Pentagonal dodecahedranes: Polyfunctionalization and MS fragmentation

With the use of four- to eight-fold functionalized dodecahedranes (1-3), op portunities to arrive at highly strained dodecahedranes with two to four pa irs of vicinal, eclipsed bromine substituents through front-side substituti on and addition reactions have been explored. In standard processes, the in terception of beta -OCH3 radical/cationic intermediates was not problematic (9-12, 37, 50). The interception of beta -CO2R radicals was possible for C l-. (18) but not for Be (17). The interception of beta -chloro radicals was possible for Cl-. (27) but not for Br-. (26), and the interception of beta -Br cations ("bromonium ions") with Br- was modest (45) to highly ineffici ent (24, 26). Two X-ray structural analyses (dimethoxy dibromide 9 and tetr amethoxy tetrabromide 53) indicated the structural consequences of the mole cular strain introduced by the two (four) vicinal CH3O/Br pairs. A systemat ic analysis of the MS spectra confirms that, in virtually all cases studied , the elimination of the substituents occurs without significant carbon-cag e disruption, leading ultimately to multiply unsaturated dodecahedral ions for dodecahedrahexa(C2OH8)enes, -hepta(C20H6)enes, and -octa-(C20H4)enes.