Towards perfunctionalized dodecahedranes - En route toC(20) fullerene

摘要

"One-pot" substitution of the twenty hydrogen atoms in pentagonal dodecahedrane (C20H20) by OH, F, Cl, and Br atoms is explored. Electrophilic insertion of oxygen atoms with DMDO and TFMDO as oxidizing reagents ended, far off the desired C-20(OH)(20), in complex polyol mixtures (up to C20H10(OH)(10) decols, a trace of C20H(OH)(19)?). Perfluorination was successful in a NaF matrix but (nearly pure) C20F20 could be secured only in very low yield. "Brute-force" photo-chlorination (heat, light, pressure, time) provided a mixture of hydrogen-free, barely soluble C20Cl16 dienes in high yield and C20Cl20 as a trace component. Upon electron-impact ionization of the C20Cl16 material sequential loss of the chlorine atoms was the major fragmentation pathway furnishing, however, only minor amounts of chlorine-free C-20(+) ions. "Brute-force" photobrominations delivered an extremely complex mixture of polybromides with C20HBr13 trienes as the highest masses. The MS spectra exhibited exclusive loss of the Br substituents ending in rather intense singly, doubly, and triply charged C-20-H-4-0(+(2+)(3+)) ions. The insoluble similar to C20HBr13 fraction (C20Br14 trienes as highest masses) obtained along a modified bromination protocol, ultimately allowed the neat mass selection of C-20(-) ions. The C20Cl16 dienes and C20H0-3Br14-12 tri-/tetraenes, in spite of their very high olefinic pyramidalization, proved resistant to oxygen and dimerization (polymerization) but added CH2N2 smoothly. Dehalogenation of the respective cycloaddition products through electron-impact ionization resulted in C22-24H4-8+(2+) ions possibly constituting bis-/tris-/tetrakis-methano-C-20 fullerenes or partly hydrogenated C-22, C-23, and C-24 cages.