Bridging of Bipyridine Units by Phenylphosphine Links: Linear and Cyclic Oligomers and Some Acid Derivatives

Reaction of 6,6‘-dibromo-2,2‘-bipyridine with phenylphosphine under palladium-promoted cross-coupling conditions provides a variety of linear oligomers bearing two reactive bromo substituents
as well as a cyclic dimer, characterized by X-ray crystallography, in which the bipyridine units are
constrained to a cis configuration by two phenylphosphine oxide bridges. Derivatives of the linear
species containing both carboxylate and phosphonate substituents are readily obtained.