A Practical General Method for the Preparation of Long Acenes. Issue 9 (16th January 2019)

• Record Type: Journal Article
• Authors: Jancarik, Andrej; Levet, Gaspard; Gourdon, André
• Is Part Of: Chemistry. Volume 25:Issue 9(2019)
• Page Start: 2366
• Page End: 2374
• Publication Date: 2019-01-16
• Subjects: acenes -- graphene -- heptacene -- hyperconjugation -- polycyles; Chemistry -- Periodicals; 540
• DOI: 10.1002/chem.201805975
• Languages: English
• ISSNs: 0947-6539

Abstract

Abstract: The field of long acenes, the narrowest of the zig‐zag graphene nanoribbons, has been an area of significant interest in the past decade because of its potential applications in organic electronics, spintronics and plasmonics. However the low solubility and high reactivity of these compounds has so far hindered their preparation on large scales. We report here a concise strategy for the synthesis of higher acenes through Diels–Alder condensation of arynes with a protected tetraene ketone. After deprotection by cleavage of the ketal, the obtained monoketone precursors cleanly yield the corresponding acenes through quantitative cheletropic thermal decarbonylation in the solid state, at moderate temperatures of 155 to 205 °C. This approach allows the preparation of heptacene, benzo[ a ]hexacene, cis ‐ and trans ‐dibenzopentacene and offers a valuable new method for the synthesis of even larger acenes. Abstract : On the straight and narrow : Symmetrical and nonsymmetrical chemically fragile and poorly soluble acenes beyond pentacene can be obtained from a protected bicyclic tetracene (see scheme). The method involves Diels–Alder addition with arynes, oxidation and cleavage of the ketal to give a soluble and stable polyaromatic ketone. Solid‐state cheletropic decarbonylation gives the target oligoacene in quantitative yield.