A simple and facile synthesis of tricyclic-fused pyrimido[4,5-b]indol-2-amines

In the present investigation, a simple and facile synthetic strategy for the construction of a series of structurally interesting tricyclic-fused N-alkyl-9H-pyrimido[4,5-b]indol-2-amines has been successfully achieved. Our synthesis, based on the annulation reaction between readily available 2-chloroindole-3-carbaldehydes or 3-acetyl-2-chloroindoles and guanidine nitrate using KOH as the base in refluxing EtOH medium, has the attractive features such as mild and economical reaction conditions and easy handing with lesser impact on the environment.