Synthesis of 4,4′-Bipyridines via a Simple Dimerization Procedure

Significance

Polyhalogenated 4,4′-bipyridines were synthesized in a single step starting from ­dihalopyridines. A mechanism is proposed on the basis of experiments performed with 2-chloro-5-bromopyridine. When LDA was used, the corresponding dimer containing two chlorine and two bromine atoms was formed predominantly accompanied by several byproducts whose structures and mechanism of formation are discussed.