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A base-promoted domino benzannulation reaction of 2,3-dibromoindenone with acyclic 1,3-dicarbonyls resulted in an efficient synthetic protocol for a series of novel polycyclic indeno[1,2-a]fluorenes. The reaction proceeds via the two sequential addition-elimination reactions of nucleophilic species generated from the 1,3-dicarbonyls under basic conditions, serendipitously leading to the benzannulation with two molecules of 2,3-dibromoindenone. The second addition-elimination occurs on the initially formed adduct of 1,3-dicarbonyl with 2,3-dibromoindenone, setting the stage for further intramolecular cyclization and aromatization. Interestingly, unsymmetrical 1,3-dicarbonyls furnished a single regioisomer. The origin of the regioselectivity and plausible mechanism is discussed. [ABSTRACT FROM AUTHOR]

A one-pot three-component synthesis of substituted meta-hetarylanilines from heterocycle-substituted 1,3-diketones has been developed. The electron-withdrawing power of the heterocyclic substituent (which can be estimated on the basis of calculated Hammett constants) in the 1,3-diketone plays a pivotal role in the studied reaction. The series of meta-hetarylanilines prepared (21–85% isolated yield) demonstrates the synthetic utility of the developed method.

An efficient methodology for the synthesis of highly diverse 4-aminoquinoline derivatives from activated alkynes and 2-aminobenzonitriles mediated by Lewis acid is described. The reaction proceeds via sequential aza-Michael addition/intramolecular annulation to afford highly substituted 4-aminoquinolines in good yields. The reaction is operationally simple and has high atom-economy with broad substrate scope. The post synthetic application of the reaction provides 4 H -benzo[ de ][1,6]naphthyridines. [ABSTRACT FROM AUTHOR]

We present the inaugural synthesis of a chiral teropyrene achieved through a four‐fold alkyne benzannulation catalyzed by InCl3, resulting in good yields. The product underwent thorough characterization using FT‐Raman and FT‐IR spectroscopies, demonstrating a close agreement with calculated spectra. X‐ray crystallographic analysis unveiled a notable twist in the molecule's backbone, with an end‐to‐end twist angle of 51°, consistent with computational predictions. Experimentally determined enantiomeric inversion barriers revealed a significant energy barrier of 23 kcal/mol, facilitating the isolation of enantiomers for analysis by circular dichroism (CD) and circularly polarized luminescence (CPL) spectroscopies. These findings mark significant strides in the synthesis and characterization of chiral teropyrenes, offering insights into their structural and spectroscopic properties. [ABSTRACT FROM AUTHOR]

We report the synthesis of a longitudinally helical molecular nanocarbon, hexabenzoheptacene (HBH), along with its dimethylated derivative (HBH‐Me), which are composed of six benzene rings periodically benzannulated to both zigzag edges of a heptacene core. This benzannulation pattern endows the resulting nanocarbons with a helical heptacene core and local aromaticity, imparting enhanced solubility and stability to the system. The chiral HBH‐Me adopts a more highly twisted conformation with an end‐to‐end twist angle of 95°, enabling the separation of the enantiomers. Both HBH and HBH‐Me can be facilely oxidized into their corresponding dications, which exhibit enhanced planarity and aromaticity upon loss of electrons. Notably, both longitudinally helical nanocarbons readily promote solid state packing into two‐dimensional (2D) arrangement. Single‐crystal microbelts of HBH‐Me show hole mobility up to 0.62 cm2 V−1 s−1, illustrating the promising potential of these longitudinally helical molecules for organic electronic devices. [ABSTRACT FROM AUTHOR]

One‐pot access to sulfonyl 2,3‐diarylnaphthalenes was developed via tBuOK‐mediated (4+2) benzannulation of o‐bis‐sulfonylmethyl arenes, employing diverse diarylacetylenes. A plausible mechanism is proposed and discussed. The advantages of the system include the use of inexpensive reagents, wide substrate scope, and mild reaction conditions. The synthetic route allows for the formation of two carbon–carbon double bonds (C=C). [ABSTRACT FROM AUTHOR]

An assorted set of sulfonyl arenes such as β‐naphthylamines, β‐naphthols, phenols and naphthalenes could be accessed in a divergent manner by base‐mediated annulation of sulfonyl enynals. The strategy is extended to the synthesis of heterocycles such as carbazole, quinoline and benzothiophene. Benzannulation is demonstrated on derivatives of natural steroids like estrone and cholesterol. [ABSTRACT FROM AUTHOR]

Palladium-mediated oxidative spirocyclization of 1,1-diacyl-2-vinylcyclopropanes afforded a small series of benzannulated 6,5- and 5,5-spiroketals. The rapid construction of these scaffolds proceeded in moderate to good yield (27-63%). However, efforts to thoroughly examine scope were hampered by both poor diastereoselectivity and, in the case of the 5,5-benzannulated spiroketal series, access to the requisite 1,3-dicarbonyl starting materials. [ABSTRACT FROM AUTHOR]

The DBU‐catalyzed benzylation of 1H‐benzotriazole amides with methyl coumalate is demonstrated for the synthesis of stilbenes and biaryl derivatives. The transformation involves the base‐catalyzed Michael addition of methyl coumalate to the 6π‐electrocyclic ring opening decarboxylation aromatization. Furthermore, the novel 2‐phenylnaphthalene derivatives showed potent anti‐proliferative and anti‐invasive activities against H1299 cells. [ABSTRACT FROM AUTHOR]

A one‐pot synthesis method for functionalized bis‐sulfonyl dibenzofurans was developed under an air atmosphere using potassium carbonate‐mediated benzannulation of diversified α‐sulfonyl o‐hydroxyacetophenones with 1,4‐dichloro‐2‐butyne. A plausible mechanism was proposed and discussed. This method provides intermolecular double α‐propargylation, sulfonyl migration, and intramolecular ring‐closure via the formation of one carbon‐oxygen single (C−O) bond, one carbon‐sulfur single (C−S) bond, and two carbon‐carbon (C=C) double bonds. [ABSTRACT FROM AUTHOR]

Divergent and enantiospecific total syntheses of the indolosesquiterpenoids xiamycins A, C, F, H and oridamycin A have been accomplished. The syntheses, which commence from (R)-carvone, employ a key photoinduced benzannulation sequence to forge the carbazole moiety characteristic of these natural products. Late-stage diversification from a common intermediate enabled the first syntheses of xiamycins C and F, and an unexpected one-pot oxidative decarboxylation, which may prove general, led to xiamycin H. All synthetic intermediates and the natural products were tested for anti-fungal activity. Xiamycin H emerged as an inhibitor of three agriculturally relevant fungal pathogens.

Expanded helicenes are expected to show enhanced chiroptical properties as compared to the classical helicenes but the synthesis is very challenging. Herein, we report the facile synthesis of a series of expanded helicenes Hn (n=1–4) containing 11, 19, 27 and 35 cata‐fused benzene rings through Suzuki coupling‐based oligomerization followed by Bi(OTf)3‐mediated regioselective cyclization of vinyl ethers. Their structures were determined by X‐ray crystallographic analysis. Enantiopure H2, H3, and H4 can be isolated by chiral HPLC and they all exhibit strong chiroptical responses with high absorption dissymmetry factor (|gabs|) values (0.020 for H2, 0.021 for H3, and 0.021–0.024 for H4). [ABSTRACT FROM AUTHOR]

Two catalytic benzannulation/1,4-addition cascades of available enynones with indoles or tetronic acid-derived enamino lactones as C-nucleophiles are reported, producing 53 examples of heterocycle-incorporating diarylmethanes with moderate to excellent yields. The combination of AgOTf and Sc(OTf)3 permits bimetallic synergistic catalysis of the reaction of enynones with indoles to access 35 triarylmethanes in generally good yields with ortho -naphthoquinone methides, generated in situ, as the key intermediates. Exchanging indoles for tetronic acid-derived enamino lactones resulted in 18 diarylmethanes by the Ag-catalyzed benzannulation/1,4-addition cascade. Both reactions are advantageous for their high atom utilization and mild reaction conditions, providing intriguing complementary approaches for the direct syntheses of new heterocycle-containing diarylmethanes. [ABSTRACT FROM AUTHOR]

The extended π-conjugated compounds 1 – 8 were synthesized by the benzannulation of the corresponding alkyne derivatives followed by Pd-catalyzed intramolecular cyclization. For the Pd-catalyzed intramolecular cyclization, microwave irradiation reduced the amount of the Pd catalyst and the reaction time. Moreover, this protocol can be achieved to prepare the extended and twisted π-conjugated molecule 19 , having anthracene, helicene, and picene skeletons. [Display omitted] • Synthesis of extended PHAs in a short step by benzannulation and intramolecular cyclization. • Improvement of reaction conditions of Pd-catalyzed C–H arylation by microwave irradiation. • Reaction mechanism of Pd-catalyzed C–H arylation depending on the substrate. • Applicable to extended and twisted π-conjugated molecule. [ABSTRACT FROM AUTHOR]

Bromotrimethylsilane‐promoted benzannulation of o‐alkynylbenzaldehydes and alkynes to yield 1‐naphthyl aryl ketones is reported. The reaction conditions are mild, metal‐free, and do not require pretreatment/protection of the substrates. We found that aryl propargyl alcohols were very effective substrates for this reaction, compared with other alkynes. Studies on the reaction scope, monitoring the reaction progress by 1H NMR, and theoretical calculations suggest that isochromenylium (benzopyrilium) ion is the key reaction intermediate. [ABSTRACT FROM AUTHOR]

The development of a Lewis acid-catalyzed, intramolecular ring-opening benzannulation of 5-(indolyl)2,3-dihydrofuran acetals is described. The resulting 1-hydroxycarbazole-2-carboxylates are formed in up to 90% yield in 1 h. The dihydrofuran acetals are readily accessed from the reactions of enol ethers and α-diazo-β-indolyl-β-ketoesters. To highlight the method's synthetic utility, a formal total synthesis of murrayafoline A, a bioactive carbazole-containing natural product, was undertaken. [ABSTRACT FROM AUTHOR]

Benzannulation and N‐annulation of β‐ketoenamines by the in‐situ generated methyl(methylene)sulfonium ion from the reaction of dimethyl sulfoxide (DMSO) and 1,2‐dibromoethane (DBE) was achieved. The β‐ketoenamines underwent N‐annulation to pyridine derivatives, while the N‐alkylated enamines were benzannulated to afford substituted anilines. The utility of the intermediate methyl(methylene)sulfonium ion was further extended for synthesizing methylene‐bridged bis‐1,3‐dicarbonyl compounds. [ABSTRACT FROM AUTHOR]

A mild and transition‐metal‐free one‐pot strategy is established to prepare polysubstituted naphthalene and phenanthrene derivatives from methyl enol ethers (MEE) with alkynes. Significantly, this protocol is promoted by boron trifluoride diethyl etherate (BF3⋅Et2O) at room temperature. A wide variety of diversely functionalized naphthalene and phenanthrene derivatives were obtained in good to excellent yields. A plausible mechanism involving a spiro quinonoid intermediate is proposed. Due to fluorescent nature of naphthalene, selected compounds were screened for the solvatochromism study. Notably, positive solvatochromism effect was observed in the case of nitro‐substituted naphthalene derivative (3 h) with respect to different polarity of solvents. [ABSTRACT FROM AUTHOR]

A mild and efficient synthesis of a broad scope of substituted naphtho[1,2‐a]pyrene derivatives was accomplished in good yields using an InCl3/AgNTf2‐mediated two‐fold alkyne benzannulation reaction. HPLC enantiomeric separation was achieved and the interconversion barriers have been determined. The ECD spectra of two derivatives were recorded and interpreted through TD‐DFT calculations. Raman spectra were also recorded and predicted through DFT calculations. [ABSTRACT FROM AUTHOR]

Chromene‐fused heterocyclic compounds have shown fascinating biological and physiochemical properties and thus, the design and development of chromene‐fused heterocyclic molecules is of significant interest in the field of synthetic organic chemistry. We report an innovative ligand‐ and additive‐free synthetic approach of 4‐(phenylethynyl)‐2H‐chromene‐3‐carbaldehyde with phenylacetylenes has been described through sequential chlorination, benzannulation, benzylic sp3 C−H bond functionalization, and ether oxidation for the formation of chloro‐substituted‐9‐phenyl‐6H‐benzo[c]chromen‐6‐ones with readily available chemicals under one‐pot, base‐free conditions using CuCl2 as sustainable catalyst. In this regioselective approach, we defined a reasonably longer cascade, which reveals the multiple role of chlorine as chlorine supplier, Lewis acid catalyst and oxidation rate promoter that tolerates a broad substrate scope and allows good product yields. The authenticated mechanism proceeds in a cascading fashion through the formation of multiple bonds. [ABSTRACT FROM AUTHOR]

We have synthesized and characterized a benzannulated analog, bBDPA, of the well-known stable radical bis(diphenylene)phenylallyl (BDPA). Benzannulation gives rise to fluorescence in the closed-shell precursor molecule bBDPAH, but luminescence is quenched in the radical species. We detail the synthesis, characterization by absorption, emission, and EPR spectroscopy, and examine the molecular orbital landscape dictating the properties of the radical. We find that benzannulation alters the energy of the radical’s frontier molecular orbitals differently than in luminescent radicals brought about by incorporation of heteroatoms into their frameworks.

This paper reports the total synthesis of the serrulatane natural products (1R,4S,11S)-8,19-dihydroxyserrulat-14-ene (5.0% yield) and (1R,4S,11S)-8-hydroxyserrulat-14-en-19-oic acid (3.8% yield) via a silver-catalyzed 6-endo-dig benzannulation of an (-)-isopulegol derived ene-yne-ol in 17 steps. Analysis of the spectroscopic data as well as the specific rotations allowed for the confirmation of the stereochemistry at C1, C4 and C11 as (1R,4S,11S) for both natural products 8,19-dihydroxyserrulat-14-ene and 8-hydroxyserrulat-14-en-19-oic acid that were reported from the Australian desert plant, Eremophila neglecta. [ABSTRACT FROM AUTHOR]

This paper reports the development of a silver-catalyzed 6-endo-dig cyclisation of 5-alkoxy-1,5-enynes enabling benzannulation of (-)-menthone with construction of the calamenene skeleton as a single isomer. The total syntheses of (7S,10R)-2,15-dihydroxycalamenene (6 steps, 39.6%), (7S,10R)-2-hydroxy-15-calamenenal (7 steps, 10.7%) and (7S,10R)-2-Hydroxy-15-calamenenoic acid (9 steps, 33.6%) were achieved from (-)-menthone via a common intermediate. Analysis of the spectroscopic data as well as the specific rotations allowed for confirmation of the stereochemistry at C1 and C4 of the natural compounds isolated from Tarenna madagascariensis as (7R,10S)-2,15-dihydroxycalamenene and (7R,10S)-2-hydroxy-15-calamenenal, and the carboxylic acid isolated from Alpinia oxymitra was confirmed as (7S,10R)-2-hydroxy-15-calamenenoic acid. [ABSTRACT FROM AUTHOR]

A benzannulation strategy involving activation of two C–H bonds of five-membered heteroarenes was developed. Readily available furans and pyrroles stabilized by synthetically useful electron-withdrawing groups underwent Pd-catalyzed 1:2 annulation reactions with diaryl alkynes. A variety of functional groups, including ester, amide, ketone, aldehyde, and nitrile, on the heterocyclic cores were tolerated in the Pd-catalyzed oxidative reactions. In these reactions, the combination of 2,2-dimethylbutyric acid and its conjugate base facilitated metalation at the heteroaromatic rings and reoxidation of the Pd(0) species using oxygen as the terminal oxidant. This strategy provides fluorescent -benzofuran and indole derivatives and is expected to allow for further development of functionalized polycyclic heteroaromatic compounds. [ABSTRACT FROM AUTHOR]

Aromatic compounds are ubiquitous in pharmaceutical agents and other functional materials. Therefore, synthetic methods to construct highly functionalized aromatic frameworks have attracted considerable attention, especially when utilizing acyclic precursors instead of pre‐existing benzenoid cores. A plethora of methods exist in the literature for the construction of substituted aromatic products by using transition metal catalysis and base‐promoted benzannulation reactions starting from acyclic precursors. In recent years, organocatalytic approaches such as N‐heterocyclic carbene catalysis have emerged as effective tools for the efficient and regioselective construction of highly functionalized aryl rings under metal‐free and mild reaction conditions. The fundamental objective of this minireview is to highlight the synthetic potential of NHC‐catalyzed benzannulations for the generation of aromatic rings with complex substitution patterns and to discuss these reactions from the perspective of their mechanistic design. [ABSTRACT FROM AUTHOR]

A novel and straightforward strategy for the construction of versatile densely functionalized aryl α‐keto esters is disclosed through a one‐pot and efficient [4+2] benzannulation reaction of α‐cyano‐β‐methylenones and ynediones, which could be synthesized easily from the corresponding starting materials. This protocol features high yield, mild metal‐free reaction condition, high atom economy, high functional‐group tolerance, easy handing and gram‐scale synthesis. [ABSTRACT FROM AUTHOR]

The robustness of phosphine catalysis enabling the domino benzannulation reactions of allenoates with enamines is described. A broad array of substituted terephthalates were delivered under simple and practical reaction conditions. Furthermore, the reaction could be carried out on a gram scale with higher yield, and various conversions of the terephthalate products demonstrate the versatility of this transformation. [ABSTRACT FROM AUTHOR]

Ruthenium‐catalyzed butadiene‐mediated benzannulation enabled the first synthesis of 3,10‐(di‐tert‐butyl)rubicene and its N‐doped derivatives as well as preliminary studies on their photophysical properties. Unlike the parent rubicene and 3,10‐(di‐tert‐butyl)rubicene, which adopt classical herringbone‐type packing motifs in the solid state, the N‐doped congener 7 b displayed columnar packing with an alternating co‐facial arrangement of aromatic and heteroaromatic substructures. [ABSTRACT FROM AUTHOR]

Owing to the importance of arene moieties in organic chemistry, methods for arene construction attract great attention. Besides the traditional substitution strategy from pre-existing arenes, the straightforward formation of arene cores can also provide significant shortcuts towards a wide array of target molecules with different substitution patterns. Among direct arene formation reactions, applying environmentally benign organocatalysis to access arene moieties continues to attract increasing attention. This short review provides a brief summary of recent progress on organocatalyzed de novo (hetero)arene formation and applications in enantioselective synthesis. 1 Introduction 2 Arene Formation with Non-Covalent Organocatalysts 2.1 Arene Formation with Acid Organocatalysts 2.2 Arene Formation with Base Organocatalysts 2.3 Arene Formation with Hydrogen-Bonding Organocatalysts 3 Arene Formation with Covalent Organocatalysts 3.1 Arene Formation with Lewis Base Organocatalysts 3.1.1 Arene Formation with Secondary Amine Organocatalysts 3.1.2 Arene Formation with Tertiary Amine, Tertiary Phosphine and Sulfide Organocatalysts 3.1.3 Arene Formation with N-Heterocyclic Carbene Organocatalysts 3.2 Arene Formation with Lewis Acid Organocatalysts 4 Conclusion [ABSTRACT FROM AUTHOR]

Main observation and conclusion: A new dual palladium/scandium catalysis starting from β‐alkynyl ketones and o‐alkynyl anilines is reported for the first time, leading to the atom‐economic synthesis of rotationally hindered C3‐naphthylated indoles in moderate to good yields and high regioselectivity. This method can tolerate normal air conditions, and features the use of palladium/scandium cooperative catalysts without any ligand, facile double annulation involving various internal alkynes, and good functional group tolerance. [ABSTRACT FROM AUTHOR]

A three-step reaction sequence for the gram-scale synthesis of 1-chloro-2,3-dimethyl-4-phenylnaphthalene was developed. (i) Stereoselective dichlorocarbene addition to methyl angelate afforded methyl (1 S *,3 S *)-2,2-dichloro-1,3-dimethylcyclopropane-1-carboxylate (78% yield, >98% purity, distillation). (ii) Addition reaction of two molar amounts of PhLi afforded (1 S *,3 S *)-2,2-dichloro-1,3-dimethylcyclopropyldiphenylmethanol (81% yield, >98% purity, recrystallization). (iii) Key SnCl4-mediated benzannulation produced the desired product (83% yield, >98% purity, recrystallization) with three contiguous reaction sites. Five derivatization examples including benzylic reactions and cross-couplings at the pendant Cl-position are demonstrated. Some relevant distinctive benzannulations are also discussed. [ABSTRACT FROM AUTHOR]

Under the oxygen atmosphere conditions, PdCl2/CuCl2‐mediated one‐pot Wacker‐type decarboxylative benzannulation of sulfonyl o‐allylchalcones provides sulfonyl naphthalenes and carboxylic acids in MeOH at reflux. A plausible mechanism is proposed and discussed herein. This high‐yield protocol provides a highly effective intramolecular ring‐closure via one carbon‐carbon double bond (C=C) formation. [ABSTRACT FROM AUTHOR]

A cesium ion/alcohol promoted [4C+2C]annulation with the easily available diacetyl ketene dithioacetals as 4 C components to give poly‐substituted phenols is reported. It is revealed for the first time that in the presence of cesium ion and alcohol under mild alkaline conditions, the acetyl methyl carbon of ketene dithioacetals can be utilized as a carbon nucleophile. This nucleophile can attack at a carbonyl carbon of a ketone to form a C−C bond to initiate a [4C+2C]annulations, which lead to a poly‐substituted phenol product via intramolecular cyclization followed by aromatization. This reaction provides a new and practical route to the construction of poly‐substituted phenols between the same (two diacetyl ketene dithioacetals) or different ketones (a diacetyl ketene dithioacetal and a ketone) under very mild reaction conditions. [ABSTRACT FROM AUTHOR]

Regioselective synthesis of 3‐arylsulfonyl benzophenone derivatives via base mediated, aerial‐oxidative [3+3] benzannulation of α,β‐unsaturated aldehydes and 4‐sulfonyl butenones is reported. A variety of readily available acyclic building blocks are transformed into substituted biaryl ketones in this benzannulation reaction. The reaction proceeds under mild conditions in an open flask and uses atmospheric oxygen as oxidant to afford good yields of the products. Analogous benzannulation reactions of chalcone afforded highly substituted m‐terphenyl‐benzophenone derivatives. [ABSTRACT FROM AUTHOR]

Aromatic compounds are omnipresent in organic chemistry, which are the broadest skeletons of bioactive molecules, medicines, and materials. Due to their importance, conventional methods to assemble aromatic rings have attracted considerable attention. The direct formation of benzene cores from readily available acyclic precursors offers a highly versatile and superior approach to prepare both small organic molecules and sophisticated natural products. Recently, organocatalyst‐mediated annulation reaction, including phosphine‐, tertiary amine‐, secondary amine‐, primary amine‐, and NHC‐mediated benzannulation reactions, is considered as an efficient method to access multi‐substituted arenes. In this review, we will emphasize the selected examples of organocatalyst‐mediated benzannulation reactions of available acyclic precursors for the construction of diverse aromatics. [ABSTRACT FROM AUTHOR]

Although various methods for the preparation of dibenzofurans are available, an efficient, general synthesis of dibenzofurans from benzofurans remains an unsolved problem. Herein, we provide the first benzannulation of readily prepared 2‐nitrobenzofurans with alkylidene malononitriles. This methodology enables facile assembly of a wide variety of highly functionalized dibenzofurans in moderate to excellent yields under metal‐free conditions. Gram‐scale synthesis and further elaborations of the product were succesfully performed, demonstrating synthetic utility of this method. [ABSTRACT FROM AUTHOR]

A straightforward synthesis of benzonitriles is achieved via amino-catalyzed [3+3] benzannulation of α,β-unsaturated aldehydes and 4-arylsulfonyl-2-butenenitriles. Using pyrrolidine as an organocatalyst via iminium activation, a series of substituted benzonitriles were obtained in good to high yields in a regioselective manner. This reaction can proceed smoothly under mild reaction conditions and without the aid of any metals, additional oxidants, or strong bases, thus making this an efficient and environmentally friendly method to access benzonitriles. [ABSTRACT FROM AUTHOR]

By harnessing a highly efficient metal‐catalyzed tandem cycloaddition reaction as the key benzannulation step, a series of cyclopolyarene nanorings of varied sizes are obtained from poly(arylene‐butadiynylene) macrocyclic precursors, which can be synthesized relatively conveniently. Interestingly, due to the nonparallel bond connectivity of the repeat unit, unique Möbius topology is manifested by the cyclopolyarene nanorings composed of an odd number of repeat units, whereas cylindrical tubular structures with radial conjugation are formed with those consisting of an even number of repeat units. [ABSTRACT FROM AUTHOR]

Tunable catalytic annulation reactions of β alkynyl ketones with indoles have been developed, enabling multiple chemical bond‐forming events to selectively access skeletally diverse indole‐containing heterocycles with generally good yields. Silver‐catalyzed intermolecular benzannulation reaction of β‐alkynyl ketones with indoles afforded tetracyclic benzo[b]carbazoles whereas isochromen‐1‐yl‐substituted indoles could be obtained using the same silver catalysis by lowering the reaction temperature (0 °C or rt). Interestingly, using Sc(OTf)3 and AgOTf as a combined catalytic system led to the formation of C3‐naphthylated indoles via intramolecular benzannulation reaction. [ABSTRACT FROM AUTHOR]

The first application of ruthenium(0)‐catalyzed 1,2‐dione‐diyne [2+2+2] cycloaddition to PAH construction is achieved by the precision synthesis of soluble diindenoperylenes (DIPs), the electronic structures of which were investigated using steady‐state absorption and emission, transient absorption, cyclic voltammetry and time‐dependent density functional theory [ABSTRACT FROM AUTHOR]

Trifluoroacetic anhydride mediated one-pot intermolecular formal (4+2) benzannulation of oxygenated arylacetic acids with alkyl aryl ketones provides 4-aryl-2-arylacetoxynaphthalenes in moderate to good yields in the presence of H3 PO4 in an open-vessel in a straightforward procedure. A plausible mechanism is proposed and discussed. This protocol provides a highly effective ring-closure via two carbon–carbon (C–C) and one carbon–oxygen (C–O) bond-formation events. [ABSTRACT FROM AUTHOR]

A one‐pot method for the preparation of diamino‐substituted naphthalene derivatives from easily available starting materials aryl halides, 1,4‐bis(trimethylsilyl)butadiyne and amines is developed. Two C−N bonds, three C−C bonds and one aromatic ring are formed in this domino process. This transformation is achieved by the cooperative catalysis of Pd(OAc)2, Cu(Xantphos)I and Cu(OTf)2. A possible double Sonogashira coupling/hydroamination/ benzannulation reaction route is proposed. [ABSTRACT FROM AUTHOR]

TiCl4 (or SnCl4)-promoted hetero-type benzannulation reactions using various (2,2-dichlorocyclopropyl)(thiophen-2-yl)methanols proceeded smoothly to produce uniquely substituted 4-chlorobenzothiophenes (five examples). The present approach involves the first distinctive thiophene formation from thiophene cores, in contrast to traditional methods of thiophene formation from benzene cores. The stereocongested (less reactive) Cl position in the obtained 4-chlorobenzothiophenes functioned successfully as the partners of three cross-coupling reactions: (i) a Suzuki–Miyaura cross-couplings using Pd(OAc)2/SPhos/K3PO4 catalysis (seven examples; 63–91%), (ii) a hydroxylation using KOH/Pd(dba)2/tBu-XPhos catalysis (85%), and (iii) a borylation using a B2(pin)2/Pd(dba)2/XPhos/NaOAc catalysis-provided 4-(pin)B-benzothiophene (58%).

In combination with bulky substituents at the core, fourfold benzannulation at the cata‐positions stabilizes a nonacene sufficiently to allow its isolation and characterization by 1H NMR and X‐ray analysis. The four benzo units blueshift the absorption spectrum in comparison to a solely linear nonacene, but significantly increase the stability in the solid state. [ABSTRACT FROM AUTHOR]

Incorporation of a five‐membered ring into a helicene framework disrupts aromatic conjugation and provides a site for selective deprotonation. The deprotonation creates an anionic cyclopentadienyl unit, switches on conjugation, leads to a >200 nm red‐shift in the absorbance spectrum and injects a charge into a helical conjugated π‐system without injecting a spin. Structural consequences of deprotonation were revealed via analysis of a monoanionic helicene co‐crystallized with {K+(18‐crown‐6)(THF)} and {Cs+2(18‐crown‐6)3}. UV/Vis‐monitoring of these systems shows a time‐dependent formation of mono‐ and dianionic species, and the latter was isolated and crystallographically characterized. The ability of the twisted helicene frame to delocalize the negative charge was probed as a perturbation of aromaticity using NICS scans. Relief of strain, avoidance of antiaromaticity, and increase in charge delocalization assist in the additional dehydrogenative ring closures that yield a new planarized decacyclic dianion. [ABSTRACT FROM AUTHOR]

A facile and efficient intramolecular benzannulation strategy for the synthesis of substituted 6 H -benzo[ c ]chromenes from diazoaceto-acetate enones tethered with unactivated alkynes has been developed. The reaction proceeds in moderate to good yields under operationally simple conditions with thermally induced [4+2]-annulation of intermediate vinyl ketenes as the key step. [ABSTRACT FROM AUTHOR]

Regioselective benzannulation reaction of indol‐3‐yl‐but‐3‐yn‐2‐ols to functionaly embellished 2‐iodocarbazoles is described for the first time using iodine at room temperature in an open flask. This reaction proceeds through a cascade of 5‐endo spirocyclization, ring‐rearrangement through a vinyl shift, and aromatization in a short time. This protocol offers direct access to uncovered 2‐iodocarbazoles, with a broad substrate scope and good to moderate yields. Further, we have demonstrated the synthetic potential of these compounds using cross‐coupling reactions. [ABSTRACT FROM AUTHOR]