Step Cyclization to Give Part Belt Oxygen-Functionalized\nPillar[6,10]arenes

Part belt oxygen-functionalized pillar[6,10]arenes\nare synthesized\nby step cyclization. An oxygen-substituted tetramer and hexamer have\nbeen prepared to construct the O3 pillar[6]arene <b>4</b> via\na hexamer cyclization reaction and the O6 pillar[10]arene <b>7</b> through a [4 + 1+4 + 1] cyclization reaction. X-ray crystallographic\nstudies reveal that both macrocycles have a large cavity and indicate\nthat the part belt oxygen-functionalized pillar[6,10]arenes have both\nsimilar cyclic structures and certain differences in configuration\ncompared to pillararene. A variable-temperature <sup>1</sup>H NMR\nexperiment also demonstrated the structure differences between O3\npillar[6]arene <b>4</b> and traditional pillararene.