Electrocatalytic Annulation-Iodosulfonylation of Indole-Tethered 1,6-Enynes to Access Pyrrolo[1,2-a]indoles

We present the first example of electrocatalytic three-component annulation-iodosulfonylation of indole-tethered 1,6-enynes with arylsulfonyl hydrazides and KI for accessing various iodosulfonated pyrrolo[1,2-a]indoles in moderate to excellent yields with high stereospecificity. This electrosynthesis opens new avenues for the construction of pyrrolo[1,2-a]indoles skeleton with good functional group compatibility under environmentally benign condition. Based on the control experiments and cyclic voltammetry data, we suggested the plausible reaction mechanism which included anodic oxidation, homolysis of arylsulfonyl iodide, arylsulfonyl radical addition, 5-exo-dig cyclization, radical coupling or nucleophilic attack of iodide ions cascade.