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- Title
Thermal Reactivity of Neutral and Oxidized Ferrocenyl-Substituted Enediynes.
- Authors
Cinar, Mehmet Emin; Morbach, Guido; Schmittel, Michael
- Abstract
The coupling of two equivalents of ethynylferrocene (2) with one equivalent of 1,2-diiodocyclohexene (1) and 1,2-diiodobenzene (4) using Sonogashira cross-coupling conditions led to 1,2-bis(ferrocenylethynyl)cyclohexene (3) and 1,2-bis(ferrocenylethynyl) benzene (5), respectively. At high temperatures enediynes 3 and 5 showed exothermic signals in differential scanning calorimetry (DSC) measurements, suggestive of intramolecular diradicaloid ring formation (Bergman (C¹-C6) or Schreiner-Pascal (C¹-C5) cyclizations). The oxidation of 3 and 5 to the mono-oxidized enediynes 3+ and 5+ decreased the onset temperatures drastically. Equally, 1-ferrocenylethynyl-2-(p-nitrophenyl) ethynylbenzene (8) displayed a significant decrease in the onset temperature after oxidation to 8+. Because the insoluble nature of the polymeric material formed in the thermolysis of the oxidized enediynes prevented characterization, the origin of this drastic effect was studied by DFT. Contrary to expectations, one-electron oxidation does not lower the barrier for intramolecular cyclization. Rather, the computations suggest that the polymerization is initiated by a bimolecular process.
- Subjects
ENEDIYNES; FERROCENE; THERMAL analysis; THERMAL electrons; DIFFERENTIAL scanning calorimetry
- Publication
Molecules, 2014, Vol 19, Issue 11, p18399
- ISSN
1420-3049
- Publication type
Article
- DOI
10.3390/molecules191118399