allyl ligand is rigidly bound to the metal through the less substituted terminus, in line with the higher free energy content of the corresponding isomers: [Pd(η1-CHPh-CHCH2)(P-N-P′)]+ +48.78 kJ mol-1; [Pd(η1-CMe2-CHCH 2)(P-N-P′)]+ +69.35 kJ mol-1. The complexes react with secondary amines in the presence of fumaronitrile at different rates yielding allylamines and the palladium(0) derivative [Pd(η2-fn)(P-N-P′)] (5). On the basis of charge distribution on the allylic carbon atoms and of steric factors, the difference in rate and the regioselectivity in the amination of 1-3 are better rationalized by a mechanism with nucleophilic attack at the η3-intermediate rather than by an SN2 mechanism with nucleophilic attack at the Pd-CHR1 carbon atom. The high regioselectivity in the reaction of 4 with piperidine implies an SN2′ mechanism with nucleophilic attack at the CMe2 allyl carbon. A dynamic process occurs also for the 18-electron complex 5 consisting in a dissociation-association equilibrium of the olefin.
- Crociani, Bruno,Antonaroli, Simonetta,Paoli, Paola,Rossi, Patrizia
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p. 12490 - 12500
(2013/01/14)
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- η1-Allylpalladium complexes with a tridentate PNP ligand with different phosphino groups
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The iminodiphosphine 2-(PPh2)C6H4-1- CHNC6H4-2-(PPh2) (P-N-P′) is used for the preparation of the complexes [Pd(η1-CHR1-CHCR 2R3)(P-N-P′)]BF4 [R1 = R 2 = R3 = H: (1); R1 = R2 = Ph, R3 = H: (2); R1 = R3 = H, R2 = Ph: (3); R1 = H, R2 = R3 = Me: (4)]. The P-N-P′ tridentate coordination and the η1-allyl bonding mode in the solid are confirmed by the X-ray structural analysis of 1. In solution, the complexes 1 and 2 undergo an η1-η3- η1 rearrangement at 298 K interconverting the bonding site of the allyl group. A five-coordinate structure with the phosphine ligands in the axial position is proposed for the η3-allyl intermediate. For the dynamic process, a ΔG≠ value of 53.8 kJ mol-1 is obtained from 1H NMR data of 2. In 3 and 4, the allyl ligand is rigidly bound to the metal through the less substituted terminus, in line with the higher free energy content of the corresponding isomers: [Pd(η1-CHPh-CHCH2)(P-N-P′)]+ +48.78 kJ mol-1; [Pd(η1-CMe2-CHCH 2)(P-N-P′)]+ +69.35 kJ mol-1. The complexes react with secondary amines in the presence of fumaronitrile at different rates yielding allylamines and the palladium(0) derivative [Pd(η2-fn)(P-N-P′)] (5). On the basis of charge distribution on the allylic carbon atoms and of steric factors, the difference in rate and the regioselectivity in the amination of 1-3 are better rationalized by a mechanism with nucleophilic attack at the η3-intermediate rather than by an SN2 mechanism with nucleophilic attack at the Pd-CHR1 carbon atom. The high regioselectivity in the reaction of 4 with piperidine implies an SN2′ mechanism with nucleophilic attack at the CMe2 allyl carbon. A dynamic process occurs also for the 18-electron complex 5 consisting in a dissociation-association equilibrium of the olefin.
- Crociani, Bruno,Antonaroli, Simonetta,Paoli, Paola,Rossi, Patrizia
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p. 12490 - 12500,11
(2012/12/13)
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- Impact of cyclodextrins on the behavior of amphiphilic ligands in aqueous organometallic catalysis
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In this study, we showed that the addition of randomly modified β-cyclodextrin (RAME-β-CD) in aqueous medium could have a beneficial impact on the catalytic performances of phosphane-based aggregates in the Pd-catalyzed cleavage of allyl carbonates (Tsuji-Trost reaction). The RAME-β-CD/phosphane supramolecular interactions helped explain the catalytic results. The presence of RAME-β-CD in the aqueous compartment improved the phosphane-based aggregate dynamics. The exchanges between the hydrophobic substrate-containing aggregate core and the catalyst-containing aqueous phase were then greatly favored, resulting in an increase in the catalytic performances.
- Bricout, Herve,Leonard, Estelle,Len, Christophe,Landy, David,Hapiot, Frederic,Monflier, Eric
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supporting information
p. 1479 - 1484
(2012/11/13)
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- Scope and limitation of activated carbons in aqueous organometallic catalysis
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The effect of activated carbons has been studied in the palladium-catalyzed cleavage reaction of allylalkylcarbonate under aqueous biphasic conditions. A number of parameters were investigated, such as the type of carbon, the structure of the water-soluble ligand, the water conditions, and the metal complex loading. It was found that the intrinsic properties of carbons had a strong influence on the reaction rates. The best performances were obtained with the AC-WV carbon possessing the largest part of mesopores and lowest content of oxygen-surface groups. The results were rationalized by considering that AC-WV acted as a mass-transfer promoter increasing the interfacial area and collisions between the reactive species in the pore volume. The hypothesis of a confinement effect of the catalyst and reactants within the pores via adsorption-desorption processes was supported by isothermal studies and 31P{1H} NMR investigations.
- Kania, Nicolas,Gokulakrishnan, Narasimhan,Leger, Bastien,Fourmentin, Sophie,Monflier, Eric,Ponchel, Anne
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scheme or table
p. 208 - 218
(2011/04/21)
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- Amphiphilic photo-isomerisable phosphanes for aqueous organometallic catalysis
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Water-soluble phosphanes were tagged with a light-responding diazo group. Upon UV exposure, the diazo-isomerisation led to phosphane morphology change, resulting in an increase in the reaction rate of an aqueous palladium-catalysed cleavage reaction. The Royal Society of Chemistry.
- Bricout, Herve,Banaszak, Estelle,Len, Christophe,Hapiot, Frederic,Monflier, Eric
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supporting information; experimental part
p. 7813 - 7815
(2010/11/18)
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- Ditopic cyclodextrin-based receptors: New perspectives in aqueous organometallic catalysis
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The mass transfer properties of mono- and ditopic β-cyclodextrin-based receptors have been evaluated in a biphasic palladium-catalyzed Tsuji-Trost reaction and compared to one of the best mass-transfer promoters, namely the randomly methylated β-cyclodextrin. While monotopic receptors appeared to be poor mass-transfer promoters of long alkyl chain allyl carbonates or urethanes, cooperative effects have been evidenced with ditopic cyclodextrin-based receptors, opening new perspectives in aqueous organometallic catalysis.
- Six, Natacha,Menuel, Stephane,Bricout, Herve,Hapiot, Frederic,Monflier, Eric
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experimental part
p. 1467 - 1475
(2010/08/19)
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- Biphasic aqueous organometallic catalysis promoted by cyclodextrins: How to design the water-soluble phenylphosphane to avoid interaction with cyclodextrin
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The ability of cyclodextrin to interact with meta-trisulfonated triphenylphosphane derivatives bearing one or two methyl (or methoxy) groups on the aromatic ring has been investigated by NMR and UV-vis spectroscopy. In the case of native β-cyclodextrin (β-CD), the presence of one methyl or methoxy group in the ortho-position on each aromatic ring is necessary to hamper the formation of an inclusion complex between the β-CD and meta-trisulfonated triphenylphosphane derivatives. In the case of methylated β-CD, the formation of an inclusion complex is only observed when the meta-trisulfonated triphenylphosphane contains a methyl group in the para-position. The poor affinity of methylated β-CD towards modified trisulfonated triphenylphosphanes was attributed to the steric hindrance generated by the methyl groups on the CD secondary face. The absence or presence of an interaction between phosphanes and methylated β-CD was also confirmed by catalytic experiments. Thus, the phosphanes that do not interact with the methylated CD were the most efficient mass-transfer promoters in an aqueous biphasic palladium-catalyzed Tsuji-Trost reaction.
- Ferreira, Michel,Bricout, Herve,Sayede, Adlane,Ponchel, Anne,Fourmentin, Sophie,Tilloy, Sebastien,Monflier, Eric
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experimental part
p. 609 - 618
(2009/04/21)
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- Substrate-selective aqueous organometallic catalysis. How size and chemical modification of cyclodextrin influence the substrate selectivity
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Randomly hydroxypropylated and methylated cyclodextrins with different cavity size have been used as inverse phase transfer catalysts in a palladium catalyzed Tsuji-Trost reaction with water-insoluble alkylallylcarbonates and alkylallylurethanes as substrate. It has been shown that the molecular recognition ability of both α-CD and β-CD derivatives towards these substrates was responsible for an increase in the reaction rates and remarkable substrate selectivities between a linear and a branched structure. By contrast, the too wide cavity of γ-CD derivatives did not allow these carriers to be efficient in terms of substrate selectivity. Thus, the performances of a cyclodextrin carrier in this cleavage reaction strongly depended on the size of the cavity in which the substrate had to fill in as close as possible the available space.
- Torque, Christophe,Bricout, Hervé,Hapiot, Frédéric,Monflier, Eric
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p. 6487 - 6493
(2007/10/03)
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- Convenient synthesis of new amphiphilic triphenylphosphine analogues for aqueous biphasic catalysis
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The synthesis of three triphenylphosphine analogues with phenyl groups replaced by (4-tert-butyl)phenyl and (3-sulfonato)phenyl group is described. The surface-active properties of these new compounds are reported. The catalytic activities obtained with these phosphines in the palladium-catalyzed cleavage of undecyl allyl carbonate were up to 24000 times higher than those observed with trisulfonated triphenylphosphine, the ligand typically used in biphasic catalysis. One of these catalysts can be recovered six times without loss of catalytic activity.
- Caron, Laurent,Canipelle, Micha?l,Tilloy, Sébastien,Bricout, Hervé,Monflier, Eric
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p. 8837 - 8840
(2007/10/03)
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- Chemically modified β-cyclodextrins as supramolecular carriers in the biphasic palladium-catalyzed cleavage of allylic carbonates: Activity enhancement and substrate-selective catalysis
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Catalytic amounts of chemically modified β-cyclodextrins allowed us to achieve, in high yields, the deprotection of various water-insoluble allylic carbonates in a genuine two-phase system without co-solvent. The catalytic activities were up to 300 times higher than those observed without modified cyclodextrins, The process of molecular recognition between the cyclodextrin and the substrate allowed us to perform substrate-selective catalytic reactions which cannot be achieved in homogeneous or biphasic media with conventional transition metal catalysts.
- Lacroix, Thibaut,Bricout, Herve,Tilloy, Sebastien,Monflier, Eric
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p. 3127 - 3129
(2007/10/03)
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- Synthetic and kinetic aspects of nickel-catalysed amination of allylic alcohol derivatives
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The design of efficient nickel-based catalytic systems for coupling of diethylamine (1) with esters and ether derivatives of allyl alcohol (2a-c) and related allyl-substituted compounds (4a-e) is reported. Special attention is paid to solvent and salt effects on catalytic activities and kinetic profiles for the formation of allyllamines. The results are discussed in terms of the influence of some reaction parameters (polarity, ion exchange processes, substrate) on the rate determining step of the catalytic cycle.
- Bricout, Herve,Carpentier, Jean-Francois,Mortreux, Andre
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p. 1073 - 1084
(2007/10/03)
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- INVESTIGATIONS IN THE REGION OF AMINES AND AMMONIUM COMPOUNDS. CLXXVII. "REARANGEMENT-CLEAVAGE" OF DIALKYLALLYLPROPARGYLAMMONIUM SALTS IN THE PRESENCE OF A PRIMARY AMINE
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Under the influence of a primary amine with heat both in the presence and in the absence of alkali dialkylallylammonium salts containing a group of the propargyl type form the imines of α-substituted 4-pentenal.
- Grigoryan, Dzh. V.,Galoyan, A. M.,Babayan, A. T.
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p. 2098 - 2101
(2007/10/02)
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