Copper‐Catalyzed C−H Oxygenation of Benzoxepine‐4‐carboxylates: Facile Synthesis and Photophysical Properties of Naphtho[2,1‐d]oxazoles and Benzo[c]phenoxazines

Abstract

AbstractAn efficient, solvent‐free, one‐pot protocol was developed for the preparation of naphtho[2,1‐d]oxazoles and benzo[c]phenoxazines by the C−H oxygenation of benzoxepine‐4‐carboxylates with benzylamines and anilines in the presence of Cu(OAc)2. The synthesis, UV/vis absorption, fluorescence emission and electrochemical properties have been studied for these heterocyclic compounds. The benzo[c]phenoxazines absorbed in the UV/vis in the range 449–461 nm and fluorescence emission in the range 562–627 nm. The nitro‐ and dimethyl‐substituted benzo[c]phenoxazines had the most favorable fluorescence emission in these series of compounds (emission maxima at 627 and 603 nm with quantum yields Φf=0.51 and 0.37, respectively). The optical and electrochemical properties suggest that these compounds can act as electron‐transporting materials for organic light‐emitting diode applications.