Gd(III)-Catalyzed Regio-, Diastereo-, and Enantioselective [4 + 2] Photocycloaddition of Naphthalene Derivatives.

Catalytic asymmetric dearomatization (CADA) reactions have evolved into an efficient strategy for accessing chiral polycyclic and spirocyclic scaffolds from readily available planar aromatics. Despite the significant developments, the CADA reaction of naphthalenes remains underdeveloped. Herein, we report a Gd(III)-catalyzed asymmetric dearomatization reaction of naphthalene with a chiral PyBox ligand via visible-light-enabled [4 + 2] cycloaddition. This reaction features application of a chiral Gd/PyBox complex, which regulates the reactivity and selectivity simultaneously, in excited-state catalysis. A wide range of functional groups is compatible with this protocol, giving the highly enantioenriched bridged polycycles in excellent yields (up to 96%) and selectivity (up to >20:1 chemoselectivity, >20:1 dr, >99% ee). The synthetic utility is demonstrated by a 2 mmol scale reaction, removal of directing group, and diversifications of products. Preliminary mechanistic experiments are performed to elucidate the reaction mechanism.

Silver(I) Complexes with Mefenamic Acid and Nitrogen Heterocyclic Ligands: Synthesis, Characterization, and Biological Evaluation.

Four Ag(I) complexes with mefenamato and nitrogen heterocyclic ligands, [Ag(2-apy)(mef)]2 (1), [Ag(3-apy)(mef)] (2), [Ag2(tmpyz)(mef)2] (3), and {[Ag(4,4'-bipy)(mef)]2(CH3CN)1.5(H2O)2}n (4), (mef = mefenamato, 2-apy = 2-aminopyridine, 3-apy = 3-aminopyridine, tmpyz = 2,3,5,6-tetramethylpyrazine, 4,4'-bipy = 4,4'-bipyridine), were synthesized and characterized. The interactions of these complexes with BSA were investigated by fluorescence spectroscopy, which indicated that these complexes quench the fluorescence of BSA by a static mechanism. The fluorescence data also indicated that the complexes showed good affinity for BSA, and one binding site on BSA was suitable for the complexes. The in vitro cytotoxicity of the four complexes against human cancer cell lines (MCF-7, HepG-2, A549, and MDA-MB-468) and one normal cell line (HTR-8) was evaluated by the MTT assay. Complex 1 displayed high cytotoxic activity against A549 cells. Further studies revealed that complex 1 could enhance the intracellular levels of ROS (reactive oxygen species) in A549 cells, cause cell cycle arrest in the G0/G1 phase, and induce apoptosis in A549 cells in a dose-dependent manner.

Sulfur in Waste-Free Sustainable Synthesis: Advancing Carbon-Carbon Coupling Techniques.

This review explores the pivotal role of sulfur in advancing sustainable carbon-carbon (C-C) coupling reactions. The unique electronic properties of sulfur, as a soft Lewis base with significant mesomeric effect make it an excellent candidate for initiating radical transformations, directing C-H-activation, and facilitating cycloaddition and C-S bond dissociation reactions. These attributes are crucial for developing waste-free methodologies in green chemistry. Our mini-review is focused on existing sulfur-directed C-C coupling techniques, emphasizing their sustainability and comparing state-of-the-art methods with traditional approaches. The review highlights the importance of this research in addressing current challenges in organic synthesis and catalysis. The innovative use of sulfur in photocatalytic, electrochemical and metal-catalyzed processes not only exemplifies significant advancements in the field but also opens new avenues for environmentally friendly chemical processes. By focusing on atom economy and waste minimization, the analysis provides broad appeal and potential for future developments in sustainable organic chemistry.

Enantioselective Synthesis of Cyclobutane Derivatives via Cascade Asymmetric Allylic Etherification/[2 + 2] Photocycloaddition.

Chiral cyclobutane presents as a popular motif in natural products and biologically active molecules, and its derivatives have been extensively used as key synthons in organic synthesis. Herein, we report an efficient synthetic method toward enantioenriched cyclobutane derivatives. The reaction proceeds in a cascade fashion involving Ir-catalyzed asymmetric allylic etherification and visible-light induced [2 + 2] cycloaddition. Readily available branched allyl acetates and cinnamyl alcohols are directly used as the substrates under mild reaction conditions, providing a broad range of chiral cyclobutanes in good yields with excellent diastereo- and enantioselectivities (up to 12:1 dr, >99% ee). It is worth noting that all substrates and catalysts were simultaneously added without any separated step in this approach. The gram-scale reaction and diverse transformations of product further enhance the potential utility of this method.

Visible-light induced dearomatization reactions.

Dearomatization reactions provide rapid access to structurally complex three-dimensional molecules from simple aromatic compounds. Plenty of reports have demonstrated their utilities in the synthesis of natural products, medicinal chemistry, and materials science in the last decades. Recently, visible-light mediated photocatalysis has emerged as a powerful tool to promote many kinds of transformations. The dearomatization reactions induced by visible-light have also made significant progress during the past several years. This review provides an overview of visible-light induced dearomatization reactions classified based on the manner in which aromaticity is disrupted.

A label-free T4 polynucleotide kinase fluorescence sensor based on split dimeric G-quadruplex and ligation-induced dimeric G-quadruplex/thioflavin T conformation.

The phosphorylation process of DNA by T4 polynucleotide kinase (T4 PNK) plays a crucial role in DNA recombination, DNA replication, and DNA repair. Traditional monomeric G-quadruplex (G4) systems are always activated by single cation such as K+ or Na+. The conformation transformation caused by the coexistence of multiple cations may interfere with the signal readout and limit their applications in physiological system. In view of the stability of dimeric G4 in multiple cation solution, we reported a label-free T4 PNK fluorescence sensor based on split dimeric G4 and ligation-induced dimeric G4/thioflavin T (ThT) conformation. The dimeric G4 was divided into two independent pieces of one normal monomeric G4 and the other monomeric G4 fragment phosphorylated by T4 PNK in order to decrease the background signal. With the introduction of template DNA, DNA ligase, and invasive DNA, the dimeric G4 could be generated and liberated to combine with ThT to show obvious fluorescence signal. Using our strategy, the linear range from 0.005 to 0.5 U mL-1, and the detection limit of 0.0021 U mL-1 could be achieved without the consideration of interference caused by the coexistence of multiple cations. Additionally, research in real sample determination and inhibition effect investigations indicated its further potential application value in biochemical process research and clinic diagnostics.

Iridium-Catalyzed Asymmetric Allylic Benzylation with Photogenerated Hydroxy-o-Quinodimethanes.

An iridium-catalyzed asymmetric allylic benzylation of aryl vinyl carbinols under light irradiation is described. 2-Methylbenzophenone derivatives are employed and activated to hydroxy-o-quinodimethanes by an ultraviolet (UV) light. This approach enables asymmetric allylic benzylation with high enantioselectivity (up to 99 % ee) from readily available 2-methylbenzophenones without the utilization of strong bases, and pre-activation or pre-functionalization of the substrates. Moreover, deuterium experiments reveal the generation of nucleophilic benzyl species from 2-methylbenzophenone under UV irradiation.

Intermolecular Dearomatization of Naphthalene Derivatives by Photoredox-Catalyzed 1,2-Hydroalkylation.

An intermolecular hydroalkylative dearomatization of naphthalenes with commercially available α-amino acids is achieved via visible-light photoredox catalysis. With an organic photocatalyst, a series of multi-substituted 1,2-dihydronaphthalenes are obtained in good-to-excellent yields. Intriguingly, by tuning the substituents at the C2 position of naphthalenes, formal dearomative [3+2] cycloadditions occur exclusively via a hydroalkylative dearomatization-cyclization sequence. This overall redox-neutral method features mild reaction conditions, good tolerance of functionalities, and operational simplicity. Diverse downstream elaborations of the products are demonstrated. Preliminary mechanistic studies suggest the involvement of a radical-radical coupling pathway.

Asymmetric Dearomatization of Indole Derivatives with N-Hydroxycarbamates Enabled by Photoredox Catalysis.

Dearomatization of indoles provides efficient synthetic routes for substituted indolines. In most cases, indoles serve as nucleophiles. Reported here is an asymmetric dearomatization reaction of indole derivatives that function as electrophiles. The combination of a photocatalyst and chiral phosphoric acid open to air unlocks the umpolung reactivity of indoles, enabling their dearomatization with N-hydroxycarbamates as nucleophiles. A variety of fused indolines bearing intriguing oxy-amines were constructed in excellent yields with moderate to high enantioselectivities. Mechanistic studies show that the realization of two sequential single-electron transfer oxidations of the indole derivatives is key, generating the configurationally biased carbocation species while providing the source of stereochemical induction. These results not only provide an efficient synthesis of enantioenriched indoline derivatives, but also offer a novel strategy for further designing asymmetric dearomatization reactions.

Visible-Light-Promoted Intermolecular Oxidative Dearomatization of ß-Naphthols with N-Hydroxycarbamates.

An intermolecular oxidative dearomatization of ß-naphthols with N-hydroxycarbamates promoted by visible light was realized by means of photogenerated ß-naphthol radical cation intermediates. With a commercially available organic dye, the naphthalenones bearing a fully substituted stereogenic center were obtained with up to 92 % yield under aerobic conditions (26 examples). In addition, the rearrangement of C-O coupling products to C-N coupling compounds could be achieved merely in the presence of Cs2 CO3 . This transformation simultaneously provides an attractive and synthetically useful approach to access the aminative dearomatization compounds.

Direct Aromatic C-H Trifluoromethylation via an Electron-Donor-Acceptor Complex.

A novel electron-donor-acceptor (EDA) complex-mediated direct C-H trifluoromethylation of arenes with Umemoto's reagent has been developed. This transformation has been enabled by an unprecedented EDA complex formed by Umemoto's reagent and an amine, which was supported by experiments and theoretical calculations. The radical-based methodology presented here allows to access highly-functionalized trifluoromethyl arenes in up to 81 % chemical yield.

Immobilization of unraveled immunoglobulin G using well-oriented ZZ-His protein on functionalized microtiter plate for sensitive immunoassay.

Highly efficient protein immobilization is extremely crucial for solid-phase immunoassays. We present a strategy for oriented immobilization of functionally intact immunoglobulin G (IgG) on a polystyrene microtiter plate via iminodiacetic acid (IDA)-Ni(2+) and ZZ-His protein interaction. We immobilized a ZZ-EAP (Escherichia coli alkaline phosphatase)-His fusion protein, which exhibits Fc binding, His tag, and intrinsic AP activities, and analyzed it against the interaction between rabbit IgG anti-horseradish peroxidase (anti-HRP) and its binding partner HRP to investigate the specificity and efficacy of this method. We compared the IDA-Ni(2+)-(ZZ-His) method with ZZ-EAP random immobilization using sandwich enzyme-linked immunosorbent assay, and the results showed that the former method had an enhanced signal, 10-fold higher sensitivity, and a wider linear range. Thus, the proposed method allows a broad range of oriented immobilized functionally intact IgG antibodies on polystyrene plates using only one type of IDA-Ni(2+) chelate surface because the ZZ protein can bind to the Fc region of various IgGs.

Di-µ-benzoato-κ(3)O,O':O;κ(3)O:O,O'-bis-[aqua-(nitrato-κO)(1,10-phenanthroline-κ(2)N,N')lead(II)].

The title compound, [Pb(2)(C(7)H(5)O(2))(2)(NO(3))(2)(C(12)H(8)N(2))(2)(H(2)O)(2)], crystallizes as a dinuclear centrosymmetric dimer containing two Pb(II) atoms bridged by two benzoate ligands. Each Pb(II) atom is seven-coordinated by a water mol-ecule, a nitrate anion, a 1,10-phenanthroline (phen) ligand and two benzoate anions. The crystal packing is stabilized by O-H⋯O hydrogen bonds and by π-π stacking between neighboring phen ligands, with a centroid-centroid distance of 3.557 (3) Å.

catena-Poly[[bis-[aqua-(1,10-phenanthroline)lead(II)]-bis-(µ3-2-hy-droxy-5-sulfonato-benzoato)] acetic acid monosolvate].

In the title compound, [Pb2(C7H4O6S)2(C12H8N2)2(H2O)2]·CH3COOH, the seven-coordinate Pb(II) atom is chelated by two N atoms of one 1,10-phenanthroline ligand, four O atoms from three 5-sulfosalicylate dianions and one water O atom. Each dianion serves as a bridging ligand, connecting adjacent Pb(II) atoms into a centrosymmetric polymeric chain extending parallel to [001]. There are π-π inter-actions between the aromatic systems of neighbouring dianions, with plane-to-plane distances of 3.371 (2) Å, and between phenanthroline ligands, with a centroid-to-centroid distance of 3.484 (2) Å. O-H⋯O hydrogen bonding additionally stabilizes the crystal packing. The acetic acid mol-ecules are incorporated in the voids of this arrangement. They exhibit half-occupancy due to disorder around a centre of inversion.

Chiral Brønsted Acid-Catalyzed Intramolecular Asymmetric Allylic Alkylation of Indoles with Primary Alcohols.

Herein, chiral Brønsted acid-catalyzed intramolecular asymmetric allylic alkylation of indoles with allylic primary alcohols is described. The allyl alcohols were directly employed as the allylic precursors in this metal-free protocol, without preactivation or any additional activating reagents. This method provides the convenient synthesis of a broad range of functionalized tetrahydrocarbazoles in excellent yields (≤97%) with good enantioselectivity (≤93% ee). The optimal conditions are compatible for gram-scale reaction.

Synthesis, Characterization, and Evaluation of Nanoparticles Loading Adriamycin Based on 2-Hydroxypropyltrimethyl Ammonium Chloride Chitosan Grafting Folic Acid.

Chitosan nanoparticles have been considered as potential candidates for drug loading/release in drug delivery systems. In this paper, nanoparticles (HACAFNP) loading adriamycin based on 2-hydroxypropyltrimethyl ammonium chloride chitosan grafting folic acid (HACF) were synthesized. The surface morphology of the novel nanoparticles was spherical or oval, and the nanoparticles exhibited a relatively small hydrodynamic diameter (85.6 ± 2.04 nm) and positive zeta potential (+21.06 ± 0.96 mV). The drug release of nanoparticles was assayed and represented a burst effect followed by a long-term steady release. Afterward, the antioxidant efficiencies of nanoparticles were assayed. In particular, the target nanoparticles exhibited significant enhancement in radical scavenging activities. Cytotoxicities against cancer cells (MCF-7, BGC-823, and HEPG-2) were estimated in vitro, and results showed nanoparticles inhibited the growth of cancer cells. It's worth noting that the inhibition index of HACAFNP against BGC-823 cells was 71.19% with the sample concentration of 25 µg/mL, which was much higher than the inhibitory effect of ADM. It was demonstrated that the novel nanoparticles with dramatically enhanced biological activity, reduced cytotoxicity, and steady release could be used as the practical candidates for drug loading/release in a delivery system.

Photoredox-Catalyzed Intermolecular Hydroalkylative Dearomatization of Electron-Deficient Indole Derivatives.

Dearomatization of indole derivatives offers a straightforward approach to access diverse indolines. To date, the corresponding dearomative transformations involving electron-deficient indoles are limited. Herein, we report a one-electron strategy for dearomatization of electron-deficient indoles via a photoredox-catalyzed hydroalkylation employing commercially available glycine derivatives as the hydrofunctionalization reagents. Followed by DBU-mediated lactamization, structurally appealing lactam-fused indolines are obtained in good to excellent yields with exclusive selectivity.

A mechanochemically synthesized porous organic polymer derived CQD/chitosan-graphene composite film electrode for electrochemiluminescence determination of dopamine.

Herein, we explore a new carbon source for preparation of carbon quantum dots (CQDs) with controllable composition using a porous organic polymer (POP) derived porous carbon via a nitric acid oxidation method. The POP used for the preparation of CQDs was synthesized by mechanochemical Friedel-Crafts alkylation under solvent free conditions. Using the as-prepared CQDs, we develop a simple and effective electrochemiluminescence (ECL) detection method for dopamine (DA) using a CQD/chitosan-graphene composite modified glassy carbon electrode (GCE). Both the electrochemical and ECL behaviors were studied in detail with ammonium persulfate as a coreactant. The complementary structure and synergistic function of the composite give the ECL sensor special properties. Apart from the high stability, it also presents good repeatability and high sensitivity to DA with a wide linear range from 0.06 to 1.6 µM. And a satisfactory detection limit of 0.028 µM (S/N = 3) was achieved for the prepared sensor. Furthermore, the ECL also shows high selectivity toward DA with an excellent interference resistance ability at a high concentration ratio of 100 (C interference : C DA = 100). In addition, the ECL sensor was successfully applied for effective detection and quantitative analysis of the actual dopamine in human body fluids for disease diagnosis and pathological studies.

Radical Alkynyltrifluoromethylation of Alkenes Initiated by an Electron Donor-Acceptor Complex.

Radical alkynyltrifluoromethylation of alkenes with actylenic triflones has been achieved. This radical chain reaction is initiated by a catalytic amount of an electron-donor-acceptor complex composed of Togni's reagent and N-methylmorpholine. This transformation proceeds under exceptionally mild and operationally simple conditions. A variety of alkenes are compatible in this protocol including aliphatic alkenes, vinyl ethers, enecarbamates, styrenes, and even acrylates, providing diverse ß- trifluoromethyl alkynes in good to excellent yields.