2,4‐Dichlorophenyl Acrylate/8‐Quinolinyl Methacrylate Copolymers: Ion‐Exchange Study

The chelating ion‐exchange properties of the 2,4‐dichlorophenyl acrylate (2,4‐DCPA)/8‐quinolinyl methacrylate (8‐QMA) copolymers, synthesized using different monomer feed ratios, were investigated by the batch equilibrium method. Five metal ions Cu⁺², Ni⁺², Co⁺², Zn⁺², and Fe⁺³ were used to evaluate the cation‐exchanger capability of 2,4‐DCPA‐co‐8‐QMA copolymers. The ion‐exchange study was carried out for three different experimental variables viz., pH of the aqueous medium, ionic strength of electrolyte and shaking time. It was observed that due to the presence of a pendant ester‐bound quinolinyl group, the copolymers are better suited as cation exchangers.     

Molecular Recognition by Zn(II)-Capped Dynamic Foldamers

Two α-aminoisobutyric acid (Aib) foldamers bearing Zn(II)-chelating N-termini have been synthesized and compared with a reported Aib foldamer that has a bis(quinolinyl)/mono(pyridyl) cap (BQPA group). Replacement of the quinolinyl arms of the BQPA-capped foldamer with pyridyl gave a BPPA-capped foldamer, then further replacement of the linking pyridyl with a 1,2,3-triazole gave a BPTA-capped foldamer. Their ability to relay chiral information from carboxylate bound to Zn(II) at the N-terminus to a glycinamide-based NMR reporter of conformational preference at the C-terminus was measured. The importance of the quinolinyl arms became readily apparent, as the foldamers with pyridyl arms were unable to report on the presence of chiral carboxylate in acetonitrile. Low solubility, X-ray crystallography and ¹H NMR spectroscopy suggested that interfoldamer interactions inhibited carboxylate binding. However changing solvent to methanol revealed that the end-to-end relay of chiral information could be observed for the Zn(II) complex of the BPTA-capped foldamer at low temperature.     

Rhodium Bis(quinolinyl)benzene Complexes for Methane Activation and Functionalization

A series of rhodium(III) bis(quinolinyl)benzene (bisq^x) complexes was studied as candidates for the homogeneous partial oxidation of methane. Density functional theory (DFT) (M06 with Poisson continuum solvation) was used to investigate a variety of (bisq^x) ligand candidates involving different functional groups to determine the impact on Rh^III(bisq^x)‐catalyzed methane functionalization. The free energy activation barriers for methane C?H activation and Rh–methyl functionalization at 298 K and 498 K were determined. DFT studies predict that the best candidate for catalytic methane functionalization is Rh^III coordinated to unsubstituted bis(quinolinyl)benzene (bisq). Support is also found for the prediction that the η²‐benzene coordination mode of (bisq^x) ligands on Rh encourages methyl group functionalization by serving as an effective leaving group for S_N2 and S_R2 attack.     

One-pot synthesis of methyl piperazinyl–quinolinyl nicotinonitrile derivatives under microwave conditions and molecular docking studies with DNA

Derivatives of methyl piperazinyl–quinolinyl nicotinonitrile were synthesised by one-pot method under microwave conditions. This was achieved using the Knoevenagel condensation reaction. The novel derivatives described above were purified by column chromatography and characterised by FT-IR, ¹H, ¹³C, 2D-NMR and HRMS spectroscopic techniques. Furthermore, molecular docking was used to determine the binding sites of DNA with selected compounds. The synthetic method developed in this study showed several advantages including simplicity, high yield of products, coupled with safety and a short reaction time of 15 min.     

Synthesis and Antimicrobial Studies of Some Quinolinylpyrimidine Derivatives

The quinolinylpyrimidine derivatives were prepared by the condensation of quinolinyl chalcones with urea (or thiourea) under basic conditions by using both conventional and microwave heating. Their IR, ¹H NMR, ¹³C NMR, mass spectra and CHN analyses confirmed the prepared compounds. The newly prepared quinolinylpyrimidine derivatives were screened for antimicrobial activities against the bacterial strains viz. S. aureus, Shigella, Salmonela, P. aeroginosa, B. Subtilus and E. coli and found considerably active against S. aureus, P. aeroginosa and E. coli.     

Reactions of 4‐dimethylamino‐3‐quinolinyl sulfides with nitrating mixture and transamination of 4‐dimethylamino‐3‐methylsulfinyl‐6‐nitroquinoline

4‐Amino‐3‐quinolinyl sulfides 4d‐e and 7a‐c were prepared by amination of 4‐chloro‐3‐quinolinyl sulfides 4c or 1c , respectively, in methanol (140‐160 °C) or in boiling phenol with yields up to 95 %. Reaction of 4‐dimethylamino‐3‐quinolinyl sulfides 7c and 4e with nitrating mixture proceeded simultanously as oxidation of the methylthio group to the methylsulfinyl one and as C6‐nitration to form 6‐nitro‐β‐quinolinyl sulfoxides 9c or 10b , respectively. 4‐Dimethylamino‐3‐methylsulfinyl‐6‐nitroquinoline 9c underwent acid catalysed transamination when reacting with primary aliphatic amines and ammonia.     

Microwave Synthesis of Fused Pyrans by Humic Acid Supported Ionic Liquid Catalyst and Their Antimicrobial,Antioxidant, Toxicity Assessment,and Molecular Docking Studies

A series of fused quinolinyl and quinolonyl pyrans were synthesized via a one‐pot reaction of quinolinyl and quinolonyl carbaldehydes, malononitrile, and a 1,3‐diketone. The reactions were catalyzed by a new humic acid supported 1‐butyl‐3‐methyl imidazolium thiocyanate ionic liquid under microwave irradiation conditions. Antimicrobial, antioxidant, and toxicity studies displayed various biological activities depending on structure of the pyrans.     

Competition between S‐oxidation and nitration in reactions of some β‐ and γ‐quinolinyl sulfides with nitrating mixture

This study was performed in order to explain different orientation in the reaction of quinolinyl sulfides with nitrating mixture, which converted on one hand quinolinyl sulfides 1 , 3 and 5 to sulfoxides 2 , 4 and 8 , respectively, on the other hand, sulfides 6 , 7 to the respective nitroderivatives 9 and 10 . Competitive experiments showed following reactivity order: thianthrene 11 ≥ thianthrene 5‐oxide 12 ≥ isothioquinanthrene 3 ≥ thioquinanthrene 1 ≥ 3,3′‐diquinolinyl sulfide 5 ≥ 3,4′‐diquinolinyl sulfide 6 ≥ 4,4′‐diquinolinyl sulfide 7 . Considering that NO₂⁺ (as reactive form of nitrating mixture) attacks the most electronodonating (sulfur or carbon) center the reactivity order well correlates with the results of HOMO as well as MEP calculations.     

Syntheses of tetraquinolinyl substituted pyrene, diphenylacetylene, and trans-stilbene ligands

We report the syntheses and characterizations of quinolinyl functionalized di-t-butyl-pyrene, diphenylacetylene, and trans-stilbene ligands.     

Light Emitting Materials and Devices of PPV Type Compounds Containing Quinolines

Five derivatives of 1,4‐bis(2′‐quinolinylethenyl)benzene were prepared through Wittig reaction of a diylide of p‐xylene and two molar equivalents of quinolinyl carbaldehyde. Dyes 1a,b and 2a‐c thus obtained exhibit fluorescence in quantum yields of 0.44–0.78. They are fabricated to light‐emitting diodes in the form of ITO/NPB/CBP/TPBI: dye(5% wt)/Mg: Ag. The devices can be turned on at 6 V, and they displayed blue and green light at intensities up to 5000 cd/m² at 15 V. The compounds containing methoxy substituents, i.e. 1b and 2b,c , performed more effectively than those without, i.e. 1a and 2a . The former derivatives also showed a red‐shift in their emission spectra with respect to the latter.     

Transformations of schiff bases derived from quinoline‐8‐carbaldehyde. Synthesis of C‐8 substituted quinolines

The Schiff bases derived from quinoline‐8‐carbaldehyde and substituted aromatic amines were used in the synthesis of C‐8 substituted quinolines. 3‐Aryl‐2‐(8‐quinolinyl)‐4‐thiazolidinones were prepared from obtained aldimines by means of the cyclocondensation of mercapto acids. A series of 4‐N‐arylamino‐4‐(8‐quinolinyl)‐1‐butenes was synthesized through the addition of the Grignard reagent (allylmagnesium bromide) to the double bond C=N of these aldimines. The structure of the prepared compounds was established on the basis of their elemental analyses and spectral data.     

Highly Efficient Dye‐Sensitized Solar Cells Based on Panchromatic Ruthenium Sensitizers with Quinolinylbipyridine Anchors

Panchromatic Ru^II sensitizers TF‐30–TF‐33 bearing a new class of 6‐quinolin‐8‐yl‐2,2′‐bipyridine anchor were synthesized and tested under AM1.5 G simulated solar irradiation. Their increased π conjugation relative to that of the traditional 2,2′:6′,2′′‐terpyridine‐based anchor led to a remarkable improvement in absorptivity across the whole UV–Vis–NIR spectral regime. Furthermore, the introduction of a bulky tert‐butyl substituent on the quinolinyl fragment not only led to an increase in the J_SC value owing to the suppression of dye aggregation, but remarkably also resulted in no loss in V_OC in comparison with the reference sensitizer containing a tricarboxyterpyridine anchor. The champion sensitizer in DSC devices was found to be TF‐32 with a performance of J_SC=19.2 mA cm^?2, V_OC=740 mV, FF=0.72, and η=10.19 %. This 6‐quinolin‐8‐yl‐2,2′‐bipyridine anchor thus serves as a prototype for the next generation of Ru^II sensitizers with any tridentate ancillary.     

Theoretical study on a chemosensor for fluoride anion‐based on a urea derivative

The sensing mechanism of the N‐Phenyl‐N′‐(3‐quinolinyl)urea (PQU) chemosensor for fluoride anion has been investigated by density functional theory/time‐dependent density function theory. The double intermolecular hydrogen bonds are formed between the three anions (X^??F^?, AcO^?, Cl^?) and the urea fragment of PQU. In the S₀ states, the H_b? X^? hydrogen bonds are slightly stronger than the H_a? X^? hydrogen bonds and the fluoride‐induced deprotonation occurs at the N? H_b position rather than at the N? H_a position. Consequently, the absorption peaks, including an intramolecular charge transfer transition and a ππ* transition, are significantly red‐shifted. Thermodynamic calculations confirm that the deprotonation in the ground state is favorable in energy only when excess fluoride anion exists. Along with the S₀ → S₁ transition, the H_a? X^? hydrogen bonds strengthen and the H_b? X^? hydrogen bonds weaken. However, the emission spectra of [PQU‐H_b]^?, instead of [PQU‐H_a]^?, are observed upon addition of fluoride anion. © 2013 Wiley Periodicals, Inc.     

Enantioselective Allylic Oxidation of Olefins Using Chiral Quinolinyl‐oxazoline Copper Complex Catalysts

Copper complexes of chiral quinolinyl‐oxazoline have been studied as the catalysts for enantioselective allylic oxidation of cycloalkenes with tert‐butyl perbenzoate. Using 5 mol% of these chiral catalysts, optical active allylic benzoates were obtained in moderate enantiomeric excesses. CuOTf prepared in situ, CuClO₄ and CuPF₆ were found to be good precatalysts in acetone.     

Derivatives of some cyclic 3,4‐quinolinediyl bis‐sulfides with N,N‐dimethylcarbamoyl and N‐methyl‐N‐formylaminornethyl substituents in the 2‐quinolinyl position

Reactions of hydrogen sulfates of quino‐ and diquino‐annelated 1,4‐dithiins 11 and 2 with DMF/hydroxylamine‐O‐sulfonic acid/Fe⁺⁺ ion system took place at the α‐quinolinyl positions and led to N,N‐dimethylcarbamoyl and N‐methyl‐N‐formylaminomethyl derivatives 6 , 8 , 12 and 7 , 9 , 13 , respectively. The ¹H and ¹³C NMR spectra of N‐methyl‐N‐formylaminomethyl derivatives 7 , 9 , 13 showed the presence of rotational isomers E and Z regarding to the N‐methyl‐N‐formylaminomethyl substituent. The spectra of 6 , 7 , 8 , 12 and 13 were completely assigned with the use of 1D and 2D NMR techniques. In the case of rotational isomers 7a and 7b , the crucial correlations came from the NOE interaction between the methylene and methyl protons from CH₂N(CH₃)CHO groups and benzene‐rings protons. Synthesis of 2,3‐dihydro‐1,4‐dithiino[6,5‐e]quinoline 4‐oxide 14 was presented as well.     

Functionalization of Pyridine and Quinoline Scaffolds by Using Organometallic Li-, Mg- and Zn-Reagents

This Review discusses the various methods for functionalizing pyridine and quinoline scaffolds, including direct selective metalation (DoM), halogen/metal exchange reactions, Li, Mg, and Zn insertion, and trans-metalation approaches, which are then followed by cross-coupling reactions of the Kumada or Negishi types. Selective deprotonation of aryl or pyridyl/quinolinyl derivatives can be performed using n-BuLi, LDA, and TMP-based different organolithium, -magnesium, and -zinc reagents. The functionalized pyridine and quinoline-based heterocyclic compounds were prepared by selectively deprotonating with presenting a directing functional group substituted pyridine/quinoline analogues in the presence of TMP-bases (TMP−Li, Mg, Zn reagents). Different aryl or alkyl Li, Mg, and Zn reagents with electron-donating and electron-withdrawing substituents undergo transition metal-catalyzed C(sp²)−C(sp²) and C(sp²)−C(sp³) types of cross-coupling reactions with pyridine/quinoline halides under mild conditions with the sustainable process producing complex N-heterocycles. Using moderate and sustainable reaction conditions, sensitive functional group tolerance, and inexpensive and low toxic chemicals, highly functionalization of pyridine and quinoline-based bioactive therapeutic scaffolds and natural products was accomplished. Therefore, in this article, we provide a succinct overview of the numerous synthetic strategies and practical methods used by various authors between 2010 and 2023 to functionalize pyridine and quinoline analogues using diverse Li, Mg, and Zn organometallic reagents.     

Synthesis and reactivity of lithium tri(quinolinyl)magnesates

2-, 3- and 4-Bromoquinolines were converted to the corresponding lithium tri(quinolinyl)magnesates at −10°C when exposed to Bu₃MgLi in THF. The resulting organomagnesium derivatives were quenched with various electrophiles or involved in metal-catalyzed coupling reactions with heteroaryl halides to afford functionalized quinolines.     

Manipulating electron transfer – the influence of substituents on novel copper guanidine quinolinyl complexes

Copper guanidine quinolinyl complexes act as good entatic state models due to their distorted structures leading to a high similarity between Cu(i) and Cu(ii) complexes. For a better understanding of the entatic state principle regarding electron transfer a series of guanidine quinolinyl ligands with different substituents in the 2- and 4-position were synthesized to examine the influence on the electron transfer properties of the corresponding copper complexes. Substituents with different steric or electronic influences were chosen. The effects on the properties of the copper complexes were studied applying different experimental and theoretical methods. The molecular structures of the bis(chelate) copper complexes were examined in the solid state by single-crystal X-ray diffraction and in solution by X-ray absorption spectroscopy and density functional theory (DFT) calculations revealing a significant impact of the substituents on the complex structures. For a better insight natural bond orbital (NBO) calculations of the ligands and copper complexes were performed. The electron transfer was analysed by the determination of the electron self-exchange rates following Marcus theory. The obtained results were correlated with the results of the structural analysis of the complexes and of the NBO calculations. Nelsen''s four-point method calculations give a deeper understanding of the thermodynamic properties of the electron transfer. These studies reveal a significant impact of the substituents on the properties of the copper complexes.

Copper guanidine quinolinyl complexes act as good entatic state models for the electron transfer due to a high similarity between the corresponding Cu(i) and Cu(ii) complexes. The introduction of substituents leads to a further enhancement.     

Synthesis and Transformations of Substituted 3,3′-Diquinolinyl Sulfides

Abstract

Reactions of the 1,4-dithiin ring opening in 1,4-dithiinodiquinoline 1 with selected oxygen nucleophiles followed by S- and N-alkylation led to sulfides possessing one or two quinolinyl or quinolonyl units. Diquinolinyl sulfides 2 were transformed into quinolinyl-quinolonyl sulfides 3 or diquinolonyl sulfides 9 via thermal rearrangement (the O-N alkyl migration) or hydrolysis of the alkoxy and alkylthio groups with the hydrochloric acid-ethanol mixture.