Quinoline Fragment Research Articles

SYNTHESIS OF 8-HYDROXYQUINOLINE CHALCONES: TRANS CONFIGURATION, INTRAMOLECULAR HYDROGEN BONDS, BROMINATION, AND ANTIFUNGAL ACTIVITY

ABSTRACT Nine (8-Hydroxyquinolin-5-yl)-arylpropenones were synthesized and their structures demonstrated by IR and NMRspectroscopy. These molecules showed transconfiguration and strong intramolecular hydrogen bonding; in the IR spectra of 5-formyl-8-hydroxyquinoline, 5-acetyl-8-hydroxyquinoline, 1-(8-hydroxyquinolin-5-yl)-3-phenylprop-2-en-1-one and 3-(8-hydroxyquinolin-5-yl)-1-phenylprop-2-en-1-one in CHCl 3 , besides the known intermolecular hydrogen band (~3180 сm -1 ), we identified the intramolecular hydrogen band ОН ... N (3460 сm -1 ); the hydrogen bond peaks shifted to low frequency in proton-donor solutions such as phenol and acetic acid (with respect to 8-hydroxyquinoline) and the bonds were broken in trifluoroacetic acid solutions, due to OH protonation; the apolar solvent CCl 4 and electrophilic substituents in position 5 in the quinoline ring, limited the formation of the intermolecular hydrogen bonds and, therefore, shifted the ~3460 сm -1 intramolecularhydrogenband to lower frequencies and made it stronger and sharper. The bromination of 3-(8-hydroxyquinolin-5-yl)-1-(4-tolyl) prop-2-en-1-one occurred on the activated quinoline fragment, producing monobromo and tetrabromo derivatives, instead of bromination on the aliphatic double bond. Three chalcones tested showed strong antifungal activity

Synthesis, structure, and blue photoluminescence of the coordination chain polymer [Cd2(L)Cl4] n (L = 2-(3,5-dimethylpyrazol-1-yl)-4-methylquinoline)

The complex of CdCl2 with 2-(3,5-dimethylpyrazol-1-yl)-4-methylquinoline (L), Cd2(L)Cl4 (I), is synthesized. According to the X-ray diffraction data, the structure of coordination polymer I is formed by chains in which two crystallographically independent Cd atoms linked by the bridging Cl atoms have different coordination numbers (5 and 6) and different environments. Five Cl atoms form the coordination polyhedron of the Cd(2) atom: a square pyramid (Cd-Cl 2.554(3)–2.689(3) A) completed to a bipyramid by the CI atom at a substantially longer distance of 2.865(4) A. Two Cl atoms and the N atom of quinoline fragment L are arranged in the equatorial plane of the coordination polyhedron of the Cd(1) atom, which is a distorted trigonal bipyramid. The axial vertices are occupied by the N atom of the pyrazole cycle of L and the Cl atom. Five-membered metallocycles CdCN3 are formed upon the coordination of bidentate chelating ligands L. The planes of L of two adjacent chains are parallel (the distances between them are ∼3.5 A), which suggests the π-π interaction between the planes. The luminescence excitation spectrum of compound I has a broad band with λmax = 350 nm. The spectrum of bright blue photoluminescence of compound I (300 K, λexc = 340 nm) contains an intense band with λmax = 420 nm.

Synthesis and photoluminescence of the chiral compounds [ZnLCl2] · EtOH and ZnLCl2, where L is the (+)-3-Carene derivative containing pyrazoline and quinoline fragments: crystal structure of [ZnLCl2] · EtOH

The following chiral compounds were synthesized: [ZnLCl2] · EtOH (I) and ZnLCl2 (II), where L is the pyrazolin-5-ol derivative obtained from terpene (+)-3-carene. According to the X-ray diffraction data, the crystal structure of compound I is built of acentric molecules of the mononuclear ZnLCl2 complex and EtOH molecules. In molecules of the complex, the Zn2+ ion is coordinated by two N atoms of the bidentate chelating ligand L and two Cl atoms at the vertices of the distorted tetrahedron. The intermolecular contacts and the hydrogen bonds Cl(1)…H-O(1) between the adjacent ZnLCl2 molecules result in the formation of chains parallel to the y axis. The reactant L and solvate I possess weak photoluminescence in the visible spectral range. Complex II exhibits more intense photoluminescence at λmax = 416 and 517 nm.

2-(2-Furyl)-1(3)H-imidazo[4,5-f]quinoline. Synthesis and electrophilic substitution reactions

2-(2-Furyl)-1(3)H-imidazo[4,5-f]quinoline was synthesized by the Weidenhagen reaction of quinoline-5,6-diamine with furfural. Its alkylation with methyl iodide in the system KOH-DMSO gave two isomeric N-methyl derivatives, 2-(2-furyl)-1-methyl-1H- and 2-(2-furyl)-3-methyl-3H-imidazo[4,5-f]quinolines, the latter prevailing. 2-(2-Furyl)-3-methyl-3H-imidazo[4,5-f]quinoline was brought into electrophilic substitution reactions: bromination, nitration, formylation, acylation, sulfonation. Depending on the reaction conditions, electrophilic attack could be directed at both furan ring and quinoline fragment.

Development of the catalytic synthesis of compounds of the quinoline series (the N. S. Kozlov reaction) (Review)*

This article is dedicated to the 80th anniversary of the Institute of Physical Organic Chemistry, National Academy of Sciences of Belarus (in 1929-1959 the Institute of Chemistry, Academy of Sciences of the BSSR). It contains a review of the advances in the synthesis and properties of condensed heterocyclic systems containing a quinoline fragment – derivatives of quinaldine, benzo[f]quinoline, indeno- and indoloquinoline, benzo[a]phenanthridine, benzoacridine, tetrahydroquinoline, 1,7- and 4,7-phen-anthroline. The reactions forming the basis of the synthesis of the heterocycles are described – catalytic reaction of amines with acetylene, catalytic condensation of azomethines with methyl and α-methylene ketones, triple-component condensation of arylamines, carbonyl compounds, and CH acids.

Fluorescence properties of polyamines bearing two terminal quinoline fragments in water

Fluorescence properties of polyamines bearing two terminal quinoline fragments with different polyamine chain length, such as ethylenediamine ( L0), diethylenetriamine ( L1), and triethylenetetramine ( L2), have been studied in water. These ligands show Zn 2+-induced fluorescence enhancement, while showing almost no enhancement with other cations. However, stability constants for Zn 2+ coordination and fluorescence response against Zn 2+ depend strongly on the polyamine chain length. The chain length also affects the fluorescence wavelength. The Zn 2+– L1 and Zn 2+– L2 complexes show emission at 410 nm, while Zn 2+– L0 complexes show a blue-shifted emission at 375 nm due to the partial charge transfer from the excited state quinoline to the Zn 2+ center.

4-(6-Quinolyloxymethyl)benzonitrile

The title compound, C17H12N2O, was synthesized by an ether synthesis from quinolin-6-ol and 4-(bromo­meth­yl)benzonitrile. The phenyl ring of the benzonitrile group makes a dihedral angle of 47.52 (6)° with the plane of the quinoline fragment. The crystal structure is stabilized by inter­molecular C—H⋯π inter­actions between a benzene H atom of the benzonitrile group and the benzene ring of the quinoline fragment. In addition, the crystal structure also exhibits a weak inter­molecular C—H⋯N hydrogen bond.

Synthesis of the pentacyclic core of lihouidine

The pentacyclic base of the sponge-derived alkaloid lihouidine has been assembled from two quinoline fragments. The key step is a nitration-promoted cyclization to form the C–C bond between the two quinoline units.

2-(5,7-Dichloroquinolin-8-yloxy)-N,N-diphenylacetamide

In the title compound, C23H16Cl2N2O2, intra­molecular C—H⋯Cl and C—H⋯N hydrogen bonds from the quinoline fragment form five- and six-membered rings, respectively. The quinoline ring system makes dihedral angles of 30.42 (1) and 81.17 (1)° with the phenyl rings of the diphenyl­acetamide fragment. In the crystal structure, mol­ecules are linked into chains along the b axis by inter­molecular C—H⋯O hydrogen bonds.

2-(5,7-Dibromoquinolin-8-yloxy)-N,N-diphenylacetamide

In the title compound, C23H16Br2N2O2, intra­molecular C—H⋯Br and C—H⋯N hydrogen bonds from the quinoline fragment form two five-membered rings. The quinoline ring system makes dihedral angles of 81.6 (2) and 31.2 (2)° with the phenyl rings of the diphenyl­acetamide fragment. In the crystal structure, mol­ecules are linked into chains along the b axis by inter­molecular C—H⋯O hydrogen bonds.

A quinoline–polyamine conjugate as a fluorescent chemosensor for quantitative detection of Zn(II) in water

A simple ligand ( L1), a diethylenetriamine bearing two end quinoline fragments, was synthesized. Without metal cations, L1 shows no fluorescence at pH 2–13; however, Zn 2+ addition creates strong fluorescence at pH 5–12. The emission intensity exhibits linear and stoichiometrical response to the Zn 2+ amount. No remarkable emission enhancement was, however, observed for other cations.

Photo-and thermochromic spiranes. 29. New photochromic indolinospiropyrans containing a quinoline fragment

A new photochromic spiropyran of the indoline series, containing a quinoline fragment, has been synthesized. The photochromic properties of the spiropyran and its iodomethylate have been studied. Features of the molecular structure of the compounds were determined by X-ray structural investigations. It was established that the pyridopyran fragments of the cations in the crystal of the iodomethylate salt, unlike those in the crystal of the neutral spiropyran, emerge from 21-stacks, disposed jointly with I− ions, which causes their higher mobility and aids the course of reversible photoconversions on UV irradiation in solution.

Novel Photochromic Indolinospiropyrans Containing a Quinoline Fragment Condensed with a 2H‐Pyran Ring

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2-Aminoquinolin-8-ylp-toluenesulfonate

The essentially planar quinoline fragment and the aromatic ring of the toluene­sulfonate group of the title compound, C16H14N2O3S, form a dihedral angle of 52.2 (1)°; the torsion angle about the central bridge C—O—S—C is −69.3 (2)°. The N—H⋯N and N—H⋯O hydrogen bonds, involving the H atoms of the amino group and the quinoline and sulfonyl N and O atoms [N⋯N = 3.055 (3) A and N⋯O = 3.058 (2) A], link the mol­ecules into dimers; a C—H⋯O inter­action formed by the CH group in position 4 of the quinoline group [C⋯O = 3.293 (3) A] further links the dimers into infinite chains running along the diagonal of the ab plane.

Excited-State Proton Transfer through Water Bridges and Structure of Hydrogen-Bonded Complexes in 1H-Pyrrolo[3,2-h]quinoline: Adiabatic Time-Dependent Density Functional Theory Study

Proton transfer reaction is studied for 1H-pyrrolo[3,2-h]quinoline-water complexes (PQ-(H(2)O)(n), n = 0-2) in the ground and the lowest excited singlet states at the density functional theory (DFT) level. Cyclic hydrogen-bonded complexes are considered, in which water molecules form a bridge connecting the proton donor (pyrrole NH group) and acceptor (quinoline nitrogen) atoms. To understand the effect of the structure and length of water bridges on the excited-state tautomerization in PQ, the potential energy profile of the lowest excited singlet state is calculated adiabatically by the time-dependent DFT (TDDFT) method. The S(0) --> S(1) excitation of PQ is accompanied by significant intramolecular transfer of electron density from the pyrrole ring to the quinoline fragment, so that the acidity of the N-H group and the basicity of the nitrogen atom of the quinoline moiety are increased. These excited-state acid-base changes introduce a driving force for the proton transfer reaction. The adiabatic TDDFT calculations demonstrate, however, that the phototautomerization requires a large activation energy in the isolated PQ molecule due to a high energy barrier separating the normal form and the tautomer. In the 1:1 cyclic PQ-H(2)O complex, the energy barrier is dramatically reduced, so that upon excitation of this complex the tautomerization can occur rapidly in one step as concerted asynchronous movements of the two protons assisted by the water molecule. In the PQ-(H(2)O)(2) solvate two water molecules form a cyclic bridge with sterically strained and unfavorable hydrogen bonds. As a result, some extra activation energy is needed for initiating the proton dislocation along the longer hydrogen-bond network. The full tautomerization in this complex is still possible; however, the cooperative proton transfer is found to be highly asynchronous. Large relaxation and reorganization of the hydrogen-bonded water bridge in PQ-(H(2)O)(2) are required during the proton translocation from the pyrrole NH group to the quinoline nitrogen; this may block the complete tautomerization in this type of solvate.

Theoretical and UV spectral study of isomeric 1-(quinolinyl)-β-carbolines conformations

On the basis of β-carboline ( 1) and 1-(quinolin-2′-yl)-β-carboline ( 3) α- and t-band energies differences ( Δ α,t) a equilibrium conformations of 1-(quinolin-4′(5′-8′)-yl)-β-carbolines ( 4– 8) in solution have been estimated. Furthermore, as an example of model compounds 1-(α′-naphtyl)-β-carboline (MC1) and 1-(β′-naphtyl)-β-carboline (MC2) and also 5 and 6 by molecular mechanics (mm+), semi-empirical (AM1) and none empirical (RHF/6-31G(d)) methods a computations of internal rotation of quinoline fragment around single bond have been performed. It was found that the greater bathochromic shift of the long-wavelength band maxima of 1, in the case of 3 (Δ λ max = 39 nm) relatively to 6, 7 (Δ λ max = 17 ± 2 nm) and 4, 5, 8 (Δ λ max = 9 ± 1 nm) caused by coplanarity of the molecule 3. Also, from experimental and theoretical investigations a less dihedral angle between β-carboline and quinoline nucleous for 6, and 7 than 4, 5 and 8 owing to steric and electronic interactions have been found.

Novel photochromic indolinospiropyrans containing a quinoline fragment condensed with a 2H-pyran ring

Novel photochromic indolinospiropyrans containing a quinoline fragment condensed with a 2H-pyran ring

Folipidine, a New Type Quinoline Alkaloid from Plants of the Haplophyllum Genus

The new quinoline alkaloid folipidine, the structure of which was established by chemical transformations and spectral data (UV, IR, mass, NMR) using APT, 2D 1H-1H COSY, NOESY, and 1H-13C HSQC, HMBC, was isolated from two plants of the Haplophyllum genus. Folipidine is the first representative of a new type of quinoline alkaloids that contain a heteroaromatic skeleton of [3,4-b] conjugated pyrrole and quinoline fragments. The total alkaloids of these plants exhibit antitumor activity. Folipidine does not possess such activity.

In situ Characterization of the Adsorption of Cinchona Chiral Modifiers on Platinum Surfaces

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In situ characterization of the adsorption of cinchona chiral modifiers on platinum surfaces

Graphic The adsorption of cinchona chiral modifiers on platinum surfaces has been characterized with surface-sensitive techniques. The uptakes of quinoline and lepidine, models for the aromatic moiety of the cinchona, were first studied on Pt(1 1 1) single crystal surfaces and under ultrahigh vacuum by reflection–absorption infrared spectroscopy (RAIRS). Adsorption at low (∼100 K) temperatures is molecular and without any preference for a distinct molecular geometry. Temperature programmed desorption (TPD) experiments indicated extensive dehydrogenation starting at about 250 K, and infrared data obtained at room temperature corroborated the conversion of some of the aromatic CH bonds to a more aliphatic environment. An in situ RAIRS characterization of the adsorption of cinchonidine from carbon tetrachloride solutions onto a polycrystalline platinum substrate proved that in hydrogen-treated solvents the decomposition of the adsorbate is inhibited, so that the cinchona retains its molecular character on the surface at room temperature. Three adsorption regimes were identified depending on the concentration of cinchonidine in solution, namely, no observable adsorption at low concentrations, bonding via a flat-lying quinoline moiety in the intermediate concentration range, and a tilted adsorption geometry near saturation. The optimum activity and enantioselectivity reported previously in catalytic processes for intermediate concentrations can then be associated with the orientation of the aromatic ring parallel to the surface plane. In a separate study, it was determined that hydrogen plays a unique role in cinchonidine adsorption, initially conditioning the surface for the uptake (presumably by reduction and removal of surface contaminants), and later hydrogenating the quinoline fragment of the modifier and facilitating its desorption. Finally, different solvents were shown to behave differently in these systems. Specifically, adsorbed cinchonidine remains on the platinum surface after flushing with non-polar solutions such as cyclohexane, but can be easily removed by more polar solvents such as dichloromethane. This behavior correlates well with both the solubility of cinchonidine and the performance of the cinchona/platinum catalyst as a function of the nature of the solvent.