Chemistry - An Asian Journal最新文献

Nitrogen-containing compounds are ubiquitous in pharmaceuticals, agrochemicals, and functional materials, and the development of sustainable methodologies for carbon-nitrogen (C─N) bond formation is of fundamental importance. Herein, we report a rationally designed bifunctional ligand and micellar cooperativity that effectively enables Cu-catalyzed amination of aryl bromides under mild aqueous conditions. A series of structurally tailored ligands was designed by systematically tuning their electronic and steric properties to stabilize the active copper catalyst and promote selective C─N bond formation. When combined with the bio-derived non-ionic surfactant CNSL-1000-M, the micellar environment provides a confined hydrophobic reaction space, enhancing catalyst performance and substrate activation. This cooperative ligand-micelle system enables the C─N coupling with both electron-rich and electron-deficient aryl bromides at 60°C, affording the corresponding aryl amines in good to excellent yields. The active Cu catalyst was thoroughly characterized by UV-visible spectroscopy, x-ray photoelectron spectroscopy (XPS), and Electron Paramagnetic Resonance (EPR). It is worth noting that our current catalyst system shows better catalytic activity and selectivity than conventional organic solvents such as DMF, 1,4-dioxane, DMSO, and toluene. This study demonstrates that electronic, steric, and micellar cooperativity play decisive roles in aqueous copper-catalyzed reactions and establishes a practical, sustainable platform for C─N cross-coupling reactions.

Metal complexes are emerging as powerful agents in light-activated cancer therapy, a cutting-edge therapeutic strategy for combating cancer and other serious diseases. Among them, iridium (Ir)-based photosensitizers have recently gained significant attention, driving innovation in photo-activated cancer therapy and opening new avenues for targeted treatment. Building on this momentum, we have designed a novel benzimidazole-based iridium complex, [LIr], which demonstrates remarkable potential as a phototherapeutic agent. Upon activation with a direct light source from a 40 W white LED (400-700 nm), with a fixed distance of 15 cm between the light source and the samples maintained throughout all the experiments, [LIr] exhibits potent catalytic activity, efficiently oxidizing key cellular antioxidants: converting glutathione (GSH) to glutathione disulfide (GSSG), NADH to NAD⁺, and NADPH to NADP⁺. This redox disruption compromises cancer cell defenses and enhances therapeutic efficacy. In addition, light activation of complex [LIr] generates a burst of reactive oxygen species (ROS), including the highly cytotoxic singlet oxygen, with a notable singlet oxygen quantum yield. This multifaceted reactivity not only disrupts cellular redox balance but also induces oxidative stress in targeted cancer cells.

Catalytic hydroboration of N-heteroarenes and imines represents an attractive and sustainable strategy for accessing a broad range of synthetically valuable nitrogen-containing compounds. Herein, we disclose the metal-free catalytic activity of bicyclic (alkyl)(amino)carbene (BICAAC) (I) toward the hydroboration of N-heteroarenes and imines using pinacolborane (HBpin). The catalyst exhibits excellent regioselectivity, promoting 1,4-hydroboration of pyridines and 1,2-hydroboration of quinolines, while efficiently reducing a variety of imines under mild reaction conditions. Mechanistic investigations, based on a series of control experiments, reveal that the reaction is initiated by the addition of the B─H bond of HBpin across the carbene center to generate the catalytically active BICAAC-borane species (II). This intermediate activates the substrate through a Lewis acid-base interaction between the boron center and the nitrogen atom of the substrate, followed by hydride transfer from a second equivalent of HBpin to afford the hydroborated products. This work significantly expands the scope of BICAAC organocatalysis and demonstrates its potential as an efficient metal-free catalyst for the reduction of challenging nitrogen-containing unsaturated substrates.

Lowering temperatures provides an effective strategy for probing rapid protein dynamics. However, conventional nuclear magnetic resonance (NMR) measurements are usually limited to temperatures above 0°C due to water freezing and increasing rotational correlation times. In this study, we report subzero-temperature NMR analysis enabled by encapsulating a protein within spherical coordination cages. Spatial confinement within the metallo-cages stabilizes proteins by preventing aggregation, enabling multi-dimensional NMR measurements of a 20 kDa protein at temperatures as low as -30°C in low-viscosity acetone-water mixtures. Below 0°C, the NMR spectra of the protein revealed markedly slowed dynamics, resolving two distinct conformations as split signals. Furthermore, the subzero-temperature analysis enabled detection of exchangeable hydroxy protons that are unobservable at ambient temperatures. Saturation transfer difference (STD) NMR revealed binding of carbohydrate hydroxy groups to lysozyme, owing to the large apertures of the cages, which permit ligand diffusion while the cages stabilize proteins under subzero conditions. This cage confinement thus facilitates the study of rapid protein dynamics and ligand binding beyond the limits of conventional solution NMR.

An efficient intramolecular hydride-transfer cyclization process in aqueous CTAB media for the reaction of ortho-aminobenzaldehydes with active methylene cyanoacetamide compounds enabling the synthesis of diverse tetrahydroquinoline cyanocarboxamide derivatives has been achieved. The method offers good yields and diastereoselectivity, operational simplicity, large-scale synthesis, high atom- and step-economy, and excellent functional group tolerance. Further, this methodology works well with glycine, malononitrile, ethyl cyanoacetate, and barbituric acid as active methylene compounds.

To investigate the effects of oligo(ethylene glycol) (OEG) chain length and thermal factors on the formation of self-assembled monolayers (SAMs), the surface structure, adsorption state, and electrochemical stability of SAMs of 2-[2-(2-methoxyethoxy)ethoxy]ethanethiol (EG3 SAMs) on Au(111) at an elevated temperature were examined using scanning tunneling microscopy (STM), x-ray photoelectron spectroscopy (XPS), and cyclic voltammetry (CV). To gain a clearer understanding, the results for EG3 SAMs were directly compared with those observed for decanethiolate (DT) SAMs. STM observations revealed that DT SAMs formed after deposition at 323 K for 2 and 24 h exhibited a well-ordered c(4 × 2) phase regardless of the deposition time, whereas EG3 SAMs at 323 K for 2 h displayed a mixed morphology of ordered and disordered phases containing brightly aggregated rows. After deposition at 323 K for 24 h, the brightly aggregated rows almost disappeared and more uniformly ordered SAMs were formed on the entire Au (111) surface. Moreover, CV measurements showed that EG3 SAMs are reductively desorbed from the Au surface much more easily than DT SAMs. In this study, we clearly demonstrated that the OEG backbone significantly affects the formation, surface structure, thermal behavior, and electrochemical stability of SAMs.