One-pot synthesis of 2-bromo-4,5-diazafluoren-9-one via a tandem oxidation–bromination-rearrangement of phenanthroline and its hammer-shaped donor–acceptor organic semiconductors

An unexpected one-pot tandem procedure of 2-bromo-4,5-diazafluoren-9-one starting from phenanthroline with a yield of up to 50% has been described. The conversion mechanism involves three consecutive oxidation, bromination, and rearrangement reactions. A series of its hammer-shaped donor–acceptor organic semiconductors with solvent-dependent fluorescence have also been constructed via Ullman and/or Friedel–Crafts reaction. Diazafluorenes (DAFs) and derivatives are regarded as promising building blocks or candidates for donor–acceptor organic semiconductors.