Bicyclic Arenes Research Articles

Experimental study of neuropsychotropic activity

Objective. To study the neuropsychotropic activity of 2,4-dioxobutanoic acid derivatives containing a fragment of benzimidazole as well as to determine the relationship between the structure of substances and their biological effects. Materials and methods. The spectrum of neuropsychotropic activity of 2,4-dioxobutanoic acid derivatives with benzimidazole was studied on experimental animals using the open field, black-and-white camera, and extrapolation deliverance tests. Results. A compound with potential anxiolytic properties has been identified. The dependence of the manifestation of anxiogenic or anxiolytic properties in the presence of mono- or bicyclic arenes in the structure, respectively, is shown. Conclusions. 2,4-Dioxobutane acids containing a fragment of benzimidazole are of interest for the search for substances with neuropsychotropic activity. The results of the structure-activity analysis should be used in further targeted synthesis.

Mechanochemically Induced Chalcogenation of Bicyclic Arenes under Solvent‐, Ligand‐, Metal‐, and Oxidant‐Free Conditions

AbstractA convenient method has been developed for the synthesis of biarenyl chalcogenides through the interaction of bicyclic arenes and diaryl dichalcogenides on the surface of basic alumina under ball milling without any metal catalyst or solvent. This methodology shows wide substrate scope and is of high potential in organic synthesis due to its green aspects of ease of operation, shorter reaction time, ambient conditions and high yields.

Chain-Growth Polymerization of Benzotriazole Using Suzuki-Miyaura Cross-Coupling and Dialkylbiarylphosphine Palladium Catalysts.

Electron-deficient (n-type) conjugated materials are commonly prepared via step-growth methods with limited control over the molecular weight and molecular weight distribution of the resulting polymers. In this communication, we demonstrate that Pd-dialkylbiarylphosphine catalysts enable the chain-growth polymerization of benzo[1,2,3]triazole using Suzuki-Miyaura coupling with molecular weight control and modest molecular weight distributions (Đ ∼ 1.2-1.6). The importance of a free ligand in the reaction mixture during polymerization was established by analysis of polymer samples using GPC and MALDI-TOF mass spectrometry. A block copolymer with poly(3-hexylthiophene) was also synthesized by sequential monomer addition. The success of these commercially available catalysts for polymerization of benzotriazole highlights their potential for chain-growth reactions with other bicyclic arenes in the future.

Transition Metal- and Oxidant-Free Base-Mediated Selenation of Bicyclic Arenes at Room Temperature.

Bicyclic arenyl selenides are of much importance because of their pharmaceutical applications. A simple method for their synthesis has been developed by a reaction of 2-naphthol and styrenyl selenocyanate/diaryl diselenide in the presence of a base at room temperature. The selenation occurs exclusively at the 1-position of 2-naphthol unit. The reactions are relatively fast (2–4 h) and high yielding. A library of substituted naphthyl styrenyl and naphthyl aryl selenides are obtained by this procedure.

Solvent‐ and Metal‐Free Chalcogenation of Bicyclic Arenes Using I2/DMSO as Non‐Metallic Catalytic System

We have developed a green and efficient protocol for the chalcogenation of bicyclic arenes by using I2/DMSO as catalytic system under solvent‐ and metal‐free conditions. This protocol allows access to several chalcogenated bicyclic arenes through C(sp2)–H bond functionalization, in good to excellent yields by using microwave irradiation or conventional heating.

Express method for total content assessment of aromatic hydrocarbons and oxygen in finished gasolines by refractometry and densimetry

This paper presents routine refracto-densimetric indicators which may be used to identify unbalanced automobile gasoline and falsifications (surrogates). These criteria are supposed to reduce considerably the amount of testing via standard chromatographic and spectroscopic methods. Refracto-densimetric method for controlling the limiting weight content of oxygen is based on substantial difference between specific refractions of oxygenates and hydrocarbon gasoline components. Application of the refractive intercept which is additive in the volume fractions of components and constant for different homologous series of hydrocarbons allowed to establish its maximum value, the excess of which identifies a gasoline with a high content of aromatic hydrocarbons. In addition, the excess of refractive intercept of certain limit value can also indicate the possible presence of conjugated diolefins in gasoline and bicyclic arenes.

Atmospheric PM and volatile organic compounds released from Mediterranean shrubland wildfires

Wildfires produce a significant release of gases and particles affecting climate and air quality. In the Mediterranean region, shrublands significantly contribute to burned areas and may show specific emission profiles. Our objective was to depict and quantify the primary-derived aerosols and precursors of secondary particulate species released during shrubland experimental fires, in which fire-line intensity values were equivalent to those of moderate shrubland wildfires, by using a number of different methodologies for the characterization of organic and inorganic compounds in both gas-phase and particulate-phase. Emissions of PM mass, particle number concentrations and organic and inorganic PMx components during flaming and smouldering phases were characterized in a field shrubland fire experiment. Our results revealed a clear prevalence of K+ and SO42− as inorganic ions released during the flaming–smouldering processes, accounting for 68–80% of the inorganic soluble fraction. During the residual-smouldering phases, in addition to K+ and SO42−, Ca2+ was found in significant amounts probably due the predominance of re-suspension processes (ashes and soil dust) over other emission sources during this stage. Concerning organic markers, the chromatograms were dominated by phenols, n-alkanals and n-alkanones, as well as by alcohol biomarkers in all the PMx fractions investigated. Levoglucosan was the most abundant degradation compound with maximum emission factors between 182 and 261 mg kg−1 in PM2.5 and PM10 respectively. However, levoglucosan was also observed in significant amounts in the gas-phase. The most representative organic volatile constituents in the smoke samples were alcohols, carbonyls, acids, monocyclic and bicyclic arenes, isoprenoids and alkanes compounds. The emission factors obtained in this study may contribute to the validation and improvement of national and international emission inventories of this intricate and diffuse emission source.

A Combined NMR, Computational, and HPLC Study of the Inclusion of Aromatic and Fluoroaromatic Compounds in Cyclodextrins as a Model for Studying Carbohydrate–Aromatic Interactions

AbstractA combined NMR, computational, and HPLC study of the inclusion of aromatic and fluoroaromatic compounds in cyclodextrins has been carried out with the aim of studying this process as a model for carbohydrate···aromatic interactions. NMR experiments showed that although β‐CD formed an inclusion complex with benzene, no stable inclusion adduct was formed with hexafluorobenzene. MM3* calculations confirmed these data and, when extended to naphthalene, anthracene, phenanthrene, and their partially and fully fluorinated analogues, showed that β‐CD formed inclusion adducts only with the hydrocarbons, whereas the partially fluorinated derivatives were shown to enter the cavity only with their non‐fluorinated part, and the perfluoro compounds were not included. HPLC experiments, carried out by eluting these compounds through CD‐modified HPLC columns, also confirmed these results, at least with the mono‐ and bicyclic arenes. Indeed, the elution of these derivatives showed that the efficiency of the inclusion, as determined by comparing HPLC retention times, decreased on passing from hydrocarbons to partially fluorinated compounds, and reached a minimum with perfluorinated derivatives. In contrast with this general trend, 1,2,3,4‐tetrafluoroanthracene had longer retentions times on β‐ and γ‐CD‐modified HPLC columns than anthracene, possibly for solubility reasons. As a whole, these results were interpreted in terms of carbohydrate···aromatic interactions between the C5–H5 bonds on the hydrophobic faces of the sugars and the π electrons of the aromatic partner. The interactions seem to have an important dispersive component.(© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2008)

Oxidation of bicyclic arenes with hydrogen peroxide catalysed by Mn(III) porphyrins

Several manganese(III) porphyrin complexes were evaluated as catalysts in the oxidation of indane and tetralin with hydrogen peroxide, in the presence of ammonium acetate as a co-catalyst. Catalysis by Mn(III) meso-tetra-2,6-dichlorophenylporphyrins gave rise, in a first stage, to benzylic monooxygenation products (1-alcohols and 1-ketones). However, addition of excess of oxidant gave rise to over-oxidation products and, in certain conditions, hydroxy-keto compounds were selectively obtained. Reactions catalysed by Mn(III) meso-tetra-pentafluorophenylporphyrins showed higher capability to generate dehydrogenated products. As a result, 1 H-indene and naphthalene were formed. To understand the reactions’ pathway, the oxidations of 1-indanol, 1-indanone, 2-indanol, 1 H-indene, 1-tetralol, 1-tetralone, 1,4-dihydroxytetralin and 4-hydroxy-1-tetralone were also considered with manganese (III) meso-tetra-2,6-dichlorophenylporphyrin chloride, Mn(TDCPP)Cl, as catalyst.

Tunable haptotropic metal migration in fused arenes: towards organometallic switches.

Tricarbonyl chromium complexes of naphthalene derivatives are synthesized by chromium-templated [3 + 2 + 1]-benzannulation and subjected to thermally induced haptotropic rearrangement experiments. Thermodynamic and kinetic parameters for the metal shift demonstrate the influence of the arene substitution pattern. In turn, the chromium template may be tuned as well by phosphorus coligands which allow to accelerate or slow down the isomerization process; this effect quantitatively reflects the steric and electronic properties of the coligand sphere. Proper adjustment of the template allows for a photo-induced reverse migration of the chromium moiety which results in a switchable organometallic device. Experiments with enantiopure arene chromium complexes indicate a stereospecific metal migration. The rearrangement proceeds by an intramolecular mechanism in both directions. Haptotropic isomerization reactions are not limited to bicyclic arenes and can be extended from naphthalenes to phenanthrene or tetra- and pentacyclic heteroarene systems.

Studies on cognitive enhancing agents. III. Antiamnestic and antihypoxic activities of a series of 1-bicycloaryl-2-(omega-aminoalkoxy)ethanols.

2-(2-Aminoethoxy)-1-hydroxyethyl derivatives of bicyclic arenes (naphthalene, thianaphthene, benzofuran, and indole) were prepared and screened for antiamnestic (AA) and antihypoxic (AH) activities which were evaluated by measuring the reversing potency in electroconvulsion-induced amnesia and the protective effect against hypoxia, respectively, in mice. Compound 3o, 1-(benzo[b]thiophen-5-yl)-2- (2-diethylaminoethoxy)ethanol, showed the best AA and AH activity profile, being superior to our prototype compound, 2-(2-dimethylaminoethoxy)-1-phenylethanol (1). Elongation of the ethylene linkage in the side chain of 3o to 3- and 4-carbon moieties brought about a significant decrease in AH activity. Compound 3o was further investigated for its protective effect against CO2-induced memory impairment and for acute toxicity in mice. It is ten-fold more potent than tacrine in the amnesia-reversal assay and is considerably less toxic than tacrine.

Activation of aromatic rings by early transition metal ions in the gas phase. Implications for the metal‐catalyzed [2 + 2 + 2] cycloaddition of alkynes and nitriles

AbstractThe reactions of a series of monocyclic and bicyclic arenes with early transition metal ions (Sc+, Y+, Nb+ and Ta+) and their oxides and dioxides were studied in a Fourier transform ion cyclotron resonance mass spectrometer. Ring cleavage of the nitrogen‐containing heterocycles results in loss of HCN as the dominant pathway. Thermochemical considerations, secondary reactions and correlations with solution cyclotrimerization reactions indicate that the MC4H4+ product is a metallacyclopentadiene. Based on correspondence between the reactivities of a series of early metals with their valence electron counts, the reactivities of quinoline and isoquinoline and the decomposition behavior of the products, a metallacycloheptatriene intermediate is proposed for the heteroaromatic ring cleavage reaction. These results are compared to metal complexes in solution which catalyze the [2 + 2 + 2] cyclotrimerization of alkynes and nitriles.

π‐Amphoteric Heterocycles

The formation of the Wheland or Meisenheimer cr-complexes the wellknown phenomena in chemistry of aromatics and heteroaromatics [1, 2] is a key step in the both classical SE2Ar and SN2Ar substitution. The ability of arenes and hetarenes to form predominantly the cationic or the anionic type of s-complexes is, in general, determined by the p-excessive or p-deficient character of aromatic nucleus (cf. known C-protonation of azulenes, indoles, donor-substituted benzenes or vice versa addition of nucleophiles to nitroazines and polynitroarenes). To our knowledge the simple aromatics, capable of undergoing easy transformation in the both directions into the anionic, as well as the cationic s-complexes are still unknown. The simplest possible aromatics of this type would be expected to contain two condensed rings together with a high asymmetry of the p-electron density. With the indolizines la,b, we found the first example of the bicyclic arenes, which easily form cationic and anionic s-complexes on carbon atoms with a simple variation in the pH of the solvent system.