Substituted indeno[2,1‐c]fluorene‐5,8‐diones as a platform for synthesis of polyaromatic hydrocarbons possessing extended π‐conjugated systems with butterfly‐like frameworks

Abstract

Synthetic options for conversion of indeno[2,1‐c]fluorene‐5,8‐diones into larger polyaromatic compounds with extended π‐conjugated systems were explored. The crucial two‐fold transformation of the five‐membered ketone moieties of indeno[2,1‐c]fluorene‐5,8‐diones was based either on a one‐carbon homologation or on a ring‐expansion reaction which eventually enabled syntheses of compounds possessing substituted tribenzo[a,e,l]indeno[1,2,3‐hi]acephenanthrylenes and [5]helicenes scaffolds. The former was prepared by using a reaction sequence based on Ramirez olefination, intramolecular Heck reaction, and intermolecular Suzuki‐Miyaura cross‐coupling, whereas the latter utilized a sequence comprising Büchner−Curtius−Schlotterbeck reaction and intermolecular Suzuki‐Miyaura cross‐coupling. Scholl reaction of selected [5]helicenes yielded planarized polyaromatic compounds with the tribenzo[a,e,l]indeno[1,2,3‐hi]acephenanthrylene scaffold. Where possible, structures of products were confirmed by X‐ray diffraction analyses. Photophysical properties were determined as well.