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•Antiobiotics adsorption on carbon-based materials was modeled by machine learning.•Random forest showed best prediction accuracy than GBT and ANN.•SBET , pHsol, C0 were critical ...factors for TC (74%) and SMX (80%) adsorption on CBMs.•Impact tendencies of SBET, pHsol, C0 on adsorption were similar for TC and SMX.•Chemical compositions and pHpzc of CBMs showed different influences on TC and SMX.
Antibiotics as emerging pollutants have attracted extensive attention due to their ecotoxicity and persistence in the environment. Adsorption of antibiotics on carbon-based materials (CBMs) such as biochar and activated carbon was recognized as one of the most promising technologies for wastewater treatment. This study applied machine learning (ML) methods to develop generic prediction models of tetracycline (TC) and sulfamethoxazole (SMX) adsorption on CBMs. The results suggested that random forest outperformed gradient boosting trees and artificial neural network for both TC and SMX adsorption models. The random forest models could accurately predict the adsorption capacity of antibiotics on CBMs using material properties and adsorption conditions as model inputs. The developed ML models presented better generalization ability than traditional isotherm models under variable environmental conditions (e.g., temperature, solution pH) and adsorbent types. The relative importance analysis and partial dependence plots based on ML models were performed to compare TC and SMX adsorption on CBMs. The results indicated the critical role of specific surface area for both TC (24%) and SMX (45%) adsorption, while the other material properties (e.g., H/C, (O + N)/C, pHpzc) showed variable influences due to the differences in molecular structures, functional groups, and pKa values of TC and SMX. The accurate ML prediction models with generalization ability are useful for designing efficient CBMs with minimal experimental screening, while the relative importance and partial dependence plot analysis can guide rational applications of CBMs for antibiotics wastewater treatment.
The growing environmental issues caused by CO2 emission accelerate the development of carbon capture and storage (CCS), especially bio-energy CCS as an environment-friendly and sustainable technique ...to capture CO2 using porous carbon materials (PCMs) produced from various biomass wastes. This study developed quantitative structure-property relationship models based on 6244 CO2 adsorption datasets of 155 PCMs to predict the CO2 adsorption capacity and analyze the relative significance of physicochemical properties. The results suggested that random forest (RF) models showed good accuracy and predictive performance based on physicochemical parameters of PCMs and adsorption conditions with the test dataset (R2 > 0.9). In general, textural properties were more crucial than chemical compositions of porous carbons to the change of CO2 adsorption capacity. At a low pressure (0.1 bar), the volumes of mesopore and micropore played an important role according to the RF analysis, but had a negative correlation with CO2 adsorption capacity based on the Pearson correlation coefficient (PCC) analysis. The relative importance of ultra-micropore increased along with the increase of pressure. The PCC value between ultra-micropore volume and CO2 uptake amount was up to 0.715 (p < 0.01) at 1 bar and 0 °C. The influence of chemical compositions was complex. The N content was confirmed to positively correlate to the CO2 adsorption capacity but its contribution was much lower than that of ultra-micropores. This study provided a new approach for fostering the rational design of porous carbons for CO2 capture via statistical analysis and machine learning method, which facilitated adsorbents screening for the cleaner production.
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•CO2 adsorption on 155 porous carbon materials was modeled by machine learning.•Random forest showed a good prediction ability for CO2 adsorption capacity (R2 > 0.9).•Textural properties were more crucial for CO2 adsorption than chemical compositions.•The relative importance of ultra-micropore volume improved as pressure increased.•Total N content contributed less to CO2 adsorption than ultra-micropore volume.
Abstract
The precise and efficient construction of axially chiral scaffolds, particularly toward the aryl-alkene atropoisomers with impeccably full enantiocontrol and highly structural diversity, ...remains greatly challenging. Herein, we disclose an organocatalytic asymmetric nucleophilic aromatic substitution (S
N
Ar) reaction of aldehyde-substituted styrenes involving a dynamic kinetic resolution process via a hemiacetal intermediate, offering a novel and facile way to significant axial styrene scaffolds. Upon treatment of the aldehyde-containing styrenes bearing (
o
-hydroxyl)aryl unit with commonly available fluoroarenes in the presence of chiral peptide-phosphonium salts, the S
N
Ar reaction via an exquisite bridged biaryl lactol intermediate undergoes smoothly to furnish a series of axially chiral aldehyde-containing styrenes decorated with various functionalities and bioactive fragments in high stereoselectivities (up to >99% ee) and complete
E
/
Z
selectivities. These resulting structural motifs are important building blocks for the preparation of diverse functionalized axial styrenes, which have great potential as efficient and privileged chiral ligands/catalysts in asymmetric synthesis.
Enantioselective diverse synthesis of a small-molecule collection with structural and functional similarities or differences in an efficient manner is an appealing but formidable challenge. ...Asymmetric preparation and branching transformations of tetrahydroindolizines in succession present a useful approach to the construction of N-heterocycle-containing scaffolds with functional group, and stereochemical diversity. Herein, we report a breakthrough toward this end via an initial diastereo- and enantioselective 3 + 2 cycloaddition between pyridinium ylides and enones, following diversified sequential transformations. Chiral N,N′-dioxide-earth metal complexes enable the generation of optically active tetrahydroindolizines in situ, across the strong background reaction for racemate-formation. In connection with deliberate sequential transformations, involving convenient rearomatic oxidation, and light-active aza-Norrish II rearrangement, the tetrahydroindolizine intermediates were converted into the final library including 3-arylindolizine derivatives and dicarbofunctionalized 1,5-dicarbonyl compounds. More importantly, the stereochemistry of four-stereogenic centered tetrahydroindolizine intermediates could be efficiently transferred into axial chirality in 3-arylindolizines and vicinal pyridyl and aryl substituted 1,5-diketones. In addition, densely functionalized cyclopropanes and bridged cyclic compounds were also discovered depending on the nature of the pyridinium ylides. Mechanism studies were involved to explain the stereochemistry during the reaction processes.
We reported a mechanistic study on asymmetric O–H insertion reaction of α-diazoester with carboxylic acid using Rh2(OAc)4/chiral guanidine-amide as the cocatalyst by density functional theory ...B3LYP-D3(BJ)/def2-TZVP//B3LYP-D3(BJ)/6-31G**, SDD (SMD, Et2O). The catalytic reaction included two stages: (i) formation of Rh–carbene species, subsequently by the construction of C–O bond forming enol and (ii) chiral guanidinium salt-assisted H-transfer to the enol. In cooperative catalysis, Rh2(OAc)4 helped to form an enol intermediate via high-reactivity Rh–carbene species, while the in situ-formed guanidium carboxylate acted as a chiral proton shuttle to construct a hydrogen bonding net for the stereo-determinant protonation. The repulsions between the phenyl group of the enol intermediate and the cyclohexyl as well as the ortho-substituted isopropyl group of chiral guanidine played important roles in controlling stereoselectivity. A disadvantageous steric arrangement in si-face attack weakened the stabilizing electrostatic and orbital interaction of reacting species in the H-transfer step, enhancing the pathway to form a predominant product with R-configuration in the two competing pathways. A model was proposed to explain the asymmetric induction of chiral guanidine-amide in protonation.
The enantioselective synthesis of S-stereogenic sulfinamides has garnered considerable attention due to their structural and physicochemical properties. However, catalytic asymmetric synthesis of ...sulfinamides still remains daunting challenges, impeding their broad application in drug discovery and development. Here, we present an approach for the synthesis of S-stereogenic sulfinamides through peptide-mimic phosphonium salt-catalyzed asymmetric skeletal reorganization of simple prochiral and/or racemic sulfoximines. This methodology allows for the facile access to a diverse array of substituted sulfinamides with excellent enantioselectivities, accommodating various substituent patterns through desymmetrization or parallel kinetic resolution process. Mechanistic experiments, coupled with density functional theory calculations, clarify a stepwise pathway involving ring-opening and ring-closing processes, with the ring-opening step identified as crucial for achieving stereoselective control. Given the prevalence of S-stereogenic centers in pharmaceuticals, we anticipate that this protocol will enhance the efficient and precise synthesis of relevant chiral molecules and their analogs, thereby contributing to advancements in drug discovery.
The oxindole scaffold represents an important structural feature in many natural products and pharmaceutically relevant molecules. Herein, we report a visible-light-induced modular methodology for ...the synthesis of complex 3,3'-disubstituted oxindole derivatives. A library of valuable fluoroalkyl-containing highly sterically congested oxindole derivatives can be synthesized by a catalytic three-component radical coupling reaction under mild conditions (metal & photocatalyst free, >80 examples). This strategy shows high functional group tolerance and broad substrate compatibility (including a wide variety of terminal or non-terminal alkenes, conjugated dienes and enynes, and a broad array of polyfluoroalkyl iodide and oxindoles), which enables modular modification of complex drug-like compounds in one chemical step. The success of solar-driven transformation, large-scale synthesis, and the late-stage functionalization of bioactive molecules, as well as promising tumor-suppressing biological activities, highlights the potential for practical applications of this strategy. Mechanistic investigations, including a series of control experiments, UV-vis spectroscopy and DFT calculations, suggest that the reaction underwent a sequential two-step radical-coupling process and the photosensitive perfluoroalkyl benzyl iodides are key intermediates in the transformation.
A rhodium-catalyzed transarylation of benzamides via selective C–C bond activation with arylboronic acids was described, which was distinct from the conventional metal-catalyzed C–N bond activation. ...This transformation exhibited good functional group compatibility with yields up to 88%, offering a practical approach for the construction and functionalization of benzamides. Preliminary experimental and computational studies revealed the selectivity of metal insertion into the C–C bond or the C–N bond was greatly affected by substituents on the amide’s N atom.
Density functional theory (DFT) calculations were performed to investigate the mechanism and the enantioselectivity of the aza-Henry reaction of isatin-derived ketimine catalyzed by chiral ...guanidine-amide catalysts at the M06-2X-D3/6-311+G(d,p)//M06-2X-D3/6-31G(d,p) (toluene, SMD) theoretical level. The catalytic reaction occurred via a three-step mechanism: (i) the deprotonation of nitromethane by a chiral guanidine-amide catalyst; (ii) formation of C-C bonds; (iii) H-transfer from guanidine to ketimine, accompanied with the regeneration of the catalyst. A dual activation model was proposed, in which the protonated guanidine activated the nitronate, and the amide moiety simultaneously interacted with the ketimine substrate by intermolecular hydrogen bonding. The repulsion of CPh
group in guanidine as well as
-Boc group in ketimine raised the Pauli repulsion energy (∆
) and the strain energy (∆
) of reacting species in the unfavorable
-face pathway, contributing to a high level of stereoselectivity. A new catalyst with cyclopropenimine and 1,2-diphenylethylcarbamoyl as well as sulfonamide substituent was designed. The strong basicity of cyclopropenimine moiety accelerated the activation of CH
NO
by decreasing the energy barrier in the deprotonation step. The repulsion between the
-Boc group in ketimine and cyclohexyl group as well as chiral backbone in the new catalyst raised the energy barrier in C-C bond formation along the
-face attack pathway, leading to the formation of
-configuration product. A possible synthetic route for the new catalyst is also suggested.
The mechanism and origin of the stereoselectivity of the asymmetric carbonyl-ene reaction between N-methyl-protected isatin and 2-methyloxypropene catalyzed by the N,N′-dioxide–Mg(OTf)2 complex were ...investigated by DFT and ONIOM methods. The background reaction occurred via a two-stage, one-step mechanism with a high activation barrier of 30.4 kcal mol–1 at the B3LYP-D3(BJ)/6-311G**(SMD, CH2Cl2)//B3LYP/6-31G*(SMD, CH2Cl2) level at 303 K. Good linear correlations between the global nucleophilicity index (N) and the activation energy barrier (ΔG ⧧) were found. The chiral N,N′-Mg(II) complex catalyst could enhance the electrophilicity of the isatin substrate by forming hexacoordinate Mg(II) reactive species. The substituent at the ortho positions of aniline combined with the aliphatic ring of the backbone in the chiral N,N′-dioxide ligand played an important role in the construction of a favorable “pocket-like” chiral environment (chiral pocket) around the Mg(II) center, directing the preferential orientation of the incoming substrate. An unfavorable steric arrangement in the re-face attack pathway translated into a more destabilizing activation strain of the ene substrate, enhancing enantiodifferentiation of two competing pathways for the desired R product. This work also suggested a new phosphine ligand (N-L1) for the formation of the Mg(II) complex catalyst for the asymmetric carbonyl-ene reaction. The chiral environment and Lewis acidity of the Mg(II) complex could be fine-tuned by introduction of P-donor units into the ligand for highly efficient asymmetric catalysis.
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