Palladium‐Catalyzed Oxidative Alkynylation of Allenyl Ketones: Access to 3‐Alkynyl Poly‐substituted Furans

Posted on 26 September 2023 by nBowen Dou, nKang Wang, nJianbo Wangn

We report herein a palladium-catalyzed cyclizative alkynylation of allenyl ketones with terminal alkynes, which is proposed to follow a mechanism involving palladium-carbene migratory insertion.

Comprehensive Summary

Furans bearing alkynyl substituents are highly useful in organic synthesis. However, the methodologies to access these important furan derivatives are rather limited. We herein report an efficient synthesis of alkynylated furan derivatives based on Pd-catalyzed oxidative cross-coupling reaction between allenyl ketones and terminal alkynes. This novel synthesis of alkynylated furans with wide substrate scope is operationally simple and tolerates various functional groups. Mechanistically, the formation of the palladium carbene through cycloisomerization and the subsequent alkynyl migratory insertion are proposed as the key steps in the transformation. The reaction reported in this paper further demonstrates the generality of the carbene-based cross coupling.

Formal Deoxygenative Cross‐Coupling of Aldehydes to Ketones through α‐Haloboronates: A Route to Deoxygenative Hydroacylation of Aldehydes

Posted on 26 September 2023 by nZihao Hu, nWanqi Zhang, nXU Taon

A cross-coupling of aldehydes with α-haloboronates has been achieved under dual nickel/photoredox catalysis system. Considering the easy preparation of α-haloboronates with our deoxygenative difunctionalization of carbonyls (DODC) strategy, this protocol provides a formal deoxygenative cross-coupling of aldehydes to one-carbon-prolonged ketone products. The mild conditions enabled good functional group tolerance and broad substrate applicability. The application of this method was presented via a tunable synthesis of two ketones with very similar skeletons from two same aldehydes.

Comprehensive Summary

Aldehydes are a kind of important synthons and reagents in organic synthesis. The efforts on transformations of aldehydes are highly rewarding and have always attracted considerable attention. Herein, a cross-coupling of aldehydes with α-haloboronates has been achieved under dual nickel/photoredox catalysis system. Considering the α-haloboronates can be easily obtained from aldehydes with our deoxygenative difunctionalization of carbonyls (DODC) strategy, this protocol provides a formal deoxygenative cross-coupling of aldehydes to one-carbon-prolonged ketone products. The mild conditions enabled good functional group tolerance and broad substrate applicability. The application of this method was presented via a tunable synthesis of two ketones with very similar skeletons from two same aldehydes.

Characterization of Sprays Generated by the Expansion of Emulsions with Liquid Carbon Dioxide

Posted on 26 September 2023 by nClara Lauscher, nAlexander Licau, nGerhard Schaldach, nMarkus Thommesn

An approach to generate aerosols by expanding emulsions with water and liquid carbon dioxide was investigated regarding the local droplet size, the droplet velocity, and the mass concentration in the spray cone. The high-pressure emulsion was expanded not only through an orifice but also through swirl nozzles, and the differences in the droplet formation process were determined.

Abstract

Expanding emulsions with liquid CO₂ facilitates the creation of aerosols with an average droplet diameter in the low micrometer size range, which is challenging with conventional atomizers. The droplet formation process of the expansion of high-pressure emulsions was investigated using a plain-orifice atomizer and different swirl nozzles. The local droplet size and droplet velocities were measured and used to estimate the local Weber number and thus infer the droplet size reduction. Measurements of the local mass concentration in the aerosol showed that, for the swirl nozzle, the highest concentration was found outside of the central axis, indicating radial momentum generated by the swirl nozzle. Furthermore, it was shown that the type of expansion nozzle used has an influence on the resulting median droplet size in the aerosol. For a water mass load of 0.01, the median droplet diameter was reduced from 8 to 3 μm by increasing the swirl number from 0.01 to 0.1.

Partial Hydrolysis of Diphosphonate Ester During the Formation of Hybrid TiO2 Nanoparticles: Role of Acid Concentration

Posted on 26 September 2023 by

The extent of partial hydrolysis of tetraethyl propylene diphosphonate ester (TEPD) is altered by controlling the acid content during the formation of hybrid organic-inorganic TiO₂ nanoparticles. Depending on the degree of partial hydrolysis, the TEPD (derivatives)-TiO₂ bonding in the obtained materials is altered, as evidenced by solution and solid-state NMR.

Abstract

The hydrolysis of the phosphonate ester linker during the synthesis of hybrid (organic-inorganic) TiO₂ nanoparticles is important when forming porous hybrid organic-inorganic metal phosphonates. In the present work, a method was utilized to control the in-situ partial hydrolysis of diphosphonate ester in the presence of a titania precursor as a function of acid content, and its impact on the hybrid nanoparticles was assessed. Organodiphosphonate esters, and more specific, their hydrolysis degree during the formation of hybrid organic-inorganic metal oxide nanoparticles, are relatively under explored as linkers. Here, a detailed analysis on the hydrolysis of tetraethyl propylene diphosphonate ester (TEPD) as diphosphonate linker to produce hybrid TiO₂ nanoparticles is discussed as a function of acid content. Quantitative solution NMR spectroscopy revealed that during the synthesis of TiO₂ nanoparticles, an increase in acid concentration introduces a higher degree of partial hydrolysis of the TEPD linker into diverse acid/ester derivatives of TEPD. Increasing the HCl/Ti ratio from 1 to 3, resulted in an increase in degree of partial hydrolysis of the TEPD linker in solution from 4 % to 18.8 % under the applied conditions. As a result of the difference in partial hydrolysis, the linker-TiO₂ bonding was altered. Upon subsequent drying of the colloidal TiO₂ solution, different textures, at nanoscale and macroscopic scale, were obtained dependent on the HCl/Ti ratio and thus the degree of hydrolysis of TEPD. Understanding such linker-TiO₂ nanoparticle surface dynamics is crucial for making hybrid organic-inorganic materials (i. e. (porous) metal phosphonates) employed in applications such as electronic/photonic devices, separation technology and heterogeneous catalysis.

NiO/ZnO Composite Derived Metal‐Organic Framework as Advanced Electrode Materials for Zinc Hybrid Redox Flow Battery

Posted on 26 September 2023 by

NiO/ZnO-derived MOF composite is used to modify carbon felt electrode. Alkaline zinc-based electrolyte is used as anolyte and catholyte and exhibits better redox reactions. The peak current ratio increases to 1.07 mA at 10 mA cm⁻² for the as-prepared material.

Abstract

NiO/ZnO composite derived metal-organic framework (MOF) is used as to modify carbon felt (CF) via a conventional solid-state reaction followed by ultrasonication. The prepared electrode material is used in zinc-hybrid redox flow batteries (RFBs) due to their high redox activity of Zn²⁺/Zn. The electrochemical performance of composite modified CF and pre-treated CF was studied by cyclic voltammetry (CV) in 0.5 M aqueous zinc chloride with 5 M potassium hydroxide solutions showed clear confirmation for enhanced electrocatalytic activity. The unique porous structure of NiO/ZnO-derived MOF with increased surface area improves the battery behavior significantlyThe peak current ratio for the as-prepared material is about 3 times higher than that of the pre-treated CF due to more active sites. Zinc-based RFB with modified CF electrode exhibited better electrochemical performance with voltage efficiency (VE, 88 %), which is higher than true redox flow batteries.

Perspectives on Dual‐purpose Functional Nanomaterials for Detecting and Removing Fluoride Ion from Environmental Water

Posted on 26 September 2023 by nSukhvinder Dhiman, nArun Kumar Solanki, nKritika Nag, nGovindasamy Jayamurugann

Two-in-one: This review discusses recent developments in the area of functional nanomaterials that are capable of detecting and removing fluoride through the use of agglomeration, electrostatic, H-bonding, ion exchange, coordination and π-π stacking interactions. This unique approach provides an effective way to detect and remove fluoride from water in the environment.

Abstract

Fluoride (F⁻) is a unique analyte because when in small quantities, it is beneficial and harmful when in larger or negligible quantities, leaving it essential for dual-purpose detection and removal from a water sample to prevent fluoride-caused health risks. F⁻ detection and removal using organic molecules and hybrid materials are extensively reported in the literature, but very few reports discuss dual-purpose detection and removal. Functional nanomaterials (FNM) based on nanoparticles, metal-organic frameworks, and carbon dots conjugated with fluorophore moiety are largely used for these purposes. Functional groups on nanomaterial surfaces exhibited various interactions such as agglomeration, electrostatic, hydrogen bonding, ion exchange, coordination and π-π stacking interactions, enabling dual-purpose detection and removal of F⁻. These materials offer unique properties such as tunable pore structure, size, and morphology coupled with large surface area and high thermal/chemical stability. Further, this perspective review discusses prospects for sustainable technologies and describes the advantages and disadvantages of using FNM based on its optical properties for detection and removal efficiency. We believe this is the first account that summarizes the single FNM that can be used for simultaneously the selective detection of F⁻ in aqueous media and its efficient removal.

Influence of Coordination to Silver(I) Centers on the Activity of Heterocyclic Iodonium Salts Serving as Halogen‐Bond‐Donating Catalysts

Posted on 26 September 2023 by

Pyrazole-containing iodonium triflates and silver(I) triflate bind to each other, and such an interplay significantly affects the total catalytic activity of the mixture of these Lewis acids. The obtained results indicate that such a cooperation additionally results in prevention of decomposition of the organocatalysts during the reaction progress.

Abstract

Kinetic data based on ¹H NMR monitoring and computational studies indicate that in solution, pyrazole-containing iodonium triflates and silver(I) triflate bind to each other, and such an interplay results in the decrease of the total catalytic activity of the mixture of these Lewis acids compared to the separate catalysis of the Schiff condensation, the imine–isocyanide coupling, or the nucleophilic attack on a triple carbon−carbon bond. Moreover, the kinetic data indicate that such a cooperation with the silver(I) triflate results in prevention of decomposition of the iodonium salts during the reaction progress. XRD study confirms that the pyrazole-containing iodonium triflate coordinates to the silver(I) center via the pyrazole N atom to produce a rare example of a pentacoordinated trigonal bipyramidal dinuclear silver(I) complex featuring cationic ligands.

Electrostatic Self Assembly of Metal‐Free Hexagonal Boron Nitride/Protonated Carbon Nitride (h‐BN/PCN) Nanohybrid: A Synergistically Upgraded 2D/2D Sustainable Electrocatalyst for Sulfamethazine Identification

Posted on 26 September 2023 by

The present study illustrates the advantages of the synergistically upgraded, sustainable, metal-free h-BN/PCN electrocatalyst for sulfamethazine sensor towards real-world samples using highly sensitive electrochemical techniques with good recovery percentages. Thus, the best performance for the electrochemical sensing of SMZ was exhibited by the h-BN/PCN nanocomposite.

Abstract

In the scientific community, developing a non-enzymatic detection tool for highly reliable and sensitive identification of the targeted biomolecules is challenging. Sulfamethazine (SMZ), a bacterial inhibitor frequently used as an antibacterial medicine, can cause antimicrobial resistance (AMR) in humans if taken in excess. Hence, there is a need for a reliable and rapid sensor that can detect SMZ in food and aquatic environments. The goal of this study aims to develop a novel, inexpensive 2D/2D hexagonal boron nitride/protonated carbon nitride (h-BN/PCN) nanohybrid that can function as an electrocatalyst for SMZ sensing. The as-synthesized material‘s crystalline, structural, chemical, and self-assembly properties were thoroughly characterized by XRD, HR-TEM, XPS, HR-SEM, FT-IR, and ZETA potential and electrochemical sensing capacity of the suggested electrodes was optimized using CV, EIS, DPV, and i-t curve techniques. The above nanohybrid of h-BN/PCN-modified GCE exhibits improved non-enzymatic sulfamethazine sensing behaviour, with a response time of less than 1.83 s, a sensitivity of 1.80 μA μM⁻¹ cm⁻², a detection limit of 0.00298 μM, and a range of 10 nM to 200 μM. The electrochemical analysis proves that the conductivity of h-BN has significantly improved after assembling PCN due to the large surface area with active surface sites and the synergistic effect. Notably, our constructed sensor demonstrated outstanding selectivity over a range of probable interferents, and electrochemical studies indicate that the suggested sensor has improved functional durability, rapid response, impartial repeatability, and reproducibility. Furthermore, the feasibility of an h-BN/PCN-modified sensor to detect the presence of SMZ in food samples consumed by humans has been successfully tested with high recovery percentages.

Sterically Enhanced Control of Enzyme‐Assisted DNA Assembly

Posted on 26 September 2023 by

The sterically controlled, nuclease enhanced DNA assembly technique successfully assembles DNA structures containing multiple capture probes. Short (60 bp) DNA stands, with probes attached, are assembled with larger (1 kb) strands, overcoming the limitations of Gibson assembly, and offering a multiplex diagnostic tool.

Abstract

Traditional methods for the assembly of functionalised DNA structures, involving enzyme restriction and modification, present difficulties when working with small DNA fragments (<100 bp), in part due to a lack of control over enzymatic action during the DNA modification process. This limits the design flexibility and range of accessible DNA structures. Here, we show that these limitations can be overcome by introducing chemical modifications into the DNA that spatially restrict enzymatic activity. This approach, sterically controlled nuclease enhanced (SCoNE) DNA assembly, thereby circumvents the size limitations of conventional Gibson assembly (GA) and allows the preparation of well-defined, functionalised DNA structures with multiple probes for specific analytes, such as IL-6, procalcitonin (PCT), and a biotin reporter group. Notably, when using the same starting materials, conventional GA under typical conditions fails. We demonstrate successful analyte capture based on standard and modified sandwich ELISA and also show how the inclusion of biotin probes provides additional functionality for product isolation.

Linear Polymer Comprising Dual Functionalities with Hierarchical Pores for Lithium Ion Batteries

Posted on 26 September 2023 by

Polymers for batteries: A linear polymer with micro and Nano pores with azo and carbonyl functionalities renders increased accessibility to Li ions after preconditioning. During charge-discharge experiment Azo-Carb-PDI electrode had impressive discharge capacity of 469 mA h/g after 500 cycle which is almost 15 times higher than the monomer (Azo-PDI-Azo, 30 mA h/g after 100 cycle).

Abstract

Organic materials with carbonyl, azo, nitrile and imine moieties are widely used in lithium batteries. The solubility of these materials in battery electrolytes is an issue. Aggregation of the organic molecules can suppress the solubility, but the accessibility of lithium-ion is hindered. Therefore, insoluble porous organic materials are desired. Herein, we synthesized a linear polymer with carbonyl and azo functionalities. Due to the presence of easily isomerizable azo moiety, a porous polymer was obtained. The polymer showed nano and micropores. The battery with the porous polymer showed an impressive specific capacity of 400 mA h/g at 0.2 A/g. If the battery is pre-conditioned, the specific capacity increased to 615 mA h/g at the same current density. The post-mortem analysis of the battery confirmed that the polymer didn't dissolve in the battery electrolyte. The control material is a small molecule with carbonyl and azo moieties that showed a poor specific capacity of 40 mA h/g indicating the necessity to have a hierarchically porous dual-functional polymer.