Efficient Catalyst For Aerobic Oxidation Research Articles

Theoretical Studies on Muti‐Hydroxyimides as Highly Efficient Catalysts for Aerobic Oxidation

N,N-dihydroxypyromellitimide (NDHPI) and N,N',N''-trihydroxyisocyanuric acid (THICA) have been recently demonstrated to act as better carbon-radical-producing catalysts than the popular N-hydroxyphthalimide (NHPI). To gain a mature understanding of these particular catalysts, herein their geometrical, electronic, and thermochemical properties, as well as their catalytic activities, have been systemically investigated by a theoretical analysis. It appears that THICA, unlike NDHPI and NHPI, is unsuitable for solvent-free catalysis or catalysis in aprotic solvents due to its favorable coexistent planar conformer. Besides, the more remarkable catalytic efficiencies of NDHPI and THICA compared to NHPI can be ascribed to the lower barriers and the endothermicity in the H-abstraction processes by their radicals, especially by their multi-radicals which show stronger electron-withdrawing effects. Furthermore, the generation of THICA radicals would be much feasible at high temperature without co-catalysts. This study provides a new perspective towards the rational design of reactive hydroxyimide organocatalysts for industrial applications.

An ionic compound containing Ru(III)-complex cation and phosphotungstate anion as the efficient and recyclable catalyst for clean aerobic oxidation of alcohols

A novel ionic compound (3, [RuCl4(L)2]3PW12O40) containing the Ru(III)-complex cation and α-Keggin-type phosphotungstate anion was synthesized and proven to be the efficient catalyst for aerobic oxidations of alcohols free of base and nitroxyl radical. Specially, 3 could be reused at least five runs without obvious activity loss. The stability of 3 was dramatically improved due to the incorporation of [PW12O40]3 − as the counter-anions, leading to its available recyclability.

Bimetallic Au–Pd/MgO as efficient catalysts for aerobic oxidation of benzyl alcohol: A green bio-reducing preparation method

The oxidation of benzyl alcohol, with molecular oxygen at atmospheric pressure in an aqueous medium, is investigated using Au–Pd/MgO bimetallic catalysts to examine the effect of catalyst parameters (viz. preparation method, Au/Pd molar ratio, and calcinations temperature) and reaction conditions (viz. reaction temperature and oxygen flow rate) on conversion and selectivity. The bimetallic catalysts were prepared via two novel reduction methods with bio-reducing agents and were characterized by transmission electron microscopy, X-ray diffraction, diffuse reflectance UV–vis spectroscopy, and thermogravimetric analysis to understand synergistic interactions between Au and Pd. Under optimal conditions, the Au–Pd bimetallic catalysts, with a 1:1 molar ratio and 9.7±1.3nm particle size, exhibited remarkably enhanced catalytic activity (>52%) and selectivity (∼100%) compared with their monometallic counterparts. Moreover, the activity of the catalysts was maintained after six recycles without agglomeration.

ChemInform Abstract: Size‐Controlled Synthesis of Gold Clusters as Efficient Catalysts for Aerobic Oxidation

This article summarizes our recent research on the size-controlled synthesis of Au clusters stabilized by a polymer or supported by a solid, and related work reported by others. Small Au clusters have excellent, size-specific catalytic activity in the aerobic oxidation of alcohols and alkanes.

Size-Controlled Synthesis of Gold Clusters as Efficient Catalysts for Aerobic Oxidation

This article summarizes our recent research on the size-controlled synthesis of Au clusters stabilized by a polymer or supported by a solid, and related work reported by others. Small Au clusters have excellent, size-specific catalytic activity in the aerobic oxidation of alcohols and alkanes.

Chitosan-stabilized gold, gold–palladium, and gold–platinum nanoclusters as efficient catalysts for aerobic oxidation of alcohols

Chitosan was used as a stabilizer for the synthesis of Au, AuPd and AuPt nanoclusters (NCs). The produced NCs had a narrow particle size distribution with sizes less than 2.3 nm in diameter and were characterized by various techniques such as UV–Visible spectroscopy, X-ray diffraction, X-ray photoelectron spectroscopy, transmission electron microscopy and scanning electron microscope energy dispersive spectroscopy (STEM-EDS). These metal NCs exhibited high catalytic activity toward the aerobic oxidation of various alcohols under ambient conditions comparable with the reported Au:PVP catalyst. Au NCs protected by chitosan could easily be recovered for repeated use.

Novel Ca-doped CePO4 supported ruthenium catalyst with superior catalytic performance for aerobic oxidation of alcohols

Ca-doped cerium phosphate (CeCaPO(4)) has been newly developed and successfully used as catalyst support with superior ion-exchanged property and oxygen activation ability. Ru(3+) exchanged CeCaPO(4) is identified as an efficient catalyst for aerobic oxidation of alcohols with the highest TOF (∼408 h(-1)) reported so far on supported Ru catalysts.

ChemInform Abstract: Graphite‐Supported Gold Nanoparticles as Efficient Catalyst for Aerobic Oxidation of Benzylic Amines to Imines and N‐Substituted 1,2,3,4‐Tetrahydroisoquinolines to Amides: Synthetic Applications and Mechanistic Study.

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Graphite‐Supported Gold Nanoparticles as Efficient Catalyst for Aerobic Oxidation of Benzylic Amines to Imines and N‐Substituted 1,2,3,4‐Tetrahydroisoquinolines to Amides: Synthetic Applications and Mechanistic Study

Selective oxidation of amines using oxygen as terminal oxidant is an important area in green chemistry. In this work, we describe the use of graphite-supported gold nanoparticles (AuNPs/C) to catalyze aerobic oxidation of cyclic and acyclic benzylic amines to the corresponding imines with moderate-to-excellent substrate conversions (43-100%) and product yields (66-99%) (19 examples). Oxidation of N-substituted 1,2,3,4-tetrahydroisoquinolines in the presence of aqueous NaHCO3 solution gave the corresponding amides in good yields (83-93%) with high selectivity (up to amide/enamide=93:4) (6 examples). The same protocol can be applied to the synthesis of benzimidazoles from the reaction of o-phenylenediamines with benzaldehydes under aerobic conditions (8 examples). By simple centrifugation, AuNPs/C can be recovered and reused for ten consecutive runs for the oxidation of dibenzylamine to N-benzylidene(phenyl)methanamine without significant loss of catalytic activity and selectivity. This protocol "AuNPs/C+O2" can be scaled to the gram scale, and 8.9 g (84 % isolated yield) of 3,4-dihydroisoquinoline can be obtained from the oxidation of 10 g 1,2,3,4-tetrahydroisoquinoline in a one-pot reaction. Based on the results of kinetic studies, radical traps experiment, and Hammett plot, a mechanism involving the hydrogen-transfer reaction from amine to metal and oxidation of M-H is proposed.

The functionalized poly(ethylene glycol) supported palladium nanoparticles as a highly efficient catalyst for aerobic oxidation of alcohols

The aerobic oxidation of various alcohols was studied with the stabilizing palladium nanoparticles as the catalyst under very mild conditions in poly(ethylene glycol) (PEG) media. The bidentate nitrogen ligand functionalized-PEG played an important role in stabilizing and immobilizing palladium nanoparticles. The stabilizing palladium nanoparticles were found to be highly active for the oxidation of benzyl alcohol. Finally, the scope and limitation of substrates have also been investigated for this novel catalytic system.

A novel method for immobilization of Co tetraphenylporphyrins on P(4VP-co-St)/SiO 2: Efficient catalysts for aerobic oxidation of ethylbenzenes

In this paper, poly(4vinylpyridine-co-styrene) (P(4VP-co-St)) was grafted on silica gel particles in the manner of “grafting from”, and the grafting particle P(4VP-co-St)/SiO 2 was gained. The grafting particle P(4VP-co-St)/SiO 2 is a novel kind of supports for immobilizing metalloporphyrin catalysts. Then, the immobilization of cobalt tetraphenylporphyrin (CoTPP) on the supports P(4VP-co-St)/SiO 2 was carried out via the axial coordination reaction between CoTPP and the pyridine groups of the grafted P(4VP-co-St), resulting in the heterogenised catalysts CoTPP–P(4VP-co-St)/SiO 2. The synthesized catalysts were characterized by FTIR and the axial coordination process between CoTPP and the grafted P(4VP-co-St) was confirmed by UV–vis. The effects of various factors on the immobilization reaction of CoTPP were studied in detail. Finally, the catalytic performance of CoTPP–P(4VP-co-St)/SiO 2 in the catalytic oxidation process of ethyl benzene was investigated. The experimental results show that the axial coordination reaction is a very easy and novel method for favorably immobilizing CoTPP onto the P(4VP-co-St)/SiO 2 surfaces. During the immobilization process of CoTPP on P(4VP-co-St)/SiO 2, the most bonding amount of CoTPP (0.19 g/g) is obtained under the lower temperature (5 °C) and the higher concentration of CoTPP(6.0 mg/ml) lasting 4 h. Moreover, the supported catalyst CoTPP–P(4VP-co-St)/SiO 2 can effectively activate the dioxygen, and obviously catalyze the transform of ethylbenzene into acetophenone. So it exhibits the fine catalytic activity.

Hydrous ruthenium oxide supported on Co3O4 as efficient catalyst for aerobic oxidation of amines

Ruthenium catalysts supported on various metal oxides and Co3O4-supported various transition metal catalysts prepared by an adsorption-precipitation method were examined for the aerobic oxidation of benzyl amine. We found that the Co3O4-supported ruthenium catalyst exhibited the best catalytic performance. The Co3O4-supported ruthenium catalyst was also effective for the aerobic oxidation of several other amines. The present catalyst could be used recyclably and be operated under solvent-free conditions. The activity of the present catalyst for the aerobic oxidation of benzyl amine depended less on the oxygen pressure, and the catalyst was also efficient even when air was used as an oxidant. The content of ruthenium and the size of Co3O4 particles played crucial roles in determining the catalytic performance. We have clarified that the supported hydrous ruthenium oxide (RuO2·xH2O) is the active species for the aerobic oxidation of benzyl amine, whereas the supported metallic ruthenium (Ru°) and supported ruthenium chloride (RuCl3) are inactive, and the supported anhydrous ruthenium oxide (RuO2) only exhibits a lower activity.

Water‐Soluble Diruthenium Complexes Bearing Acetate and Carbonate Bridges: Highly Efficient Catalysts for Aerobic Oxidation of Alcohols in Water.

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Water-soluble diruthenium complexes bearing acetate and carbonate bridges: highly efficient catalysts for aerobic oxidation of alcohols in water

The aerobic oxidation of alcohols in water can be performed efficiently in the presence of a catalytic amount of the water-soluble diruthenium complex Ru2(micro-OAc)3(micro-CO3) under an atmospheric pressure (1 atm) of O2.

SELECTIVE OXIDATION OF ALCOHOLS BY REDOX MOLECULAR SIEVES

ABSTRACT High-throughput synthesis and screening of libraries consisting of redox zeolites and molecular sieves have been developed for the selective oxidation of 2-butyl-5-hydroxymethyl-imidazole to the corresponding aldehyde in the liquid phase. Libraries consisting of 96 catalysts were prepared and screened for catalytic activity using high-throughput software, robotics, reactor, and screening technologies. The integrated synthesis and screening workflow allowed ∼5000 samples to be screened in less than one month. Promising hits identified in the high-throughput primary screens were successfully scaled up and optimized in conventional laboratory test units. Best results have been obtained with doubly or triply doped mesoporous sieves containing both an impregnated and framework-substituted metal. PtBi-doped framework-substituted V-MCM-41 redox mesoporous sieves were found to be efficient catalysts for aerobic oxidation under relatively mild reaction conditions (100–150°C, 15–400 psi air, 4–10 h reaction time). MIBK/H2O/t-BuOH mixtures were identified as efficient solvent systems for this reaction. Isolated yields confirm high selectivities of more than 90% with quantitative conversions. Spent catalysts were shown to be fully regenerable by high temperature calcination in air.

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.

ChemInform Abstract: Catalytic Asymmetric and Chemoselective Aerobic Oxidation: Kinetic Resolution of sec-Alcohols.

Optically active (nitroso)(salen)ruthenium(II) chloride (2) was found to be an efficient catalyst for aerobic oxidation of racemic secondary alcohols under irradiation with a halogen or fluorescent lamp, which proceeded with good enantiomer-differentiation (krel=11–20). Furthermore, no epoxidation was observed in the oxidation of racemic 4-phenyl-3-buten-2-ol.

Catalytic asymmetric and chemoselective aerobic oxidation: kinetic resolution of sec-alcohols

Optically active (nitroso)(salen)ruthenium(II) chloride ( 2) was found to be an efficient catalyst for aerobic oxidation of racemic secondary alcohols under irradiation with a halogen or fluorescent lamp, which proceeded with good enantiomer-differentiation (k rel=11–20). Furthermore, no epoxidation was observed in the oxidation of racemic 4-phenyl-3-buten-2-ol.