Recent Advances in Immobilized Metal Catalysts for Environmentally Benign Oxidation of Alcohols

Matsumoto, Tsutomu; Ueno, Masaharu; Wang, Naiwei; Kobayashi, Shū

doi:10.1002/asia.200700359

Cited by 291 publications

(124 citation statements)

References 170 publications

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“…X-ray structure of (R)-1 with ellipsoids plotted at the 50% probability level, and H atoms and dichloromethane solvent omitted for clarity. Selected bond lengths: Cu1-O2 = 1.898(2), Cu1-O3 a = 1.936(2), Cu1-N1 = 1.937(2), Cu1-O1 = 1.9613 (19), Cu2-O4 = 1.869(2), Cu2-O3 = 1.903(2), Cu2-N2 = 1.919(2), Cu2-O1 = 1.9362(18) Å. Symmetry code: a = -x, y, -z. refined to 0.030 (9). The complete molecular cluster without the solvated dichloromethane is depicted in Fig.1 and relevant bond lengths given in the caption are unexceptional.…”

Section: Synthesis and Structural Descriptionmentioning

confidence: 99%

Chiral tetranuclear and dinuclear copper(ii) complexes for TEMPO-mediated aerobic oxidation of alcohols: are four metal centres better than two?

et al. 2014

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ARTICLE This journal is © The Royal Society of Chemistry 2013J. Name., 2013, 00, 1-3 | 1 The one-pot reaction of 3,5-di-tert-butyl-2-hydroxybenzaldehyde, (R)-2-aminoglycinol and Cu(OAc)2·2H2O in a 1:1:1 ratio in the presence of triethylamine led to the isolation of X-ray quality crystals of the chiral complex (R)-1 in high yield. The single crystal structure of (R)-1 reveals a tetranuclear copper(II) complex that contains a {Cu4(μ-O)2(μ3-O)2N4O4} core. A reaction using (1S,2R)-2-amino-1,2-diphenylethanol as precursor under the same conditions generated the chiral complex (S,R)-2; its structure was determined by single crystal X-ray crystallography and was found to contain a {Cu2(μ-O)2N2O2} core. Both (R)-1 and (S,R)-2 have been used for catalytic aerobic oxidation of benzylic alcohols in combination with the TEMPO (2,2,6,6-tetramethylpiperidinyl-1-oxyl) radical. (R)-1 selectively catalyses the conversion of various aromatic primary alcohols to the corresponding aldehydes with high yields (99%) and TONs (up to 770) in the air, while (S,R)-2 exhibits less promising catalytic performance under the same reaction conditions. The role of the cluster structures in (R)-1 and (S,R)-2 in controlling the reactivity towards aerobic oxidation reactions is discussed. IntroductionThe oxidation of alcohols to carbonyl compounds is an important transformation in synthetic organic chemistry and extensive efforts have been focused on the development of atom-economic oxidation methodologies for such reactions. [1][2][3][4] Amongst the protocols developed to date, catalytic aerobic oxidation has proven to be especially efficient and valuable by virtue of the use of a low-loaded, low-cost catalyst and molecular oxygen from the air. [5][6][7][8][9][10] In the past two decades, copper-catalysed, TEMPO (2,2,6,6-tetramethylpiperidinyl-1-oxyl) mediated aerobic oxidation has been the most popular choice of catalyst systems since the pioneering work of Semmelhack and coworkers in 1984. These authors utilized a CuCl/TEMPO system in DMF (N,N-dimethylformamide) to furnish the aerobic oxidation of benzylic and allylic alcohols. 11 Recent progress indicates that both Cu(I) and Cu(II) complexes with a N,N-or N,O-ligands in combination with TEMPO could be efficient catalysts or catalyst precursors for the aerobic oxidation of various alcohols, and of particular note is a highly efficient copper/2,2'-bipyridine/TEMPO system developed by the Stahl group. 12-17 However, the types of organic ligands exploited in the copper catalyst systems are still limited and the structures of copper catalysts involved in the catalytic process are rarely explored. [17][18][19][20] The construction of metal-organic cluster compounds through self-assembly of predesigned ligands with appropriate metal ions is a prime research topic [21][22][23][24][25] Herein, we report the one-pot syntheses and crystal structures of two tetranuclear and dinuclear copper(II) complexes resulting from the in situ synthesis of chiral Schiff base ligands (Scheme 1), and their catalytic ap...

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Section: Synthesis and Structural Descriptionmentioning

confidence: 99%

Chiral tetranuclear and dinuclear copper(ii) complexes for TEMPO-mediated aerobic oxidation of alcohols: are four metal centres better than two?

et al. 2014

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“…Systematic studies on the effects of metal (Pt, Pd, Au, Ag), Ag particle size, support oxides (CeO2, ZrO2, Al2O3, SiO2), and additives (13 kinds of metal salts) show four important factors required to achieve selective N-alkylation of anilines: (1) metal with weak metal-hydrogen bond energy (i.e. Ag), (2) smaller size of Ag cluster, (3) the support having both acidic and basic sites (i.e. Al2O3), and (4) additives with high Lewis acidity (Fe III salt).…”

Section: N-alkylation Of Anilines With Alcoholsmentioning

confidence: 99%

Silver Cluster Catalysts for Green Organic Synthesis

Shimizu

Satsuma

2011

J. Jpn. Petrol. Inst.

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Development of platinum-group-metal (PGM)-free catalysts for green chemical synthesis is an important topic in synthetic catalysis, because PGM will soon be in short supply in the near future. Our group has paid attention to the catalytic functions of Ag clusters. Here, we summarize our recent work on size-and support-specific catalysis of Ag clusters for green organic synthesis. Ag clusters supported on Al2O3 act as effective heterogeneous catalysts for (1) oxidant-free dehydrogenation of alcohols to carbonyl compounds, (2) coupling of alcohols with amines to form amides and H2, (3) N-alkylation of anilines with alcohols, (4) C _ C cross-coupling reaction of alcohols, (5) selective hydrogenation of nitroaromatics, and (6) direct synthesis of N-substituted anilines from nitroaromatics and alcohols. To establish a catalyst design concept, effects of Ag particle size and acid-base character of support oxides are investigated. The structure-activity relationships for all reactions show similar tendencies; metallic Ag clusters with smaller size and acid-base bifunctional nature of the support oxide are preferable. We propose that cooperation between coordinatively unsaturated Ag sites of Ag clusters and acidbase pair sites at the metal-support interface is a key concept for the design of Ag cluster catalysts for the above reactions.

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“…Another issue arises, particularly in a large-scale oxidation, associated with safety, environmental and economical reasons: toxic, harmful reagents are used; rather harsh conditions are often required, spurring chemists to develop ecologically more sustainable methods. [4][5][6][7][8][9][10][11] In recent years, a stable class of nitroxyl radicals, 12) as exemplified by 2,2,6,6-tetramethyl piperidinyl 1-oxyl (TEMPO) [(1); Chart 1], has extensively been used as a catalyst for oxidation of alcohols, because TEMPO is readily available from chemical suppliers at a reasonable price, and because the method allows the use of various safe bulk oxidants, thereby offering safe and extremely efficient oxidation of alcohols with considerable operational simplicity. [13][14][15][16][17][18][19][20][21][22][23][24][25] Today, TEMPOcatalyzed alcohol oxidation has high priority not only in academic laboratories, but also in the chemical industries, particularly in the pharmaceutical industry, as an efficient, mild, and environmentally acceptable method.…”

Section: Introductionmentioning

confidence: 99%

Discovery and Exploitation of AZADO: The Highly Active Catalyst for Alcohol Oxidation

Iwabuchi

2013

Chem. Pharm. Bull.

111

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The oxidation of primary and secondary alcohols to the corresponding aldehydes (or carboxylic acids) or ketones is a fundamental transformation in organic synthesis. Stable organic nitroxyl radicals as represented by 2,2,6,6-tetramethylpiperidine-1-oxyl (TEMPO) (1) have been used extensively to catalyze the oxidation of a number of alcohol substrates employing environmentally benign co-oxidants such as bleach (NaOCl) or PhI(OAc) 2 . Although TEMPO oxidation is better known as a method for selective oxidation of primary alcohols to the corresponding aldehydes, the TEMPO-based method is not very efficient for the oxidation of structurally hindered secondary alcohols. We designed and synthesized 2-azaadamantane N-oxyl [AZADO (

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Recent Advances in Immobilized Metal Catalysts for Environmentally Benign Oxidation of Alcohols

Cited by 291 publications

References 170 publications

Chiral tetranuclear and dinuclear copper(ii) complexes for TEMPO-mediated aerobic oxidation of alcohols: are four metal centres better than two?

Chiral tetranuclear and dinuclear copper(ii) complexes for TEMPO-mediated aerobic oxidation of alcohols: are four metal centres better than two?

Silver Cluster Catalysts for Green Organic Synthesis

Discovery and Exploitation of AZADO: The Highly Active Catalyst for Alcohol Oxidation

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