The Preparation and Crystal Structures of Octaoxoketocalix[8]arene Derivatives: The Ketocalixarene Counterparts of the Largest "Major" Calixarene.

The purpose of this study was to synthesize and structurally characterize ketocalixarenes (i.e., calixarenes where the bridging methylene bridges are replaced by carbonyl groups) derived from the largest "major" calixarene, namely --butylcalix[8]arene . Ketocalix[8]arenes were synthesized by the oxidation of protected --butylcalix[8]arene derivatives. Octamethoxy-p-tert-butylketocalix[8]arene was prepared by the photochemical reaction of the calixarene with NBS in a CHCl/HO mixture. The oxidation of the methylene groups of octaacetoxy---butylcalix[8]arene was conducted by a reaction with CrO in AcO/AcOH. The basic hydrolysis of the acetate groups of the oxidation product yielded octahydroxy---butylketocalix[8]arene . In the crystal, the molecule adopts a saddle-like conformation of crystallographic and idealized symmetry. Strikingly, the array of OH/OH intramolecular hydrogen bonds present in the parent is completely disrupted in .