On treatment with the catalyst InBr 3 , 1,1-difluoroallenes that bear a cyclopentene moiety and an aryl group underwent domino ring assembly in the presence or absence of N-bromosuccinimide or N-iodosuccinimide to afford aryne precursors such as three-ringed ortho-fluoro(halo)phenanthrenes, four-ringed ortho-fluoro(halo)tetraphenes, orthofluoro(halo)chrysenes and fluoro [4]helicenes. Metalation of the aryne precursors followed by elimination of the fluoride resulted in the unprecedented systematic generation of arynes bearing π-extended systems. DielsÀ Alder reactions of these arynes with isobenzofurans afforded the corresponding cycloadducts whose reductive aromatisation in an SnCl 2 /HBr system furnished fully aromatised benzotriphenylenes. In addition, oxidative arylÀ aryl coupling (the Scholl reaction) of these benzotriphenylenes facilitated the synthesis of 'half HBCs' (hexabenzocoronenes).[a] Dr.
Coronene and related polycyclic aromatic hydrocarbons (PAHs) have received significant interest over recent decades due to the development of liquid crystals and organic semiconducting materials. The ring assembly by a domino reaction of fluorinated allenes (1,2‐propadienes) has facilitated the synthesis of these π‐extended molecules. The domino reaction of 1,1‐difluoroallenes under indium catalysis afforded π‐extended aryne precursors. The Diels—Alder reactions of the arynes, followed by aromatization and aryl—aryl coupling successfully provided PAHs including ‘half HBCs’ (hexabenzocoronenes). More information can be found in the Full Paper by Junji Ichikawa et al. on page 1384 in Issue 8, 2020 (DOI: 10.1002/asia.202000069).
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