From calixfurans to heterocyclophanes containing isopyrazole units

Cyclic poly-1,4-diketones 2, obtained by the oxidation 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 containing four and six isopyrazole units, respectively. Solution studies have demonstrated the ability,of 4a and 4c to act as ligands for transition metals. The crystal structures of 4a and the coordination compound formed by 4c with 2 equiv. of CiS-PtCl2(DMSO)(2) have been determined. In the solid state 4c is shown to bind aromatic substrates within its cavity. (C) 2003 Elsevier Ltd. All rights reserved.