Twisted Polycyclic Aromatic Systems Prepared by Annulation of Bis(arylethynyl)arenes with Biphenylboronic Acids

Abstract

Twisted polycyclic aromatic hydrocarbons (PAHs) were prepared by the successive rhodium-catalyzed annulation and dehydrogenative cyclization of bis(arylethynyl)arenes with di-tert-butylbiphenyl-2-ylboronic acid. The molecular structures of the PAHs were determined by single-crystal XRD analysis. The PAHs showed up to four fjord regions, and the twisting angle was 46.7°. The nonplanarity (NP) and harmonic oscillator model of aromaticity (HOMA) were calculated by using the structural data obtained from XRD analysis. The PAHs derived from dialkynyl naphthalenes showed low planarity and HOMA of the central ring. The optical properties of the PAHs were investigated by UV/Vis absorption and fluorescence spectroscopy analyses. The absorption and emission maxima of the PAHs with a larger planar region appeared at a longer wavelength. DFT calculations support that the absorption band at λ≈450 nm can be mainly attributed to the HOMO-LUMO transition.

Synthetic Applications of Oxidative Aromatic Coupling—From Biphenols to Nanographenes

“…[139] As ar esult of the large steric hindrance,t he whole system is contorted and easily loses the two central tert-butyl substituents under acidic conditions. In addition to the structures shown in Figure 10, many other PA Hs have been synthesized using the oxidative coupling method [140][141][142][143][144][145][146][147] which, due to space limitations, cannot be included in this Review.…”

“…In addition to the structures shown in Figure , many other PAHs have been synthesized using the oxidative coupling method which, due to space limitations, cannot be included in this Review.…”

Recent Advances in Heterocyclic Nanographenes and Other Polycyclic Heteroaromatic Compounds

“…PAHs with a picene substructure, including the perylenoid 107.4 , were prepared via an oxidative coupling cyclization ( Scheme 107 ). 215 Sterically congested precursors 107.3 and 107.6 were prepared in a rhodium-catalyzed double annulation reaction from the corresponding dialkynes ( 107.2 and 107.5 ) and the biphenyl boronic acid 107.1 . The subsequent oxidation of 107.3 with FeCl 3 as an oxidant provided the quadruply cyclized, C 2 -symmetrical product 107.4 in 90% yield.…”

Syntheseanwendungen der oxidativen aromatischen Kupplung – von Biphenolen zu Nanographenen

“…Zusätzlich zu den in Abbildung dargestellten Strukturen wurden mithilfe der oxidativen Kupplungsmethode viele weitere PAKs synthetisiert, die aus Platzgründen nicht in diese Zusammenfassung einbezogen werden können.…”