Synthesis of\nBiheteroaryls by Pd-Catalyzed Homocoupling\nof Heteroaryl Bromides

Symmetrical biheteroaryl compounds, such as bypyridines\nand bipyrazoles,\nare important ligands in transition-metal catalysis. They also serve\nas synthetic precursors of photo catalysts/sensitizers, bioactive\nagents, and energetic materials. To facilitate the concise synthesis\nof these useful structures, an efficient Pd-catalyzed homocoupling\nof heteroaryl bromides has been successfully established using the\nelectron-rich and sterically hindered monophosphorus ligand BIDIME.\nThe coupling protocol features a tandem Miyaura borylation/Suzuki\ncoupling sequence and exhibits unprecedented tolerance of a wide range\nof heteroaryl bromides, providing a series of symmetrical biheteroaryls\nin moderate to good yields. Notably, the use of the corresponding\npolymeric ligand, PolyBIDIME, enabled the recycling of a palladium\ncatalyst, demonstrating the potential of the homocoupling in practical\napplications.