Synthesis of 'macrocycle of macrocycles' containing 3 ~ 8 calix[4]arene units. Unexpected generation of large super-macrocycles

A new class of calixarene-based macrocycles consisting of three to eight calix[4]arene subunits has been prepared from starting 5,11,17,23-tetra-tert-butyl-25,27-dihydroxy-26,28-dipropoxycalix[4]are ne. The macrocyclization has been achieved by direct alkylation with 1,6-dibromohexane in DMF in the presence of NaH or via appropriate intermediates. Thus, the starting compound was transformed into bis-calix[4]arenes bearing two bromoalkyl substituents or two hydroxyl groups in positions suitable for further cyclization. By the mutual reactions of the above noticed compounds supermacrocycles containing 3, 4, 6, and 8 calix[4]arene subunits connected by hexamethylene chains have been prepared and characterized. This is a novel strategy to design a 'macrocycle of macrocycles'.