Copper-free Sonogashira coupling of 2-chloroquinolines with phenyl acetylene and quick annulation to benzo[b][1,6]naphthyridine derivatives in aqueous ammonia

An efficient copper-free Sonogashira coupling of 2-chloroquinolines with phenyl acetylene to 2-ethynylquinolines is described. We further discussed the one pot facile annulation of 2-alkynylquinoline-3-carboxaldehydes to 3-phenylbenzo[b][1,6]naphthyridines in aqueous ammonia in excellent yield.