For two- to six-fold functionalised dodecahedranes (7–10) the chances for selective variation of their substitution have been explored, as part of a program directed at homododecahedranes and at highly unsaturateddodecahedranes, ultimately C20fullerene. With 1,6-dimethyl ester 7 several side chain transformations next to the very bulky dodecahedral cage were effected (1,6-bismethylene derivatives
generally in polyunsaturated dodecahedranes (in the extreme C(20)H(4), "tetrahydro-C(20) fullerenes"). Only subsequently did skeletal fragmentations occur. From X-ray crystal-structure analyses, more information was obtained on the structural response of the dodecahedral skeleton to the strain induced by the voluminous substituents. As Appendix, the forcing radical bromination of 1,6-dibromododecahedrane
The pagodane route to dodecahedranes-functional group manipulations on the dodecahedrane sphere
作者:Klaus Scheumann、Fabian Wahl、Horst Prinzbach
DOI:10.1016/s0040-4039(00)92325-6
日期:1992.1
Reductive and halogenative Barton decar☐ylation methodologies provide an expeditious access to variously 1,6-di- and 1,6,11,16-tetrasubstituted pentagonal dodecahedranes. Vicinal CO2R and Cl substituents cause increasing competition in the radical transfer step.
The highly pyramidal, highly strained 1,4,16-dodecahedratriene (4) and C20H12 1,4,10(14),16-dodecahedratetraene (5) are cage olefins with an intriguing "inner life". For 5 DFT calculations give information about the energetic and geometrical consequences of one-/two-electron oxidation and reduction. Attempts to prepare 4 and 5 through thermal retro[2+2]/[4+2]cycloaddition strategies proved unsuccessful. Still, the C20H14/C20H12 cage cations and anions are liberated upon electron impact or gas-discharge ionization of their thermally extremely stable tris-/tetrakisanthraceno-anellated derivatives. Mass-selection (photoelectron (PE) characterization) of the anions failed, however, due to the very small anion intensity, the preferential formation of hydrogen-poor ions, and minor cage disruption.
From Pagodanes to Dodecahedranes - Search for a Serviceable Access to the Parent (C 20 H 20 ) Hydrocarbon ** **Dedicated to Professor W. von E. Doering on the occasion of his 80th birthday. H.P. very fondly remembers his two post-doc years at Yale University (1957–59).
novel SN2 pagodane → dodecahedrane routes a preparatively potent access to the parent pentagonal dodecahedrane (2) was explored. The one-pot catalytic procedure (Pd/C/H2) starting from an eightfold functionalized secopagodane (14, C20H12Br6 (CO2 CH3)2) excells in shortness but, rather erratic (33–53%), falls out of the competition. The longer route via 1,6-dicarboxyl/dibromo dodecahedranes (35, 22)