Copper-catalyzed cascade reaction: synthesis of pyrimido[4,5- b ]quinolinones from 2-chloroquinoline-3-carbonitriles with (aryl)methanamines

Cu-catalyzed cascade reaction of 2-chloroquinoline-3-carbonitriles with benzyl amines and sodium hydroxide in aerobic atmosphere has been developed for the synthesis of pyrimido[4,5- b ]quinoline-4-ones. The reaction proceeds sequentially via Ullmann-coupling and conversion of nitrile to amide followed by nucleophilic addition of amide nitrogen onto iminium carbon and air oxidation. Reagents and substrates are cheap and easily available/accessible. Plausible mechanism of reaction is also discussed.