Oxidative Organic Transformations Research Articles

Constructing Donor‐Acceptor Covalent Organic Frameworks for Highly Efficient H2O2 Photosynthesis Coupled with Oxidative Organic Transformations

The development of photocatalytic systems that enable the simultaneous production of H2O2 and value‐added organic chemicals presents a dual advantage: generating valuable products while maximizing the utilization of solar energy. Despite the potential, there are relatively few reports on photocatalysts capable of such dual functions. In this study, we synthesized a series of donor‐acceptor covalent organic frameworks (COFs), designated as JUC‐675 to JUC‐677, to explore their photocatalytic efficiency in the co‐production of H2O2 and N‐benzylbenzaldimine (BBAD). Among them, JUC‐675 exhibited exceptional performance, achieving a H2O2 production rate of 22.8 mmol g−1 h−1 with an apparent quantum yield of 15.7%, and its solar‐to‐chemical conversion efficiency was calculated to be 1.09%, marking it as the most effective COF‐based photocatalyst reported to date. Additionally, JUC‐675 demonstrated a high selectivity (99.9%) and yield (96%) for BBAD in the oxidative coupling of benzylamine. The underlying reaction mechanism was thoroughly investigated through validation experiments and density functional theory (DFT) calculations. This work represents a significant advancement in the design of COF‐based photocatalysts and the development of efficient dual‐function photocatalytic platforms, offering new insights and methodologies for enhanced solar energy utilization and the synthesis of value‐added products.

Constructing Donor‐Acceptor Covalent Organic Frameworks for Highly Efficient H2O2 Photosynthesis Coupled with Oxidative Organic Transformations

The development of photocatalytic systems that enable the simultaneous production of H2O2 and value‐added organic chemicals presents a dual advantage: generating valuable products while maximizing the utilization of solar energy. Despite the potential, there are relatively few reports on photocatalysts capable of such dual functions. In this study, we synthesized a series of donor‐acceptor covalent organic frameworks (COFs), designated as JUC‐675 to JUC‐677, to explore their photocatalytic efficiency in the co‐production of H2O2 and N‐benzylbenzaldimine (BBAD). Among them, JUC‐675 exhibited exceptional performance, achieving a H2O2 production rate of 22.8 mmol g−1 h−1 with an apparent quantum yield of 15.7%, and its solar‐to‐chemical conversion efficiency was calculated to be 1.09%, marking it as the most effective COF‐based photocatalyst reported to date. Additionally, JUC‐675 demonstrated a high selectivity (99.9%) and yield (96%) for BBAD in the oxidative coupling of benzylamine. The underlying reaction mechanism was thoroughly investigated through validation experiments and density functional theory (DFT) calculations. This work represents a significant advancement in the design of COF‐based photocatalysts and the development of efficient dual‐function photocatalytic platforms, offering new insights and methodologies for enhanced solar energy utilization and the synthesis of value‐added products.

Oxidative Organic Transformations Photocatalyzed by NDI in Visible Light.

In this work, we report the synthesis and photocatalytic properties of N,N-bis(n-hexyl)-2-bromo-6-(n-hexylamino)-1,4,5,8-naphthalenetetracarboxylic diimide photocatalyst, NDI-PC, in visible light. In the presence of air or oxidant, NDI-PC efficiently enables multiple photooxygenations of isoquinolines, thiocyanation of phenylimidazopyridines, functionalization of quinolinones by allowing regioselective installation of an SCN, SeCN, SPh, SePh, Cl, Br, or I group at the C-3 position, and isomerization of alkenes. Mechanistic investigations suggest an oxidative photoredox process for oxygenation and C-H functionalization, while isomerization is believed to proceed through a photosensitization pathway.

Ceria nanocatalyst-supported oxidative organic transformations of aromatic alcohols and p-nitrotoluene

Hydrothermally derived nanocubes of CeO2(10 nm) were explored as an efficient heterogeneous catalyst in the partial oxidation of aromatic alcohols to the corresponding aldehydes and aerobic oxidation ofp-nitrotoluene top-nitrobenzoic acid. The CeO2nanocatalyst was characterized by x-ray diffraction, transmission electron microscopy (TEM), energy dispersive spectroscopy, x-ray photoelectron spectroscopy, Brunauer-Emmett-Teller (BET) surface area analysis, Fourier transform infrared spectroscopy, thermal gravimetric analysis and ultraviolet-visible spectroscopy. TEM/high-resolution TEM micrographs reveal a morphology of mostly cubic nanostructures with exposed highly active {100} and {110} facets. The surface area of nanoceria was determined by BET analysis and found to be 33.8 m2g-1. To demonstrate the universality of the catalytic system, the selective oxidation of different substrates of benzylic alcohol and complete oxidation ofp-nitrotoluene was investigated under mild conditions. Absolute selectivity towards their respective aldehydes was found to be 99.50% (benzaldehyde), 90.18% (p-chlorobenzaldehyde), 99.71% (p-nitrobenzaldehyde), 98.10% (p-fluorobenzaldehyde), 94.66% (p-anisaldehyde) and 86.14% (cinnamaldehyde). Moreover, the catalytic oxidative transformation of nitrotoluene results in 100% conversion with 99.29% selectivity towards nitrobenzoic acid.

Versatile Metal-Free Photocatalysts Based on 3D Covalent Organic Frameworks Capable of Reductive and Oxidative Organic Transformations and Polymerizations

Versatile Metal-Free Photocatalysts Based on 3D Covalent Organic Frameworks Capable of Reductive and Oxidative Organic Transformations and Polymerizations

A persistent radical anion naphthalenediimide-based hybrid material for near-infrared photothermal conversion and photocatalytic oxidative organic transformations

A naphthalenediimide-based hybrid material was designed and prepared, which exhibits NIR photothermal conversion and promotes the photocatalytic hydroxylation of arylboronic acids and C-3 thiocyanation of indoles.

Design, Synthesis, and Applications of a Vanadium Complex: An Effective Catalyst for the Direct Conversion of Alcohols and Aldehydes to Esters.

A novel bench-stable V-catalyst [(L2)VIVO](ClO4) was synthesized and characterized by X-ray diffraction (XRD) analysis and FT-IR, UV-visible, and EPR spectroscopies, which confirmed its excellent catalytic activity. In application, aldehydes are rapidly converted into their corresponding esters without additives in a one-pot manner using a newly developed catalyst [(L2)VIVO](ClO4) and H2O2 as a green oxidant. The developed method is compatible with a broad range of densely substituted aldehydes and allows for the facile preparation of aliphatic, aromatic, and heterocyclic esters, including esters derived from CD3OD, methanol, ethanol, iso-propanol, n-butanol, sec-butyl alcohol, and propargylic alcohol. Gratifyingly, numerous alcohols also directly converted to their corresponding esters in a one-pot manner. We disclose herein the direct conversion of two different functionalities (alcohols and aldehydes) into esters (33 examples) with satisfactory yields, showing the potential of the developed catalyst toward varied oxidative organic transformations in a one-pot manner.

(Invited) Why Is Pacman so Hungry? Femtosecond M-Edge XANES Explains the Low Quantum Yield of µ-Oxo Bis(Fe Porphyin) Photocatalysts

Bridged μ-oxo iron bisporphyrins serve as photocatalysts for oxidative organic transformations, but suffer from low quantum efficiency. This low performance has been primarily attributed to the short lifetime of Fe(II)/Fe(IV)=O state formed after LMCT excitation, but a competing proposal claims that the majority photoproduct is a catalytically inactive ligand-centered ion pair. We use femtosecond optical and M2,3-edge XANES spectroscopy to investigate the early photodynamics of the μ-oxo iron bisporphyrin, (TPPFe)2O, providing evidence for the preferential formation of an TPPFe(III)+/TPPFe(III)-O- ion pair state instead of the desired TPPFe(II)/TPPFe(IV)=O. This work provides new guidance for catalyst design, suggesting that the excited-state potential surfaces must be redesigned to promote formation of the catalytically active state.

Persistent radical cation sp2 carbon-covalent organic framework for photocatalytic oxidative organic transformations

Persistent radical covalent organic frameworks (COFs) have exhibited great application potential in the fields of photocatalysis, magnetism, and biology. However, there is still a lack of a simple, green, and effective way to produce persistent radical COFs. Here, we synthesized two sp2 carbon-covalent organic frameworks (sp2C-COFs) with persistent triphenylamine radical cation (TPA+•), which can be generated by simple light irradiation since the effective donor–acceptor heterojunction is formed in ordered skeleton. The number of persistent TPA+• will increase with the intensity of light irradiation and the photogenerated electrons generated simultaneously can be consumed by O2 to form reactive oxygen species, which can be then used to carry out the oxidative organic transformations under visible light. In addition, femtosecond-transient absorption spectra prove that the difference in the structure of the two radical cation sp2C-COFs will significantly influence the charge recombination rate, so that the materials show different catalytic efficiency.

Ceria Nanocatalyst Supported Oxidative Organic Transformations of Aromatic Alcohols and P-Nitrotoluene

Ceria Nanocatalyst Supported Oxidative Organic Transformations of Aromatic Alcohols and P-Nitrotoluene

Band gap engineering of amine functionalized Ag(I)-based coordination polymers and their plasmonic Ag0 coupled novel visible light driven photo-redox system for selective oxidation of benzyl alcohol

We developed a one-pot synthetic route to design Ag nanoparticles (NPs) coupled mixed ligand Ag(I) coordination polymer (CP), Ag@Ag(I)-CP (40% NH2) for photocatalysis. Initial combined (experimental and DFT) study on mixed ligand CPs demonstrates that a rational substitution of ligand L1: 1,4-benzenedicarboxylate by L2: 2 amino 1,4-benzenedicarboxylate enhances porosity and reduction of energy gap (2.9 eV) due to highest occupied crystal orbital (HOCO; + 2.4 V vs. NHE) suitable for BA oxidation selectively to benzaldehyde (BD) ((E0BA/BD = + 1.9 V). When Ag NP (~ 6–7 nm) is in-situ encapsulated on CP, formed a coupled structure Ag@Ag(I)-CP (40% NH 2), which offered advantages on BA oxidation (k (O2) = 7.4 × 10-4 min-1; yield: 19.1% BD, and k (persulfate) = 38.7 × 10-4 min-1; yield: 54.1% BD) along with significant stability, reusability and competitiveness than other Ag or precious metal NPs. The new material offers numerous possibilities for applications in oxidative organic transformations reactions. The simple synthetic strategy demonstrated in this work for the coupling of Ag(I) based coordination polymers with metal nanoparticles at the molecular scale for semiconductor like applications under visible light will accelerate extensive research in near future.

1,2,3-Triazole-based conjugated porous polymers for visible light induced oxidative organic transformations

1,2,3-Triazole contained conjugated porous polymers (CPPs) have recently emerged as a new class of efficient photocatalysts. To gain more insight into the excellent photocatalytic activity of this kind of CPPs, herein, we report the design and preparation of a series of 1,2,3-triazole-based CPPs via oxidative coupling polymerization to study their photocatalytic performance. These CPPs have donor-acceptor properties and 1,2,3-triazole serves as an electron acceptor. The resulting CPPs with thiophene, carbazole and diphenylamine as electron donor units, respectively, have distinct porosities and optoelectronic properties, and showed effective photocatalytic performance towards oxidative hydroxylation of arylboric acids and alkylation of vinylarenes with diethyl bromomalonate or bromoacetonitrile. The thiophene contained CPP was a more efficient photocatalyst for the catalytic reactions, which can be attributed to its smaller optical band gap and greater charge separation efficiency. Furthermore, PTPT has shown reliable recyclability with no significant loss in its catalytic activity.

Isotruxene-based porous polymers as efficient and recyclable photocatalysts for visible-light induced metal-free oxidative organic transformations

The first implementation of isotruxene-based porous polymers (IsoPOPs) in catalysis is described, which allows oxidative chemical transformations to be conducted with air as the benign oxidant under visible-light irradiation in a metal-free fashion.

Redox‐Mediated Alcohol Oxidation Coupled to Hydrogen Gas Formation in a Dye‐Sensitized Photosynthesis Cell

This work reports a dye‐sensitized photoelectrochemical cell (DSPEC) that couples redox‐mediated light‐driven oxidative organic transformations to reductive hydrogen (H2) formation. The DSPEC photoanode consists of a mesoporous anatase TiO2 film on FTO (fluorine‐doped tin oxide), sensitized with the thienopyrroledione‐based dye AP11, while H2 was formed at a FTO‐Pt cathode. Irradiation of the dye‐sensitized photoanode transforms 2,2,6,6‐tetramethylpiperidine 1‐oxyl (TEMPO) to the oxidized TEMPO (TEMPO+), which acts as a chemical oxidant for the conversion of benzyl alcohol. The TEMPO0/+ couple, previously used as redox mediator in DSSC, mediates efficient electron transfer from the organic substrate to the photo‐oxidized dye. A DSPEC photoreactor was designed that allows in situ monitoring the reaction progress by infrared spectroscopy and gas chromatography. Sustained light‐driven oxidation of benzyl alcohol to benzaldehyde within the DSPEC photoreactor, using of TEMPO as mediator, demonstrated the efficiency of the device, with a photocurrent of 0.4 mA cm−2, approaching quantitative Faradaic efficiency and exhibiting excellent device stability.

Synthesis of Ni2+ cation modified TS-1 molecular sieve nanosheets as effective photocatalysts for alcohol oxidation and pollutant degradation

Improvement of the charge separation of titanosilicate molecular sieves is critical to their use as photocatalysts for oxidative organic transformations. In this work, MFI TS-1 molecular sieve nanosheets (TS-1 NS) were synthesized by a low-temperature hydrothermal method using a tailored diquaternary ammonium surfactant as the structure-directing agent. Introducing Ni2+ cations at the ion-exchange sites of the TS-1 NS framework significantly enhanced its photoactivity in aerobic alcohol oxidation. The optimized Ni cation-functionalized TS-1 NS (Ni/TS-1 NS) provide impressive photoactivity, with a benzyl alcohol (BA) conversion of 78.9% and benzyl aldehyde (BAD) selectivity of 98.8% using O2 as the only oxidant under full light irradiation; this BAD yield is approximately six times greater than that obtained for bulk TS-1, and is maintained for five runs. The excellent photoactivity of Ni/TS-1 NS is attributed to the significantly enlarged surface area of the two-dimensional morphology TS-1 NS, extra mesopores, and greatly improved charge separation. Compared with bulk TS-1, Ni/TS-1 NS has a much shorter charge transfer distance. The as-introduced Ni species could capture the photoelectrons to further improve the charge separation. This work opens the way to a class of highly selective, robust, and low-cost titanosilicate molecular sieve-based photocatalysts with industrial potential for selective oxidative transformations and pollutant degradation.

Benzodithiophenedione‐Based Conjugated Microporous Polymer Catalysts for Aerobic Oxidation Reactions Driven by Visible‐Light

AbstractSearching for catalysts that are cost‐effective, efficient, recyclable and capable of harvesting light for aerobic oxidation reactions remains a challenge for material scientists. Herein, we have designed and developed a task‐specified heterogeneous photocatalyst, which was built by a two‐step reaction starting from a commercially available compound named benzo[1,2‐b:4,5‐b′] dithiophene‐4,8‐dione (BDD). Through the molecular engineering strategy integrating an electron‐output BDD, the obtained BDD‐based conjugated microporous polymer (CMP‐BDD) exhibits efficient visible light absorption due to the incorporation of a BDD moiety and an extended π‐conjugated structure. Remarkably, the CMP‐BDD showed an effective heterogeneous catalytic activity for typical oxidative organic transformations, such as selective oxidation of organic sulfides, and thiocyanation of imidazoheterocycles in the presence of light and oxygen. In addition, the CMP‐BDD exhibited good recyclability in the photocatalytic oxidation of thioanisole, which can be used for at least five times without substantial decline in photocatalytic activity, demonstrating its promising potential in industrial applications.

(Ar-tpy)RuII(ACN)3: A Water-Soluble Catalyst for Aldehyde Amidation, Olefin Oxo-Scissoring, and Alkyne Oxygenation.

The synthetic chemists always look for developing new catalysts, sustainable catalysis, and their applications in various organic transformations. Herein, we report a new class of water-soluble complexes, (Ar-tpy)RuII(ACN)3, utilizing designed terpyridines possessing electron-donating and -withdrawing aromatic residues for tuning the catalytic activity of the Ru(II) complex. These complexes displayed excellent catalytic activity for several oxidative organic transformations including late-stage C-H functionalization of aldehydes with NH2OR to valuable primary amides in nonconventional aqueous media with excellent yield. Its diverse catalytic power was established for direct oxo-scissoring of a wide range of alkenes to furnish aldehydes and/or ketones in high yield using a low catalyst loading in the water. Its smart catalytic activity under mild conditions was validated for dioxygenation of alkynes to highly demanding labile synthons, 1,2-diketones, and/or acids. This general and sustainable catalysis was successfully employed on sugar-based substrates to obtain the chiral amides, aldehydes, and labile 1,2-diketones. The catalyst is recovered and reused with a moderate turnover. The proposed mechanistic pathway is supported by isolation of the intermediates and their characterization. This multifaceted sustainable catalysis is a unique tool, especially for late-stage functionalization, to furnish the targeted compounds through frequently used amidation and oxygenation processes in the academia and industry.

有機ニトロキシルラジカルを用いた酸化的分子変換の最近の進歩

有機ニトロキシルラジカルを用いた酸化的分子変換の最近の進歩

Cationic Polycarbazole Networks as Visible-Light Heterogeneous Photocatalysts for Oxidative Organic Transformations

Photoredox catalysis has aroused great interest from chemists, as it offers a powerful tool for organic synthesis. Cationic polycarbazole networks (CPOP-28 and CPOP-29) were prepared via simple oxidative coupling reaction and applied as heterogeneous photocatalysts for a wide range of oxidative organic transformations, including oxidation of sulfides, hydroxylation of arylboronic acids, and cross-dehydrogenative coupling reactions, in the presence of visible light and air. Remarkably, photocatalytic activities are enhanced by ingenious introduction of trifluoromethyl groups to the polymeric network CPOP-29. The effects of the trifluoromethyl group on photocatalytic activities were elucidated in terms of photophysical and electrochemical properties. The appealing photocatalytic performance of the trifluoromethylated polymer is ascribed to superior light-absorption ability, longer fluorescence lifetime, and stronger oxidative capability. In addition, the photocatalysts showed good recyclability and could be...

Polymer-Supported Photosensitizers for Oxidative Organic Transformations in Flow and under Visible Light Irradiation

A 2,1,3-benzothiadiazole (BTZ)-based vinyl cross-linker was synthesized and copolymerized with large excesses of styrene using free radical polymerization to deliver heterogeneous triplet photosensitizers in three distinct physical formats: gels, beads, and monoliths. These photosensitizers were employed for the production of singlet oxygen (1O2) and for the aerobic hydroxylation of arylboronic acids via superoxide radical anion (O2•–), whereby the materials demonstrated good chemical and light stability. BTZ-containing beads and monoliths were exploited as photosensitizers in a commercial flow reactor, and 1O2 production was also demonstrated using direct sunlight irradiation, with a conversion rate comparable to the rates achieved when a 420 nm LED module is used as the source of photons.