Palladium(0)-catalyzed coupling of organozinc iodide reagents with bromopyridines: synthesis of selectively protected pyridine-containing azamacrocycles

The synthesis of azamacrocycles in which the ring nitrogens are regioselectively functionalized is described. An organozinc palladium(0)-catalyzed coupling with an appropriately functionalized bromopyridine generated a key intermediate, which was transformed in two steps to a desired precursor and subjected to an intramolecular N-alkylation to effect a macrocyclization affording selectively protected azamacrocycles 1-3.