6,6′-Dimethyl-2,2′-bipyridine-4-ester: A pivotal synthon for building tethered bipyridine ligands

Abstract We describe an efficient and scalable synthesis of 4-carbomethoxy-6,6′-dimethyl-2,2′-bipyridine starting from easily available substituted 2-halopyridines and based on the application of modified Negishi cross-coupling conditions. This compound is a versatile starting material for the synthesis of 4-functionalized 2,2′-bipyridines bearing halide, alcohol, amine, and other functionalities, suitable for conjugation to biological material ( 2a – c , 3a – g ). The utility of this compound in the construction of more complex architectures was further demonstrated by the synthesis of two bifunctional lanthanide chelators; an open chain ligand based on one 2,2′-bipyridine unit and a cryptand based on three 2,2′-bipyridine units [N 2 (bpy) 3 COOMe]. In the field of luminophoric biolabels, the photophysical properties of the corresponding Eu(III) cryptate are reported.