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A gold-catalyzed cascade cyclization of naphthalene-tethered allenynes gave strained fused phenanthrene derivatives. The reaction proceeds through the nucleophilic reaction of an alkyne with the activated allene to generate a vinyl cation intermediate, followed by arylation with a tethered naphthalene ring to form the 4H-cyclopenta[def]phenanthrene (CPP) scaffold. When using aryl-substituted substrates on the alkyne terminus, the gold-catalyzed reaction produced dibenzofluorene derivatives along with the CPP derivatives. Selective formation of CPP and dibenzofluorene derivatives depending on the reaction conditions is also presented.

Any singular irreducible cubic curve (or simply, cubic) after an affine transformation can be written as either y2=x3 , or y2=x2(x+1) , or y2=x2(x-1) . We classify the phase portraits of all quadratic polynomial differential systems having the invariant cubic y2=x2(x+1) . We prove that there are 63 different topological phase portraits for such quadratic polynomial differential systems. We control all the bifurcations among these distinct topological phase portraits. These systems have no limit cycles. Only three phase portraits have a center, 19 of these phase portraits have one polycycle, three of these phase portraits have two polycycles. The maximum number of separartices that have these phase portraits is 26 and the minimum number is nine, the maximum number of canonical regions of these phase portraits is seven and the minimum is three., C. Pantazi is also partially supported by the grant PID-2021-122954NB-100 funded by MCIN/AEI/10.13039/501100011033 and by “ERDF A way of making Europe”., Peer Reviewed, Postprint (published version)

© 2020, Springer Science+Business Media, LLC, part of Springer Nature. In this paper, we study the creation of zeros in a certain type of families of functions. The families studied are given by the difference of two basic functions with a translation made in the argument of one of these functions. The problem is motivated by applications in the 16th Hilbert problem and its ramifications. Here, we apply the results obtained to the study of bifurcations of critical periods in the Loud family of quadratic centers.

The carboarylation reaction of biphenyl-alkynes was successfully triggered by electrophilic attack of 1,1-bis(triflyl)ethylene on the alkyne moiety to give polycyclic aromatic hydrocarbons (PAHs) decorated by superacidic carbon acid functionality. Neutralisation of thus obtained acids with NaHCO yielded the corresponding sodium salts, which showed improved solubility in both aqueous and organic solvents.

A key challenge in the synthesis of diterpenoid alkaloids lies in identifying strategies that rapidly construct their multiply bridged polycyclic skeletons. Existing approaches to these structurally intricate secondary metabolites are discussed in the context of a "bond-network analysis" of molecular frameworks, which was originally devised by Corey some 40 years ago. The retrosynthesis plans that emerge from a topological analysis of the highly bridged frameworks of the diterpenoid alkaloids are discussed in the context of eight recent syntheses of hetidine and hetisine natural products and their derivatives. This Minireview highlights the extent to which network analyses of the type described here sufficed for designing synthesis plans, as well as areas where they had to be amalgamated with functional group oriented synthetic planning considerations.

A key challenge in the synthesis of diterpenoid alkaloids lies in identifying strategies that rapidly construct their multiply bridged polycyclic skeletons. Existing approaches to these structurally intricate secondary metabolites are discussed in the context of a "bond-network analysis" of molecular frameworks, which was originally devised by Corey some 40 years ago. The retrosynthesis plans that emerge from a topological analysis of the highly bridged frameworks of the diterpenoid alkaloids are discussed in the context of eight recent syntheses of hetidine and hetisine natural products and their derivatives. This Minireview highlights the extent to which network analyses of the type described here sufficed for designing synthesis plans, as well as areas where they had to be amalgamated with functional group oriented synthetic planning considerations.

A key challenge in the synthesis of diterpenoid alkaloids lies in identifying strategies that rapidly construct their multiply bridged polycyclic skeletons. Existing approaches to these structurally intricate secondary metabolites are discussed in the context of a "bond-network analysis" of molecular frameworks, which was originally devised by Corey some 40 years ago. The retrosynthesis plans that emerge from a topological analysis of the highly bridged frameworks of the diterpenoid alkaloids are discussed in the context of eight recent syntheses of hetidine and hetisine natural products and their derivatives. This Minireview highlights the extent to which network analyses of the type described here sufficed for designing synthesis plans, as well as areas where they had to be amalgamated with functional group oriented synthetic planning considerations.

A novel CoII -catalyzed polyene cyclization was developed that is uniquely effective when performed in hexafluoroisopropanol as the solvent. The process is presumably initiated by metal-catalyzed hydrogen-atom transfer (MHAT) to 1,1-disubstituted or monosubstituted alkenes, and the reaction is remarkable for its tolerance of internal alkenes bearing either electron-rich methyl or electron-deficient nitrile substituents. Electron-rich aromatic terminators are required in both cases. Terpenoid scaffolds with different substitution patterns are obtained with excellent diastereoselectivities, and the bioactive C20-oxidized abietane diterpenoid carnosaldehyde was made to showcase the utility of the nitrile-bearing products. Also provided are the results of several mechanistic experiments that suggest the process features an MHAT-induced radical bicyclization with late-stage oxidation to regenerate the aromatic terminator.

A straightforward approach to the synthesis of the challenging 12-arylindolo[1,2- c ]quinazolin-6(5 H)-ones through the palladium-catalyzed direct arylation of N -benzyl and NH-free [1,2- c ]quinazolin-6(5 H)-ones with aryl halides is described.

A straightforward one-pot approach to the synthesis of challenging 12-arylindolo[1,2- c ]quinazolin-6(5 H)-ones is described. Starting from readily available o -(o -aminophenylethynyl)trifluoroacetanilides, palladium-catalyzed aminoarylation of the triple bond with ArI, ArBr, and ArN 2+ BF 4- is followed by cyclization of the resulting N -trifluoroacetyl-2-(o -aminophenyl)-3-aryl indole. This sequential reaction provides the title compounds by means of a rare elimination of trifluoromethane.

A strained dibenzoazacyclooctyne (DIBAC) derivative was introduced for the preparation of a rotaxane by strain-promoted azide-alkyne cycloaddition (SPAAC), also referred to as a copper-free click reaction. The DIBAC can efficiently act as a bulky reactive chain stopper to transform a pseudorotaxane architecture consisting of a diazo-functionalized dialkoxy-naphthalene guest and a tetracationic cyclobis(paraquat-p-phenylene) (CBPQT(4+)) host into the corresponding [2]rotaxane. Furthermore, the use of the DIBAC is demonstrated to be limited to short rigid macrocycles, as it is unable to act as stopper for a rotaxane featuring a larger crown ether macrocyclic host.

A strained dibenzoazacyclooctyne (DIBAC) derivative was introduced for the preparation of a rotaxane by strain-promoted azide-alkyne cycloaddition (SPAAC), also referred to as a copper-free click reaction. The DIBAC can efficiently act as a bulky reactive chain stopper to transform a pseudorotaxane architecture consisting of a diazo-functionalized dialkoxy-naphthalene guest and a tetracationic cyclobis(paraquat-p-phenylene) (CBPQT(4+)) host into the corresponding [2]rotaxane. Furthermore, the use of the DIBAC is demonstrated to be limited to short rigid macrocycles, as it is unable to act as stopper for a rotaxane featuring a larger crown ether macrocyclic host.

1-Aminodecalins were prepared from acyclic precursors by combining the powerful twofold diene-transmissive Diels-Alder chemistry of [3]dendralenes with the simplicity of enamine formation. On mixing at ambient temperature, a simple dienal condenses with a primary or secondary amine to generate the enamine, a 1-amino-[3]dendralene in situ, and this participates as a double diene in a sequence of two Diels-Alder events with separate dienophiles. Overall, four C-C bonds and one C-N bond are formed. Mechanistic insights into these reactions are provided by means of density functional theory calculations.

We present a nitrogen-containing polycyclic aromatic hydrocarbon (N-PAH), namely 12-methoxy-9-(4-methoxyphenyl)-5,8-diphenyl-4-(pyridin-4-yl)pyreno[1,10,9-h,i,j]isoquinoline (c-TPE-ON), which exhibits high quantum-yield emission both in solution (blue) and in the solid state (yellow). This molecule was unexpectedly obtained by a three-fold, highly regioselective photocyclodehydrogenation of a tetraphenylethylene-derived AIEgen. Based on manifold approaches involving UV/Vis, photoluminescence, and NMR spectroscopy as well as HRMS, we propose a reasonable mechanism for the formation of the disk-like N-PAH that is supported by density functional theory calculations. In contrast to most PAHs that are commonly used, our system does not suffer from entire fluorescence quenching in the solid state due to the peripheral aromatic rings preventing π-π stacking interactions, as evidenced by single-crystal X-ray analysis. Moreover, its rod-like microcrystals exhibit excellent optical waveguide properties. Hence, c-TPE-ON comprises a N-PAH with unprecedented luminescent properties and as such is a promising candidate for fabricating organic optoelectronic devices. Our design and synthetic strategy might lead to a more general approach to the preparation of solution- and solid-state luminescent PAHs. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Starting from three achiral compounds, the title reaction provides rapid access to a variety of molecules that contain indoline, tetrahydroquinoline, and tetrahydroisoquinoline moieties (see scheme). The process features the efficient formation of multiple new bonds and chiral centers, excellent stereoselectivity, oxetane desymmetrization, and easy product purification through filtration. Copyright © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Starting from three achiral compounds, the title reaction provides rapid access to a variety of molecules that contain indoline, tetrahydroquinoline, and tetrahydroisoquinoline moieties (see scheme). The process features the efficient formation of multiple new bonds and chiral centers, excellent stereoselectivity, oxetane desymmetrization, and easy product purification through filtration. Copyright © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Natural inspiration: Based on the biosynthesis of squalene‐derived polyethers, a total synthesis of teurilene is described. The carbocation formation in the Nicholas reaction serves to control the initiation of a polyepoxide ring‐opening cascade. The three furan rings present in teurilene were obtained in excellent yield in one step. Boc=tert‐butoxycarbonyl, TMS=trimethylsilyl.

Let's twist again: A "clean reaction" strategy based on thermally eliminating lactam bridges from a soluble acene precursor through a retro-Diels-Alder reaction gives a new, stable, green heptatwistacene (see structure). The molecule has a twist angle of 23.49°, is very stable even in air, and has an optical band gap of 1.82 eV. © 2012 Wiley-VCH Verlag GmbH&Co. KGaA, Weinheim.

Let's twist again: A "clean reaction" strategy based on thermally eliminating lactam bridges from a soluble acene precursor through a retro-Diels-Alder reaction gives a new, stable, green heptatwistacene (see structure). The molecule has a twist angle of 23.49°, is very stable even in air, and has an optical band gap of 1.82 eV. © 2012 Wiley-VCH Verlag GmbH&Co. KGaA, Weinheim.

Let's twist again: A "clean reaction" strategy based on thermally eliminating lactam bridges from a soluble acene precursor through a retro-Diels-Alder reaction gives a new, stable, green heptatwistacene (see structure). The molecule has a twist angle of 23.49°, is very stable even in air, and has an optical band gap of 1.82 eV. © 2012 Wiley-VCH Verlag GmbH&Co. KGaA, Weinheim.

Cascade cyclization of bromoenynes bearing an aryl group with catalytic amounts of palladium(II) acetate and cesium carbonate led to the direct construction of tri- or tetracyclic heterocycles. Direct arylation of a pyrrole, furan or thiophene ring in the cascade reaction affords the corresponding fused heteroarenes in moderate to good yields.

Free radical approach to fused vinylcyclopropane derivatives is described. Homolytic decomposition of Barton esters 4a-f in the presence of activated alkynes affords bicyclo[3.1.0]hex-2-ene derivatives 5a-g in moderate yields (18-52 %). The propagation sequence comprises: intermolecular addition/5-exo-cyclization/3-exo-cyclization/beta -elimination, and allows for a one-pot synthesis of bicyclic cyclopropane derivatives starting from two acyclic, unsaturated compounds. (C) 2001 Academie des sciences / Editions scientifiques et medicales Elsevier SAS.

Free radical approach to fused vinylcyclopropane derivatives is described. Homolytic decomposition of Barton esters 4a-f in the presence of activated alkynes affords bicyclo[3.1.0]hex-2-ene derivatives 5a-g in moderate yields (18-52 %). The propagation sequence comprises: intermolecular addition/5-exo-cyclization/3-exo-cyclization/beta -elimination, and allows for a one-pot synthesis of bicyclic cyclopropane derivatives starting from two acyclic, unsaturated compounds. (C) 2001 Academie des sciences / Editions scientifiques et medicales Elsevier SAS.

An efficient synthetic route towards previously inaccessible 7-bromo-1,3-diazapyrenes through an in-melt peri-cyclization of readily available 7-(5-bromo-3,4-dihydropyrimidin-4-yl)-1H-perimidines is described. © 2018 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim