Iodine-Catalyzed One-Pot Multicomponent Synthesis of Pyrrolo/indolo[1,2-a]quinoxalines Substituted with Ortho-Carbonyl Alkyl Benzoates/Benzoic Acids Via Spirocyclic Ring Opening

An efficient iodine-catalyzed cascade coupling protocol was developed for the synthesis of tetracyclic and pentacyclic pyrrolo[1,2-a] quinoxaline and indolo[1,2-a]quinoxaline derivatives via Iodine-mediated oxidative Pictet-Spengler reaction of 2-(1H-pyrrol-1-yl)aniline, 2-(1H-indol-1-yl)aniline with ninhydrin followed by spirocyclic ring-opening with alcohol/ water. The target compounds were obtained in good-to excellent yields with a broad substrate scope