Search Results (85)

Chirality is a cornerstone of biological systems and pharmaceutical activity, driving a critical need for rapid and sensitive enantioselective analytical methods. Covalent organic frameworks (COFs) have emerged as versatile porous materials, and their chiral counterparts, chiral COFs (CCOFs), uniquely combine high surface area, pre-designable pores, and a confined chiral microenvironment, making them exceptional platforms for enantioselective fluorescence sensing. This review systematically summarizes recent advances in the construction and application of CCOFs for enantioselective fluorescence sensing. We first outline the primary synthetic strategies for CCOFs, including direct synthesis, post-synthetic modification, and chiral induction. Subsequently, based on the direction of fluorescence signal change upon analyte binding, we classify the sensing mechanisms into three categories: “turn-off” (quenching via static complexation or photoinduced electron transfer), “turn-on” (enhancement through rigidification or suppression of electron transfer), and ratiometric (self-calibrating dual-emission response). Representative examples for the detection of amino acids, amino alcohols, terpenes, and saccharides are highlighted for each mode. Special emphasis is placed on structure–property relationships, such as the synergistic roles of hydrogen bonding, π–π stacking, and framework confinement in amplifying enantioselectivity. Finally, we discuss current challenges and future perspectives, including the rational design of ratiometric sensors, integration into practical devices, and the convergence with machine learning to advance the field of smart chiral sensing. Full article

For those who did not follow the invention and development of enantioselective catalysis, this review introduces pertinent historical aspects of the field and presents the scientific concepts of asymmetric bio- and organocatalysis. They are powerful technologies applied in organic laboratories and industry. They realize chiral amplification by converting inexpensive achiral substrates and reagents into enantiomerically enriched products using readily recoverable solvents, if any are used. Racemic substrates can also be deracemized catalytically. More sustainable fabrications are now available that require neither toxic metallic species nor costly reaction conditions in terms of energy, atmosphere control, product purification, and safety. Nature has been the source of the first asymmetric catalysts (microorganisms, enzymes, alkaloids, amino acids, peptides, terpenoids, sugars, and their derivatives). They act as temporary chiral auxiliaries and lower the activation free energy of the reaction by altering the reaction mechanism. Reductions, oxidations, carbon-carbon and carbon-heteroatom bond-forming reactions are part of the process panoply. Asymmetric catalyzed multicomponent and domino reactions are becoming common. Typical modes of activation are proton transfers, hydrogen bonded complex formation, charged or uncharged acid/base pairing (e.g., σ-hole catalysts), formation of equilibria between achiral aldehydes and ketones with their chiral iminium salt or/and enamine intermediates, umpolung of aldehydes and ketones by reaction with N-heterocyclic carbenes (NHCs), phase transfer catalysis (PTC), etc. Often, the best enantioselectivities are observed with polyfunctional catalysts derived from natural compounds, but not always. They may combine to form chiral structures containing nitrogen, phosphorus, sulfur, selenium, and iodine functional moieties. Today, man-made enantiomerically enriched catalysts, if not enantiomerically pure, are available in both enantiomeric forms. Being robust, they are recovered and reused readily. Full article

Apart from in hydrosilylation, platinum has traditionally played a limited role in homogeneous catalysis due to its high thermodynamic stability and lower intrinsic reactivity compared to other group 10 metals. However, the emergence of N-heterocyclic carbene (NHC) ligands has substantially broadened the catalytic profile of transition metals by enabling access to new mechanistic pathways and enhancing robustness under demanding conditions. This review summarizes advances in Pt–NHC catalysis reported between 2010 and 2025. These transformations encompass hydrosilylation of amides and CO₂, hydroboration and diboration, hydroamination, alkyne hydration, hydrogenation, selective alkyne dimerization, Suzuki–Miyaura coupling, arene C–H borylation, and cycloisomerization reactions, in which NHC ligands enhance bond activation, control regio- and stereoselectivity, and stabilize reactive Pt intermediates, including chiral architectures, enabling high enantioselectivity. Full article

G-quadruplex (G4) DNA structures have recently emerged as promising chiral scaffolds for enantioselective catalysis. This study investigates how thymidine loop modifications influence the catalytic performance of the telomeric G4 sequence HT21 in the asymmetric sulfoxidation of thioanisole. To this end, several singly or doubly modified HT21 derivatives were synthesized by using β-L-2′-deoxythymidine, 5-hydroxymethyl-2′-deoxyuridine, and 5-bromo-2′-deoxyuridine instead of a T residue, or β-L-2′-deoxyadonesine instead of an A residue, in specific positions within the TTA loops. The catalytic activity of these analogues was evaluated in the Cu(II)-mediated oxidation of thioanisole using hydrogen peroxide as oxidant. All modified sequences maintained complete substrate conversion, but their enantioselectivities varied markedly. Whereas the highest enantiomeric excess (84% ee) had previously been achieved with the HT21 analogue bearing a β-L-2′-deoxyadenosine in the first loop, the thymidine-based modifications, either alone or in combination, resulted in lower ee values, suggesting that loop alterations critically affect the chiral microenvironment, not all loop positions are functionally equivalent, and single substitutions within the same loop can result in different enantioselectivities. These findings highlight new insights on how individual loop residues contribute to asymmetric induction and offer further details for tuning G4-based catalytic scaffolds. Full article

The development of nanoscale chiral materials with enhanced optical properties holds significant promise for advancing technologies in light-emitting devices and enantioselective sensing. Here, we report the self-assembly of chiral metal–organic cages from an axially chiral, AIE-active binaphthyl dicarboxylate ligand. This supramolecular architecture functions as a multifunctional platform, demonstrating a high affinity for anionic guests through synergistic electrostatic and hydrogen-bonding interactions. The rigid cage framework not only enhances the ligand’s intrinsic aggregation-induced emission (AIE) but also serves as a highly effective chiral amplifier. Notably, MOCs significantly boost the circularly polarized luminescence (CPL), achieving a luminescence dissymmetry factor (|g_lum|) of 1.2 × 10⁻³. This value represents an approximately five-fold enhancement over that of the unassembled ligand. The photophysical properties of this chiral supramolecular system provide a strategic blueprint for designing next-generation optical nanomaterials. Full article

Catalytic transfer hydrogenation (CTH) provides a practical and sustainable approach for reducing unsaturated compounds, serving as an alternative to high-pressure H₂ in laboratory and fine chemical contexts. This broad reaction class includes asymmetric transfer hydrogenation (ATH), a key strategy in enantioselective synthesis due to its operational simplicity, high stereocontrol, and compatibility with sensitive functional groups. A central variable governing CTH efficiency is the role of bases, which may function as essential activators, co-hydrogen donors, or be entirely absent depending on the catalytic system. This review provides a comparison of base-assisted, base-free, and base-as-co-hydrogen-donor CTH methodologies across diverse metal catalysts and substrates. We highlight how bases such as triethylamine, K₂CO₃, and NaOH facilitate catalyst activation, modulate hydride formation, and tune reactivity and selectivity. The dual function of bases in formic-acid-driven systems is examined alongside synergistic effects observed with mixed-base additives. In contrast, base-free CTH platforms demonstrate how tailored ligand frameworks, metal-ligand cooperativity, and engineered surface basicity can eliminate the need for external additives while maintaining high activity. Through mechanistic analysis and cross-system comparison, this review identifies the key structural, electronic, and environmental factors that differentiate base-assisted from base-free pathways. Emerging trends—including greener hydrogen donors, advanced catalyst architectures, and additive-minimized protocols—are discussed to guide future development of sustainable CTH processes. Full article

Molecularly imprinted polymers (MIPs) are polymeric receptors for a targeted template molecule that are traditionally formed using a combination of functional monomers and crosslinkers. While investigating novel crosslinkers for MIPs, one of these (2-(methacryloylamino)ethyl-2-methylacrylate (referred to as N,O-bismethacryloyl ethanolamine or “NOBE”)) performed better when used alone versus in combination with other monomers. This introduced the concept of one monomer molecularly imprinted polymers, given the acronym OMNiMIPs, and prompted studies provided in this report that clarify OMNiMIPs have fundamental differences compared to traditionally formulated MIPs. Enantioselectivity studies using BOC-L-tyrosine as a standard template showed that NOBE OMNiMIPs afforded higher-performing MIPs compared with traditional MIPs, have significantly higher binding capacities, and have an internal hydrogen-bonded crosslinking structure that contributes to the morphological stability of the binding site structure. Based on the adventitious discovery of NOBE OMNiMIPs, new analogs based on the NOBE structure were developed and evaluated for further enhancement of molecular recognition performance and novel capabilities of OMNiMIPs. While the majority of the new OMNiMIPs exhibited enantiomeric selectivity toward BOC-L-tyr, improvements were not observed compared with NOBE. Full article

Enantioselective transition metal catalysis is undoubtedly a cornerstone at the frontier of chemistry, attracting intense interest from both academia and the pharmaceutical industry. Central to this field is the strategic utilization of noncovalent interactions (NCIs), including hydrogen bonding, ion pairing, and π-system engagements, which not only drive asymmetric synthesis but also enable precise stereochemical control in transition metal-catalyzed transformations. Recent breakthroughs have unveiled a new generation of rationally designed ligands that exploit ligand–substrate noncovalent interactions, emerging as indispensable tools for stereocontrolled synthesis and setting new paradigms in ligand engineering. These advancements establish a transformative framework for ligand engineering, bridging fundamental mechanistic insights with practical synthetic utility. In this review, the judicious design concepts and syntheses of novel ligands from the past five years were highlighted and their synthetic applications in asymmetric catalysis were detailed. Full article

Using the DFT method, an analogue of R,R-t-Bu-BenzP* was tried as a potential ligand for Ni-catalyzed asymmetric hydrogenation. This ligand contains benzyl groups instead of the t-Bu groups in R,R-t-Bu-BenzP*. Computational results imply that the R,R-Benz-BenzP* ligand (1) is expected to provide excellent enantioselectivity in the Ni-catalyzed asymmetric hydrogenation of 1-phenylethanone oxime. The computed effectiveness of the R,R-Benz-BenzP* ligand is stipulated by its conformational flexibility, which helps stabilize the crucial transition states via a non-bonding interaction between the substrate and the catalyst. R,R-Benz-BenzP* ligands with CN- and OMe-substituted benzyl rings were also computed to possess the same effectiveness. Full article

1,2-Diphenylethylenediamine (DPEDA) is a privileged chiral scaffold being used in the construction of a broad variety of organocatalysts and ligands for enantioselective organic reactions. This molecule gave a significant contribution in the synthesis of structurally different bi/multifunctional organocatalysts. DPEDA played an essential role in the development of organocatalysts capable of yielding important information on the different reaction mechanisms, like enamine, iminium, hydrogen-bonding and anion-binding catalysis. The aim of the present review is to highlight and summarize the achievements reached in the last 20 years (2004–2024) in the chemistry of DPEDA-based organocatalysts for asymmetric synthesis. Full article

Enantiopure tetrahydroisoquinolines (THIQs), recognized as privileged skeletal structures in natural alkaloids, have attracted considerable attention from chemists due to their biological and pharmacological activities. Synthetic strategies for optically active THIQs have been rapidly and extensively developed in the past decades. In view of simplicity and atom economy, asymmetric reduction of N-heteroaromatics, imines, enamines, and iminium salts containing an isoquinoline (IQ) moiety should be the preferred approaches to obtain chiral THIQs. This review focuses on recent advances in the catalytic asymmetric synthesis of enantiopure THIQs via asymmetric reduction, including asymmetric hydrogenation, transfer hydrogenation, reductive amination, and deracemization. Highly enantioselective synthesis of THIQs was achieved via transition-metal-catalyzed asymmetric reduction and organocatalytic asymmetric reduction utilizing either catalyst activation or substrate activation strategy. Despite much progress in the enantioselective synthesis of THIQs, there still remain considerable opportunities and challenges for progress and developments in this field of research, particularly in the development of asymmetric catalytic systems for the direct reduction of IQs. Full article

Ring size-dependent diastereoselective coordination of unsymmetrical diamines containing one azacyclic nitrogen and one exocyclic nitrogen to [(η⁵-C₅Me₅)MCl]⁺ cores where M = Rh, Ir and [Ru(η⁶-cymene)Cl]⁺ is reported herein. Total stereoselectivity was observed with the six- and seven-membered azacycles, whereas the five-derivative proved poorly selective. All complexes were active for transfer hydrogenation but showed no enantioselectivity with prochiral ketones. Full article

Chiral pincer complexes, characterized by their rigid tridentate coordination framework, have emerged as powerful catalysts in asymmetric synthesis. This review provides a comprehensive overview of recent advancements in the development of chiral pincer-type ligands and their corresponding transition metal complexes. We highlight the latest progress in their application across a range of catalytic asymmetric reactions, including the (transfer) hydrogenation of polar and non-polar bonds, hydrophosphination, alkynylation, Friedel-Crafts reactions, enantioselective reductive cyclization of alkynyl-tethered cyclohexadienones, enantioselective hydrosilylation, as well as Aza–Morita–Baylis–Hillman reactions. The structural rigidity and tunability of chiral pincer complexes enable precise control over stereoselectivity, resulting in high enantioselectivity and efficiency in complex molecular transformations. As the field advances, innovations in ligand design and the exploration of new metal centers are expected to expand the scope and utility of these catalysts, bearing significant implications for the synthesis of enantioenriched compounds in pharmaceuticals, materials science, and beyond. Full article

The development of new chiral ligands with simple and modular structure represents a challenging direction in the design of efficient homogeneous transition metal catalysts. Herein, we report on the asymmetric hydrogenation of prochiral ketones catalyzed by the iridium complexes of simple alkane-diyl-based P,N,O-type chiral ligands with a highly modular structure. The role of (i) the P-N and N-O backbone in the potentially tridentate ligands, (ii) the number, position and relative configuration of their stereogenic elements and (iii) the effect of their NH and OH subunits on the activity and enantioselectivity of the catalytic reactions are studied. The systematic variation in the ligand structure and the comparative catalytic experiments shed light on different mechanistic aspects of the iridium-catalyzed reaction. The catalysts containing the simple alkane-diyl-based ligands with central chirality provided high enantioselectivities (up to 98% ee) under optimized reaction conditions and proved to be active and selective even at very high substrate concentrations (100 mmol substrate/mL solvent). Full article

The (R,R)-Teth-TsDPEN-Ru(II) complex promoted the one-pot double C=O reduction of α-alkyl-β-ketoaldehydes through asymmetric transfer hydrogenation/dynamic kinetic resolution (ATH-DKR) under mild conditions. In this process, ten anti-2-benzyl-1-phenylpropane-1,3-diols (85:15 to 92:8 dr) were obtained in good yields (41–87%) and excellent enantioselectivities (>99% ee for all compounds). Notably, the preferential reduction of the aldehyde moiety led to the in situ formation of 2-benzyl-3-hydroxy-1-phenylpropan-1-one intermediates. These intermediates played a crucial role in enhancing both reactivity and stereoselectivity through hydrogen bonding. Full article