Unusual iodination of arylsulfonylallenes

Arysulfonylallenes (ArSO₂–CR¹=C=CR²R³), depending on their structure, react with iodine to give two types of products, diiodo alkenes ArSO₂–CHI–CI=CR²R³, when R¹=H, or iodo dienes ArSO₂–CR¹=CI–C(Me)=CH₂, when R¹=Br, Ph and R²=R³=Me, in yields of 55–98%. The plausible reaction mechanisms have been proposed.