Chemistry - A European Journal最新文献

We have explored the reactions of a three-components mixture made of formamide, diaminomaleonitrile, and glycine, with meteorites as catalysts and high-energy proton beam irradiation as the energy source, mimicking the solar wind. The resulting mixture contained a wide array of biogenic compounds, including the complete set of RNA nucleobases and nucleosides, thymine and its analogs, pterins, triazines, carboxylic acids, diketopiperazines, hydantoins, N-carboxyamino acid anhydrides, amino acids, peptides, and nucleobase-amino acid/peptide conjugates. It also embodies the possibility of synthesis stability of RNA-peptide chimeras onto which evolution to the extant molecular genetic system could start. The prebiotic worth of the system consists of the fact that formamide derives from HCN hydrolysis; glycine is a condensation product of formamide and HCN; diaminomaleonitrile is obtained from HCN. The fact that the starting mixture is three-component does not decrease the prebiotic value; it is a subset of a largely possible general universal condition: all the starting components are only the second step of facile condensation reactions. This model could be the starting point for the chemical evolution towards biological complexity.

Palladium/norbornene (Pd/NBE) cooperative catalysis is widely regarded as an effective strategy for constructing polysubstituted arenes, providing a rapid and efficient route that is often difficult to accomplish using traditional cross-coupling methods. This review focuses on applying Pd/NBE cooperative catalysis to the functionalization of nonaromatic systems, referred to as the alkenyl Catellani reaction. The nonaromatic substrates discussed include uracil, 2-quinolone, 2-pyridone, alkene, coumarin, chromone, glycal, and 1,2-azaborine, all of which generate a broad range of functional alkenes. In addition, this review outlines developments in asymmetric alkenyl Catellani reactions and highlights their use in the total synthesis of structurally complex molecules.

Mechanochemistry has emerged as a cornerstone of sustainable synthesis, providing an energy-efficient, solvent-free alternative to conventional solution-phase methodologies while minimizing environmental impact. Despite increasing application of mechanochemical approaches for preparing diverse organic compounds, the extension of these strategies to the synthesis of covalent organic frameworks (COFs) is limited up to now. Notably, the mechanochemical synthesis of multicomponent reaction-derived COFs (MCR-COFs) has not been previously reported. Herein, we demonstrate solvent-free mechanosynthesis of MCR-COFs through a three-component Povarov cascade reaction, efficiently combining aldehydes, amines, and phenylacetylenes with tert-butyl peroxybenzoate as the unique oxidant under one-pot ball-milling conditions. The resulting frameworks exhibit exceptional structural regularity, manifested by high crystallinity and well-defined permanent porosity with surface areas reaching 1371.6 m²/g. Intriguingly, the mechanosynthesized MCR-COFs exhibit a different stacking mode from the traditional solvothermal counterparts. Remarkably, these mechanosynthesized COFs can be applied to solvent-free mechanochemical reaction for the first time. This work establishes a paradigm shift in COF synthesis by merging the sustainability benefits of mechanochemistry with the accuracy of three-component cascade synthesis, while simultaneously advancing the catalytic applications of COF materials through mechanochemistry.

The fluorescence sensing method based on lanthanide metal-organic frameworks (Ln-MOFs) offers high sensitivity, selectivity, and rapid, real-time detection of biogenic amines (BAs). However, their high cost, complex synthesis, and unclear sensing mechanism limit practical application. Herein, waste polyimide is utilized as a precursor to synthesize Eu-1,2,4,5-benzenetetracarboxylic acid (Eu-BTEC) via a two-step hydrothermal-solution method. Under optimum conditions, the obtained Eu-BTEC exhibits excellent fluorescence selectivity and sensitivity toward cadaverine, with an apparent constant of 1.58 ×10⁶ L·mol^-1 and a detection limit of 0.17 µmol·L^-1. Density functional theory calculations reveal that the amino groups of cadaverine donate electrons to Eu³⁺, blocking the intramolecular electron transfer from the benzene ligand to Eu³⁺. Owing to the absence of chromophores in cadaverine, this electron transfer leads to luminescence quenching of Eu-BTEC. To achieve visual and portable detection, Eu-BTEC-based fluorescence test strips were fabricated by spraying its suspension onto filter paper, enabling visual quantification of cadaverine (0.50 µmol·L^-1) under UV light. This study not only provides a sustainable route for converting waste polyimide into Ln-MOFs but also elucidates the BA sensing mechanism through HOMO-LUMO band-gap and electron-density analyses, offering new insights into the fluorescence quenching process of Ln-MOFs.

Self-immobilizing near-infrared (NIR) fluorogenic probes based on hemicyanine dyes show great promise for in vivo imaging due to their superior retention efficiency at target sites. However, their broader development and application have been hampered by tedious synthetic routes and insufficient understanding of how structural variations govern performance in complex biological systems. Herein, we report a versatile and efficient late-stage condensation strategy that provides easy access to a series of self-immobilizing hemicyanine dyes, enabling the first systematic comparison between 5- and 7-regioisomers. Although both probes showed strong fluorogenic responses to alkaline phosphatase in vitro, there in vivo behavior differed remarkably. Unexpectedly, the 5-substituted probe (P5) exhibited significantly lower tumor retention and imaging contrast in live mice than the 7-substituted analogue (P7). Density functional theory (DFT) calculations and mechanistic studies attributed this divergence to the higher reactivity and slower formation kinetics of the quinone methide intermediate generated from P5, leading to nucleophilic attack by water and rapid diffusion from the detection site in highly dynamic in vivo environments. This study not only offers a practical synthetic route but also establishes regiochemical tuning of QM reactivity and formation kinetics as a crucial design strategy for developing imaging agents suited for in vivo applications.

As a broad-scale energy storage solution, redox flow batteries (RFBs) offer high efficiency and tunable design. However, conventional RFBs rely on transition-metal ion couples, (e.g., vanadium or iron), whose implementation is limited by low energy densities, high cost, and environmental leaching. Main-group compounds, comprising earth-abundant, p-block elements, represent highly promising, yet underexplored candidates for RFBs. Herein, we evaluate three boron-formazanate complexes as negolyte and symmetric electrolytes in nonaqueous organic redox flow batteries (NAORFBs). Detailed electrochemical characterization of these complexes reveals two sequential reduction processes with the first being exceptionally stable (<3% capacity fade after charge/discharge cycling in a static H-cell for 3 days). In contrast, cycling that includes the two-electron reduced state results in rapid degradation (>59% capacity fade over 2.5 days in a static H-cell), most likely due to fluoride elimination from the BF₂ moiety. Guided by these insights, a B(Ph)₂ unit was introduced to mitigate this degradation pathway. The elimination of labile B─F bonds as well as steric protection conferred by two phenyl groups led to improved cycling performance (>85% capacity retention after charge/discharge cycling in a flow battery for 15 days). These findings guide the rational design of inexpensive main-group electrolytes for application in energy storage.

Mechanochemistry has attracted significant attention as a sustainable and efficient alternative to solution-based synthesis, offering the advantage of solvent-free conditions or the use of only minor amounts of solvent. Many established mechanochemical transformations rely on the use of additives-a strategy broadly referred to as additive-assisted grinding. The most employed additives are liquids (liquid-assisted grinding (LAG)), ionic solids, and non-ionic additives. Additionally, ionic liquids (ionic liquid-assisted grinding (IL-AG)), piezoelectric, or mechanoluminescent materials can be used. This review provides an overview of additive-assisted organic synthetic transformations under mechanochemical conditions, highlighting the roles, advantages, and limitations of additives, as well as emerging trends from recent literature.

We report two enantio- and diastereodivergent transformations based on a one-pot relay catalysis strategy. Chiral cyclohexenecarbaldehydes, diastereomeric to the products of Enders' seminal triple domino reaction, were synthesized with excellent enantioselectivity using two structurally related chiral catalysts in a sequential fashion. While the anti-isomer was obtained via a one-pot Michael/Mannich reaction catalyzed by a single chiral catalyst, the complementary syn-isomer was selectively accessed through sequential addition of two distinct catalysts in a single vessel. In most cases optically pure products were obtained. This one-pot relay catalysis strategy enables access to complementary stereoisomers and represents a valuable alternative to traditional domino reactions and single-catalyst one-pot processes involving independent catalytic cycles.

In the search for alternatives to platinum anticancer drugs, palladium complexes have attracted considerable interest. In this frame, six square planar palladium(II) complexes with the general formula [PdAB₂] were prepared, where the ligand A is (1R,2R)-diaminocyclohexane (DACH) or 1,10-phenanthroline (Phen), and the ligand B is chlorine, iodine, or pyridine. The biological properties of the investigated compounds were systematically evaluated to identify trends linked to ligand variations. The complexes were synthesized following established experimental procedures and characterized by elemental analysis and NMR spectroscopy. DNA interactions were investigated through melting experiments and the ethidium bromide (EB) displacement assay. The obtained data suggested covalent adduct formation as the preferential binding mode for the DACH-containing complexes, whereas intercalation was predominant for the phenanthroline-based complexes. Notably, at least one compound appears to interact with DNA through both modes. Cytotoxic activity was evaluated against three human ovarian cancer cell lines (A2780, A2780R, and SKOV3) as well as a healthy control cell line (HSkM, human skeletal myoblasts). Significant cytotoxic activity was observed for the Phen-containing complexes, with compound 3 also showing a good selectivity index. Conversely, DACH-containing complexes were found to be non-cytotoxic.

Cyanoarene photocatalysts such as 3DPAFIPN are widely employed in visible-light-driven transformations, yet their intrinsic structural dynamics under irradiation remain poorly understood. Here we reveal that 3DPAFIPN undergoes light-induced reconfiguration into distinct cyclized and radical substitution products, with the parent species ultimately decomposing under reaction conditions. Using a combination of Photo-Chem-ESI-MS and TLC-mapping, we directly monitored the evolution of catalytic forms and identified the cyclized derivatives as the true active species in thiol-yne-ene coupling. The major cyclized product was isolated and structurally confirmed by single-crystal X-ray diffraction, providing unambiguous experimental evidence for light-driven photocatalyst reconfiguration. Compared with the precursor, the cyclized catalysts display enhanced stability against cyanide substitution by radical intermediates and deliver higher efficiency and selectivity. This study establishes a generalizable workflow for dissecting dynamic photocatalyst behavior and extends the ReAct-Light concept, highlighting light-triggered structural evolution as a new design principle for adaptive and robust photocatalytic systems.