Synthesis and characterization of calixarene analogs locked in the cone conformation by the dimerization of syn-dihydroxymetacyclophanes as a building block

syn-Dihydroxymetacyclophanes were converted to bridged calix[4]arene analogs by base-catalyzed condensation with formaldehyde. A remarkable template effect was observed on this condensation. Enlarged calix[4]arene analogs were synthesized by two different methods. All calix[4]arene analogs took the cone-type conformation and kept it even at high temperatures, according to the elucidation by 1H NMR spectroscopy. The acidities (pKapp) of calix[4]arene analogs, which partially form the hydrogen bonding, were medium values in the range of 5.1–5.5. Calix[4]arene analogs can transport Li+ ion considerably and show the selectivity for Li+ over Na+ ions 15 and 30 in the weak basic and neutral solutions, respectively.