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 analog s by base-catalyzed condensation with formaldehyde. A remarkable template e ffect was observed on this condensation. Enlarged calix[4]arene analogs wer e 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 H-1 NMR spectroscopy. The acidities (pKapp) of calix[4]a rene 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 consi derably and show the selectivity for Li+ over Na+ ions 15 and 30 in the wea k basic and neutral solutions, respectively. (C) 2001 Elsevier Science Ltd. All rights reserved.