Rare homodinuclear Co (II) complex Co2(L)NO3 (1) and helical centrosymmetric homotetranuclear Cu (II) complex Cu4(L)2(H2O)2·2ClO4 (2), have been synthesized by a newly explored bis (salamo)‐like ...tetraoxime ligand (H3L) with Co (NO3)2·6H2O and Cu (ClO4)2·6H2O, respectively, and characterized by elemental analyses, IR, UV–Vis spectroscopy and single crystal X‐ray crystallography. X‐ray crystallographic studies indicate that the two Co (II) atoms (Co1 and Co2) in complex 1 have different N2O4 and N2O3 coordination spheres, and distorted octahedral (Co1) and slightly distorted triangular bipyramidal (Co2) geometries, while Cu (II) atoms in complex 2 have also two different N2O4 (Cu1) and N2O3 (Cu2) coordination environments, and complex 2 forms a helical centrosymmetric molecule. In addition, supramolecular interactions, Hirshfeld surfaces analyses, antibacterial and fluorescence properties were also investigated in detail.
Two homomultinuclear Co (II) and Cu (II) complexes, Co2(L)NO3 (1) and Cu4(L)2(H2O)2·2ClO4 (2) with a salamo‐like tetraoxime ligand H3L have been synthesized, and characterized by IR, UV–vis, X‐ray crystallography, Hirshfeld surfaces analyses and antibacterial activities.
Rearrangement reactions have attracted considerable interest over the past decades due to their high bond-forming efficiency and atom economy in the construction of complex organic architectures. In ...contrast to the well-established 3,3-rearrangement, 1,3 O-to-C rearrangement has been far less vigorously investigated, and stereospecific 1,3-rearrangement is extremely rare. Here, we report a metal-free intramolecular hydroalkoxylation/1,3-rearrangement, leading to the practical and atom-economical assembly of various valuable medium-sized lactams with wide substrate scope and excellent diastereoselectivity. Moreover, such an asymmetric cascade cyclization has also been realized by chiral Brønsted acid-catalyzed kinetic resolution. In addition, biological tests reveal that some of these medium-sized lactams displayed their bioactivity as antitumor agents against melanoma cells, esophageal cancer cells and breast cancer cells. A mechanistic rationale for the reaction is further supported by control experiments and theoretical calculations.
Long-term air pollution data with high temporal and spatial resolutions are needed to support the research of physical and chemical processes that affect the air quality, and the corresponding health ...risks. However, such datasets were not available in China until recently. For the first time, this study examines the spatial and temporal variations of PM2.5, PM10, CO, SO2, NO2, and 8h O3 in 31 capital cities in China between March 2013 and February 2014 using hourly data released by the Ministry of Environmental Protection (MEP) of China. The annual mean concentrations of PM2.5 and PM10 exceeded the Chinese Ambient Air Quality Standards (CAAQS), Grade I standards (15 and 40μg/m3 for PM2.5 and PM10, respectively) for all cities, and only Haikou, Fuzhou and Lasa met the CAAQS Grade II standards (35 and 70μg/m3 for PM2.5 and PM10, respectively). Observed PM2.5, PM10, CO and SO2 concentrations were higher in cities located in the North region than those in the West and the South-East regions. The number of non-attainment days was highest in the winter, but high pollution days were also frequently observed in the South-East region during the fall and in the West region during the spring. PM2.5 was the largest contributor to the air pollution in China based on the number of non-attainment days, followed by PM10, and O3. Strong correlation was found between different pollutants except for O3. These results suggest great impacts of coal combustion and biomass burning in the winter, long range transport of windblown dust in the spring, and secondary aerosol formation throughout the year. Current air pollution in China is caused by multiple pollutants, with great variations among different regions and different seasons. Future studies should focus on improving the understanding of the associations between air quality and meteorological conditions, variations of emissions in different regions, and transport and transformation of pollutants in both intra- and inter-regional contexts.
•Temp-spatial variations of air pollutants in 31 Chinese cities were analyzed.•Major cities in China experience severe air pollution.•Significant temp-spatial differences in criteria air pollutants were observed.•Strong correlation was found between different pollutants except for O3.•China’s pollution is caused by multi-pollutants with temp-spatial variations.
Chiral Brønsted acid-catalysed asymmetric synthesis has received tremendous interest over the past decades, and numerous efficient synthetic methods have been developed based on this approach. ...However, the use of chiral Brønsted acids in these reactions is mostly limited to the activation of imine and carbonyl moieties, and the direct activation of carbon–carbon triple bonds has so far not been invoked. Here we show that chiral Brønsted acids enable the catalytic asymmetric dearomatization reactions of naphthol-, phenol- and pyrrole-ynamides by the direct activation of alkynes. This method leads to the practical and atom-economic construction of various valuable spirocyclic enones and 2H-pyrroles that bear a chiral quaternary carbon stereocentre in generally good-to-excellent yields with excellent chemo-, regio- and enantioselectivities. The activation mode of chiral Brønsted acid catalysis revealed in this study is expected to be of broad utility in catalytic asymmetric reactions that involve ynamides and the related heteroatom-substituted alkynes.Chiral Brønsted acid catalysis is mostly limited to the activation of imine and carbonyl moieties. Now, by direct activation of alkynes, chiral Brønsted acids have been used to enable the catalytic asymmetric dearomatization of naphthol-, phenol- and pyrrole-ynamides for the construction of various spirocyclic enones and 2H-pyrroles bearing a chiral quaternary carbon stereocentre.
Three rare heteromultinuclear complexes, ∞NiL(4,4′‐bipy)Pr (NO3)3·(CH3)2CHOH (1), {CuLSm (NO3)3}2(4,4′‐bipy)·CH3OH (2) and {CuL (CH3CH2OH)Eu (NO3)3 (3) with a symmetrical salamo‐like hexadentate ...ligand H2L have been synthesized, and characterized by FT‐IR, UV–vis and X‐ray crystallography. Complex 1 is a 1D coordination polymer constructed from heterobimetallic Ni(L)Pr (NO3)3 units which are connected by the exo‐dentate ligand 4,4′‐bipy bearing nitrogen‐donor atoms. Complex 2 is a heterotetranuclear dimer based on Cu(L)Sm (NO3)3 moieties which are linked through the exo‐dentate 4,4′‐bipy hasing nitrogen‐donor atoms. Complex 3 is a heterodinuclear structure, Cu (II) atom is five‐coordinate possessing a distorted square pyramidal geometry, and Eu (III) atom is a deca‐coordinate adopting a distorted bicapped square antiprism. In addition, fluorescence and antimicobial properties of the ligand H2L and its complexes 1–3 have also been discussed.
Three rare heteromultinuclear complexes, ∞NiL(4,4′‐bipy)Pr (NO3)3·(CH3)2CHOH (1), {CuLSm (NO3)3}2(4,4′‐bipy)·CH3OH (2) and {CuL (CH3CH2OH)Eu (NO3)3 (3) with a symmetrical salamo‐like hexadentate ligand H2L have been synthesized, and characterized by FT‐IR, UV–vis and X‐ray crystallography. In addition, fluorescence and antimicobial properties of the ligand H2L and its complexes 1–3 have also been discussed.
China has been experiencing severe air pollution in recent decades. Although an ambient air quality monitoring network for criteria pollutants has been constructed in over 100 cities since 2013 in ...China, the temporal and spatial characteristics of some important pollutants, such as particulate matter (PM) components, remain unknown, limiting further studies investigating potential air pollution control strategies to improve air quality and associating human health outcomes with air pollution exposure. In this study, a yearlong (2013) air quality simulation using the Weather Research and Forecasting (WRF) model and the Community Multi-scale Air Quality (CMAQ) model was conducted to provide detailed temporal and spatial information of ozone (O3), total PM2.5, and chemical components. Multi-resolution Emission Inventory for China (MEIC) was used for anthropogenic emissions and observation data obtained from the national air quality monitoring network were collected to validate model performance. The model successfully reproduces the O3 and PM2.5 concentrations at most cities for most months, with model performance statistics meeting the performance criteria. However, overprediction of O3 generally occurs at low concentration range while underprediction of PM2.5 happens at low concentration range in summer. Spatially, the model has better performance in southern China than in northern China, central China, and Sichuan Basin. Strong seasonal variations of PM2.5 exist and wind speed and direction play important roles in high PM2.5 events. Secondary components have more boarder distribution than primary components. Sulfate (SO42−), nitrate (NO3−), ammonium (NH4+), and primary organic aerosol (POA) are the most important PM2.5 components. All components have the highest concentrations in winter except secondary organic aerosol (SOA). This study proves the ability of the CMAQ model to reproduce severe air pollution in China, identifies the directions where improvements are needed, and provides information for human exposure to multiple pollutants for assessing health effects.
Objective
This study was undertaken to uncover the pathophysiologic role of discoidin domain receptor 2 (DDR‐2), a putative fibrillar collagen receptor, in inflammation promotion and joint ...destruction in rheumatoid arthritis (RA).
Methods
In synovial tissue from patients with RA and from mice with collagen antibody–induced arthritis (CAIA) (using Ddr2−/− and DBA/1 mice), gene and protein expression levels of DDR‐2, interleukin‐15 (IL‐15), and Dkk‐1 were measured by quantitative reverse transcription–polymerase chain reaction, Western blotting, and immunohistochemistry. Gene knockdown of DDR2 in human RA fibroblast‐like synoviocytes (FLS) was conducted via small interfering RNA. Interaction between the long noncoding RNA H19 and microRNA 103a (miR‐103a) was assessed in RA FLS using RNA pulldown assays. Cellular localization of H19 was examined using fluorescence in situ hybridization assays. Chromatin immunoprecipitation and dual luciferase reporter assays were applied to verify H19 transcriptional and posttranscriptional regulation by miR‐103a.
Results
DDR2 messenger RNA (mRNA) expression was significantly associated with the levels of IL‐15 and Dkk‐1 mRNA in the synovial tissue of RA patients (r2 = 0.2022–0.3293, all P < 0.05; n = 33) and with the serum levels of IL‐15 and Dkk‐1 in mice with CAIA (P < 0.05). In human RA FLS, activated DDR‐2 induced the expression of H19 through c‐Myc. Moreover, H19 directly interacted with and promoted the degradation of miR‐103a.
Conclusion
These results indicate a novel role for activated DDR‐2 in RA FLS, showing that DDR‐2 is responsible for regulating the expression of IL‐15 and Dkk‐1 in RA FLS and is involved in the promotion of inflammation and joint destruction during pathophysiologic development of RA. Moreover, DDR‐2 inhibition, acting through the H19–miR‐103a axis, leads to reductions in the inflammatory reaction and severity of joint destruction in mice with CAIA, suggesting that inhibition of DDR‐2 may be a potential therapeutic strategy for RA.
A revised Community Multi-scale Air Quality (CMAQ) model with updated secondary organic aerosol (SOA) yields and a more detailed description of SOA formation from isoprene oxidation was applied to ...study the spatial and temporal distribution of SOA in China in the entire year of 2013. Predicted organic carbon (OC), elemental carbon and volatile organic compounds agreed favorably with observations at several urban areas, although the high OC concentrations in wintertime in Beijing were under-predicted. Predicted summer SOA was generally higher (10–15 µg m−3) due to large contributions of isoprene (country average, 61 %), although the relative importance varies in different regions. Winter SOA was slightly lower and was mostly due to emissions of alkane and aromatic compounds (51 %). Contributions of monoterpene SOA was relatively constant (8–10 %). Overall, biogenic SOA accounted for approximately 75 % of total SOA in summer, 50–60 % in autumn and spring, and 24 % in winter. The Sichuan Basin had the highest predicted SOA concentrations in the country in all seasons, with hourly concentrations up to 50 µg m−3. Approximately half of the SOA in all seasons was due to the traditional equilibrium partitioning of semivolatile components followed by oligomerization, while the remaining SOA was mainly due to reactive surface uptake of isoprene epoxide (5–14 %), glyoxal (14–25 %) and methylglyoxal (23–28 %). Sensitivity analyses showed that formation of SOA from biogenic emissions was significantly enhanced due to anthropogenic emissions. Removing all anthropogenic emissions while keeping the biogenic emissions unchanged led to total SOA concentrations of less than 1 µg m−3, which suggests that manmade emissions facilitated biogenic SOA formation and controlling anthropogenic emissions would result in reduction of both anthropogenic and biogenic SOA.
The authors examines the formation of fine particulate matter in urban areas. Topics discussed include new particle formation and aging of primary particles.
An emerging class of C−C coupling transformations that furnish drug‐like building blocks involves catalytic hydrocarbonation of alkenes. However, despite notable advances in the field, hydrocarbon ...addition to gem‐difluoroalkenes without additional electronic activation remains largely unsuccessful. This owes partly to poor reactivity and the propensity of difluoroalkenes to undergo defluorinative side reactions. Here, we report a nickel catalytic system that promotes efficient 1,2‐selective hydroarylation and hydroalkenylation, suppressing defluorination and providing straightforward access to a diverse assortment of prized organofluorides bearing difluoromethyl‐substituted carbon centers. In contrast to radical‐based pathways and reactions triggered by hydrometallation via a nickel‐hydride complex, our experimental and computational studies support a mechanism in which a catalytically active nickel‐bromide species promotes selective carbonickelation with difluoroalkenes followed by alkoxide exchange and hydride transfer, effectively overcoming the difluoroalkene's intrinsic electronic bias.
A sterically bulky NHC‐nickel catalyst promoted site‐selective hydroarylation(alkenylation) of gem‐difluoroalkenes by coupling with organotriflates(bromides) and sodium 1‐phenylethoxide as hydride source to furnish products containing CF2H‐substituted carbon centers. Experimental and computational studies shed light on the non‐radical mechanism and the metal alkoxide's role in facilitating the reaction.
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