Oxidant Effect of H2O2 for the Syntheses of Quinoline Derivatives via One-Pot Reaction of Aniline and Aldehyde

A convenient one-pot method for the synthesis of substituted quinolines via the reaction of aniline and aldehyde in the presence of a Lewis acid (AlCl₃) and an oxidant (H₂O₂) has been developed. Hydrogen peroxide was found to promote the reaction by its function as a hydrogen hunter, hindering the formation of by-product N-alkylaniline. The effect of the oxidant on the yield and selectivity was studied. When the molar ratio of aniline, n-butyraldehyde, and H₂O₂ was 1:3:0.5 at 25 °C, the yield of 3-ethyl-2-propylquinoline was improved from 64% (reaction without H₂O₂) to 84% (with H₂O₂), and the quinoline selectivity was improved to almost 100%. Moreover, the reaction time was obviously reduced. The substituent effect was also investigated in this work.     

Mechanistic Studies on the Roles of the Oxidant and Hydrogen Bonding in Determining the Selectivity in Alkene Oxidation in the Presence of Molybdenum Catalysts

When the molybdenum oxo(peroxo) acetylide complex [CpMo(O? O)(O)C?CPh] is used as a catalyst for the oxidation of olefins, completely different product selectivity is obtained depending on the oxidant employed. When tert‐butyl hydroperoxide (TBHP, 5.5 M ) in dodecane is used as the oxidant for the oxidation of cyclohexene, cyclohexene oxide is formed with high selectivity. However, when H₂O₂ is used as the oxidant, the corresponding cis‐1,2‐diol is formed as the major product. Calculations performed by using density functional theory revealed the nature of the different competing mechanisms operating during the catalysis process and also provided an insight into the influence of the oxidant and hydrogen bonding on the catalysis process. The mechanistic investigations can therefore serve as a guide in the design of molybdenum‐based catalysts for the oxidation of olefins.     

Synthesis,characterization and catalytic activity of peripherally tetra‐substituted Co(II) phthalocyanines for cyclohexene oxidation

New 3,3‐diphenylpropoxyphthalonitrile (5) was obtained from 3,3‐diphenylpropanol (3) and 4‐nitrophthalonitrile (4) with K₂CO₃ in DMF at 50 °C. The novel cobalt(II) phthalocyanine complexes, tetrakis‐[2‐(1,4‐dioxa‐8‐azaspiro[4.5]dec‐8‐yl)ethoxy] phthalocyaninato cobalt(II) (2) and tetrakis‐(3,3‐diphenylpropoxy)phthalocyaninato cobalt(II) (6) were prepared by the reaction of the phthalonitrile derivatives 1 and 5 with CoCl₂ by microwave irradiation in 2‐(dimethylamino)ethanol for at 175 °C, 350 W for 7 and 10 min, respectively. These new cobalt(II)phthalocyanine complexes were characterized by spectroscopic methods (IR, UV–visible and mass spectroscopy) as well as elemental analysis. Complexes 2 and 6 are employed as catalyst for the oxidation of cyclohexene using tert‐butyl hydroperoxide (TBHP), m‐chloroperoxybenzoic acid (m‐CPBA), aerobic oxygen and hydrogen peroxide (H₂O₂) as oxidant. It is observed that both complexes can selectively oxidize cyclohexene to give 2‐cyclohexene‐1‐ol as major product, and 2‐cyclohexen‐1‐one and cyclohexene oxide as minor products. TBHP was found to be the best oxidant since minimal destruction of the catalyst, higher selectivity and conversion were observed in the products. Copyright © 2012 John Wiley & Sons, Ltd.     

Effective catalytic oxidation of alcohols and alkenes with monomeric versus dimeric manganese(II) catalysts and t‐BuOOH

Two new Mn(II) complexes, [Mn(C₆H₅COO)(H₂O)(phen)₂](ClO₄)(CH₃OH) ( 1 ) and [Mn₂(μ‐C₆H₅COO)₂(bipy)₄]?2(ClO₄) ( 2 ) (phen = 1,10‐phenanthroline; bipy = 2,2′‐bipyridine), were synthesized and characterized using UV–visible and infrared spectroscopies and single‐crystal X‐ray diffraction analyses. Complexes 1 and 2 have six‐coordinate octahedral geometry around the Mn(II) centre. Complex 1 is a monomer and consists of a deprotonated monodentate benzoate ligand together with two neutral bidentate amine ligands (phen) and a water molecule. Complex 2 has a dinuclear structure in which two Mn(II) ions share two carboxylate groups, adopting a two‐atom bridging mode, and two chelated bipy ligands. Both complexes catalyse the oxidation of alcohols and alkenes in a homogeneous catalytic system consisting of the Mn(II) complex and tert‐butyl hydroperoxide (TBHP) in acetonitrile. The system yields good to quantitative conversions of various alkenes and alcohols, such as styrene, ethylbenzene and cyclohexene to their corresponding ketones, and primary alcohols and 1‐octanol, 1‐heptanol, cyclohexanol, benzyl alcohols and cinnamyl alcohol to their corresponding aldehydes and carboxylic acids. Complexes 1 and 2 exhibit very high activity in the oxidation of cyclohexene to cyclohexanone (ca 80% selectivity) as the main product (ca 94% conversion in 1 h) and of cinnamyl alcohol to cinnamaldehyde (ca 64% selectivity) as the main product (ca 100% conversion in 0.5 h) with TBHP at 70°C in acetonitrile. In addition, optimum reaction conditions were also determined for benzyl alcohol with complexes 1 and 2 and TBHP. Copyright © 2016 John Wiley & Sons, Ltd.     

Synthesis,characterization and catalytic activity of novel Co(II) and Pd(II)‐perfluoroalkylphthalocyanine in fluorous biphasic system; benzyl alcohol oxidation

Tetrakis[heptadecafluorononyl] substituted phthalocyanine complexes were prepared by template synthesis from 4‐(heptadecafluorononyloxy)phthalonitrile with Co(CH₃COO)^·₂H₂O or PdCl₂ in 2‐N, N‐dimethylaminoethanol. The corresponding phthalonitrile was obtained from heptadecafluorononan‐1‐ol and 4‐nitrophthalonitrile with K₂CO₃ in DMF at 50 °C. The structures of the compounds were characterized by elemental analysis, FTIR, UV–vis and MALDI‐TOF MS spectroscopic methods. Metallophthalocyanines are soluble in fluoroalkanes such as perfluoromethylcyclohexane (PFMCH). The complexes were tested as catalysts for benzyl alcohol oxidation with tert‐butylhydroperoxide (TBHP) in an organic–fluorous biphasic system (n‐hexane–PFMCH). The oxidation of benzyl alcohol was also tested with different oxidants, such as hydrogen peroxide, m‐chloroperoxybenzoic acid, molecular oxygen and oxone in n‐hexane–PFMCH. TBHP was found to be the best oxidant for benzyl alcohol oxidation since higher conversion and selectivity were observed when this oxidant was used. Copyright © 2008 John Wiley & Sons, Ltd.     

Active control of catalysis and product selectivity by a fuel cell system

A new concept to control catalysis and catalytic reaction through partial oxidation of alkenes with O₂ is described. Oxidation of alkenes was studied by alkene/Pd-anode/H₃PO₄-electrolyte/cathode/O₂ fuel cell (FC). An idea based on electrocatalysis and electrochemical reactions to control reaction rates and product selectivity was proposed and proven through the oxidation of propylene, Wacker and π-allyl oxidation. The oxidation rate and the product selectivity to the Wacker and the π-allyl oxidations could be controlled by changing electrode potentials. We could active control oxidation states of Pd on the anode, Pd(II) or Pd(0), during the oxidation from outer circuit. The oxidation states of Pd on the anode decided the product selectivity.     

Efficient Oxidation of Cyclohexane over Bulk Nickel Oxide under Mild Conditions

Nickel oxide powder was prepared by simple calcination of nickel nitrate hexahydrate at 500 °C for 5 h and used as a catalyst for the oxidation of cyclohexane to produce the cyclohexanone and cyclohexanol—KA oil. Molecular oxygen (O₂), hydrogen peroxide (H₂O₂), t-butyl hydrogen peroxide (TBHP) and meta-chloroperoxybenzoic acid (m-CPBA) were evaluated as oxidizing agents under different conditions. m-CPBA exhibited higher catalytic activity compared to other oxidants. Using 1.5 equivalent of m-CPBA as an oxygen donor agent for 24 h at 70 °C, in acetonitrile as a solvent, NiO powder showed exceptional catalytic activity for the oxidation of cyclohexane to produce KA oil. Compared to different catalytic systems reported in the literature, for the first time, about 85% of cyclohexane was converted to products, with 99% KA oil selectivity, including around 87% and 13% selectivity toward cyclohexanone and cyclohexanol, respectively. The reusability of NiO catalyst was also investigated. During four successive cycles, the conversion of cyclohexane and the selectivity toward cyclohexanone were decreased progressively to 63% and 60%, respectively, while the selectivity toward cyclohexanol was increased gradually to 40%.     

Catalytic reactivity of Cr/SiO2 in the liquid phase oxidation of cyclohexanol by tert-butyl hydroperoxide

Silica supported chromium is a heterogeneous, active and selective catalyst for the liquid phase oxidation of cyclohexanol by tert-butyl hydroperoxide (TBHP) in the presence or absence of oxygen. It is also active for the decomposition of TBHP. The reactivity at 70ºC and atmospheric pressure is higher than over other catalysts and the cyclohexanone selectivity is 100%.     

Catalytic cross-coupling of aniline by pyrite and dissolved oxygen under alkaline conditions

Pyrite catalyzes oxidation of various organic contaminants by dissolved oxygen (DO) under acidic conditions; however, the catalytic mechanism under alkaline conditions is still not clear. In this study, we observe increased oxidation rates of aniline with increasing pHs (7.0–11.0). Electron paramagnetic resonance (EPR) analysis and quenching experiments rule out contributions of •OH, O₂^•−, ¹O₂ and Fe (IV) to aniline oxidation and suggest that the Fe (III)–OOH peroxo and/or H₂O₂ are the primary oxidative species in the oxidation of aniline at pH 11.0. In addition, 200 mg L⁻¹ H₂O₂ does not apparently increase the oxidation rate of aniline, which also rules out the predominant contribution of the produced H₂O₂ to aniline oxidation. We therefore suggest that the Fe (III)–OOH peroxo is indeed the primary oxidative species in the pyrite–DO system under alkaline conditions. Analyses of solid total organic carbon (TOC), gas chromatography–mass spectrometry and Fourier-transform infrared spectroscopy further reveal that more than 83.3% aniline has been polymerized to polyaniline, instead of being mineralized into CO₂ and H₂O, indicating that H-abstraction from aniline by the Fe (III)–OOH peroxo is an important step in the oxidation of aniline under alkaline conditions. This study provides new insight into the oxidative species in the pyrite–DO system, and opens a new door for organic degradations under alkaline conditions.     

Simple one‐pot conversion of organic compounds by hydrogen peroxide activated by ruthenium(III) chloride: organic conversions by hydrogen peroxide in the presence of ruthenium(III)

The aromatic compounds p‐nitrobenzaldehyde, p‐hydroxybenzaldehyde, naphthalene, toluene, catechol, quinol, aniline and toluidine dissolved in aqueous acetic acid or aqueous medium were oxidized in quantitative to good yields by 50% H₂O₂ in the presence of traces of RuCl₃ (～10^?8 mol; substrate/catalyst ratio 1488:1 to 341 250:1). Conditions for highest yields, in the most economical way, were obtained. Higher catalyst concentrations decrease the yield. Oxidation in aromatic aldehydes is selective at the aldehydic group only. In the case of hydrocarbons, oxidation results in the introduction of a hydroxyl group with >85% (in the case of toluene) selectivity for the ortho position. Formation of low‐molecular‐weight polyaniline was reduced to 10%, along with 90% formation of higher molecular weight polyaniline. In this new, simple and economical method, which is environmentally safe and requires less time, oxo‐centered carboxylate species of ruthenium(III) in acetic acid medium and hydrated ruthenium(III) chloride in aqueous medium probably catalyze the oxidation. Copyright © 2005 John Wiley & Sons, Ltd.     

The catalytic reduction of nitrobenzene at the [MoVIO2(O2CC(S)(C6H5)2)2]2− complex intercalated in a Zn(II)–Al(III) layered double hydroxide host: A kinetic model for the molybdenum–pterin binding site in nitrate reductase

The heterogeneous reduction of nitrobenzene by thiophenol catalyzed by the dianionic bis(2‐sulfanyl‐2,2‐diphenylethanoxycarbonyl) dioxomolybdate(VI) complex, [Mo^VIO₂(O₂CC(S)(C₆H₅)₂)₂]²⁻, intercalated into a Zn(II)–Al(III) layered double hydroxide host [Zn_3−xAl_x(OH)₆]^x+, has been investigated under anaerobic conditions. Aniline was found to be the only product formed through a reaction consuming six moles of thiophenol for each mol of aniline produced. The kinetics of the system have been analyzed in detail. In excess of thiophenol, all reactions follow first‐order kinetics (ln([PhNO₂]/[PhNO₂]₀) = −k_appt) with the apparent rate constant k_app being a complex function of both initial nitrobenzene and thiophenol concentrations, as well as linearly dependent on the amount of solid catalyst used. A mechanism for this catalytic reaction consistent with the kinetic experiments as well as the observed properties of the intercalated molybdenum complex has thiophenol inducing the initial coupled proton–electron transfer steps to form an intercalated Mo^IV species, which is oxidized back to the parent Mo^VI complex by nitrobenzene via a two‐electron oxygen atom transfer reaction that yields nitrosobenzene. This mechanism is widespread in enzymatic catalysis and in model chemical reactions. The intermediate nitrosobenzene thus formed is reduced directly by excess thiophenol to aniline. The values of rate coefficients indicate that reduction of nitrobenzene proceeds much faster than proton‐assisted oxidation of thiophenol. This may account for the observation that the presence of protonic amberlite IR‐120(H) increases considerably the rate of the overall reaction catalyzed. Activation parameters in excess of the protonic resin and PhSH were ΔH^≠ = 80 kJ mol⁻¹ and ΔS^≠ = −70 J mol⁻¹ K⁻¹. The large negative activation entropy is consistent with an associative transition state. The present system is characterized by a well‐defined catalytic cycle with multiple‐turnovers reductions of nitrobenzene to aniline without appreciable deactivation. © 2001 John Wiley & Sons, Inc. Int J Chem Kinet 33: 212–224, 2001     

Selective and mild oxidation of sulfides to sulfoxides or sulfones using H2O2 and Cp′Mo(CO)3Cl as catalysts

Dialkyl, aryl-alkyl, benzylic, and benzothiophenic sulfides are selectively oxidized to sulfoxides or sulfones, with stoichiometric amounts of H₂O₂ (aq) or TBHP, in the presence of complexes Cp′Mo(CO)₃Cl, CpMoO₂Cl and the mesoporous material MCM-41-2 as catalysts. The use of the thianthrene 5-oxide (SSO) probe shows that CpMo(CO)₃Cl/H₂O₂ or TBHP are electrophilic oxidants (Xso ? 15). The same conclusion is drawn from competition experiments with a mixture of p-ClC₆H₄SCH₃ and C₆H₅SOCH₃.     

The Role of the −OH Groups within Mn12 Clusters in Electrocatalytic Water Oxidation

The formidable reactivity of the oxygen-evolving center near photosystem II is largely based on its protein environment that stabilizes it during catalysis. Inspired by this concept, the water-soluble Mn₁₂ clusters Mn₁₂O₁₂(O₂CC₆H₃(OH)₂)₁₆(H₂O)₄ (3,5DHMn₁₂) and Mn₁₂O₁₂(O₂CC₆H₃(OH)₃)₁₆(H₂O)₄ (3,4,5THMn₁₂) were developed as efficient electrocatalysts for water oxidation. In this work, the role of the −OH groups in the electrocatalytic process was explored by describing the structural and electrocatalytic properties of two new Mn₁₂ clusters, 3,4DHMn₁₂ and 2,3DHMn₁₂ , having one −OH group in the meta position relative to the benzoate-Mn moiety, and one at the para or ortho position, respectively. The Mn centers in 3,4DHMn₁₂ were discovered to have lower oxidation potential compared with those in 2,3DHMn₁₂ , and thus, 3,4DHMn₁₂ can catalyze water oxidation with higher rate and TON than 2,3DHMn₁₂ . Hence, the role of the −OH groups in the electrocatalysis was established, being involved in electronic stabilization of the Mn centers or in proton shuttling.     

A carboxylate-bridged Mn(II) compound with 6-methylanthranilate/bipy: oxidation of alcohols/alkenes and catalase-like activity

Abstract

A novel manganese compound, [Mn₂(μ_1,3-6-CH₃-2-NH₂C₆H₄COO)₂(bipy)₄](ClO₄)₂ (bipy = 2,2′-bipyridine), was synthesized and used as a catalyst precursor in the oxidation of alkenes and primary alcohols to corresponding aldehydes, ketones, and acids. The six-coordinate compound has a binuclear structure in which two Mn(II) ions adopt a syn-anti μ_1,3-bridging mode with two carboxylate groups and two chelated bipy ligands. The compound exhibits good activity in the oxidation of cyclohexene to 2-cyclohexene-1-one as the major product (93% conv. in 3 h, 79.3% selectivity) and of cinnamyl alcohol to cinnamaldehyde as the major product with 46% selectivity (100% conv. in 1.5 h) with tert-butyl hydroperoxide (TBHP) in acetonitrile at 70 °C. Furthermore, the catalase-like activity of the compound was studied in different solvents (acetonitrile, methanol, Tris-HCl buffer; TOF = 29,910 h^?1 in Tris-HCl buffer).     

Probable mechanism for alkane oxidation with H2O2 over VS-2

Metallosilicate zeolites containing Ti and V, TS-2 and VS-2, have been synthesized using tetrabutylammonium cation as the template. Although both Ti and V exist in zeolite framework in a highly dispersed state, V easily leaches by K₂CO₃ or H₂O₂ treatments in contrast to Ti. Spin trapping experiments and relative reactivity of linear/cyclic alkanes indicate that the oxidation of alkanes over TS-2 and VS-2 proceed by different mechanisms; it is conceivable that the oxidation occurs by way of the attack of ·OH species produced from the V species in the zeolite framework with H₂O₂.     

Catalytic Oxidative Cyclocondensation of o‐Aminophenols to 2‐Amino‐3H‐phenoxazin‐3‐ones

The catalytic oxidative cyclocondensation of the o‐aminophenols 1a–f was investigated. The oxidants used were air/laccase, H₂O₂/horseradish peroxidase, H₂O₂/ebselen (3), and TBHP/diphenyl diselenide 4. The products obtained were 2‐amino‐3H‐phenoxazin‐3‐one—questiomycin A, its derivative 2b, and cinnabarinic acid and actinocin (2c,d). Substrates with methyl groups at 4 and 5 positions of benzene ring were converted to different dihydrophenoxazinones 2g,h. Compounds having chlorine atoms at the same positions underwent oxidation to planar phenoxa-zinones 2e,f with elimination of one hydrochloride molecule.     

Selective Oxidation of Sulfides to Sulfoxides using H2O2 Catalyzed by p-Toluenesulfonic Acid (p-TsOH) Under Solvent-Free Conditions

Abstract

An efficient, chemoselective, and environmental friendly procedure for the oxidation of sulfides to sulfoxides is described. Various types of aromatic and aliphatic sulfides are selectively oxidized to sulfoxides in good to excellent yields using 30% H₂O₂ in the presence of catalytic amounts of a p-TsOH under solvent-free conditions at room temperature.     

Polyferroorganosiloxanes as catalysts of oxidation processes

Polyferroorganosiloxanes were studied as catalysts for homogeneous oxidation of alkanes by hydrogen peroxide tinder mild conditions. In the oxidation of cyclohexane the catalysts are characterized by high efficiency (conversion of hydrogen peroxide is 25%) and stability Kip to 80 cycles per gat NJ The min product of the oxidation W do presence a 2,4,6-tri-tert-btitylphenol is cyclohexanol (tip to 35% per H₂O₂).     

Hydrogen Peroxide-Responsive Triggers Based on Borinic Acids: Molecular Insights into the Control of Oxidative Rearrangement

Arylborinic acids represent new, efficient, and underexplored hydrogen peroxide-responsive triggers. In contrast to boronic acids, two concomitant oxidative rearrangements are involved in the complete oxidation of these species, which might represent a major limitation for an efficient effector (drug or fluorophore) release. Herein, a comprehensive study of H₂O₂-mediated unsymmetrical arylborinic acid oxidation to investigate the factors that could selectively guide their oxidative rearrangement is described. The o-CF₃ substituent was found to be an excellent directing group allowing a complete regioselectivity on borinic acid models. This result was successfully applied to synthesizing new borinic acid-based fluorogenic probes, which exclusively release the fluorescent moiety upon H₂O₂ treatment. These compounds maintained their superior kinetic properties compared to boronic acids, thus further enhancing the potential of arylborinic acids as valuable new H₂O₂-sensitive triggers.     

Catalytic oxidation of cyclohexane over Cu-Zn-Cr ternary spinel systems

Spinel systems with the composition of Cu_1−xZn_xCr₂O₄ [x = 0 CCr, x = 0.25 CZCr-1, x = 0.5 CZCr-2, x = 0.75 CZCr-3 and x = 1 ZCr] were prepared by homogeneous co-precipitation method and were characterized by X-ray diffraction (XRD) and FT-IR spectroscopy. Elemental analysis was done by EDX, and surface area measurements by the BET method. The redox behavior of these catalysts in cyclohexane oxidation at 243 K using TBHP as oxidant was examined. Cyclohexanone was the major product over all catalysts with some cyclohexanol. 69.2% selectivity to cyclohexanol and cyclohexanone at 23% conversion of cyclohexane was realized over zinc chromite spinels in 10 h.