Palladium-Catalyzed Arylation of Azole Compounds with Aryl Halides in the Presence of Alkali Metal Carbonates and the Use of Copper Iodide in the Reaction

Article abstract of DOI:10.1246/bcsj.71.467

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 Cul 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 Cul to some extent without using the palladium species to give 2-arylazoles.