Benzonorcorrole NiII Complexes: Enhancement of Paratropic Ring Current and Singlet Diradical Character by Benzo‐Fusion

Fused benzene rings to antiaromatic compounds generally improve their stability but attenuate their antiaromaticity. The opposite case is now reported. Ni^II benzonorcorroles were synthesized and the effect of benzo‐fusion on the antiaromaticity was elucidated. The benzo‐fusion resulted in significant decrease of the HOMO–LUMO gaps and enhancement of the paratropic ring current effect. Furthermore, the introduction of the benzo groups induced singlet diradical character in the antiaromatic porphyrinoid.     

Syntheses of 4-(benzo[b]furan-2 or 3-yl)- and 4-(benzo[b]-thiophen-3-yl)piperidines with 5-HT2 antagonist activity

The syntheses of 4-(benzo[b]furan-3-yl)piperidines, 4-(benzo[b]furan-2-yl)piperidines and 4-(benzo[b]thiophen-3-yl)piperidines with 5-HT₂ antagonist activity are described. Reaction of 1-acetyl-4-(2,4-difluorobenzo-yl)piperidine 2 with methyl glycolate gave methyl 6-fluoro-3-(1-acetylpiperidin-4-yl)benzo[b]furan-2-carboxylate 3 , which was converted to 2-[2-[4-(benzo[b]furan-3-yi)piperidin-1-yl]ethyl-5,6,7,8-tetrahydro-1,2,4-triazolo-[4,3-a]pyridin-3(2H)-one hydrochloride 9 . Analogous benzo[b]furans 17a-d and benzo[b]thiophenes 10a,b and 18a were prepared by a similar method. Cyclization of 4-fluoro-2-(4-pyridinylmethoxy)acetophenones 20a,b afforded 4-(benzo[b]furan-2-yl)pyridines 21a,b , which were converted to 2-[2-[4-(benzo[b]furan-2-yl)-piperidin-1-yl]ethyl-5,6,7,8-tetrahydro-1,2,4-triazolo[4,3-a]pyridin-3(2H)-one hydrochlorides 24a,b. Among them, benzo[b]furans 9 and 17a,d and benzo[b]thiophenes 10 and 18a showed potent 5-HT₂ antagonist activity in vitro.     

Synthesis and Cation Recognition Study of Novel Benzo Crown Ether Functionalized Enamine Derivatives

A novel series of benzo crown ether (dibenzo 18-crown-6 ether, benzo 18-crown-6 ether, and benzo 15-crown-5 ether) functionalized enamines derivatives from amino benzo crown ether (4-amino dibenzo 18-crown-6 ether, 4-amino benzo 18-crown-6 ether, 4-amino benzo 15-crown-5 ether) and substituted 3-(dimethylamino)-1-phenylprop-2-en-1-one compounds have been synthesized. All the synthesized compounds were characterized by infrared, ¹H NMR, ¹³C NMR, distortionless enhancement polarization transfer, and mass and elemental analysis techniques. The cation recognition property for benzo crown ether enamine 8a was studied by absorption and fluorescence spectroscopy.     

Spectrometry: Spectrofluorimetric Study of Benzo[a]Quinolizidines as Potential Fluorescent Probes for DNA

Abstract

The interaction between DNA and several benzo[a]quinolizidines, including emetine and four synthetic benzo[a]quinolizidine derivatives, has been studied using spectrophotometric and spectrofluorimetric techniques. An appreciable decrease in molar absorptivity at the maxima at λ = 230 nm and λ = 280 nm is observed when increasing DNA concentrations (10 mg/ml-100 mg/ml) are added to aqueous buffered solutions (pH = 7) of the benzo[a]quinolizidine derivatives. These compounds exhibit native fluorescence at 315 nm (λex = 285 nm), which is quenched by increasing amounts of DNA. The interaction between DNA and benzo[a]quinolizidines was confirmed by viscosimetry. Increases between 1.9% and 10.8% in the reduced specific viscosity (n/no) of DNA solutions were observed due to the presence of the benzo[a]quinolizidines studied.     

A concise synthesis of all four possible benzo[4,5]furopyridines via palladium-mediated reactions

[reaction: see text] By taking advantage of the alpha- and gamma-activation of chloropyridines as well as palladium-mediated reactions, all four possible benzo[4,5]furopyridine tricyclic heterocycles, benzo[4,5]furo[2,3-b]pyridine, benzo[4,5]furo[2,3-c]pyridine, benzo[4,5]furo[3,2-c]pyridine, and benzo[4,5]furo[3,2-b]pyridine, are efficiently synthesized from 2-chloro-3-iodopyridine, 3-chloro-4-stannylpyridine, 4-chloro-3-iodopyridine, and 2-chloro-3-hydroxypyridine, respectively.     

Preparation of 2-, 3-, 4- and 7-(2-alkylcarbamoyl-1-alkylvinyl)benzo[b]furans and their BLT1 and/or BLT2 inhibitory activities

Several 2-alkylcarbamoyl-1-alkylvinylbenzo[b]furans were designed to find a selective leukotriene B4 (LTB4) receptor antagonist. 2-(2-Alkylcarbamoyl-1-alkylvinyl)benzo[b]furans having a substituent group at the 3-position, 4-(2-alkylcarbamoyl-1-methylvinyl)benzo[b]furans having a substituent group at the 3-position, and 7-(2-alkylcarbamoyl-1-methylvinyl)benzo[b]furans and 3-(2-alkylcarbamoyl-1-alkylvinyl)benzo[b]furans were prepared and evaluated for LTB4 receptor (BLT1 and BLT2) inhibitory activities. (E)-3-Amino-4-[2-[2-(3,4-dimethoxyphenyl)ethylcarbamoyl]-1-methylvinyl]benzo[b]furan ((E)-17c) showed potent and selective inhibitory activity for BLT2. On the other hand, (E)-7-(2-diethylcarbamoyl-1-methylvinyl)benzo[b]furan ((E)-27a) showed potent inhibitory activity for both BLT1 and BLT2.     

Site-specific preparation of 4-substituted-6-fluoro(carboalkoxyl)benzo[b]furans and benzo[b]thiophenes via base-catalyzed cyclization of enyne derivatives

A site-specific synthesis of 4-substituted-6-fluoro(carboalkoxyl)benzo[b]furans and benzo[b]thiophenes is described. The reactions of heterocyclic aromatic aldehydes with a Wittig reagent, followed by Sonogashira reaction with terminal alkynes, and subsequent base-catalyzed cyclization site-specifically provide 4-substituted-6-fluoro(carboalkoxyl)benzo[b]furans and benzo[b]thiophenes in good yields.     

Cation complexing of crown ethers using fluorescence spectroscopy, part II

The complex formations of benzo[12]crown-4, benzo[15]crown-5 and benzo[18]crown-6 with perchlorate salts of Mg(2+), Li(+) and Na(+) were investigated using the steady state fluorescence emission spectroscopy in acetonitrile. The complexation enhanced quenched fluorescence spectra, (CEQFS) exhibited the ion complexation role of the macrocyclic ethers and equilibrium constant, K(e) of 1:1 stoichiometry were estimated. The K(e) were found in the order of Mg(+)>Na(+)>Li(+) for benzo[15]crown-5 whilst Na(+)>Mg(+)>Li(+) order was found with benzo[12]crown-4 at 298 K.     

Synthesis of benzo[b]furan-2-thioles from 4-(2-hydroxyaryl)-1,2,3-thiadiazoles

4-(2-Hydroxyaryl)-1,2,3-thiadiazoles treated with bases decompose with nitrogen liberation and the formation of benzo[b]furan-2-thiolates. On acidifying the thiolates benzo[b]furan-2-thiols were obtained. 4-(4- and -5-Benzyloxy-2-hydroxyphenyl)-1,2,3-thiadiazoles formed analogously the corresponding benzo[b]furan-2-thiolates whose acidifying afforded polymeric compounds.     

Synthesis of 2-, 4- and 5-(2-alkylcarbamoyl-1-methylvinyl)-7-alkyloxybenzo[b]furans and their leukotriene B4 receptor antagonistic activity

Variable benzo[b]furan derivatives having (E)- and (Z)-2-alkylcarbamoyl-1-methylvinyl groups at the 2-, 4- and 5-positions and a carboxylpropoxy or (1-phenyl)ethoxy group at the 7-position were prepared to find novel and selective leukotriene B4(LTB4) receptor antagonists. (E)-2-(2-diethylcarbamoyl-1-methylvinyl)-7-(1-phenylethoxy)benzo[b]furan (4v) showed selective inhibition to the human BLT2 receptor (hBLT2). On the other hand, (E)-2-acetyl-4-(2-diethylcarbamoyl-1-methylvinyl)-7-(1-phenylethoxy)benzo[b]furan (7v) inhibited both human BLT(1) receptor (hBLT1) and hBLT2. The (E)-2-(2-diethylcarbamoyl-1-methylvinyl) group lay on approximately the same plane as the benzo[b]furan ring, whereas the (E)-4-(2-diethylcarbamoyl-1-methylvinyl) group had the torsion angle (45.7 degree) from the benzo[b]furan ring plane. However, the (Z)-(2-alkylcarbamoyl-1-methylvinyl)benzo[b]furans were inactive. The inhibitory activity depended on the conformation of the 2-diethylcarbamoyl-1-methylvinyl group.     

Synthesis and Characterization of New Heterocyclic Compounds Containing Thienylbenzo[h]Quinoline Moiety

In this paper the reaction of 2‐(2′‐thienylmethylene)‐3,4‐dihydronaphthalen‐2(1H)‐one ( 1 ) with cyanothioacetamide gave a mixture of 3‐cyano‐5,6‐dihydro‐4‐(2′‐thienyl)‐benzo[h]quinolin‐2(1H)‐thione ( 2 ) and the related disulfide 3 . Compound 2 was reacted with some halo compounds namely; ethyl chloroacetate, chloroacetamide, chloro(N‐(p‐chlorophenyl))acetamide, N¹‐chloroacetylsulfanilamide, and 2‐chloromethyl‐1H‐benzimidazole to produce a series of 2‐(substituted)methylthio‐3‐cyano‐5,6‐dihydro‐4‐(2′‐thienyl)benzo[h]quinolines 4a , 4b , 4c , 4d , 4e and 11 . Upon heating the latter compounds with sodium ethoxide, they underwent intramolecular Thorpe–Zeigler cyclization to furnish the corresponding 2‐(substituted)‐3‐amino‐5,6‐dihydro‐4‐(2′‐thienyl)‐benzo[h]thieno[2,3‐b]quinolines 5a , 5b , 5c , 5d , 5e and 12 . (3‐Cyano‐5,6‐dihydro‐4‐(2′‐thienyl)‐benzo[h]quinolin‐2‐ylthio)acethydrazide ( 8 ) and the related isomer, 3‐amino‐5,6‐dihydro‐4‐(2′‐thienyl)thieno[2,3‐b]benzo[h]quinoline‐2‐carbohydrazide ( 9 ), were also synthesized. Most of the aforementioned compounds were used as key intermediates for synthesizing other benzo[h]quinolines, benzo[h]thieno[2,3‐b]quinolines as well as benzo[h]pyrimido[4′,5′:4,5] thieno[2,3‐b]quinolines. The structure of all synthesized compounds was confirmed by spectroscopic measurements and analytical analyses.     

Spectres photoélectroniques He(I) et He(II) du benzo[b]sélénophène et du benzo[b]tellurophène

He(I) and He(II) photoelectron spectra of benzo[b]selenophene and benzo[b]tellurophene The photoelectron spectra of benzo[b]selenophene ( 2 ) and benzo[b]tellurophene ( 1 ) have been recorded with He(I) and He(II) radiation and been compared to those of benzo[b]thiophene ( 3 ), benzo[b]furan ( 4 ), indole ( 5 ) and indene ( 6 ). The first four bands are correlated with π-orbitals, of which the highest occupied one is strongly localized on the heteroatom in the case of 1 . The results are in agreement with semi-empirical PPP-calculations.     

Condensation of ethyl cydopentanone-2-carboxylate withN-arylmethylene-2-naphthylamines

The condensation of ethyl cyclopentanone-2-carboxylate withN-arylmethylene-2-naphthylamines depending on the conditions of reaction affords 4-aryl-l-ethoxycarbonyl-lH-2,3,4,5-tetrahydrocyclopenta-[c]benzo[f]quinolines, 4-aryl-l-ethoxycarbonyl-lH-2,3-dihydrocyclopenta[c]benzo[f]quinolines, and 4-aryllH-2,3-dihydrocyclopenta[c]benzo[f]quinolines.     

Diversity‐oriented One‐pot Synthesis of Novel Imidazo[4′,5′:4,5]benzo[e][1,4]thiazepinones and Benzo[d]imidazolyl Thiazolidinones through pTSA Promoted Cyclization and Evaluation of Antimicrobial and Anti‐inflammatory Activities

In contrast to target‐oriented synthesis that aims to access precise regions of chemistry, diversity‐oriented synthesis via multicomponent synthesis populates chemical space broadly with small molecules having diverse structures. This study has achieved the diversity‐oriented synthesis of novel imidazo[4′,5′:4,5]benzo[e][1,4]thiazepinones ( 4 ) and benzo[d]imidazolyl thiazolidinones ( 5 ) controlled by the nature of substitution effect of the reaction component. The one‐pot reaction of benzimidazole 1 , aromatic aldehyde 2 , and mercaptoacetic acid 3 leads to the formation of imidazo[4′,5′:4,5]benzo[e][1,4]thiazepinones ( 4 ) with electron‐donating groups as substitution on aromatic aldehyde while electron‐withdrawing substitutions produced benzo[d]imidazolyl thiazolidinones ( 5 ). The title compounds ( 4 ) and ( 5 ) were evaluated for their antimicrobial and anti‐inflammatory activities.     

Ipso substitution as a route to benzo[c]quinolizines and 4-hydroxycoumarins

A convenient ipso substitution method for the preparation of benzo[c]quinolizine (2) and 4-hydroxy-3-(2'-pyridyl)coumarin (3) has been developed. The intramolecular nucleophilic substitution reaction of 3-oxo-2-(2'-pyridyl)-(2-halophenyl)propanoate (1) in refluxing xylenes gives initially benzo[c]quinolizine, while further heating results in the formation of 4-hydroxycoumarin. A mechanism has been proposed to rationalize the two competitive reaction pathways, and the role of HCl is discussed. Under optimized conditions, seven benzo[c]quinolizines and five coumarins were prepared in moderate to good yields.     

Reactivity of 4‐chlorobenzo[c][2,7]naphthyridines towards Pd(0) catalyzed coupling reactions and nucleophilic substitutions. aroylation by nucleophilic substitution with analogues of acyl anions

Various 4‐substituted benzo[c][2,7]naphthyridines were prepared from the corresponding 4‐chloro derivative by Pd(0) coupling reaction or nucleophilic substitution. More particularly, 4‐aroyl‐benzo[e][2,7]naph‐thyridines were synthesized by aroylation with arenecarbaldehydes in the presence of 1,3‐dimethylimida‐zolium iodide.     

Comparative study on the structural, optical, and electrochemical properties of bithiophene-fused benzo[c]phospholes

Three types of bithiophene-fused benzo[c]phospholes were successfully prepared by Ti(II)-mediated cyclization of the corresponding dialkynylated bithiophene derivatives as a key step. Each sigma(3)-phosphorus center of the benzo[c]phosphole subunits was readily transformed into sigma(4)-phosphorus center by Au coordination or oxygenation. In addition, the bithiophene subunit was functionalized at the alpha,alpha'-carbon atoms by Pd-catalyzed cross-coupling reactions with heteroarylmetals and by an S(N)Ar reaction with hexafluorobenzene. The experimentally observed results (NMR spectroscopy, X-ray analysis, UV/Vis absorption/fluorescence spectroscopy, and cyclic/differential-pulse voltammetry) have revealed that the structural, optical, and electrochemical properties of the bithiophene-fused benzo[c]phospholes vary considerably depending on the pi-conjugation modes at the bithiophene subunits and the substituents of the heterocyclopentadiene components. The appropriately ring-annulated sigma(3)-P derivatives and sigma(4)-P-AuCl complexes were found to emit fluorescence in the orange-red region, and the sigma(4)-P-oxo derivatives proved to undergo reversible one-electron reduction at -1.4 to -1.8 V (vs ferrocene/ferrocenium). These results indicate that the bithiophene-fused benzo[c]phospholes possess narrow HOMO-LUMO gaps and low-lying LUMOs, which was confirmed by density functional theory calculations of their model compounds. The time-of-flight measurement of an ITO/benzo[c]phosphole/Al device showed that the electron mobility in the P-oxo derivative is one-order higher than that in Alq(3) at low electric fields. The present study demonstrates that the arene-fused benzo[c]phosphole skeleton could be a highly promising platform for the construction of a new class of phosphole-based optoelectrochemical materials.     

Error propagation as a factor in selection of measurement intervals for the determination of polycyclic aromatic hydrocarbons by second-derivative spectrofluorimetry

The most suitable wavelength intervals were selected for the determination of 4 polycyclic aromatic hydrocarbons (PAHs; benzo[g,h,i]perylene, dibenzo[a,h]anthracene, pyrene, and triphenylene) in very complex mixtures of 11 PAHs: anthracene, benz[a]anthracene, benzo[a]pyrene, benzo[b]fluoranthene, benzo[g,h,i]perylene, benzo[k]fluoranthene, chrysene, dibenz[a,h]anthracene, phenanthrene, pyrene, and triphenylene. The multiple linear regression algorithm was applied to measurements made in several wavelength intervals previously selected on the basis of sensitivity and minimum number of interfering compounds. Of the different models obtained, those displaying minimum error propagation in the analytical result were selected. By applying the models proposed in this study, we precisely and accurately determined benzo[g,h,i]perylene, dibenz[a,h]anthracene, pyrene, and triphenylene in complex mixtures--a feat that could not be achieved by the use of constant-wavelength spectrofluorimetry in combination with second-derivative techniques.     

Second-derivative constant-wavelength synchronous scan spectrofluorimetry for determination of benzo[b]fluoranthene, benzo[a]pyrene and indeno[1,2,3-cd]pyrene in drinking water

The use of derivative constant-wavelength synchronous scan fluorimetry is reported for the determination of three polycyclic aromatic hydrocarbon pollutants in drinking water (linearity range 0.4-4 mug 1(-1)). The limits of detection (LD) and quantification (LQ) (mug 1(-1)) are 0.01 and 0.07 for benzo[b]fluoranthene, 0.03 and 0.12 for benzo[a]pyrene and 0.19 and 0.57 for indeno[1,2,3-cd]pyrene in the presence of three other pollutants, benzo[k]fluoranthene, benzo[ghi]perylene and fluoranthene. The precision (RSD /= 85%) were satisfactory.     

Ring transformations of heterocyclic compounds. XX Benzo‐fused spiro[cyclohexadiene‐dihydroindoles] by ring transformation of pyrylium salts with anhydrobases of benzo[e]‐ and benzo[g]indolium salts

The diastereoselective synthesis of 6‐aroyl‐3,5‐diarylspiro[cyclohexa‐2,4‐diene‐1,2′2′,3′‐dihydro‐1′H‐benzo[e]indoles] 6 and ‐benzo[g]indoles] 7 from 2,4,6‐triarylpyrylium perchlorates 1 and in situ generated 2‐methylene‐2,3‐dihydro‐1H‐benzo[e]indoles 3 or ‐benzo[g]indoles 5 (anhydrobases of the corresponding 2‐methyl‐1H‐benzo[e]indolium perchlorates 2 and 2‐methyl‐3H‐benzo[g]indolium perchlorates 4 , respectively) in the presence of triethylamine/acetic acid in ethanol by a 2,5‐[C₄+C₂] pyrylium ring transformation is reported. Spectroscopic data of the transformation products and their mode of formation are discussed.