Aqueous Catalyst Phase Research Articles

ChemInform Abstract: Cellulose: A New Bio‐Support for Aqueous Phase Catalysts.

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.

Stability of supported platinum catalysts in aqueous phase under hydrogen atmosphere

Two supported platinum catalysts (1.0 wt.% Pt/alumina ( D=51%) and 1.0 wt.% Pt/silica ( D=41%)) were treated at room temperature under nitrogen or hydrogen in aqueous media of various pH (pH=0.7, HCl; pH=6, water; pH=10, NH 4OH). Then, the catalysts were filtered, dried and activated following various procedures. The dispersions of the different samples were determined from transmission electron microscopy (TEM) and/or chemisorption measurements. On preoxidized samples, a sintering of platinum is observed under hydrogen bubbling whatever the pH of the solution and it is higher on the silica support. An in situ reduction allows to prevent the metal accessibility loss on alumina and to restrict that observed on silica. Otherwise, the activation mode (direct reduction or calcination–reduction) can modify the platinum accessibility of the Pt/alumina catalyst treated in HCl medium.

Cellulose: a new bio-support for aqueous phase catalysts.

Cellulose: a new bio-support for aqueous phase catalysts.

Cellulose: a new bio-support for aqueous phase catalysts

The choice of a hydrophilic bio-polymer, such as cellulose, as the support of the water soluble Pd(OAc)2/5 TPPTS system, leads to a new and efficient heterogeneous catalyst for the Trost Tsuji allylic alkylation reaction.

ChemInform Abstract: A Novel Amphiphilic Chiral Ligand Derived from D-Glucosamine. Application to Palladium-Catalyzed Asymmetric Allylic Substitution Reaction in an Aqueous or an Organic Medium, Allowing for Catalyst Recycling.

A novel amphiphilic phosphinite−oxazoline chiral compound, 2-methyl-4,5-[4,6-O-benzylidene-3-O-bis{4-((diethylamino)methyl)phenyl}phosphino-1,2-dideoxy-α-d-glucopyranosyl]-[2,1-d]-2-oxazoline (1), has been prepared from natural d-glucosamine hydrochloride. The newly prepared complex, [Pd(2-methyl-4,5-[4,6-O-benzylidene-3-O-bis{(4-((diethylmethylammonium)methyl)phenyl)}phosphino-1,2-dideoxy-α-d-glucopyranosyl]-[2,1-d]-2-oxazoline)(η3-C3H5)]3+·3BF4- (3), is soluble in water and an efficient catalyst for asymmetric allylic substitution reaction in water or an aqueous/organic biphasic medium (up to 85% ee). This catalytic system offers an easy separation of the aqueous catalyst phase from the product phase and allows recycling of the catalyst phase. In addition, compound 1 also works as an effective ligand for the palladium-catalyzed reaction under conventional homogeneous conditions in an organic medium, in which the catalyst (Pd−1 complex) can be recovered by simple acid/base extraction and reused in the se...

Chitosan: A Natural Polymeric Support of Catalysts for the Synthesis of Fine Chemicals

The high surface hydrophilicity of chitosan is the property which has allowed the synthesis of an efficient, selective, and stable palladium supported aqueous phase catalyst for the reaction of allylic substitution of (E)-cinnamyl ethyl carbonate by morpholine. The adjustment of the water content of the catalytic solid and the addition of a cationic surfactant (CTAB) in the medium both contribute to improve drastically the efficiency of the catalyst while keeping the palladium leaching below 0.5%.

A novel amphiphilic chiral ligand derived from D-glucosamine. Application to palladium-catalyzed asymmetric allylic substitution reaction in an aqueous or an organic medium, allowing for catalyst recycling

A novel amphiphilic phosphinite-oxazoline chiral compound, 2-methyl-4,5-[4,6-O-benzylidene-3-O-bis[4-((diethylamino)methyl)phenyl]phosphino-1,2-dideoxy-alpha-D-glucopyranosyl]-[2,1-d]-2-oxazoline (1), has been prepared from natural D-glucosamine hydrochloride. The newly prepared complex, [Pd(2-methyl-4,5-[4,6-O-benzylidene-3-O-bis[(4-((diethylmethylammonium)methyl)phenyl)]phosphino-1,2-dideoxy-alpha-D-glucopyranosyl]-[2,1-d]-2-oxazoline)(eta3-C3H5)]3+ x 3BF4- (3), is soluble in water and an efficient catalyst for asymmetric allylic substitution reaction in water or an aqueous/organic biphasic medium (up to 85% ee). This catalytic system offers an easy separation of the aqueous catalyst phase from the product phase and allows recycling of the catalyst phase. In addition, compound 1 also works as an effective ligand for the palladium-catalyzed reaction under conventional homogeneous conditions in an organic medium, in which the catalyst (Pd-1 complex) can be recovered by simple acid/base extraction and reused in the second reaction.

Novel Water-Soluble Bisphosphinite Chiral Ligands Derived from alpha,alpha- and beta,beta-Trehalose. Application to Asymmetric Hydrogenation of Dehydroamino Acids and Their Esters in Water or an Aqueous/Organic Biphasic Medium.

Novel 2,3:4,6-di-O-isopropylidene-alpha-D-glucopyranosyl-(1,1)-4,6-O-isopropylidene-2,3-di-O-diphenylphosphino-alpha-D-glucopyranoside (2), 2,3:4,6-di-O-cyclohexylidene-alpha-D-glucopyranosyl-(1,1)-4,6-O-cyclohexylidene-2,3-di-O-diphenylphosphino-alpha-D-glucopyranoside (4), and 2,3:4,6-di-O-cyclohexylidene-beta-D-glucopyranosyl-(1,1)-4,6-O-cyclohexylidene-2,3-di-O-diphenylphosphino-beta-D-glucopyranoside (11) were prepared from the corresponding alpha,alpha- or beta,beta-trehalose. The ligands were transformed into cationic Rh complexes, such as [Rh(alpha-D-glucopyranosyl-(1,1)-2,3-di-O-diphenylphosphino-alpha-D-glucopyranoside)(cod)]BF(4) (3) and [Rh(beta-D-glucopyranosyl-(1,1)-2,3-di-O-diphenylphosphino-beta-D-glucopyranoside)(cod)]BF(4) (12) bearing free hydroxy groups. These complexes were soluble in water and were efficient catalysts for the asymmetric hydrogenation of dehydroamino acids and their esters in water or an aqueous/organic biphasic medium with high enantioselectivity (up to 99.9% ee). Aqueous biphasic systems offer an easy separation of the aqueous catalyst phase from the product phase and allow recycling of the catalyst phase without the loss of enantioselectivity.

A stable and recyclable supported aqueous phase catalyst for highly selective hydroformylation of higher olefins†

A highly regioselective supported aqueous phase hydroformylation catalyst is presented that is completely and conveniently separated from the products and reused in numerous consecutive catalytic cycles.

Palladium(0) allylic alkylation in a two-phase system or with a supported aqueous phase catalyst

The reaction of allylic carbonates with various acyclic and cyclic carbonucleophiles is catalyzed by the system Pd(OAc) 2 and P(C 6H 4- m-SO 3Na) 3 (or tppts) in a two-phase liquid medium H 2O-nitrile, the activity of the catalyst depending mainly on the nature of the nitrile, the temperature of the reaction and the ratio palladium/tppts. The same system Pd(OAc) 2 and P(C 6H 4- m-SO 3Na) 3 supported on silica catalyzes also this reaction. The formation of the active palladium species in the two cases is followed by 31 P NMR spectroscopy and discussed.

Effect of pH on rate and selectivity behavior in biphasic hydroformylation of 1-octene

The effect of pH on activity and selectivity of (RhCl(COD) 2 TPPTS catalyzed hydroformylation of 1-octene in a biphasic medium has been studied. The pH of the aqueous catalyst phase shows a strong influence on the rate of reaction and n iso ratio of the aldehyde products. The effect of P Rh ratio, catalyst and 1-octene concentration, partial pressure of hydrogen and carbon monoxide was studied at 7 and 10 pH, which showed significantly different trends. The rates increased by two- to five fold when the pH was changed from 7 to 10. While the dependence of the rate was found to be linear on the olefin and hydrogen concentration at both 7 and 10 pH, the rate of hydroformylation was found to be inhibited with increase in catalyst concentration beyond 1 × 10 −3 kmol m −3. The effect of partial pressure of carbon monoxide was linear at pH 7 whereas at pH 10 a substrate inhibited kinetics was observed.

Alternative supported aqueous-phase catalyst systems

The concept of supported aqueous-phase (SAP) catalysis has been extended to olefin hydroformylations by the use of in situ formed Rh-, PtSnCl 3- and Co-complexes containing HexDPPDS, TAPTS and TPrPTS as ligands, respectively. (HexDPPDS = hexyl-bis(sodium- m-sulfonatophenyl)phosphine; TAPTS = tris(ω-(sodium- p-sulfonatophenyl)alkyl)phosphines, where alkyl CH 2, TBeTS; C 2H 4, TEtPTS, C 3H 6, TPrPTs). Furthermore, some data are reported on the SAP asymmetric hydroformylation of styrene by the use of PtCl 2[( S,S)-BDPP-(( p-NMe 3)(BF 4)) 4] + SnCl 2 system and on the SAP asymmetric hydrogenation of dehydro-phenylalanine derivatives with Rh(COD)[( S,S)-BDPP-( p-NME 3) 4](BF 4) 5 and Rh(COD)[( S,S)-Chiraphos-( p-NMe 3) 4](BF 4) 5 complexes. (BDPP = 2,4-bis(diphenylphosphino)pentane; Chiraphos = 2,3-bis(diphenylphosphino)butane). For the sake of comparison, the two-phase catalytic results are also given with each alternative SAP catalytic applications, as well as the appropriate (organic) homogeneous values, which were obtained with the analogous complexes containing the respective non-funtionalized ligands. With the exception of the Co-system, the SAP catalytic systems show similar selectivity only to the analogous non-aqueous catalysts. The anomalous behavior of the Co-system in the presence of water is attributed to the presence of sulfonate groups on the ligand which may interact with the cobalt.

Two‐Phase Catalysis: A Strategy for Avoiding Consecutive Reactions as Exemplified in the Telomerization of Butadiene and Ammonia

The industrially interesting primary octadienylamines 1 and 2 can be synthesized selectively for the first time from 1,3-butadiene and ammonia. The use of an aqueous catalyst phase together with an organic solvent as a second phase are the key to the success of this process. Consecutive reactions of the primary amines 1 and 2, which are more nucleophilic than ammonia, can thus be avoided.

Catalytic olefin hydrogenation with the application of a new water soluble rhodium catalyst

The catalyst precursor preparedin situ from rhodium dimer [Rh(cod)Cl]2 and a new water-soluble phosphine Ph2PCH2CH2CONHC(CH3)2CH2SO3H (in Li+ salt form) has been found to act as an effective olefin hydrogenation catalyst. Catalytic hydrogenation reactions have been tested in either two phase: aqueous catalyst/insoluble olefin or methanolic catalyst/olefin systems. The observed reaction rates were higher for terminal than for internal olefins. 1-Hexene in methanolic solution has been hydrogenated with a turnover frequency of about 8000 h−1. This system has also been applied in the form of a supported aqueous phase catalyst.

Selective catalytic synthesis of fine chemicals: opportunities and trends

Recent, environmentally-driven trends in the manufacture of fine chemicals are reviewed. Comparison of alternative processes on the basis of their atom utilization and E factor (kg byproducts/kg product) i s discussed. The use of chromium-substituted molecular sieves (CrAPO-5 and 11 and Cr silicalite) as recyclable solid catalysts for benzylic and allylic oxidations, the oxidation of secondary alcohols to ketones and the selective decomposition of alkyl hydroperoxides, is described. New developments in the use of zeolite-encapsulated metal complexes as solid catalysts for oxidations and reductions are reviewed. The use of palladium(0) trisulfonated triphenylphosphine complex as a catalyst for carbonylation in water is reported. Finally, the use of supported aqueous phase catalysts in various processes, including enantioselective hydrogenation, is briefly reviewed.

Asymmetric Synthesis of Naproxen by a New Heterogeneous Catalyst

A new heterogeneous, asymmetric catalyst is described. The catalyst is a modified version of the supported aqueous-phase catalyst reported previously (Wan and Davis, J. Catal. 148, 1 (1994)); ethylene glycol is used in place of water as the hydrophilic phase. Both the enantioselectivity and the activity of this new heterogeneous catalyst are comparable to the homogeneous analogue in neat methanol (or ethylene glycol); e.e.′s are 95.7% vs 96.1% and t.o.f.′s are 40.7 hr −1 vs 131.0 hr −1, respectively. Recycling of the catalyst is possible without leaching of ruthenium at a detection limit of 32 ppb.

Enhancement of interfacial catalysis in a biphasic system using catalyst-binding ligands

TO avoid the problem of separation of products from catalyst in homogeneous catalysis1, two-phase systems have been developed in which the catalytic complex (usually a water-soluble organo-metallic complex) remains in one (generally aqueous) phase while the products remain in a second, immiscible phase2. Catalysis relies on the transfer of organic substrates into the aqueous catalyst phase; but the limited solubility of these substrates in water leads to reaction rates much lower than those for conventional homo-geneous catalysis. Here we show that catalysis at the interface of a two-phase system can be enhanced by using a 'promoter ligand' which, although soluble in the organic phase, will bind to the organometallic catalyst and thus increase its concentration close to the interface in the aqueous phase. We demonstrate this approach for the hydroformylation of 1-octene using a rhodium-based catalyst. A rate enhancement by a factor of 10–50 is observed when we introduce the promoter ligand PPh3 in the organic phase.

Phosphorus-31 NMR spin lattice relaxation times as an indirect probe of adsorbed water in supported aqueous phase catalysts

Phosphorus-31 spin lattice relaxation times, T 1's, for SAP hydroformylation catalysts derived from HRh (CO) (TPPTS) 3 and TPPTS (TPPTS = trisulfonated triphenyl phosphine trisodium salt) are consistent with a liquid-like character for the supported aqueous phase. Ale T 1 for solid TPPTS is 1150 s while for TPPTS in a supported aqueous phase T 1 varies from 220 to 4.9 s. A T 1 of 4.9 s is close to the value obtained for TPPTS in solution and is observed at a H 2O/P ratio of 24.9. At this level of water content previously reported SAP catalysts have shown maximum catalytic activity for the hydroformylation of olefins.

The beneficial effect of alkali metal salt on supported aqueous-phase catalysts for olefin hydroformylation

Alkali metal salt modified SAP (supported aqueous-phase) rhodium catalysts prepared by coimpregnation method using alkali metal chloride were found to be active and selective for olefin hydroformylation. The salt addition promoted the formation of aldehydes with high selectivity, the aldehyde yield being increased more than 2.5 times at a proper salt/Rh ratio. Changes in stretching frequency of the carbonyl species were detected during ethene hydroformylation, which appeared at ca. 1625 cm−1 on the non-modified SAP catalyst sample, while at ca. 1586 cm−1 on the KCl-modified one, as shown by in situ IR spectroscopy. The results of a deuterium isotope effect experiment showed that the hydroformylation rate for aldehyde formation on SAP rhodium catalyst under atmospheric pressure of CO/D2 was about 1.3 times faster than that under CO/H2, implying that the rate-determining step involved in aldehyde formation is most probably a step related with hydrogen. The role of the alkali metal salt is discussed in relation with the reaction mechanism.

Selective hydrogenation of α,β-unsaturated aldehydes catalyzed by supported aqueous-phase catalysts and supported homogeneous catalysts

Selective hydrogenations of different α,β-unsaturated aldehydes into allylic alcohols with immobilized homogeneous catalysts are reported. Different kinds of catalysts were used: supported aqueous-phase catalysts (RuCl 2(TPPTS) 3/SiO 2 and RuH 2(TPPTS) 4/SiO 2) and supported homogeneous catalysts (especially phosphino-iridium catalysts like IrCl 3{(C 6H 5)P[(CH 2) 3SiO 3 2 ] 2·2N[(CH 2) 3SiO 3 2 ] 3·2SiO 2} 3). Some of them are good alternatives to homogeneous catalysts since they are chemoselective, sometimes stereoselective and easy to recover.