Synthesis and structure of a new 1,2-bridged calix[6]arene

The novel 1,2-bridged calix[6]arene 5 is prepared in a cyclocondensation reaction of 1,3,5,7-tetra-tert-butyl-2,6,9-trioxabicyclo[3.3.1]nona-3,7-diene-4,8-dicarbonylchloride ('bisdioxine') 2 with p-tert-butylcalix[6] arene. Elucidation of its structure is based on an X-ray structure determination together with supporting NMR and MS investigations. The new macrocycle 5 offers good complexation properties for Cs+ ions.