Mild Conditions Research Articles

Photocatalytic Three-Component Acylcarboxylation of Alkenes with CO2.

γ-Keto acid is a valuable chemical motif in a wide range of fields including organic, biological, and medicinal chemistry. However, its single-step synthesis is challenging because of the mismatch of the carbonyl polarity and low tolerance of carboxylic acids. Herein, we report the single-step syntheses of γ-keto acids using alkenes and CO2. Our photocatalytic system enabled the transformation of alkenes under mild conditions in high yields (up to 95%) with broad substrate generality (35 examples).

Iodine-Catalyzed [5 + 1] Carbonylation of 2-Alkenyl/Pyrrolylanilines with CS2 as the Carbonylating Reagent.

Novel metal-free iodine (I2)-catalyzed [5 + 1] carbonylation of 2-alkenyl/pyrrolylanilines with carbon disulfide (CS2) as the carbonylating reagent has been developed. This innovative method allows for the synthesis of valuable derivatives such as 4-aryl-2-quinolinones and pyrrolyl-fused quinoxalinones. Notably, this work represents the first instance where CS2 has been utilized as a carbonylating reagent source. The protocol demonstrates the utilization of various substrates, leading to diverse reactions that afford excellent yields under mild conditions. The method also shows good compatibility with functional groups present in the substrates, further enhancing its synthetic utility. Importantly, the developed reaction exhibits scalability, enabling gram-scale synthesis, and shows promise for the synthesis of druglike molecules. In this catalytic system, CS2 serves as the carbonyl source, while dimethyl sulfoxide plays multiple roles, including acting as an oxidant and a solvent. Mechanistic studies have been conducted to elucidate the underlying processes, with the formation of quinolone-2-thiones identified as crucial intermediates, facilitating the carbonylation annulation process.

Plasma-catalytic direct oxidation of methane to methanol over Cu-MOR: Revealing the zeolite-confined Cu2+ active sites

Efficient methane conversion to methanol remains a significant challenge in chemical industry. This study investigates the direct oxidation of methane to methanol under mild conditions, employing a synergy of non-thermal plasma and Cu-MOR (Copper-Mordenite) catalysts. Catalytic tests demonstrate that the Cu-MOR IE-3 catalyst (i.e., prepared by three cycles of ion exchange) exhibits superior catalytic performance (with 51 % methanol selectivity and 7.9 % methane conversion). Conversely, the Cu-MOR catalysts prepared via wetness impregnation tend to over-oxidize CH4 to CO and CO2. Through systematic catalyst characterizations (XRD, TPR, UV–Vis, HRTEM, XPS), we elucidate that ion exchange mainly leads to the formation of zeolite-confined Cu2+ species, while wetness impregnation predominantly results in CuO particles. Based on the catalytic performance, catalyst characterizations and in-situ FTIR spectra, we conclude that zeolite-confined Cu2+ species serve as the active sites for plasma-catalytic direct oxidation of methane to methanol.

Palladium-Catalyzed Carbonylative Sonogashira Coupling of Aryl Thianthrenium Salts with Arylalkynes.

Alkynones are valuable compounds with applications in various areas. In this work, we developed an efficient carbonylation procedure for the carbonylative cross-coupling of aryl thianthrenium salts with aromatic alkynes. Various useful alkynones were produced in moderate to excellent yields under mild conditions. Notably, among the various tolerated functional groups, the bromide group can be maintained, which is ready for further coupling reactions.

Rapid Synthesis of Highly Substituted 1,6-Naphthyridines Via Heteroaryl Ditriflates.

We report the discovery of a convenient and efficient method for the synthesis of highly substituted 1,6-naphthyridines. A tandem nitrile hydration/cyclization procedure was developed to access 1,6-naphthyridine-5,7-diones under mild conditions. Subsequently, we have found that ditriflation of these intermediates provides 1,6-naphthyridine-5,7-ditriflates which are bench-stable but highly reactive intermediates that can be engaged in one-pot difunctionalization reactions leading to diverse drug-like products in rapid fashion.

Copper-Catalyzed Dual Remote Asymmetric Vinylogous Alkynylallylic Substitution of Yne-Allylic Esters with Coumarins.

Chiral coumarins and their derivatives are ubiquitous structural motifs found in an array of biologically and therapeutically active natural products and drugs. Herein, a highly enantioselective dual remote copper-catalyzed vinylogous alkynylallylic substitution of yne-allylic esters with coumarins has been developed. The practicality of this method is exemplified by the use of readily available starting materials; mild reaction conditions; excellent regio-, enantio-, and stereoselectivities; and the very broad substrate scope (67 examples), while the scalability and further applications of this method are illustrated by the gram-scale reaction and the series of derivations of the products.

Electrochemically Enabled Hydroxyphosphorylation of 1,3-Enynes to Access Phosphinyl-Substituted Propargyl Alcohols.

Catalytic difunctionalization with the direct activation of (O)P-H bonds has been recently established as a potentially robust platform to generate valuable organophosphorus compounds. In terms of 1,3-enynes, despite of the various catalytic methods developed for hydrophosphorylation, the radical-mediated hetero-functionalization of two different atoms has been less explored. In this study, we disclosed an electrochemically induced hydroxyphosphorylation of 1,3-enynes for the construction of phosphinyl-substituted propargyl alcohols. The system involves the direct activation of both arylphosphine oxides and oxygen in ambient air with no external metal or additive needed. The use of electrochemistry ensures the regioselective, atom-economic and eco-friendly for the difunctionalization process. This strategy highlights the advantages of mild reaction conditions, readily available starting materials and broad substrate scope, showing its practical synthetic value in organic synthesis.

A ratiometric fluorescent probe for selective detection of hypochlorite (ClO−) and gallium (III) (Ga3+) ions in environmental and food samples

Hypochlorite (ClO−) and gallium (Ⅲ) ions (Ga3+) have extensive applications in various human industries and daily activities. However, their inherent toxicity poses significant risks to environmental preservation and human well-being. Hence, the development of reliable and handy detection tools for ClO− and Ga3+ in the environment and food is crucial. In this study, a ratiometric fluorescent probe was prepared based on benzothiazolaldehyde and pyridine-2-carboxylic acid hydrazide, which exhibited exceptional performance characteristics for the selective detection of ClO− and Ga3+. These features include high specificity, low detection limits (0.28 μM for ClO−, 0.13 μM for Ga3+), mild pH conditions (pH 4–11 for ClO−, pH 6–11 for Ga3+), fast response time (within 30 s), as well as versatile applicability across different matrices such as water, soil, food, and plant samples. Additionally, this probe can be used with a smartphone color recognition app. The probe offers a convenient and effective tool for the detection of ClO− and Ga3+, demonstrating its potential application value in environmental monitoring and food safety.

Dual amplification dynamic DNA network system for CRISPR/Cas12a based p53 gene detection

BackgroundIt is estimated that over 50 % of human cancers are caused by mutations in the p53 gene. Early sensitive and accurate detection of the p53 gene is important for diagnosis of cancers in the early stage. However, conventional detection techniques often suffer from strict reaction conditions, or unsatisfied sensitivity, so we need to develop a new strategy for accurate detection of p53 gene with smart designability, multiple signal amplification in mild reaction conditions. ResultsIn this study, CRISPR/Cas system is exploited in entropy-driven catalysis (EDC) and hybridization chain reaction (CHA) dual signal amplification sensing strategies. The products of both reactions can efficiently and separately activate CRISPR/Cas12a which greatly amplifies the fluorescent signal. The method has good linearity in p53 detection with the concentration ranged from 0.1 fM to 0.5 pM with ultra-low detection limit of 0.096 fM. It also showed good performance in serum, offering potentials for early disease detection. SignificanceThe designed dual amplification dynamic DNA network system exhibits an ultra-sensitive fluorescence biosensing for p53 gene identification. The method is simple to operate and requires only one buffer for the experiment, and meanwhile shows smart designability which could be used for a wide range of markers. Thus, we believe the present work will provide a potential tool for the construction and development of sensitive fluorescent biosensors for diseases.

Catalytic micro-structured ceramic beads and efficacy evaluation through SMX degradation in PMS-activated systems

This study tackles the challenge of applying fine and nano-catalyst particles in Advanced Oxidation Processes (AOPs), primarily due to the complexities of nanoparticle removal from treated water to prevent secondary nano-hazards. We propose an innovative solution: micro-structured ceramic beads (MSCBs, approximately 3 mm in diameter) with a unique anisotropic pore structure. For the first time, we prepared MSCBs impregnated with cobalt oxide (Co/MSCBs) using a phase-inversion and sintering-assisted process. The Co/MSCBs were investigated for the degradation of sulfamethoxazole (SMX) in the peroxymonosulfate (PMS) induced AOPs system under mild reaction conditions. The effects of operating parameters (e.g., SMX concentration, reaction temperature, and catalyst dosage) in the Co/MSCBs|PMS system were studied on three different types of catalytic ceramic beads: 2Co/MSCB0 (beads with a common isotropic pore structure), 2Co/MSCB1 (beads with radial finger-like microstructures and a denser outer skin-layer), and 2Co/MSCB2 (beads with finger-like microstructures and no outer skin layer). At 20 °C, 2Co/MSCB2 (59.1 %) demonstrated a higher degradation efficiency for 40 mg/L SMX in comparison to 2Co/MSCB1 (54.9 %) and 2Co/MSCB0 (49.6 %). Additionally, it is noteworthy that the sample 2Co/MSCB2, after being used and regenerated, exhibited significantly a higher catalytic performance (70.83 % removal in 20 min during the 16th run) than the fresh one (70.47 % removal in 120 min). After reactions, Co/MSCBs can be readily separated from the bulk solution and used for the next run, making them ideal for practical applications. Furthermore, a radical quenching experiment was conducted, and a plausible catalytic mechanism was proposed. This research presents a new approach for the fabrication of micro-structured ceramic beads that are capable of effectively overcoming the diffusion limitations encountered in both heterogeneous reactions and adsorption processes.

The catalytic activity of metal–organic frameworks (MOFs) and post-synthetic modified MOF towards depolymerisation of polycarbonate

Chemical recycling of polycarbonate (PC) recovers valuable chemicals like monomers but often requires catalysts for mild reaction conditions and high conversion rates. This study explores the use of metal–organic frameworks (MOFs) as catalysts for PC methanolysis. We investigated the catalytic activity of amine-containing MOFs, specifically ZIF-8, MAF-6, and UiO-66-NH2, which have basic active sites favouring PC depolymerisation. MOFs were characterised using X-ray diffraction (XRD), Fourier-transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), and Brunauer–Emmett–Teller (BET) analysis. We examined the effects of temperature, catalyst content, and time on PC recycling efficiency and also conducted post-synthetic modification (PSM) of MOF-5 to assess its catalytic performance in PC depolymerisation. Methanolysis yielded bisphenol A (BPA) and dimethyl carbonate (DMC), with conversion rates confirmed by nuclear magnetic resonance (NMR). MOF catalysts significantly enhanced conversion rates compared to reactions without catalysts, with ZIF-8 and MAF-6 achieving nearly 100% PC conversion. PSM of MOF-5 with ethylenediamine (ED) led to increased PC conversion. Additionally, the MOF-based catalysts were recovered and reused for up to three cycles.

Electrochemical Nickel-Catalyzed Cross-Electrophile Coupling of Alkenyl Triflates with α-Chloroamides.

Cross-electrophile coupling reactions of different electrophiles have been extensively studied but mainly limited to bromides and iodides. Here, we report an electrochemically induced nickel-catalyzed cross-electrophile coupling strategy between alkenyl triflates and α-chloroamides in an undivided cell under mild reaction conditions, affording the α-functionalized amide derivatives in good to excellent yields with broad substrate scopes and good functional group tolerance. The control experiments were conducted, and a plausible mechanism was proposed.

3-Thioxo-3H-indolizinium-1-olates and Related Pseudo-Cross-Conjugated Heterocyclic Mesomeric Betaines: Synthesis and Spectral Features.

The first example of the synthesis of 3-thioxo-3H-indolizinium-1-olates, which further expands a limited class of pseudocross-conjugated heterocyclic mesomeric betaines isoconjugate to odd nonalternant hydrocarbon anion, is reported. These unique, moderately colored heterocyclic products result from a developed three-component reaction of cyclopropenones, pyridines, and sulfur. The protocol is distinguished by simple and mild reaction conditions that avoid expensive reagents or exotic catalysts, exhibiting high functional group tolerance. The broad scope of the reaction is particularly remarkable in light of the dramatic influence of pyridines' substituents on the reactivity of corresponding indolizin-1-ols, the key intermediates that proved to be highly thiophilic. In addition, an oxidative coupling of indolizin-1-ol in situ with p-tropoquinone oxime acetate is discovered. The reaction involves the C3 and C5 positions of the indolizin-1-ol and results in unusual indolizine-aminotropolone combinations. For the 3H-indolizinium-1-olate type of PCC HMBs, some general considerations concerning light absorption and NMR regularities were formulated.

Binary and Halide-free Catalyst Systems Based on Al/Ga/In Aminopyridylbisphenolate Complexes for the Cycloaddition of Epoxides and CO2.

Group 13 complexes bearing an aminopyridylbisphenol ligand have been prepared [ML-X; L = ligand, M = Al (X = Cl and Br), Ga (X = Cl, Br, and I), or In (X = Cl)]. The structures of the complexes containing the chloride ligand (ML-Cl; M = Al, Ga, and In) have been directly compared through an X-ray crystallography study, with differences in the monomeric or dimeric nature of their structures observed. All of the complexes obtained have been studied as potential catalysts for the synthesis of cyclic carbonates from epoxides and CO2. It has been found that the indium complex, as part of a traditional binary catalyst system (catalyst + tetra-butylammonium halide cocatalyst), displays the highest catalytic activity and is active under rather mild reaction conditions (balloon pressure of CO2). Meanwhile, it has been found that the GaL-I complex is a competent single-component catalyst (no need for addition of a cocatalyst) at more elevated reaction temperatures and pressures. A full substrate scope has been performed with both developed catalyst systems to demonstrate their applicability. In addition to the experimental results, a density functional theory study was performed on both catalyst systems. These results explain both why the indium catalyst is the most active under binary catalyst system conditions and how the gallium catalyst with an iodide (GaL-I) is able to act as a single-component catalyst in contrast to the indium-based complex.

Photoinduced Metal-Free Radical Addition/Cyclization of 2-Cyanoaryl Acrylamides to Prepare gem-Difluorinated Naphthyridinone Scaffolds.

Direct construction of gem-difluorinated heterocycles represents a long-standing challenge in organic chemistry. Herein, we developed a transition-metal-free photocatalytic radical addition/cyclization of BrCF2COR with 2-cyanoaryl acrylamides to give gem-difluorinated naphthyridinone scaffolds in moderate to good yields. Furthermore, some natural products were found to be suitable in the reaction system. The easily available substrates, mild reaction conditions, simple operation, and wide functionality tolerance show practical and environmental advantages in this method.

EDA Complex-Enabled Annulation to Access CF2-Containing Tetralones and Quinazolinones Using Persulfates as Electron Donors.

A photocatalyst-free and EDA complex-enabled radical cascade cyclization reaction of inactive alkenes with bromodifluoroacetamides was reported for the divergent synthesis of fluorine-containing tetralones and quinazolinones. In this transformation, persulfates as electron donors and difluoro bromamide as electron acceptors generate the EDA complex. This is a promising photochemical method with advantages such as mild reaction conditions, simple operation, being metal-free, and excellent functional group tolerance.

Synthesis of Fully Substituted Difluoromethylpyrazoles by Cyclization of Difluoroacetohydrazonoyl Bromides with 2-Acylacetonitriles or Malononitrile.

A concise and efficient method for the construction of fully substituted difluoromethylpyrazoles is achieved by a cyclization reaction between difluoroacetohydrazonoyl bromides and 2-acylacetonitrile or malononitrile. The method features advantages such as mild reaction conditions, broad substrate scope, good product yields, and high regioselectivity.

Biocatalytic Synthesis of Nitrile-Bearing All-Carbon Quaternary Stereocenters.

The synthesis of all-carbon quaternary stereocenters containing nitriles is a very important and challenging subject in organic chemistry. We used a biocatalytic approach under mild conditions to obtain new derivatives of these scaffolds by oxidation of catechols by Myceliophthora thermophila laccase (Novozym 51003) to afford o-quinones and 1,4-addition of a series of carbon nucleophiles containing tertiary alkyle nitriles to these intermediates. Using this approach, α-cyano carbonyls bearing a quaternary stereocenter were also prepared. Finally, the yields for the prepared compounds were 72-94%.

Strongly active and environmentally friendly WO3/C3N4 photocatalysts for converting cyclohexane to cyclohexanone under ambient conditions

C–H bond activation under mild conditions remains a great challenge in the chemical industry, while catalytic cyclohexane oxidation is inefficient and often requires organic solvents and strong oxidants. This study constructed a C3N4/WO3 Z-type heterojunction catalyst to efficiently convert cyclohexane into cyclohexanone and cyclohexanol (KA oil) through aqueous phase oxidation by O2 under visible light irradiation. With strong redox performance and high photogenerated carrier separation ability, the proposed composite catalyst can produce the key active species for cyclohexane oxidation in the H2O–O2 system. The reaction mechanism was clarified through experiment and DFT theory calculation. Cyclohexane was converted into cyclohexyl radical under the action of ·OH, and ·O2− converted most products into cyclohexanone. The catalyst can be recycled under optimized process conditions while reaching a KA oil yield of 139.73 μmol g−1 h−1 and a selectivity of 93.1%.

Rapid room-temperature synthesis of biocompatible metal–organic framework for enzyme immobilization with improved stability and on-demand release

Enzyme immobilization within metal–organic frameworks (MOFs) addresses the inherent fragility of enzymes, playing a crucial role across diverse industries by improving efficiency and lowering economic costs. While the application of MOFs in the food and pharmaceutical industries is constrained by toxicity concerns, MIL-88A(Fe) emerges as an ideal candidate due to its non-toxicity and biocompatibility. However, the release of encapsulated enzymes is significantly hampered, reducing their bioactivity. Herein, we present a safe and simple platform for creating enzyme@MIL-88A, which provides enzyme stabilization and controlled release. The thermal stabilization of a spectrum of enzymes (phytase, xylanase, amylase, mannanase, and glucanase) is achieved, elevating their endurance threshold to 95 °C. Furthermore, the controlled on-demand release of the encapsulated enzymes at target sites is accomplished by adjusting defects in enzyme@MIL-88A composites via an acid modulation approach, while preserving enzyme activity. This approach has improved the amount of enzyme released from 10 % to 99.7 %. To the best of our knowledge, this is the first time enzyme@MIL-88A has been synthesized rapidly under mild conditions for enzyme stabilization and controlled release. Our method offers a universal platform for stabilizing vulnerable biomaterials and the controlled delivery of biological macromolecules.