Palladium-Catalyzed Atroposelective Suzuki-Miyaura Coupling to Construct Axially Chiral Tetra-Substituted α-Boryl Styrenes.

Palladium-catalyzed Suzuki-Miyaura (SM) coupling is a valuable method for forming C─C bonds, including those between aryl moieties. However, achieving atroposelective synthesis of axially chiral styrenes via SM coupling remains challenging. In this study, a palladium-catalyzed atroposelective Suzuki-Miyaura coupling between gem-diborylalkenes and aryl halides is presented. Using the monophosphine ligand Me-BI-DIME (L2), a range of axially chiral tetra-substituted acyclic styrenes with high yields and excellent enantioselectivities are successfully synthesized. Control experiments reveal that the gem-diboryl group significantly influences the product enantioselectivities and the coupling prefers to occur at sites with lower steric hindrance. Additionally, the alkenyl boronate group in the products proves versatile, allowing for various transformations while maintaining high optical purities.

Palladium-Catalyzed Defluorinative Alkylation of gem-Difluoroalkenes with Cyclopropanols: Stereoselective Synthesis of γ-Fluorinated γ,δ-Unsaturated Ketones.

A palladium-catalyzed defluorinative alkylation of gem-difluoroalkenes with cyclopropyl alcohols was developed. A range of γ-fluorinated γ,δ-unsaturated ketones were constructed in good yields with excellent stereoselectivities. In addition, by base-mediated intramolecular nucleophilic vinylic substitution (SNV), the products could be further transformed to 2,5-dimethylenetetrahydrofurans and analogues with excellent stereoselectivities.

Effects of remediation agents on rice and soil in toxic metal(loid)s contaminated paddy fields: A global meta-analysis.

Toxic metal(loid)s contamination of paddy soil is a nonnegligible issue and threatens food safety considering that it is transmitted via the soil-plant system. Applying remediation agents could effectively inhibit the soil available toxic metal(loid)s and reduce their accumulation in rice. To comprehensively quantify how remediation agents impact the accumulation of Cd/Pb/As in rice, rice growth and yield, the accumulation of available Cd/Pb/As in paddy soil, and soil characteristics, 50 peer-reviewed publications were selected for meta-analysis. Overall, the application of remediation agents exhibited significant positive effects on rice plant length (ES = 0.05, CI = 0.01-0.08), yield (ES = 0.20, CI = 0.13-0.27), peroxidase (ES = 0.56, CI = 0.18-0.31), photosynthetic rate (ES = 0.47, CI = 0.34-0.61), and respiration rate (ES = 0.68, CI = 0.47-0.88). Among the different types of remediation agents, biochar was the most effective in controlling the accumulation of Cd/Pb/As in all portions of rice, and was also superior in inhibiting the accumulation of Pb in rice grains (ES = -0.59, 95 % CI = -1.04-0.13). This study offers an essential contribution for the remediation strategies of toxic metal(loid)s contaminated paddy fields.

Atroposelective Synthesis of Axially Chiral Diaryl Ethers by N-Heterocyclic-Carbene-Catalyzed Sequentially Desymmetric/Kinetic Resolution Process.

We describe herein an N-heterocyclic-carbene-catalyzed atroposelective synthesis of axially chiral diaryl ethers. Through a sequentially enantioselective desymmetric process and a kinetic resolution process, the products could be constructed in good yields with excellent enantiopurities. Both alcohols and phenols were compatible with this catalytic system. The axially chiral carboxylic acids derived from the esters were proven to be potential chiral ligands for asymmetric synthesis, for example, Rh(III)-catalyzed enantioselective C-H functionalization.

The effects of iron-based nanomaterials (Fe NMs) on plants under stressful environments: Machine learning-assisted meta-analysis.

Mitigating the adverse effects of stressful environments on crops and promoting plant recovery in contaminated sites are critical to agricultural development and environmental remediation. Iron-based nanomaterials (Fe NMs) can be used as environmentally friendly nano-fertilizer and as a means of ecological remediation. A meta-analysis was conducted on 58 independent studies from around the world to evaluate the effects of Fe NMs on plant development and antioxidant defense systems in stressful environments. The application of Fe NMs significantly enhanced plant biomass (mean = 25%, CI = 20%-30%), while promoting antioxidant enzyme activity (mean = 14%, CI = 10%-18%) and increasing antioxidant metabolite content (mean = 10%, CI = 6%-14%), reducing plant oxidative stress (mean = -15%, CI = -20%∼-10%), and alleviating the toxic effects of stressful environments. The observed response was dependent on a number of factors, which were ranked in terms of a Random Forest Importance Analysis. Plant species was the most significant factor, followed by Fe NM particle size, duration of application, dose level, and Fe NM type. The meta-analysis has demonstrated the potential of Fe NMs in achieving sustainable agriculture and the future development of phytoremediation.

Enhanced fertilizer utilization and heavy metals immobilization by ball-milling bentonite with NH4Cl: Experiments and DFT calculations.

Over-application of nitrogen fertilizer induces soil acidification, which activates heavy metals availability and poses significant challenge to crop production and food safety. In this study, we prepared a clay-based material by ball-milling bentonite with NH4Cl (NH4Cl@bentonite) and assessed its synergistic performance in enhancing nitrogen fertilizer utilization efficiency, immobilizing heavy metals, and improving crop yield and safety. The results showed that the optimal performance of NH4Cl@bentonite was achieved by milling bentonite with NH4Cl at a 4:1 mass ratio for 9 h. NH4Cl@bentonite significantly improved soil water holding and retention capacity by 1.6 and 4.3 times, respectively. In comparison to NH4Cl alone, NH4Cl@bentonite led to a 22.3% increase in N-use efficiency and a 1.5 times enhancement in crop yield. The Pb and Cd content in water spinach shoots decreased by 55.3% and 57.5%, respectively, attributed to the transformation of heavy metals into lower bioavailability states by NH4Cl@bentonite. Experiments and Density Functional Theory (DFT) calculations indicated that NH4Cl@bentonite could immobilize Pb and Cd through processes such as cation exchange, surface adsorption, complexation, and enhancement of soil pH. This work proposes a simple and efficient method for improving cropland fertilizer utilization while ensuring healthy and sustainable development. ENVIRONMENTAL IMPLICATION: Soil acidification, caused using chemical fertilizers, especially nitrogen-based ones, threatens crop production and food safety by damaging soil structure, speeding up nutrient loss, and increasing the solubility of heavy metals. To tackle this problem, we made a clay material by mixing bentonite with NH4Cl (NH4Cl@bentonite) in a ball mill. NH4Cl@bentonite increased N-use efficiency by 22.3%, boosted crop yield by 1.5 times, and reduced the Pb and Cd levels in water spinach shoots by 55.3% and 57.5%, respectively. This work suggests a simple and effective way to enhance fertilizer use in croplands while ensuring healthy and sustainable development.

Is Cr(III) re-oxidation occurring in Cr-contaminated soils after remediation: Meta-analysis and machine learning prediction.

Whether Cr(III) in Cr(III)-containing sites formed after Cr(VI) reduction and stabilization remediation are re-oxidized and pose toxicity risks again has been a growing concern. In this study, 1030 data were collected to perform a meta-analysis to clarify the effects of various factors (oxidant type, soil and Cr(III) solid compound properties, aging conditions, and testing methods) on Cr(III) oxidation. We observed that the soil properties of clay, pH ≥ 8, the lower CEC capacity, easily reducible Mn content, and Cr(III) content, and the higher Eh value and Fe content can promote the re-oxidation of Cr(III). Publication bias and sensitivity analyses confirmed the stability and reliability of the meta-analysis. Subsequently, we used five machine learning algorithms to construct and optimize the models. The prediction results of the RF model (RMSE <1.36, R2 >0.71) with good algorithm performance showed that after ten years of remediation, the extractable Cr(VI) concentration in the soil was 0.0087 mg/L, indicating a negligible secondary pollution risk of Cr(III) re-oxidation. This study provides theoretical support for subsequent risk management and control after Cr(VI) soil remediation and provides a solution for the quantitative prediction of Cr(III) re-oxidation.

Enantioselective Synthesis of Bicyclo[3.2.1]octadienes via Palladium-Catalyzed Intramolecular Alkene-Alkyne Coupling Reaction.

Bicyclo[3.2.1]octadiene compounds and derivatives exist in a number of natural products and bioactive compounds. Nevertheless, catalytic enantioselective protocols for the synthesis of these skeletons have not been disclosed. Herein we reported a palladium-catalyzed asymmetric intramolecular alkene-alkyne coupling of alkyne-tethered cyclopentenes, affording a library of enantionenriched bicyclo[3.2.1]octadienes in excellent yields and enantioselectivities (mostly >99 % ee). Moreover, the products could undergo an unusual iodination-induced 1,2-acyl migration, forming iodinated bicyclo[3.2.1]octadienes with three vicinal stereocenters. The enone and isolated olefin motifs embedded in the products provide useful handles for downstream elaboration.

Comprehensive evaluation of the risk system for heavy metals in the rehabilitated saline-alkali land.

A comprehensive assessment of the heavy metal system in the rehabilitated saline-alkali land holds significant importance, as the in-situ remediation process utilizing amendments substantially alters the initial physicochemical properties of the soil, which could lead to the migration or reactivation of previously stabilized heavy metals. In this context, the present study aims to evaluate the heavy metal content and health risk within the improved saline-alkali soil-plant system. Moreover, a comprehensive evaluation based on the TOPSIS-RSR method is carried out to accurately gauge the soil health status. The findings indicate that the modification process has an impact on the concentrations of heavy metals in the soil and crops, causing either an increase or decrease. However, the level of heavy metal pollution in the improved saline-alkali soil and rape remains within safe limits. The results of the migration of heavy metals after amendment application indicated that the migration of heavy metals in the soil was influenced by the properties of the heavy metals, the composition of the amendment, and leaching. Furthermore, the total non-carcinogenic hazard quotients in the soil and rape were within the safe threshold for all populations. The findings provided novel insights into the status and risk assessment of the pollution of improved saline-alkali soil.

Enhanced remediation of Cr(VI)-contaminated soil by modified zero-valent iron with oxalic acid on biochar.

Hexavalent chromium (Cr(VI)) is carcinogenic and widely presented in soil. In this study, modified zero-valent iron (ZVI) with oxalic acid on biochar (OA-ZVI/BC) was prepared using wet ball milling method for the remediation of Cr(VI)-contaminated soil. Microscopic characterizations showed that ZVI were distributed on the biochar uniformly and confirmed the enhanced interface interaction between biochar and ZVI by wet ball milling. Electrochemical analysis indicated the strong electron transfer ability and enhanced corrosion behavior of OA-ZVI/BC. Moreover, inhibitory efficiencies of Cr(VI) removal with the addition of 1,10-phenanthroline suggested abundant Fe2+ generation in OA-ZVI/BC, which might facilitate the reduction of Cr(VI) to Cr(III). Theory calculation further demonstrated the ZVI modified by oxalic acid was more susceptible to solid-solid interfacial reactions with Cr(VI), and more electrons were transferred to Cr(VI). When applied to Cr(VI)-contaminated soil, OA-ZVI/BC could passivate 96.7 % total Cr(VI) and maintained for 90 days. The toxicity characteristic leaching procedure (TCLP) and simple based extraction test (SBET) were used to evaluate the leaching toxicity and bioaccessibility of Cr(VI), respectively. The TCLP-Cr(VI) decreased to 0.11 mg·L-1 after OA-ZVI/BC treatment, much lower than that of soils with ZVI/BC and OA-ZVI remediation (1.5 mg·L-1 and 4.1 mg·L-1). The bioaccessibility of Cr(VI) reduced by 93.5 % after 3-month remediation. Sequential extraction showed that Cr fractions in the soil after OA-ZVI/BC remediation was converted from acetic acid-extractable (HOAc-extractable) to more stable forms (e.g., residual and oxidizable forms). Benefiting from the synergies of oxalic acid, biochar and wet ball milling, OA-ZVI/BC exhibited an excellent performance on the remediation of Cr(VI)-contaminated soil, whose mechanisms involved adsorption, reduction (Fe0/Fe2+, Fe2+/Fe3+) and co-precipitation. This study herein develops a promising ZVI technology in the remediation of heavy metal-contaminated soil.

Copper-Catalyzed Enantioselective and Regiodivergent Allylation of Ketones with Allenylsilanes.

We report herein a regiodivergent and enantioselective allyl addition to ketones with allenylsilanes through copper catalysis. With the combination of CuOAc, a Josiphos-type bidentate phosphine ligand and PhSiH3 , allyl addition to a variety of ketones furnishes branched products in excellent enantioselectivities. The regioselectivity is completely reversed by employing the P-stereogenic ligand BenzP*, affording the linear products with excellent enantioselectivities and good Z-selectivities. The linear Z-product could be converted to E-product via a catalytic geometric isomerization of the Z-alkene group. The silyl group in the products could provide a handle for downstream elaboration.

Effective strategies for reclamation of saline-alkali soil and response mechanisms of the soil-plant system.

The combination of amendments has emerged as a potential strategy to efficiently alleviate salt stress in saline-alkali soil. However, knowledge regarding how to optimize the proportion of different amendment materials, comprehensively assess the contribution of each component, and clarify the response mechanisms of the amendment-saline-alkali soil-plant system is incomplete. Based on this, we conducted a pot experiment to evaluate the improvement effect of the combined application of different amendment materials at varying levels and the contribution of the amendment components to alleviating salt stress. Overall, T6 exhibited the most significant improvement effect on the physicochemical and biological properties of the saline-alkali soil and promoted the growth of oilseed rape, with the levels of 2.0 % phosphogypsum, 2.0 % humic acid, 0.25 % bentonite, and 0.03 % sodium carboxymethyl cellulose. Compared with the control group, the EC decreased by 1.51 % to 33.49 %, the soil salt content dropped by 11.40 % to 35.46 %, and the soil soluble Na + concentration significantly declined by 39.47 % to 63.20 %. Additionally, the soil nutrient content and soil microbial community structure were enhanced in treatment groups. Meanwhile, amendments alleviated salt stress in the oilseed rape plant by activating anti-oxidative enzymes and osmoregulatory substances such as soluble sugar and proline, thus improving their ability to remove reactive oxygen species (ROS). The anti-oxidative enzymes such as superoxide dismutase (SOD), peroxidase (POD), and catalase (CAT) were significantly increased, with an increase of 10.68 % (SOD, T2) ∼207.31 % (CAT, T6) compared to the control group. The structural equation modeling (SEM) analysis and simulation experiments indicated that the amendment components synergically promoted the amelioration effect on salt stress, and effectively improved soil properties, which affected the response of oilseed rape to soil environment. This research paper provides the relevant reference for the combined application of different amendment materials for soil reclamation.

Effects of soil amendments on Cd and As mobility in the soil-rice system and their distribution in the grain.

The accumulation, mobilization, and distribution of toxic metal(loid)s in rice are key factors that affect food security and determine bio-utilization patterns. In this study, five soil amendments with different components were used in paddy fields to study the key factors: organic amendments: (1) polyaspartic acid (OA1) and (2) organic fertilizer (OA2); inorganic amendments: (3) kaolinite (IA1) and (4) magnesium slag (IA2); and organic-inorganic composite amendments: (5) modified biochar/quicklime (OIA). Although the Cd and As exhibited opposite chemical dissolution behaviors, IA1/OIA, can simultaneously reduce their accumulation and transfer coefficients in rice tissues, while other amendments only work for one of them. The in situ distribution in grains showed that IA1/OIA changed the original Cd distribution in the lemma and palea, whereas all amendments reduced Cd accumulation in the germ. In contrast, OA1/IA2 amendments led to more As accumulation in the rice husks and bran than in the endosperm center, and the germ had higher As signals. Because of their similar transport pathways and interactions, the concentrations of Cd and As in the grains were correlated with a variety of mineral elements (Fe, Mo, Zn, etc.). Changes in the Cd/As concentration and distribution in rice were achieved through the improvement of soil properties and plant growth behavior through amendments. The application of OIA resulted in the highest immobilization indices, at 82.17 % and 35.34 % for Cd and As, respectively. The Cd/As concentrations in the rice grains were highly positively correlated with extractable-Cd/As in the soil (Cd: R2 = 0.95, As: R2 = 0.93). These findings reveal the migration and distribution mechanisms of Cd and As in the soil-rice system, and thus provide fundamental information for minimizing food safety risk.

Effects of the application of nanoscale zero-valent iron on plants: Meta analysis, mechanism, and prospects.

In order to determine the ideal conditions for the application of nanoscale zero-valent iron (nZVI) in agricultural production, this review studies the effects of nZVI application on plant physiological parameters, presents its mechanism and prospective outcomes. In this research, it was observed that the application of nZVI had both favorable and unfavorable effects on plant growth, photosynthesis, oxidative stress, and nutrient absorption levels. Specifically, the application of nZVI significantly increased the biomass and length of plants, and greatly reduced the germination rate of seeds. In terms of photosynthesis, there was no significant effect for the application of nZVI on the synthesis of photosynthetic pigments (chlorophyll and carotenoids). In terms of oxidative stress, plants respond by increasing the activity of antioxidant enzyme under mild nZVI stress and trigger oxidative burst under severe stress. In addition, the application of nZVI significantly increased the absorption of nutrients (B, K, P, S, Mg, Zn, and Fe). In summary, the application of nZVI can affect the plant physiological parameters, and the degree of influence varies depending on the concentration, preparation method, application method, particle size, and action time of nZVI. These findings are important for evaluating nZVI-related risks and enhancing nZVI safety in agricultural production.

Internal Electric Field-Modulated Charge Migration Behavior in MoS2 /MIL-53(Fe) S-Scheme Heterojunction for Boosting Visible-Light-Driven Photocatalytic Chlorinated Antibiotics Degradation.

Inadequate photo-generated charge separation, migration, and utilization efficiency limit the photocatalytic efficiency. Herein, a MoS2 /MIL-53(Fe) photocatalyst/activator with the S-scheme heterojunction structure is designed and the charge migration behavior is modulated by the internal electric field (IEF). The IEF intensity is enhanced to 40 mV by modulating band bending potential and the depletion layer length of MoS2 . The photo-generated electron migration process is boosted by constructing the electron migration bridge (Fe-O-S) and modulating the IEF as the driving force, confirmed by the density functional theory calculation. Compared with the pristine materials, the photocurrent density of MoS2 /MIL-53(Fe) is significantly enhanced 27.5 times. Contributed by the visible-light-driven cooperative catalytic degradation and the high-efficiency direct photo-generated electron reduction dichlorination process, satisfactory chlorinated antibiotics removal and detoxification performances are achieved. This study opens up new insights into the application of heterojunctions in photocatalytic activation of PDS in environmental remediation.

Atroposelective Synthesis of Axially Chiral Styrenes by Platinum- Catalyzed Stereoselective Hydrosilylation of Internal Alkynes.

Hydrofunctionalization of alkynes is one of the most efficient ways to access axially chiral styrenes with open-chained olefins. While great advances have been achieved for 1-alkynylnaphthalen-2-ols and analogues, atroposelective hydrofunctionalization of unactivated internal alkynes lags. Herein we reported a platinum-catalyzed atroposelective hydrosilylation of unactivated internal alkynes for the first time. With monodentate TADDOL-derived phosphonite L1 used as a chiral ligand, various axially chiral styrenes were achieved in excellent enantioselectivities with high E-selectivities. Control experiments showed that the NH-arylamide groups have significant effects on both the yields and enantioselectivities and could act as directing groups. The potential utilities of the products were shown by the transformations of the amide motifs of the products.

(Z)-Selective Synthesis of Bromofluoroalkenes via the TMSCF2Br-Mediated Tandem Reaction with para-Quinone Methides.

We report herein a tandem reaction of para-quinone methides with TMSCF2Br to construct bromofluoroalkenes in a Z-selective manner. While TMSCF2Br has been documented as the precursor of difluoro carbene, it exhibits another possibility in this transformation, a formal bromofluoro carbene surrogate. The alkenyl bromide unit of the products could directly engage in a variety of transformations.

Metagenomic insights into the inhibitory mechanisms of Cu on fermentative hydrogen production.

Cu is widely present in the feedstocks of dark fermentation, which can inhibit H2 production efficiency of the process. However, current understanding on the inhibitory mechanisms of Cu, especially the microbiological mechanism, is still lacking. This study investigated the inhibitory mechanisms of Cu2+ on fermentative hydrogen production by metagenomics sequencing. Results showed that the exposure to Cu2+ reduced the abundances of high-yielding hydrogen-producing genera (e.g. Clostridium sensu stricto), and remarkably down-regulated the genes involved in substrate membrane transport (e.g., gtsA, gtsB and gtsC), glycolysis (e.g. PK, ppgK and pgi-pmi), and hydrogen formation (e.g. pflA, fdoG, por and E1.12.7.2), leading to significant inhibition on the process performances. The H2 yield was reduced from 1.49 mol H2/mol-glucose to 0.59 and 0.05 mol H2/mol-glucose upon exposure to 500 and 1000 mg/L of Cu2+, respectively. High concentrations of Cu2+ also reduced the rate of H2 production and prolonged the H2-producing lag phase.

Construction of oxygenated 2-azabicyclo[2.2.1]heptanes via palladium-catalyzed 1,2-aminoacyloxylation of cyclopentenes.

Herein, we describe a palladium-catalyzed 1,2-aminoacyloxylation of cyclopentenes to synthesize oxygenated 2-azabicyclo[2.2.1]heptanes. This reaction proceeds efficiently with a broad array of substrates. The products could be further functionalized to build up a library of bridged aza-bicyclic structures.

Arsenic removal and stabilization behavior of schwertmannite@BC (Sch@BC) in contaminated dual media (water/soil): Via sulfate exchange and chemical complexation.

Arsenic (As) is extremely harmful to the ecological environment and human health owing to its high toxicity. The composite that biochar (BC) modified by Schwertmannite (Sch), marked as Sch@BC, were prepared to remediate As-contaminated water and soil with a high efficiency. The characterization results showed that the Sch particles were successfully loaded on the BC, providing more active sites for As(V) adsorption. Compared with the pristine BC, the adsorption capacity of Sch@BC-1 was significantly improved (50.00 mg/g), of which the adsorption capacity kept stable over a wide pH range (pH = 2-8). The adsorption process conformed to pseudo-second-order kinetics and Langmuir isotherm model, which indicated that chemical adsorption was the dominant mechanism and the adsorption rate was controlled by intraparticle diffusion. Sch@BC could adsorb As(V) through electrostatic interaction and ion exchange, forming a FeAsO4 complex and removing As(V). The 5-week soil incubation experiment showed that 3% Sch@BC showed the optimal stabilization effect, while the proportion of stable crystalline Fe/Mn-bound fractionation (F4) increased. Moreover, the results of microbial community diversity showed that Sch@BC interacted with As-resistant dominant microorganisms such as Proteobacteria in soil, promoted their growth and reproduction, and improved the stability of As in soil. In summary, Sch@BC is an excellent agent with broad application prospects for remediating As-contaminated water and soil.