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Herein, we have established a method for the construction of β‐keto sulfones through aerobic oxy‐sulfonylation of alkynes with sulfinates. The reaction performed employing air as the oxidant and oxygen source. Moreover, this protocol exhibits low consume of sulfinates, short reaction period, and minimal waste. Mechanism study and density functional theory (DFT) calculation showed that the solvent played a significant role in the transformation. [ABSTRACT FROM AUTHOR]

Mesoporous Co3O4 nanostructures, templated from different mesoporous silicas, SBA-3, SBA-5, and SBA-16, were used as catalysts for the liquid-phase selective oxidation of benzyl alcohol using molecular oxygen as the oxidant. The nanostructured Co3O4-16, templated from SBA-16, showed the best activity for the reaction, with 97.5% benzyl alcohol conversion and 100% benzaldehyde selectivity obtained after 3 h of reaction at 100°C. This could be attributed to its large number of oxygen vacancies and low surface Co3+/Co2+ ratio that were beneficial to O2 activation, together with its three-dimensional nanostructure that facilitated the adsorption of benzyl alcohol, compared to Co3O4-3 and Co3O4-15. The material could be reused without losing activity if the organics adsorbed on the surface of the used sample were removed by calcination at 300°C for 1 h. A mechanism for the reaction was proposed, considering that the activation of molecular oxygen was the rate-determining step of the reaction. [ABSTRACT FROM AUTHOR]

Red light-driven selective oxidation of benzyl amines to imines has been effectuated by Por-DETH-COF photocatalysis. [Display omitted] • A hydrazone-linked 2D porphyrinic COF, Por-DETH-COF, is assembled. • Red light-driven selective aerobic oxidation of amines is achieved. • The system exhibits a broad scope of substrate amines. • Por-DETH-COF displays outstanding recyclability. • Hydrazone-linked COFs provide a unique photocatalytic juncture. Covalent organic frameworks (COFs) have recently gained rising consideration for visible light photocatalysis. Their property could be accurately established with specific reactions in which the most investigated one turns out to be the aerobic oxidation of amines. In this contribution, a hydrazone-linked 2D (two-dimensional) porphyrinic COF, Por-DETH-COF, was assembled from 5,10,15,20-tetrakis(4-benzaldehyde)porphyrin (p -Por-CHO) and 2,5-diethoxyterephthalohydrazide (DETH) and its photocatalytic activity was duly appraised with the aerobic oxidation of amines. Thereby, the red light-driven selective oxidation of benzyl amines to imines was obtained in very high conversions and selectivities with ambient air as the oxidant. Importantly, the photocatalytic system exhibited remarkable compatibility of functional groups and extensive scope of benzyl amines. Notably, the Por-DETH-COF photocatalyst displayed outstanding recyclability after five successive cycles. This work suggests that 2D COFs could contribute a unique juncture for selective organic transformations by photocatalysis. [ABSTRACT FROM AUTHOR]

The metal organic framework {[Cu2(CN)3(phen)3]5H2O} MOF1- bicarbonate system was investigated as an efficient catalyst for aerobic oxidation of 2, 6-di-tert-butylphenol (2,6- DTBP). The catalytic system showed very efficient catalytic behavior for the oxidation of selective coupling of 2,6- DTBP to 3,3′,5,5′-tetra-tert-butyl-4,4′-diphenoquinone (DPQ) in excellent yield. The influence of reaction parameters on the selective oxidation of 2, 6-DTBP to DPQ had been investigated. Photoluminescence probing technology of Disodium salt of terephthalic acid as well as scavenging experiments revealed the creation of the hydroxyl radicals as the main active oxidation radicals produced by the MOF1/O2/basic bicarbonate system. The oxidation reaction mechanism was also discussed. The recycled catalytic system retained its activity for eight successive runs.

[Display omitted] One sustainable concept emerges to implement the selective oxidation of sulfides with dioxygen (O 2) at ambient conditions and has received increasing attention. As such, three donor–acceptor (D–A) type conjugated microporous polymers (CMPs) were connected via robust C C bonds prepared from FeCl 3 -promoted polymerization of monomers of 3,6-di(9 H -carbazol-9-yl)-9 H -fluorene with the 9 H position of the fluorene moiety occupied by 1,1′-biphenyl-, difluoro-, or keto- group, furnishing 9,9′-(9,9′-spirobi[fluorene]-2,7-diyl)-bis-9 H -carbazole-CMP (SFC-CMP), 9,9′-(9,9-difluoro-9 H -fluorene-2,7-diyl)bis(9 H -carbazole)-CMP (FFC-CMP), and 2,7-di(carbazol-9-yl)-fluoren-9-one-CMP (OFC-CMP), respectively. These three carbazole–fluorene CMPs could implement blue light-driven highly selective oxidation of sulfides into sulfoxides with O 2 in methanol (CH 3 OH). Intriguingly, the SFC-CMP imparted the best photocatalytic activity for selective oxidation of sulfides in a broad scope. Besides, the SFC-CMP photocatalyst could be fully recovered even outperforming the fresh one. This work highlights that the properties of CMPs could be regulated by the D–A units like carbazole–fluorene to execute selective chemical transformations ambiently. [ABSTRACT FROM AUTHOR]

Mesoporous ceria–cobalt (Ce0.9Co0.1O2, Ce0.8Co0.2O2, and Ce0.7Co0.3O2) mixed oxides, ceria (CeO2), and cobalt oxide (Co3O4) catalysts were prepared through modified template-assisted method and employed in oxidation of ethylbenzene with molecular oxygen (O2) without solvent and additives. Prepared catalysts were characterized by various physicochemical characterization techniques. The XRD results showed the formation of solid solutions in cobalt-doped ceria samples. The XPS results indicated the presence of more Ce3+ ions and surface adsorbed oxygen. H2-TPR profiles revealed a remarkable improvement in the redox behavior of ceria with the doping of cobalt into the ceria lattice. TEM and N2 adsorption studies showed mesoporous nature of materials. Among the prepared catalysts, Ce0.9Co0.1O2 showed far better activity for oxidation of ethylbenzene with 60% conversion and 87% selectivity toward acetophenone. This is attributed to facile redox behavior, more surface adsorbed oxygen species, and larger surface area of the catalyst and considered as crucial factors to improve the catalytic activity. Mesoporous ceria–cobalt (Ce0.9Co0.1O2) mixed oxide efficiently catalyzed the aerobic oxidation of ethylbenzene to acetophenone without solvent with good conversion and selectivity. [ABSTRACT FROM AUTHOR]

Poly(1-vinylimidazole), (p(1-VIm)), hydrogels were synthesized via free radical polymerization reaction and modified with different alkyl dihalides of variable chain lengths such as 1,2-dibromoethane (1,2-BE) and 1,4-dibromobutane (1,4-BB) to obtain polymeric ionic liquid. The chemical structure of synthesized p(1-VIm) macroporous hydrogel was confirmed by Fourier transform infrared spectroscopy (FT-IR) and scanning electron microscopy. P(1-VIm)-Ag, 1,2-BE-p(1-VIm)-Ag, and 1,4-BB-p(1-VIm)-Ag were prepared by reducing Ag(CH3COO) metal salts loaded into p(1-VIm) hydrogels and then reducing with NaBH4. Metal nanoparticles embedded p(1-VIm)-Ag were visualized by transmission electron microscopy. The metal content of all composites was estimated via atomic absorption spectroscopy, and its amount was 4.44 mmol/g hydrogel, 5.44 mmol/g hydrogel, and 8.39 mmol/g hydrogel, for p(1-VIm), 1,2-BE-p(1-VIm), and 1,4-BB-p(1-VIm), respectively. According to the results, metal content of quaternized hydrogels is higher than nonquaternized. P(1-VIm)-Ag, 1,2-BE-p(1-VIm)-Ag, and 1,4-BB-p(1-VIm)-Ag composites were used as catalyst in the aerobic oxidation of olefins by emphasizing the effects of different parameters such as temperature, substituent effect, etc. Olefin oxidation reaction was carried out in higher oxidation conversion by 1,2-BE-p(1-VIm)-Ag and 1,4-BB-p(1-VIm)-Ag than p(VIm)-Ag, due to high hydrophobicity of quaternized composites. The prepared porous hydrogel composites were also used as catalyst in H2 generation from hydrolysis of sodium borohydride (NaBH4). The activation energies, enthalpy, and entropy for NaBH4 hydrolysis catalyzed by composites were determined. According to the results, p(VIm)-Ag showed higher catalytic activity. Low performance of 1,4-BB-p(1-VIm)-Ag than 1,2-BE-p(1-VIm)-Ag and p(1-VIm)-Ag is due to high hydrophobicity of this hydrogel than the other catalytic systems whiles reaction medium is water. Furthermore, the p(1-VIm), 1,2-BE-p(1-VIm), and 1,4-BB-p(1-VIm) were utilized in the adsorption of oxo-anions such as Cr2O7−2, CrO4−2 and MnO4−. Between hydrogels, 1,4-BB-p(1-VIm) has better performance than 1,2-BE-p(1-VIm) and p(1-VIm). Because of that, ion absorption capacity is increased with an increase in the number of carbon atoms in the chain of the alkylation agents. In addition, pH dependency of adsorbents was investigated and p(VIm) showed high pH dependency. Indeed, hydrophilic/hydrophobic character and permanent positive charges of Q-p(VIm) hydrogels made them independent of the solution pH. Finally, the catalyst was easily recovered from the reaction medium, and it could be reused for other four runs without significant loss of activity. Durability of catalyst structure without leaching confirmed by FT-IR spectra and atomic absorption spectroscopy, respectively. [ABSTRACT FROM AUTHOR]

This review focuses on recent advances and mechanistic views of aerobic C(sp3)–H oxidations catalyzed by organocatalysts, where metal catalysis and photocatalysis are not included. 1 Introduction 2 Carbanion Route: TBD-Catalyzed C(sp3)–H Oxygenation 2.1 α-Hydroxylation of Ketones 2.2 Carbonylation of Benzyl C(sp3)–H 3 Radical Route: NHPI-Catalyzed C(sp3)–H Oxidation 3.1 N-Oxyl Radicals and Mechanisms 3.2 Oxygenation of Benzyl C(sp3)–H 3.3 Solvent Effects 4 Hydride-Transfer Route: TEMPO-Catalyzed Oxidations 4.1 Oxoammonium Cation and Mechanisms 4.2 Dehydrogenation of Alcohols 4.3 Oxygenation of Benzyl C(sp3)–H 5 Conclusions and Outlook [ABSTRACT FROM AUTHOR]

The ketones and benzoic acids are very useful chemicals as the precursors and intermediates in both laboratory and synthetic industrial applications, which are usually obtained by selective catalytic oxidation of alcohols using a amount of certain expensive oxidants or metal catalysts. Here, an efficient and practical oxidation the aryl secondary and primary alcohols to corresponding carbonyl compounds using NaOtBu in open air at room temperature has been developed. And utilizing NaOtBu/air/ toluene, a series of ketones or benzoic acids were obtained from secondary and primary alcohols in high yields, respectively. More importantly, most of the substrates with electron‐withdrawing or electron‐donating groups could be converted to the corresponding products in high to excellent yields. Furthermore, the practicality of the reaction was demonstrated through 1.0 gram‐scale reaction with excellent yield. [ABSTRACT FROM AUTHOR]

The construction of C−O bonds through C−H bond functionalization remains fundamentally challenging. Here, a practical chlorine radical‐mediated aerobic oxidation of alkylarenes to carbonyls was developed. This protocol employed commercially available HCl as a hydrogen atom transfer (HAT) reagent and air as a sustainable oxidant. In addition, this process exhibited excellent functional group tolerance and a broad substrate scope without the requirement for external metal and oxidants. The mechanistic hypothesis was supported by radical trapping, 18O labeling, and control experiments. [ABSTRACT FROM AUTHOR]

[Display omitted] Photocatalytic oxidative organic reactions are important synthetic transformations, and research on reaction selectivity by reactive oxygen species (ROS) is significant. To date, however, there has rarely been any focus on the directed generation of ROSs. Herein, we report the first identification of tunable molecular oxygen activation induced by polymeric conjugation in nonmetallic conjugated microporous polymers (CMP). The conjugation between these can be achieved by the introduction of alkynyl groups. CMP-A with an alkynyl bridge facilitates the intramolecular charge mobility while CMP-D, lacking an alkynyl group enhances the photoexcited carrier build-up on the surface from diffusion. These different processes dominate the directed ROS generation of the superoxide radical (O 2 −) and singlet oxygen (1O 2), respectively. This theory is substantiated by the different performances of these CMPs in the aerobic oxidation of sulfides and the dehydrogenative coupling of amines, and could provide insight into the rational design of CMPs for various heterogeneous organic photosynthesis. [ABSTRACT FROM AUTHOR]

Biomimetic oxidation of primary amines to carboxylic acids has been developed where the copper‐containing amine oxidase (CuAO)‐like o‐NQ‐catalyzed aerobic oxidation was combined with the aldehyde dehydrogenase (ALDH)‐like TBHP‐mediated imine oxidation protocol. Notably, the current tandem oxidation strategy provides a new mechanistic insight into the imine intermediate and the seemingly simple TBHP‐mediated oxidation pathways of imines. The developed metal‐free amine oxidation protocol allows the use of molecular oxygen and TBHP, safe forms of oxidant that may appeal to the industrial application. [ABSTRACT FROM AUTHOR]

Aerobic oxidative desulfurization (AODS) represents a sustainable way to deeply desulfurize transportation fuels through a high-performance catalyst to convert thiophenes into sulfones in an efficient way. Here, we report that iron (Fe) intercalated molybdenum oxides (MoOx) nanobelts can be a durable and robust catalyst for AODS, catalyzing the reaction efficiently at 80 °C with air as a sustainable oxygen source. By combining systematic characterization, kinetic analysis, and density functional theory calculation, we demonstrate that the guest Fe ions could precisely modulate the electronic structure of Mo sites, leading to a significant increase in surface oxygen vacancy density. An optimized doping amount enables our catalyst with excellent catalytic performance via thorough conversion of various sulfides. The catalyst maintained almost unchanged activity in repeated uses, qualifying it as a candidate for the sustainable AODS of fuel. We anticipate that the strategy demonstrated here will provide practical guidance on the rational design and optimization of Mo-based catalysts to promote aerobic oxidation reactions. [ABSTRACT FROM AUTHOR]

A base-free catalytic system for the aerobic oxidation of 5-hydroxymethyl-2-furfural was exploited by using Pt nanoparticles immobilized onto a thermoresponsive poly(acrylamide-co-acrylonitrile)-b-poly(N-vinylimidazole) block copolymer, with an upper critical solution temperature of about 45 °C. The Pt nanocatalysts were well-dispersed and highly active for the base-free oxidation of 5-hydroxymethyl-2-furfural by molecular oxygen in water, affording high yields of 2,5-furandicarboxylic acid (up to >99.9%). The imidazole groups in the block copolymer were conducive to the improvement of catalytic performance. Moreover, the catalysts could be easily separated and recovered based on their thermosensitivity by cooling the reaction system below the upper critical solution temperature. Good stability and reusability were observed over these copolymer-immobilized catalysts with no obvious decrease in catalytic activity in the five consecutive cycles. [ABSTRACT FROM AUTHOR]

A convenient aerobic oxidative hydroxylation of 3-substituted oxindoles under mild reaction conditions is described herein. This process was accomplished by the activation of molecular oxygen in the air in the presence of a photocatalyst under the irradiation of visible light. The desired product was delivered in up to 89% yield without the addition of base or stoichiometric oxidant.

In the present study, the allylic oxidation of cyclohexene is investigated using molecular oxygen as an oxidant under environment-friendly conditions in the presence of rGO-dithiooxamide/Au hybrid nanocatalyst (rGO $=$ reduced graphene oxide). This hybrid catalyst comprises nanometric spherical gold particles supported on dithiooxamide-functionalized rGO. The structure of the prepared hybrid catalyst was characterized using FT-IR, XRD, SEM and TEM techniques. The catalytic activity results were found to be dependent on pressure, the amount of hybrid nanocatalyst, reaction time, and temperature. In addition, an 85% conversion and 85% selectivity to 2-cyclohexene-1-one were obtained under optimized reaction conditions. The catalytic activity over a recycled catalyst (rGO-dithiooxamide/Au) remained at a satisfactory state after at least five cycles.

In the latest years, the concentration levels of certain metals and metalloids in the sediments of the Galician Rías have shown an increasing trend (e.g., As, Zn, Cu, Pb, Hg). These areas are also characterized by their richness in nutrients and their great aquaculture or mariculture activity, with the presence of more than 3500 mussel rafts in the Rías Baixas. The inner areas of the Galician Rías are subjected to activities that resuspend the sediment such as high levels of maritime traffic and dredging or cleaning operations. It is likely that a transfer of these elements to the water column happens during the resuspension of sediments caused by natural events or anthropogenic activities. In this study, selected samples of surface sediments of the Ría de Pontevedra (NW Spain) were subjected to a procedure of aerobic oxidation to determine the concentration of some elements (Fe, Mn, Cu, Cr, Pb, Hg, and Zn) released from the sediment to the aqueous phase. The experiment was carried out within 5 days. Measurements of pH and total concentration were taken both in water and sediment samples. Furthermore, speciation of trace elements was carried out in the sediment samples. Trace element concentrations were lower in the sediments during aerobic oxidation, being released to the aqueous phase. From an environmental point of view, Cu was the only trace element released in quantities that may be toxic for the organisms in the area. This problem of sediment oxidation related to dredging activities or natural storm conditions should be considered in environmental impact studies and transferred to stakeholders., (© 2024. The Author(s).)

Optimizing lanthanide catalyst performance with organic ligands often encounters significant challenges, including susceptibility to water or oxygen and complex synthesis pathways. To address these issues, our research focuses on developing inorganic lanthanide clusters with enhanced stability and functionality. In this study, we introduce the [Sm 6 O(OH) 8 (H 2 O) 24 ]I 8 (H 2 O) 8 cluster (Sm-OC) as a sustainable and efficient catalyst for the aerobic oxidation of thiols under heating conditions. The Sm-OC catalyst demonstrated remarkable stability, outstanding recyclability, and excellent chemoselectivity across a diverse range of functional groups in 38 different tests. Notably, it enables efficient unsymmetrical disulfide synthesis and prevents the formation of over-oxidized by-products, highlighting its superior performance. This Sm-OC catalyst provides a practical and robust tool for the precise construction of versatile disulfides, thus establishing a template for the broader use of lanthanide clusters in organic synthesis., Competing Interests: The authors declare no conflicts of interest.

Kisspeptin signaling regulates energy homeostasis. Adiposity is the principal source and receiver of peripheral Kisspeptin, and adipose Kiss1 metastasis suppressor (Kiss1) gene expression is stimulated by exercise. However, whether the adipose Kiss1 gene regulates energy homeostasis and plays a role in adaptive alterations during prolonged exercise remains unknown. Here, we investigated the role of Kiss1 role in mice and adipose tissues and the adaptive changes it induces after exercise, using adipose-specific Kiss1 knockout (Kiss1 adipoq-/- ) and adeno-associated virus-induced adipose tissue Kiss1-overexpressing (Kiss1 adipoq over ) mice. We found that adipose-derived kisspeptin signal regulates lipid and glucose homeostasis to maintain systemic energy homeostasis, but in a sex-dependent manner, with more pronounced metabolic changes in female mice. Kiss1 regulated adaptive alterations of genes and proteins in tricarboxylic acid (TCA) cycle and oxidative phosphorylation (OxPhos) pathways in female gWAT following prolonged aerobic exercise. We could further show that adipose Kiss1 deficiency leads to reduced peroxisome proliferator-activated receptor gamma co-activator 1 alpha (PGC-1α) protein content of soleus muscle and maximum oxygen uptake (VO 2 max) of female mice after prolonged exercise. Therefore, adipose Kisspeptin may be a novel adipokine that increases organ sensitivity to glucose, lipids, and oxygen following exercise., (© 2024 The Author(s). The FASEB Journal published by Wiley Periodicals LLC on behalf of Federation of American Societies for Experimental Biology.)

Solar-driven upgrading of biomass-derived 5-hydroxylmethylfurfural (HMF) to 2,5-furandicarboxylic acid (FDCA) holds great promise for sustainable production of bio-plastics and resins. However, the process is limited by poor selectivity and sluggish kinetics due to the vertical coordination of HMF at relatively strong metal sites. Here, we purposely developed a Cu(II) porphyrin framework featuring side-chain incorporated urea linkages, denoted as TBUPP-Cu MOF, to render HMF a weak hydrogen bond at the urea site and flat adsorption via π-π stacking with the benzene moiety. The unique configuration promotes the approaching of -CHO of HMF to the photoexcited porphyrin ring towards kinetically and thermodynamically favourable intermediate formation and subsequent desorption. The charge localisation and orbital energy alignment enable the selective activation of O 2 over the porphyrin to generate ⋅O 2 - and 1 O 2 instead of highly oxidative H 2 O 2 and ⋅OH via spin-flip electron transfer, which drive the ambient oxidation of proximal -CHO. The effective utilisation of redox species and circumvented over-oxidation facilitate a FDCA selectivity of >90 % with a high turnover number of 193 mol HMF  mol Cu -1 . The facile purification of high-purity FDCA and zero-waste recycling of intermediates and durable catalyst feature TBUPP-Cu MOF a promising photo-oxidation platform towards net-zero biorefining and organic transformations., (© 2024 The Authors. Angewandte Chemie International Edition published by Wiley-VCH GmbH.)

MXenes are two-dimensional nanomaterials having alternating sheets of one atom-thick early transition metal layer and one atom-thick carbide or nitride layer. The external surface contains termination groups, whose nature depends on the etching agent used in the preparation procedure from the MAX phase. The present concept proposes that, due to their composition, the metal-surface termination groups make MXenes particularly suited as heterogeneous catalysts for some reactions. This proposal comes from the consideration that early transition metal atoms bonded to hydroxyl and oxo groups are a general type of active sites in heterogeneous catalysis and that similar catalytic centers can also be present in the MXene structure. After having presented the concept, we have selected V 2 C Mxene as an example to illustrate its catalytic activity and to show how the catalytic performance varies when the surface groups are modified. As a test reaction, we selected the aerobic oxidation of indane to the corresponding indanol/indanone mixture using molecular oxygen as terminal oxidizing reagent. Two previously reported procedures to modify the surface groups, namely surface dehydroxylation by thermal treatment under diluted hydrogen flow and surface oxidation with ammonium persulfate to convert some surface groups into oxo groups were used, observing in both cases a decrease in the catalytic activity of V 2 C. Based on this, V III/IV -OH are proposed as catalytic centers in this aerobic oxidation. Overall, the present concept shows the merits of MXenes in heterogeneous catalysis, based on their chemical composition and the surface functionality., (© 2024 The Authors. Chemistry - A European Journal published by Wiley-VCH GmbH.)

A MIL-53(Fe)/g-C3N4 heterogeneous composite was synthesized and applied in photocatalytic oxidation of 5-hydroxymethylfurfural (5-HMF) to 2,5-diformylfuran (DFF). The systematic investigation indicated that the introduction of MIL-53(Fe) into g-C3N4 increased the specific surface area, broadened the visible-light response region, and promoted the separation efficiency of the photo-generated electron-hole pairs. The 10% MIL-53(Fe)/g-C3N4 heterogeneous composite achieved the best photocatalytic oxidation activity with 74.5% of 5-HMF conversion under simulated sunlight, which was much higher than that of pristine g-C3N4 and MIL-53(Fe). The MIL-53(Fe)/g-C3N4 composite displayed good photocatalytic reusability and stability. Based on the characterization results and photocatalytic performance, a Z-scheme photocatalytic mechanism of the MIL-53(Fe)/g-C3N4 composite was suggested, and a possible reaction route was deduced.

Catalytic iodine in the presence of water acts indirectly as a source of Brønsted acid and, concurrently, generates iodonium ion and hydrogen peroxide, which mediate the final oxidative aromatization step in the multicomponent cyclocondensation of an aromatic amine and two aliphatic aldehyde compounds. The oxidative cycle in this and related iodine‐catalyzed reactions is seldom discussed, generally unoptimized, and rarely investigated in detail. This work establishes that two independent catalytic cycles (H+ and I−/I+) drive such multicomponent cyclocondensation/ oxidation reactions, provided that the oxidant is generated in sufficient concentration to inhibit oxidation of the dihydroquinoline by the intermediate iminium cation. The complementary dual catalytic cycles, when optimized, act in concert to suppress side product formation, which simplifies isolation and purification of the self‐aggregating products, and increases the efficiency and scope of the Wang‐Kozlov multicomponent reaction. [ABSTRACT FROM AUTHOR]

A copper‐catalyzed aerobic oxidative azo‐ene cyclization has been developed. The developed CuI/DMAP/O2 system efficiently facilitates the aerobic oxidation of ene‐containing hydrazides to azo compounds, which undergo azo‐ene cyclizations for the synthesis of oxazolidinones. In addition, the present approach enables the synthesis of lactams, as well as a nitroso‐ene cyclization. Preliminary mechanistic studies revealed that two carbonyl groups were essential for the successful azo‐ene cyclization and that a concerted mechanism might be plausible for this azo‐ene cyclization. [ABSTRACT FROM AUTHOR]

Herein, an iron(II)‐catalyzed biomimetic oxidation of N‐heterocycles under aerobic conditions is described. The dehydrogenation process, involving several electron‐transfer steps, is inspired by oxidations occurring in the respiratory chain. An environmentally friendly and inexpensive iron catalyst together with a hydroquinone/cobalt Schiff base hybrid catalyst as electron‐transfer mediator were used for the substrate‐selective dehydrogenation reaction of various N‐heterocycles. The method shows a broad substrate scope and delivers important heterocycles in good‐to‐excellent yields. [ABSTRACT FROM AUTHOR]

7,8‐Dimethoxy‐3‐methyl‐1,10‐ethylenealloxazinium chloride (1a) was found to be a superior photooxidation catalyst among substituted ethylene‐bridged flavinium salts (R=7,8‐diMeO, 7,8‐OCH2O‐, 7,8‐diMe, H, 7,8‐diCl, 7‐CF3 and 8‐CF3). Selection was carried out based on structure vs catalytic activity and properties relationship investigations. Flavinium salt 1a proved to be robust enough for practical applications in benzylic oxidations/oxygenations, which was demonstrated using a series of substrates with high oxidation potential, i. e. 1‐phenylethanol, ethylbenzene, diphenylmethane and diphenylmethanol derivatives substituted with electron‐withdrawing groups (Cl or CF3). The unique capabilities of 1a can be attributed to its high photostability and participation via a relatively long‐lived singlet excited state, which was confirmed using spectroscopic studies, electrochemical measurements and TD‐DFT calculations. This allows the maximum use of the oxidation power of 1a, which is given by its singlet excited state reduction potential of +2.4 V. 7,8‐Dichloro‐3‐methyl‐1,10‐ethylenealloxazinium chloride (1 h) can be used as an alternative photocatalyst for even more difficult substrates. [ABSTRACT FROM AUTHOR]

A simple and efficient TEMPO-mediated system for aerobic oxidative synthesis of 2-aryl benzoxazoles from readily available benzoxazoles and primary benzylic and hetero benzylic amines is presented in one pot. The reaction proceeds through the ring-opening of benzoxazoles and is followed by oxidative condensation with benzylamines. These metal-free, straightforward reactions worked well with a wide range of substrates, yielding moderate to good yields under mild conditions using air as an external green oxidant. [ABSTRACT FROM AUTHOR]

Mixed-ligand ruthenium(II) complex with 2,2′-bipyridine and 1,10-phenanthroline-3,8-dicarboxylic acid with the composition [Ru(phen-C)(bpy)2]Cl2·5H2O (bpy = 2,2′-bipyridine, phen-C = 1,10-phenantroline-3,8-dicarboxylic acid) has been synthesized and characterized by spectral data. The complex has been tested as photocatalyst in aerobic oxidation reactions, including transformation of arylboronic acids to phenols, primary amines to imines, and sulfides to sulfoxides in aqueous medium. The possibility of regeneration of the catalyst in the oxidation of sulfides has been demonstrated. [ABSTRACT FROM AUTHOR]

A catalyst‐free direct aerobic oxidative annulation reaction of 2‐aminobenzylic amines and α‐hydroxy ketones efficiently afforded versatile 5H‐1,4‐benzodiazepine derivatives by employing air as economic and green oxidant under mild conditions. Interestingly, solvent was found to be crucial to the reaction, so that by using acetic acid as the best solvent an efficient and practical method could be achieved, requiring no catalysts or additives at all. This method tolerates a wide range of 2‐aminobenzylic amines and α‐hydroxy ketones and could be scaled up to multigram synthesis and directly applied in one‐step synthesis of the pharmaceutically active N‐desmethylmedazepam derivatives, revealing the potential of this new method in the synthesis of 5H‐1,4‐benzodiazepine skeleton‐based pharmaceuticals and chemicals. [ABSTRACT FROM AUTHOR]

Copper catalyzed aerobic oxidation enables the tandem selective and efficient transformation of N‐pyridylindole for the construction of 11H‐pyrido[2,1‐b]quinazolin‐11‐ones. The reaction shows good efficiency to accomplish the aerobic oxidation. Mechanistic investigation indicated the facile oxidation of N‐pyridylindole underwent the single‐electron‐transfer oxidation, the capture of molecular oxygen and the extrusion of carbon monoxide to deliver the desired 11H‐pyrido[2,1‐b]quinazolin‐11‐ones. [ABSTRACT FROM AUTHOR]

A ligand-free palladium-catalyzed aerobic oxidative carbonylation of amines for the synthesis of ureas, particular unsymmetrically N,N′-disubstituted ureas, which cannot be accessed by any other palladium-catalyzed oxidative carbonylation of amines to date, is presented. An array of symmetrical and unsymmetrical ureas were straightforwardly synthesized by using inexpensive, readily available, stable, and safe amines with good to excellent yields under a pressure of 1 atm. This novel method employs oxygen as the sole oxidant and offers an attractive alternative to transition-metal-based oxidant systems [ABSTRACT FROM AUTHOR]

A mild photocatalytic phenol oxygenation enabled by a continuous‐flow photoreactor using visible light and pressurized air is described herein. Products for wide‐ranging applications, including the synthesis of vitamins, were obtained in high yields by precisely controlling principal process parameters. The reactor design permits low organophotocatalyst loadings to generate singlet oxygen. It is anticipated that the efficient aerobic phenol oxygenation to benzoquinones and p‐quinols contributes to sustainable synthesis. [ABSTRACT FROM AUTHOR]

A widely applicable approach was developed to synthesize ketones, esters, amides via the oxidative C−C bond cleavage of readily available alkyl aldehydes. Green and abundant molecular oxygen (O2) was used as the oxidant, and base metals (cobalt and copper) were used as the catalysts. This strategy can be extended to the one‐pot synthesis of ketones from primary alcohols and α‐ketoamides from aldehydes. [ABSTRACT FROM AUTHOR]

Two highly efficient metal‐organic framework catalysts TJU‐68‐NHPI and TJU‐68‐NDHPI have been successfully synthesized through solvothermal reactions of which the frameworks are merged with N‐hydroxyphthalimide (NHPI) units, resulting in the decoration of pore surfaces with highly active nitroxyl catalytic sites. When t‐butyl nitrite (TBN) is used as co‐catalyst, the as‐synthesized MOFs are demonstrated to be highly efficient and recyclable catalysts for a novel three‐phase heterogeneous oxidation of activated C−H bond of primary and secondary alcohols, and benzyl compounds under mild conditions. Based on the high efficiency and selectivity, an environmentally benign system with good sustainability, mild conditions, simple work‐up procedure has been established for practical oxidation of a wide range of substrates. [ABSTRACT FROM AUTHOR]

Cuprous halides, best described as (CuX)n (X = Cl−, Br−, and I−) in their solid state, catalyse selective aerobic oxidation of alcohols with the assistance of both NMI (N‐methylimidazole) and TEMPO (2,2,6,6‐tetramethylpiperidine‐1‐oxyl), and the iodide generally demonstrates the highest activity, for example, in the oxidation of 1‐octanol at ambient temperature under 24 h' reaction. However, in the aerobic oxidation of benzylic alcohols, the chloride showed superiority to the iodide in that the aerobic oxidation was quantitatively completed within 3 h at ambient temperature whereas the iodide showed only about half the activity of the chloride analogue. By probing the system using electrochemistry, electric conductivity, and 1H NMR titration, it was revealed that the surprising anomaly was due to the difference in the rate of forming active species, [Cu (NMI)2X(MeCN)], from the polymeric solid in a two‐stage process. Substrates expansion of 11 benzylic alcohols indicated that CuCl/NMI/TEMPO system demonstrated quantitative conversion of benzylic alcohols into corresponding aldehydes within 3 h and showed great tolerance to the substituents on the phenyl ring of the substrates. Furthermore, electron‐withdrawing substituent was beneficial to the oxidation and could offset the steric effect at orthro‐substituent. Such a behaviour suggested that in the catalysis, increasing the acidity of the hydroxyl group (OH) of the substrates could ease the oxidation, which implied that the deprotonation via an internal pathway might be one of the rate‐determining steps. Our results also showed that the anion halide participated actively in the catalysis by coordinating to Cu(I) in the active species. [ABSTRACT FROM AUTHOR]

The accumulation of solid and liquid organic waste requires their treatment to develop energy biotechnologies and prevent environment pollution. Aim. The goal of the work was to study the efficiency of the purification of the filtrate from dissolved organic compounds by aerobic oxidation and methane fermentation. Methods. The standard methods were used to determine рН and redox potential (Eh), the gas composition, the content of short-chain fatty acids, the concentration of dissolved organic compounds counting to the total сarbon. The efficiency of two types of microbial metabolism for the degradation of soluble organic compounds of filtrate was compared. Results. The aerobic oxidation was established to provide 1.9 times more efficient removal of dissolved organic compounds, compared with the anaerobic methane fermentation. However, it provided CH 4 yield 1 L/dm3 of filtrate (сarbon concentration — 1071 mg/L). The necessity to optimize the methods for purifying filtrate to increase the efficiency of the process was determined. Conclusions. The obtained results will be the basis to develop complex biotechnology providing not only the production of environmentally friendly energy H 2 via the fermentation of solid food waste, but also the purification of filtrate to solve the ecological and energy (CH 4 production) problem of society. [ABSTRACT FROM AUTHOR]

Aerobic oxidation by using molecular oxygen (O2) as the oxidant is highly attractive, in which activating O2 to reactive oxygen species (ROS) is a prerequisite. Although some progress has been achieved in regulating ROS by heterogeneous catalysts, the strategies to efficiently control ROS in aerobic oxidation are still urgently desired. Herein, grain boundaries (GBs) in metal oxides are discovered to be able to facilely regulate ROS. Impressively, MoO3 nanocrystals with high density of GBs (MoO3‐600) deliver a mass activity of 83 mmol g‐1 h‐1 in aerobic oxidation of benzyl alcohol, 7 and 8 times as high as that of MoO3 nanoparticles without GBs and Pt/C, respectively. In addition, the selectivity of benzoic acid is 100% during whole reaction process over MoO3‐600. Mechanistic studies reveal that the oxygen atoms at GBs in MoO3‐600 are highly active to form ∙OH radicals with the generation of oxygen vacancies, while the oxygen vacancies are replenished by O2. The reaction path directly contributes to the excellent catalytic performance. [ABSTRACT FROM AUTHOR]

Defective D‐CeO2@N/C@TiO2 nanospheres, each comprising a spherical CeO2 core coated with shells of N‐doped carbon and TiO2, were successfully synthesized then evaluated for the aerobic oxidation of 5‐hydroxymethylfurfural (HMF) to 5‐hydroxymethyl‐2‐furancarboxylic acid (HMFCA). Detailed catalyst characterization studies using XRD, SEM, TEM, TG‐DTA, XPS, N2 physisorption confirmed the hierarchical core‐shell structure of the D‐CeO2@N/C@TiO2 nanospheres, with the defective surface structures created through a thermal hydrogenation process using NaBH4 promoting HMF conversion. The effect of various reaction parameters, including the reaction time, temperature, oxygen pressure, type of alkali co‐reactant and the amount of catalyst, on HMF oxidation to HMFCA over the D‐CeO2@N/C@TiO2 nanospheres were studied. Under the optimized reaction conditions (temperature 80 °C, reaction time 30 min, O2 pressure 1 MPa), a high HMF conversion of 87.8 % and a remarkable HMFCA selectivity of 100 % were obtained. In addition, the D‐CeO2@N/C@TiO2 nanosphere catalyst showed great stability over four consecutive HMF oxidation tests, implying good catalyst stability. Experimental findings were used to develop a plausible reaction mechanism for the selective oxidation of HMF on the D‐CeO2@N/C@TiO2 nanospheres. [ABSTRACT FROM AUTHOR]

The analogous three‐component synthesis strategy for substituted 1,2,4‐oxadiazole and quinazoline derivatives from readily available benzaldehyde, benzylamine and hydroxylamine or aniline has been developed. Both the cascade reaction sequences involves nucleophilic addition of C−N bond, introduction a halogen donor, nucleophilic substitution and Cu(II)‐catalyzed aerobic oxidation. This synthesis methodology demonstrated good yields, broad substrate scope and oxygen as a green oxidant. Thus, this synthesis protocol provides strategies for the construction of substituted 1,2,4‐oxadiazole and quinazolines from readily and simple starting materials. [ABSTRACT FROM AUTHOR]

A copper-based magnetic nanocatalyst has been prepared by co-precipitation method and characterized by FESEM, EDS, TEM, XRD, XRF, ICP–OES, FTIR, and BET analysis. This new nanocatalyst displays a good activity toward the aerobic oxidation of a wide range of alcohols in water. Moreover, it is recyclable up to five following runs by simple filtration without any significant loss of its catalytic activity. [ABSTRACT FROM AUTHOR]

The direct aerobic oxidation of secondarty C(sp3)-H bonds was achieved in the presence of N-hydroxyphthalimide (NHPI) and cerium ammonium nitrate (CAN) under mild conditions. Various benzylic methylenes could be oxidized to carbonyl compounds in satisfied selectivity while saturated cyclic alkanes could be further oxidized to the corresponding lactones with the catalytic system. Remarkably, 25% of isochroman was converted to corresponding ketone with a selectivity of 96%. The reaction was initiated by hydrogen atom abstraction from NHPI by cerium and nitrates under oxygen atmosphere to form PINO radicals. 2,2,6,6-Tetramethylpiperidine-1-oxyl (TEMPO) addition experiments showed that the oxidation proceeded via a complex radical chain mechanism and an ion pathway. [ABSTRACT FROM AUTHOR]

A mild and green methodology for the regiodivergent functionalization of isoquinoline‐1,3(2H,4H)‐diones under aerobic conditions was developed. Under a catalytic amount of base, heteroatom nucleophiles went through an imide opening/ring contraction sequence to give the thermodynamic controlled product; while carbon based nucleophiles led to kinetic controlled aldol type product. Moreover, the aldol type product was transformed into the benzo[c]phenanthridine core structures under transition metal free condition, which provides an environmental benign access to this framework. [ABSTRACT FROM AUTHOR]

[Display omitted] • Cu(I)-2,2′-bipyridine pre-catalysts for the aerobic benzyl alcohol oxidation. • Catalytic activity steered by ligand counter-anion interaction in acetonitrile. • Benzaldehyde selectivity depends on the initial benzyl alcohol concentration. • Ligand de-coordination found as the main deactivation path for the catalyst. "In situ" prepared cationic Cu(I) complexes bearing 2,2'-bipyridine ligands and trifluoromethylsulfonate (triflate) have been used to catalyze the aerobic oxidation of benzyl alcohol to benzaldehyde in acetonitrile in the presence of (2,2,6,6-tetramethylpiperidin-1-yl) oxyl (TEMPO). A combination of catalytic reactions, operando 1H NMR spectroscopic studies and the analysis of the molecular structure of the Cu(I) precatalysts in acetonitrile by means of DFT calculations shed light on the notable influence of counter-anion ligand interactions on the observed catalytic activity. [ABSTRACT FROM AUTHOR]

[Display omitted] • Two CTFs were prepared with or without the insertion of Thiazolo[5,4-d]thiazole (TzTz) unit. • CTF-TZDA showed elevated conduction band energy level and higher adsorption energy for substrates. • CTF-TZDA exhibited high photocatalytic aerobic oxidation ability with high selectivity. • The photocatalytic capability of triazine based CTFs could be tailored by TzTz unit. Recently, covalent triazine frameworks (CTFs) have realized versatile applications in the field of photocatalysis. Herein, two CTFs photocatalysts were designed and synthesized with or without thiazolo[5,4-d]thiazole (TzTz), an electron deficient unit, to highlight the introduction of an additional acceptor unit on the photocatalytic aerobic oxidation reaction of triazine based CTFs. Specifically, CTF-TZDA was prepared by a condensation reaction between terephthalimidamide and 4,4′-(thiazolo[5,4-d]thiazole-2,5-diyl) dibenzaldehyde (TzTz aldehyde), and similarly, CTF-FPBA was prepared between terephthalimidamide and [1,1′-biphenyl]-4,4′-dicarbaldehyde. CTF-TZDA showed high photocatalytic activities towards aerobic oxidation of both benzyl sulfides and benzyl amines to benzyl sulfoxides and benzyl imines, respectively, and the reaction was powered by blue light. A wide range of substrates can be aerobically oxidized with high yield (about 99%) and high selectivity over CTF-TZDA photocatalyst. The insertion of the TzTz unit lowered that band gap, accelerated the delocalization of π electrons, and elevated the LUMO levels of CTF-TZDA, which are beneficial to extend the light absorption range, and to promote the separation and transfer of photo-induced charge carriers. This work indicates that the insertion of an additional electron deficient unit rich in heteroatoms is considered as a feasible approach towards enhancing the photocatalytic activity of CTFs. [ABSTRACT FROM AUTHOR]

• Manganese-catalysts used for sustainable organic transformations. • Manganese catalysts became alluring to replace noble metals. • Unsaturated C O, C N, and C C bonds hydrogenation and C H funtionalisation due to polarized Mn-C bonds. • Manganese-catalysts used for hydrogen-atom transfer (HAT) reactions. • The mechanistic studies confirmed that ligand steric and electronic effects of Mn-catalysts. Manganese (Mn) is a perfect candidate as catalyst in the sustainable organic transformations. It is the second most abundant metal in earth's crust, inexpensive, and non-toxic in the nature. We expect it to replace precious metals in the novel metal catalysis. Mn-catalysts and its pincer-type complexes with bidentate and tridentate ligands have shown explosive growth since 2016. Manganese complexes, oxides, and halides have displayed excellent catalytic activity in the organic transformations. Manganese catalysts have been used in C C bond formation & C H functionalisation, late-stage fluorination, hydrosilylation, hydrogenation of unsaturated C O, and C C bonds, and cross-coupling reactions with unique reactivity and selectivity. Even then, Mn catalysis has not got the same attention as other earth-abundant metals such as Fe and Co. This review highlights the recent advances and emerging opportunities of Mn-catalyzed organic transformation based on their intrinsic mechanistic advances and potentials, covering literature up to 2024. Manganese (Mn) is a perfect candidate as catalyst in the sustainable organic transformations. It is the second most abundant metal in earth's crust, inexpensive, and non-toxic in nature. We expect it to replace the precious metals in the novel metal catalysis of organic reactions. [Display omitted] [ABSTRACT FROM AUTHOR]

An efficient and practical catalytic system for the oxidation of alcohols to aldehydes/ketones using catalytic amounts of Bi(NO3)3 and Keto-ABNO (9-azabicyclo [3.3.1]nonan-3-one N-oxyl) with air as the environmentally benign oxidant was developed. Various primary and secondary alcohols were smoothly oxidized to the corresponding products under mild conditions, and satisfactory yields were achieved. Moreover, this methodology avoids the use of a ligand and base. The gram-scale reaction was demonstrated for the oxidation of 1-phenyl ethanol, and the product of acetophenone was obtained at an isolated yield of about 94%.

A unique hybrid Polyoxometalate was synthesized, which can absorb visible light and perform photocatalytic activity. This Organic-Inorganic hybrid material was synthesized through attaching the organotin compound to the vacant polyoxometalate. Interestingly, this hybridization brought an outstanding decrement in the polyoxometalate band gap and turned this hybrid polyoxometalate to a photocatalytic compound, which can conduct catalytic reactions under visible light. In this line, we devised photoxidation of sulfides using this photocatalyst and under O2 atmosphere as a sustainable and environmental friendly oxidant. Various kinds of sulfides were investigated under optimum reaction conditions and the corresponding sulfoxide products were synthesized in good to high yields.

Despite the remarkable advances in the area of asymmetric catalytic oxidations over the past decades, the development of sustainable and environmentally benign enantioselective oxidation techniques, especially with the efficiency level similar to natural enzymes, still represents a challenge. The growing demand for enantiopure compounds and high interest to industry-relevant green technological advances continue to encourage the research pursuits in this field. Among various oxidants, molecular oxygen is ubiquitous, being available at low cost, environmentally benign and easy-to-handle material. This review highlights recent achievements in catalytic enantioselective oxidations utilizing molecular oxygen as the sole oxidant, with focus on the mechanisms of dioxygen activation and chirogenesis in these transformations.