Addition of ArSSAr to dienes via intramolecular C-C bond formation initiated by a catalytic amount of ArS+

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.