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

[GRAPHICS] 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.