Reaction Conditions Research Articles

A new nickel-based δ-isomer Anderson-type polyoxometalates: Synthesis, crystal structure and catalytic activity in 1,2,3-triazoles production

In this study, we present a novel organic hybrid Ni-based δ-isomer of Anderson-type polyoxometalates (POMs), namely, δ-[C6H12Mo6N2NiO24]4− (1), as an efficient catalyst for the cycloaddition reaction between alkynes, halides, and sodium azide. Synthesis of the catalyst was performed using a facile one-pot method followed by characterization using single crystal, powder XRD, SEM, and FT-IR techniques. After optimizing reaction conditions for a model reaction (T = 80 °C, time = 6 h, and solvent = 2 mL H2O), the catalytic activity of this compound was examined for the preparation of diversely substituted 1,2,3-triazoles under ambient atmospheric and additive-free conditions, achieving moderate to good yields. Catalyst 1 could reuse up to four sequential cycles without significant loss in its catalytic activity. Additionally, the true heterogeneity of the catalyst was determined by the hot-filtration test.

Synthesis and Characterization of Lignin-Silver Nanoparticles

Metal nanoparticle synthesis via environmentally friendly methods is gaining interest for their potential advantages over conventional physico-chemical approaches. Herein, we propose a robust green synthesis route for lignin-modified silver nanoparticles, utilizing the recovery of lignin as a renewable raw material and exploring its application in valuable areas. Through a systematic approach combining UV-Vis spectroscopy with AAS and DLS, we identified repeatable and scalable reaction conditions in an aqueous solution at pH 11 for homogeneous silver nanoparticles with high uniformity. The TEM median sizes ranged from 12 to 15 nm with circularity between 0.985 and 0.993. The silver nanoparticles yield exceeded 0.010 mol L−1, comparable with traditional physico-chemical methods, with a minimal loss of silver precursor ranging between 0.5 and 3.9%. Characterization by XRD and XPS revealed the presence of Ag-O bonding involving lignin functional groups on the pure face-centered cubic structure of metallic silver. Moreover, the lignin-modified silver nanoparticles generated a localized thermal effect upon near-infrared laser irradiation (808 nm), potentially allowing for targeted applications in the biomedical field. Our study showcases the potential of lignin as a renewable reducing and capping agent for silver nanoparticle synthesis, addressing some shortcomings of green synthesis approaches and contributing to the development of suitable nanomaterials.

Design and one-pot synthesis of new substituted pyrrolo[1,2-a]thieno[3,2-e]pyrimidine as potential antitumor agents: in vitro and in vivo studies

A new efficient and versatile one-pot three-component synthesis of substituted pyrrolo[1,2-a]thieno[3,2-e]pyrimidine derivatives has been developed. It is based on a multistep cascade reaction from 2-aminothiophenes and 2-hydroxy-4-oxobut-2-enoic acids, and derivatives of cyanoacetic acid catalyzed by diisopropylethylamine. As a result, novel pyrrolo[1,2-a]thieno[3,2-e]pyrimidine derivatives (21 compounds) were synthesized in a mild reaction conditions with a high yield. The structures of the developed compounds were confirmed by NMR and elemental analysis. The influence of electron-withdrawing or electron-donor substituents on the antitumor activity of the developed compounds has been identified. In vitro screening analysis of 21 compounds revealed six lead candidates (12aa, 12dc, 12hc, 12ic, 12lb, and 12mb) that demonstrated the most significant antitumor activity against B16-F10, 4T1 and CT26 cells. Necrosis/apoptosis assay showed that apoptosis was the predominant mechanism of cell death. Molecular docking analysis revealed several potential targets for tested compounds, i.e. phosphatidylinositol 5-phosphate 4-kinase (PI5P4K2C), proto-oncogene serine/threonine-protein kinase (Pim-1), nicotinamide phosphoribosyltransferase (NAMPT) and dihydrofolate reductase (DHFR). The lead compound (12aa) can effectively induce cell apoptosis, possesses a high yield (98 %) and requires low-cost starting chemicals for its synthesis. In vivo experiments with melanoma-bearing mice confirmed that 12aa compound resulted in the significant tumor inhibition on 15 d after the therapy. In particular, tumor volume was ∼0.19 cm3 for 50 mg/kg versus ∼2.39 cm3 in case of untreated mice and tumor weight was ∼71.6 mg for 50 mg/kg versus ∼452.4 mg when considered untreated mice. Thus, our results demonstrated the high potential of the 12aa compound in the treatment of melanoma and can be recommended for further preclinical studies.

Mesoporous SBA‐15 Supported CdS through Organosilane Ligand for Photo Driven Cleavage of Aryl Ether in Lignin and its Model Compound

AbstractMesoporous silica (SBA‐15) was synthesized hydrothermally followed by calcination and then functionalization with 3‐(triethoxysilyl)‐1‐propanethiol through surface grafting. The thiol moiety of the grafted ligand was utilized for the uniform anchoring of cadmium into the channels of the material. The synthesised material was subjected for its photo catalytic applications after characterization through standard characterization protocol. The synthesised mesoporous silica (i.e. SAB‐15), ligand modified material (i.e.SBA‐15‐S and Cd loaded ( i.e. SAB‐15‐CdS) materials were characterized through standard characterization protocol like powder XRD, FT‐IR, UV‐DRS, MAS NMR, N2 sorption, FE‐SEM, HR‐TEM and TG‐DTA studies. After successful characterization, the screening of the catalyst was carried out on a model reaction involving photo catalytic cleavage of α‐O‐4 aryl ether linkage present in benzyl phenyl ether, which is an important lignin model compound. The catalyst exhibited good efficiency along with the selectivity for desired monoaromatic platform chemicals. The synthesized catalyst was also carried out for the photo catalytic depolymerization of alkali lignin at the optimized reaction conditions which further showed the promising results for getting value added chemicals from lignin. The reaction products were characterized by using Gas chromatography‐mass spectrometry (GC‐MS) techniques.

Synthesis and characterization of β-cyclodextrin polymers and its performance as a drug carrier

The aim of this study was to determine the optimal reaction conditions for the synthesis of hyperbranched cyclodextrin polymer (CDP) and to investigate their performance as drug carriers. In this study, β-Cyclodextrin (β-CD) was used as the basis for CDP nanocarriers, which were synthesized by reacting β-CD with pyromellitic dianhydride (PMDA) as a crosslinking agent. The effects of β-CD/PMDA molar ratio and reaction time were investigated to optimize the synthesis of CDP. The optimal reaction conditions were determined to be a reaction time of 2 h and a molar ratio of 1/12 β-CD/PMDA. Ketoprofen (KP) was used as a model drug to evaluate the loading capacity of CDP. The effects of KP/CDP (w/w) loading ratio, temperature, and stirring speed on the formation of the KP/CDP inclusion complex were investigated. The optimum conditions for loading KP into CDP were found to be 1/4 KP/CDP ratio, 4 h, 35 °C, and 300 rpm with a loading efficiency of 39.57%. Characterization of the CDP was performed using Zetasizer, FTIR, DSC, SEM and XRD analysis.

A Real-Time LSPR-Based Study of Metal-Organic Framework (MOF) Growth.

MOFs are known for their absorption properties and widely used for accumulation, filtering, sensorics, photothermal, catalytical and other applications. Their combination with plasmonic metal nanoparticles leads to hybrid structures that profit from the stabilizing effect and high porosity of the MOF as well as the optical and electronic properties of the nanoparticles. The growth of MOFs on plasmonic nanoparticles can be monitored in-situ using LSPR spectroscopy, simultaneously applying microfluidic reaction conditions for the fabrication of NP@MOF structures. Here, a systematic study is conducted using LSPR spectroscopy for the monitoring of the Layer-by-Layer deposition of twelve different MOFs, determining the suitability of LSPR spectroscopy for this purpose. In addition to some well-investigated materials like HKUST-1, other MOFs such as MIL-53, MIL-88 A and Cu-BDC are deposited successfully. For some MOFs such as Zn-Fum, the LSPR experiment indicates that no deposition had taken place. The results are confirmed with AFM, SEM and XPS measurements. This work shows that LSPR spectroscopy is suitable for the in-situ monitoring of LbL MOF growth and the microfluidic setup is a very promising method for the controlled manufacturing of NP@MOF hybrid structures. Further studies may include the optimization of the synthesis process or the transfer to other materials.

Manganese‐Mediated Electrooxidative Ring‐Opening Azidation of Cyclobutanol Derivatives with TMSN3

AbstractA Mn‐electrocatalytic ring‐opening azidation of tert‐cyclobutanols has been developed. The regioselective method is applicable for the azidation of a diverse array of cyclobutanols to provide practical γ‐azido ketones in 23–91% yields under chemical oxidants‐free reaction conditions. Detailed mechanistic studies suggest the process of Mn‐mediated alkoxy radical generation followed by β‐scission to form carbon‐centered radical species is possibly involved in this transformation.

Inside Back Cover

The cover displays a selective oxidative sulfonylation of alkenes with selenium sulfonate depended on the reaction conditions. The electrochemical C—H sulfonylation proceeded smoothly to afford (E)‐vinyl sulfones with good selectivity in an undivided cell without external oxidant. While aerobic trifunctionalization of alkenes occurred in the presence of KI in the air, which provides β‐keto selenosulfones via the formation of C—O, C—S, and C—Se bonds in one‐pot. This selective synthesis is like interstellar racing, reaching distant planets from the same starting point through different paths. Following control experiments, a plausible mechanism is proposed to rationalize the experimental results. More details are discussed in the article by Cao et al. on page 1367—1372.image

Triflic Acid-Assisted Regioselective Bromination of Quinoxaline Derivatives Enables a Facile Synthesis of Polymer PTQ10.

Poly[(thiophene)-alt-(6,7-difluoro-2(2-hexyldecyloxy)quinoxaline)] (PTQ10) emerges as a promising candidate for donor materials in organic solar cells (OSCs) due to its high efficiency, simplified synthesis, and cost-effectiveness. The acceptor unit of PTQ10 is derived from the alkylation of 5,8-dibromo-6,7-difluoroquinoxaline-2-ol, emphasizing the importance of its economical synthesis for commercial viability. This study investigates triflic acid-assisted regioselective bromination of quinoxaline derivatives and proposes an alternative synthetic pathway for PTQ10. The developed route benefits from concise synthetic steps, a dependable procedure, and high overall yield. Starting with the condensation of 4,5-difluorobenzene-1,2-diamine with ethyl oxoacetate to yield 6,7-difluoroquinoxaline-2-ol, subsequent triflic acid-assisted regioselective bromination produces 5,8-dibromo-6,7-difluoroquinoxaline-2-ol in high yield. Alkylation under Mitsunobu reaction conditions yields 5,8-dibromo-6,7-difluoro-2-(2-hexyldecyloxy)quinoxaline, followed by polymerization with 2,5-distannylated thiophene under Stille reaction conditions to afford PTQ10. This research provides insights into efficient synthetic strategies for PTQ10, advancing its potential for commercial application in OSCs.

Epoxidation of Camelina sativa oil methyl esters as a second-generation biofuel with thermodynamic calculations

The epoxidation of methyl esters found in Camelina sativa (CS) non-edible oil — largely containing unsaturated fatty acids — was performed. Epoxides are known to be used in biopolymer formation and CO2 capture. This study distinctively demonstrates epoxidation process through a combination of statistical methods and quantum chemical thermodynamic calculations. Esters produced along with glycerol during transesterification of vegetable oils can be used efficiently through epoxidation. Epoxidation products synthesized at various reaction conditions (including oil refinement) were analyzed through gas chromatography with mass spectrometry. According to the statistical analysis, the reaction time and temperature had the highest effect on the composition of products and oil refining is unnecessary. Moreover, iodine values (ester conversion) were determined without the use of chemicals through Raman spectroscopy. The study findings indicate CS epoxidation to be an environment-friendly process.

Interface Effects in the Stability of 2D Silica, Silicide, and Silicene on Pt(111) and Rh(111).

Ultrathin two-dimensional silica films have been suggested as highly defined conductive models for fundamental studies on silica-supported catalyst particles. Key requirements in this context are closed silica films that isolate the gas phase from the underlying metal substrate and stability under reaction conditions. Here, we present silica bilayer films grown on Pt(111) and Rh(111) and characterize them by scanning tunneling microscopy and X-ray photoelectron spectroscopy. We provide the first report of silica bilayer films on Rh(111) and have further successfully prepared fully closed films on Pt(111). Interestingly, surface and interface silicide phases play a decisive role in both cases: On platinum, closed films can be stabilized only when silicon is deposited in excess, which results in an interfacial silicide or silicate layer. We show that these silica films can also be grown directly from a surface silicide phase. In the case of rhodium, the silica phase is less stable and can be reduced to a silicide in reductive environments. Though similar in appearance to the "silicene" phases that have been controversially discussed on Ag(111), we conclude that an interpretation of the phase as a surface silicide is more consistent with our data. Finally, we show that the silica film on platinum is stable in 0.8 mbar CO but unstable at elevated temperatures. We thus conclude that these systems are only suitable as model catalyst supports to a limited extent.

Retrosynthesis Zero: Self-Improving Global Synthesis Planning Using Reinforcement Learning.

The field of computer-aided synthesis planning (CASP) has witnessed significant growth in recent years. Still, many CASP programs rely on large data sets to train neural networks, resulting in limitations due to the data quality and prior knowledge from chemists. In response, we propose Retrosynthesis Zero (ReSynZ), a reaction template-based method that combines Monte Carlo Tree Search with reinforcement learning inspired by AlphaGo Zero. Unlike other single-step reaction template-based CASP methods, ReSynZ takes complete synthesis paths for complex molecules, determined by reaction rules, as input for training the neural network. ReSynZ enables neural networks trained with relatively small reaction data sets (tens of thousands of data) to generate multiple synthesis pathways for a target molecule and suggest possible reaction conditions. On multiple data sets of molecular retrosynthesis, ReSynZ demonstrates excellent predictive performance compared to existing algorithms. The advantages, such as self-improving model features, flexible reward settings, the potential to surpass human limitations in chemical synthesis route planning, and others, make ReSynZ a valuable tool in chemical synthesis design.

Anionic Conjugate Addition Oligomerization of Carbon Dioxide/Butadiene Derived Lactones.

Nucleophilic and non-nucleophilic bases have been employed in anionic oligomerization of unsaturated δ-valerolactone (3-ethylidene-6-vinyltetrahydro-2H-pyran-2-one) (1). Compared to the seminal findings with 1,5,7-triazabicyclo[4.4.0]dec-5-ene (TBD), the unsaturated lactone reacts with guanidines, disilazanes, and phosphazenes both in bulk and in solution with higher productivities and activities, reaching full conversion with turnover frequencies up to 382 h-1. Additionally, reactions using phosphazenes and NaHMDS were active at 1 mol % catalyst loadings both in solvent and in bulk monomer at room temperature. Characterization of the reaction products by 1H, 13C, FTIR, MALDI-MS, tandem mass spectrometry (MS/MS), and ion mobility mass spectrometry (IM-MS) revealed microstructural differences dependent on the nucleophilicity of the organocatalytic base and reaction conditions. The products from phosphazene-catalyzed reactions are consistent with selective vinylogous 1,4-conjugate addition, whereas both conjugate addition and ring-opening mechanisms are observed in TBD. DSC reveals that these microstructures can be tuned to have a Tg range between -18 and 80 °C, while SEC and MALDI-MS reveal that only low molar mass oligomers are formed (748-5949 g/mol). From these results, an approach for selectively favoring the vinylogous 1,4-conjugate addition pathway is obtained over ring-opening reactivity.

Copper-Catalyzed [4+1+1] Annulation of Ammonium Salts and Anthranils: Synthesis of 2,3-Diaroylquinolines.

A copper(I)-catalyzed protocol is developed for the synthesis of various 2,3-diaroylquinolines starting from achiral ammonium salts and anthranils through [4+1+1] annulation. Using copper(I) chloride as the sole catalyst, this reaction is featured with easily available starting materials, broad substrate scope, good yields and simple reaction conditions.

Sonochemical Synthesis of Copper Borates: Effect of Reaction Conditions on the Characteristic Properties

The effect of ultrasonic treatment on liquid-state production and the characteristic features of synthesized powder were studied in liquid-state conditions. In sonochemical synthesis, the operation parameters of mole ratio, reaction temperature, and time were optimized. The synthesis was achieved in moderate conditions such as mole ratio of copper: sodium: boron (Cu: Na: B) 1:2:1, 70°C and 2.5 minutes. The prepared samples were identified as copper borate (Cu(BO2)2) with the powder diffraction file number "00-001-0472". The reaction yields were also increased from 50% to 71.5% with the modification of the experimental procedure. The specific FT-IR peaks were observed at 1090, 985, 872, 781 and 731 cm-1 band values. In the morphological analyses, the agglomerations of multi-angular particles were seen. The results showed the affirmative effects of the possible use of the ultrasonic treatment on both the practical synthesis and the increase of characteristics.

A Mechanistic Investigation of the N-Hydroxyphthalimide Catalyzed Benzylic Oxidation Mediated by Sodium Chlorite.

A detailed investigation into the mechanistic course of N-hydroxyphthalimide catalyzed oxidation of benzylic centers using sodium chlorite as the stoichiometric oxidant is reported. Through a combination of experimental, spectroscopic, and computational techniques, the transformation is interrogated, providing improved reaction conditions and an enhanced understanding of the mechanism. Performing the transformation in the presence of acetic acid or a pH 4.5 buffer leads to extended reaction times but improves the catalyst lifetime, leading to the complete consumption of the starting material. Chlorine dioxide is identified as the active oxidant that is able to oxidize the N-hydroxyphthalimide anion to the phthalimide-N-oxyl radical, the proposed catalytically active species, which is able to abstract a hydrogen atom from the substrate. A second molecule of chlorine dioxide reacts with the resultant radical and, after loss of hypochlorous acid, leads to the observed product. Through a broad variety of techniques including UV/vis, EPR and Raman spectroscopy, isotopic labeling, and the use of radical traps, evidence for the mechanism is presented that is supported through electronic structural calculations.

A new Ag‐based photocatalyst for efficient degradation of antibiotic nitrofurantoin

In this paper, a new 0D Ag(I)‐based coordination polymer [Ag2(dib)(H2L)2](1) is proposed as a photocatalyst for the photocatalytic degradation of nitrofurantoin (NFT) under ultraviolet irradiation. The catalytic 1 was analyzed by various methods such as PXRD, SEM, FT‐IR, TGA, UV–vis, DRS, and electrochemical tests. The experimental result shows that 1 is an n‐type semiconductor, which can effectively catalyze the photodegradation of NFT under ultraviolet irradiation. Under the optimal reaction conditions, the photodegradation rate of NFT was 97.95% within 60 min when the concentration of NFT was 30 ppm. The experiment of free radical capture shows that O2˙− is the main active substance for photodecomposition, and the possible mechanism of 1 catalytic degradation of NFT is proposed. This research will lay the foundation for Ag(I)‐based coordination polymers in the field of antibiotic photocatalytic degradation.

Ferromagnetically Coupled Chromium(III) Dimer Shows Luminescence and Sensitizes Photon Upconversion.

There has been much progress on mononuclear chromium(III) complexes featuring luminescence and photoredox activity, but dinuclear chromium(III) complexes have remained underexplored in these contexts until now. We identified a tridentate chelate ligand able to accommodate both meridional and facial coordination of chromium(III), to either access a mono- or a dinuclear chromium(III) complex depending on reaction conditions. This chelate ligand causes tetragonally distorted primary coordination spheres around chromium(III) in both complexes, entailing comparatively short excited-state lifetimes in the range of 400 to 800 ns in solution at room temperature and making photoluminescence essentially oxygen insensitive. The two chromium(III) ions in the dimer experience ferromagnetic exchange interactions that result in a high spin (S=3) ground state with a coupling constant of +9.3 cm-1. Photoinduced energy transfer from the luminescent ferromagnetically coupled dimer to an anthracene derivative results in sensitized triplet-triplet annihilation upconversion. Based on these proof-of-principle studies, dinuclear chromium(III) complexes seem attractive for the development of fundamentally new types of photophysics and photochemistry enabled by magnetic exchange interactions.

Photo-Induced Ruthenium-Catalyzed C-H Arylation Polymerization at Ambient Temperature.

Transition metal-catalyzed C-H arylation polymerization (CHAP) is an attractive tool for constructing π-conjugated polymers in a sustainable manner. However, the existing methods primarily rely on palladium catalysis, which usually entails harsh reaction conditions and branching/cross-linking. Here we report the first example of an ambient-temperature ruthenium-catalyzed C-H arylation polymerization induced by visible light irradiation. The present polymerization can produce various meta- and para-linked polymers in excellent yields with high molecular weights. The remarkable feature of our mild reaction platform is represented by high chemoselectivity, leading to polymers that are otherwise inaccessible under conventional reaction conditions at high temperatures.

Machine-Learning-Assisted Descriptors Identification for Indoor Formaldehyde Oxidation Catalysts.

The development of highly efficient catalysts for formaldehyde (HCHO) oxidation is of significant interest for the improvement of indoor air quality. Up to 400 works relating to the catalytic oxidation of HCHO have been published to date; however, their analysis for collective inference through conventional literature search is still a challenging task. A machine learning (ML) framework was presented to predict catalyst performance from experimental descriptors based on an HCHO oxidation catalysts database. MnOx, CeO2, Co3O4, TiO2, FeOx, ZrO2, Al2O3, SiO2, and carbon-based catalysts with different promoters were compiled from the literature. Notably, 20 descriptors including reaction catalyst composition, reaction conditions, and catalyst physical properties were collected for data mining (2263 data points). Furthermore, the eXtreme Gradient Boosting algorithm was employed, which successfully predicted the conversion efficiency of HCHO with an R-square value of 0.81. Shapley additive analysis suggested Pt/MnO2 and Ag/Ce-Co3O4 exhibited excellent catalytic performance of HCHO oxidation based on the analysis of the entire database. Validated by experimental tests and theoretical simulations, the key descriptor identified by ML, i.e., the first promoter, was further described as metal-support interactions. This study highlights ML as a useful tool for database establishment and the catalyst rational design strategy based on the importance of analysis between experimental descriptors and the performance of complex catalytic systems.