Latest ArticlesThe first synthesis, characterization, and hydride reduction reactions of a series of PNP-pincer ligand supported molybdenum and tungsten carbyne complexes [(PNP)M(≡CAr)X(CO)] [M = Mo, W; PNP = Ph2P(CH2)2N(CH3)(CH2)2PPh2, R2P(CH2)2N(H)(CH2)2PR2, R = Ph, Cy] are reported. Treatment of [(PNP)M(≡CAr)X(CO)] with LiAlH4 led to full reduction of the carbyne carbon, giving PP-bidentate η6-arene molybdenum and tungsten complexes. Alternatively, when NaBH4 was used as a reductant, the carbyne ligand completely dissociated from the molybdenum center to yield toluene and dimolybdenum biscarbonyl complex [(PNP)Mo(CO)]2. These PNP-pincer molybdenum and tungsten carbyne complexes showed unique reactivity with hydride reagents preferably at the carbyne carbons, in contrast to the metal centers of non-pincer molybdenum and tungsten carbyne complexes in previous reports.
A neutral Diels-Alder reaction lacking enough electronic bias typically requires forcing conditions to proceed owing to the enlarged energy gap between HOMO and LUMO. We herein report an electrophotocatalytic decarbonylative [4 + 2] cyclization of indenones under mild reaction conditions for facile access toward various benzo[c]fluorenones. Mechanistic investigations revealed that this reaction first underwent photocatalytic decarbonylative [4 + 2] cyclization followed by an electrocatalytic oxidation. Consistent with their photophysical properties and DFT calculations, the obtained benzo[c]fluorenones displayed remarkable photocatalytic activity both in the current electrophotocatalytic decarbonylative [4 + 2] cyclization of indenones and in the oxidation of benzhydrol.
Hypoxic-ischemic encephalopathy (HIE) is a major cause of infant mortality and permanent neurological abnormalities, highlighting the importance of early identification and accurate diagnosis. Fluorescence sensing provides various benefits over traditional diagnostic methods, including real-time detection of hypoxia, which is often linked to HIE, and molecular-level insights. Herein, a novel hypoxia-responsive fluorescent probe, BOD, was created to overcome the difficulties associated with blood–brain barrier (BBB) penetration for brain damage imaging using a HIE model. BOD can be cleaved by azoreductase to produce a red fluorescent signal, with excellent sensitivity, selectivity, and biocompatibility. Crucially, BOD effectively monitors neural cells across varying oxygen concentrations, particularly in hypoxic microenvironments, providing vital insights into the impact of oxygen deprivation on neural cell function during HIE. In both cellular and ex vivo mouse brain tissue models, the effectiveness of BOD was confirmed: it outperformed conventional techniques in the reliable identification of hypoxic injury sites, differentiating between mild, moderate, and severe injury. Thanks to its excellent permeability due to its lipophilicity and positive charge, BOD can pass through the BBB, with strong fluorescence in the periventricular white matter (PWM) and cortex strongly correlated with injury severity. This study is novel in its application of a hypoxia-responsive fluorescent probe for brain damage imaging in an HIE model, highlighting the substantial potential of BOD for real-time, in vivo imaging, representing a promising tool for early diagnosis and investigation of HIE.
Nitrile oxide is a highly reactive species used for organic synthesis and bioconjugation. Herein, we developed a novel approach for disulfide formation and capping of N-terminal cysteine in peptides mediated by bromo nitrile oxide. 1,1-Dibromoformaldoxime acts as the precursor for bromo nitrile oxide. This transformation proceeds under mild conditions with rapid kinetics, efficiently converting a broad range of thiophenols, thiols, and cysteine-containing native peptides into disulfides, cyclic disulfides, or thiazolidin-2-one oximes. Notably, oxidant-sensitive residues such as methionine, tyrosine, and tryptophan are well tolerated without over-oxidation. The compatibility with aqueous media further highlights its potential for the late-stage modification of native peptides and the derivatization of biologically active molecules.
Polycyclic heterocycles are prevalent in medicines, functional materials and natural products, making their synthesis a significant focus in modern organic chemistry. Herein, we present a Lewis acid-mediated cascade annulation of 1,6-enynols with o-aminobenzonitriles for the chemoselective synthesis of oxepino[3,4,5-de][1,6]naphthyridine and chromeno[2,3,4-de][1,6]naphthyridine derivatives. This reaction design enables selective control over the carbon-heteroatom and carbon-carbon bond formation in an efficient, atom-economical manner, allowing the one-step synthesis of rare [6-6-7] and [6-6-6] core polycyclic heterocycles containing three heteroatoms. Density functional theory (DFT) calculations and control experiments reveal that the reaction's high selectivity is achieved by modulating the reactivity of electron-rich alkenyl groups in the enynols, which selectively directs the intramolecular dehydroaromatization and cyclization processes.
Nanographenes (NGs) incorporating N-doped heptagonal units demonstrate intriguing physicochemical properties, attributed to their negatively curved structure induced by the angular strain of the heptagons and the electronic effects of nitrogen atoms, while their precise synthesis remains a challenging task. Herein, we developed an efficient approach for the construction of azepine-embedded NGs via two-fold SNAr/gold(I)-catalyzed 7-endo-dig annulation from commercially available 4,7-dibromo-5,6-difluorobenzo[2,1,3]thiadiazole. The fusion of two heptagonal rings dramatically increases the intramolecular strain and forces the central skeleton to twist, giving rise to a unique packing mode in the crystal. The incorporation of thiadiazole leads to a pronounced bathochromic shift in the fluorescence emission, which causes the typical product to display NIR-emission. Furthermore, it is found that the backbone core of these NGs with thiadiazole exhibits excellent single-molecule conductivity as well.
In this work, a periodically ordered cruciform DNA nanowire (POCDN) guided-localized hybridization chain reaction (LHCR) was designed for the simultaneous and rapid detection and imaging of dual-miRNAs in cancer cells. In the presence of the targets miRNA-21 and miRNA-155 associated with breast cancer, the hairpins on both sides of the DNA nanowire were opened to undergo a LHCR, and the trace amount of the target miRNAs were converted into numerous 5-carboxyfluorescein (FAM) and Cy5 signals, which in turn enabled the simultaneous and sensitive detection and visualization of dual-miRNAs targets in malignant tumor cells. Impressively, folic acid (FA) labelled on the structural backbone of DNA nanowires could be specifically targeted to malignant tumor cells with overexpressing the folate receptor, which greatly improved the efficiency of delivery into the cell and enabled precise imaging of intracellular miRNAs without the liposomal transfection. Compared with conventional hybridization chain reaction (HCR), the POCDN-guided LHCR confined the reactants in a compact space, greatly improving the sensitivity of the assay and the reaction rate, with a 5.3-fold reduction in reaction time to just 5 min and detection limits as low as 0.97 and 0.58 pmol/L for miRNA-21 and miRNA-155, respectively. This strategy provides a programmable platform for simultaneous rapid and sensitive detection and precise visualization of multi-miRNAs with eventual applications in bioanalytical studies and potential for future clinical diagnostics of diseases.
Over the past decades, vinyl cations have been developed as versatile synthetic intermediates in organic chemistry, that allow the construction of various C–C and C–X bonds. However, the catalytic enantioselective transformation of vinyl cations remains one of the major challenges in asymmetric catalysis, especially for the organocatalytic enantioselective reaction. Herein, we report a chiral Brønsted acid-catalyzed atroposelective reaction of vinyl cations by combining organocatalytic diyne cyclization with C(sp2)–H functionalization of diphenols. The effective chiral induction model of vinyl cations enables the streamlined synthesis of axially chiral acyclic tetrasubstituted alkenes with the simultaneous control of chemoselectivity, regioselectivity, E/Z selectivity and enantioselectivity. Further derivatizations and applications demonstrate the potential utility of constructed axially chiral skeletons in asymmetric catalysis. Computational mechanistic studies reveal the reaction mechanism and origin of selectivities. Notably, this protocol represents the first organocatalytic asymmetric intermolecular reaction of vinyl cations, as well as the first organocatalytic enantioselective diyne cyclization.
Heck/Tsuji-Trost reaction and cyclization reactions have been established as efficient and practical strategies for constructing nitrogen-containing heterocyclic compounds. However, it is challenging to achieve a direct cascade of Heck/Tsuji-Trost and 6-endo cyclization reactions in one-pot synthesis, primarily due to the reactivity of intermediates and the regioselectivity control of the reaction. In this work, a palladium-catalyzed, Heck/Tsuji-Trost and 6-endo cyclization tandem reaction of aryl iodides, vinylacetic acid, and aryl amines has been developed, providing an effective approach for one-pot synthesis of substituted quinolines in moderate to good yields. The broad functional group tolerance, high regioselectivity, gram-scale experiments, and successful late-stage modification of natural products and pharmaceuticals proved the versatility and practicality of this method. Additionally, mechanistic experiments demonstrate that the branched amination product serves as a key intermediate in this reaction.
A novel thia[8]helicene (BN[8]H) with B, N heteroatoms incorporated in the molecular skeleton was synthesized via Suzuki coupling reaction and intramolecular direct electrophilic C-H borylation. Its helical structure was confirmed by X-ray crystal analysis. Enantiomers BN[8]H showed the interesting responses to fluoride ion stimulation with novel sign inversion of electronic circular dichroism (ECD) and circularly polarized luminescence (CPL). TD-DFT calculations revealed that the fluoride ions significant influence the transition dipole moments and θu,m, resulting in circularly polarized luminescence reversal.
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