Synthesis of unsymmetrical urea from aryl- or pyridyl carboxamides and aminopyridines using PhI(OAc)2via in situ formation of aryl- or pyridyl isocyanates

The synthesis of unsymmetrical ureas ( N -aryl- N ′-pyridylurea and N , N ′-bipyridylurea) from aryl- or pyridyl carboxamides and aminopyridines in the presence of PhI(OAc) 2 has been reported. The formation of pyridylisocyanates from their corresponding carboxamides via Hofmann rearrangement is confirmed.