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Under acidic reaction conditions (TFA), deprotection of BocNR(OSO2R) reagents triggers intermolecular aminative cyclizations of alkenes equipped with pendant nucleophiles. The processes are predicated on a sequence of stereospecific intermolecular aza‐Prilezhaev aziridination followed by stereospecific SN2‐like opening by the pendant nucleophile. The method offers broad scope with respect to the nucleophile (N‐, O‐ or C‐based), alkene and cyclization mode, allowing the installation of two contiguous stereocenters under operationally simple conditions. [ABSTRACT FROM AUTHOR]

A rhodium(III)‐catalyzed oxidative cyclization of chalcones with internal alkynes is reported, generating biologically important 3,3‐disubstituted 1‐indanones along with reusable aromatic aldehydes. This transformation features unique (4+1) reaction mode, excellent regioselectivity in alkyne insertion, broad substrate scope, allows for the construction of quaternary carbon centers, and is scalable. Steric hindrance from substrate and ligand probably controls the chemoselectivity of this carbocyclization. Importantly, this discovery enables a practical two‐step protocol switching the overall reaction of acetophenones with internal alkynes from a (3+2) to a (4+1) annulation. [ABSTRACT FROM AUTHOR]

π‐Activation of alkynyl precursors possessing an endogenous carbon nucleophile is one of the imperative topics in homogeneous gold catalysis as it offers Csp3‐Csp2 and Csp2‐Csp2 linked carbocycles. However, the exo‐dig and endo‐dig cyclization modes unlocks the possibility of both small and large rings respectively, thereby losing regioselectivity. Nevertheless, several gold‐catalyzed carbocyclizations which permits one isomer by controlling or avoiding the formation of other went largely unnoticed. Hence, this review is an attempt to summarize such approaches reported from early 2000's to till date along with our viewpoint on contributing parameters for regioselectivity. This review covers only unimolecular reactions with classifications primarily based on the type of endogenous nucleophiles such as silyloxyenols, enamides/enamines, benzenoids, heteroaromatics and alkyls/alkenyls. From an application perspective, these reactions are significant in total synthesis and materials science. Therefore, those reactions that finds application in natural product synthesis and π‐functional materials are highlighted in appropriate places. [ABSTRACT FROM AUTHOR]

Gold‐catalyzed cyclizations of (2‐formylphenyl)prop‐2‐yn‐1‐yl acetates afford two distinct cyclization products. In the case of substrates bearing a alkyl or arylalkynyl group, 2‐carbonyl‐1H‐indene derivatives were obtained whereas substrates bearing an electron‐withdrawing alkynoate or alkynone group, distinct 4‐acetoxy‐3‐hydroxy‐2‐naphthoates were produced efficiently. Our mechanistic analysis indicates that H2O is not only a nucleophile but also a catalyst for both carbocyclizations. [ABSTRACT FROM AUTHOR]

This review focuses on the carbocyclization reactions of alkyne-containing substrates catalyzed by Brønsted acids. The electrophilic activation occurs either by direct protonation of the alkyne or by formation of an intermediate cation that further reacts with the alkyne to give a key vinyl cation intermediate. Specific focus is placed on the selectivity of the various methodologies described herein and on mechanistic rationales. 1 Introduction 2 Brønsted Acid Catalyzed Alkyne Carbocyclization Involving C(sp) Reaction Partners 2.1 Brønsted Acid Catalyzed Cyclization of Diynes 2.2 Brønsted Acid Catalyzed Cyclization of Allenynes 3 Brønsted Acid Catalyzed Alkyne Carbocyclization Involving C(sp2) Reaction Partners 3.1 Brønsted Acid Catalyzed Cycloisomerization of Enynes 3.1.1 Initial Protonation of the Alkene Function 3.1.2 Initial Protonation of the Alkyne Function 3.1.3 A Conia-Ene Reaction 3.2 Electrophile-Induced Carbocyclization Involving Other C(sp2)-Based Reaction Partners 3.2.1 Iminium Electrophiles 3.2.2 Oxonium Electrophiles 3.2.3 Isocyanate and Thioisocyanate Electrophiles 3.3 Brønsted Acid Catalyzed Cycloisomerization of Aryl-alkynes 3.3.1 Reactions Using Excess or Stoichiometric Amounts of Brønsted Acid 3.3.2 Reactions Using Substoichiometric Amounts of Brønsted Acid 3.3.3 Heteroatom-Substituted Alkynes 3.3.4 Enantioselective Brønsted Acid Catalyzed Cycloisomerization of Aryl-alkynes 4 Brønsted Acid Catalyzed Alkyne Carbocyclization Involving C(sp3) Reaction Partners: Alkyne-alkane Cycloisomerization 5 Conclusion and Outlook [ABSTRACT FROM AUTHOR]

An organoselenium‐enabled radical relay Azidation‐carbocyclization reaction for the preparation of azide‐substituted quinoline‐2,4‐diones was developed. A series of previously unknown structurally diverse azide‐ substituted quinoline‐2,4‐diones were obtained under metal‐free and room‐temperature conditions. The key features of this reaction are a broad substrate scope, amenability to gram‐scale synthesis, and easy product derivatization. Preliminary mechanistic studies support participation of an organoselenium species in a radical relay pathway. [ABSTRACT FROM AUTHOR]

A tandem Michael addition/carbocyclization of 3,4‐dimethoxyphenethyl maleimide with carbon and sulfur nucleophiles is accomplished via a relay catalysis using γ‐Al2O3/TfOH binary system. The X‐ray Photoelectron Spectroscopy (XPS) analysis of binary system indicates the presence of AlF3, AlO(OH) species. This approach provides an easy access to 2‐aryl or 2‐thio aryl pyrrolo[2,1‐a]isoquinolines in good yields in a tandem fashion. With suitable ratio of γ‐Al2O3/TfOH binary system, the Michael addition of N/C/S nucleophiles to N‐benzyl maleimide is also achieved. A key to the success of these reactions would be the generation of AlF3, AlO(OH) species from γ‐Al2O3 and TfOH, which might have delineated the disadvantageous background reactions usually displayed by a strong Brønsted acid such as TfOH. [ABSTRACT FROM AUTHOR]

[Display omitted] Herein, we report the synthesis of thiolated methylene oxindoles via palladium-catalyzed intramolecular decarbonylative carbocyclization of thioester tethered alkyne. This reaction tolerates various functional groups, affording the thiolated methylene oxindoles in moderate-to-good yields. [ABSTRACT FROM AUTHOR]

Imidazopyridinones and 7-azaoxindoles are two classes of heterocyclic compounds with only limited previous use in organic and medicinal chemistry. Various synthetic methods and routes have been evaluated to identify safe and robust chemistry to advanced imidazopyridinone building blocks and inhibitor structures. Preparation of the 7-azaoxindoles was challenged by instability of the core scaffold. Key to the successful isolation of the target structure was development of a mild Suzuki cross-coupling in non-aqueous media. The imidazopyridinones were potent inhibitors of the E. coli thymidylate monophosphate kinase, while the 7-azaoxindole showed low activity. The compounds were inactive in cell-based studies, indicating poor cell wall penetration. [ABSTRACT FROM AUTHOR]

Stereoselective carbocyclizations of vinyloxiranes were efficiently catalyzed by Lewis acids to provide cyclic homoallyl alcohols as single isomers. The choice of Lewis acid, B(C6F5)3 was crucial for the stereoselective transformation in the case of cis vinyloxiranes, whereas BF3∙OEt2 was proven to be an effective catalyst for trans substrates. The method was well implemented in the synthesis of seven‐membered rings and six‐membered rings with functional group tolerance. Utility of the resulting trans‐ and cis homoallyl alcohols was demonstrated to concisely build the tricyclic core of musellarin A and E. [ABSTRACT FROM AUTHOR]

The use of molecular oxygen in palladium‐catalyzed oxidation reactions is highly widespread in organic chemistry. However, the direct reoxidation of palladium by O2 is often kinetically unfavored, thus leading the deactivation of the palladium catalyst during the catalytic cycle. In the present work, we report a highly selective palladium‐catalyzed carbocyclization of bisallenes to seven‐membered heterocycles under atmospheric pressure of O2. The use of a homogenous hybrid catalyst (Co(salophen)‐HQ, HQ=hydroquinone) significantly promotes efficient electron transfer between the palladium catalyst and O2 through a low‐energy pathway. This aerobic oxidative transformation shows broad substrate scope and functional group compatibility and allowed the preparation of O‐containing seven‐membered rings in good yields in most cases. [ABSTRACT FROM AUTHOR]

Reviewed herein, the progress employing the assistance of a neighboring carbonyl group for alkyne functionalization reactions that are mediated by water. Proper arrangement of these transformations is synthetically worthwhile because it will allow chemists to design straightforward synthetic routes for the construction of complex architectures with perfect regio‐ and chemoselectivity. Researchers must understand the mechanism before aiming a new idea based on these types of transformations as they proceed through a different way in comparison to the strategies that employ carbonyl groups as a directing group for C−H functionalization reactions. In general, an oxygen transposition event occurs in the presence of an alkyne activator. In an aim to expose the molecular diversity that can now be accessed employing intramolecular carbonyl assistance, all the precedents are organized systematically for the first time and can be expected to serve as a comprehensive reference work. Therefore, the key arrangement of this review is schemes accompanied by a concise explanatory text describing both advantages and limitations along with the mechanism. Different transformations are ordered in sections according to the chemical structure of the assisted groups. The overall objective of this review is to promote the application of carbonyl‐assisted reactions beyond the methodologies dedicated to the regioselective synthesis of carbonyl derivatives and hence, serving it as a valuable reaction archetype in modern‐day research for the synthesis of carbo‐ and heterocycles. [ABSTRACT FROM AUTHOR]

This review examines current trends in the use of readily accessible acyclic enaminodiones in the synthesis of heterocyclic structures, including medicinal and natural compounds. Enaminodiones are latent tricarbonyl compounds, therefore their synthetic use exploits mainly their electrophilic properties. In addition, they can act as C-nucleophiles and participate in formal (4+2) cycloaddition reactions as ambiphilic reagents, as well as key intermediates in intramolecular cyclizations. The review analyzes the literature published in 2012–2019; the systematization is based on the structure of the formed heterocycle. The bibliography of the review includes 97 sources. [ABSTRACT FROM AUTHOR]

Here, a mild and general oxidative radical relay carbocyclization reaction with 2‐arylbenzoimidazoles and cyclic ethers is reported. This method provides an efficient access to a wide range of structurally diverse benzimidazo[2,1‐a]isoquinoline‐6(5H)‐ones under metal‐free conditions. The wide substrate scope, good functional group tolerance, and scale‐up operation of this method are expected to promote its potential applications in biotechnology and pharmacy. [ABSTRACT FROM AUTHOR]

In our pursuit of developing novel analogs of anthracyclines with enhanced antitumor efficacy and safety, we have designed a synthesis scheme for 4,11-dihydroxy-5,10-dioxocyclopenta[ b ]anthracene-2-carboxamides. These newly synthesized compounds exhibit remarkable antiproliferative potency against various mammalian tumor cell lines, including those expressing activated mechanisms of multidrug resistance. The structure of the diamine moiety in the carboxamide side chain emerges as a critical determinant for anticancer activity and interaction with key targets such as DNA, topoisomerase 1, and ROS induction. Notably, the introduced modification to the doxorubicin structure results in significantly increased lipophilicity, cellular uptake, and preferential distribution in lysosomes. Consequently, while maintaining an impact on anthracyclines targets, these novel derivatives also demonstrate the potential to induce cytotoxicity through pathways associated with lysosomes. In summary, derivatives of cyclic diamines, particularly 3-aminopyrrolidine, can be considered a superior choice compared to aminosugars for incorporation into natural and semi-synthetic anthracyclines or new anthraquinone derivatives, aiming to circumvent efflux-mediated drug resistance. [Display omitted] • • New cyclopentane-fused anthraquinone derivatives have been designed and synthesized. • • Selected compounds have strong antiproliferative potency and circumvent Pgp-mediated efflux. • • Derivative 9 has increased lipophilicity and faster cellular uptake than doxorubicin. • • Terminal amino group in the side chain is crucial for DNA binding and Top1 inhibition. [ABSTRACT FROM AUTHOR]

We have developed a Hosomi‐Sakurai type carbocyclization of homoallylic silyl ethers in reaction with silyl nucleophiles, catalyzed by Lewis acidic silylium salt. It offers cyclopropane and cyclobutane products with high efficiency and selectivity. A range of silyl nucleophiles could be engaged in this transformation to give small‐sized carbocycles incorporating allyl, allenyl, carbonyl, indole or thioether groups. Diastereoselectivity in the cyclobutane formation was observed to be dependent on the steric bulkiness of incoming nucleophiles. [ABSTRACT FROM AUTHOR]

The development of a nickel-catalyzed C–H alkylation of aromatic substrates with unactivated alkyl halides is described. This carbocyclization facilitates the synthesis of diverse fused ring systems from simple aromatic substrates and is an attractive alternative to traditional polar or radical-mediated ring formations. The present system uses unactivated primary and secondary alkyl bromides and chlorides, while avoiding the use of precious palladium catalysts and more reactive alkyl halides commonly used in related C–H alkylations. Image 1 [ABSTRACT FROM AUTHOR]

Density functional theory calculations were performed to reveal the mechanisms of Pd‐catalyzed cascade carbocyclization‐borylation and arylation reactions. The computational results indicate that the reactions start with allylic C−H cleavage through concerted metalation‐deprotonation and an intramolecular exo‐type allene insertion to form a six‐membered carbocycle intermediate. The regioselectivity of insertion could be explained by frontier molecular orbital theory and natural population analysis calculation. In the absence of extra nucleophiles, η1/η3‐isomerization followed by acetate‐assisted deprotonation could yield polyene product. When nucleophile was added to the reaction system, transmetalation and subsequent reductive elimination could give the exo‐substituted triene as major product. Meanwhile, η1/η3‐isomerization, transmetalation, and reductive elimination could afford the endo‐isomer as side product. The regioselectivity of further functionalization is controlled by the competition of transmetalation and η1/η3‐isomerization. The computational results show that both exo‐ and endo‐boronation product could be observed when bis(pinacolato)diboron is added as nucleophile. However, only exo‐phenylation product is observed when phenylboronic acid is used as nucleophile because of the high free‐energy barrier for reductive elimination from aryl η3‐allylic palladium. Show me the way: DFT calculations were employed to study the mechanism and origin of regioselectivity of cascade carbocyclization‐functionalization reactions. [ABSTRACT FROM AUTHOR]

Easy and effective preparation of new 1H-pyrrolizine carboxylates was achieved with high efficiency via KHMDS-induced carbocyclization of N-alkynyl proline carboxylates under substantially mild conditions. Meanwhile, some trans-diiodoallylic N-proline carboxylates were obtained from N-propargyl proline carboxylates using molecular I2 with or without KHMDS. This method is quite feasible in terms of practical and quick access to the pyrrolizines and their derivatives over the formation of carbanions. [ABSTRACT FROM AUTHOR]

Sulfur centered radicals are widely employed in chemical synthesis, in particular for alkene and alkyne hydrothiolation towards thioether bioconjugates. The steadfast radical chain process that enables efficient hydrothiolation has been explored in the context of cascade reactions to furnish complex molecular architectures. The use of thiyl radicals offers a much cheaper and less toxic alternative to the archetypal organotin-based radical methods. This review outlines the development of thiyl radicals as reactive intermediates for initiating carbocyclization cascades. Key developments in cascade cyclization methodology are presented and applications for natural product synthesis are discussed. The review provides a chronological account of the field, beginning in the early seventies up to very recent examples; a span of almost 50 years.

Herein, we communicate a selective and efficient protocol for oxidative arylating carbocyclization of enallenynes using O2 as the oxidant. The key to success for this aerobic transformation is the application of a specific electron transfer mediator (ETM), a bifunctional catalyst consisting of a metal‐macrocycle and quinone moieties. This catalyst significantly facilitates the reoxidation of Pd0 to PdII under atmospheric pressure of O2. Diverse functionalized enallenynes react with aryl boronic acids to afford the corresponding cyclic tetraenes in moderate to good yields. Co catalyst as co‐catalyst: A PdII‐catalyzed oxidative carbocyclization of the rational designed enallenynes using molecular oxygen is reported. By applying a bifunctional catalyst (Co(salophen)‐HQ) as an efficient electron transfer mediator, enallenynes are effectively arylated to the corresponding six‐membered carbocycles in good yields. [ABSTRACT FROM AUTHOR]

The reaction of furfural with secondary amines and isopropyl cyanoacetate gave previously unkown diisopropyl esters of 8-(dialkylamino)-6-oxo-3-(2-furyl)-2,4-dicyanobicyclo- [3.2.1]octane-2,4-dicarboxylic acid. [ABSTRACT FROM AUTHOR]

Lewis bases were evaluated as catalysts for halocarbocyclization reactions of alkynylstyrenes and a cinnamylaniline derivative. Phosphines and phosphorus chalcogenides exhibited high activity for the conversion of alkynylstyrenes in the presence of N-halosuccinimides with up to a 30-fold increase of the initial reaction rate with respect to the background reaction. Phosphorus sulfides and selenides showed the best catalytic activity for the iodocarbocyclization of a cinnamylaniline derivative in the presence of diiodohydantoin. An asymmetric variant of the iodocarbocyclization reaction of an alkynylstyrene using a chiral phosphorus selenide resulted in a modest enantioselectivity. [ABSTRACT FROM AUTHOR]

Abstract: A new sulfinate salt‐mediated radical relay for the completion of C(sp3)−H bond indenylation of cyclic ethers with readily available 2‐alkynylbenzonitriles by combining silver/tert‐butyl peroxide (TBHP) was established, providing a wide range of 3‐alkylated 1‐indenones with generally good yields. Interestingly, the current reaction system can tolerate an S‐centered radical and a C‐centered radical in one pot, in which the S‐centered radical promotes the formation of the C‐centered radical to induce a radical cascade without disturbing the reaction process. A reaction mechanism is also proposed based on control experiments. [ABSTRACT FROM AUTHOR]

Abstract: The organoborane‐catalyzed reductive carbocyclization of homoallylic alcohols has been developed by using hydrosilanes as reducing reagents to provide a range of 1,2‐disubstituted arylcyclobutanes. The reaction proceeds in a cis‐selective manner with high efficiency under mild conditions. Mechanistic studies, including deuterium scrambling and Hammett studies, and DFT calculations, suggest a dual ring‐closing pathway. [ABSTRACT FROM AUTHOR]

oxobicyclo[3.2.1]octane-2,4-dicarboxylates. The structures of the products were confirmed by NMR and X-ray analysis.

The reaction of cyclopentenylsilane derivatives with n -Bu 4 NF in THF at rt was shown to proceed with the regio- and stereoselective formation of the corresponding bicyclo[3.1.0]hex-2-ene derivatives. [ABSTRACT FROM AUTHOR]

A mild and convenient synthetic method for oxindoles and α-arylacylamides bearing an all carbon quaternary stereocenter from the readily available α-bromo-N-arylacylamides has been developed. This Cu(acac)2/Phen-promoted radical cyclization reaction, via the intramolecular radical cyclization onto the aryl moiety, can proceed in two different routes depending on the substituents on the nitrogen atom. In this transformation, oxindoles and α-arylacylamides were formed in high chemoselectivity. A variety of useful functional groups such as methoxy, fluoro, chloro, bromo, methoxycarbonyl, and cyano are compatible with the reaction conditions. The use of inexpensive, readily available Cu(acac)2 and Phen makes this protocol very efficient and practical. [ABSTRACT FROM AUTHOR]

A highly selective palladium-catalyzed oxidative carbonylation/carbocyclization/alkoxycarbonylation of enallenols to afford spirolactones bearing an all-carbon quaternary center was developed. This transformation involves the overall formation of three C−C bonds and one C−O bond through a cascade insertion of carbon monoxide (CO), an olefin, and CO. Preliminary experiments on chiral anion-induced enantioselective carbonylation/carbocyclization of enallenols afforded spirolactones with moderate enantioselectivity. [ABSTRACT FROM AUTHOR]

The rapid synthesis of bicyclo[m.n.1]alkanone cores possessing quaternary carbon centers adjacent to a bridged ketone represents a significant synthetic challenge. This type of architectural feature is embedded in various complex biologically active compounds such as hyperforin and garsubellin A. Herein, we report a highly diastereoselective one-pot Diels–Alder reaction/Au(I)-catalyzed carbocyclization to generate bicyclo[3.3.1]alkanones in yields ranging from 48–93%.

An olefin-assisted palladium-catalyzed oxidative carbocyclization-alkoxycarbonylation of bisallenes to afford seven-membered carbocycles has been established. This dehydrogenative coupling reaction showed excellent substrate scope and functional group compatibility. The reaction exhibited high chemo- and regioselectivity, and ester 3 was the only product obtained. The olefin unit has been proven to be indispensable during the reaction. Moreover, intramolecular oxidative coupling suggests that the reaction proceeds via a (π-allyl)palladium intermediate. [ABSTRACT FROM AUTHOR]

A synthetic method for highly functionalized quinolin-2(1H)-ones has been developed. The copper(II) chloride-catalyzed aerobic oxidative carbocyclization reactions of α-substituted N-[2-(phenyl-ethynyl)phenyl]acetamides, via the Conia-ene-type intramolecular carbocupration onto the alkynyl moiety, produced 3,4-difunctionalized quinolin-2(1H)-ones. In the absence of copper(II) chloride, these α-substituted acetamides undergo base-promoted nucleophilic 6-exo-dig carbocyclization to generate 3-functionalized quinolin-2(1H)-ones. Several useful functional groups including benzoyl, alkanoyl, diethoxyphosporyl, cyano, and methoxycarbonyl groups are compatible with the reaction conditions. α-Substituted N-(2-ethynylphenyl)acetamides bearing a terminal C≡C bond could also be used to generate the corresponding 4-methyl-substituted quinolin-2(1H)-ones smoothly. [ABSTRACT FROM AUTHOR]

Tin triflate-promoted one-pot intramolecular annulation of α-geranyl or α-farnesyl β-ketosulfones 3 – 4 affords the respective bicyclic or tricyclic sulfonyl dihydropyrans 5 – 6 in moderate to good yields via a cascade cation-olefin-carbonyl carbocyclization process. The starting materials 3 and 4 were obtained by K 2 CO 3 -mediated α-geranylation or α-farnesylation of β-ketosulfones 1 with bromides 2a or 2b . The structures of the key products were confirmed by X-ray crystallography. [ABSTRACT FROM AUTHOR]

The use of enaminones as effective synthons for a directed C−H functionalization is reported. Proof-of-concept protocols have been developed for the RhIII-catalyzed synthesis of naphthalenes, based on the coupling of enaminones with either alkynes or α-diazo-β-ketoesters. Two inherently reactive functionalities (hydroxy and aldehyde groups) are integrated into the newly formed cyclic framework and a broad range of substituents are tolerated, rendering target products readily available for further elaboration. [ABSTRACT FROM AUTHOR]

We report a new protocol for the annulative difunctionalization of acetylenes via tandem carbocyclization-coupling of ε-acetylenic β-ketoesters with aryl and heteroaryl bromides and chlorides catalyzed by the palladium species derived from an air- and moisture-stable palladacyclic precatalyst. In the tandem process, the palladium complex combines appropriate carbophilic Lewis acidity and redox activity to catalyze two mechanistically distinct reactions - nucleophilic addition of the enolate to unactivated alkyne, followed by CC coupling. We found that a broad range of electronically varied aryl and heteroaryl bromides and chlorides underwent this reaction with various ε-acetylenic β-ketoesters, providing corresponding substituted vinylidenecyclopentanes in high yield with excellent functional group tolerance. [ABSTRACT FROM AUTHOR]

The efficient gold-catalyzed cyclization reactions of alkynyl silyl enol ethers were successfully applied to the preparation of bicyclo[3.2.1]octanone derivatives. Accordingly, after optimization of the gold catalytic system, several bicyclic α,β-unsaturated keto adducts were synthesized in good to excellent yields. The process followed a major 5- exo cyclization via an anti addition of the silyl enol ether to the π-activated intermediate, which was demonstrated by a deuterium incorporation experiment. A 6- endo cyclization process was observed for a silyl enol ether bearing an electron-donating aromatic group. [ABSTRACT FROM AUTHOR]

Palladium(II) catalyzed carboannulation reaction of internal alkynes with nitrostyrenes to afford 2,3-disubstituted indenones is reported. The annulation reaction proceeds through transmetalation of Pd(II) with aldehydes generated from the nitrostyrene (C–H activation) and insertion of the alkynes, followed by cyclization via intramolecular nucleophilic addition of intermediate organopalladium(II) species. This reaction proceeded in moderate to good yields and with high regioselectivity. Electron-rich nitrostyrenes were transformed to the corresponding aldehydes in high yields without addition of any peroxide reagent. [ABSTRACT FROM AUTHOR]

Indanes and indenes are among the most important carbocycles. Many indane and indene derivatives have shown important pharmacological activities, and the indane and indene nuclei are structural motifs present in several natural products of biological relevance. In spite of their importance, only a few reviews on their preparation methods have appeared so far in the literature, the most recent ones being published about ten years ago. The present Review is aimed at filling this gap, presenting some of the most important and innovative approaches to indanes and indenes that have been published in the course of the last ten years (coverage: from 2005 to May, 2015). [ABSTRACT FROM AUTHOR]

Iridium(III) and rhodium(III) complexes can catalyze the carbocyclization between 2-phenylimidazo[1,2- a]pyridine and α-diazo esters. The reaction occurs via CH activation and dialkylation of the arene followed by intramolecular nucleophilic substitution. Iridium(III) and rhodium(III) catalysis offer complementary scopes with respect to the α-diazo esters. [ABSTRACT FROM AUTHOR]

[Display omitted] Over recent years, coinage metal alkenyl carbene intermediates have attracted significant attention as three-carbon synthons. Catalytically generated from a variety of readily available precursors, these intermediates can engage in a wide number of carbo- and heterocyclizations providing efficient routes to carbo- and heterocycles otherwise difficult to achieve. In this Review, we aim to highlight the most relevant advances in this exciting topic. [ABSTRACT FROM AUTHOR]

An enantioselective oxidative carbocyclization-borylation of enallenes that is catalyzed by palladium(II) and a Brønsted acid was developed. Biphenol-type chiral phosphoric acids were superior co-catalysts for inducing the enantioselective cyclization. A number of chiral borylated carbocycles were synthesized in high enantiomeric excess. [ABSTRACT FROM AUTHOR]

A post-Ugi gold-catalyzed regioselective intramolecular carbocyclization strategy is reported. A better cationic gold system, compared to our previous report, has been optimized and utilized. The method presented exhibits excellent functional group compatibility including bulky substitutions on alkynes and allows the direct access to indoloazepinones and indoloazocinones in good to excellent yields. [ABSTRACT FROM AUTHOR]

We have developed a novel synthetic method to furnish spiro[4.5]cyclohexadienones using an gold-catalyzed carbocyclization of phenols with a terminal alkyne via an intramolecular ipso-Friedel-Crafts alkenylation. Using 2-5 mol% of gold catalyst, 1 equiv. of methanesulfonic acid, and 1 equiv. of 2,6-di- tert-butylpyridine, a variety of spiro[4.5]cyclohexadienone derivatives with an exo-cyclic olefin unit was obtained in good to excellent yields. The divergent synthesis of dihydronaphthalene derivatives was also examined based on the newly developed gold catalysis. [ABSTRACT FROM AUTHOR]

A highly efficient oxidative carbocyclization-carbonylation reaction cascade of allenynes and enallenes has been developed using a PdII salt in low catalytic amounts under ambient temperature and pressure (1 atm of carbon monoxide). The use of DMSO as an additive was found to be important for an efficient reaction. A wide range of alcohols as trapping reagents were used to give the corresponding esters in good yields. [ABSTRACT FROM AUTHOR]

The isolation and characterization of a rhodacycle intermediate implicated in rhodium-catalyzed reactions of alkylidenecyclopropanes (ACPs) is described. The structure of the metallacycle was unambiguously determined by X-ray crystallography and is catalytically competent in the rhodium-catalyzed carbocyclization and ene-cycloisomerization reactions of ACPs. This work represents a rare example of the isolation of a metallacycle in a metal-catalyzed higher-order carbocyclization reaction and thereby provides important insight into the ligand requirements for the insertion of π-components. Furthermore, it serves as a convenient synthon for the development of challenging higher-order carbocyclization reactions, as exemplified by the reaction with an activated allene. [ABSTRACT FROM AUTHOR]