Iodine-Catalyzed Synthesis of Fused Tetracyclic Pyridazino[6,1-b]pyrrolo[1,2-a]quinazolin-9(1H)-one Derivatives via a Tandem Reaction.

Abstract A facile and general method for the synthesis of pyridazino[6,1-b]pyrrolo[1,2-a]quinazolin-9(1H)-one derivatives via a reaction of 2-aminobenzohydrazide and 1,7-dichloro-heptan-4-one catalyzed by iodine in the presence of excess NaHCO3 is described. This is a tandem reaction to construct three new rings and a chiral quaternary carbon center in one-pot procedure. Two possible pathways in the formation of the second heterocycle are proposed, and they are confirmed by the key intermediates of pyrrolo[1,2-a]quinazolin-5(1H)-ones which are selectively obtained via controlling the ratio of base.