Modification of Fluorene and Fluorenone Core via C-H Functionalization

Abstract

We report the modification of fluorene and fluorenone cores, and assembling libraries of functionalized fluorenes/fluorenones involving the C(sp2)-H and C(sp3)-H functionalization route. Fluorene/fluorenone motifs are versatile components in materials science and some are bio-active compounds. In this work, the C-H bonds of fluorene and fluorenone were subjected to the C-H arylation, alkylation, benzylation, alkoxylation, and annulation reactions to afford modified fluorenes/fluorenones. Alternatively, various functionalized fluorenes/fluorenones were also obtained by subjecting the C-H bonds of aryl or alkyl carboxamides to the C-H arylation process using iodofluorenes or iodofluorenones as the coupling partners. Overall, a comprehensive effort and synthesis of several C(1), C(2), C(3), and C(4) functionalized fluorenes, fluorenones, fluorene-fluorenone couple, fluorene-carbazole couple, π-extended bis fluorenes, and enantioenriched π-extended bis fluorenes are reported. Given the prominence of fluorene/fluorenone motifs, this work contributes to augmenting the library of fluorenes and fluorenones via the C(sp2)-H and C(sp3)-H functionalization strategy.