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A facile and expeditious protocol for the synthesis of difunctionalized indenes from readily available benzimidates and nitroalkenes through rhodium‐catalyzed C−H activation and cyclization is reported here. The transformation exhibits powerful reactivity, tolerates a large number of functional groups, and proceeds in moderate to high yields under an ambient atmosphere, providing a straightforward method to access structurally diverse and valuable difunctionalized indene derivatives. [ABSTRACT FROM AUTHOR]

A highly efficient rhodium(III)‐catalyzed synthesis of novel functionalized indene derivatives has been achieved via C−H activation/intramolecular aldol condensation. This cascade reaction is an atom economical protocol which could be further applied to build more complex compounds. [ABSTRACT FROM AUTHOR]

It is a great challenge to design n‐channel donor‐acceptor (D−A) type small molecules because of the lack of strong electron withdrawing acceptor unit. Herein, 3‐(dicyanomethylidene)‐indan‐1‐one (IC) and 1,3‐bis(dicyanomethylidene)‐indene (IDC) based D−A type small molecular organic semiconductors IC–DDTPTI and IDC‐DDTPTI are synthesized and characterized. Both compounds have low‐lying LUMO energy levels, especially for IDC‐DDTPTI with LUMO energy level lower than −4.0 eV. Thin film transistor characteristics show IC–DDTPTI displays ambipolar transistor behavior with balanced hole and electron mobility. The electron mobility is 0.40 cm2 V−1 s−1 and the hole mobility reaches 0.18 cm2 V−1 s−1. IDC‐DDTPTI exhibits unipolar n‐channel character with an electron mobility of 0.027 cm2 V−1 s−1. These results highlight the applications of IC and IDC units in high performance D−A type n‐channel organic semiconductors. [ABSTRACT FROM AUTHOR]

A one-pot method for the simple, efficient, and environmentally benign protocol for the synthesis of Spiro-Indoline/Indene derivatives containing Aza indole moiety as a side chain is outlined. The 1,3-dipolar cycloaddition reaction of azomethine ylides derived from ethynyl Azaindole under mild conditions is accomplished. The low cost, easy availability of the starting material, and simple reaction conditions suggest the possible use of the present method for large-scale preparations. [ABSTRACT FROM AUTHOR]

A novel, efficient and convenient procedure has been developed for the synthesis of 2-(4-amino-substituted benzylidene)indanone derivatives. In the first step, the reaction of 4-fluorobenzaldehyde with 5, 6-dimethoxy-2, 3-dihydro-1H-inden-1-one in the presence of NaOH in EtOH was described. In the next step, a variety of aliphatic and aromatic amines were reacted with 2-(4-fluorobenzylidene)-5, 6-dimethoxy-2, 3-dihydro-1H-Inden-1-one via aromatic substitution (SNAr) reaction to produce 2-(4-aminobenzylidene)-5, 6-dimethoxy-2, 3-dihydro-1H-Inden-1-one derivatives as a novel class of 1-indanones. These products have been successfully prepared in good to excellent yields. 1 H and 13 C NMR, FT-IR spectroscopy and CHN analysis supported the proposed structures of the products. [ABSTRACT FROM AUTHOR]

The first syntheses and characterizations of 6,7a-dichloro-3a-hydroxyoctahydro-1H-indene-2,5-diyl diacetates were successfully obtained starting from indan-2-ol. Epoxidation of 2 was carried out using mCPBA in methylene chloride followed by acetylation using acetyl chloride to furnish the diacetates. The structures of all synthesized compounds were characterized by spectroscopic methods. [ABSTRACT FROM AUTHOR]

Abstract: 1‐Aryl‐3,3‐bis(pivaloyloxy)propynes can be converted in good to high yields into either 1,3‐ or 1,2‐bis(pivaloyloxy)indenes, depending on the N‐heterocyclic carbene (NHC) gold(I) hexafluoroantimonate catalyst used. Almost exclusive formation of 1,3‐di(oxycarbonyl)indene derivatives was achieved with cationic gold complexes containing the embracing N,N′‐1,3‐bis(9‐butylfluorenyl)benzimidazolylidene ligand (nBuFNHC). The regioselective issue of the reaction was rationalized by the specific spatial distribution of the steric bulk in the nBuFNHC ligand. In contrast, only modest selectivities in favor of 1,2‐disubstituted indenes were observed with more classical NHC gold complexes, the best selectivity being then obtained with N,N′‐1,3‐bis(2,6‐diisopropylphenyl)‐4,5‐dihydroimidazolylidene gold chloride (SIPrAuCl) as precatalyst. [ABSTRACT FROM AUTHOR]

An efficient one-pot synthesis of indenes from simple starting materials is presented. This process involves a dual C-C bond formation through an intermolecular Heck coupling reaction followed by acid-mediated intramolecular cyclodehydration. The strategy is amenable to various substituted aro- matics to give indenes. In addition, the regioselective synthesis of benzyl styrenes in a single column purification technique through in-situ reduction of Heck products (ketones) followed by acid mediated dehydration of crude reaction mixture is presented. [ABSTRACT FROM AUTHOR]

Abstract: A new approach to the synthesis of highly substituted cyclopentadienes, indenes, and cyclopentene‐fused heteroarenes by means of the Pd‐catalyzed Trost–Oppolzer‐type intramolecular Alder–ene reaction of 2,4‐pentadienyl acetates is described. This unprecedented transformation combines the electrophilic features of the Tsuji–Trost reaction with the nucleophilic features of the Alder–ene reaction. The overall outcome can be perceived as a hitherto unknown “acid‐free” iso‐Nazarov‐type cyclization. The versatility of this strategy was further demonstrated by the formal synthesis of paucifloral F, a resveratrol‐based natural product. [ABSTRACT FROM AUTHOR]

A rhodium(II)- or copper(I)-catalyzed formal intramolecular carbene insertion into vinylic C(sp2)−H bonds is reported herein. This method provides straightforward access to 1 H-indenes with high efficiency and excellent functional-group compatibility. Mechanistically, the reaction is proposed to involve the following sequence: metal carbene formation, intramolecular nucleophilic addition of the double bond to the electron-deficient carbene carbon atom, dearomatization, and finally a 1,5-H shift. [ABSTRACT FROM AUTHOR]

The rhodium(III)-catalyzed C−H alkylation and intramolecular cyclization of aldimines with enones are described. This transformation provides direct access to the formation of C2-carbonyl-substituted indene derivatives with excellent site-selectivity and functional group compatibility. [ABSTRACT FROM AUTHOR]

The first enantioenriched synthesis of 1,1,3-trisubstituted (trifluoromethyl)indene derivatives, bearing a quaternary stereogenic carbon center, is reported using a simple chiral sulfinamide phosphine-catalyzed asymmetric allylic alkylation of a mixture of indenes with Morita-Baylis-Hillman carbonates. The resulting derivatives can serve as a valuable synthetic building block for some drugs and natural products. Broad substrate scope and high regio- and enantioselectivity of this reaction were particularly remarkable. [ABSTRACT FROM AUTHOR]

The formal (3+2) cycloaddition between terminal allenes and aryl or styryl gold(I) carbenes generated by a retro-Buchner reaction of 7-substituted 1,3,5-cycloheptatrienes led to indenes and cyclopentadienes, respectively. These cycloaddition processes have been applied to the construction of the carbon skeleton of the cycloaurenones and the dysiherbols as well as to the total synthesis of (±)-laurokamurene B. [ABSTRACT FROM AUTHOR]

A new and versatile multicomponent domino strategy has been developed for the synthesis of a series of 1H-indene and phthalimide derivatives from simple and readily available starting materials. This process operating under mild conditions shows a broad substrate scope with moderate to excellent yields. [ABSTRACT FROM AUTHOR]

The addition of trimethylsilyl esters of trivalent phosphorus acids to trimethylsilyl ester of 1 H-indene-3-carboxylic acid has been studied. The convenient syntheses of new functionalized organophosphorus acids and their derivatives with indan-1-carboxylic acid moieties have been proposed. Water-soluble sodium salts of the corresponding acids were also obtained. [ABSTRACT FROM AUTHOR]

A novel synthesis of 1,1-disubstituted 1H-indenes is described involving the Pd-catalyzed cascade reaction between o-bromophenyl-β-bromostyrenes and N-tosylhydrazones in a process comprising the consecutive formation of two Csp³-C bonds on the same carbon atom: the cross-coupling of the N-tosylhydrazone with the alkenyl bromide and the intramolecular Heck reaction on the newly formed double bond. A similar approach has been applied to the preparation of 1,1-disubstituted naphthalenes. [ABSTRACT FROM AUTHOR]

Enantioenriched indenes were reached through a chirality conversion strategy using original axially chiral benzylidene cyclanes. Good to high remote diastereocontrol and excellent enantiocontrol were observed in this cascade involving copper-catalyzed homologation of terminal alkynes, in situ allenoate formation and Alder-ene cyclization. [ABSTRACT FROM AUTHOR]

Efficient rhodium-catalyzed oxidative decarboxylation annulation reactions between mandelic acids and alkyne derivatives are described. The desired indenone products were obtained in medium to good yields under the optimized reaction conditions, which were a [RhCp*Cl2]2 catalyst (10.0 mol %) in combination with a PCy3 ligand (10.0 mol %) and AgSbF6 (10 mol %) and Cu(OAc)2 (20 mol %) additives. Many functional groups are compatible with the reaction under the optimized reaction conditions. This strategy provides a promising method for the construction of indenones from cheap and commercially available starting materials. [ABSTRACT FROM AUTHOR]

The tricyclic intermediate 2 has been synthesized in eight steps from known compound 6 in 20% overall yield. As such, this constitutes a highly efficient formal synthesis of (±)-aplykurodinone-1. This synthesis features a unique, one-pot, intramolecular hetero-Pauson-Khand reaction (h-PKR)/desilylation sequence to expeditiously construct the tricyclic framework, providing valuable insights for expanding the scope and boundaries of h-PKR. [ABSTRACT FROM AUTHOR]

An efficient iodine-mediated regioselective tandem approach for the synthesis of symmetric and asymmetric iodo-substituted indenes and stereoselective cyclopenta [ b]pyridine/thiophenes from easily accessible enediynes that proceeds by in situ formation of an iodonium intermediate followed by a regioselective 5-endo-dig cyclization has been described. The intramolecular electrophilic iodocyclization was selectively triggered by a distribution of electronic density along the alkyne bond. Subsequently, the iodo-substituted indenes were diversified by employing palladium-catalyzed cross-coupling reactions and the coupled products were further confirmed by X-ray crystallographic studies. [ABSTRACT FROM AUTHOR]

The enantio- and diastereoselective formation of indenes spirofused to highly substituted cyclopropanes is described. The application of a new cinchona alkaloid derived ammonium salt in a phase transfer catalysis setup facilitates high selectivity and excellent yields at low catalyst loadings (0.1–1.0 mol%). [ABSTRACT FROM AUTHOR]

Gold-catalyzed [3+2]-annulations of α-aryl diazonitriles with ynamides and allenamides yield 1-amino-1H-indenes in two distinct pathways; the success of these annulations relies on the high electrophilicity of α-cyano arylgold carbenes to activate an ionic pathway. [ABSTRACT FROM AUTHOR]

The asymmetric formation of spiroindenes containing up to four contiguous stereocenters from the reaction of benzofulvenes with 2,4-dienals through trienamine catalysis is described. The benzofulvene core was found to be an excellent starting point for the synthesis of interesting spiroindenes through a formal cycloaddition pathway. The reaction was mediated by a diphenylprolinol silyl ether catalyst, and a diverse array of spiroindenes were obtained in high yields with excellent stereoselectivity. An attractive feature of the developed system is the possibility to diversify the product scaffold significantly by further manipulation of the chiral spiroindenes. Thus, three intramolecular ring-closing reactions following the organocatalytic step resulted in highly complex polycyclic systems. [ABSTRACT FROM AUTHOR]

A facile synthesis of highly functionized indanone fused multicyclic pyrrolines using the heterocyclic ketene aminal and ninhydrin is described. Derivative alkoxyl or amine substituted analogues were also directly achieved upon adding alcohols or amines as corresponding starting materials. The reaction conditions are environment friendly and have a good tolerance towards a variety of heterocyclic ketene aminals. A library including three series of molecularly diverse indanone fused pyrrolines with potential bioactivities was demonstrated to be rapidly constructed with good to excellent yields. [ABSTRACT FROM AUTHOR]

The aim of this study was to design new molecules and evaluate their anticholinesterase and amyloid beta (Aβ1–42) inhibition activities as multifunctional drug candidates for the treatment of Alzheimer’s disease (AD). A series of 5,6-dimethoxy-1H-indene-2-carboxamides (1–22) was synthesized; cholinesterase inhibitory activities of the compounds were measured according to Ellman’s colorimetric assay, while the thioflavin T assay was used for measuring the inhibition of Aβ1–42aggregation. The results revealed that most compounds showed higher inhibitory activity against BuChE than AChE. Compounds20and21were found to be the most potent BuChE inhibitors with respective IC50values of 1.08 and 1.09 μM. Compounds16,20,21and22exhibited remarkable inhibition of Aβ1–42aggregation. Kinetic analysis showed that the most potent BuChE inhibitor (20) acted as a noncompetitive inhibitor. Docking studies suggested that inhibitor20displayed many potential hydrogen-bondings with the PAS of BuChE. These results suggest that compound20may be an especially promising multifunctional drug for the prevention and treatment of AD. [ABSTRACT FROM AUTHOR]

A concise synthesis of functionalized indene derivatives via the gold(i)-catalysed cascade C–H functionalization/conia-ene type reaction of electron-rich aromatics with o-alkynylaryl α-diazoesters has been developed. In this transformation, the gold catalyst not only catalysed the formation of the zwitterionic intermediate via intermolecular C–H functionalization but promoted the subsequent intramolecular 5-endo-dig cyclization via activation of alkynes. The reaction is characterized by high chemo- and site-selectivity, readily available starting materials, nice functional-group tolerance and mild reaction conditions. [ABSTRACT FROM AUTHOR]

The three-component reaction of N-phenacylbenzothiazolium bromides, aromatic aldehydes and indane-1,3-dione in ethanol at room temperature in the presence of triethylamine as base afforded functionalized spiro[benzo[ d]pyrrolo[2,1- b]thiazole-3,2′-indenes] in good yields and with high diastereoselectivity. The 1H NMR data and single crystal structure clearly indicated that the obtained spiro compounds predominately have one diastereoisomer. [ABSTRACT FROM AUTHOR]

ABSTRACT The CuI-catalyzed addition of iodine to the C≡C triple bond of 3,3-diethoxy-1-phenyl propyne ( 1) unexpectedly leads to the new cyclization products 2,3-diiodo-1 H-inden-1-one ( 2) and 1-ethoxy-2,3-diiodo-1 H-indene ( 3). Both compounds were isolated and characterized via 1H, 13C NMR (Nuclear Magnetic Resonance) spectroscopy and HRMS (High Resolution Mass Spectrometry). The molecular and crystal structures of compounds 2 and 3 were determined by single crystal X-ray diffraction. Their crystal structures are governed by extensive halogen bonding, involving I·I and I·O interactions. [ABSTRACT FROM AUTHOR]

A new chemoselective iodocarbocyclization of allenyl arenes was developed leading to the formation of 2-iodoindenes. In acetonitrile or nitromethane, electrophilic sources of iodine cations react selectively with the C2-C3 double bond of 1-arylallenes to give, after anti nucleophilic attack of the aromatic ring, 2-iodoindene products in high yields. Variations of the allenic skeletons revealed the high 5-endo selectivity and some competitive pathways of cyclization. Postfunctionalization reactions of the carbon-iodine bond, via Pd- and Cu-cross-couplings, gave rise to substituted indenes in good to excellent yields. [ABSTRACT FROM AUTHOR]

Chiral cyclopentadienyl rhodium complexes promote highly enantioselective enol-directed C(sp2)-H functionalization and oxidative annulation with alkynes to give spiroindenes containing all-carbon quaternary stereocenters. High selectivity between two possible directing groups, as well as control of the direction of rotation in the isomerization of an O-bound rhodium enolate into the C-bound isomer, appear to be critical for high enantiomeric excesses. [ABSTRACT FROM AUTHOR]

A novelSnCl4-promoted tandem reaction toward multisubstitutedindenes via a sequential C–O bond cleavage/Nazarov cyclization/nucleophilicaddition reaction has been developed to afford a series of multisubstitutedindenes with an all-carbon quaternary center in moderate to good yields. [ABSTRACT FROM AUTHOR]

Indium(III)-catalyzed cyclization reactions of aromatic 5-enynamides were studied. Indium triflate enabled the efficient synthesis of 2-aminonaphthalenes and 2-amino-1 H-indenes from aromatic N-methyl- N-tosyl-ynamides bearing an ortho-vinyl and -isobutenyl group, respectively. The aromatic N-3-arylpropargylynamides bearing an ortho-gem-dihalovinyl subunit underwent a tandem cyclization/carbobromination reaction in the presence of indium tribromide to provide the dibrominated 2,3-dihydro-1 H-indeno[2,1- b]pyridine derivatives in good yields. [ABSTRACT FROM AUTHOR]

The selective dehydration of 1-indanol in liquid-phase was studied at 363 K and 2 bar, over solid acid catalysts, and using cyclohexane as a solvent. Mesoporous SiO 2 –Al 2 O 3 with a high density of strong Lewis acid sites produced di-1-indanyl ether and other heavy products apart from indene. In contrast, the overall selectivity to indene with beta zeolite (HBEA, Si/Al = 12.5), HZSM-5 (Si/Al = 20) and dealuminated mordenite zeolite (HMOR, Si/Al = 80) was almost 100%. The transition state shape selectivity and a moderate density of both Lewis and Brønsted acid sites were crucial to achieve high selectivity to indene. In spite of the high overall selectivity, the final yield in indene with HBEA was only 55%. This was attributed to the formation of heavy compounds inside the large cavities of HBEA, which cannot diffuse through its micropores. In contrast, yields in indene higher than 90% were obtained with HMOR and HZSM-5. It was also observed that the yield in indene increased with time even after reaching the 1-indanol total conversion, which indicates the slow diffusion of the reactant and product molecules inside of the microporous network of HMOR and HZSM-5. Therefore, a process involving liquid phase dehydration of 1-indanol, employing one of these two zeolites as a catalyst would provide: 1) high yield in indene; 2) easy separation of product from solvent; 3) easy separation of the catalyst from the reaction medium. [ABSTRACT FROM AUTHOR]

2-(2-Phenyl-4 H -chromen-4-ylidene)-2 H -indene-1,3-diones were obtained in good to excellent yields by treatment of 2-hydroxychalcones and indane-1,3-dione in refluxing toluene in the presence of amberlyst-15 as catalyst in air. The reaction involving 2-hydroxychalcones and cyclopentane-1,3-dione under the same condition gave 2-(2-phenyl-4 H -chromen-4-ylidene)cyclopentane-1,3-diones along with 2,8-dioxabicyclo[3.3.1]nonanes, the relative amount of the products being dependent on the reaction time. Separate experiments have shown that the isolated 2,8-dioxabicyclo[3.3.1]nonanes are convertible to the other type of products under the applied reaction condition. [ABSTRACT FROM AUTHOR]

A novel FeCl3 mediated formal [2+2] cycloaddition/ring opening cascade of o-keto-cinnamates was developed for the synthesis of indenones. The reaction tolerates a broad range of functional groups, including bromide, chloride, amide, acid and ester groups. [ABSTRACT FROM AUTHOR]

( E)-2-[2-(1-Substituted ethylidene)hydrazinyl]-5-oxo-9b-hydroxy-5,9b-dihydroindeno[1,2- d][1,3]-thiazine-4-carbonitriles and ( E)-5-oxo-[( E)-(1-substituted ethylidene)hydrazinyl]-2,5-dihydroindeno[1,2- d][1,3]thiazine-4-carbonitriles have been obtained from the reaction of 2-(substituted ethylidene)hydrazinecarbothioamides with 2-(1,3-dioxo-2,3-dihydro-1 H-inden-2-ylidene)propanedinitrile ( 1) in ethyl acetate solution. However, ( Z)-6′-amino-1,3-dioxo-3′-substituted-2′-[( E)-(1-phenylethylidene)hydrazono]-1,2′,3,3′-tetrahydrospiro(indene-2,4′-[1,3]thiazine)-5′-carbonitriles were observed during the reaction of N-substituted-2-(1-phenylethylidene)hydrazinecarbothioamides with ( 1). The structure assignment of products has been confirmed on the basis of 1H-, 13C-NMR, and , as well as theoretical calculations. [ABSTRACT FROM AUTHOR]

Densely functionalized alkylidene indanes and indanones can be prepared efficiently in one pot, in high yields with good stereoselectivities (in some cases exclusively the Z-isomer), through a route involving phosphine-catalyzed Michael addition followed by palladium-catalyzed Heck cyclization. These transformations tolerate substrates bearing various substituents around the indane/indanone motif. Employing this technology, a concise formal synthesis of sulindac, a nonsteroidal anti-inflammatory drug, has been established. [ABSTRACT FROM AUTHOR]

An introduction is presented in which the editor discusses various reports within the issue on topics including application of a dual catalytic system in the Wittig reaction, gold acyl complex formation during indene synthesis, and palladium catalyzed arylation of allylamines.

Herein we report on the charge transport properties of spin-coated thin films of an n-type fullerene derivative, i.e. the indene-C60 bis-adduct (ICBA). In particular, the effects of annealing temperature and duration as well as surface functionalization are explored. Electron mobilities approaching 0.1 cm2 V−1 s−1 are reported. [ABSTRACT FROM AUTHOR]

Starting from (R)-citronellic acid and (R)-seudenol, the total synthesis of (+)-aplykurodinone-1, a highly degraded marine steroid, has been achieved in 11 steps and in 19% overall yield with excellent stereochemical control. In addition to the features such as an Ireland-Claisen rearrangement, an intramolecular carbonyl-ene cyclization, and an intramolecular Michael addition, the present synthetic strategy is accomplished without the use of protecting groups. [ABSTRACT FROM AUTHOR]

A simple and general microwave-assisted selenium oxidation has been developed for the synthesis of substituted ninhydrins from indan-1-ones in order to access to indeno[1,2- b ]indoles substituted on the A ring. This efficient and convenient oxidation, using selenium dioxide under microwave irradiations, afforded mono- and di-substituted ninhydrins in a single step reaction with good yields. [ABSTRACT FROM AUTHOR]

The TfOH-mediated reactions of 2,4-diaryl-1,1,1-trifluorobut-3-yn-2-oles (CF3-substituted diaryl propargyl alcohols) with arenes in CH2Cl2 afford 1,3-diaryl-1-CF3-indenes in yields up to 84%. This new process for synthesis of such CF3-indenes is complete at room temperature within one hour. The synthetic potential, scope, and limitations of this reaction were illustrated by more than 70 examples. The proposed reaction mechanism invokes the formation of highly reactive CF3-propargyl cation intermediates that can be trapped at the two mesomeric positions by the intermolecular nucleophilic attack of an arene partner with a subsequent intramolecular ring closure. [ABSTRACT FROM AUTHOR]

The article presents chemical equations of the article "Catalytic Enantioselective Synthesis of Indanes by a Cation-Directed 5-endo-Trig Cyclization" by C.P. Johnston and others, published in the periodical "Nature Chemistry" in 2015.

A golden moment: The development of targeted gold acyl complexes, which are generated from dialkynes via vinylidene intermediates, and can decarbonylate to form indenes by proto‐aurolysis is highlighted. [ABSTRACT FROM AUTHOR]

The article presents the chemical reactions for synthesis of indenes and benzosiloles involving diisobutylaluminum hydride-promoted cyclization of benzyl and phenylsilyl ethers bearing a 2-(trimethylsilyl) ethynyl group.

A graphical abstract of the article "The Diels-Alder Reactivity of 2-Vinylindenes: Synthesis of Functionalized Tetrahydrofluorenes" by C. M. Lavados et al. is presented.

The novel diazosulfonation reaction proceeds via addition of sulfonyl radicals to the enynal triple bond followed by 5-exo-trig carbocyclization/H-abstraction sequence to furnish unprecedented diazoindenyl sulfones. [ABSTRACT FROM AUTHOR]

A novel ruthenium complex HSRC is prepared and successfully applied for the synthesis of spiro carbocyclic indenes via a [3 + 2] annulation strategy. [ABSTRACT FROM AUTHOR]

A new chemo- and regioselective iodocarbocyclization of allenylarenes is presented. [ABSTRACT FROM AUTHOR]

Intramolecular Pd-catalyzed cyclization of various o-(alkynyl)styrenes includes bromopalladation/Heck cross-coupling/β-H elimination using oxygen as an oxidant affords 3-bromoindenes of type (II). [ABSTRACT FROM AUTHOR]