Functionalization of silicon surfaces with catalytically active Pd complexes and application to the aerobic oxidation of benzylic alcohols

A single-crystal silicon surface was modified with a bisoxazoline-Pd molecular layer and utilized as a highly efficient (catalyst turnover number up to 780,000, 110 degrees C, 72 h) and recyclable catalyst in the aerobic oxidation of benzylic alcohols.     

Oxidant-free oxidation: ruthenium catalysed dehydrogenation of alcohols

The oxidation of alcohols has been achieved using Grubbs’ catalyst or a ruthenium p-cymene complex without the presence of an added oxidant.     

Highly selective synthesis of catalytically active monodisperse rhodium nanocubes

Monodisperse sub-10 nm Rh nanocubes were synthesized with high selectivity (>85%) by a seedless polyol method. The {100} faces of the Rh NCs were effectively stabilized by chemically adsorbed Br- ions from trimethyl(tetradecyl)ammonium bromide (TTAB). This simple one-step polyol route can be readily applied to the preparation of Pt and Pd nanocubes. Moreover, the organic molecules of PVP and TTAB that encapsulated the Rh nanocubes did not prevent catalytic activity for pyrrole hydrogenation and CO oxidation.     

由长链醇选择性氧化制备香料(英文)

The activity and the selectivity of Ru and Pt based carbon catalysts in the selective oxidation of long-chain aliphatic alcohols (C8, C10, C12) have been investigated. Ru/AC and Pt/AC always showed good initial activity, however deactivation phenomena rapidly depressed the catalytic per-formance of the catalysts. These phenomena can be limited by modification of Ru/AC and Pt/AC with Au improving the durability of the catalyst. Ru/AC and AuRu/AC showed good selectivity to the corresponding aldehyde (95%) making these catalysts promising for fragrances manufacturing. The advantage in using Au modified catalyst lies on the easier regeneration procedure com-pared to the one necessary for Ru/AC. Pt /AC and AuPt/AC showed a lower selectivity to aldehyde promoting the formation of the acid and the ester formation respectively. The addition of water in the solvent system speeds up the reaction rate but drastically decreased the selectivity to aldehyde especially in the case of Pt based catalysts.     

Fast selective oxidation of alcohols under solvent-free conditions

A combination of acetic anhydride, H₂SO₄-nano silica, wet-SiO₂ (60 %), and K₂Cr₂O₇ as a new oxidizing system for the selective oxidation of different types of alcohols to the corresponding aldehydes and ketones at room temperature under solvent-free conditions is introduced. Mild reaction conditions, high yields of the products, short reaction time, no further oxidation to the corresponding carboxylic acid, and easy work-up make this new system a useful method for oxidizing alcohols.     

Promoting gold nanocatalysts in solvent-free selective aerobic oxidation of alcohols

A trace amount of metal carbonate, acetate or borate significantly boosts gold nanocatalysts in selective aerobic oxidation of alcohols under mild solvent-free conditions.     

Oxidant-dependent selective oxidation of alcohols utilizing multinuclear copper-triethanolamine complexes

Multinuclear Cu(II)-triethanolamine complexes were employed as catalysts for the selective oxidation of primary and secondary alcohols using tert-butylhydroperoxide (TBHP) and O₂/2,2′,6,6′-tetramethylpiperidinyl-1-oxyl (TEMPO) system, respectively. The catalytic performances, especially in terms of selectivities, were oxidant-dependent in forming the corresponding carbonyl compounds as the major products. Excellent selectivities and moderate to good yields were obtained for the transformation of secondary alcohols to ketones in the case of TBHP and also for the conversion of benzylic primary alcohols to aldehydes in the case of O₂/TEMPO system.     

A new method for the selective oxidation of allylic and benzylic alcohols

A new method is described for the selective oxidation of allylic or benzylic alcohols, in the presence of saturated alcohols, using trimethylamine-N-oxide in the presence of an iron carbonyl.     

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.     

分子氧选择性氧化醇类的研究进展

综述了分子氧化剂的醇类液相催化氧化的新进展。分别介绍了均相催化、水/有机两相催化、氟两相催化和液固多相催化体系。重点讨论了精细有机合成中有广泛应用前景的绿色氧化方法。预测了均相催化剂的多相化是今后工业化发展的趋势。     

A novel approach to selective oxidation of gaseous hydrocarbons

Selective oxidation of hydrocarbons can be performed by some microorganisms possessing monooxygenase activity. Biocatalytic activities of some strains of methanotrophic bacteria (which utilize methane as a sole source of carbon and energy for growth) were investigated in the reactions of partial oxidation of methane and propylene. Formation of commercially valuable oxy-products (methanol, epoxide) occurred with 100% selectivity under the mild reaction conditions studied.

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Cerium catalyzed selective oxidation of secondary alcohols in the presence of primary ones

The combination of (N₄₂Ce(NO₃)6-NaBrO₃ or CE(SO₄)₂·2H₂SO₄-NaBrO₃ has been found to be effective for the title selective oxidation.     

Productive utilization of chlorobenzene: palladium-catalyzed selective oxidation of alcohols

[reaction: see text] The palladium/ligand-catalyzed activation of chlorobenzene provides a general, efficient, and functional group friendly method for the selective oxidation of alcohols to carbonyl compounds.     

Monitoring in situ catalytically active states of Ru catalysts for different methanol oxidation pathways

One of the prerequisites for the detailed understanding of heterogeneous catalysis is the identification of the dynamic response of the catalyst surface under variable reaction conditions. The present study of methanol oxidation on different model Ru pre-catalysts, performed approaching the realistic catalytic reaction conditions, provides direct evidence of the significant effect of reactants' chemical potentials and temperature on the catalyst surface composition and the corresponding catalytic activity and selectivity. The experiments were carried out for three regimes of oxygen potentials in the 10(-1) mbar pressure range, combining in situ analysis of the catalyst surface by synchrotron-based photoelectron core level spectroscopy with simultaneous monitoring of the products released in the gas phase by mass spectroscopy. Metallic Ru with adsorbed oxygen and transient 'surface oxide', RuO(x), with varying x have been identified as the catalytically active states under specific reaction conditions, favouring partial or full oxidation pathways. It has been shown that the composition of catalytically active steady states, exhibiting different activity and selectivity, evolves under the reaction conditions, independent of the crystallographic orientation and the initial pre-catalyst chemical state, metallic Ru or RuO(2).     

Hydroxyapatite-supported palladium nanoclusters: a highly active heterogeneous catalyst for selective oxidation of alcohols by use of molecular oxygen

Treatment of a stoichiometric hydroxyapatite (HAP), Ca10(PO4)6(OH)2, with PdCl2(PhCN)2 gives a new type of palladium-grafted hydroxyapatite. Analysis by means of powder X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), energy-dispersive X-ray (EDX), IR, and Pd K-edge X-ray absorption fine structure (XAFS) proves that a monomeric PdCl2 species is chemisorbed on the HAP surface, which is readily transformed into Pd nanoclusters with a narrow size distribution in the presence of alcohol. Nanoclustered Pd0 species can effectively promote the alcohol oxidation under an atmospheric O2 pressure, giving a remarkably high turnover number (TON) of up to 236,000 with an excellent turnover frequency (TOF) of approximately 9800 h(-1) for a 250-mmol-scale oxidation of 1-phenylethanol under solvent-free conditions. In addition to advantages such as a simple workup procedure and the ability to recycle the catalyst, the present Pd catalyst does not require additives to complete the catalytic cycle. The diameters of the generated Pd nanoclusters can be controlled upon acting on the alcohol substrates used. Oxidation of alcohols is proposed to occur primarily on low-coordination sites within a regular arrangement of the Pd nanocluster by performing calculations on the palladium crystallites.     

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.     

The efficient and selective oxidation of alcohols with zeolite NaY-supported sodium ruthenate

Primary and internal alcohols are efficiently oxidised to their corresponding oxidation products at room temperature by a newly synthesized zeolite NaY-supported sodium ruthenate. Advantages of this system include simple catalyst removal and product isolation, in addition to easy recycling of this catalyst.     

Ligand-promoted dehydrogenation of alcohols catalyzed by Cp*Ir complexes. A new catalytic system for oxidant-free oxidation of alcohols

[reaction: see text] An efficient catalytic system for oxidant-free oxidation of alcohols has been developed. A new Cp*Ir catalyst bearing a 2-hydroxypyridine ligand has been designed on the concept of "ligand-promoted dehydrogenation". Various secondary alcohols can be dehydrogenatively oxidized to ketones under neutral conditions with high turnover numbers by using the new Cp*Ir catalyst.