Search

The document is the contents list for an issue of the journal Chemical Communications. It includes articles on various topics such as AI-assisted chemistry research, modification strategies of lead halide perovskite nanocrystals, gold catalysis in quinoline synthesis, and rapid production of H2O2 in a photocatalyst suspension. The journal is published by The Royal Society of Chemistry and aims to connect the world with the chemical sciences. [Extracted from the article]

Quinolines are biologically and pharmaceutically important N-heterocyclic aromatic compounds, which have broad applications in medicinal chemistry. Thus, their efficient synthesis has attracted extensive attention, and a broad range of synthetic strategies have been established. Of note, gold-catalyzed methodologies for the synthesis of quinolines have greatly advanced this field. Various gold-catalyzed intermolecular annulation reactions, such as annulations of aniline derivatives with carbonyl compounds or alkynes, annulations of anthranils with alkynes, and annulations based on A3-coupling reactions, as well as intramolecular cyclization reactions of azide-tethered alkynes, 1,2-diphenylethynes, and 2-ethynyl N-aryl indoles, have been developed. This review provides an overview of this exciting research area. Typical achievements in reaction methodologies and plausible reaction mechanisms are summarized. [ABSTRACT FROM AUTHOR]

A new cobalt-based metal–organic framework with the chemical formula of [Co2(DClTPA)2(DABCO)]·(DMF)4 (MUT-16) containing 1,4-diazabicyclo[2.2.2]octane (DABCO) and 2,5-dichloroterephthalic acid (DClTPA) has been designed and prepared through a solvothermal method. MUT-16 (MUT = Materials from University of Tehran) crystallized in a tetragonal system with I41/acd space group, based on single-crystal X-ray analysis. The Ag@MUT-16 nanocomposite was prepared using Ag nanoparticles (NPs) loaded into/onto porous MUT-16via photoreduction route (PR). The MUT-16 and Ag@MUT-16 were characterized using various techniques, such as PXRD, FT-IR, FE-SEM, TEM, EDX, N2 adsorption–desorption isotherms, TGA, DRS, PL, EIS, and Mott–Schottky measurements. The Ag@MUT-16 nanocomposite showed photocatalytic activity of 87.75% in the degradation of Quinoline Yellow (QY) after 30 min under visible light irradiation. The distinctive characteristics of the Ag@MUT-16 nanocomposite, such as the Fenton-like effect of Co2+ ions, surface plasmon resonance (SPR) of Ag NPs, Schottky junction at interfaces between Ag NPs and MUT-16, and reduction of electron–hole recombination through electron trapping by Ag NPs as co-catalyst, all play significant roles in the photocatalytic degradation of Quinoline Yellow (QY). [ABSTRACT FROM AUTHOR]

The document is the contents list for an issue of the journal Chemical Communications. It includes a range of articles on various topics, such as nanopesticides, molecular dynamics simulations, radical qubits, enzymatic activity, and electrochemical reactions. The journal is published by The Royal Society of Chemistry and aims to connect the world with the chemical sciences. The document provides a snapshot of the articles included in the issue, allowing library patrons to quickly identify relevant research topics. [Extracted from the article]

Iron-binding strategies in anticancer drug design target the key role of iron in cancer growth. The incorporation of a quinoline moiety in the design of tetrazolium-based prochelators facilitates their intracellular reduction/activation to iron-binding formazans. The new prochelators are antiproliferative at submicromolar levels, induce apoptosis and cell cycle arrest, and impact iron signaling in cancer cells. [ABSTRACT FROM AUTHOR]

Chemical Communications is a journal published by The Royal Society of Chemistry, which aims to connect the world with the chemical sciences. The contents list of the journal includes various research articles on topics such as the characterization of a polyoxometalate containing a transplutonium element, the evaluation of titanium oxide as an electrocatalyst, and the synthesis of various compounds. The journal covers a wide range of topics in the field of chemistry and is open to everyone interested in impactful research on energy and environmental catalysis. [Extracted from the article]

The photophysical and chiroptical properties of a chiral biquinoline amphiphile were found to be closely related to its aggregate states. Photochromism through photo-induced radical and circularly polarized luminescence were realized in its gel state and thin film state, respectively. [ABSTRACT FROM AUTHOR]

We have successfully synthesized quinoline derivatives that exhibit easy scalability and responsiveness to multiple stimuli. These derivatives are capable of forming self-assembled nanoscopic aggregates in an aqueous medium. Consequently, when placed in an aqueous environment, we observe dual fluorescence originating from both twisted intramolecular charge transfer and aggregation-induced emission. The introduction of nerve gas agents, such as diethyl chlorophosphate (DClP) or diethylcyanophosphate (DCNP), to the probe molecules facilitates the charge-transfer process, resulting in a red-shift in absorption maxima. Notably, when operating in fluorescence mode, both of these analytes produce distinct output signals, making them easily distinguishable. DCNP generates a blue fluorescence, while the addition of DClP yields cyan fluorescence. Our mechanistic investigation reveals that the initial step involves phosphorylation of the quinoline nitrogen end. However, in the case of DCNP, the released cyanide ion subsequently attacks the carbonyl carbon centre, forming a cyanohydrin derivative. The response to these target analytes appears to be influenced by the nucleophilicity of the quinoline nitrogen end and the electrophilic nature of the carbonyl unit. [ABSTRACT FROM AUTHOR]

The first example of manganese-catalyzed asymmetric transfer hydrogenation of N-heteroaromatics in water is reported. This ATH reaction proceeds smoothly without the need for inert atmosphere protection in the presence of a water-stable manganese catalyst, which bears an easily available aminobenzimidazole ligand. Ammonia borane, regarded as a green, cheap and high atom economical hydrogen source, was applied. Various quinolines are transformed into the desired products in high yields and up to 99% enantiomeric excess (ee). The utility of the current protocol was demonstrated by applying it in the gram-scale total synthesis of the Hancock alkaloid (−)-cuspareine with 96% overall yield. [ABSTRACT FROM AUTHOR]

Inter-molecular π–π stacking interactions of aromatic systems play crucial roles in functional nanomaterials and therapeutics. Herein, we developed a series of novel 8-hydroxyquinoline-polycyclic aromatic hydrocarbon (PAH) conjugates (PH1–PH3) by coupling 8-hydroxyquinoline with a series of PAHs such as naphthalene, anthracene, and pyrene. A second series of quinoline-PAH derivatives (PD1–PD3) has also been developed by sulfonating the quinoline –OH of the first series. Crystallographic analyses of these compounds revealed exciting structural and supramolecular features. Supramolecular analyses of PH series compounds revealed that the crystal packing interactions in these compounds are dominated by intermolecular C–H⋯O and C–H⋯π interactions, in which the C–H⋯O interactions lead to the formation of zig-zag 1D chains in the crystal lattice, which are interconnected to a 3D network by various intermolecular C–H⋯π interactions. Compared to the PH series, the supramolecular interactions in the PD series are dominated by π–π and C–H⋯π interactions. In these compounds, two adjacent V-shaped molecules are arranged in a dimeric fashion such that one arm of the V-shaped molecule is packed within the cleft formed by the arms of the other. In the crystal lattice of PD series compounds, such dimers are interconnected through π–π interactions into 1D chains/2D sheets, which are further interconnected into 2D/3D networks through additional C–H⋯π/π–π stacking interactions. The preliminary cytotoxicity properties of PH and PD series compounds were evaluated using human hepatocellular carcinoma cells (HepG2 cells). It was observed that the presence/absence of –OH group on the quinoline ring and the size of the PAH ring play significant roles in determining the cytotoxicity of these compounds. The PH series compounds with an –OH substituent on the quinoline ring exhibited comparatively better cytotoxicity (IC50 values in the range 8.03–11.72 μM) than the PD series compounds (IC50 values in the range 9.48–38.16 μM) with sulfonated quinoline moiety. The compound bearing pyrene PAH and –OH substituent on the quinoline ring exhibited the best cytotoxicity (IC50 = 8.03 μM) among all the compounds tested. The present study, therefore, shows that the quinoline-PAH conjugates can exhibit interesting structural and supramolecular properties along with appreciable cytotoxic effects. Further, these properties could be fine-tuned by changing the size of the PAH ring and the substituent on the quinoline ring. [ABSTRACT FROM AUTHOR]

Ruthenium(II) complexes [RuL(CO)Cl(PPh3)2], 1a–4a, have been synthesized using ligands PhN＝NC(Ar)NOH, HL 1–4, respectively, by varying the pendant aryl (Ar) groups. The single crystal X-ray diffraction studies of complexes reveal that there are certain changes in Ru–Nazo and Ru–Noxime bond lengths that may be explained primarily on the basis of electronic effects of pendant aryl groups. In 4a, all Ru–N bond lengths are longer and this is attributed to oximato–O⋯O (hydroxyphenyl) interactions. Furthermore, there are weak intramolecular F⋯π interactions in 3a. The complexes display multiple reductive responses ascribable to electron acceptance within the azo-oxime framework of the coordinated ligand and the corresponding one-electron reduced metastable anion radical complexes of type [Ru(L˙−)(CO)Cl(PPh3)2]−[1]˙− have been generated. This property of the complexes has been exploited in electron transfer catalysis via trapping of electrons in the azo-oxime skeleton in two types of reactions: (1) α-alkylation of ketones with primary alcohols and (ii) synthesis of 2-substituted quinoline derivatives from 2-aminobenzyl alcohols and substituted acetophenones/alkyl methyl ketones. The scope of catalysis has been studied and the probable catalytic pathway has been established from experimental results. The catalytic pathway is ligand-centric and redox-driven for the dehydrogenation process and the initial step involves formation of a coordinated anion radical. This leads to conversion of the starting 1° alcohol to the corresponding carbonyl via the HAT pathway, with the ruthenium(II) centre practically behaving as a template and remaining redox inactive. The catalytic reactions have been proven to be affected by the nature of pendant aryl (Ar) groups within the coordinated ligand. [ABSTRACT FROM AUTHOR]

A series of tetrahydroquinoline derivatives were selectively synthesized at room temperature via electrochemical hydrocyanomethylation of quinoline skeletons using acetonitrile as both a hydrogen source and a cyanomethyl precursor. When a bulky substituent was present at the C2 position, hydrogenation of quinoline derivatives dominated. Furthermore, a deuterium labeling experiment revealed that protons were derived from acetonitrile. This method features mild conditions, high efficiency, wide substrate scope, and good functional group tolerance. [ABSTRACT FROM AUTHOR]

A Lewis acid-mediated synthesis of 3-substituted quinolines from readily available 2-aminobenzyl alcohols and N,N′-dimethylenamine(one)s is reported. The Friedlander-type reaction described herein is modular and allows the installation of a variety of electron-withdrawing groups (COPh, CN, CO2Me, NO2, SO2Ph) at the 3-position of the quinoline nucleus to afford the final products in moderate to good yields. The reaction proceeds via transamination followed by the formation of a C–C bond by the involvement of a boron complex and aerobic oxidation to offer the product. [ABSTRACT FROM AUTHOR]

A rapid, efficient and eco-friendly synthesis of 2-aroxyquinolines and 2-aminoquinolines was developed respectively through activating agent-promoted deoxygenative aryloxylation/amination. The main challenges in constructing C2–O or C2–N bonds from N-oxides lie in overcoming two side reactions: the reaction between the activating agent and the nucleophile, and the associated reaction at the C4-position. Compared to previous reports, this method benefits from an eco-friendly solvent, short reaction time, simple operation, and wide substrate scope, providing a variety of heteroaryl ethers and amines. We have demonstrated a gram-scale synthesis and calculated the green chemistry metrics to highlight the advantage of the developed synthetic method. [ABSTRACT FROM AUTHOR]

Metal complexes play a crucial role in photo-activated chemotherapy (PACT), which has recently been used to treat specific disorders. Triple-negative breast cancer has an enormously high rate of relapse due to the existence and survival of cancer stem cells (CSCs) characterized by increased amounts of glutathione (GSH). Hence, designing a phototoxic molecule is an enticing area of research to combat triple-negative breast cancer (TNBC) via GSH depletion and DNA photocleavage. Herein, we focus on the application of PTA and non-PTA Ir(III) complexes for phototoxicity in the absence and presence of GSH against MDA-MB-231 TNBC cells. Between these two complexes, [Cp*IrIII(DD)PTA]·2Cl (DDIRP) exhibited better phototoxicity (IC50 ~2.80 ± 0.52 µM) compared to the non-PTA complex [Cp*IrIII(DD)Cl]·Cl (DDIR) against TNBC cells because of the high GSH resistance power of the complex DDIRP. The significant potency of the complex DDIRP under photo irradiation in both normoxia and hypoxia conditions can be attributed to selective transportation, high cellular permeability and uptake towards the nucleus, GSH depletion by GSH-GSSG conversion, the ability of strong DNA binding including intercalation, and oxidative stress. The strong affinity to serum albumin, which serves as a carrier protein, aids in the transport of the complex to its target site while preventing glutathione (GSH) deactivation. Consequently, the complex DDIRP was developed as a suitable phototoxic complex in selective cancer therapy, ruling over the usual chemotherapeutic drug cisplatin and the PDT drug Photofrin. The ability of ROS generation under hypoxic conditions delivers this complex as a hypoxia-efficient selective metallodrug for the treatment of TNBC. [ABSTRACT FROM AUTHOR]

Quinoline carboxylic acid-linked and Pd nanoparticle (NP)-loaded COF nanospheres were constructed via a three-component one-pot Doebner reaction and post-synthetic metalation. The obtained Pd@DhaTAPB-COOH solid stabilizer can greatly promote the pH-switched recyclable Pickering interfacial dechlorination reaction, which sheds light on the bright future of smart Pickering emulsion catalysis. [ABSTRACT FROM AUTHOR]

This manuscript describes the synthesis of a triazolyl-pyridine-based phosphine, N-((diphenylphosphaneyl)methyl)-N-methyl-6-(1-phenyl-1H-1,2,3-triazol-4-yl)pyridin-2-amine, [2,6-{(PPh2)CH2N(Me)(C5H3N)(C2HN3C6H5)}] (1) (here onwards referred to as PNN) and its cationic and neutral MnI complexes and catalytic applications. The reaction of 1 with Mn(CO)5Br afforded a cationic complex [Mn(CO)3(PNN)]Br (2), which is highly stable in solid state, but in solution it gradually loses one of the CO groups to form a neutral complex [Mn(CO)2(PNN)Br] (3). Complex 2 on treatment with AgBF4 also yielded a cationic complex [Mn(CO)3(PNN)]BF4 (4). These complexes efficiently promoted the synthesis of quinoline derivatives via acceptor-less dehydrogenative coupling of 2-aminobenzyl alcohol and ketones, with complex 3 showing the highest activity with a very low catalyst loading (0.03 mol%) at 110 °C. Complex 3 (0.5 mol%) also showed excellent catalytic activity in the transfer hydrogenation of ketones and aldehydes to form respective secondary and primary alcohols. [ABSTRACT FROM AUTHOR]

Improving the dispersion of metal nanoparticles and suppressing metal aggregation have long been the keys to constructing efficient metal-loaded catalysts. Herein, catalysts of cobalt (Co) supported on nitrogen (N)-doped carbon were prepared by a simple hydrothermal method using folic acid (FA) as the carbon source. Surprisingly, hydrazine hydrate not only facilitated the loading of metal Co, but also regulated the morphology of the catalyst, promoted the uniform distribution of metal Co, and effectively improved the catalytic hydrogenation activity of the catalyst. It was found that the catalyst mediated with 10 mL hydrazine hydrate and pyrolyzed at 900 °C exhibited the best catalytic performance (99.6% conversion of quinoline and 98.0% selectivity for 1,2,3,4-tetrahydroquinoline). In addition, it exhibited satisfying adaptability for diverse substrates. This study can provide great theoretical significance and practical guidance for the preparation of Co–N–C catalysts. [ABSTRACT FROM AUTHOR]

The palladium-catalyzed oxidative C3-alkenylation of anthranils (2,1-benzisoxazoles) with various styrenes has been successfully achieved. The C3-alkenylated anthranils were subsequently utilized in a [4+2]-cycloaddition with in situ generated α,β-unsaturated ketones leading to the synthesis of a diverse range of olefin-containing quinolines. Notably, this reaction exclusively yielded mono-alkenylated products with E-selectivity. The optimized catalytic conditions were compatible with a wide variety of substituted olefins and anthranils, forming various C3-alkenylated anthranils with good yields. To showcase the application of the present methodology, the C3-alkenylated anthranils have been employed as synthons to access a wide range of substituted quinolines. [ABSTRACT FROM AUTHOR]

One-pot transformation of N,N-dimethylaniline to fused quinoline derivatives was achieved through sequential oxidative cyclization followed by a concomitant C(sp3)–N cleavage/aromatization reaction. The transformation was successfully carried out under an air atmosphere at room temperature itself. Mechanistic investigations revealed that the reaction follows the radical pathway. In silico studies showed that the synthesized molecules exhibit good caspase-3 inhibitory activity. [ABSTRACT FROM AUTHOR]

CH-arylated quinolines have found widespread applications in drug discovery as well as in the field of fine chemicals and material science. Herein, we report a general, transition-metal-free, environmentally friendly photocatalytic strategy for the direct C–H arylation of quinolines and quinoline N-oxides/pyridines selectively at the C-8 and C-2 positions, respectively, using chlorophyll as the organic photocatalyst. This method offers a simple, practical route for direct access to C8-aryl quinolines, C2-aryl pyridines, and quinoline N-oxides. The key advantages of the present protocol include operational simplicity, the use of clean energy sources, low reagent costs, and no requirement of pre-functionalized substrates. [ABSTRACT FROM AUTHOR]

Catalyst-free nucleophilic substitution of hydrogen in quinolines under the action of available acylethynylpyrroles occurs at 80–110 °C in MeCN or toluene to stereoselectively afford 2-(E-2-acylethenylpyrrolyl)quinolines with a yield up to 78%. This unexpected cross-coupling proceeds apparently via the redox ring-opening of the intermediate quinoline/acylethynylpyrrole cycloadduct. Thus, we produced the first example of intramolecular SNH substitution of hydrogen in quinoline using the pyrrole nucleophile with 1,2-transfer of the acylethenyl substituent in the intermediate [2 + 3]-cycloadduct. This intermediate was isolated in the case of 1-methylisoquinoline wherein the [2 + 3]-cycloadduct was found to be stable. In general, the reaction mechanism was also supported using a high-level correlation electron pair approximation approach LPNO-CEPA/1/CBS utilizing M06-2X/Def2-TZVPP geometry. [ABSTRACT FROM AUTHOR]

A robust diphosphine-ruthenium(II) complex has been developed that can efficiently catalyze hydromethylation of N-heteroarenes to form N-methyl saturated N-heterocycles viz the reduction of N-heterocycles coupled with C–N bond formation. Both indoles and quinolines can be transformed to their corresponding N-methyl indolines and N-methyl 1,2,3,4-tetrahydroquinolines with high conversion (e.g., 12 indoles and 9 quinolines). On the basis of a series of experiments, a possible mechanism has been proposed to account for the hydrogenation and methylation processes involved in the catalytic pathway. More importantly, this approach provides a potential route for using DME as a methyl source for the production of N-methyl saturated N-heterocycles via hydromethylation. [ABSTRACT FROM AUTHOR]

Quinoline and indole are important core structures in biologically active compounds and materials. Atropisomeric biaryls consisting of quinoline and indole are a unique class of axially chiral molecules. We report herein enantioselective synthesis of 3-(N-indolyl)quinolines having both C–N axial chirality and carbon central chirality by a photoredox Minisci-type addition reaction catalyzed by a chiral lithium phosphate/Ir-photoredox complex. The catalytic system enabled access to a unique class of 3-(N-indolyl)quinolines with high chemo-, regio-, and stereoselectivities in good yields through the appropriate choice of an acid catalyst and a photocatalyst. This is the first example of the synthesis of 3-(N-indolyl)quinoline atropisomers in a highly enantioselective manner. [ABSTRACT FROM AUTHOR]

Synthesis of functionalized benzo[a]phenazines and indazolo[2,3-a]quinolines has been developed through Rh(III)-catalyzed oxidative annulation of 2-arylquinoxalines and 2-aryl-2H-indazoles with allyl alcohols, respectively. The method features a broad substrate scope, excellent functional group tolerance, good to high yields of annulated products, and scaled-up synthesis capability. Based on a preliminary mechanistic investigation, a tentative mechanism of annulation reaction has been proposed. [ABSTRACT FROM AUTHOR]

Eighteen mononuclear copper(II) complexes with oxygen-containing N4O1 pentadentate ligands were prepared. The ligand library consists of 2-aminoethanol derivatives ((Ar1CH2)(Ar2CH2)NCH2CH2OCH2Ar3) bearing three nitrogen-containing heteroaromatics (Ars) including pyridine, quinoline and isoquinoline via a methylene linker. Systematic replacements of pyridine binding sites with quinolines and isoquinolines reveal the general trends in the perturbation of bond distances and angles, the redox potential and the absorption maximum wavelength of the copper(II) complexes, depending on the position and number of (iso)quinoline heteroaromatics. The small effect on the redox potentials resulting from quinoline substitution at the Ar3 position (near oxygen) of the ligand comes from the steric hindrance of the peri hydrogen atom in the quinoline moiety at this position, which removes the counter anion to enhance the coordination of quinoline nitrogen and ether oxygen atoms to the metal centre. In the absorption spectra of copper(II) complexes in the d–d transition region, the quinoline substitution at this site (Ar3) exhibits an opposite effect to those at the Ar1 and Ar2 sites. The electronic and steric contributions of the heteroaromatic binding sites to the ligand properties are comprehensively discussed. [ABSTRACT FROM AUTHOR]

Here, we report a series of four novel Cu complexes, namely 2-(piperidin-1-ylmethyl)quinoline copper(II) nitrate, [LACu(NO3)2] (Cu1), 4-(quinolin-2-ylmethyl)morpholine copper(II) nitrate, [LBCu(NO3)2] (Cu2), 4-(quinolin-2-ylmethyl)morpholine copper(II) chloride, [LBCuCl2] (Cu3), and 2-(piperidin-1-ylmethyl)pyridine copper(II) chloride, [LCCu(μ-Cl)Cl]2 (Cu4). X-ray diffraction studies revealed that the geometry around the Cu(II) center could be best described as distorted octahedral in Cu1 and Cu2, whereas Cu3 and Cu4 showed distorted tetrahedral and square pyramidal geometries, respectively. DNA binding studies showed that Cu complexes Cu1–3 containing quinoline interacted via minor groove binding, whereas the Cu4 complex containing pyridine interacted via intercalation. All Cu complexes containing quinoline and pyridine caused destabilization of DNA at specific homogeneous G–C regions. The Cu1–3 complexes as groove binders destabilized the DNA structure much more than the Cu4 complex as an intercalator. Regarding groove binders, the Cu2 complex containing quinoline and morpholine caused the highest distortion and destabilization of the DNA structure, leading to high DNA cleavage efficiency. [ABSTRACT FROM AUTHOR]

The document is a contents list for the journal Chemical Communications, providing information about the journal's mission and the articles featured in the current issue. It includes an article on the total synthesis of natural products and another on the photonic features of blue phase liquid crystals. The document also provides details about the editorial staff and contact information for inquiries. It concludes with information about subscription and payment options. Additionally, the document offers instructions for authors who wish to submit material for publication, guidelines for reproducing published contributions, and copyright information. [Extracted from the article]

Singly and doubly quinoline-fused BODIPYs were effectively synthesized through a reaction sequence consisting of the reduction of nitrophenyl-substituted BODIPYs and subsequent Pictet–Spengler cyclization. The combination of the BODIPY core and fused quinoline rings imposed significantly twisted conformations in the quinoline-fused BODIPYs (around 20.0° deviation from coplanarity obtained from X-ray crystal structure analysis). These twisted BODIPYs showed significantly reduced LUMO, redshifted absorption/emission bands, high molar extinction coefficients and satisfactory reactive oxygen species generation efficiency up to 0.56, indicating potential use as heavy-atom-free photosensitizers. [ABSTRACT FROM AUTHOR]

In the synthesis of medicinally and industrially valuable quinoline scaffolds, we report a one-pot greener synthetic route to do away with harsh reaction conditions, low productivity, and unstable substrates associated with the classical methods reported in the literature. Readily available alcohols undergo acceptorless dehydrogenative annulation in basic media over an engineered nitrogen-rich hollow-spherical microporous polymer (MOP-TA) devoid of any metal support. This affordable and sustainable route stands up to the test of scalability and green matrices, which are supported by various spectroscopic and microscopic techniques. [ABSTRACT FROM AUTHOR]

We propose a practical strategy to design a series of heavy-atom-free synergistic phototherapy agents (CSQs) with both photodynamic therapy (PDT) and photothermal therapy (PTT) under NIR wavelength excitation by simply replacing the indole salt of xanthene Changsha (CS) with quinoline salt. [ABSTRACT FROM AUTHOR]

Herein, a concise method for the Rh(III)-catalyzed, directing-group-assisted C–H/C–H cross-coupling of N-heterocycles (quinolines, indolines, indoles, pyridines, pyrimidines, pyrazoles) with other heteroarenes (benzoxazoles, benzofurans, and thiophenes) is disclosed for the synthesis of unsymmetrical heterobiaryl compounds in good to excellent yields. A plausible catalytic cycle has been delineated based on experimental and computational mechanistic studies. [ABSTRACT FROM AUTHOR]

One-pot processes which facilitate a number of tandem reactions, represent an environmentally friendly approach to building molecular complexity. In addition, there are significant cost and time saving benefits. However, unearthing multiple reactions that display substrate, reagent and solvent compatibility across two or more reactions, is not straightforward. This is even more pronounced when using catalysts, which by their nature, are present in small amounts and thus susceptible to poisoning. Herein we describe a phosphine-free, inorganic base free, multi-step, one-pot reaction sequence which enables the rapid synthesis of complex, medicinally relevant heterocycles in excellent yields. This Pd-catalysed approach combines Heck olefination, C–H activation, and hydrogenation, and the same pre-catalyst is involved in the three mechanistically distinct processes. Quinolines as substrates are used in the main, but we also provide a neat extension to pyridines and simple aryl substrates. Deuterium (D2) incorporation can be facilitated through use of the COware apparatus in the reduction step. Favourable mass productivity (MP), environmental impact factor (EF), solvent intensity (SI) and process mass intensity (PMI) values are reported. While the motivation to avoid problematic additives (inorganic base and P-ligands) and problematic solvent (DMA and NMP) was driven by a green agenda, the removal of reagents and additives in the context of one-pot strategies might also serve to reduce the bad actors and improve yields in one-pot processes. [ABSTRACT FROM AUTHOR]

The tandem isomerization–hydrosilylation reaction is a highly valuable process able to transform mixtures of internal olefins into linear silanes. Unsaturated and cationic hydrido-silyl-Rh(III) complexes have proven to be effective catalysts for this reaction. Herein, three silicon-based bidentate ligands, 8-(dimethylsilyl)quinoline (L1), 8-(dimethylsilyl)-2-methylquinoline (L2) and 4-(dimethylsilyl)-9-phenylacridine (L3), have been used to synthesize three neutral [RhCl(H)(L)PPh3] (1-L1, 1-L2 and 1-L3) and three cationic [Rh(H)(L)(PPh3)2][BArF4] (2-L1, 2-L2 and 2-L3) Rh(III) complexes. Among the neutral compounds, 1-L2 could be characterized in the solid state by X-ray diffraction showing a distorted trigonal bipyramidal structure. Neutral complexes (1-L1, 1-L2 and 1-L3) failed to catalyze the hydrosilylation of olefins. On the other hand, the cationic compound 2-L2 was also characterized by X-ray diffraction showing a square pyramidal structure. The unsaturated and cationic Rh(III) complexes 2-L1, 2-L2 and 2-L3 showed significant catalytic activity in the hydrosilylation of remote alkenes, with the most sterically hindered (2-L2) being the most active one. [ABSTRACT FROM AUTHOR]

Herein, we report the alkali-catalysed dehydrogenative coupling of amino alcohols and ketones. In this reaction, NaH (5–20 mol%) was employed as the sole catalyst, achieving efficient hydride transfer from the alpha-carbon of alcohol to the carbonyl carbon of ketone, and then the generated aldehyde intermediate was rapidly captured by the ketone to afford the products in good selectivity and yield. This protocol uses readily available starting materials and inexpensive catalysts without any transition metals and ligands and is easy and simple. [ABSTRACT FROM AUTHOR]

Quinolines are important building blocks for the synthesis of natural products and pharmaceuticals. In comparison with classical methods, dehydroaromatization of 1,2,3,4-tetrahydroquinolines has emerged in recent years as an efficient and straightforward way to access quinolines due to its high atom economy and sustainability. However, existing chemical methods suffer from the use of transition metal catalysts and harsh reaction conditions. Herein, we report a novel biocatalytic route for the efficient oxidative dehydrogenation of 1,2,3,4-tetrahydroquinolines employing monoamine oxidase from Pseudomonas putida KT2440 (PpMAO) with molecular oxygen, affording the corresponding quinolines with moderate to excellent yields (up to 99%) combined with the adjustment of the microenvironment for deprotonation and the supplied amount of molecular oxygen. Unlike other common one-step aromatizations of N-heterocycles, mechanism studies have suggested that PpMAO-catalyzed aromatization involves at least two-step C–N bond dehydrogenation reactions. The first step is the formation of an imine intermediate catalyzed by enzymes, followed by enzyme-mediated aromatization in the second step. Furthermore, preparative-scale biotransformation of tetrahydroquinolines was successfully demonstrated with good isolated yields (up to 95%). This system not only provided an efficient and facile method for the synthesis of quinolines under mild conditions but also enriched the redox biocatalytic approaches to N-heterocycles. [ABSTRACT FROM AUTHOR]

Dinuclear-gold-catalyzed radical difunctionalization of alkyl bromides with 1,7-enynes has been established via dehalogenation and 1,5-HAT processes. This protocol was used to construct, in a facile and efficient manner, a wide range of cyclopenta[c]quinolines bearing two quaternary carbon centers with good yields (28 examples, up to 84% yield). The good functional group compatibility and gram-scale preparation ability of the reaction proved its synthetic robustness. [ABSTRACT FROM AUTHOR]

The difficulty in isolating cyclic enamines emanating from their intrinsic instability has impeded their exploration in cycloaddition reactions. Here, we achieved a metal-free domino reaction providing quinoline and isoquinoline-derived cyclic amidines by the cycloaddition of azides with in situ generated enamines via dearomatization. [ABSTRACT FROM AUTHOR]

Creating new, environmentally friendly catalytic systems for producing C–C bonds from renewable feedstock is a challenging objective in synthetic chemistry. Traditional methods often use expensive noble metals, organic or organometallic reagents, or toxic halides with co-catalysts or additives. However, borrowing hydrogen (BH) or hydrogen auto-transfer (HAT) technology offers a simple and cost-effective alternative for creating C–C bonds using readily available alcohols as alkylating agents. This study shows that commercial TiO2 nanoparticles can act as a heterogeneous catalyst for C-alkylation reactions via a hydrogen-borrowing mechanism. The TiO2 catalyst was effective in producing high yields of C-alkylated products from acetophenones and primary alcohols, and reusability tests showed that the catalyst was robust and stable. The TiO2 catalyst was also capable of catalyzing multistep reactions to produce quinolines from 2-aminobenzyl alcohol and ketones with yields of up to 96.0%. Control experiments showed that the reaction pathway involved borrowing hydrogen. The use of this heterogeneous catalyst offers several advantages over traditional homogeneous catalysts, including lower cost, greater functional group tolerance, etc. [ABSTRACT FROM AUTHOR]

The current study addresses the usage of inherent redox couplets in PrVO4 crystallizing in a zircon-type structure for tandem oxidative transformation. Monophasic PrVO4, synthesized using a solution combustion synthesis method, showed a tetragonal zircon-type structure in its PXRD pattern (S.G. I41/amd). The tetragonal symmetry of the zircon PrVO4 was also confirmed from electron microscopic and vibrational spectroscopic measurements. From XPS analysis, the existence of redox couplets Pr3+/Pr4+ and V4+/V5+ in PrVO4 was established. The catalytic utility of zircon PrVO4 for one-pot synthesis of 2,3-disubstituted quinolines through the oxidative tandem reaction of 2-aminobenzylalcohols with 1,3-dicarbonyl compounds has been demonstrated. This highly efficient method proceeds under molecular oxygen, tolerates different functional groups, and produces various substituted quinoline derivatives in good to excellent yields. The important features of the process are the easy workup, simple catalyst recovery, and reusability. [ABSTRACT FROM AUTHOR]

A sustainable and environmentally benign biogenic technique for one-step synthesis of Ni-NPs (NiC2O4·2H2O-NPs) using Portulaca oleracea (purslane) leaf extract has been disclosed for the first time. The phytochemicals found in Portulaca oleracea leaf extract were found to serve as a reducing agent and subsequently act as a stabilizing agent. The various analytical and spectroscopic techniques confirm the formation of Ni-NPs. The catalytic potential of Ni-NPs was investigated to achieve cost-effective, sustainable, atom and step economic synthesis of pharmaceutically important quinazoline, 2-aminoquinoline, and N-(alkyl amino) quinoline via hydrogen auto transfer and acceptorless dehydrogenative annulation without the aid of external ligand and additives. Importantly, the photophysical property studies of the synthesized N-heterocycles are deliberated and gram-scale synthesis was achieved. Moreover, catalyst recyclability, control experiments, and mechanistic elucidation were elaborated. [ABSTRACT FROM AUTHOR]

A series of half-sandwich ruthenium complexes containing quinoline derivative ligands was synthesized, which had excellent antitumor toxicity toward a variety of cell lines and could localize lysosomes. The damage of lysosomes promotes the release of cathepsin B and initiates downstream apoptotic cascade signals. The increase in reactive oxygen species (ROS) caused by the decrease in mitochondrial membrane potential (ΔΨm) synergistically amplified the damage degree of lysosomes. In addition, the complex could inhibit cell transfer and clone formation. In vivo results showed that the complex had excellent biological effects in tested mouse samples as the body weight of mice did not change much during the treatment, and the mean tumor volume was significantly lower than the control group. [ABSTRACT FROM AUTHOR]

The first organoselenium-based quinoline probe was successfully synthesized and characterized by common spectroscopic techniques. The probe was found to be selective and sensitive for superoxide detection over other reactive oxygen species (ROS), biothiols and metal ions, bearing "turn-on" fluorescence response with high photostability. The probe emitted strong yellowish-green fluorescence in the presence of superoxide with a 64 fold increase in fluorescence intensity. The detection limit of the probe was found to be 1.57 μM. The theoretical calculations strongly support the ICT mechanism for turn-on response. In addition, an in vitro cytotoxicity study revealed strong anticancer activity of the probe compared to the standard drug cisplatin in lung carcinoma (A549) and breast cancer (MCF-7) cells. The significantly high IC50 value (65.21 μM) indicated the better biocompatibility of the probe for normal cells (MDCK) and that it will be a compelling medication for lung carcinoma cells (IC50 = 2.14 μM) and breast cancer cells (IC50 = 1.81 μM). [ABSTRACT FROM AUTHOR]

In this study, an improved microwave irradiation protocol was developed for synthesizing pyrido[2′,1′:2,3]imidazo[4,5-c]quinoline from 2-(2-bromophenyl)imidazo[1,2-a]pyridine and various benzaldehydes using copper iodide as a catalyst. This protocol also employed benzyl alcohols and methyl arenes in addition to benzaldehyde. The proposed mechanism was supported by DFT and ESI-HRMS studies. Tandem oxidative addition, reductive amination, and intramolecular cyclization under microwave conditions result in the formation of new C–N and C–C bonds, respectively. Among the synthesized derivatives, compounds 3k, 3o, 3u, and 3w exhibited antimycobacterial activity against M. tuberculosis H37Rv ATCC 27294. An in silico ADMET profile was also performed to assess the active compound's safety and efficacy. [ABSTRACT FROM AUTHOR]

An I2-mediated [3+2+1] aerobic cyclization reaction of anilines with alkynes and tertiary amines without any peroxides has been reported. This protocol employed tertiary amines as a C1 building block for the direct synthesis of 2-non, 2-alkyl, and even 2-aryl substituted quinolines via C–N bond cleavage. Differing from the traditional methods, both terminal and internal alkynes were compatible in this metal-free three-component system. It is possible that the 2-vinylbenzenamine species might be produced as one of the active intermediates in this process. [ABSTRACT FROM AUTHOR]

The Rh(III)-catalyzed C8-allylation of quinoline N-oxides has been accomplished using vinylcyclopropanes as an allyl source with excellent diastereoselectivity at room temperature. The C – H/C – C activation, substrate scope and natural product mutation are the important practical features. [ABSTRACT FROM AUTHOR]

Al-NDC@GO composites were hydrothermally prepared via a single step in situ synthesis through the reaction of 1,4-naphthalene dicarboxylic acid (1,4-H2NDC), Al(NO3)3·9H2O in H2O with graphene oxide (GO), and characterized well using various analytical techniques. The experimental results showed that Al-NDC@GO with optimal GO loading exhibited remarkable adsorption capacity for the liquid phase adsorption of pyridine, quinoline and indole in oil in the order of quinoline (670 mg quinoline per g) > pyridine (533 mg pyridine per g) > indole (487 mg indole per g), high adsorptive selectivity in the presence of naphthalene and benzene, and satisfactory recyclability. The mechanism behind this excellent adsorption of NCCs is thought to be due to the high surface area, porosity, and the presence of unsaturated metal sites and excessive oxygen groups on exfoliated layers of GO sheets, especially those that are not involved in bonding with Al-NDC moieties, because all these factors may be involved in the interaction of the composites and the nitrogen-containing compounds. [ABSTRACT FROM AUTHOR]

A rare example of a structurally characterized metal quinoline complex was prepared using a non-covalent quinoline-based proteasome inhibitor (Quin1), and a related complex bearing an inactive quinoline ligand (Quin2) was also synthesized. The quinolines are prepared by a one-pot procedure involving titanium-catalyzed alkyne iminoamination and are bound to ruthenium by reaction with CpRu(NCMe)3+ PF6− in CH2Cl2. The arene of the quinoline is η6-bonded to the ruthenium metal center. The kinetics of quinoline displacement were investigated, and reactivity with deuterated solvents follows the order acetonitrile > DMSO > water. Quinolines with more methyl groups on the arene are more kinetically stable, and RuCp(Quin1)+ PF6− (1), which has two methyl groups on the arene, is stable for days in DMSO. In contrast, a very similar complex (2) made with Quin2 having no methyl groups on the arene was readily displaced by DMSO. Both 1 and 2 are stable in 9 : 1 water/DMSO for days with no measurable displacement of the quinoline. The cytotoxicity of the quinolines, their CpRu+-complexes, and CpRu(DMSO)3+ PF6− was investigated towards two multiple myeloma cell lines: MC/CAR and RPMI 8226. To determine whether the activity of the complexes was related to the nature of the quinoline ligands, two structurally similar quinoline ligands with vastly different biological properties were investigated. Quin1 is a cytotoxic proteasome inhibitor, whereas Quin2 is not a proteasome inhibitor and showed no discernable cytotoxicity. The ruthenium complexes showed poor cellular proteasome inhibition. However, both 1 and 2 showed good cytotoxicity towards RPMI 8226 and MC/CAR, with 1 being slightly more cytotoxic. For example, 1 has a CC50 = 2 μM in RPMI 8226, and 2 has a CC50 = 5 μM for the same cell line. In contrast, CpRu(DMSO)3+ PF6− was quite active towards MC/CAR with CC50 = 2.8 μM but showed no discernible cytotoxicity toward RPMI 8226. The mechanism of action responsible for the observed cytotoxicity is not known, but the new Ru(Cp)(Quin)+ PF6− complexes do not cross-link DNA as found for platinum-based drugs. It is concluded that the Ru(Cp)(Quin)+ PF6− complexes remain intact in the cellular assays and constitute a new class of cytotoxic metal complexes. [ABSTRACT FROM AUTHOR]

Cu(II) complexes supported by tetradentate amido-quinoline acyclic ligands (L1 & L2) have been synthesized, characterized, and employed as catalysts for aromatic C–H hydroxylation using H2O2 as an oxidant in the absence of an external base with a high selectivity of around 90% for phenols via the non-radical pathway (TON ≥720). The KIE value, various spectroscopic studies and DFT calculation supported the involvement of Cu(II)–OOH species. [ABSTRACT FROM AUTHOR]

Polycyclic heterocycles such as 1- and 2-aminothioxanthones are important precursors to molecules endowed with different properties and original syntheses are always required. Here, 1-aminothioxanthone was obtained either in four steps from commercially available thioxanthone, or in five steps from 3-fluoroaniline. As for 2-aminothioxanthone, direct N-arylation using commercial 2-chlorothioxanthone gave its Boc-protected derivative. From 1-aminothioxanthone, original 10-methylbenzothiopyrano[4,3,2-de]indolo[2,3-b]quinoline was synthesized by tandem N-arylation-cyclization using 2-iodo-N-methylindole in the presence of copper. However, this approach being less efficient with 2-iodobenzothiophene, we also studied another strategy. Our efforts were next concentrated on the synthesis of benzofuro-, benzothieno- and indolo[2,3-b]benzothiopyrano[4,3,2-de]1,8-naphthyridines which are original hexacycles of helical nature. Different approaches were designed and we achieved our goal from 2-chloro-4-fluoropyridine, in five steps. The original polycyclic compounds obtained were evaluated as protein kinase inhibitors, and the results were rationalized by molecular modeling experiments. Finally, their photophysical properties were measured for the purpose of structure-property relationships. [ABSTRACT FROM AUTHOR]