The reaction of biphenylene with various nitriles in the presence of catalytic amount
of [Rh(cod)2BF4]/dppe under microwave irradiation afforded 9-substituted phenanthridines. The reaction
with alkyl and aromatic nitriles provided the corresponding 9-substituted phenanthridines
in 26–79% isolated yields. The reaction was also carried out with cyanopyridines and
it provided heterocyclic compounds with the bipyridine and terpyridine scaffold. The
synthesized bipyridine and terpyridine were complexed with [Rh(cod)Cl]2. The former provided a Rh(III) complex in which the cyclooctadiene moiety was oxidized
to the tetrahydrofuran ring, whereas the latter gave a structurally fluxional complex
(in solution) with only one pyridine ring coordinated to the rhodium atom.
Key words
C–C bond cleavage - rhodium - phenanthridine - catalysis - cycloaddition