A unified strategy for intermolecular remote C(sp3)–H and C–C vinylation of O-acyl oximes with vinyl boronic acids has been achieved. This strategy is enabled by photoreductive generation of iminyl ...radicals from O-acyl oximes under irradiation by visible light. The translocated carbon-centered radicals, which are generated from the iminyl radicals through 1,5-hydrogen atom transfer or C–C cleavage, can be vinylated with vinyl boronic acids. This strategy opens up a new approach to remote functionalization via C(sp3)–H and C–C cleavage and provides an efficient and versatile solution to the synthesis of γ-vinylation of ketones and nitriles.
IMPORTANCE: The increased social and economic burdens for osteoporosis-related fractures worldwide make the prevention of such injuries a major public health goal. Previous studies have reached mixed ...conclusions regarding the association between calcium, vitamin D, or combined calcium and vitamin D supplements and fracture incidence in older adults. OBJECTIVE: To investigate whether calcium, vitamin D, or combined calcium and vitamin D supplements are associated with a lower fracture incidence in community-dwelling older adults. DATA SOURCES: The PubMed, Cochrane library, and EMBASE databases were systematically searched from the inception dates to December 24, 2016, using the keywords calcium, vitamin D, and fracture to identify systematic reviews or meta-analyses. The primary randomized clinical trials included in systematic reviews or meta-analyses were identified, and an additional search for recently published randomized trials was performed from July 16, 2012, to July 16, 2017. STUDY SELECTION: Randomized clinical trials comparing calcium, vitamin D, or combined calcium and vitamin D supplements with a placebo or no treatment for fracture incidence in community-dwelling adults older than 50 years. DATA EXTRACTION AND SYNTHESIS: Two independent reviewers performed the data extraction and assessed study quality. A meta-analysis was performed to calculate risk ratios (RRs), absolute risk differences (ARDs), and 95% CIs using random-effects models. MAIN OUTCOMES AND MEASURES: Hip fracture was defined as the primary outcome. Secondary outcomes were nonvertebral fracture, vertebral fracture, and total fracture. RESULTS: A total of 33 randomized trials involving 51 145 participants fulfilled the inclusion criteria. There was no significant association of calcium or vitamin D with risk of hip fracture compared with placebo or no treatment (calcium: RR, 1.53 95% CI, 0.97 to 2.42; ARD, 0.01 95% CI, 0.00 to 0.01; vitamin D: RR, 1.21 95% CI, 0.99 to 1.47; ARD, 0.00 95% CI, −0.00 to 0.01. There was no significant association of combined calcium and vitamin D with hip fracture compared with placebo or no treatment (RR, 1.09 95% CI, 0.85 to 1.39; ARD, 0.00 95% CI, −0.00 to 0.00). No significant associations were found between calcium, vitamin D, or combined calcium and vitamin D supplements and the incidence of nonvertebral, vertebral, or total fractures. Subgroup analyses showed that these results were generally consistent regardless of the calcium or vitamin D dose, sex, fracture history, dietary calcium intake, and baseline serum 25-hydroxyvitamin D concentration. CONCLUSIONS AND RELEVANCE: In this meta-analysis of randomized clinical trials, the use of supplements that included calcium, vitamin D, or both compared with placebo or no treatment was not associated with a lower risk of fractures among community-dwelling older adults. These findings do not support the routine use of these supplements in community-dwelling older people.
Anticancer agents are critical for the cancer treatment, but side effects and the drug resistance associated with the currently used anticancer agents create an urgent need to explore novel drugs ...with low side effects and high efficacy. 1,2,3-Triazole is privileged building block in the discovery of new anticancer agents, and some of its derivatives have already been applied in clinics or under clinical trials for fighting against cancers. Hybrid molecules occupy an important position in cancer control, and hybridization of 1,2,3-triazole framework with other anticancer pharmacophores may provide valuable therapeutic intervention for the treatment of cancer, especially drug-resistant cancer. This review emphasizes the recent advances in 1,2,3-triazole-containing hybrids with anticancer potential, covering articles published between 2015 and 2019, and the structure-activity relationships, together with mechanisms of action are also discussed.
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•1,2,3-Triazole drugs have already been used in clinics for cancer treatment.•1,2,3-Triazole-containing hybrids with potential anticancer activity.•The SAR was enriched.
The organocatalytic asymmetric arylative dearomatization of indoles was achieved through two tandem approaches involving 2,3‐disubstituted indoles and quinone imine ketals. One approach utilized the ...enantioselective cascade 1,4 addition/alcohol elimination reaction, the other employed the one‐pot tandem arylative dearomatization/transfer hydrogenation sequence. In both cases, enantiomerically pure indole derivatives that bear an all‐carbon quaternary stereogenic center were generated in high yields and excellent stereoselectivities (all d.r.>95:5, up to 99 % ee).
Less aromatic: The title reaction between indoles and quinone imine ketals was achieved by the two tandem approaches shown in the scheme. In both cases, enantiomerically pure indole derivatives bearing an all‐carbon quaternary stereogenic center were generated in high yields and excellent stereoselectivities.
Metal–organic frameworks (MOFs) with carboxylate ligands as co‐catalysts are very efficient for the oxygen evolution reaction (OER). However, the role of local adsorbed carboxylate ligands around the ...in‐situ‐transformed metal (oxy)hydroxides during OER is often overlooked. We reveal the extraordinary role and mechanism of surface‐adsorbed carboxylate ligands on bi/trimetallic layered double hydroxides (LDHs)/MOFs for OER electrocatalytic activity enhancement. The results of X‐ray photoelectron spectroscopy (XPS), synchrotron X‐ray absorption spectroscopy, and density functional theory (DFT) calculations show that the carboxylic groups around metal (oxy)hydroxides can efficiently induce interfacial electron redistribution, facilitate an abundant high‐valence state of nickel species with a partially distorted octahedral structure, and optimize the d‐band center together with the beneficial Gibbs free energy of the intermediate. Furthermore, the results of in situ Raman and FTIR spectra reveal that the surface‐adsorbed carboxylate ligands as Lewis base can promote sluggish OER kinetics by accelerating proton transfer and facilitating adsorption, activation, and dissociation of hydroxyl ions (OH−).
In the oxygen evolution reaction (OER), surface‐adsorbed carboxylate ligands on bi/trimetallic layered double hydroxides (LDHs)/MOFs demonstrate a synergistic effect. As a Lewis base the carboxylate ligands promote the sluggish OER by accelerating proton transfer and facilitating adsorption, activation, and dissociation of OH− ions, while also facilitating intrinsic electron redistribution and a partially distorted octahedral structure.
The integration of Fe dopant and interfacial FeOOH into Ni‐MOFs Fe‐doped‐(Ni‐MOFs)/FeOOH to construct Fe−O−Ni−O−Fe bonding is demonstrated and the origin of remarkable electrocatalytic performance of ...Ni‐MOFs is elucidated. X‐ray absorption/photoelectron spectroscopy and theoretical calculation results indicate that Fe‐O−Ni−O−Fe bonding can facilitate the distorted coordinated structure of the Ni site with a short nickel–oxygen bond and low coordination number, and can promote the redistribution of Ni/Fe charge density to efficiently regulate the adsorption behavior of key intermediates with a near‐optimal d‐band center. Here the Fe‐doped‐(Ni‐MOFs)/FeOOH with interfacial Fe−O−Ni−O−Fe bonding shows superior catalytic performance for OER with a low overpotential of 210 mV at 15 mA cm−2 and excellent stability with ≈3 % attenuation after a 120 h cycle test. This study provides a novel strategy to design high‐performance Ni/Fe‐based electrocatalysts for OER in alkaline media.
Iron doping and FeOOH decorating leads to interfacial Fe−O−Ni−O−Fe bonding in Fe‐doped‐(Ni‐MOF)/FeOOH. This interfacial bonding can regulate the active Ni site to give the appropriate adsorption behavior of intermediates for the oxygen evolution reaction (OER). As a result, Fe‐doped‐(Ni‐MOF)/FeOOH shows outstanding catalytic performance with low overpotential, small Tafel slope, and high durability.
The first catalytic asymmetric inverse‐electron‐demand (IED) oxa‐Diels–Alder reaction of ortho‐quinone methides, generated in situ from ortho‐hydroxybenzyl alcohols, has been established. By ...selecting 3‐methyl‐2‐vinylindoles as a class of competent dienophiles, this approach provides an efficient strategy to construct an enantioenriched chroman framework with three adjacent stereogenic centers in high yields and excellent stereoselectivities (up to 99 % yield, >95:5 d.r., 99.5:0.5 e.r.). The utilization of ortho‐hydroxybenzyl alcohols as precursors of dienes and 3‐methyl‐2‐vinylindoles as dienophiles, as well as the hydrogen‐bonding activation mode of the substrates met the challenges of a catalytic asymmetric IED oxa‐Diels–Alder reaction.
Three in a row: The title reaction of ortho‐quinone methides, generated in situ from ortho‐hydroxybenzyl alcohols, has been established. By selecting 3‐methyl‐2‐vinylindoles as a class of competent dienophiles, this approach provides an efficient strategy to construct enantioenriched chroman frameworks with three adjacent stereogenic centers in high yields and excellent stereoselectivities. CPA=chiral phosphoric acid.
•The level of synergy of territorial spatial functions (PLEFs) in the Yangtze River Economic Belt (YREB) to a high level of development.•There was significant spatial variation in the role of factors ...influencing PLEFs.•Classified into three main functional dominant zones and six sub-type zones.•Proposed a differentiated optimization strategy for the YREB.
The high-quality development of the Yangtze River Economic Belt (YREB) is a major strategy related to China’s overall national development. Based on the synergy/trade-offs of production, living, and ecological functions (PLEFs) in the YREB from 2000 to 2020, this paper puts forward suggestions for the optimization of territorial space to promote the high-quality development of the YREB. The mechanistic equilibrium model was applied to determine the synergy/trade-off relationship of PLEFs, and the key factors affecting the coordination degree were analyzed with the help of a geographical detector and a geographically weighted regression (GWR) model to further identify the trade-off zones and propose differential optimization strategies. The results showed that the average degree of synergy of PLEFs decreased from 0.18 to 0.08 in YREB during the study period, and the coordination developed to a higher level, forming a local patchwork of coordination “highlands” in space, with a gradient divergence of coordination from west to east. The land-use degree, landscape, slope, traffic, and nightlight index were the dominant factors influencing PLEFs, and their q-values were 0.30, 0.27, 0.20, 0.18 and 0.14 in order, with significant spatial differences in the effects of each factor’s role. Based on the deviation of the coordination degree of PLEFs, three major function-dominated zones were divided, and it was found that the YREB showed an evolutionary trend of ecological function domination (2000) to production function domination (2010) to ecological function domination (2020). The trade-off zones in antagonistic and dysregulated states were further identified, and the study proposed targeted optimization strategies. The findings provide theoretical reference to promote the sustainable use of territorial resources and high-quality regional development in the YREB and the rest of the country.
Lignocellulosic biomass is an abundant organic material that can be used for sustainable production of bioenergy and biofuels such as biogas (about 50–75% CH4 and 25–50% CO2). Out of all ...bioconversion technologies for biofuel and bioenergy production, anaerobic digestion (AD) is a most cost-effective bioconversion technology that has been implemented worldwide for commercial production of electricity, heat, and compressed natural gas (CNG) from organic materials. However, the utilization of lignocellulosic biomass for biogas production via anaerobic digestion has not been widely adopted because the complicated structure of the plant cell wall makes it resistant to microbial attack. Pretreatment of recalcitrant lignocellulosic biomass is essential to achieve high biogas yield in the AD process. A number of different pretreatment techniques involving physical, chemical, and biological approaches have been investigated over the past few decades, but there is no report that systematically compares the performance of these pretreatment methods for application on lignocellulosic biomass for biogas production. This paper reviews the methods that have been studied for pretreatment of lignocellulosic biomass for conversion to biogas. It describes the AD process, structural and compositional properties of lignocellulosic biomass, and various pretreatment techniques, including the pretreatment process, parameters, performance, and advantages vs. drawbacks. This paper concludes with the current status and future research perspectives of pretreatment.
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