Synthesis of benzo[4,5]imidazo[1,2‐a]indolo[1,2‐c]quinazolines from 2‐(2‐bromoaryl)indoles and 2‐methoxybenzimidazoles under recyclable magnetic MOF‐199 catalysis

Abstract

2‐(2‐Bromoaryl)indoles react with 2‐methoxybenzimidazoles in DMF in the presence of a catalytic amount of recyclable Fe3O4@SiO2@MOF‐199 along with K2CO3 to afford a series of benzo[4,5]imidazo[1,2‐a]indolo[1,2‐c]quinazolines in good yields. The reaction applies to a broad scope of 2‐(2‐bromoaryl)indoles containing electron‐donating or ‐withdrawing substituents on bromophenyl and indole moieties, and alkyl substituents at 3‐position of indole moiety. A reaction pathway involving a copper‐catalyzed Ullmann‐type C (sp2)‐N coupling and an addition‐elimination nucleophilic aromatic substitution via Meisenheimer complex followed by cyclocondensation is proposed for this catalytic process. The Fe3O4@SiO2@MOF‐199 catalyst could be recovered and reused several times without any change of catalytic activity.

Recent Approaches for the Synthesis of Imidazoquinazolines and Benzimidazoquinazolines

“…One-pot regioselective synthesis of benz [4,5]imidazo[1,2-a]quinazoline was reported by Fang, S. et al Anilinobenzimidazole (25) showed a reaction with various aromatic aldehydes bearing halogen groups and a nitro group (57a-o) in DMF to afford the targeted products (58a-j) in 59-97% yields [73]. Transition metal-free coupling reaction to form benzimidazoquinazoline was carried out by Kim et al under recyclable magnetic MOF-199 catalysis [74].…”