Catalytic Aerobic Oxidation Of Alcohols Research Articles

Synthesis and Tuning of Gold Nanoparticles Supported on Polymorphic Semicrystalline Nanoporous Polymer for Catalytic Aerobic Oxidation of Alcohols

AbstractThe wide and complex tunability of gold nanoparticles (AuNPs) supported on nanoporous, semicrystalline, and polymorphic polymer matrices consisting of syndiotactic polystyrene (sPS) or multiblock syndiotactic polystyrene‐co‐cis‐1,4 poly(butadiene) (sPSB) is herein described and correlated with the performances in aerobic oxidation of (±)‐1‐phenylethanol. Impregnation or deposition‐impregnation synthetic methods yielded AuNPs of middle size (10–20 nm) on the surface of polymer grains. The co‐precipitation method leads to small AuNPs (4–5 nm) homogenously dispersed in the support with quantitative entrapment of the gold. Thermal or solvent annealing afforded modifications of polymer crystalline phase and AuNPs morphology. The annealing with chloroform/water mixture increases the crystallinity of the nanoporous forms and converts compact γ and β phases into the nanoporous ϵ and δ phases. The thermal treatment of the AuNPs‐sPS(B) catalysts afford defective NPs with enhanced catalytic activity. The solvent‐induced formation of the nanoporous forms improves permeability to solvents and reactants and, in turn, the catalytic properties.

Hemilabile Amine-Functionalized Efficient Azo-Aromatic Cu-Catalysts Inspired by Galactose Oxidase: Impact of Amine Sidearm on Catalytic Aerobic Oxidation of Alcohols.

A series of azo-aromatic copper(II) complexes, [1a-g] and a Cu(I) complex, [1h], with varying amine-functionalized hemilabile pincer-like [HL1-3] and [L1,2], methyl-substituted azo [L3], and imine [L4] ligands, were synthesized and characterized. These complexes were investigated for aerobic oxidation of a variety of aromatic alcohols in the presence of 2.0 mol % precatalysts [1a-g], cobaltocene (2.0 mol %), N-methyl imidazole (NMI) (8.0 mol %), and TEMPOH (2.0 mol %) at room temperature. The Cu(I) complex (1h) acted as a catalyst in the absence of cobaltocene. To understand the mechanism, detailed experimental and theoretical studies have been performed with the representative complex [1a], which has suggested a new kind of mechanism involving a Cu(II)/Cu(I) redox couple. Cobaltocene acts as a reductant to [1a] to generate a Cu(I) complex, which activates dioxygen in the presence of NMI. TEMPOH transfers a hydrogen atom to the activated dioxygen with the generation of TEMPO•, which further participates in α-C-H bond activation in the Cu(II)-alkoxide intermediate in an intermolecular fashion in the catalytic cycle. The amine sidearm in the ligand backbone of the complexes has a significant role in catalytic activity. Complexes with amine sidearms are more effective than complexes without them. Moreover, the aliphatic secondary amine sidearm is more efficient among the amine sidearm than the aromatic secondary amine and tertiary amines. The amine sidearm that remained coordinated to the Cu(II) center is hemilabile, and it facilitates alcohol coordination in the catalytic process. Alcohol coordination was the rate-limiting step, and it was supported by the isotope effect study on benzyl alcohol, substitution effect on the amine moiety of the ligands, and DFT calculation. The hemilabile amine sidearm of the coordinated ligand also acted as a base in deprotonating the alcoholic O-H proton and acted as an acid in releasing H2O2 during the catalysis.

A “universal” catalyst for aerobic oxidations to synthesize (hetero)aromatic aldehydes, ketones, esters, acids, nitriles, and amides

<h2>Summary</h2> Functionalized (hetero)aromatic compounds are indispensable chemicals widely used in basic and applied sciences. Among these, especially aromatic aldehydes, ketones, carboxylic acids, esters, nitriles, and amides represent valuable fine and bulk chemicals, which are used in chemical, pharmaceutical, agrochemical, and material industries. For their synthesis, catalytic aerobic oxidation of alcohols constitutes a green, sustainable, and cost-effective process, which should ideally make use of active and selective 3D metals. Here, we report the preparation of graphitic layers encapsulated in Co-nanoparticles by pyrolysis of cobalt-piperazine-tartaric acid complex on carbon as a most general oxidation catalyst. This unique material allows for the synthesis of simple, functionalized, and structurally diverse (hetero)aromatic aldehydes, ketones, carboxylic acids, esters, nitriles, and amides from alcohols in excellent yields in the presence of air.

A Copper(I) Complex with Two Unpaired Electrons, Synthesised by Oxidation of a Copper(II) Complex with Two Redox-Active Ligands.

Two homoleptic copper(II) complexes [Cu(L1)2] and [Cu(L2)2] with anionic redox‐active ligands were synthesised, one with urea azine (L1) and the other with thio‐urea azine (L2) ligands. One‐electron oxidation of the complexes initiates an unprecedented redox‐induced electron transfer process, leading to monocationic copper(I) complexes [Cu(L1)2]+ and [Cu(L2)2]+ with two oxidised ligands. While [Cu(L1)2]+ is best described as a CuI complex with two neutral radical ligands that couple antiferromagnetically, [Cu(L2)2]+ is a CuI complex with two clearly different ligand units in the solid state and with a magnetic susceptibility close to a diamagnetic compound. Further one‐electron oxidation of the complex with L1 ligands results in a dication [Cu(L1)2]2+, best described as a CuI complex with a twofold oxidised, monocationic ligand and a neutral radical ligand. The stability in at least three redox states, the accumulation of spin density at the ligands and the facile ligand‐metal electron transfer make these complexes highly attractive for a variety of applications; here the catalytic aerobic oxidation of alcohols to aldehydes is tested.

Silver and palladium nanoparticles anchored to the core-shell Fe3O4@SiO2@Al2O3 for catalytic aerobic oxidation of alcohols and apoptotic induction on MCF-7 cells

Silver and palladium nanoparticles anchored to the core–shell Fe3O4@SiO2@Al2O3 were successfully synthesized based on MIL(Al)96 MOF. The nanocomposites, 15–20 nm in size, exhibited high catalytic activity for selective aerobic oxidation of alcohols (even aliphatic alcohols) to the corresponding carbonyl compounds at room temperature without addition of any other additives. In this regard, the Fe3O4@SiO2@Al2O3/Pd,Ag exhibited more catalytic activity than the others. The cytotoxic effect of nanocomposites was tested in-vitro against MCF-7 human breast cancer cells by MTT assay. The results showed that all synthesized nanocomposites will be promising and potential as anticancer agents, with sample Fe3O4@SiO2@Al2O3 being the most cytotoxic after 24 and 48 h. Also, the obtained nanocomposites could induce apoptosis in breast cancer cell line (MCF-7) and the ability of induce apoptosis was in the following order: Fe3O4@SiO2@Al2O3@Ag > Fe3O4@SiO2@Al2O3 > Fe3O4@SiO2@Al2O3@Pd,Ag > Fe3O4@SiO2@Al2O3@Pd.

Dioxygen Activation by Internally Aromatic Metallacycle: Crystallographic Structure and Mechanistic Investigations.

SummaryMononuclear metal-peroxo species are invoked as the key intermediates in metalloenzymatic or synthetic catalysis. However, either transience or sluggishness reactivity of synthetic analogs of metal-peroxo species impedes our understanding of oxygen activation mechanism. Herein, we designed and characterized a dioxygen-derived mononuclear osmium-peroxo complex, in which the peroxo ligand is stabilized by internally aromatic metallacycle. We demonstrate that the osmium-peroxo species shows catalytic activity toward promoterless alcohol dehydrogenations. Furthermore, computational studies provide a new mechanism for the osmium-peroxo-mediated alcohol oxidation, starting with the concerted double-hydrogen transfer and followed by the generation of osmium-oxo species. Interestingly, the internally aromatic metallacycle also plays a vital role in catalysis, which mediates the hydrogen transfer from osmium center to the distal oxygen atom of Os–OOH moiety, thus facilitating the Os–OOH→Os=O conversion. We expect that these insights will advance the development of aromatic metallacycle toward aerobic oxidation catalysis.

Catalytic Aerobic Oxidation of Alcohols by Copper Complexes Bearing Redox-Active Ligands with Tunable H-Bonding Groups.

In this research article, we describe the structure, spectroscopy, and reactivity of a family of copper complexes bearing bidentate redox-active ligands that contain H-bonding donor groups. Single-crystal X-ray crystallography shows that these tetracoordinate complexes are stabilized by intramolecular H-bonding interactions between the two ligand scaffolds. Interestingly, the Cu complexes undergo multiple reversible oxidation-reduction processes associated with the metal ion (CuI, CuII, CuIII) and/or the o-phenyldiamido ligand (L2-, L•-, L). Moreover, some of the CuII complexes catalyze the aerobic oxidation of alcohols to aldehydes (or ketones) at room temperature. Our extensive mechanistic analysis suggests that the dehydrogenation of alcohols occurs via an unusual reaction pathway for galactose oxidase model systems, in which O2 reduction occurs concurrently with substrate oxidation.

DFT and experimental study of nitrosyl carboxylate palladium clusters Pd4(NO)2(RCO2)6 as catalysts for aerobic oxidation of alcohols

Possible activation pathways for palladium nitrosyl carboxylate complexes Pd4 (μ-NO)2 (μ-RCO2)6 in reaction of catalytic aerobic oxidation of alcohols are reported. The study was carried out using scalar-relativistic DFT calculations for the system palladium nitrosyl acetate (RCH3) + methanol. Exchange-correlation functional PBE was found to be the best choice in terms of accuracy and time for calculations. The main pathway includes dissociation of starting 4-nuclear molecule into binuclear species Pd2(NO) (CH3CO2)3, where nitrosyl group keeps bridging coordination mode. Experimental studies showed that palladium nitrosyl acetate (RCH3) and nitrosyl pivalate (RCMe3) are moderately active catalysts for aerobic oxidation of benzylic alcohol, (E)-2-hexen-1-ol, (−)-menthol, trans-1,3-diphenyl-2-propen-1-ol and dodecanol-1. The addition of pyridine substantially improved the catalysts performance.

Ordered nanoporous lyotropic liquid crystal polymer resin for heterogeneous catalytic aerobic oxidation of alcohols.

An ordered, nanoporous, TEMPO-based polymer resin formed from lyotropic liquid crystal monomers catalyzes the hetereogeneous oxidation of alcohols with high activity and substrate size selectivity under transition-metal-free, aerobic conditions.

Aerobic alcohol oxidation and oxygen atom transfer reactions catalyzed by a nonheme iron(ii)-α-keto acid complex.

α-Ketoglutarate-dependent enzymes catalyze many important biological oxidation/oxygenation reactions. Iron(iv)-oxo intermediates have been established as key oxidants in these oxidation reactions. While most reported model iron(ii)-α-keto acid complexes exhibit stoichiometric reactivity, selective oxidation of substrates with dioxygen catalyzed by biomimetic iron(ii)-α-keto acid complexes remains unexplored. In this direction, we have investigated the ability of an iron(ii) complex [(TpPh,Me)FeII(BF)] (1) (TpPh,Me = hydrotris(3-phenyl-5-methylpyrazolyl)borate and BF = monoanionic benzoylformate) to catalyze the aerobic oxidation of organic substrates. An iron-oxo oxidant, intercepted in the reaction of 1 with O2, selectively oxidizes sulfides to sulfoxides, alkenes to epoxides, and alcohols to the corresponding carbonyl compounds. The oxidant from 1 is able to hydroxylate the benzylic carbon of phenylacetic acid to afford mandelic acid with the incorporation of one oxygen atom from O2 into the product. The iron(ii)-benzoylformate complex oxidatively converts phenoxyacetic acids to the corresponding phenols, thereby mimicking the function of iron(ii)-α-ketoglutarate-dependent 2,4-dichlorophenoxyacetate dioxygenase (TfdA). Furthermore, complex 1 exhibits catalytic aerobic oxidation of alcohols and oxygen atom transfer reactions with multiple turnovers.

ChemInform Abstract: Catalytic Aerobic Oxidation of Alcohols Using Recoverable IAPNO α‐Hydrogen Nitroxyl Radicals.

AbstractConditions for the oxidation of primary aliphatic, benzylic, allylic, and propargylic alcohols and secondary benzylic alcohols including benzoin in the presence of newly developed stable α‐hydrogen nitroxyl radicals as the catalyst are elaborated.

Catalytic Aerobic Oxidation of Alcohols using Recoverable IAPNO α‐Hydrogen Nitroxyl Radicals

Abstractα‐Hydrogen‐substituted nitroxyl radicals are of considerable interest as catalysts for oxidation and polymerization, but are usually inherently unstable. We report herein the catalytic activity of a new family of stable iso‐azaphenalene (IAPNO) α‐hydrogen nitroxyl radicals in the copper/bipyridine/N‐methylimidazole co‐catalyzed aerobic oxidation of alcohols. The nitroxyl radical Mes/TIPSO‐IAPNO (TIPSO=triisopropyloxy, IAPNO=isoazaphenalene N‐oxyl) displays higher activity than TEMPO in the oxidation of benzylic and allylic alcohols. Alkyl, benzyl, allyl, and propargyl alcohols are oxidized with yields up to 96 %. The readily prepared nitroxyl catalysts are recovered in 75–90 % yield after purification of the reaction mixture and are recycled.

Trinuclear Pd3O2 Intermediate in Aerobic Oxidation Catalysis

The activation of O2 is a key step in selective catalytic aerobic oxidation reactions mediated by transition metals. The bridging trinuclear palladium species, [(LPd(II))3(μ(3)-O)2](2+) (L=2,9-dimethylphenanthroline), was identified during the [LPd(OAc)]2(OTf)2-catalyzed aerobic oxidation of 1,2-propanediol. Independent synthesis, structural characterization, and catalytic studies of the trinuclear compound show that it is a product of oxygen activation by reduced palladium species and is a competent intermediate in the catalytic aerobic oxidation of alcohols. The formation and catalytic activity of the trinuclear Pd3O2 species illuminates a multinuclear pathway for aerobic oxidation reactions catalyzed by Pd complexes.

Trinuclear Pd3O2 Intermediate in Aerobic Oxidation Catalysis

AbstractThe activation of O2 is a key step in selective catalytic aerobic oxidation reactions mediated by transition metals. The bridging trinuclear palladium species, [(LPdII)3(μ3‐O)2]2+ (L=2,9‐dimethylphenanthroline), was identified during the [LPd(OAc)]2(OTf)2‐catalyzed aerobic oxidation of 1,2‐propanediol. Independent synthesis, structural characterization, and catalytic studies of the trinuclear compound show that it is a product of oxygen activation by reduced palladium species and is a competent intermediate in the catalytic aerobic oxidation of alcohols. The formation and catalytic activity of the trinuclear Pd3O2 species illuminates a multinuclear pathway for aerobic oxidation reactions catalyzed by Pd complexes.

Novel metal oxide nanocomposite of Au/CuO–ZnO for recyclable catalytic aerobic oxidation of alcohols in water

CuO–ZnO supported gold nanoparticle is introduced as a new, efficient, and recyclable catalyst for the aerobic oxidation of alcohols. The CuO–ZnO support was prepared by co-precipitation and Au nanoparticles were loaded on support by a deposition–precipitation method. The catalyst was characterized by XRD, BET surface area, FESEM, EDS and HRTEM techniques. A wide range of alcohols, including benzylic, primary and secondary alcohols are converted into the corresponding carbonyl derivatives. The experimental procedure with Au/CuO–ZnO catalyst is quite straightforward and the catalyst is recyclable up to 6 consecutive runs by simple filtration.

Catalytic Aerobic Oxidation of Alcohols with Pd@PMO-IL

Catalytic Aerobic Oxidation of Alcohols with Pd@PMO-IL

Highly Efficient, Organocatalytic Aerobic Alcohol Oxidation

5-Fluoro-2-azaadamantane N-oxyl (5-F-AZADO) realizes a simple, organocatalytic aerobic alcohol oxidation system that has a wide scope under mild conditions at ambient pressure and temperature and is weakly acidic and halogen- and transition-metal-free. The oxoammonium nitrate (5-F-AZADO(+)NO(3)(-)) works as a bifunctional catalyst of 5-F-AZADO and NO(x) that enables the catalytic aerobic oxidation of alcohols by itself (a metal-salt-free system).

ChemInform Abstract: Creation of a High‐Valent Manganese Species on Hydrotalcite and Its Application to the Catalytic Aerobic Oxidation of Alcohols.

AbstractA high‐valent Mn oxide species is synthesized on the surface of hydrotalcite by treatment of the corresponding Mn compound with KOH.

Creation of a high-valent manganese species on hydrotalcite and its application to the catalytic aerobic oxidation of alcohols

A high-valent Mn oxide species is successfully synthesized on the surface of hydrotalcite (Mn/HT-Ox), and is found to act as an efficient heterogeneous catalyst for the oxidation of alcohols using molecular oxygen as an oxidant.

Catalytic aerobic oxidation of allylic alcohols to carbonyl compounds under mild conditions

A new catalytic aerobic oxidation of alcohols to aldehydes under green conditions was developed (room temperature and pressure, water solution, open vials). The water-soluble platinum(II) tetrasulfophthalocyanine (PtPcS) catalyst showed the best selectivity for carbonyl derivatives, and in particular for α,β-unsaturated alcohols; the reactions are slow.