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

Part belt oxygen-functionalized pillar[6,10]arenes are synthesized by step cyclization. An oxygen-substituted tetramer and hexamer have been prepared to construct the O3 pillar[6]arene <b>4</b> via a hexamer cyclization reaction and the O6 pillar[10]arene <b>7</b> through a [4 + 1+4 + 1] cyclization reaction. X-ray crystallographic studies reveal that both macrocycles have a large cavity and indicate that the part belt oxygen-functionalized pillar[6,10]arenes have both similar cyclic structures and certain differences in configuration compared to pillararene. A variable-temperature ¹H NMR experiment also demonstrated the structure differences between O3 pillar[6]arene <b>4</b> and traditional pillararene.