A catalytic amount of electrochemically generated “ArS⁺” (“ArS⁺” = ArS(ArSSAr)⁺) initiates a cation chain reaction of dienes that involves the addition of ArSSAr associated with stereoselective intramolecular carbon–carbon bond formation, and the direct (in-cell) electrolysis of a mixture of a diene and ArSSAr with a catalytic amount of electricity also effectively initiates the reaction.