Search Results (284)

The Sakurai reaction constitutes a valuable tool for carbon–carbon bond formation. The use of nontoxic allylic reagents as well as the atom economy of the global process has prompted the development of enantioselective (aza)-variants based on the use of chiral organo- and metal catalysts. This review collects the recent developments in catalytic enantioselective Sakurai reactions published since the beginning of 2011, including methodologies based on the use of chiral organocatalysts, metal/boron catalysts and multicatalyst systems. It is divided into three parts, dealing successively with enantioselective organocatalytic (aza)-Sakurai reactions, enantioselective metal/boron-catalyzed Sakurai reactions and enantioselective multicatalyzed (aza)-Sakurai reactions. It shows that, although still widely developed with aromatic aldehydes, the enantioselective catalytic Sakurai reaction has considerably matured in the last decade. Full article

G-quadruplex (G4) DNAzymes, guanine-rich sequences that fold into four-stranded structures and bind hemin to mimic peroxidase activity, are widely used in biosensing. Split G4 DNAzymes offer conditional activation upon target recognition, enabling high specificity and modularity. However, achieving low OFF-state leakage remains a major challenge. Here, we systematically characterized four representative G4 scaffolds, C-myc, Bcl2, PS5.M, and C-kit, under standardized ABTS/H₂O₂ conditions to assess their kinetic properties and suitability for split designs. C-myc exhibited the highest sustained activity and near-linear concentration dependence, making it ideal for quantitative sensing, while Bcl2 showed durable catalysis suited for extended read windows. C-kit produced rapid bursts with early plateaus, favoring binary outputs, and PS5.M initiated quickly but inactivated rapidly, suggesting potential application of systems requiring fast response. Split-mode analysis revealed that symmetric 2:2 partitions often retained significant activity, whereas asymmetric 3:1 splits reduced but did not eliminate leakage. Among the four G4 DNAzymes, PS5.M demonstrated the most promising OFF-state suppression. Design strategies to minimize leakage including non-classical splits, loop/flank edits, and template-assisted assembly could be used to optimize biosensor functionalities. These findings identify essential factors critical for designing robust split DNAzyme biosensors, advancing applications in diagnostics and molecular logic gates. Full article

The increasing generation of biomass-derived waste has accelerated the development of sustainable strategies for its valorization into functional materials. Activated carbon (AC), due to its high surface area, tunable porosity, and chemical versatility, has emerged as a key product for applications in adsorption, catalysis, energy storage, and biosensing, among others. Recent studies have highlighted the importance of symmetry and asymmetry in determining the structural and functional performance of AC. Symmetric architectures, typically generated via templating methods, yield ordered pore networks, whereas asymmetric structures, commonly produced through direct chemical activation or heteroatom doping, exhibit hierarchical porosity and heterogeneous surface functionalities. This work critically examines the fundamentals of symmetry and asymmetry in AC materials, as well as their influence on design and use. It discusses synthesis strategies, characterization techniques, and recent approaches that enable the rational engineering of carbon structures. Application-specific case studies are presented, along with current challenges related to feedstock variability, scalability, and regulatory integration. By highlighting the interplay between structural order and functional diversity, this work provides a conceptual framework for guiding future research in the development on symmetrical and asymmetrical carbonaceous materials for sustainable waste valorization. Full article

4,5-Dihydro-2H-pyridazin-3-ones (DHPDOs) are important synthetic as well as naturally occurring heterocycles. We herein report the synthesis of various 4-monofunctionalized 4,5-dihydro-2H-pyridazin-3-ones and their use as starting materials to access 4,4-disubstituted dihydropyridazin-3-ones in an asymmetric fashion. By using chiral ammonium salt phase-transfer catalysts, conjugate additions of these scaffolds to classical acrylate-based Michael acceptors, as well as quinone methides, can be carried out with moderate to good enantioselectivities and in reasonable yields, affording a new pathway to dihydropyridazin-3-one derivatives with an all-carbon stereocenter. Full article

This study researches the underexplored potential of the palladium-catalyzed Hayashi–Miyaura reaction in asymmetric synthesis, focusing on the preparation of novel derivatives of 2,2-diaryl-1-nitroethanes. These compounds are of interest as potential building blocks in medicinal and materials chemistry, yet they remain largely unexamined in enantioselective transformations. The study specifically targets three challenging substrates: 1,3-dimethoxy-5-(2-nitro-1-(o-tolyl)ethyl)benzene, 2-(2-nitro-1-phenylethyl)phenol, and 4-(2-nitro-1-phenylethyl)phenol. These molecules were selected to probe the reaction’s tolerance toward ortho-substitution and free hydroxyl groups—features known to complicate catalytic processes. Full article

Chiral mesoporous silica nanostructures (MSNs) have emerged as a cutting-edge material in nanotechnology. These nanostructures not only retain the tunable physicochemical properties of traditional MSNs—such as adjustable pore size, high surface area, and excellent biocompatibility—but also exhibit unique functionalities and biological behaviors due to their helical architectures at both molecular and macroscopic levels. This inherent chirality grants chiral MSNs exceptional potential in diverse applications, including chiral catalysis, enantiomeric separation, chiral recognition, and advanced drug delivery systems. Over the past five years, substantial progress has been made in understanding their synthesis mechanisms and practical applications. This review provides a comprehensive analysis of recent advancements in chiral silica nanostructures, with a focus on the synthesis strategies and applications of chiral MSNs. Emphasis is placed on their roles in chiral recognition, drug delivery, chiral separation, nanomedicine, and asymmetric catalysis. By highlighting these developments, this review serves as a roadmap for the rational design and translational applications of chiral silica nanostructures, offering valuable guidance for unlocking their full potential. Full article

Polyhedral oligomeric silsesquioxanes (POSS) harness their molecularly precise organic–inorganic hybrid cage architecture to deliver hardness, scratch resistance, and programmable functionality for next-generation transparent coatings. Tailoring of solubility, thermal stability, mechanical robustness, electronic characteristics, and interfacial properties is achieved through strategic peripheral modifications enabled by versatile synthetic methodologies—spanning metal catalysis, metal-free routes, and selective bond activation. Advanced integration techniques, including covalent grafting, chemical crosslinking, UV–thermal dual curing, and in situ polymerization, ensure uniform dispersion while optimizing coating–substrate adhesion and network integrity. The resultant coatings exhibit exceptional optical transparency, mechanical durability, tunable electrical performance, thermal endurance, and engineered surface hydrophobicity. These synergistic attributes underpin transformative applications across critical domains: atomic-oxygen-resistant spacecraft shielding, UV-managing agricultural films, flame-retardant architectural claddings, mechanically adaptive foldable displays, and efficiency-enhanced energy devices. Future progress will prioritize sustainable synthesis pathways, emergent asymmetric cage architectures, and multifunctional designs targeting extreme-environment resilience, thereby expanding the frontier of high-performance transparent protective technologies. Full article

The synthesis and application of new chiral amino acids (AAs) and peptides derived thereof is a research topic of major importance. The introduction of γ-AA as building blocks are useful for the development of original chiral small molecules and heterocycles, enabling the exploration of 3D chemical space in search of selectivity in biological properties. 4.5-Dihydro-2H-pyridazin-3-ones (DHPDOs) are 6-membered aza-heterocycles considered as masked γ-AA analogues. We herein report on the synthesis of various a-monosubstituted DHPDOs as platform-molecules using Meldrum’s acid chemistry and the a-functionalization approach upon the asymmetric Michael addition using the Phase-Transfer Catalysis (PTC). Full article

Hydroxamic acids are emerging as versatile chiral ligands for metal-catalyzed asymmetric oxidations due to their tunable electronic and steric environments. In this study, we systematically compared the catalytic behavior of C₂- and C₁-symmetric hydroxamic acid ligands in the vanadium-catalyzed asymmetric epoxidation of allylic alcohols. A series of chiral hydroxamic acids (HA1–HA7) was synthesized and evaluated under varied conditions to elucidate the influence of ligand symmetry on enantioinduction and reactivity. The results demonstrate that C₂-symmetric bishydroxamic acids generate a highly organized chiral environment, leading to high enantioselectivity but often limited conversion, consistent with the Sabatier principle. Conversely, certain C₁-symmetric ligands—particularly HA3—produced notable enantioselectivity (up to 71% e.e.) and full conversion under optimized conditions with VO(OiPr)₃ in CH₂Cl₂. A quadrant-based stereochemical model is proposed to rationalize the differential performance of these ligands. These findings highlight the critical role of ligand desymmetrization in modulating the chiral environment around vanadium centers, providing valuable design principles for next-generation hydroxamic acid-based catalysts in asymmetric synthesis. The optimized system (VO(OiPr)₃/HA3 in CH₂Cl₂) afforded >99% conversion and 71% e.e., providing a basis for extending hydroxamic acid scaffolds to diverse allylic alcohols. Full article

Post-translational modifications (PTMs) expand the structural diversity of proteins beyond the standard amino acids, influencing protein-protein interactions. Protein methylation, a prevalent PTM, involves the transfer of methyl groups from S-adenosylmethionine (SAM) to lysine and arginine residues. Arginine methylation is catalyzed by the Protein Arginine Methyltransferase (PRMT) family to yield mono- and dimethylarginine forms. PRMT1, the isozyme responsible for the majority of asymmetric dimethylation (ADMA) is implicated in various diseases, including cancer. Here, we report the synthesis and screening of a second-generation peptide library to identify novel PRMT1 substrates. The library, based on histone peptides, incorporated varying sequences of amino acids, facilitating substrate specificity studies. Screening identified 7 peptide sequences as exceptional PRMT1 substrates, which were confirmed by kinetic analysis. Consensus sequences revealed key recognition elements for PRMT1 catalysis, suggesting roles for small non-polar side chains and specific residues near the substrate arginine. Furthermore, we developed a peptide-based PRMT1 inhibitor by substituting the substrate arginine with a chloroacetamidine warhead. The inhibitor exhibited sub-micromolar inhibitory potency against PRMT1, surpassing previous peptide-based inhibitors. Our findings contribute to understanding PRMT1 substrate specificity and provide a scaffold for developing potent inhibitors targeting PRMT1 in diseases, including cancer. Full article

Chiral coordination compounds are of growing interest due to their structural diversity and wide applicability. Besides chirality, alcohol and especially oxime-functionalized limonene derivatives confer water solubility, stability, and the appropriate reactivity to enable their use in asymmetric catalysis—such as allylic substitution, alkynylation, transfer hydrogenation, and selective C–C bond formation. Biologically, they have shown promising anticancer, antibacterial, and antibiofilm activity. This review presents an integrated overview of the synthesis, properties, and applications of chiral transition metal complexes featuring ligands derived from inexpensive, naturally occurring R- and S-limonene substrates, and explore their roles in catalysis and biological activity. Full article

The growing demand for sustainable and efficient synthetic methodologies has brought nanocatalysis to the forefront of modern organic chemistry, particularly in the construction of heterocyclic compounds through multicomponent reactions (MCRs). Among various nanocatalysts, calcium oxide nanoparticles (CaO NPs) have gained significant attention because of their strong basicity, thermal stability, low toxicity, and cost-effectiveness. This review provides a comprehensive account of the recent strategies using CaO NPs as heterogeneous catalysts for the green synthesis of nitrogen- and oxygen-containing heterocycles through MCRs. Key reactions such as Biginelli, Hantzsch, and pyran annulations are discussed in detail, with emphasis on atom economy, reaction conditions, product yields, and catalyst reusability. In many instances, CaO NPs have enabled solvent-free or aqueous protocols with high efficiency and reduced reaction times, often under mild conditions. Mechanistic aspects are analyzed to highlight the catalytic role of surface basic sites in facilitating condensation and cyclization steps. The performance of CaO NPs is also compared with other oxide nanocatalysts, showcasing their benefits from green metrics evaluation like E-factor and turnover frequency. Despite significant progress, challenges remain in areas such as asymmetric catalysis, industrial scalability, and catalytic stability under continuous use. To address these gaps, future directions involving doped CaO nanomaterials, hybrid composites, and mechanochemical approaches are proposed. This review aims to provide a focused and critical perspective on CaO NP-catalyzed MCRs, offering insights that may guide further innovations in sustainable heterocyclic synthesis. Full article

Hydrogen-bond-like M···H–C interactions in square-planar d⁸ metal complexes have recently gained attention as structure-directing elements and design motifs in asymmetric catalysis. In this study, we explore these weak interactions not as static features, but as key modulators of molecular motion. We synthesized four cis-[N,N′-pentamethylenebis(iminomethylazolato)]M(II) (M = Pt, Pd), including iminomethyl-2-imidazole, iminomethyl-5-imidazole, and iminomethylpyrrolato Pt(II) complexes and an iminomethylpyrrolato Pd(II) analog. All complexes display reversible flipping of the alkylene bridge across the coordination plane, with the M···H–C interaction alternately engaging from above or below. This dynamic motion was characterized by variable-temperature ¹H NMR spectroscopy, revealing activation parameters for the flipping process. X-ray crystallography confirmed geometries consistent with hydrogen-bond-like interactions, while NBO analysis based on DFT calculations provided insight into their electronic nature. Interestingly, although Pt and Pd display comparable M···H–C distances, solvent effects dominate the flipping kinetics over metal identity. These findings highlight the role of hydrogen-bond-like M···H–C interactions not only in structural stabilization, but also in regulating conformational dynamics. Full article

In this work, a new asymmetric amidine–imine ligand, using 1,8-diaminonaphthalene as a rigid platform, was synthesized and characterized, and its ability to form complexes with aluminum(III) was investigated. Several aluminum complexes were synthesized and characterized in solution and in the solid state. The synthesis of a dihalogenated aluminum(III) complex (AlI₂L) using a reducing agent revealed an atypical pathway, which was investigated using Density Functional Theory (DFT). The dimethylated aluminum complex AlMe₂L and the dihalogenated aluminum complex AlI₂L were evaluated as catalysts for the transformation of CO₂ and epoxides into cyclic carbonates in the presence of Bu₄NI as a co-catalyst or in a single-component system, respectively. AlMe₂L/Bu₄NI appeared to be the most efficient system under 1 bar of CO₂ at 90 °C. Full article

This review updates the field of enantioselective copper-catalysed domino reactions promoted by chiral green copper catalysts, covering the literature since 2017. These complexes are derived from a diversity of chiral ligands, including mostly bisoxazolines and biphosphines along with monophosphines, N-heterocyclic carbenes, proline derivatives, phosphoric acids, phosphoramidates, and different types of N,N-ligands. The review shows that asymmetric copper catalysis, that suits the growing demand for greener processes, offers a real opportunity to replace toxic and expensive metals in the near future. Full article