SYNTHESIS, CONFORMATIONAL STUDIES AND INCLUSION PROPERTIES OF O-BENZYLATED CALIXARENE ANALOGS OF TRIHYDROXY[3.3.3]-METACYCLOPHANES

O-Benzylation of the flexible macrocycle 1 with benzyl bromide in the presence of NaH in THF under reflux afforded a mixture of two conforme rs of the tri-O-benzylated products, cone-2a and partial-cone-2a in a ratio of 20:80 in 80% yield. In contrast, O-alkylation of the triol 1 with 2-(chloromethyl)pyridine in the presence of NaH resulted in exclu sive formation of cone-2b. Only when the template metal can hold the 2 -pyridyl group(s) and the oxide group(s) on the same side of the [3.3. 3]metacyclophane ring, is the conformation immobilized in the cone for m. The template effect of the sodium cation plays an important role in this benzylation. The two-phase solvent extraction data indicated tha t tris(2-pyridylmethoxy)[3.3.3]metacyclophanes 2b show strong Ag+ affi nity, high Ag+ selectivity being observed for both cone-2b and partial -cone-2b. H-1 NMR Titration of cone-2b with AgSO3CF3 clearly demonstra tes that a 1:1 complex is formed with retention of the original symmet ry. The pyridine moiety underwent conformational changes upon Ag+ comp lexation with the original outward orientation of the ring nitrogen ch anging to an inside orientation toward the cyclophane cavity.