Topologically Spherical Molecules. Transannular and Other Rearrangement Reactions of Dihomodioxatrisecododecahedranes

Article abstract of DOI:10.1021/jo01303a022

With the availability of 4a,8a-dimethyloctadecahydro-3,7-dioxadicyclopentapentaleno<2.1.6-hia:5,4,3-h'i'a'>diindene-4,8-dione (5), it has been possible to determine the relative ordering of three reactions experienced by potential dodecahedrane precursors of this general type.Direct ring opening of the lactone rings in 5 with Meerwein's reagent proceeds only at more elevated temperatures and only with subsequent prototropic shift.In contrast, the derived dilactol 9 and hemiacetal 10 are particularly prone to transannular hydride shifting and neighboring-group involvement of the ether oxygen.The proposed mechanism was confirmed by a suitable deuterium-labeling experiment.Further indications of the factors controlling ring opening were obtained from ether lactone 11, from which the C₂ symmetric dihomodioxatrisecododecahedrane 23 could be prepared as well.The collective results indicate the chemical reactivity of these compounds to be controlled in large part by energetic and stereoelectronic factors recognized to be operative in simpler systems.Quite apparent is a substantial kinetic inducement for bond making within the solvent-free cavities of these highly spherical molecules.