Bidirectional Synthesis, Photophysical and Electrochemical Characterization of Polycyclic Quinones Using Benzocyclobutenes and Benzodicyclobutenes as Precursors

Quinones have widespread applications in view of their interesting chemical and photophysical features. On the other hand, benzocyclobutenes (BCBs) are generally masked reactive dienes suitable for the [4+2] cycloaddition reactions. Here, benzocyclobutenes and benzodicyclobutenes (BDCBs) were prepared and further reacted with benzoquinone and naphthoquinone in order to obtain some new polycyclic quinones with highly extended π systems, namely, 6‐bromo‐5,8‐dimethoxyanthracene‐1,4‐dione, 2,9‐dibromo‐1,4,8,11‐tetramethoxypentacene‐6,13‐dione, 9‐bromo‐7,10‐dimethoxytetracene‐5,12‐dione, 3,10‐dimethoxycyclobuta[b]anthracene‐1,5,8(2H)‐trione, 6,10,17,21‐tetramethoxynonacene‐1,4,8,12,15,19‐hexaone, and 3,12‐dimethoxycyclobuta[b]tetracene‐1,5,10(2H)‐trione. In addition to their spectroscopic characterization the new compounds are investigated by UV and fluorescence spectroscopy, cyclic voltammetry, and DFT calculations. The synthesis of some new extended polycyclic quinones was achieved through a one‐pot procedure comprising the cycloaddition of benzocyclobutene and benzodicyclobutene derivatives with benzoquinone or naphthoquinone. Notably, a highly symmetrical nonacene‐hexaone could be prepared, albeit in low yields (5–7 %).