Pentagonal dodecahedranes. Novel substitution patterns— MS fragmentation and unsaturation
| Autor: | Klaus Scheumann, Jürgen Wörth, Emmerich Sackers, Martin Bertau, Horst Prinzbach, Jürgen Leonhardt, Hans Fritz, Dieter Hunkler |
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| Rok vydání: | 1998 |
| Předmět: | |
| Zdroj: | Journal of the Chemical Society, Perkin Transactions 2. :1195-1210 |
| ISSN: | 1364-5471 0300-9580 |
| Popis: | 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 C20 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 Br2. In the latter case, by a sequence of Br+ addition/HBr elimination steps, up to nine vicinally placed bromine substituents were implanted upon the C20 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 CC double bonds. |
| Databáze: | OpenAIRE |
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