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The catalytic bis‐allylation of alkynes is an important but challenging protocol to construct all‐carbon tetra‐substituted alkenes. Particularly, the catalytic unsymmetrical bis‐allylation of alkynes remains as an underexplored task to date. We herein report an unprecedented unsymmetrical bis‐allylation by simultaneously utilizing electrophilic trifluoromethyl alkene and nucleophilic allylboronate as the allylic reagents. With the aid of robust Ni0/NHC catalysis, valuable skipped trienes can be obtained in high regio‐ and stereo‐selectivities under mild conditions. Mechanistic studies indicate that the reaction may proceed through a β‐fluorine elimination of a nickelacycle followed by a transmetalation step with allylboronate. The present method exhibits a good tolerance of various functional groups. Besides, the skipped triene products can undergo an array of elaborate transformations, which highlights the potential applications of this strategy. [ABSTRACT FROM AUTHOR]

Skeletal reorganization reactions have emerged as an intriguing tool for converting readily available compounds into complicated molecules inaccessible by traditional methods. Herein, we report a unique skeleton‐reorganizing coupling reaction of cycloheptatriene and cycloalkenones with amines. In the presence of Rh/acid catalysis, cycloheptatriene can selectively couple with anilines to deliver fused 1,2‐dihydroquinoline products. Mechanistic studies indicate that the retro‐Mannich type ring‐opening and subsequent intramolecular Povarov reaction account for the ring reorganization. Our mechanistic studies also revealed that skeleton‐reorganizing amination between anilines and cycloalkenones can be achieved with acid. The synthetic utilization of this skeleton‐reorganizing coupling reaction was showcased with a gram‐scale reaction, synthetic derivatizations, and the late‐stage modification of commercial drugs. [ABSTRACT FROM AUTHOR]

Depending on the reactant property and reaction mechanism, one major regioisomer can be favored in a reaction that involves multiple active sites. Herein, an orthogonal regulation of nucleophilic and electrophilic sites in the regiodivergent hydroamination of isoprene with indazoles is demonstrated. Under Pd‐hydride catalysis, the 1,2‐ or 4,3‐insertion pathway with respect to the electrophilic sites on isoprene could be controlled by the choice of ligands. In terms of the nucleophilic sites on indazoles, the reaction occurs at either the N1‐ or N2‐position of indazoles is governed by the acid co‐catalysts. Preliminary experimental studies have been performed to rationalize the mechanism and regioselectivity. This study not only contributes a practical tool for selective functionalization of isoprene, but also provides a guide to manipulate the regioselectivity for the N‐functionalization of indazoles. [ABSTRACT FROM AUTHOR]

To improve the interfacial properties between carbon fibers (CFs) and polycarbonate (PC) resin, multi-walled carbon nanotubes (MWCNTs) were deposited onto desized CF surfaces using an ultrasonic-assisted electrophoretic deposition method, forming a multi-scaled hierarchical structure. The results showed that morphologies and geometrical structures of the as-prepared hierarchical structures could be readily tailored by varying in length and concentration of the CNT suspension. The optimum conditions were determined to be CNT length of 1-5 μm with suspension concentration of 0.5–1 wt%. A post-treatment, in combination of a polymer binder and laser irradiation, was followed to solidify the morphology and geometry of the CNT network structures formed by the CNTs with length 1-5 μm, which allowed a 22.9% ± 1.6% improvement in the interfacial bonding strength than that without the post-treatment and 68.1% ± 2.3% improvement than bare CF, evaluated by a single-filament fragmentation test. It was the well-defined CNT porous network structures that are favorable for thermoplastic resin infiltration through channels for resin flow and capillary action, thus enhancing the composite interfacial properties. [ABSTRACT FROM AUTHOR]

Five-carbon dimethylallyl units, such as prenyl and reverse-prenyl, are widely distributed in natural indole alkaloids and terpenoids. In conventional methodologies, these valuable motifs are often derived from substrates bearing leaving groups, but these processes are accompanied by the generation of stoichiometric amounts of by-products. From an economical and environmental point of view, the basic industrial feedstock isoprene is an ideal alternative precursor. However, given that electronically unbiased isoprene might undergo six possible addition modes in the coupling reactions, it is difficult to control the selectivity. This article summarizes the strategies we have developed to achieve regioselective C–H functionalizations of isoprene under transition-metal and acid catalysis. 1 Introduction 2 Catalytic Coupling of Indoles with Isoprene 3 Catalytic Coupling of Formaldehyde, Arenes and Isoprene 4 Catalytic Coupling of 4-Hydroxycoumarins with Isoprene 5 Catalytic Coupling of Cyclic 1,3-Diketones with Isoprene 6 Conclusion and Outlook [ABSTRACT FROM AUTHOR]

A regiospecific allyl–allyl coupling reaction between 1,3-dienes and allylboronates has been demonstrated under nickel catalysis. Salient features of this method include the earth-abundant metal catalyst, excellent regioselectivity and good functional group tolerance. Notably, even congested allyl substrates can also be applied to this protocol, thus allowing for the rapid preparation of a series of valuable 1,5-dienes. [ABSTRACT FROM AUTHOR]

The rational design of the microporous layer (MPL) is very important for the water management of proton exchange membrane fuel cells (PEMFC). The uncertainty of pore structure distribution of MPL originated from the random stacking of particles. To facilitate the water transfer at high current density, it is necessary to improve the capillary force of the gas diffusion layer (GDL). The hierarchical porous structure MPL was designed by coating carbon nanotubes (CNTs) with different length-diameter ratios. In the process of constructing the network structure of CNTs, the polyvinylidene fluoride (PVDF)/N-methylpyrrolidone binder/solvent system alleviates the structural and performance defects caused by the agglomeration via an integrated method of dispersion and binding. The optimal current density of PEMFC at 0.2 V can reach 1913.8 mA/cm2 under the optimal MPL structure. The peak power density of GDL-G PVDF prepared with PVDF is 831.8 W/cm2 which is 8.85% and 15.74% higher than that of GDL-1 PVDF and GDL-2 PVDF with single pore structure, respectively. The lowest mass transfer resistance of GDL-G PVDF is 23.71 mΩ, indicating that it can discharge excess water at the catalyst layer/MPL interface to avoid flooding. This design provided a novel strategy for the stable operation of PEMFC at high current density. [Display omitted] • Two types of carbon nanotubes were used to construct MPL with hierarchical network structure. • Enhanced performance of PEMFC was achieved through enhancing capillary pressure. • The optimized properties of MPL ensure ultra-low mass transport resistance. • The MPLs with PVDF/NMP binder/solvent system facilitate the water and gas transport. [ABSTRACT FROM AUTHOR]

Microporous layer (MPL) is commonly applied to gas diffusion layer to improve water management performance of a proton exchange membrane fuel cell (PEMFC). In this work, we introduce a new type of MPL comprising whisker-like carbon nanotubes (WCNTs) and Ketjen Blacks (KBs) onto the macroporous substrate to optimize the pore structures. Scanning electron microscopy images show that KBs populate overlapping networks formed by WCNTs, leading to an increased proportion of mesopores (about 34.87%) of crack-free MPL. This optimal structure of MPL with a superhydrophobic surface ensures the maximum power density up to 2.046 W cm−2 at 100% relative humidity. The electrochemical impedance spectroscopy verifies that the mass transfer resistance is significantly lower, which means rapid drain of excess water and supply of reactant gas, and it is further confirmed by theoretical analysis of pore characteristics. A mechanism of gas-water transport balance promoted by the network structures of MPL constructed by WCNTs/KBs is proposed, which allows enhancing PEMFC performance at high humidity conditions. [Display omitted] • A rational design of carbon network structure in microporous layer was proposed. • Optimal MPL was realized by synergy of Whisker-like CNTs and Ketjen Blacks. • Enhanced performance of PEMFC was achieved through alleviating flooding. • The reformative properties of MPL ensure ultra-low mass transport resistance. [ABSTRACT FROM AUTHOR]

The excellent microporous layers (MPLs) in the gas diffusion layer requires superior mass transfer capacity, which is essential to high-performance proton exchange membrane fuel cells. However, the correspondence between MPL structure and mass transfer performance is ambiguous. Here, we design efficient mass transfer channels in MPLs with evolutionary structures by adjusting the content of whisker-like carbon nanotubes (WCNTs). The cell power density exhibits a bimodal shape with the increase of WCNTs in MPLs, which verifies that the perforated cracks of 5–10 μm in the MPL provide the separated channels for water and gas transport, and the optimal hydrophobic mesopores (34.87%) promote the mass transfer efficiency by elevating the capillary force of water transport. At 100% relative humidity (RH), the peak power densities of cells with the two MPLs are increased to 2.321 W cm−2 and 2.117 W cm−2, respectively. The electrochemical impedance spectroscopy confirms that the impedance of both MPLs are 109.35 mΩ cm2 and 63.55 mΩ cm2 at 100% RH and 3 A cm−2. The simple and scalable strategy provides a novel idea to relieve the mass transport loss of fuel cells. • Mass transfer channels in MPLs with evolutionary structures are designed. • The mass transport performance of PEMFC exhibits a bimodal shape. • Crack morphology of MPLs are controlled by adjusting content of whisker-like CNTs. • Two mechanisms to improve the mass transfer capacity of GDL are proposed. • A novel strategy provides ideas to relieve the mass transport loss of fuel cells. [ABSTRACT FROM AUTHOR]

Background: Accurate preoperative prediction of lymph node metastasis (LNM) in esophageal cancer (EC) patients is of crucial clinical significance for treatment planning and prognosis., Aim: To develop a clinical radiomics nomogram that can predict the preoperative lymph node (LN) status in EC patients., Methods: A total of 32 EC patients confirmed by clinical pathology (who underwent surgical treatment) were included. Real-time fluorescent quantitative reverse transcription-polymerase chain reaction was used to detect the expression of B7-H3 mRNA in EC tissue obtained during preoperative gastroscopy, and its correlation with LNM was analyzed. Radiomics features were extracted from multi-modal magnetic resonance imaging of EC using Pyradiomics in Python. Feature extraction, data dimensionality reduction, and feature selection were performed using XGBoost model and leave-one-out cross-validation. Multivariable logistic regression analysis was used to establish the prediction model, which included radiomics features, LN status from computed tomography (CT) reports, and B7-H3 mRNA expression, represented by a radiomics nomogram. Receiver operating characteristic area under the curve (AUC) and decision curve analysis (DCA) were used to evaluate the predictive performance and clinical application value of the model., Results: The relative expression of B7-H3 mRNA in EC patients with LNM was higher than in those without metastasis, and the difference was statistically significant ( P < 0.05). The AUC value in the receiver operating characteristic (ROC) curve was 0.718 (95%CI: 0.528-0.907), with a sensitivity of 0.733 and specificity of 0.706, indicating good diagnostic performance. The individualized clinical prediction nomogram included radiomics features, LN status from CT reports, and B7-H3 mRNA expression. The ROC curve demonstrated good diagnostic value, with an AUC value of 0.765 (95%CI: 0.598-0.931), sensitivity of 0.800, and specificity of 0.706. DCA indicated the practical value of the radiomics nomogram in clinical practice., Conclusion: This study developed a radiomics nomogram that includes radiomics features, LN status from CT reports, and B7-H3 mRNA expression, enabling convenient preoperative individualized prediction of LNM in EC patients., Competing Interests: Conflict-of-interest statement: All the authors report no relevant conflicts of interest for this article., (©The Author(s) 2024. Published by Baishideng Publishing Group Inc. All rights reserved.)

Skeletal reorganization reactions have emerged as an intriguing tool for converting readily available compounds into complicated molecules inaccessible by traditional methods. Herein, we report a unique skeleton-reorganizing coupling reaction of cycloheptatriene and cycloalkenones with amines. In the presence of Rh/acid catalysis, cycloheptatriene can selectively couple with anilines to deliver fused 1,2-dihydroquinoline products. Mechanistic studies indicate that the retro-Mannich type ring-opening and subsequent intramolecular Povarov reaction account for the ring reorganization. Our mechanistic studies also revealed that skeleton-reorganizing amination between anilines and cycloalkenones can be achieved with acid. The synthetic utilization of this skeleton-reorganizing coupling reaction was showcased with a gram-scale reaction, synthetic derivatizations, and the late-stage modification of commercial drugs., (© 2022 Wiley-VCH GmbH.)

Depending on the reactant property and reaction mechanism, one major regioisomer can be favored in a reaction that involves multiple active sites. Herein, an orthogonal regulation of nucleophilic and electrophilic sites in the regiodivergent hydroamination of isoprene with indazoles is demonstrated. Under Pd-hydride catalysis, the 1,2- or 4,3-insertion pathway with respect to the electrophilic sites on isoprene could be controlled by the choice of ligands. In terms of the nucleophilic sites on indazoles, the reaction occurs at either the N 1 - or N 2 -position of indazoles is governed by the acid co-catalysts. Preliminary experimental studies have been performed to rationalize the mechanism and regioselectivity. This study not only contributes a practical tool for selective functionalization of isoprene, but also provides a guide to manipulate the regioselectivity for the N-functionalization of indazoles., (© 2021 Wiley-VCH GmbH.)