Cu(I)-Catalyzed and Base-Promoted [5 + 2 + 1] Cascade Cyclization of 2-Nitrochalcones with Aliphatic Primary Amines to 5 H -Pyrimido[5,4- b ]indole Frameworks.

An unprecedented [5 + 2 + 1] cascade cyclization to the preparation of 5 H -pyrimido[5,4- b ]indole derivatives has been disclosed. The novel protocol of 2-nitrochalcones reacted with aliphatic primary amines catalyzed by CuI and promoted by Cs 2 CO 3 , which underwent a critical intermediate 2,3-disubstituted indole, providing structurally diverse 5 H -pyrimido[5,4- b ]indoles in generally high yields (77-90%) and broad substrate scopes (34 examples).