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Propylene molecule owns two active sites, the direct epoxidation of propylene by dioxygen is still a challenge due to the limitation of selectivity. In this work, the direct liquid-phase propylene aerobic epoxidation protocol by chloride manganese meso-tetraphenylporphyrin (MnTPPCl) was developed. The conversion of propylene was 12.7%, and the selectivity towards PO (propylene oxide) reached up to 80.5%. The formation of PO was attributed to the mechanism via high-valent Mn species, which was confirmed by means of in situ UV-vis spectrum.

Herein, an efficient molecular oxygen-mediated method for the selective hydroxyalkylation and alkylation of quinoxalin-2(1H)-ones with alkylboronic acids under transition-metal free conditions has been developed. This strategy demonstrates a broad scope of quinoxalin-2(1H)-ones and alkylboronic acids, giving 3-hydroxyalkylquinoxalin-2(1H)-ones and 3-alkylquinoxalin-2(1H)-ones in moderate-to-good yield. Control experiments reveal that a radical pathway is involved.

Many natural oxidations are relevant to the origin and running of life but usually proceeded under mild conditions using molecular oxygen (O2) in the air as the sole oxidant and enzymes as the cata...

Atomically dispersed metal-nitrogen sites show great prospect for the oxygen reduction reaction (ORR), whereas the unsatisfactory adsorption-desorption behaviors of oxygenated intermediates on the metal centers impede improvement of the ORR performance. We propose a new conceptual strategy of introducing sacrificial bonds to remold the local coordination of Fe-N x sites, via controlling the dynamic transformation of the Fe-S bonds in the Fe-N-C single-atom catalyst. Spectroscopic and theoretical results reveal that the selective cleavage of the sacrificial Fe-S bonds induces the incorporation of the electron-withdrawing oxidized sulfur on the Fe centers. The newly functionalized moieties endow the catalyst with superior ORR activity and remarkable stability, owing to the reduced electron localization around the Fe centers facilitating the desorption of ORR intermediates. These findings provide a unique perspective for precisely controlling the coordination structure of single-atom materials to optimize their activity.

Understanding the fundamental insights of oxygen activation and reaction at metal-oxide interfaces is of significant importance yet remains a major challenge due to the difficulty in in situ characterization of active oxygen species. Herein, the activation and reaction of molecular oxygen during CO oxidation at platinum-ceria interfaces has been in situ explored using surface-enhanced Raman spectroscopy (SERS) via a borrowing strategy, and different active oxygen species and their evolution during CO oxidation at platinum-ceria interfaces have been directly observed. In situ Raman spectroscopic evidence with isotopic exchange experiments demonstrate that oxygen is efficiently dissociated to chemisorbed O on Pt and lattice Ce-O species simultaneously at interfacial Ce3+ defect sites under CO oxidation, leading to a much higher activity at platinum-ceria interfaces compared to that at Pt alone. Further in situ time-resolved SERS studies and density functional theory simulations reveal a more efficient molecular pathway through the reaction between adsorbed CO and chemisorbed Pt-O species transferred from the interfaces. This work deepens the fundamental understandings on oxygen activation and CO oxidation at metal-oxide interfaces and offers a sensitive technique for the in situ characterization of oxygen species under working conditions.

β-carotene spontaneously copolymerizes with molecular oxygen to form a β-carotene–oxygen copolymer compound (“copolymer”) as the main product, together with small amounts of many apocarotenoids. Both the addition and scission products are interpreted as being formed during progression through successive free radical β-carotene–oxygen adduct intermediates. The product mixture from full oxidation of β-carotene, lacking both vitamin A and β-carotene, has immunological activities, some of which are derived from the copolymer. However, the copolymer’s chemical makeup is unknown. A chemical breakdown study shows the compound to be moderately stable but nevertheless the latent source of many small apocarotenoids. GC–MS analysis with mass-spectral library matching identified a minimum of 45 structures, while more than 90 others remain unassigned. Newly identified products include various small keto carboxylic acids and dicarboxylic acids, several of which are central metabolic intermediates. Also present are glyoxal and methyl glyoxal dialdehydes, recently reported as β-carotene metabolites in plants. Although both compounds at higher concentrations are known to be toxic, at low concentration, methyl glyoxal has been reported to be potentially capable of activating an immune response against microbial infection. In plants, advantage is taken of the electrophilic reactivity of specific apocarotenoids derived from β-carotene oxidation to activate protective defenses. Given the copolymer occurs naturally and is a major product of non-enzymatic β-carotene oxidation in stored plants, by partially sequestering apocarotenoid metabolites, the copolymer may serve to limit potential toxicity and maintain low cellular apocarotenoid concentrations for signaling purposes. In animals, the copolymer may serve as a systemic source of apocarotenoids.

Plastic pollution is a serious threat to the environment as they are not bio-degradable. Herein using waste-polyethylene, we report two inter-related important findings. First that they can be converted economically and completely into highly photocatalytic carbon quantum-dots (CQDs) using H2O2 as a residue-free oxidant in an acid medium, and they have the ability to enrich a reaction medium with an extraordinary amount of molecular oxygen harvested from the air so that no separate oxygen source is needed while carrying out facile photocatalytic oxidation reactions. Second, when they are not performing any photocatalytic reaction, they exhibit self-sensitized photo-oxidation to convert themselves completely to CO2 in the presence of sunlight, a phenomenon that we term as ‘CQD-autophagy’ by drawing parallels to the death of useless-cells in the body. Such extinction from the reaction media is unique as no other material is known to do so and advantageous because the removal of carbon-dots from a solution is rather inefficient from an industry-viewpoint due to their high solubility. Instead, the inexpensive CQDs can be discarded casually with the notion that they will gradually get eliminated from the environment.

The C-H oxidation of saturated hydrocarbons to the corresponding alcohols and ketones can be performed efficiently at room temperature with molecular oxygen (1 atm) in the presence of acetaldehyde and catalysts such as Fe, Cu(OH)2 , and CuCl2 -18-crown-6 complex. Moreover, extremely high turnover numbers (>27,000) have been obtained for the C-H oxidation of saturated hydrocarbons with molecular oxygen (1 atm) using a combination of Cu(OAc)2 and acetonitrile at 70 °C. Related oxidation reactions such as epoxidation, Baeyer-Villiger reaction, acetoxylation of β-lactams with molecular oxygen and a suitable aldehyde at room temperature are described.

The rate constants of the interactions of chromium atoms with molecular oxygen through recombination Cr + O2 + M → CrO2 + M (I) and exchange Cr + O2 → CrO + O (II) were determined by a new method for treatment of experimental data. The results, together with the available literature data, led to the following equations for the rate constants of recombination in the low-pressure limit and of the exchange reaction: $${{k}_{{1,0}}}(300 < T < 2000\,\,{\text{K}}) = {\text{ }}3.7{\text{ }} \times {\text{ }}{{10}^{{18}}}{{\left( {{T \mathord{\left/ {\vphantom {T {1000}}} \right. \kern-0em} {1000}}} \right)}^{{ - 1.49}}},$$ cm6 mol–2 s–1, $${{k}_{2}}(700 < T < 4000\,{\text{K}}) = $$ $$4.0 \times {{10}^{{14}}}{{\left( {{T \mathord{\left/ {\vphantom {T {1000}}} \right. \kern-0em} {1000}}} \right)}^{{ - 0.32}}}exp\left( { - {{4480{\kern 1pt} \,{\text{K}}} \mathord{\left/ {\vphantom {{4480{\kern 1pt} \,{\text{K}}} T}} \right. \kern-0em} T}} \right)$$ , cm3 mol‒1 s‒1. An expression for the rate constant of the reverse reaction was obtained from k2(T) and the equilibrium constant for reaction (II): $${{k}_{{ - 2}}}(700 < T < 4000\,{\text{K}}) = 3.6 \times {{10}^{{13}}}{{\left( {{T \mathord{\left/ {\vphantom {T {1000}}} \right. \kern-0em} {1000}}} \right)}^{{ - 0.64}}}$$ cm3 mol‒1 s‒1. Modeling within the framework of the RRKM theory shows that calculation of the rate constant k1,0(T) requires inclusion of not only the ground electronic state of the CrO2 molecule, but also the low-lying excited electronic states up to the dissociation threshold. A comparison of the experimental and calculated temperature dependences shows that the best agreement between them is achieved at an average portion of energy transferred in deactivating collisions of the excited CrO2 molecule with diluent gas molecules of ΔE = 2.8 kJ/mol.

We describe the first electrochemical activation of D–A cyclopropanes and D–A cyclobutanes leading after C(sp3)−C(sp3) cleavage to the formation of highly reactive radical cations. This concept is utilized to formally insert molecular oxygen after direct or DDQ-assisted anodic oxidation of the strained carbocycles, delivering β- and γ-hydroxy ketones and 1,2-dioxanes electrocatalytically. Furthermore, insights into the mechanism of the oxidative process, obtained experimentally and by additional quantum-chemical calculations are presented. The synthetic potential of the reaction products is demonstrated by diverse derivatizations.

Transition metal-catalyzed aerobic oxidative reactions using molecular oxygen as the terminal oxidant play a significant role in organic synthesis. Benzoquinone (BQ) has been widely used as an electron-transfer mediator (ETM) in biomimetic palladium-catalyzed aerobic oxidative reactions, but always together with an ETM between O2 and BQ, such as a macrocyclic metal complex. Herein, we report on a heterogeneous palladium-catalyzed allenic C(sp3)-H arylation with only catalytic amounts of BQ under air without the need of an additional ETM. A range of multisubstituted 1,3-dienes were synthesized under mild reaction conditions. Mechanistic studies reveal the bifunctional role of BQ as a ligand for reductive elimination and as an ETM between Pd(0) and O2. This new regime of oxidation has important implications for further development of other transition metal-catalyzed aerobic oxidative reactions.

The activation of molecular oxygen is a fundamental step in almost all catalytic oxidation reactions. We have studied this topic and the role of surface vacancies for Co3O4(100) films with a synergistic combination of experimental and theoretical methods. We show that the as‐prepared surface is B‐layer terminated and that mild reduction produces oxygen single and double vacancies in this layer. Oxygen adsorption experiments clearly reveal different superoxide species below room temperature. The superoxide desorbs below ca. 120 K from a vacancy‐free surface and is not active for CO oxidation while superoxide on a surface with oxygen vacancies is stable up to ca. 270 K and can oxidize CO already at the low temperature of 120 K. The vacancies are not refilled by oxygen from the superoxide, which makes them suitable for long‐term operation. Our joint experimental/theoretical effort highlights the relevance of surface vacancies in catalytic oxidation reactions., Activated molecular oxygen (superoxide, O2 −) can oxidize CO already at 120 K on B‐layer terminated Co3O4(100) with oxygen vacancies. This rendered scheme illustrates how a vibrational spectrum of the adsorbed superoxide is recorded with surface action spectroscopy.

A simple and highly efficient method for manufacturing cyclohexanone oxime from solvent-free liquid-phase aerobic oxidation of cyclohexylamine over a glucose-modified TiO2 catalyst had been develop...

5-Hydroxy-6-methyluracil was found to be oxidized by molecular oxygen in an alkaline aqueous solution. The effect of temperature, concentration of alkali and oxygen on the reaction rate was revealed by UV spectroscopy and differential manometry. The reaction stoichiometry with respect to oxygen approaches 1 with an increase in the alkali concentration. Using methylated model compounds, it was shown that the consumption of 5-hydroxy-6-methyluracil in an aqueous alkaline medium is associated with the formation of the anionic form at the hydroxyl group.

A mild method for accessing diazo compounds via aerobic oxidation of hydrazones is described. This catalytic transformation employs a Cu(OAc)2/pyridine catalyst and molecular oxygen from ambient ai...

The formation of α-dicarbonyl compounds and 5-hydroxymethylfurfural during industrial processing of apple juice, orange juice, and peach puree samples was investigated in this study. Changes in the concentrations of sugars, free amino acids, α-dicarbonyl compounds, and 5-hydroxymethylfurfural in the samples from the critical process stages such as pasteurization, enzyme treatment, concentration, were monitored. The concentrations of sugars and free amino acids showed no statistically significant change during processing. 3-deoxyglucosone was identified as the dominant dicarbonyl compound formed during orange juice and peach puree processes, while glucosone was the main one formed in apple juice samples at all sampling points. In general, total dicarbonyl compounds significantly increased (p

Upon visible-light irradiation, the heterogeneous polymer of PDI–Cu(I)–PDI (PDI = perylene diimide) generates charge transfer states that are subsequently quenched by molecular oxygen for their par...

Photodynamic therapy (PDT) is a minimally invasive clinical protocol that combines a nontoxic photosensitizer (PS), appropriate visible light, and molecular oxygen for cancer treatment. This triad generates reactive oxygen species (ROS)

A simple, and practical oxidative scission of aromatic olefins to carbonyl compounds using O2 as the sole oxidant with poly(ethylene glycol) dimethyl ether as a benign solvent has been developed. A wide range of monosubstituted, gem-disubstituted, 1,2-disubstituted, trisubstituted and tetrasubstituted aromatic olefins was successfully converted into the corresponding aldehydes and ketones in excellent yields even with gram–scale reaction. Some control experiments were also conducted to support a possible reaction pathway.

A 2,2-azobis(isobutyronitrile)-catalyzed oxidative cleavage of alkenes with molecular oxygen as the oxidant was described. Carbonyl compounds and oxiranes were obtained in moderate yield under mild conditions. This study provided useful insights into the mechanism of aerobic oxidative cleavage of alkenes.

A copper-catalyzed aerobic 3-hydroxyisoindolinone synthesis was developed via the benzylic double C(sp3)–H functionalization of 2-alkylbenzamides. In this reaction, molecular oxygen was used as both an oxidant for C(sp3)–H functionalization and an oxygen source. Our method can be extended to diverse benzylic C(sp3)–H bonds and shows excellent functional group tolerance.

In this paper, it is found that the preferential growth of secondary {117} facets of Bi24O31Br10 into dominant facets would lead to higher photocatalytic activity, although the original main {213} facet has a stronger molecular oxygen adsorption ability, which illustrates that the charge separation efficiency induced by dominant/secondary facet control plays a more important role than that of O2 adsorptive performance in improving activity.

In recent years, Dakin oxidation has evolved primarily around the conversion of ortho- and para-hydroxy benzaldehydes and acetophenones to dihydric phenols, which are found in nature and complex organic materials. In the traditional Dakin reaction, an excess amount of NaOH was used along with hydrogen peroxide. The synthetic community has devoted much time and effort to developing efficient basic, acidic and neutral reaction media for Dakin oxidation. The use of in situ generated H2O2 and molecular oxygen was also tested as an alternative oxidant for this reaction. In this review, we will discuss recent developments in Dakin oxidation with representative examples as well as future challenges and potential applications for this exciting field.

HBr is a very cheap and efficient bifunctional catalyst for the synthesis of DFF from the photooxidation of HMF by O2 and from the cascade conversion of fructose via a one-step or especially the two-step protocol.

Molecular oxygen as a green, non-toxic and inexpensive oxidant has displayed lots of advantages compared with other oxidants towards more selective, sustainable, and environmentally benign organic transformations. The oxygenation reactions which employ molecular oxygen or ambient air as both an oxidant and an oxygen source provide an efficient route to the synthesis of oxygen-containing compounds, and have been demonstrated in practical applications such as pharmaceutical synthesis and late-stage functionalization of complex molecules. This review article introduces the recent advances of radical processes in molecular oxygen-mediated oxygenation reactions. Reaction scopes, limitations and mechanisms are discussed based on reaction types and catalytic systems. Conclusions and perspectives are also given in the end.

Catalytic synthesis of aromatic azo compounds by oxidative coupling of anilines using molecular oxygen represents a facile, green and valuable process; however, such an economical process suffers from poor catalytic activity and selectivity. Herein, novel single crystal MnOOH nanotubes with abundant Mn3+ sites and high oxygen defects were successfully synthesized. The catalyst exhibited high selectivity for oxidative coupling of anilines, achieving complete transformation into aromatic azo compounds under mild conditions, even at room temperature.

Self-assembly of cis-[RuCl2(dmso)4], NaVO3, Na2MoO4 and NaH2PO4 in a molar ratio of 1 : 3 : 6 : 1 in HOAc–NaOAc buffer (pH = 4–5) in the presence of CsCl gave a ruthenium(II)-supported phosphovanadomolybdate [RuII(dmso)3PMoVI6VV3O32]6− (1). While a similar reaction with the reactants in a molar ratio of 1 : 6 : 12 : 2 afforded a ruthenium substituted “sandwich” type polyoxometalate [RuII(PMoVI6VV3O32)2]14− (2). Clusters 1 and 2 were well characterized by single-crystal X-ray diffraction. Their use as heterogeneous catalysts for oxidation of alcohols in the presence of molecular oxygen was also investigated.

Selenization of Fe2O3 with NaHSe led to Se/Fe3O4. The unexpected generation of Fe3O4 attributed to the reduction conditions of the reaction, and the resulted magnetic features of the material facilitated its separation in practical applications. Owning to the synergistic effect of Se with Fe, the material was especially active to catalyze the oxidative C=C scission using O2 as mild oxidant. The technique has been successfully applied in polyene degradation project, which is of profound practical values for the treatment of the polyene pigment pollution and may be applied in the food and pharmaceutical industry.

Oxygenation reactions with molecular oxygen (O2 ) as the oxygen source provides a green and straightforward strategy for the construction of O-containing compounds. Demonstrated here is a novel N-heterocyclic carbene (NHC) catalyzed oxidative transformation of simple and readily available organic halides into valuable esters through the incorporation of O-atoms from O2 . Mechanistic studies prove that the deoxy Breslow intermediate generated in situ is oxidized to a Breslow intermediate for further transformation by this oxidative protocol. This method broadens the field of NHC catalysis and promotes oxygenation reactions with O2 .

An ideal catalytic process for the selective oxidation of hydrocarbons should employ an efficient, recyclable, and cost-effective catalyst under solvent- and additive-free conditions with molecular...

The direct epoxidation of propylene to propylene oxide (PO) using molecular oxygen is difficult to achieve. Liquid-phase aerobic propylene epoxidation has been achieved using metalloporphyrin catal...

The catalytic oxidation of cycloalkanes using molecular oxygen employing porphyrin cobalt(II) as catalyst was enhanced through use of cycloalkyl hydroperoxides, which are the primary intermediates in oxidation of cycloalkanes, as additional oxidants to further oxidize cycloalkanes in the presence of porphyrin copper(II), especially for cyclohexane, for which the selectivity was enhanced from 88.6 to 97.2% to the KA oil; at the same time, the conversion of cyclohexane was enhanced from 3.88 to 4.41%. The enhanced efficiency and selectivity were mainly attributed to the avoided autoxidation of cycloalkanes and efficient utilization of oxidation intermediate cycloalkyl hydroperoxides as additional oxidants instead of conventional thermal decomposition. In addition to cyclohexane, the protocol presented in this research is also very applicable in the oxidation of other cycloalkanes such as cyclooctane, cycloheptane and cyclopentane, and can serve as a applicable and efficient strategy to boost the conversion and selectivity simultaneously in oxidation of alkanes. This work also is a very important reference for the extensive application of metalloporphyrins in catalysis chemistry.

Methyl levulinate (ML) is a biobased platform molecule, which has versatile applications in fine chemical synthesis and food additives. However, during the ML production, one of the main barriers i...

The results of studying the dependence of the reaction rate of the hydrogen sulfide oxidation in oil with molecular oxygen in the presence of an ammonia solution of cobalt phthalocyanine on the process temperature, the consumption of the catalyst complex, and the concentration of cobalt phthalocyanine in the catalyst complex are reported. It was shown that the rate of the hydrogen sulfide oxidation strongly depends on the consumption of the catalyst complex and the concentration of cobalt phthalocyanine in the catalyst complex. Based on experimental data, a mathematical model was derived that describes the hydrogen sulfide oxidation with satisfactory accuracy. The calculated values obtained using this mathematical model are in good agreement with the experimental data.

A metal-free, visible-light-induced oxidative C-C bond cleavage of cycloketones with molecular oxygen is described. Cooperative Bronsted-acid catalysis and photocatalysis enabled selective C-C bond cleavage of cycloketones to generate an array of γ-, δ- and ϵ-keto esters under very mild conditions. Mechanistic studies indicate that singlet molecular oxygen (1 O2 ) is responsible for this transformation.

The main kinetic features of the oxidation of n-propyl mercaptan with molecular oxygen in a model mixture with diesel fuel in the presence of an ammoniac solution of cobalt phthalocyanine have been studied. The rate equation of the reaction has been derived based on the experimental data, and optimum conditions of a waste-free process for removing hydrogen sulfide and mercaptans from crude petroleum have been selected.

Multicopper oxidases oxidize a vast range of aromatic substrates coupled to the reduction of molecular oxygen to water. A vast broad spectrum of applications reflects their high biotechnological im...

A series of iridium complexes with various cyclometalated ligands and phosphines [Ir(N^C)2(PR3)Cl], where N^C = 2-(benzothiophen-3-yl)pyridine and 2-phenylpyridine and R = phenyl and p-methoxyphenyl, were obtained. It was shown that the complexes of this type react with imidazole under mild conditions. The phosphine and chloride ligands are consecutively substituted to give imidazole-containing derivatives. The photophysical properties of all the synthesized compounds were investigated in detail. The imidazole-containing complexes demonstrate efficient triplet luminescence in solution with quantum yields up to 60%, which is sensitive to molecular oxygen.

Direct selective desaturation of carbonyl compounds to synthesize α,β-unsaturated carbonyl compounds represents an environmentally benign alternative to classical stepwise procedures. In this study...

The first non-enzymatic redox deracemization method using molecular oxygen as the terminal oxidant has been described. The one-pot deracemization of β,γ-alkynyl α-amino esters consisted of a copper-catalyzed aerobic oxidation and chiral phosphoric acid-catalyzed asymmetric transfer hydrogenation with excellent functional group compatibility. By using benzothiazoline as the reducing reagent, an exclusive chemoselectivity at the C Created by potrace 1.16, written by Peter Selinger 2001-2019 N bond over the C Created by potrace 1.16, written by Peter Selinger 2001-2019 C bond was achieved, allowing for efficient deracemization of a series of α-amino esters bearing diverse α-alkynyl substituent patterns. The origins of chemo- and enantio-selectivities were elucidated by experimental and computational mechanistic investigation. The generality of the strategy is further demonstrated by efficient deracemization of β,γ-alkenyl α-amino esters., A one-pot deracemization of β,γ-alkynyl α-amino esters consisting of an aerobic oxidation and chiral phosphoric acid-catalyzed asymmetric transfer hydrogenation has been described.

Activation of C-H bonds of the hydrocarbons is one of the thrust areas of research over the years. Designing a robust catalyst, which can work efficiently under eco-friendly conditions for this rea...

The triphasic aerobic extractive desulfurization of benzothiophene (BT) using an aqueous H8PV5Mo7O40 solution as catalyst and O2 as oxidant was investigated. A time-resolved analysis of all reaction products in the gas, organic and aqueous phase, is given. The organic sulfur in BT is mainly converted to sulfuric acid. Mass transport limitations can be excluded. The reaction orders are 1 with regard to BT, and 0.5 both for HPA-5 and O2. Calculated data derived from this mechanism with a power law kinetic approach show good agreement to the experimental data for conversions below 60 \%. At higher BT conversions, significant deviations are found, suggesting that acidic products formed in the BT oxidation affect the catalyst and therefore the initial kinetics of the BT oxidation.

In this work the magnetic field effects (MFE) on the photoluminescence of MEH-PPV film and nanoparticles were obtained using the MFE technique with continuous-wave photoexcitation. The analysis of ...

The oxidation of aldehydes with molecular oxygen was investigated in the presence of MoO2(acac)2(Bis(acetylacetonato)dioxomolybdenum(VI)), and under mild condition (temperature and pressure). In the oxidation reaction system, the effect of the catalyst has been evaluated. In addition, the factor of solvents was deeply discussed. The process is particularly selective for linear and aromatic aldehydes. Finally, the use of environmentally-friendly oxidation system, including mild conditions and inexpensive oxidant, can make this process very attractive in the fine chemical synthesis.