The polar cycloaddition reaction of arenesulfonyl isocyanates (1) with dialkylcarbodiimides (2) gives rise to the formation of six-membered ring cycloadducts 6 and 8. The latter compound arises from interception of an acyclic polar 1: 1 adduct by arenesulfonylalkylcarbodiimide (9), which is generated via an exchange sequence. Simultaneous cycloaddition of 1, 2, and 9 forms cycloadducts 6, 8, and 12. Cycloadduct 12 ...