Latest ArticlesAn N-heterocyclic carbene (NHC)-catalysed retro-aldol/aldol cascade reaction of spirooxindole-based β-hydroxyaldehyde has been developed. The ring opening-closure process enables the diastereodivergent synthesis of spirocyclopentaneoxindole products with four consecutive stereocenters by simply changing the reaction solvents (THF or DCE). The Michael/aldol/retro-aldol/aldol sequential protocol allows the diastereodivergent synthesis of spirocyclopentaneoxindoles from 3-substituted oxindole and α, β-unsaturated aldehyde under the relay catalysis of a chiral secondary amine and an NHC catalyst. Moreover, four stereoisomers of the product can be selectively provided by using different combinations of a chiral secondary amine and a solvent.
A visible light and base promoted O-H insertion/cyclization of para-quinone methides with aryl diazoacetates is developed. This one-pot two step reaction offers a mild and efficient approach for the synthesis of biologically important 2, 3-dihydrobenzofuran derivatives in good yields and moderate diastereoselectivities.
When treated with an alkoxide base like t-BuOK in aprotic solvent, N-diphenylmethyl imino oxindoles, made conveniently through condensation of corresponding isatins with N-diphenylmethyl amine, are deprotonated to form azaallyl anions. Allylation and alkylation of this type of intermediates proceed smoothly with diverse C-electrophiles. Acidic work up finishes 3-amino-3-allyl/alkyl oxindoles. The overall transformation equals to an umpolung process at the C3 of isatins.
Recently, photodynamic therapy (PDT) has been extensively applied in clinical and coadjuvant treatment of various kinds of tumors. However, the photosensitizer (PS) of PDT still lack of high production of singlet oxygen (1O2), low cytotoxicity and high biocompatibility. Herein, we propose a facile method for establishing a new core-shell structured Sn nanocluster@carbon dots (CDs) PS. Firstly, Sn4+@S-CDs complex is synthesized using the sulfur-doped CDs (S-CDs) and SnCl4 as raw materials, and subsequently the new PS (Sn nanocluster@CDs) is obtained after vaporization of Sn4+@S-CDs solution. Remarkably, the obtained Sn nanocluster@CDs show an enhanced fluorescence as well as a higher 1O2 quantum yield (QY) than S-CDs. The high 1O2 QY (58.3%) irradiated by the LED light (400–700 nm, 40 mW/cm2), induce the reduction of 4T1 cancer cells viability by 25%. More intriguingly, no visible damage happens to healthy cells, with little impact on liver tissue due to renal excretion, both in vitro and in vivo experiments demonstrate that Sn nanocluster@CDs may become a promising PS, owning a high potential for application in PDT.
Hematite (α-Fe2O3) is a promising photoanode for photoelectrochemical (PEC) water splitting. However, the severe charge recombination and sluggish water oxidation kinetics extremely limit its use in photohydrogen conversion. Herein, a co-activation strategy is proposed, namely through phosphorus (P) doping and the loading of CoAl-layered double hydroxides (CoAl-LDHs) cocatalysts. Unexpectedly, the integrated system, CoAl-LDHs/P-Fe2O3 photoanode, exhibits an outstanding photocurrent density of 1.56 mA/cm2 at 1.23 V (vs. reversible hydrogen electrode, RHE), under AM 1.5 G, which is 2.6 times of pure α-Fe2O3. Systematic studies reveal that the remarkable PEC performance is attributed to accelerated surface OER kinetics and enhanced carrier separation efficiency. This work provides a feasible strategy to enhance the PEC performance of hematite photoanodes.
With regard to the reaction of higher alcohol synthesis (HAS), the optimizations of activity and selectivity towards C2+ alcohol are restricted by the improper equilibrium in two different CO activation pathways and chain growth capacity. Herein, we find that delibrately controlling the compositions of catalysts is an effective strategy to achieve the equilibrium of CO activation pathways and promote the chain growth. As a result, the optimized Cu0.25Co0.75 alloy catalyst can achieve a large proportion of higher alcohol in alcohol products (C2+OH/MeOH = 4.40), together with high CO conversion of 71.27% and space-time-yield of 147.65 g kg−1 h−1. The mechanistic studies suggest that the good performance of Cu0.25Co0.75 catalyst is attributed to the synergistic effect between alloyed Cu and Co.
In this paper, the process of ammonia borane (AB) hydrolysis generate H2 on the transition metal Fe@Co core-shell structure has been obtained. According to the different roles played by H2O molecules and the number of H2O molecules involved, there are three schemes of reaction paths. Route Ⅰ does not involve the dissociation of H2O molecules and all H atoms come from AB. Moreover, the H2O molecule has no effect on the breaking of the BH bond or the NH bond. The reaction absorbs more heat during the formation of the second and third H2 molecules. Route Ⅱ includes the dissociation of H2O molecules and the cleavage of BH or NH bonds, respectively, and the reaction shows a slight exotherm. Route Ⅲ started from the break of the BN bond and obtained 3H2 molecules through the participation of different numbers of H2O molecules. After multiple comparative analyses, the optimal hydrolysis reaction path has been obtained, and the reaction process can proceed spontaneously at room temperature.
The development of low-cost and highly efficient bifunctional electrocatalysts toward oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) is of critical importance for clean energy devices such as fuel cells and metal-air batteries. Herein, a sophisticated nanostructure composed of CoS, Co and MoC nanoparticles incorporated in N and S dual-doped porous carbon nanofibers (CoS/Co/MoC-N, S-PCNFs) as a high-efficiency bifunctional electrocatalyst is designed and synthesized via an efficient multi-step strategy. The as-prepared CoS/Co/MoC-N, S-PCNFs exhibit a positive half-wave potential (E1/2) of 0.871 V for ORR and a low overpotential of 289 mV at 10 mA/cm2 for OER, outperforming the non-noble metal-based catalysts reported. Furthermore, the assembled Zn-air battery based on CoS/Co/MoC-N, S-PCNFs delivers an excellent power density (169.1 mW/cm2), a large specific capacity (819.3 mAh/g) and robust durability, demonstrating the great potential of the as-developed bifunctional electrocatalyst in practical applications. This work is expected to inspire the design of advanced bifunctional nonprecious metal-based electrocatalysts for energy storage.
Hyperterpenoid A (1) and B (2), two pairs of enantiomers, with an unprecedented 6/6/4/6/6 polycyclic skeleton, along with one known compoud hypermonone A (3) were isolated from Hypericum beanii. The racemate (±)-1 and (±)-2 were successfully separated into the two optically pure enantiomers (ee ≥ 99%) using a preparative HPLC system. Their absolute configurations were elucidated by extensive spectroscopic analyses and single-crystal X-ray diffraction method. The related plausible biogenetic pathways were presented. Compound 1-3 showed significant neuroprotective activity and potential anti-inflammatory activity. The result that (+)-2 and (-)-2 presented different anti-inflammatory properties, may lead us to new discovery of structure activity relationship between racemates, enantiomers, and diastereomers, as well as further research regarding the binding of drugs to target proteins.
Lithium metal has a very outstanding theoretical capacity (3860 mAh/g) and is one of the most superior anode materials for high energy density batteries. However, the uncontrollable dendrite growth and the formation of "dead lithium" are the important hidden dangers of short cycle life and low safety. However, the uncontrollable dendrite growth and the formation of dead lithium leads to short cycle life and hidden danger, which hinder its practical application. Controlling the nucleation and growth process of lithium is an effective strategy to inhibit lithium dendrite. Herein, a simple in situ self-catalytic method is used to construct nitrogen doped carbon nanotube arrays on stainless steel mesh (N-CNT@SS) as a lithium composite anode. The N-doped CNTs provide a great number of N-functional groups, which enhance the lithiophilic of anode and provide a large number of uniform nucleation sites, hence it has excellent structural stability for cycles. The arrays provide neat lithium-ion transport channels to uniform lithium-ion flux and inhibits dendrite generation, revealed by the COMSOL multi-physics concentration field simulation. The N-CNT@SS composite anode sustain stable at 98.9% over 300 cycles at 1 mA/cm2. N-CNT@SS as the anode is coupled LiFePO4 (LFP) as the cathode construct a full battery, demonstrating excellent cycling stability with a capacity of 152.33 mAh/g and capacity retaining ratio of 95.4% after 100 cycles at 0.5 C.
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