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

[GRAPHICS] Ring expansion of a catenane without destruction of the interlocked structu re was attained by Diels-Alder reaction followed by ozonolysis. Annulation by Diels-Alder reaction introduced a C4 fragment onto the ring, and the ozo nolysis scissored the resulting double bond to expand the catenane ring. Th e annulation-ring scission sequence provides a general approach for changin g the connectivity on a catenane ring without destroying the interlocked st ructure.