The direct intermolecular arylation reactions of heteroaromatic compounds such as pyrroles, furans, thiophenes, azoles, and pyridines with aryl halides using palladium or rhodium catalysts have significantly been developed as effective, straightforward methods for making aryl–heteroaryl linkages, which are often found in biologically active compounds and π-conjugated functional materials. In this article is summarized the recent progress in this field.

The reactions of iodobenzene with azole compounds, 1,2-disubstituted imidazoles and 2-substituted oxazoles and thiazoles, were examined in the presence of catalytic amounts of Pd(OAc)₂ and PPh₃ in DMF using alkali metal carbonates as bases. It was found that the coupling products, 5-arylazoles, could be selectively produced in good yields by using Cs₂CO₃. In the case that their 2-position is unsubstituted, the site could also be arylated. In reactions using bromobenzene in place of iodobenzene, K₂CO₃ was also as effective as Cs₂CO₃. The addition of a stoichiometric amount of CuI appeared to specifically promote the reactions of thiazoles as well as those of thiophene derivatives. The reactions of 2-unsubstituted azole compounds with aryl iodides could be mediated by CuI to some extent without using the palladium species to give 2-arylazoles.