Sigmatropic Shiftamers: Fluxionality in Broken Ladderane Polymers
Dean J. Tantillo Dr.
Department of Chemistry Baker Laboratory Cornell University, Ithaca NY 14853-1301 (USA) Fax: (+1) 607-255-5707
Search for more papers by this authorRoald Hoffmann Prof.
Department of Chemistry Baker Laboratory Cornell University, Ithaca NY 14853-1301 (USA) Fax: (+1) 607-255-5707
Search for more papers by this authorDean J. Tantillo Dr.
Department of Chemistry Baker Laboratory Cornell University, Ithaca NY 14853-1301 (USA) Fax: (+1) 607-255-5707
Search for more papers by this authorRoald Hoffmann Prof.
Department of Chemistry Baker Laboratory Cornell University, Ithaca NY 14853-1301 (USA) Fax: (+1) 607-255-5707
Search for more papers by this authorWe gratefully acknowledge support from the National Science Foundation (through research grant CHE 99-70089) and the National Computational Science Alliance.
Graphical Abstract
Eine neue (wenngleich noch hypothetische) Verbindungsklasse wird beschrieben – die „Sigmatrop-Verschiebomere.“ Dabei handelt es sich um Polymere mit lokalen „Defekten“ in Form von Einfach- oder Doppelbindungen, die durch sigmatrope Umlagerungen im Polymergerüst fortschreiten (siehe Schema).
Supporting Information
Supporting information for this article (Coordinates and energies for computed structures from Scheme 2, as well as structures involved in the Cope rearrangements of 6 and 7.) is available on the WWW under http://www.angewandte.com or from the authors.
Please note: The publisher is not responsible for the content or functionality of any supporting information supplied by the authors. Any queries (other than missing content) should be directed to the corresponding author for the article.
References
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- 14 Barriers for Cope rearrangement of species with terminal acyclic hexadiene units were found to converge rapidly upon cyclobutane fusion to approximately 30 kcal mol−1 (from 42 kcal mol−1 in the parent boatlike cyclohexadiene,[10] Scheme 2). Also, [n]-ladderane oligomers were generally found to be <4 kcal mol−1 more stable than the broken [n]-ladderane isomers with central cyclooctadiene substructures derived from them (i.e. those species whose relative energies are set to 0.0 in Scheme 2).
- 15 We have not yet investigated substituent effects on this rearrangement; appropriately designed, they may lower the barrier even further.
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- 17
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- 18 Such systems include, for example, the asteranes[1a]—isomers of large prismanes with combinations of cis and trans fused cyclobutanes.
- 19 The size of these molecules has, so far, precluded computations on their putative fluxionality.
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