Activity For Oxidation Of Alcohols Research Articles

New Cu(I) complexes with biquinolyl-containing polymer ligands as electrocatalysts for O 2 activation in the oxidation of alcohols

Electrochemical approach to a new electroactive catalytic system based on polyamic acids with biquinolyl (biQ) fragments in the polymer backbone capable of coordination to Cu(I)-ions was elaborated using sacrificial Cu anode. The redox properties of the resultant Cu(I) polymer complex were characterized by voltammetric methods. Polynuclear Cu(I) complex with only one biQ ligand per Cu(I) center showed high oxidase activity in air oxidation of aliphatic and aromatic alcohols to corresponding carbonyl derivatives with concomitant reduction of molecular oxygen to water. The reactions proceed in acetonitrile or N-methylpyrrolidone at a potential of Cu II/Cu I electroreduction (−0.55 V versus Ag/AgCl/KCl) with the high preparative yield and current efficiency. The electrocatalytic efficiency is enhanced when the Cu-containing polymer is immobilized on the graphite surface. The stoichiometric composition of the adsorbed polymer complex was determined by means of coulometric assays of the quantities of electroactive biQ fragments and Cu(I) present on the surface. The possibility of the obtained redox-active macromolecules to mimic the active site of certain copper-containing enzymes capable of reversible binding and activation of dioxygen is discussed, providing some insight into the mechanism of the catalytic process.

Highly efficient selective oxidation of alcohols to carbonyl compounds catalyzed by ruthenium (III) meso-tetraphenylporphyrin chloride in the presence of molecular oxygen

Efficient selective oxidation of alcohols to carbonyl compounds by molecular oxygen with isobutyraldehyde as oxygen acceptor in the presence of metalloporphyrins has been reported. Ruthenium (III) meso-tetraphenylporphyrin chloride (Ru(TPP)Cl) showed excellent activity and selectivity for oxidation of various alcohols under mild conditions. Moreover, different factors influencing alcohols oxidation, for example, catalyst, solvent, temperature, and oxidant, have been investigated. In large-scale oxidation of benzyl alcohol, the isolated yield of benzaldehyde of 89% was observed.

Microgel-stabilized gold nanoclusters: Powerful “quasi-homogeneous” catalysts for the aerobic oxidation of alcohols in water

Gold nanoclusters of small size (2.5 nm) and narrow size distribution were synthesized in solution using tailor-made soluble cross-linked polymers (microgels) as exotemplates and stabilizers. The resulting microgel-stabilized nanoclusters could be conveniently isolated by precipitation, stored in the solid state, and redispersed in water and polar organic solvents. They were found to exhibit remarkable catalytic activity (average TOF up to 960 h −1) in the aerobic oxidation of benzylic and aliphatic alcohols and also of polyols in water under mild conditions (50–70 °C, 1–3 atm O 2).

Insight into the nature of active redox sites in Ru-containing hydroxyapatite by DRIFT spectroscopy

The excellent selectivity and activity of ruthenium-hydroxyapatite {RuHAp, HAp = Ca 10(PO 4) 6(OH) 2} in the aerobic oxidation of alcohols has been attributed to isolated, monomeric Ru 3+ species as the active sites. Here we reinvestigated these catalysts by a DRIFT study of CO adsorption and by electron microscopy (STEM) combined with EDX analysis. The study revealed the presence of two major species: isolated Ru 3+ ions and hydrated Ru 3+-oxide particles. The latter structure has high redox activity; it is easily oxidized with oxygen to RuO 2 and reduced by hydrogen or CO at ambient conditions. The amount of this phase in the catalysts correlates well with the alcohol oxidation activity in the liquid phase at close to ambient conditions. In contrast, the redox activity of isolated Ru 3+ ions is significantly lower (or they might be completely inactive). These species may correspond to adsorbed Ru 3+ ions, ion-exchanged Ru 3+ at the outer surface of HAp, or Ru 3+ ions in Ru-phosphate formed by a dissolution–redeposition process from HAp. Our final conclusion is that in RuHAp, the real active sites are small hydrated Ru 3+-oxide nanoparticles (1–2 nm) located on the surface of HAp. Application of a low RuCl 3 concentration and a short contact time between HAp and the aqueous RuCl 3 solution during catalyst preparation help maximize the fraction of the Ru 3+-oxide phase and thus the catalytic activity.

Gold supported on Cu–Mg–Al-mixed oxides: Strong enhancement of activity in aerobic alcohol oxidation by concerted effect of copper and magnesium

Gold nanoparticles were deposited on mixed oxides containing Cu, Mg, and Al in different ratios. The mixed-oxide supports were prepared by flame spray pyrolysis (FSP), resulting in agglomerated primary nanoparticles in the 10–15 nm range, onto which 6- to 9-nm gold particles were deposited by means of deposition–precipitation. The mixed-oxide-supported Au catalysts with noble metal loading of 0.6 ± 0.17 wt% were investigated concerning their structural properties and tested in the aerobic liquid-phase oxidation of 1-phenylethanol to phenyl–methyl ketone affording TOFs up to 1300 h −1. The catalytic tests showed that the activity of these catalysts depends strongly on the composition of the support, with Cu and Mg being crucial components. Strongly enhanced catalytic activity was observed for gold supported on a ternary mixed oxide containing Cu, Mg, and Al at the molar ratio of 5:1:2. Extension of the catalytic tests to various structurally different alcohols indicated that the ternary mixed-oxide-supported gold catalyst has excellent catalytic properties in the aerobic oxidation of a broad range of structurally different alcohols, affording selectivities ⩾ 98 % . XANES revealed both reduced and oxidized Au species on the ternary mixed-oxide supports before and after the reaction. CO 2 adsorption from the liquid phase combined with in situ ATR-IR and modulation excitation spectroscopy was applied to investigate differences in the basic surface properties of the mixed oxides. Monodentate and bidentate carbonates were identified, the former being dominant on ternary Cu-containing supports.

Synthesis of bis-quaternary ammonium peroxotungstates (peroxomolybdates) and their catalytic activity in oxidation of alcohols by aqueous H2O2

Three kinds of bis-quaternary ammonium salts of peroxotungstate and peroxomolybdate, such as PhCH2N-(CH2)6NCH2Ph[W(O2)4] · 2H2O, PhCH2N(CH2)6NCH2Ph[W-O(O2)2(C2O4)] and PhCH2N(CH2)6NCH2Ph[MoO(O2)2(C2O4)], have been synthesized and characterized. Their catalytic activity in the oxidation of cyclohexanol and benzyl alcohol was investigated with only aqueous 30% hydrogen peroxide. The results show that the bis-quaternary ammonium peroxotungstates are excellent catalysts in the oxidation of benzyl alcohol and cyclohexanol under moderate conditions. However, the catalytic ability of bis-quaternary ammonium peroxomolybadates is relatively poor. The yields of benzyl acid, benzaldehyde, and cyclohexanone reached up to 93.0%, 93.6%, and 91.7%, respectively.

Solvent free liquid phase oxidation of benzyl alcohol using Au supported catalysts prepared using a sol immobilization technique

Solvent free oxidation of benzyl alcohol was investigated in the absence of a base using Au catalysts prepared by sol immobilization on titania and carbon supports. Comparison between the Au supported catalysts revealed that activity and distribution of products was dependent on the nature of support and heat treatment. Specifically, heat pre-treatment of the Au catalysts has a beneficial effect in terms of activity, but is detrimental in terms of selectivity to the benzaldehyde. We conclude that sol immobilization is a suitable technique for preparing gold catalysts with small particle size and narrow particle size distributions and very high activity and selectivity for benzyl alcohol oxidation.

Pd and Pt catalysts modified by alloying with Au in the selective oxidation of alcohols

The use of gold on promoting PGM (platinum group metal) catalysts for the selective oxidation of various primary alcohols under mild conditions was investigated. Au/Pd and Au/Pt catalysts showing a single alloyed phase were prepared. It was found that using these bimetallic catalysts instead of monometallic ones caused a significant change in activity in the liquid-phase oxidation of alcohols. Au/Pd catalyst showed a positive synergistic effect; Au/Pt, a negative one. By using aqueous solvent instead of organic solvent (toluene), activity was enhanced for both Au/Pd and Au/Pt catalysts, with some changes in selectivity as well.

Unexpected Performance of Solid Alkaline Metal Hydroxides in Liquid Phase Oxidation of 1-Phenylethanol

Solis alkaline metal hydroxides displayed activity in alcohol oxidation in non-polar medium. Both organic molecules and molecular oxygen were employed as oxidants. The activity was in order KOH > NaOH LiOH.

TEMPO-linked metalloporphyrins as efficient catalysts for selective oxidation of alcohols and sulfides

Six new TEMPO-linked porphyrins and metalloporphyrins were synthesized and they exhibited efficient catalytic activity for selective oxidation of alcohols and sulfides to the corresponding aldehydes, ketones and sulfoxides using NaOCl as oxidant.

WY 14,643 inhibits human aldose reductase activity

Aldose reductase (AR) is implicated to play a critical role in diabetes and cardiovascular complications because of the reaction it catalyzes. Our data reveal that peroxisome proliferator WY 14,643, follows a pure non-competitive inhibition pattern in the aldehyde reduction activity as well as in the alcohol oxidation activity of AR. This finding communicates for the first time a novel feature of WY 14,643 in regulating AR activity. In addition, this observation indicates that AR, AR-like proteins and aldo-keto reductase (AKR) members may be involved in the WY 14,643 mechanism of action when it is administered as PPAR agonist.

Clean and selective oxidation of alcohols catalyzed by ion-supported TEMPO in water

Three different types of ion-supported TEMPO catalysts are synthesized and their catalytic activity in the chemoselective oxidation of alcohols is investigated. These new catalysts show high catalytic activity in water and can be reused for the next run by extraction of products. Recycling experiments exhibit that ion-supported TEMPO can be reused up to five times without loss of catalytic activity. This system offers a very clean, convenient, environmentally benign method for the selective oxidation of alcohols.

Fibrates inhibit aldose reductase activity in the forward and reverse reactions

Fibrates such as bezafibrate, gemfibrozil, clofibric acid, ciprofibrate and fenofibrate, are ligands for peroxisome proliferator-activated receptor α (PPARα), and are used as therapeutic agents in the treatment of hyperlipidemia. Synthesis and accumulation of sorbitol in cells due to aldose reductase (AR) activity is implicated in secondary diabetic complications. In pursuit of finding a lead compound identification to design an effective AR inhibitor employing fragment-based design-like approach, we found that this class of compounds and their nearest neighbors could inhibit AR. Bezafibrate and gemfibrozil displayed a mixed non-competitive inhibition pattern in the glyceraldehyde reduction activity and pure non-competitive inhibition pattern in the benzyl alcohol oxidation activity of AR. Clofibric acid, ciprofibrate and fenofibrate showed pure non-competitive inhibition patterns in the forward reaction. In the reverse reaction, clofibric acid displayed a non-competitive inhibition pattern while ciprofibrate and fenofibrate displayed competitive inhibition patterns. This finding reveals for the first time a novel attribute of the fibrates in the regulation of AR activity and may be useful as lead compounds to control the function of AR in the progression and treatment of secondary diabetic complications in addition to other clinical conditions. Alternatively, these findings demonstrate that AR plays a significant role in the fibrate metabolism under various scenarios.

TEMPO‐Derived Task‐Specific Ionic Liquids for Oxidation of Alcohols.

AbstractFor Abstract see ChemInform Abstract in Full Text.

Immobilization of metallporphyrins on polystyrene: Efficient catalysts for aerobic oxidation of alcohols

Metalloporphyrins of iron and cobalt have been successfully encapsulated for the first time using polystyrene matrix, exhibiting high activity for aerobic oxidation of alcohols mimicking cytochrome P-450 dependent mono oxygenases. This communication provides a simple and environmentally friendly protocol for immobilization of metalloporphyrins (MPs) on to polystyrenes in general, which gives stable, 1 1 Please refer to Supplementary data sheet. reusable (see Footnote 1) and efficient catalysts for aerobic oxidation of alcohols. These catalysts were characterized by UV–vis as well as diffuse reflectance FT-IR spectroscopy. These catalysts not only have high turnover frequencies but also could be recovered quantitatively by simple filtration and reused without loss of activity. Considering their high dispersing capacity in organic solvents, they will definitely find broad spectrum of applications in the electronic as well as optical fields. This methodology will lead to a potential model to mimic the catalytic action of metalloporphyrins in the niche areas such as catalytic oxidations, drug metabolism, DNA cleavage, photodynamic therapy and many others.

Palladium Nanoparticles Entrapped in Aluminum Hydroxide: Dual Catalyst for Alkene Hydrogenation and Aerobic Alcohol Oxidation

[reaction: see text] A new aluminum hydroxide-supported palladium catalyst (1) made by a one-pot synthesis through nanoparticle generation and gelation shows a dual catalytic activity for olefinic hydrogenation and aerobic alcohol oxidation.

TEMPO-Derived Task-Specific Ionic Liquids for Oxidation of Alcohols

A novel 2,2,6,6-tetramethylpiperidine-1-oxyl (TEMPO) radical bearing an ionic liquid-type appendage has been prepared, and its catalytic activity for the selective oxidation of alcohols to the corresponding carbonyl compounds in ionic liquid-aqueous biphasic conditions has been investigated. The ionic liquid-supported TEMPO radical shows catalyst properties similar to those of non-supported counterpart in terms of activity and selectivity, and can be easily recycled and reused without loss of activity and selectivity.

Synthesis, structures, electrochemistry and properties of dioxo-molybdenum(VI) and -tungsten(VI) complexes with novel asymmetric N 2OS, and partially symmetric N 2S 2, NOS 2N-capped tripodal ligands

A new class of asymmetric N-capped (dianionic/trianionic) tripodal proligands [H x (L n )] ( x = 2, n = 1–6; x = 3, n = 7, 8) which possess pendant arms with N 2OS, N 2S 2 or NOS 2 donor groups and with different chelate ring sizes {5,5,5} or {5,6,5} has been prepared. Treatment of these ligands with [WO 2Cl 2(dme)] (dme = 1,2-dimethoxyethane) in the presence of base (triethylamine or KOH) leads to the formation of cis-dioxotungsten(VI) complexes of the types [WO 2(L n )] ( n = 1–6) and K[WO 2(L n )] ( n = 7, 8). Reaction of these tetradentate ligands with [MoO 2(acac) 2] (acac = acetylacetonate) gives the corresponding Mo(VI) analogues [MoO 2(L n )] ( n = 1–6) and K[MoO 2(L n )] ( n = 7, 8). Moreover, a new five coordinate dioxomolybdenum(VI) complex with an NS 2 tridentate ligand [MoO 2(L 9)] has been synthesised using similar procedure. All these compounds have been spectroscopically characterised and the molecular structures of [MoO 2(L n )] ( n = 2, 6) and [WO 2(L 6)] have been established by X-ray diffraction analysis. The electrochemistry and the catalytic activity for oxidation of allylic and benzylic alcohols of these dioxo complexes have also been investigated.

Synthesis and Catalytic Activity of a Fluorous‐Tagged TEMPO Radical.

AbstractFor Abstract see ChemInform Abstract in Full Text.

Poly(ethylene glycol)‐Supported TEMPO: An Efficient, Recoverable Metal‐Free Catalyst for the Selective Oxidation of Alcohols.

AbstractFor Abstract see ChemInform Abstract in Full Text.