Ring-fused Derivatives Research Articles

Phosphole <i>P</i>-Oxide-Containing π-Electron Materials: Synthesis and Applications in Fluorescence Imaging

Phosphole P-oxide is a useful building block for π-conjugated materials due to its nonaromatic and electron-accepting character. We have synthesized a series of ring-fused derivatives of phosphole P-oxide based on the intramolecular nucleophilic cyclization of appropriate alkyne precursors or radical phosphanylations. Some of the thus obtained compounds exhibited intriguing fluorescence properties and were applied to fluorescence imaging. A donor-acceptor-type benzo[b]phosphole P-oxide with a (diphenylamino)phenyl group exhibited large solvatochromism in its fluorescence spectra, and could hence be used as a staining agent for lipid droplets. C-Naphox and PB430, which consist of fully ring-fused π-conjugated ladder-type scaffolds, exhibited outstanding photostability and their absorption and emission properties were suitable for super-resolution STED imaging. Moreover, using PB430-conjugated antibodies, we carried out a 3-D reconstruction of the STED images and developed a photostability-based multicolor STED imaging technique.

A theoretical study on the electronic properties of two ring-fused derivatives of 9,10-diphenylanthracene

Two new contorted polycyclic aromatic hydrocarbons (PAHs) 1 and 2 have been synthesized by Perepichka and coworkers (Org. Lett., 2015, 17, 4224).

Identification of fused bicyclic derivatives of pyrrolidine and imidazolidinone as dengue virus-2 NS2B-NS3 protease inhibitors

A series of fused ring derivatives of pyrrolidine and imidazolidinone were designed, synthesized, characterized and assayed against the DENV-2 NS2B-NS3 protease and wild-type DENV-2 virus. The linear dipeptide compound 1 and the non-peptidic fused ring compound 2 show comparable activities against DENV-2 NS2B-NS3 protease and wild-type DENV-2 virus in a viral replication assay. The preliminary SAR reveals that a substituent and its stereochemistry at C-3 position, substitution (X) at N-2 arene and a linker (Y) between C-3 position and its attached arene are important for the fused-ring scaffold of pyrrolidino [1,2-c]imidazolidinone to block the active site of NS2B-NS3 protease. This promising structural core will facilitate the discovery of non-peptidic, potent NS2B-NS3 protease inhibitors to stop dengue virus infections.

ChemInform Abstract: Developing Steroidal Aromatase Inhibitors — An Effective Armament to Win the Battle Against Breast Cancer

AbstractReview: [184 refs.

Synthesis and Divergent Electronic Properties of Two Ring-Fused Derivatives of 9,10-Diphenylanthracene.

Two new contorted polycyclic aromatic hydrocarbons (PAHs) 1 and 2 were synthesized by acid-catalyzed benzannulation of a substituted anthracene. The isomers reveal dissimilar photophysical and redox properties with 2 having a much smaller HOMO-LUMO gap than 1. In the solid state, 2 packs in a unique two-dimensional herringbone motif that gives rise to efficient ambipolar charge transport in OFET devices, a feature not previously observed in contorted PAHs. On the other hand, 1 packs in one-dimensional dimerized π-stacks and displays insulating properties.

Fused-ring derivatives of quinoxalines: spectroscopic characterization and photoinduced processes investigated by EPR spin trapping technique.

10-Ethyl-7-oxo-7,10-dihydropyrido[2,3-f]quinoxaline derivatives, synthesized as promising biologically/photobiologically active compounds were characterized by UV/vis, FT-IR and fluorescent spectroscopy. Photoinduced processes of these derivatives were studied by EPR spectroscopy, monitoring in situ the generation of reactive intermediates upon UVA (λmax = 365 nm) irradiation. The formation of reactive oxygen species and further oxygen- and carbon-centered radical intermediates was detected and possible reaction routes were suggested. To quantify the investigated processes, the quantum yields of the superoxide radical anion spin-adduct and 4-oxo-2,2,6,6-tetramethylpiperidine N-oxyl generation were determined, reflecting the activation of molecular oxygen by the excited state of the quinoxaline derivative.

2,6-Diacylnaphthalene-1,8:4,5-Bis(dicarboximides): Synthesis, Reduction Potentials, and Core Extension

2,6-Diacyl derivatives of naphthalene-1,8:4,5-bis(dicarboximide)s have been synthesized via Stille coupling reactions of the corresponding 2,6-distannyl derivative with acyl halides. Reaction of these diketones with hydrazine gave phthalazino[6,7,8,1-lmna]pyridazino[5,4,3-gh][3,8]phenanthroline-5,11(4H,10H)-dione fused-ring derivatives. The products were characterized by UV-vis absorption spectroscopy and electrochemistry, modeled using density functional theory calculations, and, in some cases, studied and compared using single-crystal X-ray diffraction.

Effect of N-1/C-8 Ring Fusion and C-7 Ring Structure on Fluoroquinolone Lethality

Quinolones rapidly kill bacteria by two mechanisms, one that requires protein synthesis and one that does not. The latter, which is measured as lethal action in the presence of the protein synthesis inhibitor chloramphenicol, is enhanced by N-1 cyclopropyl and C-8 methoxy substituents, as seen with the highly lethal compound PD161144. In some compounds, such as levofloxacin, the N-1 and C-8 substituents are fused. To assess the effect of ring fusion on killing, structural derivatives of levofloxacin and PD161144 differing at C-7 were synthesized and examined with Escherichia coli. A fused-ring derivative of PD161144 exhibited a striking absence of lethal activity in the presence of chloramphenicol. In general, ring fusion had little effect on lethal activity when protein synthesis was allowed, but fusion reduced lethal activity in the absence of protein synthesis to extents that depended on the C-7 ring structure. Additional fused-ring fluoroquinolones, pazufloxacin, marbofloxacin, and rufloxacin, also exhibited reduced activity in the presence of chloramphenicol. Energy minimization modeling revealed that steric interactions of the trans-oriented N-1 cyclopropyl and C-8 methoxy moieties skew the quinolone core, rigidly orient these groups perpendicular to core rings, and restrict the rotational freedom of C-7 rings. These features were not observed with fused-ring derivatives. Remarkably, structural effects on quinolone lethality were not explained by the recently described X-ray crystal structures of fluoroquinolone-topoisomerase IV-DNA complexes, suggesting the existence of an additional drug-binding state.

A New Route to Ring-Fused Pyrazines: Imidazo[4,5-b]Quinoxalines by a Simple Oxidation-Annulation Sequence

Novel tricyclic 4H-imidazo[4,5-b]quinoxalines were synthesized by a new ortho-annulation process starting from 4H-imidazoles and cerammonium nitrate (CAN) as oxidation reagent in the presence of potassium carbonate as base. This reaction is interpreted as a multi-step reaction involving oxidative radical formation, a radical aromatic substitution and a subsequent redox process. The analysis is supported by high level DFT calculations. This novel transformation opens the way for the construction of ring-fused derivatives of pyrazine. The new tricyclic products display strong fluorescence in solution and, in addition, show reversible redox activity.

Copolymerization of poly(1‐naphthylamine) with aniline and o‐toluidine

AbstractThe commercial use of polyaniline has been impeded by its intractable nature and insolubility. The use of substituted polyaniline has been attempted mainly to increase the processibility of polyaniline, but this approach usually results in the lowering of the conductivity. This study reports the synthesis of poly(1‐naphthylamine), a fused ring derivative of polyaniline, and its copolymers with aniline and o‐toluidine via a chemical polymerization method. Spectral, thermal, morphological, and conductivity studies were carried out to elucidate the influence of the incorporation of aniline and o‐toluidine units into poly(1‐naphthylamine). © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008

A Theoretical Study of Some Bicyclic Azoalkanes

The molecular structures of the ground and lowest triplet states of 2,3-diazabicyclo[2.2.1]hept-2-ene (DBH), 2,3-diazabicyclo[2.2.2]oct-2-ene (DBO) and their fused ring derivatives are investigated with an ab initio method and the density functional theory. Unlike the singlet DBH and DBO, the azo skeletal structures of the triplet counterparts are turned out to be quite sensitive to the change of the electronic structure of the fused ring. The B3LYP C-N=N-C dihedral angles of the triplet DBH and DBO are estimated to be about 28.0 and , respectively. The B3LYP singlet-triplet energy gaps for DBH and DBO are predicted to be 58.4 and 48.4 kcal/mol, respectively. The triplet state energy can be lowered drastically by the presence of the remote interaction as in the case of 1bb'. 㜀歳潴ĀԀ䁱�⨀Ā
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Theoretical study of borazine and its derivatives

The density functional theory is used to study the geometries, electronic structures, and aromaticity of borazine and its fused ring derivatives. Some new evidences for the ionic nature of B–N bond are found. Geometry studies show that the B–N bond lengths are equal. The lone pair VSCCs of the N atoms are found. As shown, the B–N bonds are of ionic nature based on their positive Laplacian. Magnatic shielding constants also are computed. The shielding and deshielding contributions are divided into Lewis and non-Lewis parts by the NCS-NBO method. It is demonstrated in the NICS studies that there are the ring current effects on borazine and its derivatives are very weak. The aromaticity of borazine is weakened with the fused ring number increasing.

Bicyclic nucleoside analogues from d-glucose: synthesis of chiral as well as racemic 1,4-dioxepane ring-fused derivatives

The dioxepanofuranose derivatives 4 and 12, obtained through the cyclization of the 3-(2-hydroxyethyl) ether of a d- xylo-pentodialdose derivative, were appropriately functionalized and elaborated to the first examples of the new class of 3′- O and 5′- O-bicyclic nucleoside analogues 9, 10, and 14 with a fused seven-membered ring. Reactions carried out through the intermediacy of the d- xylo-pentodialdose derivative 5 yielded racemic products, while prior protection of the 4-formyl group (as in 7) before deprotection of the 1,2-hydroxyl groups led to optically active analogues.

Photochemistry of anthrylethene derivatives containing heteroaromatic ring: Thiophene, furan, and their fused ring derivatives

Four 1-(9-anthryl)-2-heteroarylethene derivatives containing sulfur or oxygen atom such as 1-(9-anthryl)-2-(2-thiophenyl)ethene (ATE), 1-(9-anthryl)-2-(2-benzo[ b]thiophenyl)ethene (ABTE), 1-(9-anthryl)-2-(2-furanyl)ethene (AFE), and 1-(9-anthryl)-2-(2-benzofuranyl)ethene (ABFE) have been prepared and their excited state properties have been investigated in cyclohexane, acetonitrile, and methanol. These sulfur- or oxygen-heteroaromatic ring derivatives show solvent-dependent fluorescence and photoisomerization behavior, due to the intramolecular charge-transfer character of the lowest S 1 state. Substituent effect on fluorescence and photoisomerization of ATE further supports the contribution of the intramolecular charge-transfer character to the lowest S 1 state, which is more increased by the introduction of electron-withdrawing substituent into anthracene ring.

Recent Progress in Pyridazin-3(2H)-Ones Chemistry

Although Fischer obtained the first pyridazines as early as 1886, major attention has been devoted to their chemistry only in the early few decades. However, pyridazin-3(2H)-ones and their fused ring derivatives have recently received much more attention to possess various biological activities and also to use new synthetic auxiliaries. The scope of the present review is to summarize from 1990 as the followings; the construction of pyridazin-3(2H)-one ring, the reaction of ring nitrogen (N2), the reaction of ring carbons at C3, C4, C5 and C6 and the application of pyridazin-3(2H)-one derivatives in the synthetic chemistry.

Synthesis, structural evaluation, and estrogen receptor interaction of 2,3-diarylpiperazines.

To develop novel estrogen receptor (ER) ligands, ring-fused derivatives of the hormonally active (1R,2S)/(1S,2R)-1-(2-chloro-4-hydroxyphenyl)-2-(2,6-dichloro-4-hydroxyphenyl)ethylenediamine 4b were synthesized. (2R,3S)/(2S,3R)-2-(2-Chloro-4-hydroxyphenyl)-3-(2,6-dichloro-4-hydroxyphenyl)piperazine 4 induced ligand-dependent gene expression in MCF-7-2a cells, stably transfected with the plasmid ERE(wtc)luc and was therefore used as a lead structure. The influence of the substitution pattern in the aromatic rings (4-OH (1), 2-F,4-OH (2), 2-Cl,4-OH (3), 2,6-Cl2,3-OH (5), and 2,6-Cl2,4-OH (6)) and the effect of N-ethyl chains on the ER binding and activation of gene expression were studied. The synthesis started from the respective methoxy-substituted (1R,2S)/(1S,2R)-configurated 1,2-diarylethylenediamines 6b to 4b, which were reacted with dimethyl oxalate in order to get 5,6-diarylpiperazine-2,3-diones. Reduction with BH3*tetrahydrofuran and ether cleavage with BBr3 yielded the piperazines 1-6. The N-alkylation of the piperazines 1a-3a, which was employed for obtaining compounds 7-11, was succeeded by acetic anhydride followed by reduction and ether cleavage. Nuclear magnetic resonance (NMR) spectroscopical studies revealed a synclinal conformation of the 1,2-diarylethane pharmacophore and a preference of the substituents at the heterocyclic ring for an equatorial position. This spatial structure prevents an interaction with the ER analogously to that of estradiol (E2). Therefore, the piperazines can displace E2 from its binding site only to a very small extent. Only the N-ethyl (8) and N,N'-diethyl (11) derivatives of piperazine 3 showed relative binding affinity values > 0.1% (8, 0.42%, and 11, 0.17%). Nevertheless, ER-mediated gene activation was verified for the piperazines 4 (20%), 6 (73%), 7 (34%), 8 (74%), and 11 (37%) (concentration, 1 microM; E2, 100% activation) on the MCF-7-2a cell line. O-methylation led to completely inactive compounds and showed the necessity of H bridges from the piperazines to the ER for activating gene expression.

A novel acylative ring cleavage of benzothieno[3,2-b]pyran-4-ols: application to the synthesis of dibenzothiophenes and fused-ring derivatives

The benzothienopyranols 3, readily available from the ketone 1, are transformed to the carbamates 5 on treatment with N,N-dimethylcarbamoyl chloride, subsequent thermal electrocyclisation provides access to dibenzothiophene derivatives 6 and 11–13.

ChemInform Abstract: Regioselective Substitution in Aromatic Six‐Membered Nitrogen Heterocycles

Publisher Summary The reactivity of various six-membered heteroaromatic compounds has been previously reviewed through 1982. This chapter describes the nucleophilic, electrophilic, and free-radical substitution reactions on the ring carbon atoms of pyridines, pyridazines, pyrimidines, pyrazines, triazines, and tetrazines. Fused-ring derivatives of these heterocycles are not covered. Multistep substitutions involving dihydro intermediates are included. The primary chemical literature between 1982 and June 1987 is also surveyed.

Fluorometric Determination of Thiazole-Containing Compounds

Fluorescence spectroscopy was applied to the development of sensitive analytical methods for the determination of thiazole and several congeners that contain substituted thiazole rings. Treatment to yield thionine, previously used spectrophotometrically to measure thiazole and fluorometrically only for sulfur determinations in inorganic systems, is further characterized and illustrated with the determination of the antibiotic thiopeptin. This method is selective for submicrogram quantities of thiazole rings in the presence of fused-ring derivatives and reduced analogs. It has a precision of ±2% RSD (n = 11) at the 15-ng/ml thiazole concentration level with a signal-to-noise ratio of 3:1. For thiopeptin, this method has an accuracy of 5% mean relative error (n = 8) over the 5–20-ppm range in medicated feed.

Fused ring derivatives of [12]paracyclophane

Fused ring derivatives of [12]paracyclophane