Iron-Catalyzed Aerobic Oxidation of Aldehydes： Single Component Catalyst and Mechanistic Studies

An aerobic oxidation of aldehydes towards carboxylic acids in MeCN using 1 atm of pure oxygen or oxygen in air as the oxidant and a catalytic amount of single component catalyst, Fe（NO3）3.9H20, has been developed. Carboxylic acids with different synthetically useful functional groups were obtained at room temperature. Two mechanistic pathways have been proposed based on isotopic labeling, NMR monitoring, and control experiments. The practicality of this reaction has been demonstrated by conducting several 50 mmol-scale reactions using pure oxygen or an air-flow of -30 mL/min.

Computational mechanistic studies of acceptorless dehydrogenation reactions catalyzed by transition metal complexes

Acceptorless dehydrogenation (AD) that uses non-toxic reagents and produces no waste is a type of catalytic reactions toward green chemistry. Acceptorless alcohol dehydrogenation (AAD) can serve as a key step in constructing new bonds such as C-C and C-N bonds in which alcohols need to be activated into more reactive ketones or aldehydes. AD reactions also can be utilized for hydrogen production from biomass or its fermentation products (mainly alcohols). Reversible hydrogenation/ dehy-drogenation with hydrogen uptake/release is crucial to realization of the potential organic hydride hydrogen storage. In this article, we review the recent computational mechanistic studies of the AD reactions catalyzed by various transition metal complexes as well as the experimental developments. These reactions include acceptorless alcohol dehydrogenations, reversible dehydrogenation/hydrogenation of nitrogen heterocycles, dehydrogenative coupling reactions of alcohols and amines to construct C-N bonds, and dehydrogenative coupling reactions of alcohols and unsaturated substrates to form C-C bonds. For the catalysts possessing metal-ligand bifunctional active sites (such as 28, 45, 86, 87, and 106 in the paper), the dehydrogenations prefer the "bifunctional double hydrogen transfer" mechanism rather than the generally accepted-H elimination mechanism. However, methanol dehydrogenation involved in the C-C coupling reaction of methanol and allene, catalyzed by the iridium complex 121, takes place via the-H elimination mechanism, because the Lewis basicity of either the-allyl moiety or the carboxyl group of the ligand is too weak to exert high Lewis basic reactivity. Unveiling the catalytic mechanisms of AD reactions could help to develop new catalysts.

Mechanistic Studies on Propargyl Alcohol-Tethered Alkylidenecyclopropane with Aryldiazonium Salt Initiated by Visible Light

This paper discloses the reaction mechanism of two consecutive but different visible light photo-induced chain processes for the rapid construction of spirobi[indene]skeletons.The first process is triggered by a photo-induced single-electron-transfer(SET)of an electron donor-accepter(EDA)complex.The second process is initiated by a direct SET process between aryldiazonium salt and the excited allenic intermediate.In these two processes,another SET took place respectively on the in situ formed radical intermediate to realize a redox-neutral outcome.The mechanistic studies have been carried out by control experiments,kinetic and spectroscopic analyses,deuterium labeling experiments to support these two chain processes.

Synergistic degradation of phenols by bimetallic CuO-Co_3O_4@γ-Al_2O_3 catalyst in H_2O_2/HCO_3^- system

The development of new catalytic techniques for wastewater treatment has long attracted much attention from industrial and academic communities.However,because of catalyst leaching during degradation,catalysts can be short lived,and therefore expensive,and unsuitable for use in wastewater treatment.In this work,we developed a bimetallic CuO-Co3O4@γ-Al2O3 catalyst for phenol degradation with bicarbonate-activated H2O2.The weakly basic environment provided by the bicarbonate buffer greatly suppresses leaching of active Cu and Co metal ions from the catalyst.X-ray diffraction and X-ray photoelectron spectroscopy results showed interactions between Cu and Co ions in the CuO-Co3O4@γ-Al2O3 catalyst,and these improve the catalytic activity in phenol degradation.Mechanistic studies using different radical scavengers showed that superoxide and hydroxyl radicals both played significant roles in phenol degradation,whereas singlet oxygen was less important.

Network pharmacology-based elucidation of molecular biological mechanisms of Kanglaite injection for treatment of non-small cell lung cancer

Objective: To investigate the effective compounds, potential targets and molecular mechanism of Kanglaite injection (KLTi) in the treatment of Non-Small Cell Lung Cancer (NSCLC) based on network pharmacology. Methods: The active compounds and targets of KLTi which extracted and isolated from Coix Seed were screened by Traditional Chinese Medicine Systems Pharmacology Database and Analysis Platform (TCMSP). The related genes of NSCLC were obtained by searching the Human Gene Database (GeneCards) and Online Mendelian Inheritance in Man (OMIM). The candidate targets of KLTi in the treatment of NSCLC were obtained after extracting the intersection network. The "drug-component-target-disease" network was constructed with the help of Cytoscape 3.7.2. The Protein- Protein Interaction networks were constructed on the STRING platform and core network modules were screened. The Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) enrichment analysis of candidate genes were performed using Metascape platform, and a "pathway-target- compounds" network was constructed to further screen key genes and active compounds. Results: A total of 11 compounds, 22 candidate targets, 206 GO functions and 12 KEGG pathways were obtained. Conclusion: The active compounds of KLTi in the treatment of NSCLC are stigmasterol, stigmasterol α1 and ergosterol. The key targets are PGR, NCOA2, PTGS2, NR3C2, and PTGS1. The core GO functions included receptor activity and binding, neuronal signal transmission and hormone stimulation;KEGG mainly involves cancer pathways, neuroactive ligand-receptor interactions and calcium signaling pathways. This study reveals the molecular biological mechanism of KLTi in the treatment of NSCLC, which is speculated to be related to neuroendocrine, providing a new basis and therapeutic direction for subsequent clinical application and experimental research.

Enantioselective iridium-catalyzed allylic substitution with a Reformatsky reagent: direct construction of β-stereogenic homoallylic esters

The Reformatsky reagent derived from ethyl bromoacetate circumvents the challenge associated with the direct regio-and enantioselective iridium-catalyzed allylic alkylation with an unstabilized aliphatic ester enolate. Notably, this work represents the first example of using a Reformatsky reagent in a metal-allyl reaction, which permits the direct construction of enantioenriched β-stereogenic homoallylic esters without preactivation of the pronucleophile or post-reaction modification of the product(e.g., thermal decarboxylation of a 1,3-dicarbonyl). Moreover, the process allows the coupling of a broad range of sterically and electronically diverse electrophiles bearing aryl, heteroaryl and alkenyl derivatives, including the significantly more challenging alkyl-substituted allylic carbonates. The versatility of the ester product is exemplified by a series of functional group manipulations and the development of a concise and efficient enantioselective total synthesis of the natural product,(+)-descurainolide A. Finally, mechanistic studies indicate that the zinc enolate behaves as a soft nucleophile that undergoes outer-sphere alkylation.

Shedding light on the reversible deactivation of carbon-supported single-atom catalysts in hydrogenation reaction

Carbon-supported single-atom catalysts were found to suffer reversible deactivation in catalytic hydrogenation,but the mechanism is still unclear.Herein,nitro compounds hydrogenation catalyzed by N-doped carbon-supported Co single atom(Co1/NC)was taken as a model to uncover the mechanism of the reversible deactivation phenomenon.Co1/NC exhibited moderate adsorption towards the substrate molecules(i.e.,nitro compounds or related intermediates),which could be strengthened by the confinement effect from the porous structure.Consequently,substrate molecules tend to accumulate within the pore channel,especially micropores that host Co1,making it difficult for the reactants to access the active sites and finally leading to their deactivation.The situation could be even worse when the substrate molecules possess a large size.Nevertheless,the catalytic activity of Co1/NC could be restored via a simple thermal treatment,which could remove the adsorbates within the pore channel,hence releasing active sites that were originally inaccessible to reactants.

Comments on “Efficient adsorption of Mn(Ⅱ) by layered double hydroxides intercalated with diethylenetriaminepentaacetic acid and the mechanistic study.J.Environ.Sci.85,56-65”

In the paper entitled"Efficient adsorption of Mn(Ⅱ)by layered double hydroxides intercalated with di ethylenetriaminepentaacetic acid and the mechanistic study"in Journal of Environmental Sciences,volume 85,page 56-65,there were problems with mathematical notation and dimensional errors in the calculation for Giibbs free energy.In Section 2.5:Adsorption isotherms and thermodynamics studies,authors calculated the Gibbs free energy change(△G°)

Magnetic field effects on photochemical reaction--III. Mechanistic study of the photodecarboxylation of arylmethyl esters in micellar solutions

Photolysis of benzyl phenylacetate (ACO_2A), benzyl p-methylphenylacetate (BCO_2A) and 1-naphthyl phenylacetate (ACO_2Np) in homogeneous and micellar solutions results in products typical of radical coupling reactions and loss of carbon dioxide. The cage effects upon direct photolysis of these esters in acetonitrile are significantly greater than zero and those in SDS or HDTBr micellar solutions are even greater. In the triplet sensitization reaction of ACO_2 Np in micellar solutions the cage effects are smaller than those obtained upon direct irradiation. However, the application of a 0.05 or 0.2 T external magnetic field in the photolysis in micellar solutions decreases the cage effects dramatically. All these results suggest that the photoextrusions of carbon dioxide from these esters proceed via radical intermediates, and upon direct photolysis the reactive states for the cleavage re- action involve both singlet and triplet excited states.

Using Network Pharmacology and Molecular Docking Tools to Investigate the Potential Mechanism of Ephedra-Gypsum in the Treatment of Respiratory Diseases

Objective:The objective of this study was to investigate the potential mechanisms of ephedra-gypsum in the treatment ofrespiratory diseases(RDs)using network pharmacology and molecular docking techniques.Materials and Methods:The TCMSP and UniProt databases were used to mine the active components and targets of ephedra-gypsum,and the targets of RD were screened using the Online Mendelian Inheritance in Man(OMIM)and GeneCards databases.The protein-protein interaction network graph was created using the drug-disease intersection targets in the STRING database.The network diagram was analyzed using Cytoscape 3.9.1's topology function.The gene ontology(GO)and KEGG enrichment analyses were performed using the DAVID platform.Molecular docking bioactivity validation of the main active components and core targets was performed using AutoDock and PyMOL software.Results:Twenty-four compounds were screened,and 113 drug-disease targets overlapped.In total,358 biological processes,67 molecular functions,38 cellular components of GO,and 139 pathways were identified.Molecular docking analysis demonstrated the strong binding ability of tumor protein 53(TP53)-luteolin.Conclusion:The core components of ephedra-gypsum,such as quercetin,luteolin,kaempferol,and CaSO_(4)·2H_(2)O,act on key targets,such as tumor necrosis factor(TNF),interleukin-6(IL-6),TP53,and IL-1β through cytokine-mediated signaling pathways,infiammatory responses,cell proliferation,and apoptosis.This could be useful for the treatment of RD.

Advances in Fe(II)/2-ketoglutarate-dependent dioxygenase-mediated C-H bond oxidation for regioselective and stereoselective hydroxyl amino acid synthesis:from structural insights into practical applications

The asymmetric hydroxylation of inactive carbon atoms in organic compounds remains an important reaction in the industrial synthesis of valuable chiral compounds.Fe(II)and 2-ketoglutarate-dependent dioxygenases(Fe/2-kg DOs)are the largest known subgroups of mononuclear nonheme-Fe(II)-dependent oxygenases,catalyzing various oxidation reactions of C-H bonds.Recent developments in Fe/2-kg DO-related researches have coupled concepts from bioinformatics,synthetic biology,and computational biology to establish effective biotransformation systems.The most well-studied and characterized activ-ity of the Fe/2-kg DOs is substrate hydroxylation,with regard to which mechanistic studies involving the Fe center assist in engineering the protein frameworks of these enzymes to obtain the desired catalytic enhancements.Amino acids are typical substrates of Fe/2-kg DOs and are usually converted into hydroxyl amino acids,which are widely used as intermediates in pharmaceutical and fine chemical industries.Herein,we have reviewed prior structural and mechanistic studies on Fe/2-kg DOs,as well as studies on the Fe/2-kg DO-mediated selective C-H oxidation process for selective hydroxyl amino acid synthesis,which will further our journey along the promising path of building complexity via C-H bond oxidation.Further,new bioinformatics techniques should be adopted with structure-based protein rational design to mine sequence databases and shrink mutant libraries to produce a diverse panel of functional Fe/2-kg DOs capable of catalyzing targeted reactions.

Efficient synthesis of chromenopyridine and chromene via MCRs

MCRs for preparation of chromenopyridines under reflux conditions and chromenes at room temperature conditions from different salicylaldehydes,malononitrile and different thiols（mol ratio- 1：2：1） were established.Mechanistic investigation suggests that the MCRs undergo different pathways at different temperatures and catalyzed by different organic bases.The structure of chromenopyridine and chromene are confirmed by crystal X-ray crystallography.

Probing reaction pathways for H_(2)O-mediated HCHO photooxidation at room temperature

Photooxidation provides a promising strategy for removing the dominant indoor pollutant of HCHO,while the underlying photooxidation mechanism is still unclear,especially the exact role of H2O molecules.Herein,we utilize in-situ spectral techniques to unveil the H2O-mediated HCHO photooxidation mechanism.As an example,the synthetic defective Bi2WO6 ultrathin sheets realize high-rate HCHO photooxidation with the assistance of H2O at room temperature.In-situ electron paramagnetic resonance spectroscopy demonstrates the existence of•OH radicals,possibly stemmed from H2O oxidation by the photoexcited holes.Synchrotron-radiation vacuum ultraviolet photoionization mass spectroscopy and H218O isotope-labeling experiment directly evidence the formed•OH radicals as the source of oxygen atoms,trigger HCHO photooxidation to produce CO2,while in-situ Fourier transform infrared spectroscopy discloses the HCOO*radical is the main photooxidation intermediate.Density-functional-theory calculations further reveal the•OH formation process is the rate-limiting step,strongly verifying the critical role of H2O in promoting HCHO photooxidation.This work first clearly uncovers the H2O-mediated HCHO photooxidation mechanism,holding promise for high-efficiency indoor HCHO removal at ambient conditions.