Change of connectivity on catenane ring: ring expansion by annulation-ring scission sequence.

Ring expansion of a catenane without destruction of the interlocked structure was attained by Diels−Alder reaction followed by ozonolysis. Annulation by Diels−Alder reaction introduced a C4 fragment onto the ring, and the ozonolysis scissored the resulting double bond to expand the catenane ring. The annulation−ring scission sequence provides a general approach for changing the connectivity on a catenane ring without destroying the interlocked structure.