Synthesis and Photophysical Properties of Azaarene-Substituted Hypocrellin B Derivatives

Azaarenes have been widely used in the field of organic synthesis due to their unique electronic structures, bonding characteristics, and functional performances. In this work, three azaarene-substituted hypocrellin B (HB) derivatives were prepared through C–N coupling at position 13 by a radical pathway. In the presence of triethylamine, the complex of HB and fluoroboron (HB-2BF) could form an anion radical, which easily reacts with azaarene at position 13. Acting as a precursor for the anion radical, HB-2BF could synthesize azaarene-substituted HB derivatives with excellent properties, such as the 2-pyridone-modified HB derivative (HBPD), which functions as a 1O2-responsive “off–on–off” photosensitizer for phototherapy.