Synthesis of Halogenated Terpyridines and Incorporation of the Terpyridine Nucleus into a Polyetheral Macrocycle

Article abstract of DOI:10.1021/jo00356a019

Two synthetic approaches to haloterpyridines are herein described.The first method involved direct halogenation of terpyridine N-oxides with POCl3 to generate a mixture of polyhalogenated terpyridines.A more efficient approach to 6,6''-dibromo-2,2':6',2''-terpyridine utilized the Kroehnke synthesis to form the terpyridine moiety from appropriately halosubstituted precursors.Direct nucleophilic substitution on terpyridine was found to give low yields of macrocyclic products; however, if 1,5-bis(6-bromo-2-pyridyl)-1,5-dioxopentane was employed, macrocyclization afforded improved yields of the desired terpyridines.