Copper‐Catalyzed Synthesis of 5‐Arylindolo[1,2‐c]quinazolin‐6(5H)‐ones from 2‐(2‐Bromoaryl)indoles and Aryl Isocyanates under Microwave Irradiation

Abstract

2‐(2‐Bromoaryl)indoles react with aryl isocyanates by microwave irradiation in the presence of catalytic CuI along with a base to afford 5‐arylindolo[1,2‐c]quinazolin‐6(5H)‐ones. The reaction is compatible with 2‐(2‐bromoaryl)indoles bearing straight and branched alkyl chains at position 3 of indole moiety. Both electron‐donating and ‐withdrawing substituents on bromophenyl and indole moieties are well tolerated. The reaction proceeds through an initial nucleophilic addition of 2‐(2‐bromoaryl)indoles to aryl isocyanates. This is followed by an intramolecular C−N bond formation by an addition‐elimination nucleophilic aromatic substitution via Meisenheimer complexes and a copper‐catalyzed Ullmann‐type coupling.

Copper Catalyzed Synthesis of Heterocyclic Molecules via C–N and C–O Bond Formation under Microwaves: A Mini-Review

“…The synthetic manipulation was also possible with straight and branched alkyl chains at position 3 of the indole moiety in 2-(2-bromoaryl)­indoles. Similarly, both electron-withdrawing and electron-donating substituents on bromophenyl and indole moieties were resulted in good yield …”

“…Similarly, both electron-withdrawing and electron-donating substituents on bromophenyl and indole moieties were resulted in good yield. 21 Further in the same year, Sushmita and her group reported the synthesis of a novel series of N-substituted indole derivatives 66 using both conventional and microwave heating techniques. It was observed that microwave irradiation yielded a higher percentages of yields (72−96%) and shorter reaction times compared to the conventional approach (64−94%).…”

“…Similarly, both electron-withdrawing and electron-donating substituents on bromophenyl and indole moieties were resulted in good yield. 21 …”