A new synthesis of fused oxa- and thiacrown ethers-thiophene/furan oligomers

We have developed a two-step sequence for preparing a series of macrocyclic oxa- and thiacrown ethers affixed to a thiophene/furan oligomer. The sequence involves the intramolecular MnIII-promoted cyclization of linear diester precursors into 2,3-dihydrofurans, whose dehydrogenation furnishes the title compounds. A preliminary NMR study has shown that one of them seems to specifically chelate Pb2+ cations