From calixfurans to heterocyclophanes containing isopyrazole units

Cyclic poly-1,4-diketones 2, obtained by the oxidn. of the furan units present in calix[4]furan 1a and calix[6]furan 1c have been converted into the novel heterocyclophanes 4a and 4c contg. four and six isopyrazole units, resp. Soln. studies have demonstrated the ability of 4a and 4c to act as ligands for transition metals. The crystal structures of 4a and the coordination compd. formed by 4c with 2 equiv. of cis-PtCl2(DMSO)2 have been detd. In the solid state 4c is shown to bind arom. substrates within its cavity.