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A base promoted oxidative [4+2] annulation of pyrrole‐2‐carbaldehyde derivatives with o‐hydroxyphenyl propargylamines for the synthesis of highly substituted indolizines has been developed. Using DBN as base, a broad range of 5,6,7‐trisubstituted indolizines have been prepared in good to excellent yields under mild conditions, and many useful functional groups can be tolerated. [ABSTRACT FROM AUTHOR]

Arylethynyl‐substituted dipyrrolyldiketone BF2 complexes as anion‐responsive π‐electronic molecules exhibited characteristic electronic properties derived from conformation changes upon anion binding, which caused an increase in UV/vis absorption and associated two‐photon absorption. The anion complexes showed expanded planar regions assisted by intramolecular interactions, resulting in charge‐by‐charge ion‐pairing assemblies in the solid state. [ABSTRACT FROM AUTHOR]

As the key intermediates in metal‐promoted/catalyzed C−C bond coupling reactions of nitriles and alkynes, azametallacyclopentadienes, M(N=CR1−CR2=CR3), are an important class of azametallacycles. Although the first authentic azametallacyclopentadienes were documented in 1986, their chemistry towards solid‐state structures, intrinsic reactivity, and synthetic application was rarely investigated for a long time. At the beginning of this century, seminal works about the applications of azametallacyclopentadienes in the synthesis of heterocycles, including multi‐substituted pyridines, isoquinolines, furans, and pyrroles were reported. Subsequently, a series of new complexes with this motif, namely the Group 4, aluminum, actinide, and rare‐earth azametallacyclopentadienes were isolated and structurally characterized. Among them, the rare‐earth azametallacyclopentadiene expresses high reactivity towards unsaturated molecules, such as nitriles, isocyanides, and Mo(CO)6 to provide novel fused metallacycles. In this Concept, we reviewed the advances in the preparation, reactivity, and synthetic application of azametallacyclopentadienes in the past twenty years. [ABSTRACT FROM AUTHOR]

Near‐infrared (NIR) fluorophores with characteristics such as deep tissue penetration, minimal damage to the biological samples, and low background interference, are highly sought‐after materials for in vivo and deep‐tissue fluorescence imaging. Herein, series of 3‐pyrrolylBODIPY derivatives and 3,5‐dipyrrolylBODIPY derivatives have been prepared by a facile regioselective nucleophilic aromatic substitution reaction (SNAr) on 3,5‐halogenated BODIPY derivatives (3,5‐dibromo or 2,3,5,6‐tetrachloroBODIPYs) with pyrroles. The installation of a pyrrolic unit onto the 3‐position of the BODIPY chromophore leads to a dramatic red shift of both the absorption (up to 160 nm) and the emission (up to 260 nm) in these resultant 3‐pyrrolylBODIPYs with respect to that of the BODIPY chromophore. Their further 5‐positional functionalization provides a facile way to fine tune their photophysical properties, and these resulting dipyrrolylBODIPYs and functionalized pyrrolylBODIPYs show strong absorption in the deep red‐to‐NIR regions (595–684 nm) and intense NIR fluorescence emission (650–715 nm) in dichloromethane. To demonstrate the applicability of these functionalized pyrrolylBODIPYs as NIR fluorescent probes for cell imaging, pyrrolylBODIPY 6 a containing mitochondrion‐targeting butyltriphenylphosphonium cationic species was also prepared. It selectively localized in mitochondria of HeLa cells, with low cytotoxicity and intense deep red fluorescence emission. [ABSTRACT FROM AUTHOR]

Despite common occurrence in molecules of value, methods for transforming sulfonamides are distinctly lacking. Here we introduce easy‐to‐access sulfonyl pyrroles as synthetic linchpins for sulfonamide functionalization. The versatility of the sulfonyl pyrrole unit is shown by generating a variety of products through chemical, electrochemical and photochemical pathways. Preliminary results on the direct functionalization of primary sulfonamides are also provided, which may lead to new modes of activation. [ABSTRACT FROM AUTHOR]

We report the synthesis of unprecedented tetra‐urea derivatives of calix[4]arene and calix[4]pyrrole containing four spiropyran (SP) units at their upper rim. We investigate the photo‐ and acid‐induced isomerization of the monomeric and homo‐dimeric tetra‐ureas derivatives using UV‐Vis and 1H NMR spectroscopies. At micromolar concentration, irradiation of the samples with 365 nm light induces changes in their absorption spectra that are consistent with SP→merocyanine (MC) isomerization. However, analogous experiments at millimolar concentration do not produce noticeable changes in the 1H NMR spectra. The addition of triflic acid to micromolar and millimolar solutions of the tetra‐ureas produces the quantitative isomerization of the SP units to the protonated merocyanine form (E‐MCH+) and the simultaneous disassembly of the capsular dimers to form ill‐defined aggregates. The neutralization of the acid solutions resets the SP form. Under these acid/base treatment conditions, the controlled release of the included guest and the reassembly of the all‐SP tetra‐urea dimers occurs at different extents depending on its calix[4]arene or calix[4]pyrrole scaffold. [ABSTRACT FROM AUTHOR]

A variety of π‐electronic ion‐pairing assemblies can be constructed by combining anion complexes of π‐electronic systems and countercations. In this study, a series of anion‐responsive π‐electronic molecules, dipyrrolyldiketone PtII complexes containing a phenylpyridine ligand, were synthesized. The resulting PtII complexes exhibited phosphorescence emission, with higher emission quantum yields (0.30–0.42) and microsecond‐order lifetimes, and solution‐state anion binding, as revealed by our spectroscopic analyses. These PtII complexes displayed solid‐state ion‐pairing assemblies, exhibiting various anion‐binding modes, which derived from pyrrole‐inverted and pyrrole‐non‐inverted conformations, and packing structures, with the contribution of charge‐by‐charge assemblies, which were dependent on the substituents in the PtII complexes and the geometries and electronic states of their countercations. [ABSTRACT FROM AUTHOR]

Herein, a divergent synthesis of a variety of 2α‐ and 5α‐substituted furan derivatives from 2‐hydroxy‐1,4‐diones is reported. By using appropriate substrates and an acid catalyst, the reactions occurred selectively through cyclization/1,6‐conjugate addition or cyclization/Friedel–Crafts‐type cascade reactions. A broad range of nucleophilic reagents (>10 types for the 1,6‐conjugate addition for 5α substitution and >20 types for the Friedel–Crafts‐type cascade reaction for 2α substitution), including alcohols, amides, furan, thiophene, pyrrole, indole, phenols, and many others, can successfully participate in the reactions, providing a universal strategy for a diversity‐oriented synthesis of α‐substituted furan derivatives. Deuteriation experiments and DFT calculations were carried out to support the proposed reaction mechanisms. Antifungal activity experiments revealed that products with an indole or 4‐hydroxycoumarin core substituted at the 2α position showed moderate activities against Rhizoctorzia solani and Botrytis cinerea, respectively. [ABSTRACT FROM AUTHOR]

The total synthesis of dictyodendrins A–F was achieved by using the gold(I)‐catalyzed annulation of a conjugated diyne with N‐Boc‐pyrrole for direct construction of the pyrrolo[2,3‐c]carbazole scaffold. Late‐stage functionalization of the resulting pyrrolo[2,3‐c]carbazole to introduce various substituents provided divergent access to dictyodendrins. Some dictyodendrin analogues exhibited inhibitory activities toward CDK2/CycA2 and GSK3. [ABSTRACT FROM AUTHOR]

We report the synthesis of an unprecedented mono‐gold(I) phosphine complex based on a "two‐wall" aryl‐ethynyl extended calix[4]pyrrole. We describe and compare the binding properties of the parent 10α,20α‐bis‐aryl‐ethynyl calix[4]pyrrole ligand and the prepared organometallic compound as receptors for tetraalkylammonium chloride salts in dichloromethane and acetone. We describe the results of 1H NMR, UV–Vis titrations and isothermal titration calorimetry (ITC) experiments in dichloromethane and acetone, aiming to thermodynamically characterize the formed complexes. The obtained results indicate a noticeable decrease in the binding affinity of the chloride for the mono‐gold(I) receptor 1 compared to the parent ligand 2. The increase in the negative value of the electrostatic surface potential at the center of the aromatic ring of the gold(I) meso‐aryl‐ethynyl substituent serves to explain the observed results and the presence in solution of the chloride complex of 1 as a mixture of two conformers. [ABSTRACT FROM AUTHOR]

In this paper, we describe an efficient and atom‐economical synthesis of highly functionalized pyrroles, pentafulvenes, and pyrrolopyridines by [2+2] cycloaddition–retroelectrocyclization of N‐substituted propargylamines with tetracyanoethylene, followed by the treatment of the resulting tetracyanobutadiene derivatives with silica gel. In this reaction, silica gel plays an important role to promote the intramolecular cyclization to afford the heterocyclic products from the tetracyanobutadiene intermediates. The products were obtained selectively depending on the substituent on the nitrogen atom of the starting propargylamines. [ABSTRACT FROM AUTHOR]

Dearomatisation of indole derivatives to the corresponding isatin derivatives has been achieved with the aid of visible light and oxygen. It should be noted that isatin derivatives are highly important for the synthesis of pharmaceuticals and bioactive compounds. Notably, this chemistry works excellently with N‐protected and protection‐free indoles. Additionally, this methodology can also be applied to dearomatise pyrrole derivatives to generate cyclic imides in a single step. Later this methodology was applied for the synthesis of four pharmaceuticals and a pesticide called dianthalexin B. Detailed mechanistic studies revealed the actual role of oxygen and photocatalyst. [ABSTRACT FROM AUTHOR]

A photochemical approach to polysubstituted heterocycles using UV‐induced alkene isomerization is described. The method allows for the synthesis of disubstituted furans and pyrroles under mild and neutral conditions and also provides access to a class of trisubstituted furans pertinent to natural‐product synthesis. The method has broad functional‐group tolerance and many richly decorated heterocycles have been prepared incorporating functional groups that are unstable under Brønsted and Lewis acidic conditions. [ABSTRACT FROM AUTHOR]

We disclose the results of our investigations on the influence that the insertion method of aryl‐extended calix[4]pyrrole into liposomal membranes exerts on their properties as anion carriers. We use the standard HPTS assay to assess the transport properties of the carriers. We show that the post‐insertion of the carrier, as DMSO solution, assigns better transport activities to the "two‐wall" α,α‐aryl‐extended calix[4]pyrrole 1 compared to the "four‐wall" α,α,α,α‐counterpart 2. Notably, opposite results were obtained when the carriers were pre‐inserted into the liposomal membranes. We assign this difference to an improved incorporation of carrier 2 into the membrane when delivered by the pre‐insertion method. On the other hand, carrier 1 shows comparable levels of transport independently of the method used for its incorporation. Thus, an accurate comparison of the chloride transport activities featured by these two carriers demands their pre‐incorporation in the liposomal membranes. In contrast, using the lucigenin assay with the pre‐insertion method both carriers displayed similar transport efficiencies. The influence that the insertion method (post‐insertion vs. pre‐insertion) of "two‐wall" and "four‐wall" aryl‐extended calix[4]pyrrole carriers into liposomal membranes exerts on their chloride transport properties using the HPTS assay is described. The pre‐insertion method allowed a more accurate and reliable comparison of the transport activities of these carriers, being greater for the "four‐wall" carrier. [ABSTRACT FROM AUTHOR]

Pyrrole‐based zwitterionic π‐electronic systems including a phenylcarboxylate (benzoate) anionic site and an N‐methyl pyridinium cation unit were synthesized. Spectroscopic and theoretical examinations revealed the intermolecular hydrogen‐bonding interactions of the pyrrole NH group and the 3‐pyridinium and 3‐benzoate ortho‐CH moieties of zwitterions with a carboxylate anion to form self‐assembled dimers. The self‐assembled dimers were found to exist in equilibrium with the corresponding monomers in DMSO, whose dimerization ability was examined by concentration‐dependent measurements. Pyrrole‐based zwitterionic π‐electronic systems including a phenylcarboxylate anionic site and an N‐methyl pyridinium cation unit were synthesized. Spectroscopic and theoretical examinations revealed the intermolecular hydrogen‐bonding interactions of the pyrrole NH group and the 3‐pyridinium and 3‐benzoate ortho‐CH moieties of zwitterions with a carboxylate anion to form self‐assembled dimers. [ABSTRACT FROM AUTHOR]

Abstract: Polycyclic heteroaromatic compounds including pyrrole units are promising functional scaffolds owing to their electron‐rich nature, bright fluorescence, and applicability to anion recognition at the pyrrolic hydrogen atom. We report herein the effective synthesis of pseudo‐aza[5]helicene and aza[7]helicene derivatives, and unexpected formation of azahepta[8]circulenes by oxidative fusion reactions. By choosing reaction conditions and peripheral substituents attached at the terminal indole moieties, we obtained aza[7]helicenes 10 a–c and azahepta[8]circulenes 11 a,c selectively in moderate to good yields. Their solid‐state structures have been revealed by X‐ray diffraction analysis. UV/Vis absorption, emission, and cyclic voltammetry of these compounds were studied in comparison with those of previously reported tetraaza[8]circulene (TA8C), a symmetric and planar molecule. Furthermore, the enantiomeric separation of dimethyl‐substituted aza[7]helicene 10 b was achieved, and the racemization kinetics have been elucidated both theoretically and experimentally. This work illustrates a wealth of advantages of pyrrole incorporation into the polycyclic aromatic scaffolds in terms of synthetic aspects, structural variation, and optical tuning. [ABSTRACT FROM AUTHOR]

Abstract: PdII‐mediated annulative double C−H activation is shown to efficiently convert 1,n‐dipyrrolylalkanes into extensively π‐conjugated bipyrroles not accessible by conventional oxidative coupling protocols. This approach is applicable to both electron‐rich and electron‐deficient systems, and has been further developed into tandem processes involving further cyclization of substituents or oxygenation of pyrrolic α‐positions. The new bipyrrole intermediates show enhanced fluorescence as well as tunable optical properties controlled by the alignment of chromophore subunits. Photophysical data, including femtosecond transient absorptions, reveal solvent‐induced intramolecular charge transfer in their excited states, dependent on the polarity of the medium. [ABSTRACT FROM AUTHOR]

An efficient route to highly substituted indoles was developed. It included regioselective functionalization of tetrahydroindol-4(5 H)-ones, prepared by ring-opening cyclization of cyclohexane-1,3-dione-2-spirocyclopropanes with primary amines, and subsequent oxidation. The 6-substituted indoles were synthesized from a readily available 5-substituted cyclohexane-1,3-dione-2-spirocyclopropane. The synthesis of 5- and 7-substituted indoles was achieved by regioselective electrophilic alkylation of tetrahydroindol-4(5 H)-one, followed by oxidation. The 4-substituted indoles were synthesized by nucleophilic alkylation of the corresponding pyrrole derivative, which was prepared by partial oxidation of tetrahydroindol-4(5 H)-one, and sequential oxidation. The synthesis of 4-substituted indoles was also accomplished by palladium-catalyzed coupling of 4-hydroxyindole-derived triflates. Furthermore, the synthesis of 4,5,6,7-tetrasubstituted indoles was achieved by using these regioselective alkylations. [ABSTRACT FROM AUTHOR]

Starting from 3-alkoxy-2-aryl-substituted pyrroles and aromatic aldehydes, a collection of new dipyrrins was prepared. Under the standard conditions of Treibs, these were converted into the corresponding boron dipyrrins (BODIPYs). Compounds of this type with alkoxy groups at C-3 position of both pyrrole subunits are new and hence the photophysical properties of this collection of novel dipyrrins and BODIPY dyes were investigated. The dipyrrins show absorption maxima up to 596 nm and emissions of up to 677 nm. For the BODIPY series a remarkable effect of the alkoxy groups was identified, resulting in red shifts for absorptions and emissions. The compound substituted with two 2-thien-2-yl groups and a meso-C6F5 substituent shows an absorption maximum at 725 nm and emits at 754 nm and thus is a new representative of a near-IR BODIPY dye related to certain aza-BODIPYs. Our results demonstrate the influence of the alkoxy groups on the spectroscopic data and reveal the potential of 3-alkoxy-2-aryl-substituted pyrroles for the design of new fluorophores. [ABSTRACT FROM AUTHOR]

As fascinating examples of closely connected multiple π-electronic systems involving noncovalent interactions, the cooperatively interlocked [2+1]-type anion complexes of well-designed π-electronic molecules are reported. The anion-responsive π-electronic molecules investigated in this study are the boron complexes of dipyrrolyldiketones bearing arylethynyl moieties at the pyrrole α-positions. Diverse substituents were introduced at the terminal aryl moieties, thus controlling the cooperativity to form [2+1]-type complexes. Theoretical studies showed that this cooperativity was induced by effective interactions between the introduced arylethynyl moieties. The investigations of the anion-binding processes showed that the first and second bindings to the guest anion were energetically almost equivalent, indicating the fundamental and important features of the electronic states of the halide anions. Furthermore, the interlocked anion complexes, whose geometries were distorted from the orthogonal arrangements, had the racemic states of the chiral conformations, either of which was induced by ion pairing with an appropriate chiral π-electronic cation, resulting in the chiroptical property as shown by circular dichroism. [ABSTRACT FROM AUTHOR]

Similarly to polymer-supported assisted synthesis (PSAS), organic synthesis could be envisaged being performed by using zeolites, native or metal-doped, as heterogeneous catalysts. To illustrate this unprecedented Zeolite-Based Organic Synthesis (ZeoBOS), the total synthesis of acortatarin A was achieved through a novel strategy and using five out of eleven synthetic steps catalyzed by H- or metal-doped zeolites as catalysts. Notably, the formation of an yne-pyrrole intermediate with a copper-doped zeolite and the spiroketalization of an alkyne diol with a silver-doped zeolite have been developed as key steps of the synthesis. [ABSTRACT FROM AUTHOR]

A highly efficient and selective domino reaction producing valuable di- and tetrahydropyrrole-based skeletons from azidoethyl-substituted CH-acids and (thio)carbonyl compounds has been developed. By involving the additional functional groups in starting compounds into the domino reaction or postmodification of the primary reaction products, the simple construction of the pharmaceutically relevant three- and polycyclic azaheterocyclic scaffolds was demonstrated. [ABSTRACT FROM AUTHOR]

Two-component self-assembly is a promising approach to construct functional nanomaterials. Interaction of a flexible guanidiniocarbonyl pyrrole tetra-cation ( 1) with naphthalene diimide dicarboxylic acid (NDIDC) in aqueous DMSO leads to the formation of supramolecular networks. First, the carboxylate groups of NDIDC bind to the guanidiniocarbonyl pyrrole cations of 1 in a 1:2 stoichiometry. Further π-π induced aggregation then leads to 3D networks, as established by dynamic light scattering studies (DLS), NMR, fluorescence titration, viscosity measurements, AFM, and TEM microscopy. Due to ion pairing, the resulting aggregates can be switched between the monomers and the aggregates reversibly using external stimuli like protonation or deprotonation. At high concentration, a stable colloidal solution is formed, which shows an extensive Tyndall effect. Increasing the concentrations even further leads to formation of a supramolecular gel. [ABSTRACT FROM AUTHOR]

Polygon-like [2+2]- and [3+3]-type metal complexes were prepared from dipyrrin dimers connected by acute-angled spacers. The electrical conduction depends strongly on the packing alignment of the compounds, revealing the presence of effective hopping pathways for holes with relatively high mobility up to 0.11 cm2 V−1 s−1 along the aligned axis of [3+3]-type metal-bridged assemblies. These observations correlated with the geometrical control of the π-conjugated metal complexes in the cyclic structures, which enables their ordered arrangement in the assemblies. [ABSTRACT FROM AUTHOR]

Modified 3,5-dipyrrolylpyrazole (DPP) derivatives in their protonated form produce planar [2+2]-type complexes with trifluoroacetate (TFA) ions. These complexes serve as constituent components of ion-pair-based assemblies. An essential strategy for the construction of dimension-controlled organized structures based on these [2+2]-type complexes is the introduction of aryl rings bearing long alkyl chains, which enables the formation of 2D patterns at interfaces, supramolecular gels, and mesophases. [ABSTRACT FROM AUTHOR]