Latest ArticlesWe report two air-stable nickel(Ⅱ) half-sandwich complexes, Cp*Ni(1,2-Cy2PC6H4O) (1) and Cp*Ni(1,2-Ph2PC6H4NH) (2), for cooperative B-H bond activation and their applications in catalytic hydroboration of unsaturated organic compounds. Both 1 and 2 react with HBpin by adding the B-H bond across the Ni−X bond (X = O or N), giving rise to the 18-electron Ni(Ⅱ)−H active species, [H1(Bpin)] and [H2(Bpin)]. Subtle tuning of the Ni−X pair and the supporting ancillary phosphine have a significant effect on the reactivity and catalytic performance of Cp*Ni(1,2-R2PC6H4X). Unlike [H2(Bpin)], the activation of HBpin in [H1(Bpin)] is reversible, which enables the Ni−O complex to be an effective cooperative catalyst in the hydroboration of N-heteroarenes, and as well as ketones and imines.
A palladium-catalyzed cascade cyclization of allenylethylene carbonates with 1,3-indandiones was developed, providing biologically interesting tetracyclic dihydrocyclopentaindenofuranone derivatives having three contiguous quaternary carbon centers in moderate to high yields with excellent diastereoselectivities. In this reaction, the allene moiety was fully fused into the cyclopentene ring.
Photodynamic therapy (PDT) has shown great application potential in cancer treatment and the important manifestation of PDT in the inhibition of tumors is the activation of immunogenic cell death (ICD) effects. However, the strategy is limited in the innate hypoxic tumor microenvironment. There are two key elements for the realization of enhanced PDT: specific cellular uptake and release of the photosensitizer in the tumor, and a sufficient amount of oxygen to ensure photodynamic efficiency. Herein, self-oxygenated biomimetic nanoparticles (CS@M NPs) co-assembled by photosensitizer prodrug (Ce6-S-S-LA) and squalene (SQ) were engineered. In the treatment of triple negative breast cancer (TNBC), the oxygen carried by SQ can be converted to reactive oxygen species (ROS). Meanwhile, glutathione (GSH) consumption during transformation from Ce6-S-S-LA to chlorin e6 (Ce6) avoided the depletion of ROS. The co-assembled (CS NPs) were encapsulated by homologous tumor cell membrane to improve the tumor targeting. The results showed that the ICD effect of CS@M NPs was confirmed by the significant release of calreticulin (CRT) and high mobility group protein B1 (HMGB1), and it significantly activated the immune system by inhibiting the hypoxia inducible factor-1alpha (HIF-1α)-CD39-CD73-adenosine a2a receptor (A2AR) pathway, which not only promoted the maturation of dendritic cells (DC) and the presentation of tumor specific antigens, but also induced effective immune infiltration of tumors. Overall, the integrated nanoplatform implements the concept of multiple advantages of tumor targeting, reactive drug release, and synergistic photodynamic therapy-immunotherapy, which can achieve nearly 90% tumor suppression rate in orthotopic TNBC models.
Metal/nucleophilic Lewis base dual catalysis has been recognized as a reliable and promising strategy for finishing ideal organic synthesis over the past decades. The new strategy can usually achieve some chemical reactions that cannot be realized by the traditionally mono-catalytic system, dramatically expanding the synthetic utility of chemical transformations by leveraging additional activation modes. Thus considerable progress has been made in the synthesis of a wide range of heterocyclic and biologically active compounds by using the combination of diversely metal/nucleophilic Lewis base dual catalysts, including metal/phosphine, metal/N-heterocyclic carbene (NHC) and metal/tertiary amine dual catalysis systems. In this review, we describe a comprehensive and updated advance of metal/nucleophilic Lewis base dual catalytic annualtion reactions, meanwhile, the related mechanism and the application of these annulation strategies in natural product total synthesis will be highlighted in detail.
An algorithm capable of predicting and optimizing the gradient separation of LC × LC system was developed in this paper. Two groups of structural analogues, five ginsenosides as well as eight bisphenols, which were difficult to discriminate in routine analysis, were used to verify the effectiveness of the proposed algorithm in fast separation optimization. Average errors of retention times below 1% were found in the retention prediction for all types of gradient programs, implying that the theory could lead to high quality in prediction of the retention times under gradients elution. Meanwhile, 84% of relative average deviations (RADs) between the predicted peak width and the measured ones were less than 20%. The larger deviation occurred at the time when the peak appeared while the gradient of the mobile phase changed, which led the deviations increased to 20%–42%. In all, method development and optimization for LC × LC tandem system was realized by the homemade user-friendly software. The present protocol may turn on great opportunities for the convenient method development in analysis of trace structural analogues in environmental, food and biological samples.
Peracetic acid (CH3C(O)OOH, PAA)-based heterogeneous advanced oxidation process (AOP) has attacked intensive interests due to production of various reactive species. Herein, Co(OH)2 nanoparticles decorated biochar (Co(OH)2/BC) was fabricated by a simple and controllable method, which was used to degrade tetracycline hydrochloride (TTCH) in water through PAA activation. The results indicated that 100% TTCH (C0 = 10 µmol/L) degradation efficiency was realized within 7 min at pH 7, with a high kinetic rate constant (k1) of 0.64 min−1 by the optimized Co(OH)2/BC. Material characterizations suggested that Co(OH)2 nanoparticle was successfully decorated on biochar, leading to more active sites and electronic structure alteration of biochar, thus greatly promoting the catalytic cleavage of PAA for radicals production. Then, the reactive oxygen species (ROS) quenching experiments and electron paramagnetic resonance (EPR) analysis demonstrated the key species were alkoxyl radicals (R–O•, mainly CH3CO2• and CH3CO3•), HO• and 1O2 in this system. Besides, density functional theory (DFT) calculation on Fukui index further revealed that the vulnerable sites of TTCH and three possible degradation pathways were proposed. This study can provide a new strategy for synthesis functional materials in PAA activation AOPs for removal of antibiotics in water.
In-depth exploration of the relationship among different adsorption sites is conducive to design of efficient adsorbents for target pollutants removal from water. In this study, the experiments, multivariate non-linear regression and density functional theory calculations are applied to explore the possible synergistic effects of three nitrogen (N)-containing sites on cow dung biochar surface for sulfamethoxazole (SMX) adsorption. Notably, a strong synergistic effect between pyridinic N and pyrrolic N sites was found for sulfamethoxazole adsorption. The adsorption energies of SMX on four pyrrolic N-coupled pyridinic N structures were −1.02, −0.41, −0.49 and −0.72 eV, much higher than the sum of adsorption energies (−0.31 eV) on pyrrolic N and pyridinic N. Besides, the alteration of Mulliken charge revealed that the simultaneous presence of pyridinic N and pyrrolic N improved the electron transfer remarkably from −0.459 e and 0.094 e to −0.649 e and 0.186 e, benefiting for SMX adsorption. This work firstly explored the possible synergies of adsorption sites on biochar surface for organic contaminants removal from water, which shed new lights on the adsorption mechanism and provided valuable information to design efficient adsorbents in the field of water treatment.
Most catalytic processes are achieved by heating the whole reaction systems including the entire reactor, substrate and solvent, which leads to energy loss and obvious heat transfer limits. In this study, induction heating was employed to boost the catalytic Suzuki-Miyaura cross-coupling reactions by using conductive superparamagnetic microspheres with loaded Pd nanoparticles as heterogeneous catalysts. It was found that, at the same apparent reaction temperatures, the reactions by adopting the induction heating all exhibit better catalytic performance with higher conversion and yield, as compared to the reactions using conventional joule heating. The improvement is mainly attributed to the localized heating effect endowed by high efficiency of the heat transfer from the heat source to catalytic sites, which dissipates the electromagnetic energy through Néel relaxation mechanism. Moreover, it has be found that the reactions have been largely accelerated, resulting in much shorter reaction time required to approach a given value of reactant conversion. These results indicate that the unique heating method based on the superparamagnetic nanomaterials as both the inductive component and catalyst support holds a promising application for fast and efficient heterogeneous catalytic process, and exhibits potential for improving energy transfer efficiency and reducing the side reactions attributed to the uneven temperature profile.
The visible light induced multicomponent reaction of styrene, carbon disulfide, amine and ethyl difluorobromoacetate for the synthesis of thiodifluoroesters is disclosed. This developed protocol offers a facile and general route to access various valuable thiodifluoroesters in moderate to good yields. Preliminary mechanistic studies revealed that a radical process might be involved in this transformation.
Integrating discrete plasmonic nanoparticles into assemblies can induce plasmonic coupling that produces collective plasmonic properties, which are not available for single nanoparticles. Theoretical analysis revealed that plasmonic coupling derived from assemblies could produce stronger electromagnetic field enhancement effects. Thus, plasmonic assemblies enable better performance in plasmon-based applications, such as enhanced fluorescence and Raman effects. This makes them hold great potential for trace analyte detection and nanomedicine. Herein, we focus on the recent advances in various plasmonic nanoassembles such as dimers, tetramers, and core-satellite structures, and discuss their applications in biosensing and cell imaging. The fabrication strategies for self-assembled plasmonic nanostructures are described, including top-down strategies, self-assembly methods linked by DNA, ligand, polymer, amino acid, or proteins, and chemical overgrowth methods. Thereafter, their applications in biosensor and cell imaging based on dark-field imaging, surface-enhanced Raman scattering, plasmonic circular dichroism, and fluorescence imaging are discussed. Finally, the remaining challenges and prospects are elucidated.
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