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A selective direct arylation of the different Csp2‐H bonds of imidazo[2,1‐b]thiazole with (hetero) aryl halides can be achieved simply by switching from a palladium catalyst system to the use of stoichiometric amounts of copper. The observed selectivity, also rationalized by DFT calculations, can be explained by a change in the mechanistic pathways between electrophilic palladation and base‐promoted C−H metalation. [ABSTRACT FROM AUTHOR]

An effective Pd(II)/Ag(I)‐promoted intramolecular cross‐dehydrogenative coupling (CDC) of substituted 1‐benzylimidazoles under air provides, for the first time, a simple access to several functionalized imidazo[2,1‐a]isoindoles, an interesting class of polycyclic heteroaromatic compounds. The direct involvement of two unactivated carbon–hydrogen bonds, without any directing group, grants an elevated atom economy of the whole process. [ABSTRACT FROM AUTHOR]

Tetrasubstituted 1H-imidazoles are a large family of heteroarene derivatives that are known to include natural products isolated from marine sponges and synthetic compounds possessing a broad range of biological and pharmacological properties. Consequently, a great deal of attention has been given to the synthesis of these heteroarenes and reviews covering some synthetic aspects of this topic have been published in recent years. However, none of these reviews provides a comprehensive overview of the catalytic methods developed in the literature for the preparation of this important class of heteroarenes. This article aims to provide an updated critical picture of the catalytic processes reported in the literature up to the end of 2017 for the synthesis of 1,2,4,5-tetrasubstituted 1H-imidazoles illustrating these protocols and their characteristic features such as scope, efficiency, versatility, and limitations. The review also summarizes the mechanisms proposed for many of the reported processes. [ABSTRACT FROM AUTHOR]

A new hole-transport material (HTM) based on the 1,3,4-oxadiazole moiety (H1) was prepared through a single-step synthetic pathway starting from commercially available products. Thanks to a deep HOMO level, H1 was used as HTM in CH3NH3PbBr3 perovskite solar cells yielding an efficiency of 5.8 %. The reference HTM (Spiro-OMeTAD), under the same testing conditions, furnished a lower efficiency of 5.1 %. Steady-state and time-resolved photoluminescence of the thin films showed good charge-extraction dynamics for H1 devices. In addition, H1 shows a large thermal stability and completely amorphous behavior (as evaluated by thermal gravimetric analysis and differential scanning calorimetry). [ABSTRACT FROM AUTHOR]

In recent years, environmental and economic reasons have motivated the development of transition metal-free carbon-carbon bond forming reactions and some excellent reviews have covered this research area of particular interest for the pharmaceutical industry. However, none of these reviews has been specifically dedicated to summarize and discuss the results achieved in the rapidly growing field of the transition metal-free direct (hetero)arylation reactions of heteroarenes. This review, which covers the literature from 2008 to 2014, aims to provide a thorough insight into the synthetic and mechanistic aspects of these atom economic and environmentally benign reactions also highlighting their advantages and possible disadvantages compared to conventional methods for the synthesis of arylheteroarenes and biheteroaryls via transition metal-catalyzed reactions. [ABSTRACT FROM AUTHOR]

A series of 1,4-phenylene-spaced bis-imidazoles with fluorescence quantum yields up to 0.90 and large Stokes shifts have been designed and synthesized using recently developed regioselective direct CH arylation protocols. All the fluorophores show a bright blue-green emission that is well retained in the solid state. DFT calculations attributed their excellent luminescence properties to the significant planarization of the molecules in the equilibrium structures of their excited electronic states. [ABSTRACT FROM AUTHOR]

In recent years, transition metal-catalyzed direct (hetero)arylation reactions of heteroarenes with (hetero)aryl halides and pseudohalides have received significant attention as eco-friendly and economic alternatives to classical methods for the construction of heteroaryl-(hetero)aryl CC bonds by transition metal-catalyzed cross-couplings involving the use of stoichiometric amounts of organometallic reagents. This critical review with 430 references covers the results obtained in the period January 2009 to February 2013 in the area of the transition metal-catalyzed direct inter- and intramolecular (hetero)arylation reactions of heteroarenes containing one heteroatom. Particular attention has been given to illustrate chemo- and site selectivity aspects of these reactions as well applications of these CC bond forming reactions in the synthesis of pharmaceutically relevant compounds, natural products and their analogues and precursors. The most recent advancements into the mechanism(s) of these reactions have also been briefly reported. [ABSTRACT FROM AUTHOR]

A mild, general, and convenient palladium-catalyzed direct arylation of the 5-position of azoles with aryl bromides, efficiently promoted by tetrabutylammonium acetate, is described. 1-Methylpyrazole, oxazole, and thiazole reacted at 70 °C in N, N-dimethylacetamide by using Pd(OAc)2 as the catalyst precursor. Electron-poor and -rich functional groups, including the free hydroxy group, are well tolerated in the electrophilic partner. A variety of 5-aryl-1-methylimidazoles were also very efficiently obtained simply by raising the reaction temperature to 110 °C. This ligand-free protocol was successfully applied to the one-pot synthesis of two bioactive natural compounds, balsoxin and texaline, starting from oxazole by sequential direct arylation of the 5- and 2-positions. [ABSTRACT FROM AUTHOR]

The possibility of exploiting supramolecular architectures for the preparation of innovative mechanochromic devices has been extended by designing novel thienyl-substituted 1,4-bis(ethynyl)benzene dyes, which are characterized by a conjugated, rigid, rodlike core structure. This new family of chromophores was synthesized according to a simple two-step sequential cross-coupling reaction, and the optical properties were investigated in solution and in a polymeric matrix. To tune the mechanochromic performances in smart polymer materials, a virtual screening was set up that was able to select a derivative with optimal spectral features. The effective combination of experimental and computational investigations allowed us to spot those homologues with already potential anisotropic and aggregachromic features and characterized by the best spectral properties and luminescent response. The best candidate was synthesized and dispersed into a polyethylene matrix, indeed achieving an 'in silico designed' mechanochromic material. Besides the specific applications of this novel material, the integration of computational and experimental techniques reported here defines an efficient protocol that can be applied to make a selection among similar dye candidates, which constitute the essential responsive part of such supramolecular devices. [ABSTRACT FROM AUTHOR]

Review: [175 refs. [ABSTRACT FROM AUTHOR]

The article presents chemical equations related to the article "Highly Regioselective C-5 Alkynylation of Imidazoles by One-Pot Sequential Bromination and Sonogashira Cross Coupling" by F. Bellina and others, published in the periodical "Tetrahedron Letters" in 2015.

A simple and efficient method to prepare several 5-arylated azoles is presented. [ABSTRACT FROM AUTHOR]

Symmetrical and unsymmetrical diarylethynes can be readily prepared; sterically hindered bromides and base-labile functional groups are tolerated. [ABSTRACT FROM AUTHOR]