An alternative approach to triazatruxene synthesis and derivatization to a boron difluoride complex†

The extensively studied organic material 5,10,15-triazatruxene is usually synthesized by the trimerization of indole or 2-indolone using the toxic liquid bromine and phosphoryl chloride. Herein, we report an efficient synthetic approach towards 5,10,15-triazatruxene by the condensation of 2-bromoaniline and phloroglucinol followed by palladium-catalyzed intramolecular C–H bond arylation. The regioselective iridium-catalyzed borylation occurred at the 1,6,11-positions of tert-butylated triazatruxene to generate a triboronic ester quantitatively. Pyridine groups were introduced via the Suzuki–Miyaura cross-coupling reaction to afford a precursor of a triazatruxene-based boron difluoride complex with a large Stokes shift.