Synthesis and structural data of tetrabenzo[8]circulene
Robert W Miller1, Alexandra K Duncan, Severin T Schneebeli
1Department of Chemistry, University of Vermont, Burlington, VT 05405 (USA), Fax: (+1) 802-656-8705.
Chemistry (Weinheim an Der Bergstrasse, Germany)
|March 12, 2014
Summary
Researchers developed a novel synthesis for tetrabenzo[8]circulene, a stable derivative of the challenging [8]circulene molecule. This breakthrough offers a new pathway for constructing complex polycyclic aromatic hydrocarbons.
Area of Science:
- Organic Chemistry
- Supramolecular Chemistry
- Materials Science
Background:
- The synthesis of [8]circulene, a saddle-shaped molecule, has been a long-standing challenge in organic chemistry since its first attempted synthesis in 1976.
- Despite decades of limited progress, recent advancements have seen two independent groups report novel strategies for synthesizing [8]circulene derivatives.
Purpose of the Study:
- To present a third, distinct synthetic method for constructing a derivative of [8]circulene.
- To synthesize and characterize tetrabenzo[8]circulene, a novel derivative with enhanced stability.
Main Methods:
- Employed a Diels-Alder reaction as a key step in the synthetic pathway.
- Utilized palladium-catalyzed arylation for crucial bond formation.
- Characterized the synthesized compound using various analytical techniques to confirm its structure and stability.
Main Results:
- Successfully synthesized tetrabenzo[8]circulene, a derivative of [8]circulene.
- The synthesized molecule exhibits remarkable stability under ambient and elevated temperatures, unlike the parent [8]circulene.
- Clar's theory of aromatic sextets accurately predicted the enhanced stability due to the incorporation of four fused benzenoid rings, leading to a fully benzenoid structure.
- Solid-state structural analysis revealed significant twisting compared to the calculated structure, attributed to crystal-packing forces, yet confirmed localized aromaticity.
Conclusions:
- The developed synthetic strategy provides a viable route to stable [8]circulene derivatives.
- Tetrabenzo[8]circulene represents a significant advancement in the synthesis of complex polycyclic aromatic hydrocarbons, demonstrating high stability.
- The study validates theoretical predictions regarding aromaticity and stability in large polycyclic systems.
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