Metal‐Free Reaction of ortho‐Carbonylated Alkynyl‐Substituted Arylaldehydes with Common Amines: Selective Access to Functionalized Isoindolinone and Indenamine Derivatives

Herein we describe a reaction of ortho‐carbonylated alkynyl‐substituted arylaldehydes with common primary amines that can provide functionalized isoindolinone and 3‐hydroxylindenamine products in high yields. Depending on the substituent size of primary amines, two distinct reaction pathways were exploited selectively, that are, an initial aza‐conjugate addition followed by hydrogen transfer to access isoindolinone framework and a unique oxa‐conjugate addition followed by Petasis–Ferrier rearrangement to afford indenamine derivatives. In the presence of Et₃N, the reaction property of small primary amines was changed, proceeding to afford 3‐hydroxylindenamine derivatives efficiently. These products contain interesting substructures that exist in many natural products and bioactive molecules. The reaction features contain the use of transition‐metal‐free catalysts, simple operation, broad substrate scope, and product diversity.     

Is PdII‐Promoted σ‐Bond Metathesis Mechanism Operative for the PdPEPPSI Complex‐Catalyzed Amination of Chlorobenzene with Aniline? Experiment and Theory

Reduction of the Pd?PEPPSI precatalyst to a Pd⁰ species is generally thought to be essential to drive Buchwald–Hartwig amination reactions through the well‐ documented Pd⁰/Pd^II catalytic cycle and little attention has been paid to other possible mechanisms. Considered here is the Pd?PEPPSI‐catalyzed aryl amination of chlorobenzene with aniline. A neat reaction system was used in new experiments, from which the potentially reductive roles of the solvent and labile ligand of the PEPPSI complex in leading to Pd⁰ species are ruled out. Computational results demonstrate that anilido‐containing Pd^II intermediates involving σ‐bond metathesis in pathways leading to the diphenylamine product have relatively low barriers. Such pathways are more favorable energetically than the corresponding reductive elimination reactions resulting in Pd⁰ species and other putative routes, such as the Pd^II/Pd^IV mechanism, single electron transfer mechanism, and halide atom transfer mechanism. In some special cases, if reactants/additives are inadequate to reduce a Pd^II precatalyst, a Pd^II‐involved σ‐bond metathesis mechanism might be feasible to drive the Buchwald–Hartwig amination reactions.     

Zn or O? An Atomic Level Comparison on Antibacterial Activities of Zinc Oxides

For the first time, the influence of different types of atoms (Zn and O) on the antibacterial activities of nanosized ZnO was quantitatively evaluated with the aid of a 3D‐printing‐manufactured evaluation system. Two different outermost atomic layers were manufactured separately by using an ALD (atomic layer deposition) method. Interestingly, we found that each outermost atomic layer exhibited certain differences against gram‐positive or gram‐negative bacterial species. Zinc atoms as outermost layer (ZnO?Zn) showed a more pronounced antibacterial effect towards gram‐negative E. coli (Escherichia coli), whereas oxygen atoms (ZnO?O) showed a stronger antibacterial activity against gram‐positive S. aureus (Staphylococcus aureus). A possible antibacterial mechanism has been comprehensively discussed from different perspectives, including Zn²⁺ concentrations, oxygen vacancies, photocatalytic activities and the DNA structural characteristics of different bacterial species.     

浮升力和流动加速对超临界CO2管内流动传热影响

基于单相流体的概念,超临界流体的异常传热行为已经被研究很多年了,但是关于其流动传热机理仍没有统一的认识.本文通过理论分析和实验研究了超临界二氧化碳在竖直管内向上流动过程中,浮升力和流动加速效应对其流动结构和传热过程的影响.结果表明,没有确凿的实验证据表明超临界流体的异常传热行为是浮升力和流动加速直接导致的,存在的估计浮升力和流动加速效应准则均是在常物性流体的基础上,做了大量假设得出的,不同的研究者采用浮升力和流动加速准则分析超临界流体的传热恶化得出的结论不一致.最后,基于拟沸腾理论分析超临界流体的传热恶化过程,提出超临界沸腾数区分了超临界流体正常传热与恶化传热的转换边界,为超临界流体流动传热研究提供新思路,超临界沸腾数对建立用于不同技术的超临界流体动力循环的最佳运行条件具有重要意义.     

Assembly of ϵ-Keggin Polyoxometalate from Molecular Crystal to Zeolitic Octahedral Metal Oxide

Zeolitic octahedral metal oxides are inorganic crystalline microporous materials with adsorption and redox properties. New ϵ-Keggin nickel molybdate–based zeolitic octahedral metal oxides have been synthesized. ³¹P NMR spectroscopy shows that reduction of Mo^VI-based molybdates forms an ϵ-Keggin polyoxometalate that immediately transfers to the solid phase. Investigation of the formation process indicates that a low Ni concentration, insoluble reducing agent, and long synthesis time are the critical factors for obtaining the zeolite octahedral metal oxides rather than the ϵ-Keggin polyoxometalate molecule. The synthesized zeolitic nickel molybdate with Na⁺ is used as the adsorbent, which effectively separates C₂ hydrocarbon mixtures.     

Fully Chemical Recyclable Poly(γ-butyrolactone)-based Copolymers with Tunable Structures and Properties

Chinese Journal of Polymer Science - The emerging chemical recyclable polymers, such as poly(γ-butyrolactone) (PGBL) and poly((R)-3,4-trans six-membered ring-fused GBL) (P((R)-M)), provide a...     

MOFs-derived hierarchical porous carbon confining the monodisperse Ni and defective WOx for efficient and stable hydrogenolysis of cellulose to ethylene glycol

The one-pot catalytic conversion of cellulose into ethylene glycol (EG) is an attractive way of biomass utilization. However, low-cost, efficient, and stable catalysts are the premise and research challenges of industrial application. Herein, the magnetic recyclable W–Ni@C catalyst was synthesized by in-situ pyrolysis of Ni-MOFs impregnated with ammonium metatungstate. Compared with the Ni-W bimetallic catalysts prepared by the impregnation method and the sol–gel method, the W–Ni@C catalyst for cellulose hydrogenolysis reaction can achieve a higher ethylene glycol yield (67.1% vs 43.3% and 42.6%) and 100% of cellulose conversion rate. The uniformly dispersed Ni nanoparticles and abundant defective WO_x were formed in a reductive atmosphere generated in pyrolysis of Ni-MOFs, which was indispensable for the hydrogenolysis of cellulose into EG. Besides, the hierarchical porous carbon derived from organic ligands in Ni-MOFs reduces the mass transfer resistance while confining Ni nanoparticles and WO_x to prevent their leaching, effectively enhancing the stability of the W–Ni@C catalyst. Therefore, the remarkable catalytic performance, the simple and effective recovery method as well as satisfying stability would make W–Ni@C become a promising catalyst for the conversion of cellulose to EG.

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