Pentagonal dodecahedranes. Novel substitution patterns - MS fragmentation and unsaturation

• Published in: Journal of the Chemical Society, Perkin Transactions 2 no. 5; pp. 1195 - 1210
• Main Authors: Scheumann, K, Sackers, E, Bertau, M, Leonhardt, J, Hunkler, D, Fritz, H, Worth, J, Prinzbach, H
• Format: Journal Article
• Language: English
• Published: CAMBRIDGE Royal Soc Chemistry 1998
• Subjects: Chemistry; Chemistry, Organic; Chemistry, Physical; Physical Sciences; Science & Technology; ELECTROPHILIC ADDITION; CYCLIZATIONS; STABILITY; REACTIVITY; PAGODANE ROUTE; STRAIN ENERGIES; CATION; STABLE CARBOCATIONS; BRIDGEHEAD OLEFINS; MOLECULES
• ISSN: 1472-779X; 0300-9580; 1364-5471
• DOI: 10.1039/a709107i

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 unsaturated dodecahedranes, ultimately C-20 fullerene. With 1,6-dimethyl ester 7 several side chain transformations next to the very bulky dodecahedral cage were effected (1,6-bismethylene derivatives 25-31). In changing environments, Barton-type halogenative/hydrogenative decarboxylations (15-17, 38, 49, 59, 60, 77) as well as various nucleophilic substitutions (18, 20, 23, 39, 61-64) were achieved, mostly with good to high efficiency and retention of the substitution patterns. For the cage olefins 8/9 and the diepoxide 10, front-side cis-1,2-addition faced only slight competition in the reactions with HBr and CF3CO2H, but was only a minor pathway in the reaction with Br-2, In the latter case, by a sequence of Br+ addition/HBr elimination steps, up to nine vicinally placed bromine substituents were implanted upon the C-20 skeleton. The fate of variously functionalised dodecahedranes upon electron impact was studied-the competition between external (C-X/Y) and internal (C-C) bond cleavage was found to be typically dependent on the nature and relative orientation of the functionalities (X,Y) involved. There is good evidence that ions between m/z 242 (C20H2) and 256 (C20H16) resulting from the elimination of the respective Br, CO2CH3, CO2NH2, OCOCF3 substituents represent unsaturated dodecahedranes with up to nine C=C double bonds.