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The palladium-catalyzed direct arylation of azoles with (hetero)aryl halides is nowadays one of the most versatile and efficient procedures for the selective synthesis of heterobiaryls. Although this procedure is, due to its characteristics, also of great interest in the industrial field, the wide use of a reaction medium such as DMF or DMA, two polar aprotic solvents coded as dangerous according to environmental, health, safety (EHS) parameters, strongly limits its actual use. In contrast, the use of aromatic solvents as the reaction medium for direct arylations, although some of them show good EHS values, is poorly reported, probably due to their low solvent power against reagents and their potential involvement in undesired side reactions. In this paper we report an unprecedented selective C-5 arylation procedure involving anisole as an EHS green reaction solvent. In addition, the beneficial role of benzoic acid as an additive was also highlighted, a role that had never been previously described.

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 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]

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