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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]

An efficient synthesis of symmetrical 1,2-disubstituted 4,5- dialkynylimidazoles by Sonogashira alkynylation of the corresponding 4,5-dibromo derivatives was developed. Moreover, through a careful tuning of the palladium ligand, unsymmetrical 1,2-disusbtituted 4,5-dialkynylimidazoles were also prepared through a regioselective C5 alkynylation of 4,5-dibromoimidazoles, followed by a second alkynylation involving the 4-bromo derivatives so obtained. This interesting class of imidazole-fused enediynes is also able to give thermal Bergman cycloaromatization (BC), as proved by DSC experiments. [ABSTRACT FROM AUTHOR]

Two methods for the one-pot synthesis of 2,5-diarylimidazoles by palladium-catalyzed direct C--H arylation of 1-substituted imidazoles with aryl bromides have been devised. The first method, promoted by copper(I) iodide, is best suited for electron-poor aryl bromides, and also allows the 2,5-diarylation of thiazole and oxazole. The use of xylene instead of DMA is the key for the efficiency of the second method, which gives the best results with electron-rich aryl bromides. [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]

A variety of 2-substituted 5-alkynyl-1 H -imidazoles were easily prepared by a one-pot sequential procedure involving a highly regioselective electrophilic C-5 bromination of 1,2-dimethyl-1 H -imidazole, 2-chloro-1-methyl-1 H -imidazole, and 2-aryl-1-methyl-1 H- imidazoles, followed by an efficient palladium/copper co-catalyzed Sonogashira-type alkynylation. [ABSTRACT FROM AUTHOR]

The construction of carbon–carbon bonds by direct involvement of two unactivated carbon–hydrogen bonds, without any directing group, ensures a high atom economy of the entire process. Here, we describe a simple protocol for the Pd(II)/Cu(II)-promoted intermolecular cross-dehydrogenative coupling (CDC) of 5-arylimidazoles, benzimidazoles, benzoxazole and 4,5-diphenylimidazole at their C-2 position with functionalized styrenes. This specific CDC, known as the Fujiwara–Moritani reaction or oxidative Heck coupling, also allowed the C-4 alkenylation of the imidazole nucleus when both 2 and 5 positions were occupied. [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.

Novel trans-restricted analogues of resveratrol in which the C–C double bond of the natural derivative has been replaced by diaryl substituted imidazole analogues have been designed. The syntheses of 1,4-, 2,4-, and 2,5-diarylimidazoles, in which the two aryl moieties are linked to the heteroaromatic core in a 1,3 fashion in order to preserve the trans stereochemistry, have been successfully carried out by regioselective sequential transition metal-catalyzed arylations of simple, commercially available imidazole precursors. The anticancer activity of selected analogues has been evaluated in vitro against the NCI-60 human tumor cell lines panel. From this screening, we were able to select a synthetic candidate that resulted more active than its natural lead. [ABSTRACT FROM AUTHOR]

We report on the synthesis of new push-pull imidazole-benzothiazole and thiazole-benzothiazole fluorophores obtained in good yields by using direct C H arylation synthetic strategies. Spectroscopic investigations in CHCl 3 solution evidenced that the 1,4-phenylene-spaced imidazole-benzothiazole bearing an electron-donating dimethylamino group achieved a trade-off between fluorescence maximum (516 nm), Stokes shift (165 nm) and a quantum yield higher than 0.4. Dispersions of the selected fluorophore in poly (methyl methacrylate) (PMMA) thin films mostly maintained the optical features in solution with significant light transmittance in the visible region (90% at 440 nm), and a brilliant green emission at 500 nm. Photocurrent experiments performed on PMMA thin films coated over high purity transparent glasses promoted their use in the development of colourless luminescent solar concentrators with optical efficiencies close to 6%. [ABSTRACT FROM AUTHOR]