SYNTHESIS AND INCLUSION PROPERTIES OF TETRAKIS[(2-PYRIDYLMETHYL)OXY]HOMOCALIX[4]ARENES

An attempted O-alkylation of the flexible macrocycle 2 with 2-(chlorom ethyl)pyridine in the presence of NaH under THF reflux gave only one p ure stereoisomer cone-4, while other possible isomers were not observe d. Similar reaction was carried out in the presence of Cs2CO3 to yield a mixture of three conformers of tetra-O-alkylated product 4 in a rat io of 65:30:5 (cone-4: partial-cone-4: 1,4-alternate-4) in quantitativ e yield. Only when the template metal can hold the 2-pyridyl group(s) and the oxide group(s) on the same side of the [3.1.3.1]metacyclo-phan e the conformation is immobilized to the cone. The template effect of the sodium cation plays an important role in this alkylation reaction. The structural characterization of these products is also discussed. The two-phase solvent extraction data indicated that tetrakis[(2-pyrid ylmethyl)oxy]metacyclophanes 4 show strong Ag+ affinity and the high A g+ selectivity was observed for cone-4. (HNMR)-H-1 Titration of cone-4 with AgSO3CF3 clearly demonstrates that a 1:1 complex is formed which is stable on the NMR time scale.