From Pagodanes to Homologous, Non‐Pentagonal Dodecahedranes

Abstract

Homo-and bishomododecahedral cage molecules with one and two 0 -C O (0-CH2) linkers installed into the parent pentagonal framework and featuring diverse functionalization patterns have been made available from pagodane precursors via highly expeditious synthetic sequences. The enforced geometrical changes with respect to molecular curvature, olefinic pyramidalization, transannular n,n-distance as well as to the chemical reactivity particularly of the unsaturated homododecahedranes are generally in good agreement with expectations based on calculations (MM2). In the appreciably pyramidalized monohomododecahedradjene skeleton 40 the non-parallel n-bonds are ca. 2.9 (3.1) A [(D = ca. 20 (32) O , MM21, in the bishomododecahedradiene skeleton 55 the perfectly syn-periplanar n-bonds 2.81 A apart (@ = 18.2", X-ray crystal structure).

Bromination of Unsaturated Dodecahedranes—En Route to C20 Fullerene

“…[30] On the other hand, in the MS spectra of 21 and 23 loss of N 2 and (H)Br along differing sequences produced C 21 H 16-11 ions (m/z 268-263; m/z 133), possibly indicative of potentially valence-isomeric "homododecahedrenes" such as from 23 (-Br 2 -2 HBr) the C 21 H 14 ions 27 + (2 + ) . [31] NMR/MS spectral analyses: The substitution patterns of the bromides 10-16 and 20, and the pyrazolines 21, 23, and 25 were derived from extensive l H and 13 C NMR analyses (Figure 3). The individual assignments were based on decoupling and 2D FT COSY or C/H heterocorrelation spectra with the chemical shifts reflecting the established additive increments for protons/carbons a/b-or g-positioned to CÀ Br [8] and C=C double bonds, the smaller 3 J H,H coupling constants on the flattened olefinic sides, and the pronounced solvent effects (CDCl 3 vs. C 6 D 6 ).…”

Towards Perfunctionalized Dodecahedranes—En Route to C20 Fullerene

“…[10] In fact, from exploratory experimentation it was learnt that the installation of more than 10-12 chlorine or Abstract: "One-pot" substitution of the twenty hydrogen atoms in pentagonal dodecahedrane (C 20 H 20 ) 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 C 20 H 10 (OH) 10 decols, a trace of C 20 H(OH) 19 ?). Perfluorination was successful in a NaF matrix but (nearly pure) C 20 F 20 could be secured only in very low yield.…”

“…"Brute-force" photobrominations delivered an extremely complex mixture of polybromides with C 20 HBr 13 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…”

“…Perfluorination was successful in a NaF matrix but (nearly pure) C 20 F 20 could be secured only in very low yield. "Brute-force" photochlorination (heat, light, pressure, time) provided a mixture of hydrogenfree, barely soluble C 20 Cl 16 dienes in high yield and C 20 Cl 20 as a trace component. Upon electron-impact ionization of the C 20 Cl 16 material sequential loss of the chlorine atoms was the major fragmentation pathway furnishing, however, only minor amounts of chlorine-free C 20 + ions.…”

“…As detailed in the preceding paper for oligobrominations, the comparably large increase in strain energy for vicinal disubstitutions does not exert significant steric control. [1] These aspects as well as the simultaneous worldwide efforts to (per)functionalize C 60 fullerene, the "big brother" of C 20 , had given much stimulation to our crusade. [11] Herein, we present an updated account of our activities directed at 3-6, this unique set of perfunctionalized cage molecules.…”