Chemistry - An Asian Journal最新文献

A new approach for the synthetically important γ-functionalized enals has been developed. The strategy involves rhodium-catalyzed direct C-C & C-S bond forming site-selective γ-difunctionalization of diazoenals with aryl propargyl sulfides via sulfur ylide [2,3] sigmatropic rearrangement, resulting in the highly functionalized γ-allenyl(sulfanyl)enals in excellent yield at ambient temperature. This highly versatile approach constitutes a viable alternative to the remote carbonyl-directed γ-functionalization of unmodified enals which suffer from competitive side reactions. The synthetic utility of the γ-allenyl(sulfanyl)enals was demonstrated by the InCl₃-catalyzed cycloisomerization to the trisubstituted furanyl-enals via an unusual 1,4-sulfanyl migration. In addition, an operationally simple and efficient one-pot [3+2] annulation of diazoenals and propargyl sulfides, involving combined γ-difunctionalization and cycloisomerization was successfully developed for the diverse enal-functionalized furans.

In the context of chiral π-conjugated materials, the use of enantiopure alkylthio appendages represents a valid alternative to conventional alkoxy groups: sulphur atom is bigger and more electron-rich than oxygen, thus allowing for higher polarizability, greater flexibility, larger bulkiness and lower structural anisotropy. In light of these considerations, here we report two new chiral alkylthio-decorated 1,4-phenylene/thiophene dyes, obtained by simple synthetic strategies involving Pd-catalyzed cross-coupling protocols, looking for strong non-reciprocal chiroptical features in thin films. In particular, for the chiral alkylthio-decorated 1,4-phenylene-bis(thiophenylpropynone) (Thio-PTPO) dye, which proved to be the most promising for our purpose, a detailed investigation in thin films was carried out, involving optical and chiroptical spectroscopies in absorption and emission, as well as optical microscopy techniques.

Isolated Ti(IV)-zeolites have been rationally designed. The different aluminium topological densities of various zeolite frameworks lead to the creation of different degrees of vacant sites for hosting Ti(IV) active sites. The more vacancies in the host zeolite structure, the more isolated tetrahedrally coordinated Ti(IV) can be increased, especially in the BEA framework, eventually enhancing the catalytic performance in methyl oleate epoxidation towards methyl-9,10-epoxystearate. More details can be found in article number e202400669 by Chularat Wattanakit, and co-workers.

Pure silica ITH zeolite is normally synthesized under neutral or acidic conditions in the presence of HF, but it is challenging for synthesis of this zeolite under alkaline conditions. In this work, it is successful for alkaline synthesis of pure silica ITH in the absence of HF using a designed organic template containing F species, showing that the sample obtained has high crystallinity associated with ITH structure, nanosheet morphology, and rich silanol nests. Very importantly, this ITH zeolite exhibited better performance in vapor phase Beckmann rearrangement of cyclohexanone oxime than that of Silicalite-1 zeolite, one of the best catalysts for this reaction. This work might offer a new opportunity for preparation of pure silica zeolites as efficient catalysts in the Beckmann rearrangement in the future.

A mild, regiospecific Gold-Silver bimetallic catalytic system has been devised for the intramolecular hydroacyloxylation and hydroetherification of alkenoic acids and alcohols. This method exhibits precise specificity for the geminal substituted olefinic center and facilitates the synthesis of substituted phthalide and hydroisocoumarin derivatives. This method has been effectively applied for late-state functionalization to produce bioactive natural products such as rumphellaone A, mycophenolate, and (-)-ambrox. The successful gram-scale synthesis of the anticonvulsant, hypnotic drug (±)-ethyl phenyl butyro lactone (EPBL), (±)-Boivinianin A and the ability to synthesize challenging spiro and bicyclic lactone underscores the synthetic potential of this methodology. Mechanistic insights into gold-silver catalyzed lactonization of olefins have also been discussed.

Porous organic polymers (POPs) are a type of porous material composed of organic structural units connected by covalent bonds and POPs have been used as efficient electrocatalysts for hydrogen evolution reaction (HER). Herein, glassy carbon electrode (GCE) is chemically modified by B-doped imidazolium-based porous organic polymers loaded with Ru nanoparticles on the GCE surface. The incorporation of B in the POPs regulates the electronic structure of electrocatalysts to enhance their inherent electrocatalytic activity for HER. The optimized modified electrode GCE-Ru/PIM-Br2 exhibits a low overpotential of 271 mV at a current density of 10 mA cm^-2 with a small Tafel slope (80 mV dec^-1) in acidic solutions, and shows long-term stability for up to 22 h. This work presents a strategy to develop B-doped porous electrodes with loaded metal nanoparticles to strengthen the catalytic performance of electrocatalysts.

Solar-energy-driven photocatalytic CO₂ reduction by H₂O to high-valuable carbon-containing chemicals has become one of the greatest concerns in both scientific and industrial communities, due to its potential in solving energy and environmental problems. However, efficiency of photocatalytic CO₂ reduction by H₂O is still far below the needs of large-scale applications. The reduction efficiency is closely related to ability of photocatalysts in absorbing visible light which is the main part of sunlight (44 %), separating photogenerated electron-hole pairs, adsorbing CO₂ and producing protons for reducing CO₂. Thus, photocatalysts with enhanced visible light absorption, electron-hole separation, CO₂ adsorption and proton production are highly desired. Herein, we aim to provide a picture of recent progresses in improving ability of photocatalysts in visible light absorption, electron-hole separation, CO₂ adsorption and proton production, and give an outlook for future researches associated with photocatalytic CO₂ reduction by H₂O.

Proteins are generally resistant to large conformational changes under physiological conditions. Here, we show that platinum (Pt(II)), which is widely-used metal centre in cancer therapeutic drugs, binds to a cytosolic protein, small ubiquitin-like modifier 1 (SUMO1), under physiological conditions and changes its conformation to a molten globule (MG). Mass spectrometry (ICP-MS) studies confirmed stoichiometric Pt(II) binding to SUMO1. Fluorescence spectroscopy showed Tyr fluorescence quenching and increased ANS binding. Fluorescence assays on Trp-mutants indicated conformational changes and circular dichroism (CD) suggested MG formation upon Pt(II) binding. In contrast, structural homologues of SUMO1 (ubiquitin (Ubq) and SUMO2) showed no conformational changes on Pt(II) titration. Further studies compared the impact of distinct His residues in SUMO1 on Pt(II) binding and protein structure to SUMO2 and Ubq. Experiments at low pH (5.0) implicated His residues interacting with Pt(II), corroborated by the absence of conformational change in the H75L mutant of SUMO1. Pt(II)-His binding in SUMO1 unravels key molecular determinants of Pt(II)-protein interactions and their conformational consequences. SUMO1 with other SUMOylation components are shown to have enhanced expression in several cancers, hence, our study suggests a possible fate of the non-targetability of Pt(II)-based drugs on SUMOylation in cancer cells, upon interaction with SUMO1.

A photopromoted Pd-catalyzed Heck reaction of gem-difluorocyclopropyl bromides (DFCBs) with styrenes to deliver vinyl gem-difluorinated cyclopropanes (VDFCs) under mild conditions has been developed. The reaction demonstrates good functional group compatibility while providing high E/Z ratio of the products. Furthermore, the desired VDFCs can be easily transformed into fluorinated cyclic/acyclic architectures, which may broaden its applications in organic synthesis.

In this study, we have synthesized two zinc(II)-based metal-organic frameworks (MOFs) designated as [Zn(4-nvp)(bdc)] ⋅ (MeOH) (1) and [Zn₂(4-nvp)₂(bpdc)₂] ⋅ (DMF) (2) [4-nvp=4-(1-naphthylvinyl) pyridine, H₂bdc=1,4-benzendicarboxylic acid and H₂bpdc=4,4'-biphenyldicarboxylic acid]. Single-crystal X-ray diffraction (SCXRD) of both compounds unveiled an interesting paddle-wheel [Zn₂(O₂C-C)₄] secondary building block (SBB) composed of dinuclear Zn (II) centers and four dicarboxylate groups with a (4,4) square grid topology. These SBBs are interconnected giving rise to an infinite 2D layer architecture. Notably, the grid structure is composed of MeOH molecules in compound 1 and DMF molecules in compound 2, both of them arranged in a free lattice. In both compounds, 3D supramolecular architecture is ultimately formed through the stacking of 2D layers. Since the length of the bpdc ligand is higher than that of the bdc ligand, the solvent-accessible void volume is comparatively higher for compound 2. To corroborate all non-bonded interactions, Hirshfeld analysis was carried out for synthesized compounds. DNA binding application was extensively investigated through docking study. Results indicated that the synthesized compounds have strong affinities towards DNA via DNA groove binding. Henceforth, the synthesized compounds 1 and 2 would open the door for their potential applications as particular protein binders and bioactive substances.