USE OF PYRIDINE N-OXIDE AND PYRIDINIUM ION SYNTHONS IN THE PREPARATION OF OLIGOPYRIDINES - 2 NEW UNSYMMETRICAL QUATERPYRIDINES WITH 2,2'-BIPYRIDINE UNITS

Isomeric quaterpyridines 1 and 2 were prepared. They formally represen t the coupling of two 2,2'-bipyridine units at their 4' and 5' positio ns of the B ring to the 2'' position of the C ring. N-Oxidized and N-m ethylated bipyridine synthons served to introduce halogen regiospecifi cially prior to Pd(O)-catalyzed cross-coupling with a 2-pyridylstannan e.