High-Yielding Synthesis and Full Spectroscopic Characterization of 5,6:11,12-Di-o-phenylenetetracene and Its Synthesis Intermediates

• Published in: European journal of organic chemistry 2016-01, Vol.2016 (3), p.569-578
• Main Authors: Wombacher, Tobias, Foro, Sabine, Schneider, Jörg J.
• Format: Article
• Language: English
• Subjects: Aromaticity; Fused-ring systems; Hydrocarbons; Polycyclic aromatic hydrocarbons; Reaction mechanisms
• ISSN: 1434-193X; 1099-0690
• DOI: 10.1002/ejoc.201501228

Herein we present a synthetic gram‐scale route to 5,6:11,12‐di‐o‐phenylenetetracene (DOPT, 8), which is a member of the class of cyclopenta‐fused polycyclic aromatic hydrocarbons (CP‐PAHs). Full analytical characterization of the title compound was carried out by IR, Raman, UV/Vis, and high‐field 1H NMR spectroscopy, as well as by mass spectrometry. A unique double‐elimination of phenylide moieties, as the key reaction step, gave DOPT for the first time in high purity and in an isolated yield of >70 %. Re‐aromatization of the annulated π‐ring system occurred following the reductive elimination of the two phenyl groups from the DOPT precursor. Two alternative reaction pathways for this process are discussed. The synthetic method described herein may allow development of the chemistry of the title compound further, for example, to investigate the organometallic chemistry of DOPT as well as its semiconducting behavior in organic electronics. Diels–Alder chemistry has allowed the high‐yielding synthesis of the carbon framework of the aromatic hydrocarbon 5,6:11,12‐di‐o‐phenylenetetracene (DOPT). All the reaction intermediates have been fully characterized for the first time. A final unprecedented re‐aromatization sequence employing a two‐fold reductive dephenylation yielded crystalline, blue DOPT in gram‐scale quantities.