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Rapid construction of new fluorescence emitters is essential in advancing synthetic luminescent materials. This study illustrated a piperidine‐promoted reaction of chiral dialdehyde with benzoylacetonitrile and malonitrile, leading to the formation of the 6/6/7 fused cyclic product in good yield. The proposed reaction mechanism involves a dual condensation/cyclization process, achieving the formation of up to six bonds for fused polycycles. The single crystal structure analysis revealed that the fused cyclic skeleton contains face‐to‐face naphthyl and cyanoalkenyl motifs, which act as the electronic donor and acceptor, respectively, potentially resulting in through‐space charge transfer (TSCT) emission. While the TSCT emissions were weak in solution, a notable increase in luminescence intensity was observed upon aggregation, indicating bright fluorescent light. A series of theoretical analyses further supported the possibility of spatial electronic communication based on frontier molecular orbitals, the distance of charge transfer, and reduced density gradient analysis. This work not only provides guidance for the one‐step synthesis of complex polycycles, but also offers valuable insights into the design of aggregation‐enhanced TSCT emission materials. [ABSTRACT FROM AUTHOR]

A solid‐state method was developed for generating diarylisonaphthofurans from 1,3‐diaryl‐1,3‐dihydronaphthofuranols. The generated reactive molecules were stable in the solid state and could be stored without any extra precautions. X‐ray diffraction analysis revealed a typical quinoidal structure. Furthermore, the mechanochemical Diels–Alder reaction of 1,3‐diarylisonaphthofurans with epoxynaphthalenes afforded synthetically attractive diepoxypentacenes. [ABSTRACT FROM AUTHOR]

The Ugi reaction has become one of the highly explored reactions for the formation of multifunctional adducts, due to the mild reaction conditions, wide scope and high variability. By carefully selecting the starting four components, Ugi‐adducts could undergo different kinds of post‐transformations for the synthesis of bioactive heterocycles, natural products and macrocycles. Considering the significance of polycycles, diverse post‐Ugi transformations have been developed over the years for constructing structurally novel polycycles. In this account, we summarize important efforts for the synthesis of polycyclic N‐heterocycles via post‐Ugi cyclizations from the Van der Eycken laboratory onwards 2016. With the aid of transition metal catalysis from gold, rhodium, silver and palladium, as well as metal‐free strategies, versatile polyheterocycles are prepared with high efficiency and step‐economy. [ABSTRACT FROM AUTHOR]

Ugi reactions have been widely studied due to their mild reaction conditions, high structural variability, and wide applications. Ugi adducts have proved to be highly efficient for different kinds of post-transformations by carefully choosing the starting four components. Considering the importance of polycycles, diverse post-Ugi transformations have been employed for the construction of structurally novel polycyclic N-heterocycles. This minireview summarizes the recent developments of post-Ugi reactions for the synthesis of polycycles after the year 2019. Through transition metal catalysis from gold, rhodium, silver, copper, and palladium, as well as transition metal-free approaches, versatile polycycles are constructed in a highly efficient and step-economical manner. [ABSTRACT FROM AUTHOR]

In this paper we study planar polynomial Kolmogorov's differential systems \[ X_\mu\quad\begin{cases}{\dot{x}=f(x,y;\mu),}\\{\dot{y}=g(x,y;\mu),} \end{cases} \] with the parameter $\mu$ varying in an open subset $\Lambda\subset\mathbb{R}^N$. Compactifying $X_\mu$ to the Poincaré disc, the boundary of the first quadrant is an invariant triangle $\Gamma$, that we assume to be a hyperbolic polycycle with exactly three saddle points at its vertices for all $\mu\in\Lambda.$ We are interested in the cyclicity of $\Gamma$ inside the family $\{X_\mu\}_{\mu\in\Lambda},$ i.e., the number of limit cycles that bifurcate from $\Gamma$ as we perturb $\mu.$ In our main result we define three functions that play the same role for the cyclicity of the polycycle as the first three Lyapunov quantities for the cyclicity of a focus. As an application we study two cubic Kolmogorov families, with $N=3$ and $N=5$, and in both cases we are able to determine the cyclicity of the polycycle for all $\mu\in\Lambda,$ including those parameters for which the return map along $\Gamma$ is the identity.

Polycycles are abundantly present in numerous advanced chemicals, functional materials, bioactive molecules and natural products. However, the strategies for the synthesis of polycycles are limited to classical reactions and transition metal‐catalyzed cross‐coupling reactions, requiring pre‐functionalized starting materials and lengthy synthetic operations. The emergence of novel approaches shows great promise for the fields of organic/medicinal/materials chemistry. Among them, transition metal‐catalyzed C−H activation followed by intermolecular annulation reactions prevail, due to their straightforward manner with high atom‐ and step‐economy, providing rapid, concise and efficient methods for the construction of diverse polycycles. Several strategies have been developed for the synthesis of polycycles, relying on sequential multiple C−H activation/annulation, or combination of C−H activation/annulation and further interaction with a proximal group, or merger of C−H activation with a cycloaddition reaction, or in situ formation of the directing group. These are attractive, efficient, step‐ and atom‐economic methods starting from commercially available materials. This Minireview will provide an introduction to transition metal‐catalyzed C−H activation for the synthesis of polycycles, helping researchers to discover indirect connections and reveal hidden opportunities. It will also promote the discovery of novel synthetic strategies relying on C−H activation. [ABSTRACT FROM AUTHOR]

This article, published in Chemistry - A European Journal, discusses the solid-state generation of diarylisonaphthofurans from 1,3-diaryl-1,3-dihydronaphthofuranols. The reactive molecules generated were found to be stable in the solid state and could be stored without any precautions. Additionally, the article explores the mechanochemical Diels-Alder reaction of 1,3-diarylisonaphthofurans with epoxynaphthalenes, which resulted in the synthesis of diepoxypentacenes. For more detailed information, readers can refer to the Research Article by T. Hamura et al. [Extracted from the article]

Abstract: An efficient access to tetrahydrofuran‐fused bicyclo[2.2.2]oct‐2‐enes via palladium‐catalyzed cyclization of oxygen‐tethered 2,7‐alkadiynylic carbonates with 2‐(buta‐2,3‐dienyl)malononitrile has been developed. Perfect chiral induction was observed when a substituent was introduced to the propargylic position affording the optically active polycyclic products of both enantiomers. Control experiments showed that the oxygen tether of 2,7‐alkadiynylic carbonates and the two cyano groups in allene are indispensible for this transformation. [ABSTRACT FROM AUTHOR]

In this paper, we are concerned about the qualitative behavior of planar Filippov systems around some typical invariant sets, namely, polycycles. In the smooth context, a polycycle is a simple closed curve composed by a collection of singularities and regular orbits, inducing a first return map. Here, this concept is extended to Filippov systems by allowing typical Filippov singularities lying on the switching manifold. Our main goal consists in developing a method to investigate the unfolding of polycycles in Filippov systems. In addition, we apply this method to describe bifurcation diagrams of Filippov systems around certain polycycles. [ABSTRACT FROM AUTHOR]

Acid-mediated domino reaction of ortho -carbonylated alkynyl-substituted arylaldehydes with phenols is described. The implement of this reaction can provide directly a variety of tetracyclic indeno[2,1- c ]chromen-7-one products in good yields. The mechanism was proposed to be a domino indanone ring formation/ortho-alkylation of phenols/dehydrated cyclization for the formation of polycyclic skeleton. In addition, several interesting dimeric products containing a pentacyclic scaffold were also afforded stereoselectively albeit in moderate yields. The present transformations feature the use of simple acid catalyst, short reaction time and good substrate scope. [ABSTRACT FROM AUTHOR]

Protein tyrosine phosphatase 1B (PTP1B) has been proposed to be an ideal target for treatment of type II diabetes and obesity. However, no druggable PTP1B inhibitor has been established and there is still an urgent demand for the development of structurally novel PTPIB inhibitor. Herein, we reported core-structurally novel PTP1B inhibitors with low micromole-ranged inhibitory activity by one-pot reaction from simple starting materials. Further studies demonstrated some of these active compounds had a specific selectivity over other PTPs. The structure and activity relationship was also described. The best active and selective compound 5e inhibited PTP1B activity with an IC 50 of 4.53 μM. Molecular docking analysis further demonstrated that compound 5e bound to the active pocket of PTP1B. The results might provide some insights for further development of new drugs for type II diabetes and obesity. [ABSTRACT FROM AUTHOR]

Allene-yne-allene and allene-ene-allene N-tosyl-linked substrates with two chiral centres in the α-position of the allene moiety were satisfactorily prepared starting both from racemic and chiral propargylic alcohols. The Wilkinson's complex-catalyzed [2+2+2] cycloaddition reaction of these substrates was evaluated. In the case of enantiomerically pure bisallenes, high stereoselectivity was observed, giving a diastereomerically pure cycloadduct. The chirality of starting bisallene substrates can be completely transferred to the cycloadducts, representing an atom-economical and enantiospecific process for the construction of fused polycycles. However, when reacting an oxygen-linked allene-ene-allene substrate, the stereoselectivity decreased and two diastereoisomers were formed. A detailed characterization study of the resulting cycloadducts allowed us to identify the enantioisomer generated in the cycloaddition. [ABSTRACT FROM AUTHOR]

A Michael-Michael-acetalization cascade between 4-(2-hydroxyphenyl)but-3-en-2-ones and α,β-unsaturated aldehydes via a novel dual activation mode promoted by pyrrolidine was successfully established. Consequently, various novel tetrahydro-6-hydroxyl-6 H -benzo[ c ]chromen-9-one derivatives were prepared in excellent diastereoselectivities and moderate to good yields. Further diverse modification of the resulting tricyclic scaffolds provided a facile pathway to achieve a variety of tetrahydro-6-hydroxyl-6 H -benzo[ c ]chromen-9-one analogs. [ABSTRACT FROM AUTHOR]

A one-pot method for the synthesis of novel polycyclic carbazole derivatives from readily available starting materials using a sequential multicomponent reaction/Fisher indolization strategy is described. [ABSTRACT FROM AUTHOR]

Abstract: We consider the one-parameter family of planar quintic systems, , , introduced by A. Bacciotti in 1985. It is known that it has at most one limit cycle and that it can exist only when the parameter m is in . In this paper, using the Bendixson–Dulac theorem, we give a new unified proof of all the previous results. We shrink this interval to and we prove the hyperbolicity of the limit cycle. Furthermore, we consider the question of the existence of polycycles. The main interest and difficulty for studying this family is that it is not a semi-complete family of rotated vector fields. When the system has a limit cycle, we also determine explicit lower bounds of the basin of attraction of the origin. Finally, we answer an open question about the change of stability of the origin for an extension of the above systems. [Copyright &y& Elsevier]

We have synthesized a variety of 2-[(2-alkyl-1H-indol-3-yl)methylene]malonates and studied their scandium-catalyzed in-tramolecular Friedel-Crafts reactions leading to the corresponding polycyclic compounds such as indeno[1,2-b]indoles and benzo[1,2- b]carbazoles. [ABSTRACT FROM AUTHOR]

Abstract: We study Gause-type predator–prey models when the interaction between predator and prey is not locally-Lipschitz continuous in the absence of one of them. We shall show that in this case there appears a polycycle, which affects the existence of limit cycles for the system. We apply the results to study the existence of limit cycles for a classical Gause system. [ABSTRACT FROM AUTHOR]

Abstract: Let P be a not necessarily bounded polycycle of an analytic vector field on an open set of the plane. Suppose that the singularities which appear after desingularization of the vertices of P are hyperbolic. Consider the function T defined by the return time near P. It is shown that the function T and its derivative have asymptotic expansions similar to the series of Dulac but with negative powers. [Copyright &y& Elsevier]

We prove the following main theorem of the theory of ( r, q)-polycycles. Suppose a nonseparable plane graph satisfies the following two conditions: (1) each internal face is an r-gon, where r ≥ 3; (2) the degree of each internal vertex is q, where q ≥ 3, and the degree of each boundary vertex is at most q and at least 2. Then it also possesses the following third property: (3) the vertices, the edges, and the internal faces form a cell complex. Simple examples show that conditions (1) and (2) are independent even provided condition (3) is satisfied. These are the defining conditions for an ( r, q)-polycycle. [ABSTRACT FROM AUTHOR]

Let P be a not necessarily bounded polycycle of an analytic vector field on an open set of the plane. Suppose that the singularities which appear after desingularization of the vertices of P are formally linearizable. Consider the function T defined by the return time near P. It is shown that the function T and its derivative T′ have asymptotic expansions in {xμ}μ∈R and {xδ log x}δ∈R. It is also shown that under some other conditions imposed on the polycycle vertices, the asymptotic expansions of T and T′ converge absolutely and uniformly to these functions, respectively. These results are applied to the polycycles of the analytic vector fields which have a Darboux first integral. In particular, it is obtained that if P is a polycycle of a Hamiltonian vector field with an analytic (polynomial if P is unbounded) Hamiltonian function, T is a nonoscillating function. Another application concerns the nilpotent centers or focus, since the singularities which appear after desingularization of such a singularity have analytic first integrals. [Copyright &y& Elsevier]

We study the stability of a type of unbounded polycycles which appear in some planar differential equations. Each of these polycycles has hyperbolic corners, but the product of the hyperbolicity ratios of all its corners does not decide its stability. We obtain an explicit convergent integral whose sign gives the stability of the polycycle. [Copyright &y& Elsevier]

We study planar graphs embedded in the plane that have chemical applications: the degrees of all vertices are 3 or 2, all internal faces but one or two are r-gons, and each internal face is a simply connected domain. For wide classes of such graphs, we solve the existence problem for embeddings of the graph metric on the vertices in multidimensional cubes or cubical lattices preserving or doubling all the distances. Incidentally we present a complete classification of some interesting families of such graphs. [ABSTRACT FROM AUTHOR]

The cyclicity of four classes of codimension 3 plnnar polycycles and ensembles containing a saddle-node and two hyperbdic saddles is dealt with. The exnct cyclicity or cyclicity bound of them is obtained by finitely-smooth normal form theory. [ABSTRACT FROM AUTHOR]

By means of finitely-smooth normal form theory and the method of infinitesimal analysis, it is proved that the cyclicity of a planar codimension 3 polycycle S(2) is three and the complete bifurcation diagram is provided. [ABSTRACT FROM AUTHOR]

Abstract: We developed a six-step synthesis of the polycyclic core of vincorine using two cascades of reactions. A cascade of Michael–Mannich reactions was employed for one-pot preparation of a polycyclic intermediate, which was transformed into the desired polycyclic pyrroloindoline ring system using a cascade of methanolysis-N-imine cyclization reactions. [Copyright &y& Elsevier]