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Polyether amines are versatile compounds characterized by a flexible structure, consisting of polyoxypropylene and polyoxyethylene as the backbone, with amine groups at each end. They have widespread applications in various industrial processes and daily life. Despite their versatility, the utilization of polyether amines as base catalysts is rare. In this study, one kind of three-arm polyether amine 1 was employed as an environmentally friendly, cost-effective catalyst for the aerobic oxidation of thiophenols, leading to the synthesis of disulfides. The oxidative coupling of thiols serves as a fundamental pathway for the production of disulfides, which are vital in both chemical and biological processes. In contrast to known methods for thiol oxidation, this polyether amine-based catalytic process eliminates the need for expensive stoichiometric oxidants and minimizes the formation of over-oxidized by-products. Using a mere 0.5 mol % of the polyether amine 1 as the catalyst, a remarkable > 96% yield was achieved for all 16 tested substrates, encompassing a diverse range of functional groups, under the catalytic aerobic oxidation conditions. Furthermore, it is noteworthy that over 90% of the polyether amine catalyst can be efficiently recovered for reuse without loss of activity, making this a sustainable and cost-effective catalytic approach.

The photo-induced aerobic oxidation of C–H bonds has become an increasingly valuable strategy in organic synthesis, offering a green and efficient method for introducing oxygen into organic molecules. The utilization of molecular oxygen as an oxidant, coupled with visible-light photocatalysis, has gained significant attention due to its sustainability, atom economy, and environmentally benign nature. This review highlights the recent advancements in the field, focusing on the development of metal-free and transition-metal-based photocatalytic systems and novel photosensitizers capable of promoting selective C–H bond oxidation. The mechanistic pathways involved in various substrate oxidations, including benzylic, alkyl, alkene, and alkyne C–H bond transformations, are discussed. This review concludes with insights into the potential for integrating photocatalysis with renewable energy sources, positioning photo-induced aerobic oxidation as a cornerstone of sustainable chemical processes.

Our novel binuclear complex-anchored Ru(III) catalyst, designed and assembled by sonicating 2,2′-(4,6-dihydroxy-1,3-phenylene)bis(1H-benzo[d]imidazole-4-carboxylic acid), Ru(DMSO)4Cl2 and 4-methylpyridine, demonstrates remarkable efficiency and selectivity. It promotes one-pot reactions, including active methylenes and benzyl alcohols in water, via a tandem aerobic oxidation/Knoevenagel condensation process, yielding benzylidene malononitrile in excellent yields. The catalyst’s ability to oxidize benzyl alcohols to aldehydes, which then undergo Knoevenagel condensation with active methylenes, makes it a multifunctional catalyst. Notably, the catalyst can be successfully retrieved and recycled for five successive rounds with no significant decrease in catalytic efficiency. The ICP study showed that no catalyst leaching was observed, indicating that the designed catalyst is indeed heterogeneous. The Ru catalyst outperformed other documented catalysts in terms of lower dose, shorter duration, decreased working temperature, and the absence of dangerous additives. This demonstrates the catalyst’s robustness and sustainability, making it a promising candidate for future organic conversions and industrial uses.

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 [Sm6O(OH)8(H2O)24]I8(H2O)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.

We report on the high potential of a honeycomb reactor for the use in aerobic oxidation under continuous-flow conditions. The honeycomb reactor is made of porous material with narrow channels separated by porous walls allowing for high density accumulation in the reactor. This structure raised the mixing efficiency of a gas–liquid reaction system, and it effectively accelerated the aerobic oxidation of benzyl alcohols to benzaldehydes under continuous-flow conditions. This reactor is a promising device for streamlining aerobic oxidation with high process safety because it is a closed system.

We present a new undergraduate teaching experiment inspired by recent scientific advances toward the sustainable synthesis of deep blue fluorescent benzofuroindoles via the catalytic aerobic oxidation [3+2] cyclization of phenol and indole. The experiment teaches basic theoretical knowledge of organic chemistry, such as Lewis acid catalysis, electrophilic substitution, conjugate addition, and practical skills, including thin layer chromatography, column chromatography purification, UV-Vis absorption/fluorescence spectroscopy, and nuclear magnetic resonance spectroscopy. It integrates the ideological elements of green chemistry, environmental protection, safety, and sustainable chemistry, among others, and provides comprehensive training in scientific thinking, scientific inquiry, and complex problem solving in synthetic chemistry. [ABSTRACT FROM AUTHOR]

During the synthetic studies toward 5,6,7,3′,4′-monomethoxytetrahydroxyflavones, a concise pedalitin synthesis procedure was achieved. As previously reported, 6-hydroxy-2,3,4-trimethoxyacetophenone was prepared by Friedel–Crafts acylation of 1,4-dihydroxy-2,6-dimethoxybenzene with boron trifluoride diethyl etherate in acetic acid. When aldol condensation of 6-hydroxy-2,3,4-trimethoxyacetophenone 2b with vanillin was performed in basic conditions, it produced 2′-hydroxychalcone 3b, and, surprisingly, along with 3-hydroxyflavone 4 in a considerable amount. We propose that this oxidative cyclization is presumably due to the contribution of a quinone methide, likely to be subjected to aerobic oxidation. The chalcone was then subjected to oxidative cyclization with iodine in dimethyl sulfoxide to afford flavone 5 in good yield. To our delight, serial demethylation of the three methoxy groups at the 5-, 6-, and 3′-positions of 5 proceeded smoothly to produce pedalitin 1, under hydrogen bromide solution (30% in acetic acid). The crystal structures of 3-hydroxyflavone 4 and pedalitin tetraacetate 6 were unambiguously determined by X-ray crystallography.

The aim of this work was to fabricate a new heterogeneous catalyst as zinc ferrite (ZF) supported on gamma-alumina (γ-Al2O3) for the conversion of cyclic ethers to the corresponding, more valuable lactones, using a solvent-free method and O2 as an oxidant. Hence, the ZF@γ-Al2O3 catalyst was prepared using a deposition–coprecipitation method, then characterized using TEM, SEM, EDS, TGA, FTIR, XRD, ICP, XPS, and BET surface area, and further applied for aerobic oxidation of cyclic ethers. The structural analysis indicated spherical, uniform ZF particles of 24 nm dispersed on the alumina support. Importantly, the incorporation of ZF into the support influenced its texture, i.e., the surface area and pore size were reduced while the pore diameter was increased. The product identification indicated lactone compound as the major product for saturated cyclic ether oxidation. For THF as a model reaction, it was found that the supported catalyst was 3.2 times more potent towards the oxidation of cyclic ethers than the unsupported one. Furthermore, the low reactivity of the six-membered ethers can be tackled by optimizing the oxidant pressure and the reaction time. In the case of unsaturated ethers, deep oxidation and polymerization reactions were competitive oxidations. Furthermore, it was found that the supported catalyst maintained good stability and catalytic activity, even after four cycles.

Iodine is a well-known oxidant that is widely used in organic syntheses. Thiol oxidation by stoichiometric iodine is one of the most commonly employed strategies for the synthesis of valuable disulfides. While recent advancements in catalytic aerobic oxidation conditions have eliminated the need for stoichiometric oxidants, concerns persist regarding the use of toxic or expensive catalysts. In this study, we discovered that iodine can be used as a cheap, low-toxicity catalyst in the aerobic oxidation of thiols. In the catalytic cycle, iodine can be regenerated via HI oxidation by O2 at 70 °C in EtOAc. This protocol harnesses sustainable oxygen as the terminal oxidant, enabling the conversion of primary and secondary thiols with remarkable efficiency. Notably, all 26 tested thiols, encompassing various sensitive functional groups, were successfully converted into their corresponding disulfides with yields ranging from >66% to 98% at a catalyst loading of 5 mol%.

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.

The framework of 1,3,4-oxadiazine is crucial for numerous bioactive molecules, but only a limited number of synthetic methods have been reported for its production. In 2015, Wang’s group developed a 4-(dimethylamino)pyridine (DMAP)-catalyzed [2 + 4] cycloaddition of allenoates with N-acyldiazenes, which provided an atom-efficient route for 1,3,4-oxadiazines. However, the practicality of this method was limited by the instability of N-acyldiazenes as starting materials. Building upon our ongoing research about the aerobic oxidation of hydrazides and their synthetic applications, we hypothesized that aerobic oxidative cycloadditions using acylhydrazides instead of N-acyldiazenes may provide a more practical synthetic route for 1,3,4-oxadiazines. In this manuscript, we describe a one-pot synthetic protocol for 1,3,4-oxadiazines from acylhydrazides and allenoates. The developed one-pot protocol consists of aerobic oxidations of acylhydrazides into N-acyldiazenes using NaNO2 and HNO3, followed by the DMAP-catalyzed cycloaddition of allenoate with the generated N-acyldiazenes. A variety of 1,3,4-oxadiazines were produced in good to high yields. In addition, the practicality of the developed method was demonstrated by a gram-scale synthesis of 1,3,4-oxadiazine.

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.

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%.

The use of molecular oxygen in palladium‐catalyzed oxidation reactions is highly widespread in organic chemistry. However, the direct reoxidation of palladium by O2 is often kinetically unfavored, thus leading the deactivation of the palladium catalyst during the catalytic cycle. In the present work, we report a highly selective palladium‐catalyzed carbocyclization of bisallenes to seven‐membered heterocycles under atmospheric pressure of O2. The use of a homogenous hybrid catalyst (Co(salophen)‐HQ, HQ=hydroquinone) significantly promotes efficient electron transfer between the palladium catalyst and O2 through a low‐energy pathway. This aerobic oxidative transformation shows broad substrate scope and functional group compatibility and allowed the preparation of O‐containing seven‐membered rings in good yields in most cases. [ABSTRACT FROM AUTHOR]

Oxosulfonylation is a difunctionalization protocol where oxo and sulfonyl groups are introduced in one step to construct ketosulfones and N‐acylsulfonamides from simple and readily accessible reagents. The development of oxosulfonylation methods has gained significant attention due to their importance in organic and medicinal chemistry. This review article provides a brief and concise overview of the current status and latest methodologies using green oxidant and sulfonyl sources for oxosulfonylation reactions developed in the last two decades. [ABSTRACT FROM AUTHOR]

A stable, earth-abundant, reusable cobalt-based heterogeneous catalyst is developed for the oxidative esterification of alcohols under ambient conditions, featuring broad substrate scope, providing good to excellent product yields. This protocol enables easy recyclability of the catalyst, measured up to five times without significant loss of efficiency. The active sites of Co-N-Si/AC are proposed to be Co-N species.

Nitrogen heteroarenes form an important class of compounds which can be found in natural products, synthetic drugs, building blocks etc. Among the diverse strategies that were developed for the synthesis of nitrogen heterocycles, oxidative dehydrogenation is extremely effective. This review discusses various oxidative dehydrogenation strategies of C–C and C–N bonds to generate nitrogen heteroarenes from their corresponding heterocyclic substrates. The strategies are categorized under stoichiometric and catalytic usage of reagents that facilitate such transformations. The application of these strategies in the synthesis of nitrogen heteroarene natural products and synthetic drug intermediates are also discussed. We hope this review will arouse sufficient interest among the scientific community to further advance the application of oxidative dehydrogenation in the synthesis of nitrogen heteroarenes.

4-Sulfonyl-1,2,3-triazole scaffolds possess promising bioactivities and applications as anion binders. However, these structures remain relatively unexplored and efficient synthetic procedures for their synthesis remain desirable. A practical room-temperature, aerobic copper-catalyzed three-component reaction of aromatic ketones, sodium sulfinates, and azides is reported. This procedure allows for facile access to 4-sulfonyl-1,5-disubstituted-1,2,3-triazoles in yields ranging from 34 to 89%. The reaction proceeds via a sequential aerobic copper(II)chloride-catalyzed oxidative sulfonylation and the Dimroth azide–enolate cycloaddition.

We herein describe an environmentally friendly microwave-assisted oxidative esterification of alcohols and aldehydes in the presence of molecular oxygen and a heterogeneous catalysis (Pd/C, 5 mol %). This efficient and ligandless conversion procedure does not require the addition of an organic hydrogen acceptor. The reaction rate is strongly enhanced by mild dielectric heating. Furthermore, it is a versatile green procedure which generally enables the isolation of esters to be carried out by simple filtration in almost quantitative yields.

Transition-metal catalyzed oxidation reactions are central components of organic chemistry. On behalf of green and sustainable chemistry, molecular oxygen (O2) has been considered as an ideal oxidant due to its natural, inexpensive, and environmentally friendly characters, and therefore offers attractive academic and industrial prospects. In recent years, some powerful organic oxidation methods have been continuously developed. Among them, the use of molecular oxygen (O2) as a green and sustainable oxidant has attracted considerable attentions. However, the development of new transition metal-catalyzed protocols using O2 as an ideal oxidant is highly desirable but very challenging because of the low standard electrode potential of O2 to reoxidize the transition-metal catalysts. In this Account, we highlight some of our progress toward the use of transition-metal catalyzed aerobic oxidation reactions. Through the careful selection of ligand and the acidic additives, we have successfully realized the reoxidation of Cu, Pd, Mn, Fe, Ru, Rh, and bimetallic catalysts under O2 or air atmosphere (1 atm) for the oxidative coupling, oxygenation reactions, oxidative C-H/C-C bond cleavage, oxidative annulation, and olefins difunctionalization reactions. Most of the reactions can tolerate a range of functional groups. These methods provide new strategies for the green synthesis of alkynes, ( α-keto)amides/esters, ketones/diones, O/N-heterocycles, β-azido alcohols, and nitriles. The high efficiency, low cost, and simple operation under air make these methodologies very attractive and practical. We will also discuss the mechanisms of these reactions which might be useful to promote the new type of aerobic oxidative reaction design. [ABSTRACT FROM AUTHOR]

Transition-metal catalyzed oxidation reactions are central components of organic chemistry. On behalf of green and sustainable chemistry, molecular oxygen (O2) has been considered as an ideal oxidant due to its natural, inexpensive, and environmentally friendly characters, and therefore offers attractive academic and industrial prospects. In recent years, some powerful organic oxidation methods have been continuously developed. Among them, the use of molecular oxygen (O2) as a green and sustainable oxidant has attracted considerable attentions. However, the development of new transition metal-catalyzed protocols using O2 as an ideal oxidant is highly desirable but very challenging because of the low standard electrode potential of O2 to reoxidize the transition-metal catalysts. In this Account, we highlight some of our progress toward the use of transition-metal catalyzed aerobic oxidation reactions. Through the careful selection of ligand and the acidic additives, we have successfully realized the reoxidation of Cu, Pd, Mn, Fe, Ru, Rh, and bimetallic catalysts under O2 or air atmosphere (1 atm) for the oxidative coupling, oxygenation reactions, oxidative C-H/C-C bond cleavage, oxidative annulation, and olefins difunctionalization reactions. Most of the reactions can tolerate a range of functional groups. These methods provide new strategies for the green synthesis of alkynes, ( α-keto)amides/esters, ketones/diones, O/N-heterocycles, β-azido alcohols, and nitriles. The high efficiency, low cost, and simple operation under air make these methodologies very attractive and practical. We will also discuss the mechanisms of these reactions which might be useful to promote the new type of aerobic oxidative reaction design. [ABSTRACT FROM AUTHOR]

The aerobic oxidative cleavage of 1,2-diols using a heterogeneous catalyst only based on earth-abundant metals manganese and sodium is reported for the first time. This reusable catalyst cleaves a variety of substrates into aldehydes or ketones with high selectivity. The reaction requires small catalytic loadings and is performed under mild conditions using ambient pressure O2 or air as the oxidant while producing water as the only by-product. Mechanistic investigations reveal a monodentate, two-electron oxidative fragmentation process involving a MnIV species. The eco-friendly, innocuous catalyst is compatible with a wide range of functional groups and conditions, making it highly competitive with classical reagents, such as periodic acid or lead tetraacetate, as a preferred method for activated 1,2-diols. [ABSTRACT FROM AUTHOR]

In recent years, visible-light-driven organic reactions have been experiencing a significant renaissance in response to topical interest in environmentally friendly green chemical synthesis. The transformations using inexpensive, readily available visible-light sources have come to the forefront in organic chemistry as a powerful strategy for the activation of small molecules. In this review, we focus on recent advances in the development of visible-light-driven organic reactions, including aerobic oxidation, hydrogen-evolution reactions, energy-transfer reactions and asymmetric reactions.These key research topics represent a promising strategy towards the development of practical, scalable industrial processes with great environmental benefits. [ABSTRACT FROM AUTHOR]

This publication describes a highly selective oxidation of aldehydes to the corresponding acids or esters. The reaction proceeds under metal-free conditions by using N-heterocyclic carbenes as organocatalysts in combination with environmentally friendly oxygen as the terminal oxidation agent.

The Mn(III)-initiated aerobic oxidation of heterocyclic 1,3-dicarbonyl compounds, such as 4-alkyl-1,2-diphenylpyrazolidine-3,5-diones, 1,3-dialkylpyrrolidine-2,4-diones, 3-alkyl-1,5-dimethylbarbituric acids, and 3-butyl-4-hydroxy-2-quinolinone gave excellent to good yields of the corresponding hydroperoxides, which were gradually degraded by exposure to the metal initiator after the reaction to afford the corresponding alcohols. The synthesis of 30 heterocyclic 1,3-dicarbonyl compounds, the corresponding hydroperoxides and the 10 alcohols, their characterization, and the limitations of the procedure are described. In addition, the mechanism of the hydroperoxidation and the redox decomposition of the hydroperoxides are discussed.

Pyrazolidinones were prepared in a two-step sequence starting from α-hydrazonocarboxylic acids. After a four-component Ugi coupling, the resulting hydrazone was engaged in a copper triggered [3 + 2] cycloaddition/aerobic oxidation cascade.

A highly efficient transition-metal-free catalytic system Br2/NaNO2/H2O has been developed for a robust and economic acid-free aerobic oxidation of sulfides. It is noteworthy that the sulfide function reacts under mild conditions without over-oxidation to sulfone. The role of NaNO2as an efficient NO equivalent for the activation of molecular oxygen was identified. Under the optimal conditions, a broad range of sulfide substrates were converted into their corresponding sulfoxides in high yields by molecular oxygen. The present catalytic system utilizes cheap and readily available agents as the catalysts, exhibits high selectivity for sulfoxide products and releases only innocuous water as the by-products.

Nitrogen-doped carbon materials have been gaining increasing interest as metal-free catalysts. In this article, the authors have briefly introduced their recent studies on the utilization of nitrogen-doped activated carbon (N-AC) for several organic synthesis reactions, which include base catalyzed reactions of Knoevenagel condensation and transesterification, aerobic oxidation of xanthene and alcohols, and transfer hydrogenation of nitrobenzene, 3-nitrostyrene, styrene, and phenylacetylene with hydrazine. Doped-nitrogen species existed on the AC surface in different structures. For example, pyridine-type nitrogen species appear to be involved in the active sites for Knoevenagel condensation and for the oxidation of xanthene, while graphite-type nitrogen species appear to be involved for the oxidation of alcohols. Being different from these reactions, both surface nitrogen and oxygen species are involved in the active sites for the hydrogenation of nitrobenzene. N-AC was practically inactive for the transfer hydrogenation of vinyl and ethynyl groups, but it can catalyze those hydrogenation reactions assisted by co-existing nitrobenzene. Comparison of N-AC with conventional catalysts shows that N-AC can alternate with conventional solid base catalysts and supported metal catalysts for the Knoevenagel condensation and oxidation reactions.

3-Alkyl-substituted 2,4-pyrrolidinediones were directly oxidized under very mild manganese(III)-catalyzed aerobic oxidation conditions to give the corresponding 3-hydroperoxy-2,4-pyrrolidinediones in quantitative yields. The scope and limitations for the synthesis of the hydroperoxyprrolidinediones are described. [ABSTRACT FROM PUBLISHER]

Abstract: An amphiphilic polystyrene-poly(ethylene glycol) (PS-PEG) resin-dispersion of nanoparticles of palladium was designed and prepared with a view toward use for catalysis in water. The amphiphilic PSPEG resin-dispersion of nanoparticles of palladium exhibited high catalytic performance in the hydrodechlorination of chloroarenes under aqueous conditions. The amphiphilic resin-supported nanopalladium particle also catalyzed alcohol oxidation, which is one of the most fundamental and important yet immature processes in organic chemistry, in water under an atmospheric pressure of oxygen gas to form aldehydes, ketones, and carboxylic acids. [Copyright &y& Elsevier]