Magnetic MOF‐199‐Catalyzed Synthesis of Benzo[4,5]imidazo[1,2‐f]phenanthridines and Their Analogues by Tandem C(sp²)−C Coupling and Cyclization Followed by Aromatization

Abstract

Treatment of 2‐(2‐bromoaryl)‐ and 2‐(2‐bromovinyl)benzimidazoles with cyclohexane‐1,3‐diones in DMF in the presence of reusable Fe3O4@SiO2@MOF‐199 along with L‐proline and Cs2CO3 afforded 2,3‐dihydrobenzo[4,5]imidazo[1,2‐f]phenanthridin‐4(1H)‐ones and 2,3‐dihydrobenzo[4,5]imidazo[1,2‐a]quinolin‐4(1H)‐ones, respectively, in moderate to good yields. Such C(sp2)−C coupled and cyclized scaffolds were aromatized to benzo[4,5]imidazo[1,2‐f]phenanthridines and benzo[4,5]imidazo[1,2‐a]quinolines in good yields by a one‐pot sequential treatment with NaBH4, POCl3/pyridine, and DDQ.