Tetrabenzanthanthrenes by mitigation of rearrangements in the planarization of ortho-phenylene hexamers

Abstract

In general, ortho-phenylene hexamers are not good substrates for oxidative planarization because of competing backbone rearrangements. However, by first planarizing the ends, a target tetrabenzanthanthrene has been obtained by oxidation in good yield. DFT calculations suggest that the larger polycyclic aromatic subunits of the preplanarized substrate increase the rate of planarization relative to that of rearrangement. By implication, it may be possible to prepare graphene structures that cannot be made directly from simple polyphenylenes by instead designing precursors with larger polycyclic aromatic moieties. The photophysical properties of the tetrabenzanthanthrene core indicate that it may have promise as a functional chromophore.

Synthetic Applications of Oxidative Aromatic Coupling—From Biphenols to Nanographenes

“…Another example of this trend has been presented by Hartley and co‐workers, who have shown that terphenyl 158 undergoes single oxidative coupling and a 1,2‐aryl shift to afford 160 and not hexacycle 159 (Scheme ) …”

“…[152] Another example of this trend has been presented by Hartley and co-workers,w ho have shown that terphenyl 158 undergoes single oxidative coupling and a1 ,2-aryl shift to afford 160 and not hexacycle 159 (Scheme 23). [153] Under oxidative coupling conditions (FeCl 3 or DDQ), acenes bearing aryl groups attached to the central benzene rings generally cyclize to form new five-membered rings. [142,144] Scheme 24 depicts an especially interesting example,w here oxidation of symmetric tetracene 161 led to the unsymmetric product 162 containing two new rings of different sizes:five-and six-membered.…”

Synthesis of partially and fully fused polyaromatics by annulative chlorophenylene dimerization

“…The clean, high-yielding formation of 3 without any optimization was quite surprising. It is well known that unwanted side reactions such as arene rearrangement (24) and aromatic chlorination often take place with polyaromatic compounds (23) in Scholl chemistry. For example, when polyphenylene 4, which can be prepared by the nickel-catalyzed reductive dimerization of 1a (25), was subjected to the standard Scholl conditions (FeCl 3 , CH 2 Cl 2 , 0°C), the fully fused product 3 was not obtained; instead, a complex mixture of various unidentified products (most likely arene rearrangement products) was obtained.…”

Syntheseanwendungen der oxidativen aromatischen Kupplung – von Biphenolen zu Nanographenen

“…Ein weiteres Beispiel für diesen Trend wurde von Hartley et al. vorgestellt, die gezeigt haben, dass das Terphenyl 158 eine einfache oxidative Kupplung und eine 1,2‐Arylverschiebung durchläuft, was zu 160 und nicht zum Hexacyclus 159 führt (Schema ) …”