Water-soluble Rhodium Catalyst Research Articles

Parahydrogen-Induced Polarization of 1-13C-Acetates and 1-13C-Pyruvates Using Sidearm Hydrogenation of Vinyl, Allyl, and Propargyl Esters.

13C-hyperpolarized carboxylates, such as pyruvate and acetate, are emerging molecular contrast agents for MRI visualization of various diseases, including cancer. Here we present a systematic study of 1H and 13C parahydrogen-induced polarization of acetate and pyruvate esters with ethyl, propyl and allyl alcoholic moieties. It was found that allyl pyruvate is the most efficiently hyperpolarized compound from those under study, yielding 21% and 5.4% polarization of 1H and 13C nuclei, respectively, in CD3OD solutions. Allyl pyruvate and ethyl acetate were also hyperpolarized in aqueous phase using homogeneous hydrogenation with parahydrogen over water-soluble rhodium catalyst. 13C polarization of 0.82% and 2.1% was obtained for allyl pyruvate and ethyl acetate, respectively. 13C-hyperpolarized methanolic and aqueous solutions of allyl pyruvate and ethyl acetate were employed for in vitro MRI visualization, demonstrating the prospects for translation of the presented approach to biomedical in vivo studies.

Photo induced alkyne hydration reactions mediated by a water soluble, reusable Rhodium (I) catalyst

Under photochemical irradiation, the hydration of aryl alkynes in the presence of water proceeds in good yields to afford the corresponding ketone, using a water-soluble rhodium (I) catalyst. The catalyst is effective for internal and terminal alkynes and showed high functional group compatibility. A low catalyst loading, low temperature and shorter duration of photolysis are ideal feature of reaction. The catalyst can be reused several times under aerobic and aqueous conditions, exemplifying the robust nature of the catalyst. In comparison with known Rh and other metal catalysts, the present reaction provides a remarkable green approach for alkyne hydration reactions.

Hydroformylation of 1‐Dodecene with Water‐Soluble Rhodium Catalysts with Bidentate Ligands in Multiphase Systems

AbstractA hydrophilic metal–ligand complex formed from the precursor [dicarbonyl(acetylacetonato)rhodium(I)] {[Rh(acac)(CO)2]} and the bidentate ligand [2,7‐bis(SO3Na)‐4,5‐bis(diphenylphosphino)‐9,9‐dimethylxanthene] (SulfoXantPhos), was found to be a suitable candidate as a catalyst complex for the hydroformylation of 1‐dodecene in multiphase systems formulated from water, 1‐dodecene, and a nonionic surfactant. To improve the solubilization of the olefin in the aqueous phase, surfactants were added. The multiphase system acted as a tunable solvent, through which not only the interfacial area was increased during the reaction but also the phase separation behavior could be manipulated through temperature changes, thus allowing an easy separation of the expensive rhodium complex from the organic phase after the reaction. The influence of different process parameters such as the type of surfactant, type of ligand, and the metal/ligand ratio was investigated and discussed. Also the influence of the phase state on the reaction was determined. Under optimized reaction conditions, turnover frequencies of >300 h−1 and selectivities of 98:2 towards the linear product could be achieved.

Organic solvent-free hydrogenation of natural rubber latex and synthetic polyisoprene emulsion catalyzed by water-soluble rhodium complexes

A water-soluble rhodium catalyst has been found to be an efficient catalyst for hydrogenation of unsaturated polymers in the absence of any organic solvent. Natural rubber (NR) latex and synthetic polyisoprene (PIP) emulsion were hydrogenated using rhodium trichloride (RhCl3·3H2O) and different ligand types, triphenylphosphine (PPh3), trisulfonated triphenylphosphine (TPPTS) and monosulfonated triphenylphosphine (TPPMS) as a catalyst precursor. The hydrogenated NR and PIP were characterized by proton nuclear magnetic resonance (1H NMR). A low degree of hydrogenation (HD) was observed when using RhCl3/PPh3 or RhCl3/TPPTS. In contrast, a high HD of 85.8% was achieved by using RhCl3/TPPMS. The catalytic behavior could be well explained by the Hartley ionic spherical micelle model. The HD increased with increasing catalyst amount, reaction temperature and H2 pressure. The catalyst activity of RhCl3/TPPMS for NR hydrogenation was found to be lower than that for PIP hydrogenation for all conditions due to impurities in the latex, including protein. The hydrogenated NR (86%HD) has high thermal stability with a maximum decomposition temperature of 466°C and a glass transition temperature of −60°C. From dynamic mechanical analysis, hydrogenated NR had a maximum storage modulus due to the saturated carbon domains of the ethylene–propylene segments in the polymer chains.

Use of ordered mesoporous materials as tools for organic and bioorganic synthesis

Ordered mesoporous materials are materials with well defined pore sizes in the range of 2 to 50 nm. This paper shows that suspensions of particles of mesoporous materials can be useful tools for organic and bioorganic synthesis. They can be used to overcome reactant incompatibility, as is demonstrated for a reaction between 4-tert-butylbenzyl bromide and KI. The pores are impregnated with an aqueous solution of KI and the lipophilic reactant is present in the continuous apolar phase. The reaction occurs at the pore openings. The pores of the mesoporous material can also be used as host for a homogeneous catalyst. The catalyst-loaded particles are kept as a suspension in a medium that contains the reactants. This principle is demonstrated for a Heck-type reaction with a water-soluble rhodium catalyst inserted into the pores of mesoporous silica. It is also shown to work well for a 1,4-conjugate addition between two water-soluble reactants, 4-carboxyphenylboronic acid and methyl acrylate, in which case a toluene-soluble rhodium catalyst was entrapped in the pores of hydrophobized mesoporous silica. The same principle was also used for biocatalysis. Lipase was inserted into either hydrophilic or hydrophobic pores and used for both ester synthesis and ester hydrolysis. Finally, palladium nanoparticles were deposited inside the pores of mesoporous carbon and used as catalyst for a Sonogashira reaction.

Hydroaminomethylation of high alkenes with dual-metal catalysts in aqueous/organic biphasic system

The water-soluble rhodium and iridium dual metal catalysts, RhCl(CO)(TPPTS)2 and IrCl(CO)(TPPTS)2 (TPPTS: P(m-C6H4SO3Na)3), were used in the hydroaminomethylation of high alkenes in aqueous/organic two-phase system in the presence of the cationic surfactant cetyltrimethylammonium bromide (CTAB). Higher activity and especially better chemoselectivity for amine were achieved under milder conditions compared with the sole use of rhodium or iridium catalyst. The combination of rhodium and iridium complexes accelerated the hydroaminomethylation, while excess of iridium complexes led to a decrease of reactivity.

Asymmetric transfer hydrogenation of ketones and imines with novel water-soluble chiral diamine as ligand in neat water

A novel water-soluble rhodium(III)catalyst prepared from o,o′-aminated N-tosyl-1,2-diphenylethylenediamine(S,S)-3 and [Cp*RhCl2]2, which was efficient for the asymmetric transfer hydrogenation of ketones and imines in neat water with high reactivity and excellent enantioselectivity, has been developed.

A carbon–carbon coupling reaction catalyzed by a water soluble rhodium catalyst entrapped in mesoporous silica

A Heck-type reaction, comprising a carbon–carbon coupling between an arylboronic acid and styrene, has been performed using a water soluble rhodium catalyst entrapped in the water-filled pores of mesoporous silica particles. The catalyst-loaded inorganic particles were dispersed in a non-polar medium, either a solution of the reactants in an aromatic solvent (toluene or p-xylene) or a solvent-free mixture of the reactants using a large excess of styrene. The reaction occurred at the oil–water interface, i.e., at the silica pore openings. The yield obtained was higher than that obtained in the conventional liquid–liquid two-phase system. The major advantage with having the catalyst “heterogenized” by entrapment into the siliceous material is the simplicity of the work-up process. The porous particles, containing the catalyst, are simply removed by filtration after completed reaction.

Higher olefin hydroformylation in organic/aqueous biphasic system accelerated by double long-chain cationic surfactants

The double long-chain cationic surfactants (DLCS) were used in higher olefin hydroformylation catalyzed by water-soluble rhodium catalyst in aqueous/organic biphasic system. The reaction rate was greatly accelerated and the value of TOF (turn over frequency defined as the moles of converted olefin per mole Rh per hour) in 1-dodecene hydroformylation could achieve 2291 h −1 even without stirring. When the reaction was carried out with stirring rate of 400 rpm, TOF increased to 7472 h −1. These values of TOF were comparable with that in homogeneous catalysis system. The phenomenon is attributed to the formation of vesicle and the enrichment of rhodium catalyst in the interfacial layer, as well as the high transfer rate of olefins from the organic phase to the interface of vesicle. The acceleration mechanism of DLCS in biphasic catalysis was discussed.

Mass-Transfer Effects in the Biphasic Hydroformylation of Propylene

The hydroformylation of propylene to butyraldehyde is an important industrial process. In this reaction system, carbon monoxide, hydrogen, and propylene are converted to n-butyraldehyde in an aqueous phase containing a water-soluble rhodium catalyst. This reaction system consists therefore of three different phases: the aqueous catalyst phase, the organic butyraldehyde phase, and the gas phase. A modeling study indicated that an optimum value of the production rate is reached at a certain power input. It was shown that mass transfer plays an important role in this reaction system and that accurate knowledge of the mass-transfer parameters in the gas-liquid-liquid system is necessary to predict and to optimize the production rate. Mass-transfer experiments with CO, H 2 , and propylene in water and in solutions consisting of water with different amounts of n-butyraldehyde were carried out in a stirred autoclave. The results indicated that the addition of small amounts of butyraldehyde caused a relatively small increase increase in k L a, which was probably caused by a larger increase of the gas-liquid interfacial area, a, accompanied by a decrease in the mass-transfer coefficient, k L . Near the point of maximum solubility of butyraldehyde, a strong (factor of 3) increase in k L a was observed. The most logical explanation for this is an increase in k L , because measurement of the interfacial area did not show such an increase. This increase in k L , i.e., the disappearance of the initial decrease, might be due to the disappearance of the rigid layer of butyraldehyde molecules at the gas-liquid interface by formation and spreading of a butyraldehyde layer around the bubble.

Rhodium‐Catalyzed [5 + 2] Cycloaddition Reactions in Water.

AbstractFor Abstract see ChemInform Abstract in Full Text.

Rhodium-Catalyzed [5+2] Cycloaddition Reactions in Water

A new water-soluble rhodium catalyst is reported along with its ability to effect [5+2] cycloaddition reactions in water. This water-soluble catalyst is recyclable, is readily separated from the or ganic product, and allows one to avoid or minimize the use of or ganic solvents, the major waste stream of most organic reactions.

The Hydroformylation Reaction

AbstractFor Abstract see ChemInform Abstract in Full Text.

Hydroformylation of 7-tetradecene using Rh-TPPTS in a microemulsion

Water soluble rhodium catalyst complexes are highly active in a microemulsion system stabilized by technical grade surfactants of the alkyl-polyglycolether type. At temperatures around 120 °C and pressures of 100 bar internal alkenes are hydroformylated with high regioselectivity. 7-Tetradecene as model alkene was effectively hydroformylated in microemulsions with high reaction rates yielding 2-hexyl-nonal. Under the reaction conditions applied the equilibria between different catalytically active complexes are shifted towards the unmodified HRh(CO) 3. Easy catalyst recycling of the water soluble modified complex is possible when the equilibrium is shifted back under work-up conditions.

Effect of reaction engineering factors on biphasic hydroformylation of 1-dodecene catalyzed by water-soluble rhodium complex

Hydroformylation of 1-dodecene in a biphasic system using water-soluble rhodium catalyst RhCl(CO)(TPPTS) 2 [TPPTS: tri(sodium- m-sulfonatophenyl) phosphine] was investigated. The cationic surfactant cetyltrimethyl ammonium bromide (CTAB) was used to enhance the reaction rate of long chain olefin and the ratio of normal/isomeric aldehyde. Experiments were carried out semi-batchwise in a 500 ml stirred autoclave at 100 °C and 1.1 MPa. An orthogonal experimental design was adopted for analyzing the effects of agitation intensity, 1-dodecene concentration, surfactant concentration and organic/water volume ratio on the macro-kinetics and regioselectivity. Several agitation configurations for improving the mixing, dispersion and interphase mass transfer of this gas–liquid–liquid reaction system were tested and higher hydroformylation rate and regioselectivity were achieved. The relationship between the extent of emulsification of reaction mixture and the performance of hydroformylation reaction was also studied. Empirical macro-kinetic equations for the initial rate and the correlation of normal/isomeric aldehyde ratio are proposed, which represented the experimental data reasonably well.

Transient operation of a catalytic liquid–liquid plug flow reactor for kinetics measurements

A centrifugal partition chromatograph (CPC) was used as a liquid–liquid catalytic reactor for the isomerisation of hexen-3-ol into ethylpropylketone with a water soluble rhodium catalyst. Global mass transfer coefficients were measured and shown to depend on both the nature of the solute and the flow rate. Liquid–liquid partition isotherms were also determined with the CPC using elution chromatography. Finally, a reactor model was derived to account for the experimental results obtained both under stationary and transient (pulse) conditions. A parameter sensitivity evaluation is also presented.

Hydroformylation of 1-dodecene using Rh-TPPTS in a microemulsion

Biphasic hydroformylation using water-soluble rhodium catalysts is advantageous with regard to catalyst recovery and product separation. Higher olefins cannot be converted due to their immiscibility with water. The 1-dodecene as model alkene was successfully hydroformylated in microemulsions with reaction rates higher than in a two-phase system. Technical grade polyglycolether type surfactants were used for the preparation of the microemulsions. Suitable microemulsions were found for carrying out hydroformylation reactions at different temperatures. Catalyst recovery can be achieved by phase separation followed by ultrafiltration.

Indication of water in the coordination sphere of rhodium by conversions of 2,5-dimethoxy-2,5-dihydrofuran with syngas

2,5-Dimethoxy-2,5-dihydrofuran did not form the expected aldehydes when water-soluble rhodium-catalysts were used for the conversion with syngas. Instead of hydroformylation, hydrogenation was the main reaction path in water, where 2,5-dimethoxytetrahydrofuran and its hydrolysis product, succinic dialdehyde, were obtained. The formation of hydrogenation products indicates water in the coordination sphere of rhodium. This may provide us with information on the environment of an active metal in aggregated structures like micelles and vesicles which are gaining in importance in biphasic catalysis.

ChemInform Abstract: Highly Enantioselective Hydrogenation of Enamides and Itaconic Acid in Water in the Presence of Water‐Soluble Rhodium(I) Catalyst and Sodium Dodecyl Sulfate.

AbstractChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.

Highly Enantioselective Hydrogenation of Enamides and Itaconic Acid in Water in the Presence of Water-Soluble Rhodium(I) Catalyst and Sodium Dodecyl Sulfate

The water-soluble cationic Rh complexes, such as [Rh(α-d-glucopyranosyl-(1,1)-2,3-di-O-(diphenylphosphino)-α-d-glucopyranoside)(cod)]BF4 (1) and [Rh(β-d-glucopyranosyl-(1,1)-2,3-di-O-(diphenylphosphino)-β-d-glucopyranoside)(cod)]BF4 (2) bearing free hydroxy groups, are effective catalysts in the asymmetric hydrogenation of various enamides and itaconic acid (up to 99.9% ee) in water in the presence of sodium dodecyl sulfate (SDS) (7.5 × 10-3 to 1.0 × 10-1 M). The hydrogenation of methyl (Z)-α-acetamidocinnamate in water using the corresponding Rh complexes of triflate (6) and d-camphor-10-sulfonate (7), prepared separately, results in a formation of the product of the same enantioselectivity (48% ee), but the use of SDS can reduce the amount of the catalyst and improve the enantioselectivity to 81% ee. These results show that the counteranions do not directly influence the enantioselectivity. Although the effect of SDS on the enhancement of enantioselectivity remains speculative, the formation of micelle ...