Photocatalytic oxidation of primary and secondary benzylic alcohols to carbonyl compounds catalyzed by H3PW12O40/SiO2 under an O2 atmosphere

Farhadi, Saeed; Afshari, Mozhgan; Maleki, Mansoureh; Babazadeh, Zaynab

doi:10.1016/j.tetlet.2005.10.019

Cited by 54 publications

(20 citation statements)

References 65 publications

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“…[11][12][13] Thus, for safety and environmental reasons, the development of clean catalytic processes with high conversions and selectivities and the use of innocuous solvents have been among the major goals of chemistry research during the last decade. [12] Heterogeneous photocatalysis has been used successfully for partial oxidation of alcohols in the gas [14,15] and liquid phase, using organic solvents, [16][17][18] affording high yields in some cases. In our investigations into the influence of the features of photocatalysts on the selective oxidation of aromatic alcohols to the corresponding aldehydes, organics-free water was used as solvent.…”

Section: Introductionmentioning

confidence: 99%

Titania Photocatalysts for Selective Oxidations in Water

et al. 2011

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Section: Introductionmentioning

confidence: 99%

Titania Photocatalysts for Selective Oxidations in Water

et al. 2011

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“…Hydrocarbons were oxidised in aqueous TiO 2 suspensions to obtain alcohols and carbonyl compounds in the presence of artificial irradiation, [6] whereas sunlight induced functionalisation of some heterocyclic bases in the presence of polycrystalline TiO 2 in water/acetonitrile solvents. [7] Selective oxidation of alcohols to the corresponding aldehydes and ketones was performed either in the gas phase [8] or in the liquid phase using acetonitrile as solvent, [9,10] in some cases affording high yields. Remarkably, attempts at performing the selective photocatalytic oxidation of alcohols to aldehydes in organic-free water are not reported in the literature, to the best of our knowledge.…”

Section: Introductionmentioning

confidence: 99%

Photocatalytic Selective Oxidation of 4‐Methoxybenzyl Alcohol to Aldehyde in Aqueous Suspension of Home‐Prepared Titanium Dioxide Catalyst

et al. 2007

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Abstract:The photocatalytic oxidation of 4-methoxybenzyl alcohol to p-anisaldehyde (PAA) was performed in water with organic-free suspensions of home-prepared and commercial titanium dioxide (TiO 2 ) catalysts. The nanostructured TiO 2 samples were synthesised by boiling aqueous solutions of titanium tetrachloride (TiCl 4 ), under mild conditions, for different times. The crystallinity increased with the boiling time. The 4-methoxybenzyl alcohol oxidation rate followed the same pattern but the highest yield (41.5 % mol) to PAA was found for the least crystalline sample, that showed a quantum efficiency of 0.116 %. A comparison with two commercial TiO 2 samples showed that all the home-prepared catalysts exhibited a PAA yield higher than that of commercial ones. The only by-products present were traces of 4-methoxybenzoic acid and aliphatic products, carbon dioxide being the other main oxidation product.

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“…A recent application of heterogenized POMs as photocatalysts for synthetic purposes concerns the oxidation of benzylic alcohols using sol-gel silica-encapsulated H 3 PW 12 O 40 . [23] The reaction takes place under an O 2 atmosphere that acts as a stoichiometric reoxidant catalyst, thereby allowing recycling and reuse of POM. Table 1 reports some reactivity results obtained with this system.…”

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Green Oxidation of Alcohols to Carbonyl Compounds by Heterogeneous Photocatalysis

Augugliaro

Palmisano

2010

ChemSusChem

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The selective conversion of alcohols to carbonyl compounds is essential for the preparation of fragrances, food additives, and many organic intermediates.[1] This transformation is carried out by catalytic processes that are of fundamental importance in synthetic chemistry.[2] Catalytic oxidation has long been carried out in environmentally harmful organic solvents (often chlorinated ones) at high temperatures and pressures by employing stoichiometric amounts of various inorganic oxidants, for example chromate and permanganate species, that play the role of oxygen donors. The latter oxidants are not only expensive and toxic but also produce large amounts of dangerous wastes, so that investigations have been concerned with substituting them for safer systems.In recent years, significant progress has been made in the development of effective catalytic processes for the aerobic oxidation of alcohols [3] with environmentally benign and inexpensive oxidants such as oxygen or air. Typically, the aerobic oxidation of alcohols involves the use of catalysts based on platinum-group metals and transition metal compounds. The latter are (1) transition metal complexes, which comprise a central metal atom and surrounding organic ligand(s); and (2) inorganic catalysts, mainly polyoxometalates [4,5] (POMs), typically oxides of molybdenum, tungsten, and vanadium. POMs are well-defined early transition metal-oxygen clusters with unique structural characteristics and catalytic properties. [6,7] Interestingly, many POMs share photochemical characteristics very similar to those of semiconductor photocatalysts, so that POMs represent the analogues of semiconductor metal oxides.[8] According to thermodynamics, an alcohol molecule with singlet electronic configuration cannot directly react with an unactivated dioxygen molecule, which has a triplet electronic configuration.[9] The working mechanism for all metal oxidation catalysts is that the metal atom mediates the electron transfer, and thereby induces the formation of singlet oxygen.In this respect, a wide range of homogeneous metal catalysts has been found capable to use molecular oxygen as the only oxidant. [10][11][12][13] For example, a water-soluble palladium(II) batho-phenanthroline complex has been used as catalyst at a pressure of 30 bar and a temperature of 373.16 K for the aerobic oxidation of a wide range of alcohols to aldehydes, ketones, and carboxylic acids in a biphasic water/alcohol system.[14] The alcohol conversion was almost complete and the yield of carbonyl compounds was in the range 79-90 %, depending on the substrate.The use of homogeneous catalysts, however, offers obvious disadvantages over heterogeneous systems with respect to ease of handling and catalyst recycling. A wide range of supported platinum and palladium catalysts has long been reported to exhibit high catalytic performance in the oxidation of alcohols.[15-17] Au/Pd-TiO 2 catalysts showing high turnover frequencies (up to 270 000 turnovers per hour) have been also proposed.[18] These catalysts, u...

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Photocatalytic oxidation of primary and secondary benzylic alcohols to carbonyl compounds catalyzed by H3PW12O40/SiO2 under an O2 atmosphere

Cited by 54 publications

References 65 publications

Titania Photocatalysts for Selective Oxidations in Water

Titania Photocatalysts for Selective Oxidations in Water

Photocatalytic Selective Oxidation of 4‐Methoxybenzyl Alcohol to Aldehyde in Aqueous Suspension of Home‐Prepared Titanium Dioxide Catalyst

Green Oxidation of Alcohols to Carbonyl Compounds by Heterogeneous Photocatalysis

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