Valve turning towards on-cycle in cobalt-catalyzed Negishi-type cross-coupling.

Ligands and additives are often utilized to stabilize low-valent catalytic metal species experimentally, while their role in suppressing metal deposition has been less studied. Herein, an on-cycle mechanism is reported for CoCl2bpy2 catalyzed Negishi-type cross-coupling. A full catalytic cycle of this kind of reaction was elucidated by multiple spectroscopic studies. The solvent and ligand were found to be essential for the generation of catalytic active Co(I) species, among which acetonitrile and bipyridine ligand are resistant to the disproportionation events of Co(I). Investigations, based on Quick-X-Ray Absorption Fine Structure (Q-XAFS) spectroscopy, Electron Paramagnetic Resonance (EPR), IR allied with DFT calculations, allow comprehensive mechanistic insights that establish the structural information of the catalytic active cobalt species along with the whole catalytic Co(I)/Co(III) cycle. Moreover, the acetonitrile and bipyridine system can be further extended to the acylation, allylation, and benzylation of aryl zinc reagents, which present a broad substrate scope with a catalytic amount of Co salt. Overall, this work provides a basic mechanistic perspective for designing cobalt-catalyzed cross-coupling reactions.

Enhancement of the Desorption Properties of LiAlH4 by the Addition of LaCoO3.

The high hydrogen storage capacity (10.5 wt.%) and release of hydrogen at a moderate temperature make LiAlH4 an appealing material for hydrogen storage. However, LiAlH4 suffers from slow kinetics and irreversibility. Hence, LaCoO3 was selected as an additive to defeat the slow kinetics problems of LiAlH4. For the irreversibility part, it still required high pressure to absorb hydrogen. Thus, this study focused on the reduction of the onset desorption temperature and the quickening of the desorption kinetics of LiAlH4. Here, we report the different weight percentages of LaCoO3 mixed with LiAlH4 using the ball-milling method. Interestingly, the addition of 10 wt.% of LaCoO3 resulted in a decrease in the desorption temperature to 70 °C for the first stage and 156 °C for the second stage. In addition, at 90 °C, LiAlH4 + 10 wt.% LaCoO3 can desorb 3.37 wt.% of H2 in 80 min, which is 10 times faster than the unsubstituted samples. The activation energies values for this composite are greatly reduced to 71 kJ/mol for the first stages and 95 kJ/mol for the second stages compared to milled LiAlH4 (107 kJ/mol and 120 kJ/mol for the first two stages, respectively). The enhancement of hydrogen desorption kinetics of LiAlH4 is attributed to the in situ formation of AlCo and La or La-containing species in the presence of LaCoO3, which resulted in a reduction of the onset desorption temperature and activation energies of LiAlH4.

Investigation of physical properties and carbon dioxide solubility in tetramethylammonium bromide and tetraethylammonium bromide ionic liquids solutions.

Carbon dioxide is a major greenhouse gas that is responsible for global warming and renders harmful effects on the atmosphere. The unconstrained release of CO2 into the atmosphere should be prevented and various techniques have been developed in this regard to capture CO2 using different solvents and other compounds. Ionic liquids are a suitable candidate to capture CO2 due to their better solubility behaviour. In this work, two ionic liquids namely tetramethylammonium bromide (TMAB) and tetraethylammonium bromide (TEAB) are employed experimentally to capture CO2 and investigate their solubility behaviour. The study is performed at the temperature values of 303 K, 313 K, and 323 K and the pressure values of 5, 10, 15, and 20 bar equivalent to 0.5, 1.0, 1.5, and 2.0 MPa respectively. The concentrations of both ionic liquid solutions are 2.5 wt%, 5.0 wt%, and 10.0 wt%. The solubility results are considered in terms of mol fraction which is the ratio of moles of CO2 captured per moles of ionic liquid. The density and viscosity values are also determined for both compounds at respective conditions. COSMO-RS is used to generate the sigma profile, sigma surface, and Henry's constant of the ions involved in the study. CO2 is found to be soluble in both ionic liquids, but TEAB showed better solubility behaviour as compared to TMAB. The solubility of CO2 is found to be increasing with the increase in pressure while it decreases with the increase in temperature.

Electrochemical oxidative difunctionalization of diazo compounds with two different nucleophiles.

With the fast development of synthetic chemistry, the introduction of functional group into organic molecules has attracted increasing attention. In these reactions, the difunctionalization of unsaturated bonds, traditionally with one nucleophile and one electrophile, is a powerful strategy for the chemical synthesis. In this work, we develop a different path of electrochemical oxidative difunctionalization of diazo compounds with two different nucleophiles. Under metal-free and external oxidant-free conditions, a series of structurally diverse heteroatom-containing compounds hardly synthesized by traditional methods (such as high-value alkoxy-substituted phenylthioacetates, α-thio, α-amino acid derivatives as well as α-amino, ß-amino acid derivatives) are obtained in synthetically useful yields. In addition, the procedure exhibits mild reaction conditions, excellent functional-group tolerance and good efficiency on large-scale synthesis. Importantly, the protocol is also amenable to the key intermediate of bioactive molecules in a simple and practical process.

Effect of LaCoO3 Synthesized via Solid-State Method on the Hydrogen Storage Properties of MgH2.

One of the ideal energy carriers for the future is hydrogen. It has a high energy density and is a source of clean energy. A crucial step in the development of the hydrogen economy is the safety and affordable storage of a large amount of hydrogen. Thus, owing to its large storage capacity, good reversibility, and low cost, Magnesium hydride (MgH2) was taken into consideration. Unfortunately, MgH2 has a high desorption temperature and slow ab/desorption kinetics. Using the ball milling technique, adding cobalt lanthanum oxide (LaCoO3) to MgH2 improves its hydrogen storage performance. The results show that adding 10 wt.% LaCoO3 relatively lowers the starting hydrogen release, compared with pure MgH2 and milled MgH2. On the other hand, faster ab/desorption after the introduction of 10 wt.% LaCoO3 could be observed when compared with milled MgH2 under the same circumstances. Besides this, the apparent activation energy for MgH2-10 wt.% LaCoO3 was greatly reduced when compared with that of milled MgH2. From the X-ray diffraction analysis, it could be shown that in-situ forms of MgO, CoO, and La2O3, produced from the reactions between MgH2 and LaCoO3, play a vital role in enhancing the properties of hydrogen storage of MgH2.

Physicochemical approaches reveal the impact of electrolytes and hydrotropic salt on micellization and phase separation behavior of polymer polyvinyl alcohol and surfactant mixture.

The polymer-surfactant mixture has usages in numerous industries mainly in the production of daily used materials. Herein, the micellization and phase separation nature of the sodium dodecyl sulfate (SDS) and TX-100 along with a synthetic water-soluble polymer-polyvinyl alcohol (PVA) have been conducted using conductivity and cloud point (CP) measurement tools. In the case of micellization study of SDS + PVA mixture by conductivity method, the CMC values were obtained to be dependent on the categories and extent of additives as well as temperature variation. Both categories of studies were performed in aq. solutions of sodium chloride (NaCl), sodium acetate (NaOAc), and sodium benzoate (NaBenz) media. The CP values of TX 100 + PVA were decreased and enhanced in simple electrolytes and sodium benzoate media respectively. In all cases, the free energy changes of micellization (∆Gm0) and clouding (∆Gc0) were obtained as negative and positive respectively. The enthalpy (∆Hm0) and entropy (∆Sm0) changes for SDS + PVA system micellization was negative and positive respectively in aq. NaCl and NaBenz media, and in aq. NaOAc medium the ∆Hm0 values were found negative while ∆Sm0 were found negative except at the highest studied temperature (323.15 K). The enthalpy-entropy compensation of both processes was also assessed and described clearly.

Advanced Energy Management Strategy of Photovoltaic/PEMFC/Lithium-Ion Batteries/Supercapacitors Hybrid Renewable Power System Using White Shark Optimizer.

The slow dynamic response of a proton exchange membrane fuel cell (PEMFC) to high load change during deficit periods must be considered. Therefore, integrating the hybrid system with energy storage devices like battery storage and/or a supercapacitor is necessary. To reduce the consumed hydrogen, an energy management strategy (EMS) based on the white shark optimizer (WSO) for photovoltaic/PEMFC/lithium-ion batteries/supercapacitors microgrid has been developed. The EMSs distribute the load demand among the photovoltaic, PEMFC, lithium-ion batteries, and supercapacitors. The design of EMSs must be such that it minimizes the use of hydrogen while simultaneously ensuring that each energy source performs inside its own parameters. The recommended EMS-based-WSO was evaluated in regard to other EMSs regarding hydrogen fuel consumption and effectiveness. The considered EMSs are state machine control strategy (SMCS), classical external energy maximization strategy (EEMS), and optimized EEMS-based particle swarm optimization (PSO). Thanks to the proposed EEMS-based WSO, hydrogen utilization has been reduced by 34.17%, 29.47%, and 2.1%, respectively, compared with SMCS, EEMS, and PSO. In addition, the efficiency increased by 6.05%, 9.5%, and 0.33%, respectively, compared with SMCS, EEMS, and PSO.

Electrochemical radical-mediated selective C(sp3)-S bond activation.

Selective C(sp3)-S bond breaking and transformation remains a particularly important, yet challenging goal in synthetic chemistry. Over the past few decades, transition metal-catalyzed cross-coupling reactions through the cleavage of C(sp3)-S bonds provided a powerful platform for the construction of target molecules. In contrast, the selective activation of widespread C(sp3)-S bonds is rarely studied and remains underdeveloped, even under relatively harsh conditions. Herein, a radical-mediated electrochemical strategy capable of selectively activating C(sp3)-S bonds is disclosed, offering an unprecedented method for the synthesis of valuable disulfides from widespread thioethers. Importantly, compared with conventional transition-metal catalyzed C-S bond breaking protocols, this method features mild, catalyst- and oxidant-free reaction conditions, as well excellent chemoselectivity towards C(sp3)-S bonds. Preliminary mechanistic studies reveal that sulfur radical species are involved in the reaction pathway and play an essential role in controlling the site-selectivity.

Learning Smooth Representation for Unsupervised Domain Adaptation.

Typical adversarial-training-based unsupervised domain adaptation (UDA) methods are vulnerable when the source and target datasets are highly complex or exhibit a large discrepancy between their data distributions. Recently, several Lipschitz-constraint-based methods have been explored. The satisfaction of Lipschitz continuity guarantees a remarkable performance on a target domain. However, they lack a mathematical analysis of why a Lipschitz constraint is beneficial to UDA and usually perform poorly on large-scale datasets. In this article, we take the principle of utilizing a Lipschitz constraint further by discussing how it affects the error bound of UDA. A connection between them is built, and an illustration of how Lipschitzness reduces the error bound is presented. A local smooth discrepancy is defined to measure the Lipschitzness of a target distribution in a pointwise way. When constructing a deep end-to-end model, to ensure the effectiveness and stability of UDA, three critical factors are considered in our proposed optimization strategy, i.e., the sample amount of a target domain, dimension, and batchsize of samples. Experimental results demonstrate that our model performs well on several standard benchmarks. Our ablation study shows that the sample amount of a target domain, the dimension, and batchsize of samples, indeed, greatly impact Lipschitz-constraint-based methods' ability to handle large-scale datasets. Code is available at https://github.com/CuthbertCai/SRDA.

Prediction of carbon-dioxide activity coefficient for solubility in ionic liquids using multi-non-linear regression analysis.

Activity coefficient values offer insight into the intermolecular interactions between the solute and the solvent and the deviation from the ideal behavior. CO2 capture from different industrial processes is a globally pertinent issue and the search for suitable chemicals is required. To address the issue, knowledge of activity coefficient values is crucial for CO2 separation-based process. In this regard, a correlation is developed that predicts the coefficient of CO2 activity in ionic liquids by multi-nonlinear regression analysis. The correlation is developed between the pressure range of 1-50 bar and the temperature range of 298.15-33.15 K for mole fractions of 0.3, 0.5, and 0.7. Outliers' analysis is performed using the boxplot method to determine the suitability of ranges of the selected input parameters. The preceding literature does not predict the activity coefficient in relatively lower to higher temperature and pressure ranges for CO2 solubility in ionic liquids. Initially, the activity coefficient values from COSMO-RS were obtained and compared with the correlation results. The COSMO-RS and the correlation predicted results were subsequently validated with the experimental data. The average absolute error (AAE%) of the predicted correlation values is 19.53% while the root mean square error (RMSE) value is 0.465. The correlation can be used in the future to predict the CO2 activity coefficient values in ionic liquids to facilitate qualitative analyses of their CO2 capture efficiency.

Enzyme-Assisted Extraction of Phenolics from Capparis spinosa Fruit: Modeling and Optimization of the Process by RSM and ANN.

The current study intends to appraise the effect of enzyme complexes on the recovery of phenolics from Capparis spinosa fruit extract using the response surface methodology (RSM) and artificial neural networking (ANN). Enzymatic treatment of C. spinosa fruit extract was optimized under a set of conditions (enzyme concentration, pH, temperature, and time) against each enzyme formulation such as Kemzyme Plus Dry, Natuzyme, and Zympex-014. The extract yield observed for Kemzyme Plus Dry (42.00%) was noted to be higher than those for Zympex-014 (39.80%) and Natuzyme (38.50%). Based on the higher results, the values of Kemzyme Plus Dry-based extract were further employed in different parameters of RSM. The F-value (16.03) and p-values (<0.05) implied that the selected model is significant. Similarly, the higher values for the coefficient of determination (R 2) at 0.9740 and adjusted R 2 (adj. R 2) at 0.9132 indicated that the model is significant in relation to given experimental parameters. ANN-predicted values were very close to the experimental values, which demonstrated the applicability of the ANN model. Antioxidant activities also exhibited profound results in terms of total phenolic content values (24.76 mg GAE/g), total flavonoid content values (24.56 mg CE/g), and the 2,2-diphenyl-1-picrylhydrazyl (DPPH) assay (IC50) (5.12 mg/mL). Scanning electron microscopy revealed that after enzymatic hydrolysis, the cell walls were broken as compared with nonhydrolyzed materials. Five phenolics, namely, quercetin, m-coumaric acid, sinapic acid, kaempferol, and p-coumaric acid, were identified from C. spinosa extract by gas chromatography-mass spectrometry (GC/MS). The results of this study reveal that the proposed optimization techniques, using Kemzyme Plus Dry among others, had a positive effect on the recovery of phenolic bioactive compounds and thus increased the antioxidant potential of C. spinosa fruit extract.

Electrochemical oxidative N-H/P-H cross-coupling with H2 evolution towards the synthesis of tertiary phosphines.

Tertiary phosphines(iii) find widespread use in many aspects of synthetic organic chemistry. Herein, we developed a facile and novel electrochemical oxidative N-H/P-H cross-coupling method, leading to a series of expected tertiary phosphines(iii) under mild conditions with excellent yields. It is worth noting that this electrochemical protocol features very good reaction selectivity, where only a 1 : 1 ratio of amine and phosphine was required in the reaction. Moreover, this electrochemical protocol proved to be practical and scalable. Mechanistic insights suggested that the P radical was involved in this reaction.

Paired electrolysis enabled annulation for the quinolyl-modification of bioactive molecules.

A paired electrolysis enabled cascade annulation that enables the efficient synthesis of highly functionalized quinoline-substituted bioactive molecules from readily available starting materials is reported. Using this methodology, two goals, namely, the direct synthesis of quinolines and the introduction of quinoline moieties to bioactive molecules, can be simultaneously achieved in one simple operation. The use of electroreduction for the activation of isatin, together with the further anodic oxidation of KI to catalytically result in a cascade annulation, highlight the unique possibilities associated with electrochemical activation methods. This transformation can tolerate a wide range of functional groups and can also be used as a functionalization tactic in pharmaceutical research as well as other areas.

Synthesis of 1H-indazoles by an electrochemical radical Csp2-H/N-H cyclization of arylhydrazones.

The development of efficient and sustainable C-N bond-forming reactions to N-heterocyclic frameworks has been a long-standing interest in organic synthesis. In this work, we develop an electrochemical radical Csp2-H/N-H cyclization of arylhydrazones to 1H-indazoles. The electrochemical anodic oxidation approach was adopted to synthesize a variety of 1H-indazole derivatives in moderate to good yields. HFIP was not only employed as a solvent or the proton donor, but also can promote the formation of N free radicals. This synthetic methodology is operationally simple, and less expensive electrodes would be suitable for this chemistry.

Biological and Hypoglycemic Effects of a Polyherbal Extract on Alloxanized Diabetic Rats.

The current study investigates the antioxidant, antidiabetic, hepatoprotective, and nephroprotective potentials of a polyherbal mixture containing the methanolic extracts of seeds from Nigella sativa, Cicer arietinum, Silybum marianum, and Citrullus colocynthis and the rhizome of Zingiber officinale. The polyherbal extract (PHE) showed significant total phenolic contents (187.17 GAE/g), ferric reducing power (28%), and radical-scavenging activity (86.16%). The PHE also showed a substantial hypoglycemic effect in alloxan-induced diabetic rats by reducing the blood glucose level of the PHE-treated rats (-48.64%) and increasing the insulin level (107.5%) as compared with the diabetic control group. Likewise, an increase in high-density lipoprotein (HDL) contents (22.95%) with an associated decrease in low-density lipoprotein (LDL) levels (-43.93%) was also noted. A significant decrease in serum levels of liver marker enzymes, e.g., SGPT (-36%), SGOT (-31%), and serum ALP (-12%), was also observed as compared with the standard drug-treated group. Based on the findings of the study, it may be suggested that PHE helps ameliorate the severity of diabetes as a herbal remedy and might be employed in nutra-pharmaceuticals, replacing synthetic antidiabetic compounds.

Catalytic Fast Pyrolysis of Soybean Straw Biomass for Glycolaldehyde-Rich Bio-oil Production and Subsequent Extraction.

In this study, soybean straw (SS) as a promising source of glycolaldehyde-rich bio-oil production and extraction was investigated. Proximate and ultimate analysis of SS was performed to examine the feasibility and suitability of SS for thermochemical conversion design. The effect of the co-catalyst (CaCl2 + ash) on glycolaldehyde concentration (%) was examined. Thermogravimetric-Fourier-transform infrared (TG-FTIR) analysis was applied to optimize the pyrolysis temperature and biomass-to-catalyst ratio for glycolaldehyde-rich bio-oil production. By TG-FTIR analysis, the highest glycolaldehyde concentration of 8.57% was obtained at 500 °C without the catalyst, while 12.76 and 13.56% were obtained with the catalyst at 500 °C for a 1:6 ratio of SS-to-CaCl2 and a 1:4 ratio of SS-to-ash, respectively. Meanwhile, the highest glycolaldehyde concentrations (%) determined by gas chromatography-mass spectrometry (GC-MS) analysis for bio-oils produced at 500 °C (without the catalyst), a 1:6 ratio of SS-to-CaCl2, and a 1:4 ratio of SS-to-ash were found to be 11.3, 17.1, and 16.8%, respectively. These outcomes were fully consistent with the TG-FTIR results. Moreover, the effect of temperature on product distribution was investigated, and the highest bio-oil yield was achieved at 500 °C as 56.1%. This research work aims to develop an environment-friendly extraction technique involving aqueous-based imitation for glycolaldehyde extraction with 23.6% yield. Meanwhile, proton nuclear magnetic resonance (1H NMR) analysis was used to confirm the purity of the extracted glycolaldehyde, which was found as 91%.

Time-Resolved EPR Revealed the Formation, Structure, and Reactivity of N-Centered Radicals in an Electrochemical C(sp3)-H Arylation Reaction.

Electrochemical synthesis has been rapidly developed over the past few years, while a vast majority of the reactions proceed through a radical pathway. Understanding the properties of radical intermediates is crucial in the mechanistic study of electrochemical transformations and will be beneficial for developing new reactions. Nevertheless, it is rather difficult to determine the "live" radical intermediates due to their high reactivity. In this work, the formation and structure of sulfonamide N-centered radicals have been researched directly by using the time-resolved electron paramagnetic resonance (EPR) technique under electrochemical conditions. Supported by the EPR results, the reactivity of N-centered radicals as a mediator in the hydrogen atom transfer (HAT) approach has been discussed. Subsequently, these mechanistic study results have been successfully utilized in the discovery of an unactivated C(sp3)-H arylation reaction. The kinetic experiments have revealed the rate-determined step is the anodic oxidation of sulfonamides.

Electrochemically selective double C(sp2)-X (X = S/Se, N) bond formation of isocyanides.

The construction of C(sp2)-X (X = B, N, O, Si, P, S, Se, etc.) bonds has drawn growing attention since heteroatomic compounds play a prominent role from biological to pharmaceutical sciences. The current study demonstrates the C(sp2)-S/Se and C(sp2)-N bond formation of one carbon of isocyanides with thiophenols or disulfides or diselenides and azazoles simultaneously. The reported findings could provide access to novel multiple isothioureas, especially hitherto rarely reported selenoureas. The protocol showed good atom-economy and step-economy with only hydrogen evolution and theoretical calculations accounted for the stereoselectivity of the products. Importantly, the electrochemical reaction could exclusively occur at the isocyano part regardless of the presence of susceptible radical acceptors, such as a broad range of arenes and alkynyl moieties, even alkenyl moieties.

Electrochemical Radical Selenylation of Alkenes and Arenes via Se-Se Bond Activation.

A novel electrochemical radical selenylation of alkenes and activated arenes without external oxidants is reported. The diselenide was fully transformed into Se-centered radicals through electrochemical Se-Se bond activation. Three-component radical carbonselenation was successfully realized using styrenes to trap the RSe radical. Besides, the direct coupling of RSe radicals with activated arenes was further developed. Using this atom-economic protocol, diversity of unsymmetric aryl-aryl, aryl-alkyl, and alkyl-alkyl selenoethers was obtained regioselectively, which has potential application in biological chemistry.