Water-soluble Catalyst Research Articles

Selective conversion of aldehydes to carboxylic acids by hemoglobin and air

A new green, environmentally friendly and economically feasible method for the oxygenation of benzaldehyde, cinnamaldehyde, 4-chlorobenzaldehyde and 4-bromobenzaldehyde to the corresponding carboxylic acids using air in the presence of hemoglobin as a water-soluble catalyst in aqueous media at room temperature is illustrated. The resulting products were obtained with (77–100%) conversion and 100% selectivity within a reasonable amount of time. In addition, the first direct characterization of a high-valent iron intermediate (HbFe[Formula: see text]O) measured using Mass Spectroscopy (MS) and UV-vis spectroscopy proved that the major route for oxidation of aldehydes is (HbFe[Formula: see text]O) production.

Development of de Novo Copper Nitrite Reductases: Where We Are and Where We Need To Go.

The development of redox-active metalloprotein catalysts is a challenging objective of de novo protein design. Within this Perspective we detail our efforts to create a redox-active Cu nitrite reductase (NiR) by incorporating Cu into the hydrophobic interior of well-defined three-stranded coiled coils (3SCCs). The scaffold contains three histidine residues that provide a layer of three nitrogen donors that mimic the type 2 catalytic site of NiR. We have found that this strategy successfully produces an active and stable CuNiR model that functions for over 1000 turnovers. Spectroscopic evidence indicates that the Cu(I) site has a lower coordination number in comparison to the enzyme, whereas the Cu(II) geometry may more faithfully reproduce the NiR type 2 center. Mutations at the helical interface successfully produce a hydrogen bond between an interfacial Glu residue and the Culigating His residue, which allows for the tuning of the redox potential over a 100 mV range. We successfully created constructs with as much as a 120-fold improvement from the original design by modifying the steric bulk above or below the Cu binding site. These systems are now the most active water-soluble and stable artificial NiR catalysts yet produced. Several avenues for improving the catalytic efficiency of later designs are detailed within this Perspective, including adjustment of their resting oxidation state, the use of asymmetric scaffolds to allow for single amino acid mutation within the second coordination sphere, and the design of hydrogen-bonding networks to tune residue orientation and electronics. Through these studies the TRI-H system has given insight into the difficulties that arise in creating a de novo redox active enzyme. Work to improve upon this model will provide strategies by which redox-active de novo enzymes may be tuned and detail how native enzymes accomplish catalytic efficiencies through proton gated redox catalysis.

Catalytic Modification of Dehydroalanine in Peptides and Proteins by Palladium-Mediated Cross-Coupling.

Dehydroalanine (Dha) is a remarkably versatile non‐canonical amino acid often found in antimicrobial peptides. Herein, we present the catalytic modification of Dha by a palladium‐mediated cross‐coupling reaction. By using Pd(EDTA)(OAc)2 as water‐soluble catalyst, a variety of arylboronic acids was coupled to the dehydrated residues in proteins and peptides, such as Nisin. The cross‐coupling reaction gave both the Heck product, in which the sp2‐hybridisation of the α‐carbon is retained, as well as the conjugated addition product. The reaction can be performed under mild aqueous conditions, which makes this method an attractive addition to the palette of bio‐orthogonal catalytic methods.

Novel aqueous-phase hydrogenation reaction of the key biorefinery platform chemical levulinic acid into γ-valerolactone employing highly active, selective and stable water-soluble ruthenium catalysts modified with nitrogen-containing ligands

High catalytic activities (TOF = 3000 h−1) have been achieved by novel water-soluble ruthenium catalysts modified with nitrogen-containing ligands such as the bathophenanthrolinedisulfonic acid disodium salt (BPhDS) in the hydrogenation reaction of the renewable polar platform chemical levulinic acid (LA) which possesses a central relevance in the development of biorefineries of the future in a sustainable way to produce with essentially quantitative selectivity of 99.9 mol% γ-valerolactone (GVL) in aqueous media. The apparent activation energy of the Ru/BPhDS catalyst was calculated and amounts a relative low value of 53.3 kJ/mol when one considers that in the LA hydrogenation reaction this catalyst reduces a less reactive keto group into alcohol functionality. A recycling experiment of the Ru/BPhDS catalyst by extraction after addition of diethyl ether has shown that the catalyst is stable without loss of activity and selectivity in a consecutive run.

Enantioselective Michael Addition of Pyrroles with Nitroalkenes in Aqueous Media Catalyzed by a Water-Soluble Catalyst.

A new water-soluble catalytic system was developed and used in an enantioselective Michael addition of pyrroles with nitroalkenes in water to afford nitroethylpyrrole derivatives with both excellent yields and ee values.

Synthesis and evaluation of hemisalen type ligands based on chiral diamine and their use with ruthenium (II) as water-soluble catalysts for the ATH of aromatic ketones

We have developed a robust ruthenium (II) complex catalyst coordinated by chiral Schiff bases for the reduction of acetophenone by ATH in water. The results show a significant effect of the nature of the chiral entity on the reactivity and the selectivity of the catalytic system. The Schiff base synthesized from the chiral diamine is more reactive and selective than the Schiff base synthesized from chiral amino alcohol. The reduction of acetophenone by catalysts coordinated with hemisalen ligands synthesized from chiral cyclohexyl diamine (1–4) gives high asymmetric inductions with ee up to 84% and total conversion. The effectiveness of the best ligand has been evaluating on a set of aromatic/heterocyclic ketones and was resulted to the corresponding alcohols with high enantioselectivities and good yields. A multigram-scale of the reduction process was applied on chroman-4-one and giving access to (R)-(+)-chromanol-4-ol with 87% ee and yield of 79%.

Melamine-Schiff base/manganese complex with denritic structure: An efficient catalyst for oxidation of alcohols and one-pot synthesis of nitriles

Efficient and selective oxidation of alcohol to the corresponding carbonyl and/or nitrile was carried out by a new water-soluble melamine-based dendritic Mn(III) complex (Melamine-Mn (III)-Schiff base complex) in the presence of 2,4,6-trichloro-1,3,5-triazine (TCT) and O2 at room temperature. Also, the oxidation of amine to the corresponding nitrile with high selectivity and conversion was performed at room temperature using the current method and high amounts of turnover frequencies (TOFs) were obtained for reactions. This system was also applicable for direct preparation of oxime through oxidation of alcohol. The catalyst was characterized by Fourier-transform infrared (FTIR), ultraviolet-visible (UV–Vis), thermogravimetric analysis (TGA), energy-dispersive X-ray (EDX), X-ray photoelectron spectroscopy (XPS), CHN and inductively coupled plasma (ICP) analyses. Also, oxidation/reduction behavior of the catalyst was studied by cyclic voltammetry (CV). Moreover, chemoselectivity of the catalyst was discussed with various combinations. The water-soluble catalyst could be recycled from the reaction mixture and reused for several times with a very low losing in efficiency. The recovered catalyst was also investigated with various analyses. Finally, gram scale preparation of nitrile was evaluated by present method.

Next-Generation Water-Soluble Homogeneous Catalysts for Conversion of Glycerol to Lactic Acid

An attractive method for valorization of glycerol is the catalytic transformation to lactic acid. By overcoming the solubility challenge associated with known homogeneous catalysts for this reaction, we show that thermally robust Ir(I), Ir(III), and Ru(II) N-heterocyclic carbene (NHC) complexes with sulfonate-functionalized wingtips are highly prolific for this process, requiring no cosolvents other than aqueous base. The activity of the catalysts is compared under both conventional heating and microwave conditions. The most active catalyst reaches a TOF of 45 592 h–1 (microwave) and 3477 h–1 (conventional) with 1 equiv of KOH, and proceeds at a constant rate for at least 8 h. Although higher activity is observed with KOH, the catalysts are also highly active with the weaker base, K2CO3 (13 000 h–1 and concurrent formation of formate). The protocol can be modified to achieve quantitative conversion of glycerol in only 3 h. The high activity of these catalysts compared to nonsulfonated analogs is attribute...

HATRIC-based identification of receptors for orphan ligands

Cellular responses depend on the interactions of extracellular ligands, such as nutrients, growth factors, or drugs, with specific cell-surface receptors. The sensitivity of these interactions to non-physiological conditions, however, makes them challenging to study using in vitro assays. Here we present HATRIC-based ligand receptor capture (HATRIC-LRC), a chemoproteomic technology that successfully identifies target receptors for orphan ligands on living cells ranging from small molecules to intact viruses. HATRIC-LRC combines a click chemistry-based, protein-centric workflow with a water-soluble catalyst to capture ligand-receptor interactions at physiological pH from as few as 1 million cells. We show HATRIC-LRC utility for general antibody target validation within the native nanoscale organization of the surfaceome, as well as receptor identification for a small molecule ligand. HATRIC-LRC further enables the identification of complex extracellular interactomes, such as the host receptor panel for influenza A virus (IAV), the causative agent of the common flu.

Aqueous-Phase Ring-Opening Metathesis Polymerization-Induced Self-Assembly

We report aqueous-phase Ring-Opening Metathesis Polymerization-Induced Self-Assembly (ROMPISA) for forming well-defined micellar polymer nanoparticles at room temperature and high solids concentration (20 w/w%). This is achieved with a new polymerization initiator, in the form of a water-soluble cationic Hoveyda-Grubbs second generation catalyst. This reaction was used in water to produce diblock copolymers from norbornenyl monomers, which then self-assemble into myriad nanostructure morphologies for which a phase diagram was constructed. Additionally, the living nature of the polymerization initiated by the aqueous initiator was confirmed, as shown by kinetic evaluation under mild conditions in water.

A Green, Organometallic Catalyzed Synthesis of a Series of Novel Functionalized 4‐Aroyl‐4H‐benzo[g]chromenes through One‐pot, Three Component Reaction

A new series of 4‐aroyl‐4H‐benzo[g]chromene derivatives have been synthesized through an efficient, straightforward, and environmentally acceptable one‐pot, three component reaction of malononitrile, different arylglyoxals, and 2‐hydroxy‐1,4‐naphtoquinone (lawsone) in short reaction times and high to excellent yields. The zinc complex of amino acid L‐proline, that is, Zn[L‐proline]2 has been prepared and used as highly active, recyclable, noncorrosive, and water soluble Lewis acid catalyst for this transformation.

Removable Water-Soluble Olefin Metathesis Catalyst via Host-Guest Interaction.

A highly removable N-heterocyclic carbene ligand for a transition-metal catalyst in aqueous media via host-guest interactions has been developed. Water-soluble adamantyl tethered ethylene glycol in the ligand leads a hydrophobic inclusion into the cavity of β-cyclodextrin. Ruthenium (Ru) olefin metathesis catalyst with this ligand demonstrated excellent performance in various metathesis reactions in water as well as in CH2Cl2, and removal of residual Ru was performed via filtration utilizing a host-guest interaction and extraction.

Ring-closing metathesis of unprotected peptides in water.

Ring-closing metathesis (RCM) is an attractive reaction for the preparation of artificially designed peptides. Until now, RCM has been used for fully or partially protected peptides. Herein, the first RCM of unprotected peptides in water was achieved using a water-soluble Ru catalyst.

N-substituted-3(10H)-acridones as visible-light photosensitizers for organic photoredox catalysis

N-Substituted-3(10H)-acridones have been established as visible-light organic photocatalyst. These photosensitizers are efficient for oxidative coupling reaction of N-aryl tetrahydroisoquinolines with various nucleophiles. Notably, N-methyl-3(10H)-acridone (Ia) is stable and can be effectively prepared. It is a water-soluble and atom-economic catalyst, and thus holds promise for green chemical applications. Mechanistic studies confirm a single electron transfer (SET)-induced radical process and a rate-limiting step. Analysis of the photocatalytic reactivity−structure relationship reveals that the acridones are robust and tunable photosensitizers for photoredox catalysis.

Catalytic Organic Reactions in Water toward Sustainable Society.

Traditional organic synthesis relies heavily on organic solvents for a multitude of tasks, including dissolving the components and facilitating chemical reactions, because many reagents and reactive species are incompatible or immiscible with water. Given that they are used in vast quantities as compared to reactants, solvents have been the focus of environmental concerns. Along with reducing the environmental impact of organic synthesis, the use of water as a reaction medium also benefits chemical processes by simplifying operations, allowing mild reaction conditions, and sometimes delivering unforeseen reactivities and selectivities. After the "watershed" in organic synthesis revealed the importance of water, the development of water-compatible catalysts has flourished, triggering a quantum leap in water-centered organic synthesis. Given that organic compounds are typically practically insoluble in water, simple extractive workup can readily separate a water-soluble homogeneous catalyst as an aqueous solution from a product that is soluble in organic solvents. In contrast, the use of heterogeneous catalysts facilitates catalyst recycling by allowing simple centrifugation and filtration methods to be used. This Review addresses advances over the past decade in catalytic reactions using water as a reaction medium.

Colloidal polymer particles as catalyst carriers and phase transfer agents in multiphasic hydroformylation reactions

HypothesisColloidal particles have been used to covalently bind ligands for the heterogenization of homogeneous catalysts. The replacement of the covalent bonds by electrostatic interactions between particles and the catalyst could preserve the selectivity of a truly homogeneous catalytic process. ExperimentsFunctionalized polymer particles with trimethylammonium moieties, dispersed in water, with a hydrophobic core and a hydrophilic shell have been synthesized by emulsion polymerization and have been thoroughly characterized. The ability of the particles with different monomer compositions to act as catalyst carriers has been studied. Finally, the colloidal dispersions have been applied as phase transfer agents in the multiphasic rhodium-catalyzed hydroformylation of 1-octene. FindingsThe hydrodynamic radius of the particles has been shown to be around 100 nm, and a core-shell structure could be observed by atomic force microscopy. The polymer particles were proven to act as carriers for the water-soluble hydroformylation catalyst, due to electrostatic interaction between the functionalized particles bearing ammonium groups and the sulfonated ligands of the catalyst. The particles were stable under the hydroformylation conditions and the aqueous catalyst phase could be recycled three times.

Nonaqueous Biphasic Hydroformylation of Long Chain Alkenes Catalyzed by Water Soluble Phosphine Rhodium Catalyst with Polyethylene Glycol Instead of Water

The application of polyethylene glycol (donated as PEG), as an environmentally benign solvent instead of water, in rhodium catalyzed hydroformylation of long chain alkenes by using water soluble phosphine BISBIS or TPPTS (TPPTS: sodium salt of sulfonated triphenylphosphine, BISBIS: sodium salt of sulfonated 2,2′-bis(diphenylphosphinomethyl)-1,1′-biphenyl) is herein reported. The conversion of long chain alkenes in PEG-200 could reach above 95.0% after a short reaction time (15 min). In addition, an efficient phase separation and recycling of PEG-200 and catalyst were achieved. The leaching of rhodium into product phase detected by ICP-AES was less than 0.06 wt% of the initial amount.

HIGHLY ACTIVE CATALYSTS FOR OXIDATION OF THIOLS

The problem of disposal of toxic and corrosion-active sulfhydryl substances (deodorization), natural hydrocarbons is relevant to operational and environmental aspects. One method of removing these impurities is catalytic oxidation to non-toxic disulfide form. The message shows the results of a comparative study of the oxidation reaction of thiols by oxygen to disulfides in hydrocarbon media, catalyzed by complexes of copper salts (I, II) with various nitrogen-containing bases. As nitrogen-containing ligands, mono - and diethanolamine with different C4-C18 hydrocarbon radicals were used. It is established that water-soluble catalyst composition on the basis of monoethanolamine and the hydrocarbon-soluble complex of copper Cu(II) with N-octadecyldiethanolamine exhibits low activity in the oxidation of 1-octanethiol. It was found the activating effect of HCl on the activity of catalysts in various hydrocarbons (model mixture, vacuum gasoil, naphtha and gas condensate of the Karachaganak field), which allows for an exhaustive oxidation of thiols with the initial concentrations ≥1000 ppm. However, the introduction of hydrogen chloride is accompanied by the appearance of corrosion. The introduction of corrosion inhibitors have led to the complete deactivation of the catalysts. The high-performance catalytic system based on CuCl2/CuO was designed, for which we found the optimum ratio of catalyst/inhibitor, to eliminate the corrosion effect while maintaining a high level of activity. The kinetics of the oxidation reaction of the sulfhydryl derivatives by oxygen was studied. It was found that regardless of the nature of the hydrocarbon media, for all investigated catalysts a zero order on concentration of the thiol and close to first order on the catalyst concentration is observed. The use of developed catalysts and purification technology in the industry will reduce the environmental hazard during the transportation and storage of petroleum products.Forcitation:Pletneva I.V., Gavrilov Yu.A. Highly active catalysts for oxidation of thiols. Izv. Vyssh. Uchebn. Zaved. Khim. Khim. Tekhnol. 2017. V. 60. N 8. P. 70-73.

A Reusable Palladium/Cationic 2,2′-Bipyridyl System-Catalyzed Double Mizoroki-Heck Reaction in Water

A reusable PdCl2(NH3)2/cationic 2,2′-bipyridyl system was used to catalyze the double Mizoroki-Heck reaction of aryl iodides with electron-deficient alkenes in water in the absence of inert gas, giving β,β-diarylated carbonyl derivatives in good to excellent yields. The formation of unsymmetrical β,β-diarylated alkenes were also studied by coupling aryl iodides with the corresponding aryl-substituted α,β-unsaturated carbonyl compounds. This water-soluble catalyst can be swiftly separated from the organic layer using simple extraction for the further reuse, and, thus, makes it an operationally-simple and environmentally-benign procedure.

A coordinatively saturated cobalt complex as a new kind catalyst for efficient electro- and photo-catalytic hydrogen production in purely aqueous media

It has been shown that coordinatively unsaturated complexes can catalyze hydrogen production via an unstable hydride intermediate. Herein we present a new kind of water soluble catalyst based on a coordinatively saturated cobalt complex, [(phen)2Co(CN)2]⋅ClO41 that is formed by the reaction of 1,10-phenanthroline (phen), Co(ClO4)2·6H2O and tetracyanoethylene (TCNE). Under photoirradiation with blue light (λmax = 469 nm) in air, together with [Ru(bpy)3]Cl2 and ascorbic acid in a pH 5.5 aqueous solution, 1 possesses photocatalytic activity for water reduction to hydrogen with an initial turnover number (TON) of 1232H2 per mol of catalyst at first 10 h, and this activity is sustained for at least 70 h. This can be attributed to that oxidative quenching by 1 (kq = 1.69 × 1010 M−1 s−1) dominates over reductive quenching to [Ru(bpy)3]Cl2 by ascorbic acid (kq = 1.55 × 1010 M−1 s−1). Additionally, 1 electrocatalyze hydrogen generation from a neutral water with a turnover frequency (TOF) of 1113.1 mol of hydrogen per mole of catalyst per hour (mol H2/mol catalysts/h) at an overpotential (OP) of 838 mV. We hope this can afford a new method in proton or water reduction catalysis using coordinatively saturated complexes in purely aqueous media.