Palladium-catalysed Heck alkynylation of aryl bromides in an imidazolium ionic liquid: An unexpected subsequent alkyne hydrogenation reaction

Article abstract of DOI:10.1055/s-2006-951503

The copper-free palladium-catalysed alkynylation of aryl bromides with phenylacetylene in the imidazolium ionic liquid [BMIM][BF₄], in the presence of triphenylphosphine ligand and pyrrolidine as a base, was found effective and significantly more chemoselective employing deactivated substrates. When activated aryl substrates were used, unexpected side reactions were observed, especially the subsequent hydrogenation of the alkyne function in some coupling products. In other cases, amine arylation reactions occurred, as illustrated by the formation of pyrrolidinyl-4-nitrobenzene, for which an X-ray diffraction structure is reported. Georg Thieme Verlag Stuttgart.