Functionalization Reactions of C16-Hexaquinacene and Related Hemispherical Molecules

Article abstract of DOI:10.1021/jo00330a001

The exhaustive hydroboration of triquinacene (8) and C16-hexaquinacene(1) has been investigated and the pair of isomeric exo-triols separated in both cases.Whereas 8 reacts with diborane to give 37percent of the C30-symmetric product 10, 1 affords an amount of 3a (28percent) closer to the statistical value of 25percent.Because difficulties were encountered in the oxidation of 3a, the utility of triketone 4 as a possible precursor of dodecahedrane was not examined further.A four-step conversion of C16-hexaquinacenedione (26a) to monoketone 29 was developed.However, this compound was exceptionally susceptible to base-promoted enolization and therefore proved unreactive to homologation reagents designed to give the cyclopentenone 31.The chemical reactivity of 26a toward phosphonate reagents was investigated, and a number of homologated derivatives , e.g., 41, 45, and 47, were prepared.However, all attempts to accomplish transannular bond formation with compounds derived from these intermediates were unsuccessful.The diamines 62a and 63a also could not be bridged.