Synthesis of Unsymmetrically Substituted Bipyridines by Palladium-Catalyzed Direct C-H Arylation of Pyridine N-Oxides

Substituted bipyridines were efficiently prepared by direct coupling between pyridine N-oxides and halopyridines using a palladium catalyst. Pyridine N-oxides with electron-withdrawing substitutents gave the best yields. This method allows the convenient preparation of 2,2'-, 2,3'-, and 2,4'-bipyridines which are useful as functionalized ligands for metal complexes or as building blocks for supramolecular architectures.