Search

Polycyclic aromatic hydrocarbons (PAHs) are widely recognized as catalysts for interstellar H2 formation. Extensive exploration into the catalytic potential of various PAHs has encompassed both theoretical investigations and experimental studies. In the present study, we focused on studying the reactivity of an imperfect aromatic molecule, indene (C9H8), and its hydrogenated counterpart, indane (C9H10), as potential catalysts for H2 formation within the interstellar medium. The reactions of these molecules with H atoms at 3.1 K were investigated experimentally using the para-H2 matrix isolation technique. Our experimental results demonstrate that both indene and indane are reactive toward H atoms. Indene can participate in H-atom-abstraction and H-atom-addition reactions, whereas indane primarily undergoes H-atom-abstraction reactions. The H-atom-abstraction reaction of indene results in the formation of the 1-indenyl radical (R1) (C9H7) and H2 molecule. Simultaneously, an H-atom-addition reaction forms the 1,2-dihydro-indene-3-yl radical (R2) (C9H9). Experiments also reveal that the H-atom-abstraction reaction of indane also produces the R2 radical. To the best of our knowledge, this study represents the first reporting of the infrared spectra of R1 and R2 radicals. The experimental results, combined with theoretical findings, suggest that indane and indene may play a role in the catalytic formation of interstellar H2. Furthermore, these results imply a quasi-equilibrium between the investigated molecules and the formed radicals via H-atom-addition and H-atom-abstraction reactions. [ABSTRACT FROM AUTHOR]

Polycyclic aromatic hydrocarbons (PAHs) are widely recognized as catalysts for interstellar H2 formation. Extensive exploration into the catalytic potential of various PAHs has encompassed both theoretical investigations and experimental studies. In the present study, we focused on studying the reactivity of an imperfect aromatic molecule, indene (C9H8), and its hydrogenated counterpart, indane (C9H10), as potential catalysts for H2 formation within the interstellar medium. The reactions of these molecules with H atoms at 3.1 K were investigated experimentally using the para-H2 matrix isolation technique. Our experimental results demonstrate that both indene and indane are reactive toward H atoms. Indene can participate in H-atom-abstraction and H-atom-addition reactions, whereas indane primarily undergoes H-atom-abstraction reactions. The H-atom-abstraction reaction of indene results in the formation of the 1-indenyl radical (R1) (C9H7) and H2 molecule. Simultaneously, an H-atom-addition reaction forms the 1,2-dihydro-indene-3-yl radical (R2) (C9H9). Experiments also reveal that the H-atom-abstraction reaction of indane also produces the R2 radical. To the best of our knowledge, this study represents the first reporting of the infrared spectra of R1 and R2 radicals. The experimental results, combined with theoretical findings, suggest that indane and indene may play a role in the catalytic formation of interstellar H2. Furthermore, these results imply a quasi-equilibrium between the investigated molecules and the formed radicals via H-atom-addition and H-atom-abstraction reactions. [ABSTRACT FROM AUTHOR]

A mild procedure for the diastereoselective preparation of functionalized 1,3-dienes and their synthetic versatility are described herein. The silver-catalyzed decomposition of α-diazo-γ,δ-unsaturated esters through β-hydride migration at room temperature resulted in the stereoselective formation of 12 conjugated (1 E ,3 E)-dienes. Further synthetic post-modifications included intramolecular Heck reaction and hydrogenation, leading to a novel substituted indene and an aliphatic diester, respectively. To rationalize the observed reaction outcome, a computational investigation of the mechanisms was conducted, emphasizing the importance of factors such as metallocarbenoid stability, substituent effects, and microkinetics simulations to better understand the reaction intricacies. [ABSTRACT FROM AUTHOR]

The full width at half maximum (FWHM) of emission spectra, which plays an important role in determining color purity, may not always receive sufficient attention in the design of emissive materials. Particularly for the red emitter, the traditional focus has been on emission maxima, yet broad FWHM values can significantly change the perceived color. For example, the red color (λem=616–677 nm) emitted from reported Cu(I) complexes is perceived as orange to yellow if FWHM is large. To reduce FWHM, we incorporated a strained and rigid metalaphosphadicyclopenta[a,f]pentalene motif into Cu(I) complexes using trisphosphine ligands featuring a 1H‐indene‐2,3‐diyl backbone (ITP). Herein, we present the synthesis, structure, and emission properties of ITP‐MX and the congeners, showcasing genuinely deep‐red emission with narrow FWHM values of 56 nm. These materials exhibit color coordinates close to pure red on the CIE diagram, unlike reported broader‐emitting counterparts. Measurement of the entropy of disorder of the emissive crystal by a recently reported statistical mechanical method revealed a quantitative correlation between FWHM and the increase in the number of microstates (the degree of freedom) of the crystals and suggested that mechanical stress can increase the entropy of the crystal, which results in emission broadening. [ABSTRACT FROM AUTHOR]

[Display omitted] A series of sulfur-bridged bis(2-indenyl) zirconocenes were synthesized and tested for ethylene/1-octene co- polymerization and 1-decene oligomerization. Zirconocene bearing two 5,6-positioned methyl substituents in indenyl moieties, distant from the metal center, appeared to be an active catalyst producing 1-decene oligomers with high content of unsaturated vinylidene end groups, which is preferable for post-functionalization. [ABSTRACT FROM AUTHOR]

Sequential Knoevenagel condensation/cyclization using cyclic active methylene compounds such as Meldrum's acid have been studied. The reaction of 2-(1-phenylvinyl)benzaldehyde and Meldrum's acid, dimedone, or 1,3-indandione with piperidine/AcOH or L-proline at room temperature for 17–18 h gave cyclized indene derivatives in 63–80% yield. The reaction of 2-(3,5-dimethoxyphenyl)benzaldehyde and Meldrum's acid at room temperature for 17 h gave a fluorene derivative in 98% yield. Furthermore, the reaction of 2-(3,5-dimethoxybenzyl)benzaldehyde and Meldrum's acid with piperidine at room temperature for 18 h gave a dihydroanthracene derivative bearing Meldrum's acid in 83% yield. The reaction of 2-(3,5-dimethoxybenzyl)benzaldehyde and Meldrum's acid with piperidine at 110 °C for 2 h gave Meldrum's acid fragmentated dihydroanthracene derivative in 48% yield. The reaction mechanisms of the cyclization steps and Meldrum's acid fragmentation have been examined by the DFT calculations. [ABSTRACT FROM AUTHOR]

7-Bromo-5-(tert-butyl)-2-phenyl-1H-indene (1) and 6,7-dibromo-2,4-dimethyl-2,3-dihydro-1H-inden-1-one (2) are analyzed by single crystal X-ray diffraction. The conformational structure, vibrational spectrum of molecules, topology and hierarchical complexity of crystal structures are discussed. The structure of 1 is layered and contains (100) molecular layers of the tts topological type. The structure of 2 does not contain long molecular ensembles but demonstrates short Br⋯O contacts linking molecules into a centrosymmetric dimer. [ABSTRACT FROM AUTHOR]

Two novel diamines 1‐(4‐aminophenyl)‐1,3,3‐trimethyl‐2,3‐dihydro‐1H‐indene‐5‐amine and 4‐amino‐N‐(4‐(5‐(4‐aminobenzamide)‐1,3,3‐trimethyl‐2,3‐dihydro‐1H‐inden‐1‐yl) phenyl) benzamide containing indene and amide groups were successfully designed and synthesized, and a series of colorless polyimides (CPIs) derived from the two diamines with 1,2,4,5‐cyclohexanetetracarboxylic dianhydride in various ratios were copolymerized. The introduction of aliphatic ring structures was conducive to the improvement of optical properties, while the incorporation of amide groups improved thermal and mechanical properties. These CPI films exhibited excellent optical properties (T400 > 80%), high heat resistance (Tg > 300 °C) and mechanical properties with the synergistic action of the two groups. Furthermore, the effect of the content of amide groups on the intermolecular interaction of CPIs was systematically analyzed. This study provides a fancy method for the development of heat‐resistant colorless materials for optical applications. [ABSTRACT FROM AUTHOR]

A photoinduced palladium‐catalyzed ring‐opening hydroarylation of furans to form functionalized indenes was achieved via an intramolecular reductive coupling of aryl bromide with furan using silane as the reductant. Deuterium tracking and DFT analysis revealed a reasonable reaction pathway involving: 1) the homolytic cleavage of the furan C−O bond induced by the α‐allyl radical; 2) a 1,6‐H atom transfer from carbon to oxygen. [ABSTRACT FROM AUTHOR]

The Mn(III)-based oxidation of 1,3-indanedione (1) with 1,1-diarylethenes 2a–c effectively proceeded in boiling AcOH to produce 2,2-bis(vinyl)indanediones 5a–c and 1,2'-spirobi[indene]-1',3'-diones 6a–c via the formation of 2,2-bis(2-acetoxyethyl)indanedione 3 and acetoxyindeno[1,2-b]furan-4-one 4 intermediates. On the other hand, the Mn(III)-based aerobic oxidation of 1a with 2a at room temperature resulted in bis(endoperoxide) 8a and endoperoxypropellane 9a via the production of mono(endoperoxide) 7a. The plausible reaction pathways were also discussed. [ABSTRACT FROM AUTHOR]

A mild Pd-catalyzed three-component cascade cyclization functionalization of o-iodostyrenes, internal alkynes and boron reagents is presented. The transformation is driven by a controlled reaction sequence of intermolecular carbopalladation, intramolecular Heck-type cyclization, and a borylation process to give versatile boryl-functionalized indene skeletons in a selective fashion. Significantly, (Bpin)2, (Bneop)2 and CH2(Bpin)2 as boron sources are all tolerated. Additionally, the synthetic utility of this approach is demonstrated by gram-scale synthesis and synthetic transformations. [ABSTRACT FROM AUTHOR]

Aromatics, especially polycyclic aromatic hydrocarbons (PAHs), are important combustion pollutants known to be carcinogenic and mutagenic and are also precursors of soot and, consequently, combustion-generated particulate matters that can significantly threaten environmental security and human health. In engine combustion, the multi-component and broad-source feature of transportation fuels makes synergistic effects commonly exist and greatly enhances the formation of aromatics and soot. Understanding the synergistic effects of different fuel components on aromatic formation facilitates concrete guidance for controlling soot emissions. This review focuses specifically on the synergistic effects of aromatics formation, including benzene, indene, naphthalene, and larger PAHs, in combustion among hydrocarbon blends and hydrocarbons blended with oxygenated fuels. Progresses in experimental measurements, theoretical calculations of critical reactions, and kinetic modeling are reviewed in detail. Special attention is paid to blends of aromatics and linear fuels, which show pronounced synergistic effects in PAH formation. Furthermore, some prospects for future research on synergistic effects in aromatic formation are provided. [ABSTRACT FROM AUTHOR]

An intermolecular annulation reaction of 2‐aryl‐1,3‐indandions with alkynes was reported using Pd(OAc)2 to access spirobi[indene]‐1,3‐diones. Under palladium catalysis, the substrates form a homocoupling dimer intermediate through a catalytic dehydrogenative cross‐coupling process. The palladium(II) species could come from dimer or 2‐aryl‐1,3‐indandion. Notably, this pathway is not typically observed in enol‐directed formal sp3 C−H functionalization/oxidative annulation palladium chemistry. This transformation provides a route to access a class of functionalized spiro carbocyclic indenes. [ABSTRACT FROM AUTHOR]

Indene was polymerized to polyindene (PI) through a cationic mechanism using TiCl4•2THF complex as initiator. The cationic mechanism was investigated through electronic absorption spectroscopy and either the indanyl cation as well as the polyindenyl cation absorption bands were distinguished and assigned. The PI structure was investigated through the indane model compound and the indene reference compound electronic absorption spectra. Furthermore, the Raman spectrum of PI was recorded for the first time and the complete Raman and FT-IR absorption bands of PI are reported with the assignment of the main bands. The glass transition (Tg) of cationic, radiation-induced and thermally initiated PI were measured through DSC and the corresponding molecular weight estimated. DSC and TGA-FTIR analysis were used to study the thermal decomposition of PI. It was assessed that PI is pyrolyzed back into indene monomer in almost theoretical yield with an activation enthalpy of E# = 164 kJ/mol while the decomposition enthalpy of PI was determined at 101.6 kJ/mol a value very close to the theoretical value of 108.9 kJ/mol. It was assessed that PI is a fully recyclable polymer which could be decomposed back to the monomer and re-polymerized at will. [ABSTRACT FROM AUTHOR]

The one‐pot synthesis of λ4‐dibenzothiophen‐5‐imino‐N‐dibenzothiophenium triflate (1) in multigram scale is reported. This compound reacts with Rh2(esp)2 (esp=α,α,α′,α′‐tetramethyl‐1,3‐benzenedipropionic acid) generating a Rh‐coordinated sulfonitrene species, which is able to transfer the electrophilic nitrene moiety to olefins. When indenes are used as substrates, isoquinolines are obtained in good yields. We assumed that after formation of the corresponding N‐sulfonio aziridine, a ring expansion occurs via selective C−C bond cleavage and concomitant elimination of dibenzothiophene. Unexpectedly, a similar protocol transforms 1‐arylcyclobutenes into 1‐cyano‐1‐arylcyclopropanes. Our calculations indicate that aziridination is not favored in this case; instead, sulfilimine‐substituted cyclobutyl carbocations are initially formed, and these evolve to the isolated cyclopropanes via ring contraction. Both procedures are operationally simple, tolerate a range of functional groups, including oxidation‐sensitive alcohols and aldehydes, and enable the convenient preparation of valuable 15N‐labelled products. These results demonstrate the potential of 1 to provide alternative pathways for the selective transfer of N‐atoms in organic molecules. [ABSTRACT FROM AUTHOR]

Reaction of (P)AuOTf [P=P(t‐Bu)2o‐biphenyl] with indenyl‐ or 3‐methylindenyl lithium led to isolation of gold η1‐indenyl complexes (P)Au(η1‐inden‐1‐yl) (1 a) and (P)Au(η1‐3‐methylinden‐1‐yl) (1 b), respectively, in >65 % yield. Whereas complex 1 b is static, complex 1 a undergoes facile, degenerate 1,3‐migration of gold about the indenyl ligand (ΔG≠153K=9.1±1.1 kcal/mol). Treatment of complexes 1 a and 1 b with (P)AuNTf2 led to formation of the corresponding cationic bis(gold) indenyl complexes trans‐[(P)Au]2(η1,η1‐inden‐1,3‐yl) (2 a) and trans‐[(P)Au]2(η1,η2‐3‐methylinden‐1‐yl) (2 b), respectively, which were characterized spectroscopically and modeled computationally. Despite the absence of aurophilic stabilization in complexes 2 a and 2 b, the binding affinity of mono(gold) complex 1 a toward exogenous (P)Au+ exceed that of free indene by ~350‐fold and similarly the binding affinity of 1 b toward exogenous (P)Au+ exceed that of 3‐methylindene by ~50‐fold. The energy barrier for protodeauration of bis(gold) indenyl complex 2 a with HOAc was ≥8 kcal/mol higher than for protodeauration of mono(gold) complex 1 a. [ABSTRACT FROM AUTHOR]

Polycyclic aromatic hydrocarbon (PAH) molecules have long been suggested to be present in the interstellar medium (ISM). Nevertheless, despite their expected ubiquity and sustained searching efforts, identifying specific interstellar PAH molecules from their infrared (IR) spectroscopy has so far been unsuccessful. However, due to its unprecedented sensitivity, the advent of the JWST may change this. Meanwhile, recent years have witnessed breakthroughs in detecting specific PAH molecules (e.g. indene, cyanoindene, and cyanonaphthalene) through their rotational lines in the radio frequencies. As JWST holds great promise for identifying specific PAH molecules in the ISM based on their vibrational spectra in the IR, in this work, we model the vibrational excitation of indene, a molecule composed of a six-membered benzene ring fused with a five-membered cyclopentene ring, and calculate its IR emission spectra for a number of representative astrophysical regions. This will facilitate JWST to search for and identify indene in space through its vibrational bands and to quantitatively determine or place an upper limit on its abundance. [ABSTRACT FROM AUTHOR]

Indenyl-(Ind) and fluorenyl-(Fl) substituted NHC-stabilized alanes and gallanes (NHC)·EH2R 1–12 (NHC = IiPrMe, IiPr, IMeMe; E = Al, Ga; R = Ind, Fl) were prepared via reaction of the corresponding NHC-iodoalanes and -gallanes with LiInd and LiFl, respectively. Analogously, the alane adducts with two Ind/Fl substituents (NHC)·AlHR213–18 (NHC = IiPrMe, IiPr, IMeMe; R = Ind, Fl) were obtained by using two equivalents of LiInd/LiFl. Elimination of indene and fluorene was induced thermally affording unusual dimeric and trimeric NHC-alane adducts {(NHC)·AlH2}2-μ-Fl 19–20 and {(NHC)·AlH-μ-R}n21–23 (R = Ind, Fl; n = 2, 3) with bridging indenyl and fluorenyl ligands. [ABSTRACT FROM AUTHOR]

A cascade reaction between 2‐styrylbenzaldehydes and indoles has been developed for the synthesis of 1H‐indenes. An iodine‐catalyzed nucleophilic addition of indoles to an aldehyde group of 2‐styrylbenzaldehydes leads to the formation of carbocation intermediates that undergo 4π‐electrocyclization to give indenes with a trisubstituted double bond. These indenes are transformed into thermodynamically more stable products with a fully substituted double bond under the reaction conditions. Minor quantities of indolylbenzo[b]carbazoles are also produced as by‐products. [ABSTRACT FROM AUTHOR]

Two Mo(0) phosphenium complexes containing ancillary secondary phosphine ligands have been investigated with respect to their ability to participate in electrophilic addition at unsaturated substrates and subsequent P−H hydride transfer to "quench" the resulting carbocations. These studies provide stoichiometric "proof of concept" for a proposed new metal‐catalyzed electrophilic hydrophosphination mechanism. The more strongly Lewis acidic phosphenium complex, [Mo(CO)4(PR2H)(PR2)]+ (R=Ph, Tolp), cleanly hydrophosphinates 1,1‐diphenylethylene, benzophenone, and ethylene, while other substrates react rapidly to give products resulting from competing electrophilic processes. A less Lewis acidic complex, [Mo(CO)3(PR2H)2(PR2)]+, generally reacts more slowly but participates in clean hydrophosphination of a wider range of unsaturated substrates, including styrene, indene, 1‐hexene, and cyclohexanone, in addition to 1,1‐diphenylethylene, benzophenone, and ethylene. Mechanistic studies are described, including stoichiometric control reactions and computational and kinetic analyses, which probe whether the observed P−H addition actually does occur by the proposed electrophilic mechanism, and whether hydridic P−H transfer in this system is intra‐ or intermolecular. Preliminary reactivity studies indicate challenges that must be addressed to exploit these promising results in catalysis. [ABSTRACT FROM AUTHOR]

The radiation-induced polymerization of indene with a γ radiation source was studied at different dose rates (1, 2, 4, 6 kGy/h) and absorbed doses up to 400 kGy. The polymerization rate was determined through the thermogravimetric analysis and the spectrophotometric analysis of the irradiated indene solutions. With the two complementary methods the polymerization rates were determined for each dose rate. A mixed polymerization mechanism was ascertained involving either free radicals but also cations. In fact, the mixed mechanism was suggested as well by the n = 0.84 exponent of the dose rate in the polymerization kinetics equation and by the value of the radiation chemical yield Gp = G(−M) ≈ 103 molecules/100 eV. The infrared spectrum of the radiation-polymerized indene is analogous to the spectrum of a reference TiCl4-polyindene. However, the FT-IR spectrum of the former shows a couple of better defined and sharper infrared bands with respect to the latter, indicating a better structural regularity for the radio-polyindene. Since indene has been claimed as one of the potential polycyclic aromatic hydrocarbons (PAHs) present in the interstellar medium, our results suggest that it is likely that indene should be accompanied by -polyindene because of the monomer is very sensitive to the high energy radiation-induced polymerization. [ABSTRACT FROM AUTHOR]

Context. Indene, a small PAH, has been detected in the gas phase in the cold dense cloud TMC-1. Due to the low temperature in the cloud, below indene condensation temperature, its presence in the ice mantles of dust grains is likely. Aims. The aim of this work is to study the stability of indene against the energetic processing by VUV photons or cosmic rays in the ice mantles of dense molecular clouds. Methods. Ice layers of pure indene or indene diluted in water ice were grown by vapor deposition on a cold surface held at 10 K, 100 K, or 140 K. The samples were processed with VUV photons (120–180 nm) and 5 keV electrons and the destruction of indene was monitored by following the decay of its absorption bands in the infrared (IR) spectrum. Finally, we recorded the mass spectra of the decomposition products sublimated by thermal programmed desorption of the processed samples. Results. Photolysis and radiolysis cross-sections, along with half-life energy doses for indene in the solid form and diluted in water ice matrices at 10 K were derived. Ketones and alcohols were identified as the main processing products in indene and water–ice mixtures Conclusions. Dilution in water ice enhances the destruction rate of indene under energetic processing. The molecule is expected to survive for more than 107 yr in the ice mantles of grains in the interior of dense clouds, but it will end up getting destroyed within the next few hundred years by the intense VUV field in the diffuse region at the edges of the cloud. [ABSTRACT FROM AUTHOR]

Here, we present an electrochemically induced synthesis of 9‐sulfenylarylphenanthrenes and 3'‐sulfenylarylspiro‐cyclohexa[4.5]trienones starting from o‐alkynylbiphenyls and diaryl disulfides. This method was accomplished through constant current electrolysis of 10 mA in an undivided cell setup by utilizing CH3CN as a solvent and LiClO4 as an electrolyte at room temperature. Notably, the present strategy enabled the formation of sulfenylphenanthrenes and sulfenyl spiro cyclohexa[4.5]trienones in 70%–95% yield. Scale‐up synthesis, mechanistic studies, and cyclic voltammetry have also been carried out. [ABSTRACT FROM AUTHOR]

Fibroblast growth-factor receptor (FGFR) is a potential target for cancer therapy. We synthesised a novel series of FGFR1 inhibitors bearing quinoline, quinoxalin and isoquinoline using a synthetic strategy employing a one pot reaction, yielding 2-hydroxy-1H-indene-1,3(2H)-dione. Structural elucidation via IR, NMR and HRMS analyses is complemented by a proposed mechanistic pathway. All newly-synthesised compounds were evaluated in vitro for their inhibitory activities against FGFR-1. The most potent derivatives were 9a, 9b, 9c and 7b with IC50 = 5.7, 3.3, 4.1 and 3.1 μM, respectively, supported by molecular docking studies which probed the binding interactions of these compounds within the active site of the kinase. [ABSTRACT FROM AUTHOR]

Angiogenesis plays an important role in tumour generation and progression, which is used to supply nutrients and metastasis. Herein, a series of novel dihydro-1H-indene derivatives were designed and evaluated as tubulin polymerisation inhibitors by binding to colchicine site, exhibiting anti-angiogenic activities against new vessel forming. Through structure-activity relationships study, compound 12d was found to be the most potent derivative possessing the antiproliferative activity against four cancer lines with IC50 values among 0.028−0.087 µM. Compound 12d bound to colchicine site on tubulin and inhibited tubulin polymerisation in vitro. In addition, compound 12d induced cell cycle arrest at G2/M phase, stimulated cell apoptosis, inhibited tumour metastasis and angiogenesis. Finally, the results of in vivo assay suggested that compound 12d could prevent tumour generation, inhibit tumour proliferation and angiogenesis without obvious toxicity. Collectively, all these findings suggested that compound 12d is a novel tubulin polymerisation inhibitor deserving further research. [ABSTRACT FROM AUTHOR]

The thermal transformations of various -CH3/-H thienyl and furyl derivatives of o-divinylbenzenes in acidic media are presented. Experimental and theoretical studies were carried out to elucidate the mechanism. The formation of all furyl electrocyclization products 5-7 could be explained via mechanisms that begin with the [4+2] cycloaddition process of the starting compound. In the last step, either the release of a proton or a furyl group takes place, depending on the product formed. The mechanism of formation of indane/indene furyl 8 and 9 and thienyl thermal products III-VI starts with protonation of the double bond of the starting compound and 1,5-ring closure to give a carbocation intermediate, followed by a protonation/deprotonation process, respectively. All computational data, derived from quantum chemical DFT calculations, are in agreement with experimental results. [ABSTRACT FROM AUTHOR]

A new metal‐free synthetic approach to functionalized indenes is documented. The use of commercially available graphene oxide (GO) allowed the direct access to indenyl cores (yield up to 80 %) via intramolecular Friedel‐Crafts‐type allylic alkylations with readily available Morita‐Baylis‐Hillman alcohols. Combined experimental and spectroscopic investigations contributed to shed light on the reaction mechanism dealing with a nanostructured carbon material‐based C−C bond forming reaction. [ABSTRACT FROM AUTHOR]

Angiogenesis plays an important role in tumour generation and progression, which is used to supply nutrients and metastasis. Herein, a series of novel dihydro-1H-indene derivatives were designed and evaluated as tubulin polymerisation inhibitors by binding to colchicine site, exhibiting anti-angiogenic activities against new vessel forming. Through structure-activity relationships study, compound 12d was found to be the most potent derivative possessing the antiproliferative activity against four cancer lines with IC50 values among 0.028−0.087 µM. Compound 12d bound to colchicine site on tubulin and inhibited tubulin polymerisation in vitro. In addition, compound 12d induced cell cycle arrest at G2/M phase, stimulated cell apoptosis, inhibited tumour metastasis and angiogenesis. Finally, the results of in vivo assay suggested that compound 12d could prevent tumour generation, inhibit tumour proliferation and angiogenesis without obvious toxicity. Collectively, all these findings suggested that compound 12d is a novel tubulin polymerisation inhibitor deserving further research.

Chem. 2006, 4: 181 45 Bao, R L.-Y. Zhao, R. Shi, L. Chem. Commun. Int. Ed. 2002, 41: 4090 28 Sha, C.-K. Lee, F.-K. Chang, C J. J. Am. Chem. Soc. 1999, 121: 9875 29 Williams, J P. St. Laurent, D R. Friedrich, D. Pinard, E. Roden, B A. Paquette, L A. J. Am. Chem. Soc. 1994, 116: 4689 30 Hirst, G C. Johnson, T O. Jr. Overman, L E. J. Am. Chem. Soc. 1993, 115: 2992 31 Huang, B.-B. Lei, K. Zhong, L.-R. Yang, X. Yao, Z J. J. Org. Keywords: cyclopentaindenes; cycloaddition; enzymes; photochemistry; ring-opening EN cyclopentaindenes cycloaddition enzymes photochemistry ring-opening 1799 1803 5 08/29/23 20230915 NES 230915 Graph Substituted variants of the decahydro-1 I H i -cyclopenta[ I c i ]indene framework B 1 b (Figure 1) are found embedded in a significant range of natural products, most notably certain diterpenes and alkaloids. Oxa-di- -methane Rearrangement of a Substrate Embodying the Platencin Core Provides the Decahydro-1 H -cyclopenta[ c ]indene Framework Associated with Various Diterpenes and Certain Lycopodium Alkaloids. [Extracted from the article]

The electronic transition spectra of the indene molecular cation (In + , C 9 H 8 + ) in the 550–580 nm region has been measured in the gas phase in direct absorption. The spectra were experimentally recorded using sensitive cavity ring-down spectroscopy in a supersonically expanding planar plasma. Two lifetime-broadened vibronic bands are assigned to the 2 A ′ ′ - X 2 A ′ ′ electronic transition system of In + . A set of indicative spectroscopic parameters have been obtained from a band contour analysis of the 0 0 0 band in combination with supporting ab-initio calculations. The inferred Lorentz line width of 4.0 ± 0.5 cm − 1 indicates an upper state lifetime of 1.2 ± 0.1 ps . The laboratory data are compared to the diffuse interstellar bands (DIBs), and no matches can be found. Upper limits for In + column densities in the diffuse interstellar medium have also been estimated from six sightline spectra. [ABSTRACT FROM AUTHOR]

The electronic transition spectra of the indene molecular cation (In + , C 9 H 8 + ) in the 550–580 nm region has been measured in the gas phase in direct absorption. The spectra were experimentally recorded using sensitive cavity ring-down spectroscopy in a supersonically expanding planar plasma. Two lifetime-broadened vibronic bands are assigned to the 2 A ′ ′ - X 2 A ′ ′ electronic transition system of In + . A set of indicative spectroscopic parameters have been obtained from a band contour analysis of the 0 0 0 band in combination with supporting ab-initio calculations. The inferred Lorentz line width of 4.0 ± 0.5 cm − 1 indicates an upper state lifetime of 1.2 ± 0.1 ps . The laboratory data are compared to the diffuse interstellar bands (DIBs), and no matches can be found. Upper limits for In + column densities in the diffuse interstellar medium have also been estimated from six sightline spectra. [ABSTRACT FROM AUTHOR]

We report the detection of large hydrocarbon cycles toward several cold dense clouds. We observed four sources (L1495B, Lupus-1A, L483, and L1527) in the Q band (31−50 GHz) using the Yebes 40 m radiotelescope. Using the line stack technique, we find statistically significant evidence of benzonitrile (C6H5CN) in L1495B, Lupus-1A, and L483 at levels of 31.8σ, 15.0σ, and 17.2σ, respectively, while there is no hint of C6H5CN in the fourth source, L1527. The column densities derived are in the range (1.7−3.8) × 1011 cm−2, which is somewhat below the value derived toward the cold dense cloud TMC-1. When we simultaneously analyze all the benzonitrile abundances derived toward cold clouds in this study and in the literature, a clear trend emerges in that the higher the abundance of HC7N, the more abundant C6H5CN is. This indicates that aromatic cycles are especially favored in those interstellar clouds where long carbon chains are abundant, which suggests that the chemical processes that are responsible for the formation of linear carbon chains are also behind the synthesis of aromatic rings. We also searched for cycles other than benzonitrile, and found evidence of indene (C9H8), cyclopentadiene (C5H6), and 1-cyano cyclopentadiene (1-C5H5CN) at levels of 9.3σ, 7.5σ, and 8.4σ, respectively, toward L1495B, which shows the strongest signal from C6H5CN. The relative abundances between the various cycles detected in L1495B are consistent – within a factor of three – with those previously found in TMC-1. It is therefore likely that not only C6H5CN but also other large aromatic cycles are abundant in clouds rich in carbon chains. [ABSTRACT FROM AUTHOR]

Regiodivergent [3+2] and [4+2] C−H annulation of imines and imidate esters with unsymmetrical alkynes has been achieved under Rh(III) catalysis. Further transformation of the aldehyde and TMS functionality on the indene products is also demonstrated. The current work highlights the alcohols‐directed multiple C−H annulation of imines and imidate esters, leading to diverse fused heterocycles. [ABSTRACT FROM AUTHOR]

Palladium-catalyzed cross-coupling of ortho -alkenyl bromobenzenes and α-aryl-α-diazoesters was realized. The reactions proceeded in moderate to excellent yields with broad substrate scope, providing a straightforward method for the synthesis of 1,1-disubstituted indenes. The reaction is thought to undergo a tandem alkenyl C–H activation/carbene insertion sequence, in which a C,C-pallada(II)cycle is the key intermediate. [ABSTRACT FROM AUTHOR]

Comprehensive Summary: The chemodivergent ring‐opening of cyclobutanols is described under the carbocatalytic assistance of graphene oxide (GO). The protocol enables the synthesis of diversely functionalized dienes or indenes (26 examples) based on the amount of GO employed. Spectroscopic (XPS and ssNMR) as well as experimental investigations revealed a direct involvement of the π‐domains of GO in tuning the stability of carbocationic intermediates during the reaction. [ABSTRACT FROM AUTHOR]

A NaH‐promoted domino reaction between azadiene bearing an indene moiety with Nazarov reagent was developed. A variety of spiro[4.5]decane derivatives were obtained via [4+2] cycloaddition with good yields and high diastereoselectivity. The domino strategy benefited from mild reaction conditions and very broad substrate scope. Furthermore, a gram‐scale experiment and a transformation of the product were carried out. Lastly, density functional theory (DFT) calculations have been performed to verify the proposed reaction mechanism and analyze the observed diastereoselectivity. [ABSTRACT FROM AUTHOR]

The 19F NMR chemical shifts of 13 trifluoromethyl derivatives of alkenes, pyrimidines, and indenes were calculated at the DFT level using the BhandHLYP, BHandH, PBE, PBE0, O3LYP, B3LYP, KT2, and KT3 functionals in combination with the pcS‐2 basis set. Best result was documented for the BHandHLYP functional: The mean absolute error (MAE) of 0.66 ppm for the scaled values was achieved for the range of about 20 ppm. Solvent, vibrational, and relativistic corrections were found to be rather small, especially when taken in combination, generally demonstrating a slight decrease in the difference between calculated and experimental fluorine chemical shifts. As a measure of the practical importance of these compounds, one should recall that the growing number of life science products that contain trifluoromethyl groups provides a continuing driving force for the development of an effective methodology that enables both regio‐ and stereoselective introduction of trifluoromethyl groups into both aliphatic and aromatic systems. [ABSTRACT FROM AUTHOR]

Several 4,6-diphenyl-4,5,6,7-tetrahydro-3-selena-1,2,5-triazo-indene derivatives have been synthesized by the Mannich reaction (condensation) of ethyl methyl ketone, substituted aldehyde and ammonium acetate and selenium dioxide. The chemical structures have been confirmed by means of IR, ¹H NMR and mass spectral data. The synthesized compounds have been evaluated for anti-inflammatory, analgesic and antitubercular activity. The compounds have emerged as the most promising active compounds to that of standards. In addition, the inhibition effect increases with the increase in concentration of these compounds. [ABSTRACT FROM AUTHOR]

Cycloadditions are an important class of reactions in materials science for the construction of polycyclic aromatic and polycyclic heteroaromatic compounds. Recently, cycloadditions have been expanded beyond the "classical" group of cycloadditions involving six π‐electrons, and it is now possible to control cycloadditions for an extended number of π‐electrons by applying organocatalysis. This novel field of cycloadditions–termed higher‐order cycloadditions–allows new synthetic methodologies to construct polycyclic carbo‐ and heteroaromatic compounds in two or three dimensions. This concept presents higher‐order cycloadditions as a method for accessing two‐ and three‐dimensional azulenes and cyclazines, as well as three dimensional indenes, as polycyclic aromatic and polycyclic heteroaromatic compounds. [ABSTRACT FROM AUTHOR]

A series of potentially bioactive compounds having either indole or indene frameworks such as dihydroindenone and indolinone derivatives were synthesized in good to high yields by one-pot, multi-component reaction of various amines, trichloroacetonitrile, ninhydrin or isatin, and 2-hydroxy-1,4-naphthoquinone. The present method offers desirable advantages including mild conditions, absence of catalyst, simple workup procedure, and easy purification process with no chromatographic technique. [ABSTRACT FROM AUTHOR]

Indene (IND) is a kind of important aromatic hydrocarbon that is extracted from coal tar and has important applications in industry and biology. In the process of production and utilization, it is easy to enter the soil and produce toxic effects on the soil or organisms. The earthworm is an important organism in the soil. The toxicity of indene on earthworm coelomocytes is rarely studied, and the oxidative stress effects of IND on earthworm coelomocytes remain unclear. In this study, coelomocytes from earthworms and antioxidant enzymes were selected as the research targets. In addition, IND caused oxidative stress, and its related toxic effects and mechanisms were systematically studied and evaluated at the cellular and molecular levels. The results showed that IND destroyed the redox balance in earthworm coelomocytes, and the large accumulation of reactive oxygen species (ROS) significantly inhibited the activities of the antioxidant system, including superoxide dismutase (SOD), catalase (CAT), and glutathione (GSH), and caused lipid peroxidation and membrane permeability changes, resulting in a decrease in cell viability to 74.5% of the control group. At the molecular level, IND was bound to SOD by the arene-H bond, and the binding constant was 4.95 × 103. IND changed the secondary structure of the SOD and led to a loosening of the structure of the SOD peptide chain. Meanwhile, IND caused SOD fluorescence sensitization, and molecular simulation showed that IND was mainly bound to the junction of SOD subunits. We hypothesized that the changes in SOD structure led to the increase in SOD activity. This research can provide a scientific basis for IND toxicity evaluation. [ABSTRACT FROM AUTHOR]

The identification of accelerant about gasoline and other ignited liquids in arson has always been a difficult problem in the field of physical evidence identification. How to avoid “false positive” and “false negative” results is a key issue. To study the interference of diene rubber on gasoline identification from two aspects of “false positives” and “false negatives”, and to explore its degree when gasoline was mixed with diene rubber in different proportions, the combustion residues obtained from cis-polybutadiene rubber, isobutylene isoprene rubber and styrene butadiene rubber after loading different amounts of gasoline were compared using gas chromatography-mass spectrometry (GC-MS). The results showed that alkanes, alkenes/cycloalkanes, aromatic-alkylbenzenes, homologs of indenes and indanes, alkylnaphthalenes and polycyclic aromatic hydrocarbons were detected in the combustion residues of the three kinds of diene rubber samples before and after gasoline loading, which was consistent with gasoline in terms of the characteristic components categories and had strong interference with gasoline identification. After loading 0.05 mL and 0.1 mL gasoline respectively into 5 g rubber sample, there was no significant changes in the characteristic components of cycloalkanes/alkenes, alkylnaphthalenes, and polycyclic aromatic hydrocarbons in the rubber combustion residues. The number and relative peak area ratio of characteristic peaks corresponding to aromatic-alkylbenzenes, homologs of indenes and indanes changed to different degrees, while the changes of alkylbenzenes were more representative. Loading gasoline or not had little effect on the ratio of the characteristic peaks of C2 benzene components in the combustion residues of cis-polybutadiene rubber. The ratio among three characteristic peaks of C2 benzene components in the combustion residues of isobutylene isoprene rubber and styrene butadiene rubber samples changed significantly when the gasoline loading amount reached 0.1 mL. This study can provide important references for the gasoline identification when there is a presence of diene rubber matrix in practical work. [ABSTRACT FROM AUTHOR]

As acetylcholinesterase (AChE) plays a crucial role in advancing Alzheimer's disease (AD), its inhibition is a promising approach for treating AD. Sulindac is an NSAID of the aryl alkanoic acid class, consisting of a indene moiety, which showed neuroprotective behavior in recent studies. In this study, newer Indene analogs were synthesized and evaluated for their in vitro AChE inhibition. Additionally, compared with donepezil as the standard drug, these Indene analogs were accessed for their cell line-based toxicity study on SH-SY5Y cell line. The molecule SD-30, having hydrogen bond donor (HBD) at para-position, showed maximum AChE inhibition potential (IC50 13.86 ± 0.163 µM) in the indene series. Further, the SD-30 showed maximum BuChE inhibition potential (IC50 = 48.55 ± 0.136 µM) with a selectivity ratio of 3.50 and reasonable antioxidant properties compared to ascorbic acid (using DPPH assay). SD-30 (at a dose level: of 10 µM, 20 µM) effectively inhibited AChE-induced Aβ aggregation and showed no significant toxicity up to 30 mM against SH-SY5Y cell lines. [ABSTRACT FROM AUTHOR]

[Display omitted] • Indene hydrogenation, as potential LOHC, is studied on different alumina- and carbon-supported Pd, Pt, Rh and Ru catalysts. • First hydrogenation step (indane) is fast over all the considered catalysts. • Indane hydrogenation to hydrindane is slower, especially with Pd. • Rh-based catalysts are the most active, especially after activation. • Langmuir-Hinshelwood kinetic models are useful for predicting catalyst performance. We propose in this article the use of indene, obtained from the light fraction of coal tar rectification, as a Liquid Organic Hydrogen Carrier (LOHC), with a thorough study of its hydrogenation. The hydrogenation process, conducted on noble metal catalysts (Pd, Pt, Rh, and Ru) supported by activated carbon or alumina, involves the rapid conversion of indene to indane, followed by the formation of cis- and trans -hydrindane. Carbon-supported catalysts exhibited faster reactions rates, with catalytic activities varying among metal phases, Rh and Ru being the most active. Indene was found to have an inhibitory effect on the hydrogenation reactions. While Ru catalysts enhance cracking, Rh catalysts are the most selective for total hydrogenation. The study highlights that Ru catalysts favour cracking reactions more than Rh. The proposed reaction mechanisms involve successive steps and follow a Langmuir-Hinshelwood type kinetics, confirming the inhibitory effect of indene. [ABSTRACT FROM AUTHOR]

[Display omitted] • Stability hierarchy of the indene isomers is 1H-indenes > 2H-indenes > 5H-indenes > 4H-indenes. • Structural, electronic and magnetic indices were used for evaluation of hyperconjugative aromaticity. • Group Ge(CH 3) 3 induces stronger hyperconjugative aromaticity than other substitutions. • Electron-withdrawing fluorine groups on C sp 3 result weak hyperconjugative aromaticity. • As electron-donating capacity of substitutions in 1H-indenes increases, aromaticity of phenyl ring decreases. In the present research, the Schleyer hyperconjugative aromaticity was used to enhance the aromaticity of indene scaffolds. The first section of the research focused on examining the thermodynamic stability and electronic characteristics of the four structural isomers of indene. Results indicate that 1H-indene scaffolds are the most stable thermodynamic isomers of indene derivatives exceeding 100 kJ/mol. The hierarchy of stability is as follows: 1H-indenes > 2H-indenes > 5H-indenes > 4H-indenes. The aromaticity of 5- and 6-membered rings in the isomeric structures was investigated using the B3LYP/6–311 + G(d,p) method in the second section of the study. The hyperconjugative aromaticity of 5MR and 6MR was assessed using the harmonic oscillator model of aromaticity index, Bird index, Shannon index, aromatic fluctuation index, and the nucleus independent chemical shift. The results reveal that introducing electron-donating groups on 6MR enhances the aromaticity of 5MR. Moreover, adding two fluorine atoms on the C sp 3 site negatively affects the aromaticity and induces antiaromaticity in the indene scaffold. Based on aromaticity data, the order of increasing aromaticity in the presence of different groups is F < CH 3 < H < SiH 3 < GeH 3 < Si(CH 3) 3 < Ge(CH 3) 3. The extent of the Schleyer hyperconjugation interaction was also quantified using the E(2) parameter obtained from the NBO calculations. [ABSTRACT FROM AUTHOR]

The degradation of indene is investigated using molecular dynamics (MD) with the ReaxFF force field and RRKM theory. Microcanonical rate constants are obtained over a broad energy range (8–25 eV). There is agreement between the results of the molecular dynamics and RRKM calculations at the lower energies, while the molecular dynamics rate constants are larger at the higher energies. At the lower energies there is also agreement with values obtained by using expressions for photodegradation of polyaromatic hydrocarbons from the literature. Values from those expressions however increase even faster with energy than our molecular dynamics rate constants do. At the same time those values are lower than an experimental result at 6.4 eV. This suggests that astrochemical models employing those values may result in unreliable polycyclic aromatic hydrocarbons abundances.

Comprehensive Summary: Aryl sulfonyl radical triggered cascade cyclization of phenyl‐linked 1,6‐enynes for the synthesis of biologically important indenes containing alkenyl C—X bonds and 10a,11‐dihydro‐10H‐benzo[b]fluorines is presented. In these radical cascade processes, three new chemical bonds, including C—S, C—C, and C—X bonds, and three C—C bonds are formed in one step. The method is attractive and valuable due to its metal‐free, mild reaction conditions, broad substrate scope and good functional group tolerance. [ABSTRACT FROM AUTHOR]

Although palladium‐catalyzed asymmetric C−H functionalization and Heck reactions represents one of the most important synthetic strategies for the construction of quaternary stereocenters, developing the enantioselective version of PdII‐catalyzed carbopalladation‐initiated cascade reactions still remains a formidable challenge. Herein, an unprecedent enantioselective [3+2] annulation of oxime ethers and alkynes has been developed, providing both spiro and nonspiro indenes bearing all‐carbon quaternary stereocenters in good yields (up to 98 %) with excellent enantioselectivities (up to >99 % ee). This annulation is accomplished by merging the PdII‐catalyzed atroposelective C−H activation/double carbopalladation and the transient axial‐to‐central chirality transfer process, constituting the first successful example of catalytic chirality transfer strategy involving axially chiral styrene intermediate. [ABSTRACT FROM AUTHOR]

Iridium-catalyzed asymmetric C–H addition of an N-methyl group on 3-trifluoromethyl-2-(N-methylamino)pyridine to cyclic alkenes was realized by using a phosphine–olefin ligand. Indene and its 7-substituted derivatives, acenaphthylene, and some bicyclic alkenes underwent the addition to give the corresponding products in good yields with high enantioselectivity. [ABSTRACT FROM AUTHOR]

Reactions of 5,5,5-trichloropent-3-en-2-one Cl3CCH=CHC(=O)Me with arenes in Brønsted superacid CF3SO3H at room temperature for 2 h–5 days afford 3-methyl-1-trichloromethylindenes, a novel class of indene derivatives. The key reactive intermediate, O-protonated form of starting compound Cl3CCH=CHC(=OH+)Me, has been studied experimentally by NMR in CF3SO3H and theoretically by DFT calculations. The reaction proceeds through initial hydroarylation of the carbon-carbon double bond of starting CCl3-enone, followed by cyclization onto the O-protonated carbonyl group, leading to target indenes. In general, 5,5,5-trichloropent-3-en-2-one in CF3SO3H acts as a 1,3-bi-centered electrophile. [ABSTRACT FROM AUTHOR]