Molecular Waterwheel (Noria) from a Simple Condensation of Resorcinol and an Alkanedial

Abstract

A wheel surprise: Reaction of resorcinol and 1,5-pentanedial in ethanol at 80 °C for 48 h in the presence of HCl surprisingly afforded a soluble cyclic oligomer in high yield (83 %) under thermodynamic control. Single-crystal X-ray analysis revealed a waterwheel-like structure with a large hydrophobic hole through the center (see picture). A carboxylic ester derivative of the compound was shown to be highly selective for Rb+ ions.