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The use of a Cu(iii)–CF3 complex as a novel coupling reagent allows a general esterification reaction with broad substrate scope. Two activated carboxyl species are generated and interact with each other.

A convenient method of formate synthesis is reported using in situ difluorocarbene as a safe CO surrogate, involving sequential O-difluoromethylation followed by α-C–F functionalization.

Exploring earth-abundant electrocatalysts with excellent activity, robust stability, and multiple functions is crucial for electrolytic hydrogen generation. Porous phosphorized CoNi2 S4 yolk-shell spheres (P-CoNi2 S4 YSSs) were rationally designed and synthesized by a combined hydrothermal sulfidation and gas-phase phosphorization strategy. Benefiting from the strengthened Ni3+ /Ni2+ couple, enhanced electronic conductivity, and hollow structure, the P-CoNi2 S4 YSSs exhibit excellent activity and durability towards hydrogen/oxygen evolution and urea oxidation reactions in alkaline solution, affording low potentials of -0.135 V, 1.512 V, and 1.306 V (versus reversible hydrogen electrode) at 10 mA cm-2 , respectively. Remarkably, when used as the anode and cathode simultaneously, the P-CoNi2 S4 catalyst merely requires a cell voltage of 1.544 V in water splitting and 1.402 V in urea electrolysis to attain 10 mA cm-2 with excellent durability for 100 h, outperforming most of the reported nickel-based sulfides and even noble-metal-based electrocatalysts. This work promotes the application of sulfides in electrochemical hydrogen production and provides a feasible approach for urea-rich wastewater treatment.

Prussian blue analogs (PBAs) are considered as reliable and promising cathode materials for aqueous Zn‐ion batteries (AZIBs), but they suffer from low capacity and poor cycling stability due to insufficient active sites and structural damage caused by the ion insertion/extraction processes. Herein, a template‐engaged ion exchange approach has been developed for the synthesis of Co‐substituted Mn‐rich PBA hollow spheres (CoMn‐PBA HSs) as cathode materials for AZIBs. Benefiting from the multiple advantageous features including hollow structure, abundant active sites, fast Zn2+ ion diffusion, and partial Co substitution, the CoMn‐PBA HSs electrode shows efficient zinc ion storage properties in terms of high capacity, decent rate capability and prolonged cycle life., Co‐substituted Mn‐rich Prussian Blue Analog (PBA) hollow spheres (CoMn‐PBA HSs) are rationally designed and synthesized through an efficient self‐templating approach. Benefiting from the hollow structure and partial Co substitution, the CoMn‐PBA HSs electrode exhibits enhanced zinc ion storage performance with high capacity, favorable rate capability, and impressive cycling stability.

A one-pot three-component reaction of two anilines (or one aniline and one alkylamine) and in situ-generated difluorocarbene is developed herein to enable efficient construction of formamidines. Crucial formimidoyl fluoride intermediate RN═CHF is proposed from the reaction of a primary aniline and difluorocarbene. Ensuing nucleophilic iminyl substitution of this intermediate with a second amine allows cross-condensation of the two amines to produce formamidines. When only one type of primary aniline is used as the substrate, the difluoromethylated homo-condensation products can also be produced under a 1:1 molar ratio of aniline/difluorocarbene. Intramolecular variant of this method allows concise synthesis of benzimidazoquinazolines and nitrogen-fused/spirocyclic compounds, showing the potential of this method in organic synthesis. More interesting reactions are anticipated by exploiting the reactivity of difluorocarbene and primary amines to isocyanides or the formimidoyl fluoride intermediates.

Heavy metals in cultivated soil may migrate and transform through the food chain to harm the ecological environment and human health. At present, the ecological environment and human health risks of heavy metals in cultivated soil in Lanzhou city remain unclear, which impacts the effective management and control of heavy metals. The potential ecological risk hazard index was used to evaluate the ecological environmental risks of As, Cd, Cr, Hg, and Pb in the surface soil of cultivated land in Lanzhou, and the health risk model proposed by USEPA and the recommended standard were used to evaluate their human health risk. The main factors influencing the spatial differentiation of human health risk were explored by using geographic detectors. The risk of heavy metals to the ecological environment of the cultivated land surface soil in the study area was mainly medium (65.25%), and small portions were low (13.80%) and high (20.95%). The low-risk areas were mainly located in the southeast of Yongdeng County, the middle and north of Yuzhong County, and the southwest of Gaolan County. Moderate risk areas were distributed in three counties and five districts. The high-risk areas were located in the north and southeast of Yongdeng County, the south of Chengguan District, the northeast of Qilihe, the east of Xigu District, and the middle of Yuzhong County. The non-carcinogenic and carcinogenic risks of five types of heavy metal exposure pathways were as follows:oral ingestionskin contactrespiratory ingestion; generally speaking, children were at higher risk than adults. The non-carcinogenic risk in children was higher than that in adults; however, there was no such risk for local residents, as they were all less than 1. At the same time, the carcinogenic risk of As was greater than 1×10

The development of efficient and low-cost electrocatalysts toward the oxygen evolution reaction (OER) is critical for improving the efficiency of several electrochemical energy conversion and storage devices. Here, we report an elaborate design and synthesis of porous Co-based trimetallic spinel oxide nanoboxes (NiCo2-x Fex O4 NBs) by a novel metal-organic framework engaged strategy, which involves chemical etching, cation exchange, and subsequent thermal oxidation processes. Owing to the structural and compositional advantages, the optimized trimetallic NiCo2-x Fex O4 NBs (x is about 0.117) deliver superior electrocatalytic performance for OER with an overpotential of 274 mV at 10 mA cm-2 , a small Tafel slope of 42 mV dec-1 , and good stability in alkaline electrolyte, which is much better than that of Co-based bi/monometallic spinel oxides and even commercial RuO2 .

A general, convenient, and friendly route for preparing a versatile building block of isocyanides from primary amines is developed. Difluorocarbene, generated in situ from decarboxylation of chlorodifluoroacetate, reacts efficiently with primary amines to produce isocyanides. Various primary amines are well tolerated, including aryl, heteroaryl, benzyl, and alkyl amines, as well as amine residues in amino acids and peptides. Late-stage functionalization of biologically active amines is demonstrated, showing its practical capacity in drug design and peptide modification.

Invasive process of alien species is affected by not only the invaded habitats, but also the surrounding landscape matrix. Understanding the effects of landscape matrix on alien species is of great significance for controlling invasive alien species. We surveyed plant communities along the water-level fluctuating zone (WLFZ) of the Three Gorges Reservoir. Invasive status of alien plant species was evaluated. Totally 10 spatial scales of the surrounding landscape matrix in the scope of 2000 m (including WLFZ) were classified, and 14 landscape indices were applied to analyze the landscape matrix composition and configuration. Using the principal component analysis and correlation analysis, the effects of landscape matrix on the alien invasive plant species and associated scale effect were tested. Results showed that a total of 42 alien invasive plant species were found in the WLFZ, belonging to 17 families and 36 genera. Fuling was a dividing place to differentiate invasive species distribution. The number of the alien invasive species between Fuling and the Three Gorges Dam was found more than that between Fuling and Jiangjin. For the all scales (within 2000 m). The higher the landscape matrix fragmentation was, the more difficult the alien species invading. The higher landscape connectivity was, the easier the alien species invading. The effects of landscape matrix composition and configuration on the invasive plant diversity at large scales (1200-2000 m) was more significant than those at small scales (200-1000 m), in which landscape matrix composition and configuration at 1200-1400 m showed the strongest effect, demonstrating a significant spatial scale effect. Different invasive plant species showed the scale effects of landscape matrix composition and configuration. At all scales,外来物种入侵过程不仅受入侵地生境的影响,也受到周边景观基质的影响。厘清景观基质对外来入侵物种的影响,对于外来物种的入侵管控具有重要意义。本研究针对长江三峡库区消落带植物群落开展调查,评估三峡库区消落带外来植物入侵现状;在岸线以上(含消落带)2000 m范围内划分出10个景观格局尺度,采用14个指标分析景观基质组成结构;通过主成分分析和相关分析,探究景观基质组成结构对外来植物入侵的影响以及空间尺度效应。结果表明: 三峡库区消落带外来入侵植物共17科36属42种,其分布呈现出以涪陵为界的特征,涪陵至三峡大坝的外来入侵物种多于涪陵至江津段。整体上(2000 m尺度内),景观基质破碎化程度越高,外来植物入侵难度越大;景观连通性越高,外来植物越容易入侵。大尺度上(1200～2000 m)的景观组成结构对入侵植物多样性的影响明显大于小尺度(200～1000 m),其中,1200～1400 m尺度的影响最强,呈明显的空间尺度效应。不同入侵植物受景观基质组成结构的影响也表现出尺度效应。其中,苍耳和大狼把草与景观组成结构指标在各个尺度下均表现出弱相关性,而狼把草及小蓬草与景观基质组成结构表现出强相关性。景观基质组成结构与外来植物入侵密切关联,且具明显尺度效应。外来植物入侵可追溯到大尺度的景观基质,以小尺度内草地、森林等斑块类型为“脚踏石”过渡,最终达到消落带。针对消落带外来植物的管控,应该在强化消落带生境管理的基础上,加强景观基质不同尺度上的土地利用管理和优化,形成多元化的综合管控模式。.

Hierarchical FeCoS2 -CoS2 double-shelled nanotubes have been rationally designed and constructed for efficient photocatalytic CO2 reduction under visible light. The synthetic strategy, engaging the two-step cation-exchange reactions, precisely integrates two metal sulfides into a double-shelled tubular heterostructure with both of the shells assembled from ultrathin two-dimensional (2D) nanosheets. Benefiting from the distinctive structure and composition, the FeCoS2 -CoS2 hybrid can reduce bulk-to-surface diffusion length of photoexcited charge carriers to facilitate their separation. Furthermore, this hybrid structure can expose abundant active sites for enhancing CO2 adsorption and surface-dependent redox reactions, and harvest incident solar irradiation more efficiently by light scattering in the complex interior. As a result, these hierarchical FeCoS2 -CoS2 double-shelled nanotubes exhibit superior activity and high stability for photosensitized deoxygenative CO2 reduction, affording a high CO-generating rate of 28.1 μmol h-1 (per 0.5 mg of catalyst). Ministry of Education (MOE) National Research Foundation (NRF) Accepted version X. W. L. acknowledges the funding support from the National Research Foundation (NRF) of Singapore via the NRF investigatorship (NRF-NRFI2016-04), and the Ministry of Education of Singapore through the Academic Research Fund (AcRF) Tier-2 grant (MOE2017-T2-2-003) and Tier-1 grant (RG116/18).

This study describes a benign C-H cyanation of terminal alkynes with α-cyanoesters serving as a nontoxic cyanide source. In situ generation of the key copper cyanide intermediate is proposed by a sequence of α-C-H oxidation and copper-mediated β-carbon elimination of α-cyanoesters, releasing the α-ketoester byproduct observed experimentally. The ensuing reaction of copper cyanide with terminal alkynes delivers preferentially cyanoalkynes and surpasses the possible Glaser type dimerization of terminal alkynes or the undesired accumulation of HCN under protic conditions. The presence of the co-oxidant K2S2O8 is crucial to this selectivity, probably by promoting oxidative transmetalation and the resulting formation of the Cu(iii)(acetylide)(CN) intermediate. All the reagents and salts used are commercially available, cheap and nontoxic, avoiding the use of highly toxic cyanide salts typically required in cyanation studies. The scope of this reaction is demonstrated with a set of alkynes and α-cyanoesters. The application of this method to late-stage functionalization of the terminal alkyne group in an estrone derivative is also feasible, showing its practical value for drug design.

The rational design of catalysts' spatial structure is vitally important to boost catalytic performance through exposing the active sites, enhancing the mass transfer, and confining the reactants. Herein, a dual-linker zeolitic tetrazolate framework-engaged strategy is developed to construct assembled hollow plates (AHP) of N-rich carbon (NC), which is loaded with single-Ni atoms to form a highly efficient electrocatalyst (designated as Ni-NC(AHP)). In the carbonization process, the thermally unstable linker (5-aminotetrazole) serves as the self-sacrificial template and the other linker (2-methylimidazole) mainly serves as the carbon and nitrogen source to form hollow NC matrix. The formed Ni-NC(AHP) catalyst possesses enhanced mesoporosity and more available surface area, thus promoting mass transport and affording abundant accessible single-Ni sites. These features contribute to remarkable performance for electrochemical CO

Exploring earth-abundant electrocatalysts with excellent activity, robust stability, and multiple functions is crucial for electrolytic hydrogen generation. Porous phosphorized CoNi

To evaluate the pollution by polycyclic aromatic hydrocarbons (PAHs) in the surface soil of the core urban area of Lanzhou, 62 topsoil samples were collected from the area. The soil samples were analyzed for the content of 16 priority PAHs, using gas chromatography-mass spectrometry. Descriptive statistical methods were used to characterize contamination by PAHs. An absolute principal component analysis-multiple linear regression (APCS-MLR) model was applied to determine the sources of PAHs in the soil samples, and the accuracy of the model results was verified. Finally, the main influence regions of each source were determined with a geo-statistical method. The results showed that the contents of Σ

Ag nanoparticle–embedded nitrogen-doped carbon macroporous fibers are rationally designed as the host for Li metal anodes., Lithium metal has been considered as an ideal anode candidate for future high energy density lithium batteries. Herein, we develop a three-dimensional (3D) hybrid host consisting of Ag nanoparticle–embedded nitrogen-doped carbon macroporous fibers (denoted as Ag@CMFs) with selective nucleation and targeted deposition of Li. The 3D macroporous framework can inhibit the formation of dendritic Li by capturing metallic Li in the matrix as well as reducing local current density, the lithiophilic nitrogen-doped carbons act as homogeneous nucleation sites owing to the small nucleation barrier, and the Ag nanoparticles improve the Li nucleation and growth behavior with the reversible solid solution–based alloying reaction. As a result, the Ag@CMF composite enables a dendrite-free Li plating/stripping behavior with high Coulombic efficiency for more than 500 cycles. When this anode is coupled with a commercial LiFePO4 cathode, the assembled full cell manifests high rate capability and stable cycling life.

We report herein a strategy of ammonium hydrogen-bonding-assisted α-F elimination from Cu–CF3 compounds that generates R3N·HF reagents in situ. Combining this strategy and Cu(III)–CF3 chemistry with alkynes, dual fluorination and trifluoromethylation of terminal alkynes is enabled by a single Cu(III)–CF3 compound assisted by a tertiary amine with excellent regio- and stereoselectivity. This strategy also enables the development of other reaction types involving trapping of the in situ-formed R3N·HF reagents by other electrophilic groups and can be used for the late-stage functionalization of estrone derivatives.

Amadori rearrangement product (ARP) derived from glutamic acid (Glu) and xylose (Xyl) was prepared by aqueous Maillard reaction. Subsequently, ion exchange chromatography, MS, and NMR were used for purification and identification, confirming that the molecular formula of ARP was C10 H17 NO8 , namely N-(1-deoxy-α-D-xylulos-1-yl)-glutamic acid, with a molecular mass of 279 Da. To improve the aqueous yield of ARP, a thermal reaction coupled with vacuum dehydration was used and the yield of ARP was increased from 2.07% to 75.11%. Furthermore, flavor formation capacity of ARP by a thermal treatment simulated to a baking process was compared with Maillard reaction products, Maillard-dehydration reaction products, and Glu-Xyl mixture. The results indicated that a larger amount of volatile flavor compounds and a biscuit-like, burnt aroma was generated rapidly from the mixture of ARP and unreacted Glu-Xyl, which could be a potential flavor enhancer for baked foods. PRACTICAL APPLICATION: Maillard reaction performed in aqueous medium through thermal reaction combined with vacuum dehydration is a novel and practical technology that could be widely used to produce Maillard reaction intermediates (MRIs), such as Amadori or Heyns rearrangement products, which are regarded as significant nonvolatile aroma precursors and have stable physical and chemical properties compared with Maillard reaction products (MRPs). MRI derived from glutamic acid and xylose is a potential substitute of MRPs for flavorings preparation and shows a great capacity to generate fresh flavors in a short time at high temperature, which meets the requirements of baking foods. Therefore, the new developed method could be a promising tool for MRI preparation and application in food and flavoring industries.

The formation conditions of the Amadori compound (ARP) N-(1-deoxy-d-xylulos-1-yl)-alanine were determined in an aqueous Maillard reaction between l-alanine and d-xylose under a two-step temperature rising process with (-)-epigallocatechin gallate (EGCG) as an indicator followed by browning intensity detection of the final Maillard reaction products (MRPs). To clarify the mechanism of EGCG indication on the ARP formation, the change in the concentration of some key products generated during the Maillard reaction with EGCG addition was investigated. Results showed an inhibition effect of EGCG on the browning precursor formation through the generation of ARP-EGCG adducts and deoxyosone-EGCG adducts, which was proposed as an important pathway to inhibit browning during the Maillard reaction and to indicate ARP formation.

Organometallic reagents, in particular Pd(ii)- and Au(iii)-aryl reagents, have recently emerged as an efficient tool for bioconjugation. However, the detailed mechanism and origins of chemoselectivity are not well established, but are highly desirable from both synthetic and theoretical viewpoints. In this paper, we report that a computational study dealing with the reaction mechanism of Au(iii)-aryl reagents enabled selective cysteine S-arylation of peptides and proteins developed by Maynard and Spokoyny et al. (J. Am. Chem. Soc., 2018, 140, 7065). Our calculation results suggest that the reaction proceeds by a cationic Au(iii)/Au(i) pathway involving elementary steps of (a) binding of the SH residue to the Au(iii) center, (b) deprotonation of the SH residue, and (c) reductive elimination from a key four-coordinate square planar (L)Au(iii)(thiolate)(Ar) (L is a P,N-bidentate ligand) intermediate. Furthermore, the chemoselectivity of S-arylation against arylation of other nucleophilic residues can be rationalized in terms of energy demand of the three elementary steps. For instance, amine N-arylation is more difficult than S-arylation due majorly to the much higher energy required for deprotonation of much more basic N-H bonds than for deprotonation of weakly acidic S-H bonds. Carboxylate O-arylation is challenging due to the high activation energy of reductive elimination from LAu(iii)(carboxylate)(aryl), because carboxylate is much less nucleophilic than thiolate. These results thus identify acidity and nucleophilicity of the residue as two inherent factors for bioconjugation. This study provides a useful and convenient approach for predicting and rationalizing the feasibility and chemoselectivity of related bioconjugation reactions.

The development of efficient and low-cost electrocatalysts toward the oxygen evolution reaction (OER) is critical for improving the efficiency of several electrochemical energy conversion and storage devices. Here, we report an elaborate design and synthesis of porous Co-based trimetallic spinel oxide nanoboxes (NiCo

Non-noble-metal-based nanomaterials can exhibit extraordinary electrocatalytic performance toward the oxygen evolution reaction (OER) by harnessing the structural evolution during catalysis and the synergistic effect between elements. However, the structure of active centers in bimetallic/multimetallic catalysts is under long-time debate in the catalysis community. Here, an efficient bimetallic Ni-Fe selenide-derived OER electrocatalyst is reported and the structure-activity correlation during the OER evolution studied. By combining experiments and theoretical calculations, a conceptual advance is provided, in that the local coordination structure distortion and disordering of active sites inherited from the pre-catalyst and post-formed by a further reconstruction are responsible for boosting the OER performance. The active center is identified on Ni sites showing moderate bindings with oxygenous intermediates rather than Fe sites with strong and poisonous adsorptions. These findings provide crucial understanding in manipulating the local coordination and electronic structures toward rational design and fabrication of efficient OER electrocatalysts. Ministry of Education (MOE) Submitted/Accepted version X.W.L. acknowledges the funding support from the Ministry of Education of Singapore through the Academic Research Fund (AcRF) Tier-2 grant (MOE2019-T2-2-049). The National Science Fund for Distinguished Young Scholars (21825106) and the China Postdoctoral Science Foundation (2020M682333) are also acknowledged.

Highly efficient electrocatalysts are essential for the production of green hydrogen from water electrolysis. Herein, a metal-organic framework-assisted pyrolysis-replacement-reorganization approach is developed to obtain ultrafine Pt-Co alloy nanoparticles (sub-10 nm) attached on the inner and outer shells of porous nitrogen-doped carbon nanotubes (NCNT) with closed ends. During the thermal reorganization, the migration of Pt-Co nano-alloys to both surfaces ensures the maximized exposure of active sites while maintaining the robust attachment to the porous carbon matrix. Density functional theory calculations suggest a nearly thermodynamically-neutral free energy of adsorption for hydrogen intermediates and diversified active sites induced by alloying, thus resulting in a great promotion in intrinsic activity towards the hydrogen evolution reaction (HER). Benefiting from the delicate structural design and compositional modulation, the optimized Pt3 Co@NCNT electrocatalyst manifests outstanding HER activity and superior stability in both acidic and alkaline media. Ministry of Education (MOE) National Research Foundation (NRF) Accepted version X.W.L. acknowledges funding support from the National Research Foundation (NRF) of Singapore via the NRF investigatorship (NRF-NRFI2016-04), and Ministry of Education of Singapore via the AcRF Tier-2 grant (MOE2019-T2-2-049).

A field experiment was conducted in maize-cultivated sandy loam soil in the old flooded area of the Yellow River to evaluate the responses of N

Electrocatalysts based on hierarchically structured and heteroatom-doped non-noble metal oxide materials are of great importance for efficient and low-cost electrochemical water splitting systems. Herein, the synthesis of a series of hierarchical hollow nanoplates (NPs) composed of ultrathin Co

Hierarchical FeCoS

Limited by the sluggish four‐electron transfer process, designing high‐performance nonprecious electrocatalysts for the oxygen evolution reaction (OER) and oxygen reduction reaction (ORR) is urgently desired for efficient rechargeable Zn–air batteries (ZABs). Herein, the successful synthesis of porous nitrogen‐doped cobalt pyrite yolk–shell nanospheres (N‐CoS2 YSSs) is reported. Benefiting from the abundant porosity of the porous yolk–shell structure and unique electronic properties by nitrogen doping, the as‐prepared N‐CoS2 YSSs possess more exposed active surface, thus giving rise to superior activity for reversible oxygen electrocatalysis and outstanding cycling stability (more than 165 h at 10 mA cm−2) in ZABs, exceeding the commercial Pt/C and RuO2 hybrid catalysts. Moreover, the assembled ZABs, delivering a specific capacity of 640 mAh gZn −1, can be used for practical devices. This work provides a novel tactic to engineer sulfides as high efficiency and promising bifunctional oxygen electrocatalysts for advanced metal–air batteries., Nitrogen‐doped cobalt pyrite yolk–shell spheres (N‐CoS2 YSSs) are synthesized by a facile two‐step method. The unique morphological architecture and electronic properties endow N‐CoS2 YSSs with more exposed active sites and they are thus suitable for rapid charge transfer, resulting in superior activity for reversible oxygen electrocatalysis and outstanding cycling stability in Zn–air batteries.

There is no consensus on the drying methods of Salvia miltiorrhiza in ancient and modern times,especially on the content of phenolic acid in fresh S. miltiorrhiza. In order to further explore the content of main components in fresh S. miltiorrhiza and study the dynamic changes during the drying process,the content of main components was used as the index in this study to evaluate the processing method,drying method,correlation between dehydration rate and component content for fresh S. miltiorrhiza. In addition,the sealed and unsealed parallel control groups were set to carry out verification test during the drying process. UPLC method was used for determination of seven main components including rosmarinic acid,lithosperic acid,salvianolic acid B,cryptotanshinone,tanshinoneⅠ,methylene salianolate and tanshinone ⅡAin S. miltiorrhiza. The results showed that the fresh S. miltiorrhiza contained low levels of phenolic acid,and the content of phenolic acid increased significantly with the increase of dehydration rate during drying process,while the change of tanshinone was not obvious. In the comparison of three drying methods,we found that drying at 50 ℃ was better than drying in the sun,and drying in the sun was superior to drying in the shade. So,drying at 50 ℃ was the best drying method. The correlation between dehydration and phenolic acid content of S. miltiorrhiza was analyzed by verification test and SPSS software,which further proved that the dehydration rate was significantly positively correlated with the content of phenolic acid components. This study provides reference for the production processing and drying methods of S. miltiorrhiza medicinal materials,which is of great significance for improving the quality of S. miltiorrhiza.

This paper reports a computational study elucidating reaction mechanism for amide bond formation from esters and amines catalyzed by acetic acid. Two optional mechanisms (namely, classic stepwise and concerted acyl substitution mechanisms) have been studied. Calculation results establish the reaction energy profiles of both mechanisms and locate all the intermediates and transition states in both catalytic cycles. Our results propose that the concerted acyl substitution mechanism may be more likely wherein the formation of C N bond and the cleavage of C O bond occur concurrently without the need of rehybridization of the carbonyl carbon. This is also consistent with the fact that no significant racemization/epimerization were observed in the amide products when asymmetric esters and/or amines were used as the reactants, because concerted acyl substitution mechanism precludes the intermediacy of tetrahedral adducts and the accompanying generation/elimination of new chiral centers. Further discussion implies that the concerted acyl substitution mechanism may widely occur in related amidation reactions in the presence of different types of coupling reagents.

Objective To investigate the effect of microRNA-133b(miR-133b)on cardiac fibrosis and its mechanism.Methods Human cardiac fibroblasts(CFs)were harvested.The proliferation of CFs was detected by CCK8 during the overexpression and knock-down of miR-133b.The expressions of connective tissue growth factor(CTGF),α-smooth muscle actin(α-SMA),collagen Ⅰ,and collagen Ⅲ were detected with qRT-PCR and Western blot analysis after miR-133b overexpression or downexpression.Target genes of miR-133b were predicted by bioinformatics software.Dual-luciferase activity assay were used to verify a target gene of miR-133b.Results qRT-PCR showed that the expression level of miR-133b in the miR-133b mimic group was significantly higher than that in the negative control group(

An efficient and selective hydro-trifluoromethylation of terminal alkynes is developed to enable the synthesis of 1,2-disubstituted trifluoromethylated Z-alkenes from terminal alkynes, a silane and a Cu(III)–CF3 complex in DMF. The unusual Z-selectivity and the compatibility of various functional groups make this reaction complementary to previous vinyl–CF3 bond-forming methods producing dominantly E-products or a mixture of E,Z-isomers. Extensive mechanistic studies indicate that this reaction may involve a key step of migratory insertion of initially formed Ar–C≡C–CF3 into LCu(I)-H intermediate and subsequent hydrogenation of the vinyl-copper species to give finally the Z-trifluoromethylated styrenes. Deuterium labeling experiments show that DMF acts not merely as the solvent but also as the source of α-H in the Z-trifluoromethylated styrene products. Given the novel syn-difunctionalization of alkynes using Cu(III)–CF3 complexes/a nucleophilic reagent we developed recently that are also in contrast to t...

The selective catalytic reduction (SCR) system for NOX removal in coal-fired power plants has a promoting effect on the oxidation and removal of elemental mercury. In this study, basic mechanism of mercury oxidation by V2O5-based SCR catalyst is investigated via density functional theory method and the periodic slab models. Calculations are conducted to determine the adsorption energies and geometries of Hg0, HgCl, HgCl2 and HCl on V2O5(001) surface, and to reveal the energy profile of oxidation reaction and the structures of relative transition states and intermediates. The results indicate that HCl can significantly promote Hg0 oxidation on V2O5(001) surface, by forming an intermediate HgCl-surface which is important for Hg0 oxidation. The Hg0 oxidation goes through Hg0 → HgCl → HgCl2, and the two stages of the reaction follow Eley–Rideal mechanism and Langmuir-Hinshelwood mechanism, respectively. The formation of HgCl2 is the rate-determining step due to its high energy barrier. Three detailed reaction pathways are obtained, and the related energy profiles and structures are analyzed in detail. The Hg0 oxidation reaction can take place through all three pathways even if differences exist in each other, while pathways I and II have relatively low energy barriers.

One-step concurrent fluoro-trifluoromethylation across the triple bond of arylacetylenes in a syn mode is enabled by the collaboration of (phen)CuIII(CF3)3 and CsF that produces chemo-, regio-, and stereoselectively (Z)-α-fluoro-β-CF3 styrenes. This method can be extended to achieve syn-oxy-trifluoromethylation and syn-aryl-trifluoromethylation of alkynes using phenoxides, alkoxides, or phenylboronic acid in place of CsF. It opens up new opportunities for preparing various functionalized trifluoromethylated Z-alkenes and demonstrates the potential of Cu(III)–CF3 complexes in organic synthesis.

The rational design of catalysts' spatial structure is vitally important to boost catalytic performance through exposing the active sites, enhancing the mass transfer, and confining the reactants. Herein, a dual-linker zeolitic tetrazolate framework-engaged strategy is developed to construct assembled hollow plates (AHP) of N-rich carbon (NC), which is loaded with single-Ni atoms to form a highly efficient electrocatalyst (designated as Ni-NC(AHP)). In the carbonization process, the thermally unstable linker (5-aminotetrazole) serves as the self-sacrificial template and the other linker (2-methylimidazole) mainly serves as the carbon and nitrogen source to form hollow NC matrix. The formed Ni-NC(AHP) catalyst possesses enhanced mesoporosity and more available surface area, thus promoting mass transport and affording abundant accessible single-Ni sites. These features contribute to remarkable performance for electrochemical CO2 reduction with exceptionally high selectivity of nearly 100% towards CO in a wide potential range and dramatically enhanced CO partial current density.

Chemoselective access to either γ-ketoesters with a quaternary all-carbon α-stereogenic center or γ-keto nitriles is described by copper-catalyzed aerobic reaction of styrenes with α-cyanoesters. Formal oxo-enolation or oxo-cyanomethylation of styrenes is achieved via a sequence of addition of enolate (or cyanomethyl) radical to olefin and oxidation of the resulting radical adduct. This method starts from abundant and cheap feedstock under aerobic conditions, without any prefunctionalization or the production of stoichiometric metal salts waste, making it very attractive for practical use.