Modification of fluorene and fluorenone core via C-H functionalization.

Abstract

We report the modification of fluorene and fluorenone cores, and the assembly of 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 bioactive compounds. In this work, the C-H bonds of fluorene and fluorenone were subjected to C-H arylation, alkylation, benzylation, alkoxylation, and annulation reactions to afford modified fluorenes/fluorenones. Alternatively, various functionalized fluorenes/fluorenones were 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 couples, fluorene-carbazole couples, 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 a C(sp²)-H and C(sp³)-H functionalization strategy.